From d7d036578766c17377da80a3893290eebe947d13 Mon Sep 17 00:00:00 2001
From: han4wluc <han4wluc@yuusoft.com>
Date: Fri, 27 Mar 2026 12:51:47 +0800
Subject: [PATCH 1/5] Implement rollback timeline model

---
 docs/Rollback.md                              | 383 ++++++++++
 docs/RollbackImplementationPlan.md            | 703 ++++++++++++++++++
 spec/system/actions/loadSaveSlot.spec.yaml    | 122 +++
 spec/system/actions/nextLine.spec.yaml        | 147 ++++
 .../actions/nextLineFromSystem.spec.yaml      |  48 ++
 .../system/actions/rollbackByOffset.spec.yaml | 136 ++++
 spec/system/actions/saveSaveSlot.spec.yaml    | 117 +++
 .../actions/sectionTransition.spec.yaml       |  14 +-
 spec/system/createInitialState.spec.yaml      |  52 +-
 src/stores/system.store.js                    | 283 ++++++-
 10 files changed, 1993 insertions(+), 12 deletions(-)
 create mode 100644 docs/Rollback.md
 create mode 100644 docs/RollbackImplementationPlan.md

diff --git a/docs/Rollback.md b/docs/Rollback.md
new file mode 100644
index 00000000..b934e844
--- /dev/null
+++ b/docs/Rollback.md
@@ -0,0 +1,383 @@
+# Rollback Design
+
+This document defines the intended product behavior and engine model for rollback in `route-engine`.
+
+It is a design document, not a guarantee that the current implementation already matches every rule below.
+
+## Purpose
+
+Rollback is a core reading control in a visual novel.
+
+Its job is to let the player move backward through prior line checkpoints and restore the corresponding story state so the game can be re-read or re-branch from that point.
+
+Rollback is not the same as dialogue history.
+
+- `Back` means rollback.
+- `History` is a separate read-only feature and is out of scope for this document.
+
+## Product Summary
+
+The rollback model for `route-engine` is:
+
+- `Back` performs true rollback.
+- Rollback is line-level.
+- Rollback crosses section boundaries.
+- Rollback policy is `free` for now.
+- The model should be extensible to support additional policies later.
+- Presentation is always reconstructed from story state after rollback.
+- Seen-line tracking does not roll back.
+- Persistent/global device/account variables do not roll back.
+- Rollback stops auto mode and skip mode.
+- If the user rolls back and then advances again, future rollback history after that point is discarded and replaced by the new branch.
+- Rollback timeline is stored in save data and restored on load.
+
+## Terminology
+
+### Rollback
+
+Rollback means restoring a prior story checkpoint and making that checkpoint the current playable position.
+
+Rollback changes story state.
+
+### History
+
+History means showing previously displayed dialogue in a read-only UI.
+
+History does not change story state.
+
+History is a separate feature and should not be conflated with rollback.
+
+### Checkpoint
+
+A checkpoint is the unit the player can roll back to.
+
+In this design, checkpoints are line-level.
+
+Checkpoint state is defined as:
+
+- the state after rollbackable story actions for that line have been applied
+
+That means rollback reconstruction to a target checkpoint replays rollbackable story actions up to that target line inclusively.
+
+For v1, the authoritative replay source for a checkpoint is:
+
+- the project-data line identified by that checkpoint's `sectionId` and `lineId`
+- filtered to rollbackable story mutations only
+
+The checkpoint entry itself does not need to duplicate the mutation payload as long as replay remains deterministic for the supported rollbackable action set.
+
+## Back Button Semantics
+
+The main `Back` action in reading UI should perform rollback, not history preview.
+
+Expected behavior:
+
+- If the player presses `Back`, the engine rolls back to the previous line checkpoint.
+- This should work even if the current line is incomplete.
+- `Back` should not first "complete the current line" and require a second press.
+
+Rationale:
+
+- Advance and rollback should have different semantics.
+- Advancing is incremental and often reveal-aware.
+- Rollback is an explicit undo/navigation action and should be decisive.
+
+## Rollback Policy
+
+Current product policy is:
+
+- `free`
+
+Meaning:
+
+- The player may roll back to an earlier checkpoint.
+- The player may then advance again and make different decisions.
+- The old future branch is discarded once the player diverges.
+
+Future policies should be possible without redesigning the entire model:
+
+- `fixed`
+  - player may roll back and inspect prior state
+  - prior decisions remain locked
+- `blocked`
+  - player may not roll back before a specific checkpoint
+
+These policies are not part of the current behavior, but the internal checkpoint structure should leave room for them.
+
+## Checkpoint Granularity
+
+Checkpoints are line-level.
+
+That means:
+
+- every line that the player reaches becomes a rollback checkpoint
+- rollback moves between lines, not between arbitrary internal action steps
+
+This is intentionally simple and predictable.
+
+For now, we do not introduce finer-grained checkpoint kinds.
+
+The checkpoint structure should remain extensible so future metadata can be attached if needed.
+
+## Cross-Section Rollback
+
+Rollback must cross section boundaries.
+
+If the player reached:
+
+- section A, line 10
+- then section B, line 1
+
+pressing `Back` should allow rollback from section B back into section A.
+
+Rationale:
+
+- from the player's perspective, this is one continuous reading timeline
+- restricting rollback to the current section feels arbitrary and broken
+
+This means rollback history must be modeled as a single ordered timeline per context, not only as isolated per-section history buckets.
+
+## Rollback Scope
+
+### State that rolls back
+
+Rollback restores:
+
+- current read pointer
+- current section and line
+- context-scoped story variables
+- current branch position in the narrative
+
+### State that does not roll back
+
+Rollback does not restore:
+
+- seen-line registry
+- seen-resource registry
+- persistent/global device variables
+- persistent/global account variables
+- save slots
+- external side effects outside engine state
+
+Rationale:
+
+- seen-state should be monotonic
+- persistent/global variables are not story-local and should not behave like local branch state
+
+Consequence:
+
+- after rollback, previously seen content remains seen even if the player later diverges onto a different branch
+- skip behavior may still treat previously seen branch content as seen
+
+This is intentional for v1.
+
+## Presentation Model
+
+Rollback must not restore stored presentation snapshots.
+
+Instead:
+
+- rollback restores rollbackable story state
+- presentation is derived from that state
+- render state is derived from presentation and system state
+
+This matches the core state-driven architecture of `route-engine`.
+
+Implications:
+
+- transient animation progress is not restored
+- presentation after rollback is reconstructed, not resumed
+- rollback correctness should be defined in terms of restored story state, not exact renderer internals
+
+## Divergence Rule
+
+If the player rolls back and then advances again from the rollback point:
+
+- all future checkpoints after that point are discarded
+- a new future branch is created from the rollback point
+
+This is standard rollback behavior and keeps the model coherent.
+
+Without this rule, rollback history becomes ambiguous and harder to reason about.
+
+## Interaction with Auto and Skip
+
+Rollback should always stop:
+
+- auto mode
+- skip mode
+
+Rationale:
+
+- rollback is an explicit navigation action
+- continuing auto/skip after rollback is surprising and unsafe
+
+## Data Model Direction
+
+The data model should support the product rules above.
+
+### Required logical model
+
+Each context should have a single rollback timeline ordered by playthrough sequence.
+
+Conceptually:
+
+```js
+rollback: {
+  currentIndex: 0,
+  isRestoring: false,
+  timeline: [
+    {
+      sectionId: "section1",
+      lineId: "line1",
+      rollbackPolicy: "free",
+    },
+  ],
+}
+```
+
+The exact field names may differ, but the model should support:
+
+- ordered line checkpoints across section boundaries
+- replaying rollbackable story actions from timeline history
+- an array-index cursor for the current rollback position
+- a temporary restore guard for rollback reconstruction
+- future rollback policy expansion
+
+### Current checkpoint contents
+
+For now, checkpoint identity only needs:
+
+- `sectionId`
+- `lineId`
+
+But the structure should be able to grow later with:
+
+- `rollbackPolicy`
+- future interaction metadata
+- future choice locking metadata
+
+## Restoration Strategy
+
+Rollbackable story state should be recomputed from full rollback history, not restored from per-checkpoint variable snapshots.
+
+The model is:
+
+- rollback timeline stores the visited line sequence
+- each entry identifies a visited line by `sectionId` and `lineId`
+- rollback restoration resets context-scoped story state to the context baseline
+- the engine replays rollbackable story actions from the start of the timeline up to the target timeline index
+- presentation is then reconstructed from the resulting story state
+
+This means:
+
+- presentation snapshots are never stored
+- context variable snapshots are not the source of truth
+- story state is derived from the rollback timeline
+
+For now, replayability is based on line sequence plus rollbackable action classification.
+
+Initially, the only required rollbackable story mutation type is:
+
+- `updateVariable`
+
+This can be expanded later if more rollbackable action types are introduced.
+
+## Restore Guard
+
+Rollback restoration requires an explicit temporary guard such as:
+
+```js
+rollback.isRestoring = true;
+```
+
+This is an internal implementation flag, not a user-facing mode.
+
+Its purpose is to prevent the restore process from being mistaken for normal forward progression.
+
+During restore:
+
+- new rollback checkpoints must not be appended
+- rollbackable story actions must not execute again as live gameplay actions
+- seen-state must not be recomputed as fresh progression
+- normal progression side effects must not be emitted
+
+Restore must use a dedicated rollback restore path.
+
+It must not reuse normal live line-action execution as if the player had just progressed forward.
+
+For v1, `jumpToLine` is excluded from rollback history.
+
+Rationale:
+
+- `jumpToLine` can be used for tooling, debugging, or non-player transport
+- automatically recording it as player rollback history would pollute the rollback timeline
+
+Without this guard, rollback reconstruction can:
+
+- execute `updateVariable` more than once
+- append duplicate timeline entries
+- produce incorrect derived state
+
+## Non-Goals
+
+This document does not define:
+
+- dialogue history UI
+- history retention rules
+- fixed rollback behavior
+- blocked rollback behavior
+- roll-forward UX
+- save/load UI behavior beyond normal state restoration
+
+## Save/Load
+
+Rollback timeline is part of saved runtime state.
+
+That means:
+
+- saves must serialize the rollback timeline
+- saves must serialize the current rollback cursor
+- loading a save must restore rollback ability from that saved point
+
+Compatibility behavior for older saves without rollback timeline should be defined during implementation.
+
+Recommended default:
+
+- if an older save does not contain rollback state, initialize a minimal rollback timeline at the loaded current pointer
+- do not attempt to reconstruct older rollback history that was never saved
+
+Those can be defined separately later.
+
+## Implementation Notes
+
+The current engine already derives presentation from state, which is correct.
+
+However, a fully correct rollback system for this product model should move toward:
+
+- a per-context rollback timeline
+- line-level checkpoints
+- direct restoration of rollbackable story state
+- future policy extensibility
+
+The current code may still contain older concepts such as:
+
+- history-mode pointers
+- section-oriented history structures
+- replay-based rollback logic
+
+Those should be treated as implementation details that can be replaced if they do not fit this design.
+
+## Review Checklist
+
+The design is correct if all of the following are true:
+
+- `Back` always means rollback
+- rollback works on incomplete lines
+- rollback crosses section boundaries
+- rollback reconstructs presentation from story state
+- rollback does not affect seen-state
+- rollback does not affect persistent/global device/account variables
+- rollback stops auto/skip
+- re-advancing after rollback discards the old future branch
+- the internal checkpoint model can later support `fixed` and `blocked` policies
diff --git a/docs/RollbackImplementationPlan.md b/docs/RollbackImplementationPlan.md
new file mode 100644
index 00000000..f04e984c
--- /dev/null
+++ b/docs/RollbackImplementationPlan.md
@@ -0,0 +1,703 @@
+# Rollback Implementation Plan
+
+This document translates [Rollback.md](/home/han4wluc/repositories/RouteVN/route-engine/docs/Rollback.md) into an implementation plan for `route-engine`.
+
+It is intentionally technical.
+
+## Goal
+
+Replace the current mixed "history mode + section replay" rollback behavior with a true rollback system that:
+
+- uses line-level checkpoints
+- supports cross-section rollback
+- recomputes rollbackable story state from full rollback history
+- reconstructs presentation after restoration
+- remains extensible for future rollback policies
+
+## Scope
+
+In scope:
+
+- rollback model and engine actions
+- checkpoint storage
+- pointer restoration
+- branch truncation after rollback
+- stopping auto/skip on rollback
+- tests and docs
+
+Out of scope:
+
+- dialogue history UI
+- fixed rollback
+- blocked rollback
+- roll-forward
+- save UI changes
+
+## Current State
+
+The current engine has two different backward-navigation concepts:
+
+1. `prevLine`
+- moves a `history` pointer
+- behaves like preview/history navigation
+- does not represent the intended final `Back` semantics
+
+2. `rollbackToLine` / `rollbackByOffset`
+- resets context variables to a section `initialState`
+- replays recorded `updateVariable` actions
+- is limited by the current section-oriented history structure
+
+The implementation currently depends on:
+
+- `contexts[*].historySequence`
+- `pointers.read`
+- `pointers.history`
+- `currentPointerMode`
+- event-sourced replay of context variable mutations inside a section
+
+This is not the right long-term model for:
+
+- cross-section rollback
+- line-level checkpoints across the full playthrough
+- future rollback policy expansion
+
+## Target Model
+
+Each context should own one ordered rollback timeline.
+
+Conceptually:
+
+```js
+contexts: [
+  {
+    pointers: {
+      read: { sectionId, lineId },
+    },
+    rollback: {
+      currentIndex: 12,
+      isRestoring: false,
+      timeline: [
+        {
+          sectionId: "intro",
+          lineId: "line1",
+          rollbackPolicy: "free",
+        },
+      ],
+    },
+  },
+];
+```
+
+### Required properties
+
+Each checkpoint should eventually be able to hold:
+
+- `sectionId`
+- `lineId`
+- `rollbackPolicy`
+
+For initial implementation:
+
+- the array index is the sequence identity
+- `rollbackPolicy` can default to `"free"`
+
+No separate `sequenceId` is required as long as:
+
+- timeline order is preserved
+- `currentIndex` is the rollback cursor
+
+## High-Level Approach
+
+Use the visited-line timeline as the source of truth for rollbackable story state.
+
+Specifically:
+
+- store visited lines in playthrough order
+- do not snapshot presentation
+- do not treat variable snapshots as the source of truth
+- on rollback:
+  - reset context variables to the context baseline
+  - replay rollbackable story actions from the start of the timeline up to the target index
+  - move `read` pointer to the target checkpoint
+  - reconstruct presentation/render state from restored story state
+
+For now, the only required rollbackable story mutation type is:
+
+- `updateVariable`
+
+Implementation default for v1:
+
+- replay source is the project-data line actions for each visited checkpoint
+- replay only the rollbackable subset of those actions
+- do not duplicate mutation payloads into checkpoint entries yet
+
+Checkpoint semantics must be defined as:
+
+- checkpoint N represents state after rollbackable story actions for line N have been applied
+
+So rollback replay to target index is inclusive.
+
+This can be expanded later if more rollbackable action types are introduced.
+
+## Restore Guard
+
+Rollback restoration requires an explicit temporary guard:
+
+```js
+rollback.isRestoring = true;
+```
+
+This is an internal implementation flag, not a user-facing mode.
+
+Its purpose is to prevent the restore process from being mistaken for normal forward progression.
+
+During restore:
+
+- do not append new rollback checkpoints
+- do not execute normal live mutation side effects
+- do not double-apply `updateVariable`
+- do not perform fresh progression bookkeeping
+
+Without this guard, rollback reconstruction can:
+
+- execute story mutations more than once
+- append duplicate timeline entries
+- corrupt recomputed state
+
+Implementation rule:
+
+- rollback restore must use a dedicated restore path
+- it must not rely on normal live line-action execution
+
+## Data Structure Migration
+
+### Phase 1: Introduce rollback timeline alongside current structures
+
+Add a new context-local structure:
+
+```js
+rollback: {
+  currentIndex: 0,
+  isRestoring: false,
+  timeline: [],
+}
+```
+
+Checkpoint shape:
+
+```js
+{
+  sectionId,
+  lineId,
+  rollbackPolicy: "free",
+}
+```
+
+Implementation notes:
+
+- checkpoint creation should happen through one internal helper, not inline in many actions
+- `rollbackPolicy` should be present or defaultable from one helper
+- `currentIndex` should be the array-index cursor into `timeline`
+
+Current pointer rule:
+
+- `rollback.currentIndex` is the single source of truth for rollback position inside the timeline
+- array order is the sequence identity
+
+### Phase 2: Keep old history structures temporarily
+
+Do not remove these immediately:
+
+- `historySequence`
+- `pointers.history`
+- `currentPointerMode`
+- `prevLine`
+
+Reason:
+
+- they may still be needed by existing tests or non-rollback flows
+- history/log is a separate feature and may still temporarily depend on some of them
+
+But rollback actions should stop depending on them as the new timeline becomes authoritative.
+
+Recommended deprecation stance:
+
+- `prevLine` and history pointers may remain temporarily for non-rollback features
+- they should no longer be considered part of gameplay back semantics
+
+### Phase 3: Decommission old rollback dependencies
+
+Once rollback actions and tests are migrated:
+
+- remove rollback dependence on `historySequence`
+- remove rollback dependence on `pointers.history`
+- stop using section-oriented replay for rollback
+
+Possible later cleanup:
+
+- fully remove `currentPointerMode === "history"` if it is no longer used by any feature
+
+That decision should be made separately from rollback.
+
+## Checkpoint Creation Rules
+
+Checkpoints are line-level.
+
+A checkpoint should exist for each line the player reaches in read flow.
+
+### Required checkpoint creation points
+
+1. Engine init
+- create initial checkpoint for the initial line
+
+2. `nextLine`
+- after advancing to the new line
+
+3. `nextLineFromSystem`
+- after advancing to the new line
+
+4. `sectionTransition`
+- after landing on the destination section's first line
+
+5. `jumpToLine`
+- excluded from rollback timeline for now
+
+Rationale:
+
+- `jumpToLine` can be used for tooling, debugging, or non-player transport
+- automatically recording it as player rollback history would pollute the timeline
+
+### Rule for timing
+
+Checkpoint should represent the line the player is now on, not the line they left.
+
+That keeps rollback semantics intuitive:
+
+- back from line 10 goes to line 9
+- current line is always represented in the timeline
+
+### Deduplication rule
+
+Do not create duplicate adjacent checkpoints for the same:
+
+- `sectionId`
+- `lineId`
+
+unless future policy metadata requires it.
+
+Use one helper like:
+
+```js
+appendRollbackCheckpoint(state, {
+  sectionId,
+  lineId,
+  rollbackPolicy: "free",
+});
+```
+
+The helper should also:
+
+- truncate future timeline if `currentIndex` is not already at the end
+- append the new checkpoint
+- move `currentIndex` to the new last index
+
+## Replay Rules
+
+Rollback reconstruction should replay only rollbackable story actions.
+
+It must not replay arbitrary line actions as if they were live gameplay.
+
+### Initial rollbackable action set
+
+Start with:
+
+- `updateVariable`
+
+Future rule:
+
+- any new story-mutating action must explicitly declare whether it is rollbackable before it participates in rollback replay
+
+### Non-replayed actions during restore
+
+Do not replay as story mutations during restore:
+
+- dialogue presentation actions
+- background/character/visual/layout presentation actions
+- seen-state updates
+- persistent/global variable writes
+- save-related effects
+- any other forward-progression bookkeeping
+
+This is why rollback restore must not call the normal live line-action path.
+
+Presentation should still appear correctly because it is derived from the restored story state and current pointer.
+
+## Rollback Action Design
+
+### Replace `prevLine` as gameplay back
+
+`Back` in gameplay should no longer use `prevLine`.
+
+Instead:
+
+- UI-facing back action should call `rollbackByOffset({ offset: -1 })`
+
+`prevLine` may remain temporarily for history/log work, but it should not be the primary gameplay back implementation.
+
+### `rollbackByOffset`
+
+Target behavior:
+
+1. validate offset is negative
+2. find target checkpoint from `rollback.currentIndex + offset`
+3. if out of bounds, no-op
+4. delegate to one internal restore helper
+
+### `restoreRollbackCheckpoint`
+
+Introduce an internal restore helper:
+
+```js
+restoreRollbackCheckpoint(state, checkpointIndex)
+```
+
+Responsibilities:
+
+1. stop auto mode
+2. stop skip mode
+3. set `rollback.isRestoring = true`
+4. set `rollback.currentIndex`
+5. reset context variables to the context baseline
+6. replay rollbackable actions from `timeline[0..checkpointIndex]`
+7. restore `pointers.read`
+8. set `rollback.isRestoring = false`
+9. clear any stale timers via pending effects
+10. set line completion state appropriately
+11. queue normal render path
+
+The target line must be rendered from reconstructed state, not by replaying normal live gameplay actions.
+
+### Line completion on rollback
+
+Policy from product spec:
+
+- rollback should go immediately to previous checkpoint
+- no "complete current line first" behavior
+
+Recommended engine state after rollback:
+
+- `isLineCompleted = true`
+
+Reason:
+
+- the rolled-back line should be visible immediately
+- the engine should not require reveal completion before another rollback
+- presentation is reconstructed, not resumed
+
+If later you want rolled-back lines to reveal again, that should be an explicit separate product decision.
+
+## Branch Truncation
+
+When the user rolls back and then advances again:
+
+- all checkpoints after `rollback.currentIndex` must be discarded before appending the new forward checkpoint
+
+This should happen in the checkpoint append helper.
+
+Pseudo-logic:
+
+```js
+if (rollback.currentIndex < rollback.timeline.length - 1) {
+  rollback.timeline = rollback.timeline.slice(0, rollback.currentIndex + 1);
+}
+```
+
+Then append the new checkpoint and move `currentIndex` to the end.
+
+This is required for coherent free rollback.
+
+This also means:
+
+- after divergence, old future checkpoints are permanently discarded from the active rollback timeline
+
+## Variable Scope Rules
+
+Rollback restores:
+
+- context-scoped variables only, derived by replay from the timeline
+
+Rollback does not restore:
+
+- global-device variables
+- global-account variables
+- seen registries
+
+Implementation rule:
+
+- rollback replay should only affect context-scoped rollbackable story actions
+- do not mix global persistent variables into rollback reconstruction
+
+Cross-branch consequence:
+
+- previously seen content remains seen even after divergence
+- this is intentional and should not be treated as a rollback bug
+
+## Presentation and Rendering Flow
+
+Rollback must keep the existing architectural principle:
+
+- system state changes first
+- presentation is derived
+- render state is derived
+- route-graphics renders the result
+
+So rollback should not attempt to store or restore:
+
+- presentation state
+- render state
+- animation progress
+
+Instead:
+
+1. reset story state to the context baseline
+2. replay rollbackable timeline entries up to target index
+3. restore pointer to target line
+4. queue normal render effects
+5. let the engine derive presentation/render state fresh
+
+Do not restore by executing arbitrary line actions as if the user had just progressed normally.
+
+Restore should use:
+
+- timeline replay for rollbackable story actions
+- normal state-to-presentation derivation for rendering
+
+## Action Changes
+
+### `nextLine`
+
+Update to:
+
+- advance pointer
+- reset line completion state as usual
+- append checkpoint for destination line
+
+### `nextLineFromSystem`
+
+Update to:
+
+- advance pointer
+- append checkpoint for destination line
+
+### `sectionTransition`
+
+Update to:
+
+- move pointer to target section first line
+- append checkpoint for destination line
+
+### `jumpToLine`
+
+Do not append rollback checkpoints for `jumpToLine` in the initial implementation.
+
+Treat it as out of the player rollback flow unless it is later reclassified as true gameplay navigation.
+
+### `rollbackByOffset`
+
+Rewrite to operate on the rollback timeline, not `historySequence`.
+
+### `rollbackToLine`
+
+Either:
+
+- rewrite it as a lookup into the new timeline by line identity plus occurrence
+
+or:
+
+- deprecate it in favor of checkpoint-index-based restore helpers
+
+Recommendation:
+
+- keep public API if needed
+- internally resolve to checkpoint index in the rollback timeline
+
+## Save/Load
+
+Rollback timeline should be saved and loaded as part of context state.
+
+That is necessary for:
+
+- consistent rollback after load
+- preserving branch position correctly
+
+Implementation requirement:
+
+- the new `rollback` context structure must be serializable
+- it must not contain renderer objects or non-serializable references
+- loading a save must restore both:
+  - `rollback.timeline`
+  - `rollback.currentIndex`
+
+Compatibility requirement:
+
+- define explicit behavior for older saves that do not contain rollback state
+
+Recommended default:
+
+- initialize a minimal rollback timeline anchored at the loaded current pointer
+- do not attempt to synthesize unsaved historical checkpoints
+
+## Future Policy Expansion
+
+Even though only `free` is implemented now, add a small abstraction boundary.
+
+Recommended helper:
+
+```js
+const resolveRollbackPolicy = (checkpoint) =>
+  checkpoint.rollbackPolicy ?? "free";
+```
+
+Later:
+
+- `free`
+- `fixed`
+- `blocked`
+
+can be handled in one place without redesigning checkpoint storage.
+
+## Test Plan
+
+### Unit/system tests
+
+Add or migrate tests for:
+
+1. initial checkpoint exists at engine start
+2. manual line advance appends checkpoint
+3. auto/skip/system advance appends checkpoint
+4. section transition appends checkpoint
+5. rollback by offset moves to previous line in same section
+6. rollback by offset crosses section boundary
+7. rollback recomputes context variables from timeline replay
+8. rollback does not restore persistent globals
+9. rollback does not restore seen registry
+10. rollback stops auto mode
+11. rollback stops skip mode
+12. rollback on incomplete line goes immediately to previous checkpoint
+13. re-advance after rollback truncates old future branch
+14. duplicate adjacent checkpoints are not appended
+15. `rollback.isRestoring` prevents duplicate checkpoint append
+16. `rollback.isRestoring` prevents duplicate `updateVariable` execution
+17. old-save compatibility initializes a minimal rollback timeline correctly
+
+### Regression tests for divergence
+
+This is important enough to test directly:
+
+1. reach A -> B -> C
+2. rollback to B
+3. make a different choice / branch to D
+4. assert old C checkpoint is gone
+5. assert timeline is A -> B -> D
+
+### Serialization tests
+
+Add tests that:
+
+1. save a state with rollback timeline
+2. load it
+3. rollback still works correctly afterward
+
+## Migration Sequence
+
+Recommended order:
+
+1. add rollback timeline structure to context state
+2. add `appendRollbackCheckpoint` helper
+3. create checkpoints on init and forward navigation
+4. add branch truncation logic
+5. add `rollback.isRestoring` guard and restore helper
+6. implement replay-based rollback reconstruction from timeline start
+7. switch `rollbackByOffset` to new timeline
+8. switch UI-facing back flows to true rollback
+9. stop rollback logic from depending on `historySequence`
+10. update docs and tests
+11. evaluate whether `prevLine` / `history` pointer can be simplified or removed later
+
+## Risks
+
+### 1. Double checkpoint creation
+
+If both navigation action and line handling append checkpoints, timeline will drift.
+
+Mitigation:
+
+- centralize checkpoint appending in one helper
+- write adjacency dedupe tests
+
+### 2. Hidden dependence on `historySequence`
+
+Some current selectors/tests may still depend on old structures.
+
+Mitigation:
+
+- migrate rollback tests first
+- keep old structures temporarily for unrelated features
+
+### 3. Save compatibility
+
+Changing context shape may affect older saves.
+
+Mitigation:
+
+- decide whether to support a compatibility shim
+- if not, document the save compatibility break clearly
+
+### 4. Branch truncation bugs
+
+If future checkpoints are not trimmed correctly, rollback semantics become incoherent.
+
+Mitigation:
+
+- add explicit branch-divergence tests
+
+### 5. Incorrect replay classification
+
+If non-rollbackable actions are replayed as story mutations, restore will corrupt state.
+
+Mitigation:
+
+- explicitly classify rollbackable actions
+- start with `updateVariable` only
+- add restore-guard regression tests
+
+### 6. Unbounded timeline growth
+
+Rollback history is intentionally unbounded for now.
+
+Mitigation:
+
+- accept this as a product tradeoff in v1
+- keep checkpoint entries minimal
+- defer compaction/pruning work until there is evidence it is needed
+
+## Recommended First Implementation Slice
+
+The smallest valuable vertical slice is:
+
+1. add rollback timeline with array-index cursor
+2. append checkpoints on init, `nextLine`, `nextLineFromSystem`, and `sectionTransition`
+3. add `rollback.isRestoring`
+4. implement replay-based `rollbackByOffset(-1)` on the new timeline
+5. stop auto/skip on rollback
+6. support cross-section rollback
+7. add system tests for same-section and cross-section rollback
+
+Do not start with:
+
+- fixed rollback
+- blocked rollback
+- history UI
+- roll-forward
+
+Those should come later.
diff --git a/spec/system/actions/loadSaveSlot.spec.yaml b/spec/system/actions/loadSaveSlot.spec.yaml
index 86ce6237..e65e4e54 100644
--- a/spec/system/actions/loadSaveSlot.spec.yaml
+++ b/spec/system/actions/loadSaveSlot.spec.yaml
@@ -41,6 +41,15 @@ out:
   contexts:
     - pointers:
         read: { sectionId: "sec2", lineId: "line2" }
+      rollback:
+        currentIndex: 0
+        isRestoring: false
+        replayStartIndex: 1
+        baselineVariables: {}
+        timeline:
+          - sectionId: "sec2"
+            lineId: "line2"
+            rollbackPolicy: "free"
 ---
 case: load from non-existent slot
 in:
@@ -172,3 +181,116 @@ out:
         playerName: "Alice"
         score: 150
         soundEnabled: true
+      rollback:
+        currentIndex: 0
+        isRestoring: false
+        replayStartIndex: 1
+        baselineVariables:
+          playerName: "Alice"
+          score: 150
+          soundEnabled: true
+        timeline:
+          - sectionId: "sec2"
+            lineId: "line2"
+            rollbackPolicy: "free"
+---
+case: load preserves rollback timeline from save data
+in:
+  - state:
+      global:
+        saveSlots:
+          "4":
+            slotKey: "4"
+            date: 1704110600
+            image: "save4.png"
+            state:
+              viewedRegistry:
+                sections:
+                  - sectionId: "sec2"
+                    lastLineId: "line3"
+                resources: []
+              contexts:
+                - pointers:
+                    read: { sectionId: "sec2", lineId: "line3" }
+                  variables:
+                    score: 15
+                  rollback:
+                    currentIndex: 2
+                    isRestoring: false
+                    replayStartIndex: 0
+                    baselineVariables:
+                      score: 0
+                    timeline:
+                      - sectionId: "sec1"
+                        lineId: "line1"
+                        rollbackPolicy: "free"
+                      - sectionId: "sec1"
+                        lineId: "line2"
+                        rollbackPolicy: "free"
+                      - sectionId: "sec2"
+                        lineId: "line3"
+                        rollbackPolicy: "free"
+        pendingEffects: []
+  - slot: 4
+out:
+  global:
+    saveSlots:
+      "4":
+        slotKey: "4"
+        date: 1704110600
+        image: "save4.png"
+        state:
+          viewedRegistry:
+            sections:
+              - sectionId: "sec2"
+                lastLineId: "line3"
+            resources: []
+          contexts:
+            - pointers:
+                read: { sectionId: "sec2", lineId: "line3" }
+              variables:
+                score: 15
+              rollback:
+                currentIndex: 2
+                isRestoring: false
+                replayStartIndex: 0
+                baselineVariables:
+                  score: 0
+                timeline:
+                  - sectionId: "sec1"
+                    lineId: "line1"
+                    rollbackPolicy: "free"
+                  - sectionId: "sec1"
+                    lineId: "line2"
+                    rollbackPolicy: "free"
+                  - sectionId: "sec2"
+                    lineId: "line3"
+                    rollbackPolicy: "free"
+    viewedRegistry:
+      sections:
+        - sectionId: "sec2"
+          lastLineId: "line3"
+      resources: []
+    pendingEffects:
+      - name: "render"
+  contexts:
+    - pointers:
+        read: { sectionId: "sec2", lineId: "line3" }
+      variables:
+        score: 15
+      rollback:
+        currentIndex: 2
+        isRestoring: false
+        replayStartIndex: 0
+        baselineVariables:
+          score: 0
+        timeline:
+          - sectionId: "sec1"
+            lineId: "line1"
+            rollbackPolicy: "free"
+          - sectionId: "sec1"
+            lineId: "line2"
+            rollbackPolicy: "free"
+          - sectionId: "sec2"
+            lineId: "line3"
+            rollbackPolicy: "free"
diff --git a/spec/system/actions/nextLine.spec.yaml b/spec/system/actions/nextLine.spec.yaml
index 3298f047..b185b947 100644
--- a/spec/system/actions/nextLine.spec.yaml
+++ b/spec/system/actions/nextLine.spec.yaml
@@ -180,6 +180,18 @@ out:
         read:
           sectionId: "section1"
           lineId: "2"
+      rollback:
+        currentIndex: 1
+        isRestoring: false
+        replayStartIndex: 1
+        baselineVariables: {}
+        timeline:
+          - sectionId: "section1"
+            lineId: "1"
+            rollbackPolicy: "free"
+          - sectionId: "section1"
+            lineId: "2"
+            rollbackPolicy: "free"
 ---
 case: move to next line keeps fromStart scene auto running
 in:
@@ -255,6 +267,18 @@ out:
         read:
           sectionId: "section1"
           lineId: "2"
+      rollback:
+        currentIndex: 1
+        isRestoring: false
+        replayStartIndex: 1
+        baselineVariables: {}
+        timeline:
+          - sectionId: "section1"
+            lineId: "1"
+            rollbackPolicy: "free"
+          - sectionId: "section1"
+            lineId: "2"
+            rollbackPolicy: "free"
 ---
 case: move to next line resets singleLine applyMode config
 in:
@@ -323,6 +347,117 @@ out:
         read:
           sectionId: "section1"
           lineId: "2"
+      rollback:
+        currentIndex: 1
+        isRestoring: false
+        replayStartIndex: 1
+        baselineVariables: {}
+        timeline:
+          - sectionId: "section1"
+            lineId: "1"
+            rollbackPolicy: "free"
+          - sectionId: "section1"
+            lineId: "2"
+            rollbackPolicy: "free"
+---
+case: move to next line truncates future rollback history after divergence
+in:
+  - state:
+      global:
+        isLineCompleted: true
+        nextLineConfig:
+          manual:
+            enabled: true
+        pendingEffects: []
+        viewedRegistry:
+          sections: []
+      projectData:
+        story:
+          scenes:
+            scene1:
+              sections:
+                section1:
+                  lines:
+                    - id: "1"
+                      actions: {}
+                    - id: "2"
+                      actions: {}
+                    - id: "3"
+                      actions: {}
+                    - id: "4"
+                      actions: {}
+      contexts:
+        - currentPointerMode: "read"
+          pointers:
+            read:
+              sectionId: "section1"
+              lineId: "2"
+          rollback:
+            currentIndex: 1
+            isRestoring: false
+            replayStartIndex: 0
+            baselineVariables: {}
+            timeline:
+              - sectionId: "section1"
+                lineId: "1"
+                rollbackPolicy: "free"
+              - sectionId: "section1"
+                lineId: "2"
+                rollbackPolicy: "free"
+              - sectionId: "section1"
+                lineId: "3"
+                rollbackPolicy: "free"
+              - sectionId: "section1"
+                lineId: "4"
+                rollbackPolicy: "free"
+out:
+  global:
+    isLineCompleted: false
+    nextLineConfig:
+      manual:
+        enabled: true
+    pendingEffects:
+      - name: "handleLineActions"
+    viewedRegistry:
+      sections:
+        - sectionId: "section1"
+          lastLineId: "2"
+  projectData:
+    story:
+      scenes:
+        scene1:
+          sections:
+            section1:
+              lines:
+                - id: "1"
+                  actions: {}
+                - id: "2"
+                  actions: {}
+                - id: "3"
+                  actions: {}
+                - id: "4"
+                  actions: {}
+  contexts:
+    - currentPointerMode: "read"
+      pointers:
+        read:
+          sectionId: "section1"
+          lineId: "3"
+      rollback:
+        currentIndex: 2
+        isRestoring: false
+        replayStartIndex: 0
+        baselineVariables: {}
+        timeline:
+          - sectionId: "section1"
+            lineId: "1"
+            rollbackPolicy: "free"
+          - sectionId: "section1"
+            lineId: "2"
+            rollbackPolicy: "free"
+          - sectionId: "section1"
+            lineId: "3"
+            rollbackPolicy: "free"
 ---
 case: already at last line (no change)
 in:
@@ -676,6 +811,18 @@ out:
         read:
           sectionId: "section1"
           lineId: "2"
+      rollback:
+        currentIndex: 1
+        isRestoring: false
+        replayStartIndex: 1
+        baselineVariables: {}
+        timeline:
+          - sectionId: "section1"
+            lineId: "1"
+            rollbackPolicy: "free"
+          - sectionId: "section1"
+            lineId: "2"
+            rollbackPolicy: "free"
 ---
 case: complete line with scene mode (fromComplete) restarts scene timer
 in:
diff --git a/spec/system/actions/nextLineFromSystem.spec.yaml b/spec/system/actions/nextLineFromSystem.spec.yaml
index 9016d43e..322908fc 100644
--- a/spec/system/actions/nextLineFromSystem.spec.yaml
+++ b/spec/system/actions/nextLineFromSystem.spec.yaml
@@ -104,6 +104,18 @@ out:
         read:
           sectionId: "section1"
           lineId: "2"
+      rollback:
+        currentIndex: 1
+        isRestoring: false
+        replayStartIndex: 1
+        baselineVariables: {}
+        timeline:
+          - sectionId: "section1"
+            lineId: "1"
+            rollbackPolicy: "free"
+          - sectionId: "section1"
+            lineId: "2"
+            rollbackPolicy: "free"
 ---
 case: advance to next line when auto is enabled with fromStart trigger (re-queues timer)
 in:
@@ -167,6 +179,18 @@ out:
         read:
           sectionId: "section1"
           lineId: "2"
+      rollback:
+        currentIndex: 1
+        isRestoring: false
+        replayStartIndex: 1
+        baselineVariables: {}
+        timeline:
+          - sectionId: "section1"
+            lineId: "1"
+            rollbackPolicy: "free"
+          - sectionId: "section1"
+            lineId: "2"
+            rollbackPolicy: "free"
 ---
 case: advance resets singleLine applyMode config and does not re-queue timer
 in:
@@ -231,6 +255,18 @@ out:
         read:
           sectionId: "section1"
           lineId: "2"
+      rollback:
+        currentIndex: 1
+        isRestoring: false
+        replayStartIndex: 1
+        baselineVariables: {}
+        timeline:
+          - sectionId: "section1"
+            lineId: "1"
+            rollbackPolicy: "free"
+          - sectionId: "section1"
+            lineId: "2"
+            rollbackPolicy: "free"
 ---
 case: advance to next line when auto is enabled with fromComplete trigger (does not re-queue timer)
 in:
@@ -291,6 +327,18 @@ out:
         read:
           sectionId: "section1"
           lineId: "2"
+      rollback:
+        currentIndex: 1
+        isRestoring: false
+        replayStartIndex: 1
+        baselineVariables: {}
+        timeline:
+          - sectionId: "section1"
+            lineId: "1"
+            rollbackPolicy: "free"
+          - sectionId: "section1"
+            lineId: "2"
+            rollbackPolicy: "free"
 ---
 case: at last line of section with auto disabled
 in:
diff --git a/spec/system/actions/rollbackByOffset.spec.yaml b/spec/system/actions/rollbackByOffset.spec.yaml
index 7c0d91cd..5737bf3e 100644
--- a/spec/system/actions/rollbackByOffset.spec.yaml
+++ b/spec/system/actions/rollbackByOffset.spec.yaml
@@ -375,3 +375,139 @@ out:
               updateVariableIds:
                 - "act1"
             - id: "3"
+---
+case: rolls back across sections using rollback timeline replay
+in:
+  - state:
+      projectData:
+        story:
+          scenes:
+            scene1:
+              sections:
+                section1:
+                  lines:
+                    - id: "1"
+                    - id: "2"
+                      actions:
+                        updateVariable:
+                          id: "set-score-10"
+                          operations:
+                            - variableId: score
+                              op: set
+                              value: 10
+                section2:
+                  lines:
+                    - id: "10"
+                      actions:
+                        updateVariable:
+                          id: "add-score-5"
+                          operations:
+                            - variableId: score
+                              op: add
+                              value: 5
+                    - id: "11"
+        resources:
+          variables:
+            score:
+              type: number
+              scope: context
+              default: 0
+      global:
+        isLineCompleted: false
+        pendingEffects: []
+      contexts:
+        - variables:
+            score: 15
+          currentPointerMode: "history"
+          pointers:
+            read:
+              sectionId: "section2"
+              lineId: "10"
+            history:
+              sectionId: "section2"
+              lineId: "11"
+              historySequenceIndex: 0
+          rollback:
+            currentIndex: 2
+            isRestoring: false
+            replayStartIndex: 0
+            baselineVariables:
+              score: 0
+            timeline:
+              - sectionId: "section1"
+                lineId: "1"
+                rollbackPolicy: "free"
+              - sectionId: "section1"
+                lineId: "2"
+                rollbackPolicy: "free"
+              - sectionId: "section2"
+                lineId: "10"
+                rollbackPolicy: "free"
+  - offset: -1
+out:
+  projectData:
+    story:
+      scenes:
+        scene1:
+          sections:
+            section1:
+              lines:
+                - id: "1"
+                - id: "2"
+                  actions:
+                    updateVariable:
+                      id: "set-score-10"
+                      operations:
+                        - variableId: score
+                          op: set
+                          value: 10
+            section2:
+              lines:
+                - id: "10"
+                  actions:
+                    updateVariable:
+                      id: "add-score-5"
+                      operations:
+                        - variableId: score
+                          op: add
+                          value: 5
+                - id: "11"
+    resources:
+      variables:
+        score:
+          type: number
+          scope: context
+          default: 0
+  global:
+    isLineCompleted: true
+    pendingEffects:
+      - name: "clearNextLineConfigTimer"
+      - name: "render"
+  contexts:
+    - variables:
+        score: 10
+      currentPointerMode: "read"
+      pointers:
+        read:
+          sectionId: "section1"
+          lineId: "2"
+        history:
+          sectionId: null
+          lineId: null
+          historySequenceIndex: null
+      rollback:
+        currentIndex: 1
+        isRestoring: false
+        replayStartIndex: 0
+        baselineVariables:
+          score: 0
+        timeline:
+          - sectionId: "section1"
+            lineId: "1"
+            rollbackPolicy: "free"
+          - sectionId: "section1"
+            lineId: "2"
+            rollbackPolicy: "free"
+          - sectionId: "section2"
+            lineId: "10"
+            rollbackPolicy: "free"
diff --git a/spec/system/actions/saveSaveSlot.spec.yaml b/spec/system/actions/saveSaveSlot.spec.yaml
index 9c771cb2..fb3067af 100644
--- a/spec/system/actions/saveSaveSlot.spec.yaml
+++ b/spec/system/actions/saveSaveSlot.spec.yaml
@@ -263,3 +263,120 @@ out:
         playerName: "Alice"
         score: 150
         soundEnabled: true
+---
+case: save persists rollback timeline
+in:
+  - state:
+      global:
+        saveSlots: {}
+        pendingEffects: []
+      projectData:
+        story: { initialSceneId: "test" }
+      contexts:
+        - pointers:
+            read: { sectionId: "sec2", lineId: "line3" }
+          variables:
+            score: 15
+          rollback:
+            currentIndex: 2
+            isRestoring: false
+            replayStartIndex: 0
+            baselineVariables:
+              score: 0
+            timeline:
+              - sectionId: "sec1"
+                lineId: "line1"
+                rollbackPolicy: "free"
+              - sectionId: "sec1"
+                lineId: "line2"
+                rollbackPolicy: "free"
+              - sectionId: "sec2"
+                lineId: "line3"
+                rollbackPolicy: "free"
+  - slot: 3
+    thumbnailImage: null
+out:
+  global:
+    saveSlots:
+      "3":
+        slotKey: "3"
+        date: 1700000000000
+        image: null
+        state:
+          contexts:
+            - pointers:
+                read: { sectionId: "sec2", lineId: "line3" }
+              variables:
+                score: 15
+              rollback:
+                currentIndex: 2
+                isRestoring: false
+                replayStartIndex: 0
+                baselineVariables:
+                  score: 0
+                timeline:
+                  - sectionId: "sec1"
+                    lineId: "line1"
+                    rollbackPolicy: "free"
+                  - sectionId: "sec1"
+                    lineId: "line2"
+                    rollbackPolicy: "free"
+                  - sectionId: "sec2"
+                    lineId: "line3"
+                    rollbackPolicy: "free"
+          viewedRegistry: __undefined__
+    pendingEffects:
+      - name: "saveSlots"
+        payload:
+          saveSlots:
+            "3":
+              slotKey: "3"
+              date: 1700000000000
+              image: null
+              state:
+                contexts:
+                  - pointers:
+                      read: { sectionId: "sec2", lineId: "line3" }
+                    variables:
+                      score: 15
+                    rollback:
+                      currentIndex: 2
+                      isRestoring: false
+                      replayStartIndex: 0
+                      baselineVariables:
+                        score: 0
+                      timeline:
+                        - sectionId: "sec1"
+                          lineId: "line1"
+                          rollbackPolicy: "free"
+                        - sectionId: "sec1"
+                          lineId: "line2"
+                          rollbackPolicy: "free"
+                        - sectionId: "sec2"
+                          lineId: "line3"
+                          rollbackPolicy: "free"
+                viewedRegistry: __undefined__
+      - name: "render"
+  projectData:
+    story: { initialSceneId: "test" }
+  contexts:
+    - pointers:
+        read: { sectionId: "sec2", lineId: "line3" }
+      variables:
+        score: 15
+      rollback:
+        currentIndex: 2
+        isRestoring: false
+        replayStartIndex: 0
+        baselineVariables:
+          score: 0
+        timeline:
+          - sectionId: "sec1"
+            lineId: "line1"
+            rollbackPolicy: "free"
+          - sectionId: "sec1"
+            lineId: "line2"
+            rollbackPolicy: "free"
+          - sectionId: "sec2"
+            lineId: "line3"
+            rollbackPolicy: "free"
diff --git a/spec/system/actions/sectionTransition.spec.yaml b/spec/system/actions/sectionTransition.spec.yaml
index 55a03111..2651375e 100644
--- a/spec/system/actions/sectionTransition.spec.yaml
+++ b/spec/system/actions/sectionTransition.spec.yaml
@@ -70,6 +70,18 @@ out:
         read:
           sectionId: "section2"
           lineId: "10"
+      rollback:
+        currentIndex: 1
+        isRestoring: false
+        replayStartIndex: 1
+        baselineVariables: {}
+        timeline:
+          - sectionId: "section1"
+            lineId: "1"
+            rollbackPolicy: "free"
+          - sectionId: "section2"
+            lineId: "10"
+            rollbackPolicy: "free"
 ---
 case: section not found - returns unchanged state
 in:
@@ -177,4 +189,4 @@ out:
       pointers:
         read:
           sectionId: "section1"
-          lineId: "1"
\ No newline at end of file
+          lineId: "1"
diff --git a/spec/system/createInitialState.spec.yaml b/spec/system/createInitialState.spec.yaml
index 7ded0fa2..d2f5423e 100644
--- a/spec/system/createInitialState.spec.yaml
+++ b/spec/system/createInitialState.spec.yaml
@@ -71,6 +71,15 @@ out:
       views: []
       bgm:
         resourceId: __undefined__
+      rollback:
+        currentIndex: 0
+        isRestoring: false
+        replayStartIndex: 0
+        baselineVariables: {}
+        timeline:
+          - sectionId: "section1"
+            lineId: "line1"
+            rollbackPolicy: "free"
       variables: {}
 ---
 case: initialize object type variables with defaults
@@ -179,6 +188,19 @@ out:
       views: []
       bgm:
         resourceId: __undefined__
+      rollback:
+        currentIndex: 0
+        isRestoring: false
+        replayStartIndex: 0
+        baselineVariables:
+          inventory:
+            items:
+              - id: sword
+                name: Steel Sword
+        timeline:
+          - sectionId: "section1"
+            lineId: "line1"
+            rollbackPolicy: "free"
       variables:
         inventory:
           items:
@@ -262,6 +284,16 @@ out:
       views: []
       bgm:
         resourceId: __undefined__
+      rollback:
+        currentIndex: 0
+        isRestoring: false
+        replayStartIndex: 0
+        baselineVariables:
+          settings: {}
+        timeline:
+          - sectionId: "section1"
+            lineId: "line1"
+            rollbackPolicy: "free"
       variables:
         settings: {}
 ---
@@ -365,6 +397,15 @@ out:
       views: []
       bgm:
         resourceId: __undefined__
+      rollback:
+        currentIndex: 0
+        isRestoring: false
+        replayStartIndex: 0
+        baselineVariables: {}
+        timeline:
+          - sectionId: "section1"
+            lineId: "line1"
+            rollbackPolicy: "free"
       variables: {}
 ---
 case: initialize with specific initialLineId
@@ -439,4 +480,13 @@ out:
       views: []
       bgm:
         resourceId: __undefined__
-      variables: {}
\ No newline at end of file
+      rollback:
+        currentIndex: 0
+        isRestoring: false
+        replayStartIndex: 0
+        baselineVariables: {}
+        timeline:
+          - sectionId: "section1"
+            lineId: "line2"
+            rollbackPolicy: "free"
+      variables: {}
diff --git a/src/stores/system.store.js b/src/stores/system.store.js
index 79a04970..c382f3ec 100644
--- a/src/stores/system.store.js
+++ b/src/stores/system.store.js
@@ -44,6 +44,190 @@ const resetNextLineConfigIfSingleLine = (state) => {
   }
 };
 
+const createRollbackCheckpoint = ({ sectionId, lineId, rollbackPolicy }) => ({
+  sectionId,
+  lineId,
+  rollbackPolicy: rollbackPolicy ?? "free",
+});
+
+const createRollbackState = ({
+  pointer,
+  baselineVariables,
+  replayStartIndex = 0,
+}) => {
+  const hasInitialPointer = pointer?.sectionId && pointer?.lineId;
+
+  return {
+    currentIndex: hasInitialPointer ? 0 : -1,
+    isRestoring: false,
+    replayStartIndex,
+    baselineVariables: structuredClone(baselineVariables ?? {}),
+    timeline: hasInitialPointer
+      ? [
+          createRollbackCheckpoint({
+            sectionId: pointer.sectionId,
+            lineId: pointer.lineId,
+          }),
+        ]
+      : [],
+  };
+};
+
+const ensureRollbackState = (lastContext, options = {}) => {
+  if (lastContext?.rollback) {
+    if (!Array.isArray(lastContext.rollback.timeline)) {
+      lastContext.rollback.timeline = [];
+    }
+    if (typeof lastContext.rollback.currentIndex !== "number") {
+      lastContext.rollback.currentIndex =
+        lastContext.rollback.timeline.length > 0
+          ? lastContext.rollback.timeline.length - 1
+          : -1;
+    }
+    if (typeof lastContext.rollback.isRestoring !== "boolean") {
+      lastContext.rollback.isRestoring = false;
+    }
+    if (typeof lastContext.rollback.replayStartIndex !== "number") {
+      lastContext.rollback.replayStartIndex = 0;
+    }
+    if (lastContext.rollback.baselineVariables === undefined) {
+      lastContext.rollback.baselineVariables = structuredClone(
+        lastContext.variables ?? {},
+      );
+    }
+    return lastContext.rollback;
+  }
+
+  const pointer = lastContext?.pointers?.read;
+  lastContext.rollback = createRollbackState({
+    pointer,
+    baselineVariables: lastContext?.variables ?? {},
+    replayStartIndex: options.compatibilityAnchor ? 1 : 0,
+  });
+  return lastContext.rollback;
+};
+
+const appendRollbackCheckpoint = (state, payload) => {
+  const lastContext = state.contexts?.[state.contexts.length - 1];
+  if (!lastContext) {
+    return;
+  }
+
+  const rollback = ensureRollbackState(lastContext);
+  if (rollback.isRestoring) {
+    return;
+  }
+
+  if (rollback.currentIndex < rollback.timeline.length - 1) {
+    rollback.timeline = rollback.timeline.slice(0, rollback.currentIndex + 1);
+  }
+
+  const lastCheckpoint = rollback.timeline[rollback.timeline.length - 1];
+  if (
+    lastCheckpoint?.sectionId === payload.sectionId &&
+    lastCheckpoint?.lineId === payload.lineId &&
+    (lastCheckpoint?.rollbackPolicy ?? "free") ===
+      (payload.rollbackPolicy ?? "free")
+  ) {
+    rollback.currentIndex = rollback.timeline.length - 1;
+    return;
+  }
+
+  rollback.timeline.push(createRollbackCheckpoint(payload));
+  rollback.currentIndex = rollback.timeline.length - 1;
+};
+
+const applyRollbackableLineActions = (state, payload) => {
+  const { sectionId, lineId } = payload;
+  const section = selectSection({ state }, { sectionId });
+  const line = section?.lines?.find((item) => item.id === lineId);
+  const updateVariableAction = line?.actions?.updateVariable;
+
+  if (!updateVariableAction) {
+    return;
+  }
+
+  const lastContext = state.contexts?.[state.contexts.length - 1];
+  if (!lastContext) {
+    return;
+  }
+
+  const operations = updateVariableAction.operations || [];
+  for (const { variableId, op, value } of operations) {
+    const variableConfig = state.projectData.resources?.variables?.[variableId];
+    const scope = variableConfig?.scope;
+    const type = variableConfig?.type;
+
+    validateVariableScope(scope, variableId);
+    validateVariableOperation(type, op, variableId);
+
+    if (scope === "context") {
+      lastContext.variables[variableId] = applyVariableOperation(
+        lastContext.variables[variableId],
+        op,
+        value,
+      );
+    }
+  }
+};
+
+const restoreRollbackCheckpoint = (state, checkpointIndex) => {
+  const lastContext = state.contexts?.[state.contexts.length - 1];
+  if (!lastContext) {
+    return state;
+  }
+
+  const rollback = ensureRollbackState(lastContext);
+  const checkpoint = rollback.timeline[checkpointIndex];
+  if (!checkpoint) {
+    return state;
+  }
+
+  if (state.global.autoMode) {
+    stopAutoMode({ state });
+  }
+  if (state.global.skipMode) {
+    stopSkipMode({ state });
+  }
+
+  state.global.pendingEffects.push({
+    name: "clearNextLineConfigTimer",
+  });
+
+  rollback.isRestoring = true;
+  rollback.currentIndex = checkpointIndex;
+
+  lastContext.variables = structuredClone(rollback.baselineVariables ?? {});
+
+  const replayStartIndex = rollback.replayStartIndex ?? 0;
+  for (let i = replayStartIndex; i <= checkpointIndex; i++) {
+    applyRollbackableLineActions(state, rollback.timeline[i]);
+  }
+
+  lastContext.pointers.read = {
+    sectionId: checkpoint.sectionId,
+    lineId: checkpoint.lineId,
+  };
+
+  lastContext.currentPointerMode = "read";
+  if (lastContext.pointers?.history) {
+    lastContext.pointers.history = {
+      sectionId: null,
+      lineId: null,
+      historySequenceIndex: null,
+    };
+  }
+
+  state.global.isLineCompleted = true;
+  rollback.isRestoring = false;
+
+  state.global.pendingEffects.push({
+    name: "render",
+  });
+
+  return state;
+};
+
 export const createInitialState = (payload) => {
   const { projectData } = payload;
   const global = payload.global ?? {};
@@ -116,6 +300,10 @@ export const createInitialState = (payload) => {
           resourceId: undefined,
         },
         variables: contextVariableDefaultValues,
+        rollback: createRollbackState({
+          pointer: initialPointer,
+          baselineVariables: contextVariableDefaultValues,
+        }),
       },
     ],
   };
@@ -941,8 +1129,8 @@ export const saveSaveSlot = ({ state }, payload) => {
   const slotKey = String(slot);
 
   const currentState = {
-    contexts: [...state.contexts],
-    viewedRegistry: state.global.viewedRegistry,
+    contexts: structuredClone(state.contexts),
+    viewedRegistry: structuredClone(state.global.viewedRegistry),
   };
 
   const saveData = {
@@ -979,7 +1167,10 @@ export const loadSaveSlot = ({ state }, payload) => {
   const slotData = state.global.saveSlots[slotKey];
   if (slotData) {
     state.global.viewedRegistry = slotData.state.viewedRegistry;
-    state.contexts = slotData.state.contexts;
+    state.contexts = structuredClone(slotData.state.contexts);
+    state.contexts?.forEach((context) => {
+      ensureRollbackState(context, { compatibilityAnchor: !context.rollback });
+    });
     state.global.pendingEffects.push({ name: "render" });
   }
   return state;
@@ -1066,9 +1257,6 @@ export const jumpToLine = ({ state }, payload) => {
   // Reset line completion state
   state.global.isLineCompleted = false;
 
-  // Add line to history for rollback support
-  addLineToHistory({ state }, { lineId });
-
   // Add appropriate pending effects
   state.global.pendingEffects.push({
     name: "handleLineActions",
@@ -1195,6 +1383,7 @@ export const nextLine = ({ state }) => {
   const pointer = selectCurrentPointer({ state })?.pointer;
   const sectionId = pointer?.sectionId;
   const section = selectSection({ state }, { sectionId });
+  const lastContext = state.contexts[state.contexts.length - 1];
 
   const lines = section?.lines || [];
   const currentLineIndex = lines.findIndex(
@@ -1223,7 +1412,9 @@ export const nextLine = ({ state }) => {
       }
     }
 
-    const lastContext = state.contexts[state.contexts.length - 1];
+    if (lastContext && !lastContext.rollback) {
+      ensureRollbackState(lastContext, { compatibilityAnchor: true });
+    }
 
     if (lastContext) {
       // Mark current line as viewed before moving
@@ -1242,6 +1433,10 @@ export const nextLine = ({ state }) => {
 
     // Add line to history for rollback support
     addLineToHistory({ state }, { lineId: nextLine.id });
+    appendRollbackCheckpoint(state, {
+      sectionId,
+      lineId: nextLine.id,
+    });
     resetNextLineConfigIfSingleLine(state);
 
     state.global.pendingEffects.push({
@@ -1449,6 +1644,10 @@ export const sectionTransition = ({ state }, payload) => {
   // Update current pointer to new section's first line
   const lastContext = state.contexts[state.contexts.length - 1];
   if (lastContext) {
+    if (!lastContext.rollback) {
+      ensureRollbackState(lastContext, { compatibilityAnchor: true });
+    }
+
     lastContext.pointers.read = {
       sectionId,
       lineId: firstLine.id,
@@ -1459,6 +1658,10 @@ export const sectionTransition = ({ state }, payload) => {
 
     // Add first line to history
     addLineToHistory({ state }, { lineId: firstLine.id });
+    appendRollbackCheckpoint(state, {
+      sectionId,
+      lineId: firstLine.id,
+    });
   }
 
   // Reset line completion state
@@ -1486,6 +1689,7 @@ export const nextLineFromSystem = ({ state }) => {
   const pointer = selectCurrentPointer({ state })?.pointer;
   const sectionId = pointer?.sectionId;
   const section = selectSection({ state }, { sectionId });
+  const lastContext = state.contexts[state.contexts.length - 1];
 
   const lines = section?.lines || [];
   const currentLineIndex = lines.findIndex(
@@ -1514,7 +1718,9 @@ export const nextLineFromSystem = ({ state }) => {
       }
     }
 
-    const lastContext = state.contexts[state.contexts.length - 1];
+    if (lastContext && !lastContext.rollback) {
+      ensureRollbackState(lastContext, { compatibilityAnchor: true });
+    }
 
     if (lastContext) {
       const currentLineId = lastContext.pointers.read.lineId;
@@ -1532,6 +1738,10 @@ export const nextLineFromSystem = ({ state }) => {
 
     // Add line to history for rollback support
     addLineToHistory({ state }, { lineId: nextLine.id });
+    appendRollbackCheckpoint(state, {
+      sectionId,
+      lineId: nextLine.id,
+    });
     resetNextLineConfigIfSingleLine(state);
 
     state.global.pendingEffects.push({
@@ -1573,6 +1783,9 @@ export const updateVariable = ({ state }, payload) => {
   }
 
   const lastContext = state.contexts[state.contexts.length - 1];
+  if (lastContext?.rollback?.isRestoring) {
+    return state;
+  }
 
   // Track which scopes are modified
   let contextVariableModified = false;
@@ -1735,6 +1948,23 @@ export const selectLineIdByOffset = ({ state }, payload) => {
     return null;
   }
 
+  const rollback = lastContext.rollback;
+  if (
+    Array.isArray(rollback?.timeline) &&
+    typeof rollback?.currentIndex === "number"
+  ) {
+    const targetIndex = rollback.currentIndex + offset;
+    if (targetIndex < 0 || targetIndex >= rollback.timeline.length) {
+      return null;
+    }
+
+    const targetLine = rollback.timeline[targetIndex];
+    return {
+      sectionId: targetLine.sectionId,
+      lineId: targetLine.lineId,
+    };
+  }
+
   // Get current position from read pointer
   const currentSectionId = lastContext.pointers.read?.sectionId;
   const currentLineId = lastContext.pointers.read?.lineId;
@@ -1813,15 +2043,28 @@ export const rollbackByOffset = ({ state }, payload) => {
     throw new Error("rollbackByOffset requires a negative offset");
   }
 
+  const lastContext = state.contexts?.[state.contexts.length - 1];
+  const rollback = lastContext?.rollback;
+
+  if (
+    Array.isArray(rollback?.timeline) &&
+    typeof rollback?.currentIndex === "number"
+  ) {
+    const targetIndex = rollback.currentIndex + offset;
+    if (targetIndex < 0 || targetIndex >= rollback.timeline.length) {
+      return state;
+    }
+
+    return restoreRollbackCheckpoint(state, targetIndex);
+  }
+
   // Get target using the selector
   const target = selectLineIdByOffset({ state }, { offset });
 
   if (!target) {
-    // Out of bounds or invalid - do nothing
     return state;
   }
 
-  // Delegate to rollbackToLine for the actual rollback with variable reversion
   return rollbackToLine(
     { state },
     {
@@ -1858,6 +2101,26 @@ export const rollbackToLine = ({ state }, payload) => {
     throw new Error("No context available for rollbackToLine");
   }
 
+  const rollback = lastContext.rollback;
+  if (Array.isArray(rollback?.timeline) && rollback.timeline.length > 0) {
+    const visibleTimeline = rollback.timeline.slice(
+      0,
+      rollback.currentIndex + 1,
+    );
+    const targetLineIndex = visibleTimeline.findLastIndex(
+      (checkpoint) =>
+        checkpoint.sectionId === sectionId && checkpoint.lineId === lineId,
+    );
+
+    if (targetLineIndex === -1) {
+      throw new Error(
+        `Line ${lineId} not found in section ${sectionId} rollback timeline`,
+      );
+    }
+
+    return restoreRollbackCheckpoint(state, targetLineIndex);
+  }
+
   // Find the section in history
   const historySequence = lastContext.historySequence;
   const sectionEntry = historySequence?.find(

From 76f6f89dce2439282835562d0de44f50df8588e8 Mon Sep 17 00:00:00 2001
From: han4wluc <han4wluc@yuusoft.com>
Date: Fri, 27 Mar 2026 22:57:08 +0800
Subject: [PATCH 2/5] Fix rollback draft safety and restore replay

---
 .../system/actions/rollbackByOffset.spec.yaml |  25 ++
 spec/systemStore.rollbackDraftSafety.test.js  | 282 ++++++++++++++++++
 src/stores/system.store.js                    |  69 ++++-
 3 files changed, 368 insertions(+), 8 deletions(-)
 create mode 100644 spec/systemStore.rollbackDraftSafety.test.js

diff --git a/spec/system/actions/rollbackByOffset.spec.yaml b/spec/system/actions/rollbackByOffset.spec.yaml
index 5737bf3e..53ae5669 100644
--- a/spec/system/actions/rollbackByOffset.spec.yaml
+++ b/spec/system/actions/rollbackByOffset.spec.yaml
@@ -389,6 +389,10 @@ in:
                     - id: "1"
                     - id: "2"
                       actions:
+                        setNextLineConfig:
+                          manual:
+                            enabled: false
+                            requireLineCompleted: true
                         updateVariable:
                           id: "set-score-10"
                           operations:
@@ -414,6 +418,13 @@ in:
               default: 0
       global:
         isLineCompleted: false
+        nextLineConfig:
+          manual:
+            enabled: true
+            requireLineCompleted: false
+          auto:
+            enabled: false
+          applyMode: "persistent"
         pendingEffects: []
       contexts:
         - variables:
@@ -455,6 +466,10 @@ out:
                 - id: "1"
                 - id: "2"
                   actions:
+                    setNextLineConfig:
+                      manual:
+                        enabled: false
+                        requireLineCompleted: true
                     updateVariable:
                       id: "set-score-10"
                       operations:
@@ -480,6 +495,16 @@ out:
           default: 0
   global:
     isLineCompleted: true
+    dialogueUIHidden: false
+    isDialogueHistoryShowing: false
+    layeredViews: []
+    nextLineConfig:
+      manual:
+        enabled: false
+        requireLineCompleted: true
+      auto:
+        enabled: false
+      applyMode: "persistent"
     pendingEffects:
       - name: "clearNextLineConfigTimer"
       - name: "render"
diff --git a/spec/systemStore.rollbackDraftSafety.test.js b/spec/systemStore.rollbackDraftSafety.test.js
new file mode 100644
index 00000000..3e3f329e
--- /dev/null
+++ b/spec/systemStore.rollbackDraftSafety.test.js
@@ -0,0 +1,282 @@
+import { describe, expect, it, vi } from "vitest";
+import { produce } from "immer";
+import {
+  loadSaveSlot,
+  rollbackByOffset,
+  saveSaveSlot,
+} from "../src/stores/system.store.js";
+
+const createProjectData = () => ({
+  story: {
+    initialSceneId: "scene1",
+    scenes: {
+      scene1: {
+        initialSectionId: "section1",
+        sections: {
+          section1: {
+            lines: [
+              { id: "1" },
+              {
+                id: "2",
+                actions: {
+                  setNextLineConfig: {
+                    manual: {
+                      enabled: false,
+                      requireLineCompleted: true,
+                    },
+                  },
+                  updateVariable: {
+                    id: "set-score-10",
+                    operations: [
+                      {
+                        variableId: "score",
+                        op: "set",
+                        value: 10,
+                      },
+                    ],
+                  },
+                },
+              },
+              { id: "3" },
+            ],
+          },
+          section2: {
+            lines: [{ id: "10" }],
+          },
+        },
+      },
+    },
+  },
+  resources: {
+    variables: {
+      score: {
+        type: "number",
+        scope: "context",
+        default: 0,
+      },
+    },
+  },
+});
+
+describe("system.store rollback/save draft safety", () => {
+  it("saveSaveSlot does not throw when cloning live draft state", () => {
+    vi.spyOn(Date, "now").mockReturnValue(1700000000000);
+
+    const baseState = {
+      global: {
+        saveSlots: {},
+        viewedRegistry: {
+          sections: [{ sectionId: "section1", lastLineId: "2" }],
+          resources: [],
+        },
+        pendingEffects: [],
+      },
+      projectData: createProjectData(),
+      contexts: [
+        {
+          pointers: {
+            read: { sectionId: "section1", lineId: "2" },
+          },
+          variables: {
+            score: 10,
+          },
+          rollback: {
+            currentIndex: 1,
+            isRestoring: false,
+            replayStartIndex: 0,
+            baselineVariables: {
+              score: 0,
+            },
+            timeline: [
+              {
+                sectionId: "section1",
+                lineId: "1",
+                rollbackPolicy: "free",
+              },
+              {
+                sectionId: "section1",
+                lineId: "2",
+                rollbackPolicy: "free",
+              },
+            ],
+          },
+        },
+      ],
+    };
+
+    const nextState = produce(baseState, (draft) => {
+      saveSaveSlot({ state: draft }, { slot: 1, thumbnailImage: null });
+    });
+
+    expect(nextState.global.saveSlots["1"]?.state?.contexts?.[0]?.rollback)
+      .toEqual(baseState.contexts[0].rollback);
+    vi.restoreAllMocks();
+  });
+
+  it("loadSaveSlot does not throw when restoring slot state from a live draft", () => {
+    const savedRollback = {
+      currentIndex: 2,
+      isRestoring: false,
+      replayStartIndex: 0,
+      baselineVariables: {
+        score: 0,
+      },
+      timeline: [
+        {
+          sectionId: "section1",
+          lineId: "1",
+          rollbackPolicy: "free",
+        },
+        {
+          sectionId: "section1",
+          lineId: "2",
+          rollbackPolicy: "free",
+        },
+        {
+          sectionId: "section2",
+          lineId: "10",
+          rollbackPolicy: "free",
+        },
+      ],
+    };
+
+    const baseState = {
+      global: {
+        saveSlots: {
+          "1": {
+            slotKey: "1",
+            date: 1700000000000,
+            image: null,
+            state: {
+              viewedRegistry: {
+                sections: [{ sectionId: "section2", lastLineId: "10" }],
+                resources: [],
+              },
+              contexts: [
+                {
+                  pointers: {
+                    read: { sectionId: "section2", lineId: "10" },
+                  },
+                  variables: {
+                    score: 15,
+                  },
+                  rollback: savedRollback,
+                },
+              ],
+            },
+          },
+        },
+        viewedRegistry: {
+          sections: [],
+          resources: [],
+        },
+        pendingEffects: [],
+      },
+      contexts: [
+        {
+          pointers: {
+            read: { sectionId: "section1", lineId: "1" },
+          },
+          variables: {
+            score: 0,
+          },
+        },
+      ],
+    };
+
+    const nextState = produce(baseState, (draft) => {
+      loadSaveSlot({ state: draft }, { slot: 1 });
+    });
+
+    expect(nextState.contexts[0].rollback).toEqual(savedRollback);
+    expect(nextState.global.viewedRegistry.sections[0]).toEqual({
+      sectionId: "section2",
+      lastLineId: "10",
+    });
+  });
+
+  it("rollbackByOffset restores variables and current-line system state from a live draft", () => {
+    const baseState = {
+      projectData: createProjectData(),
+      global: {
+        isLineCompleted: false,
+        dialogueUIHidden: false,
+        isDialogueHistoryShowing: false,
+        nextLineConfig: {
+          manual: {
+            enabled: true,
+            requireLineCompleted: false,
+          },
+          auto: {
+            enabled: false,
+          },
+          applyMode: "persistent",
+        },
+        layeredViews: [],
+        pendingEffects: [],
+      },
+      contexts: [
+        {
+          variables: {
+            score: 10,
+          },
+          currentPointerMode: "history",
+          pointers: {
+            read: { sectionId: "section1", lineId: "3" },
+            history: {
+              sectionId: "section2",
+              lineId: "10",
+              historySequenceIndex: 0,
+            },
+          },
+          rollback: {
+            currentIndex: 2,
+            isRestoring: false,
+            replayStartIndex: 0,
+            baselineVariables: {
+              score: 0,
+            },
+            timeline: [
+              {
+                sectionId: "section1",
+                lineId: "1",
+                rollbackPolicy: "free",
+              },
+              {
+                sectionId: "section1",
+                lineId: "2",
+                rollbackPolicy: "free",
+              },
+              {
+                sectionId: "section1",
+                lineId: "3",
+                rollbackPolicy: "free",
+              },
+            ],
+          },
+        },
+      ],
+    };
+
+    const nextState = produce(baseState, (draft) => {
+      rollbackByOffset({ state: draft }, { offset: -1 });
+    });
+
+    expect(nextState.contexts[0].variables.score).toBe(10);
+    expect(nextState.contexts[0].pointers.read).toEqual({
+      sectionId: "section1",
+      lineId: "2",
+    });
+    expect(nextState.contexts[0].currentPointerMode).toBe("read");
+    expect(nextState.global.nextLineConfig).toEqual({
+      manual: {
+        enabled: false,
+        requireLineCompleted: true,
+      },
+      auto: {
+        enabled: false,
+      },
+      applyMode: "persistent",
+    });
+  });
+});
diff --git a/src/stores/system.store.js b/src/stores/system.store.js
index c382f3ec..22ada45a 100644
--- a/src/stores/system.store.js
+++ b/src/stores/system.store.js
@@ -1,3 +1,4 @@
+import { current, isDraft } from "immer";
 import {
   createStore,
   getDefaultVariablesFromProjectData,
@@ -44,6 +45,11 @@ const resetNextLineConfigIfSingleLine = (state) => {
   }
 };
 
+const cloneStateValue = (value) => {
+  const source = isDraft(value) ? current(value) : value;
+  return structuredClone(source);
+};
+
 const createRollbackCheckpoint = ({ sectionId, lineId, rollbackPolicy }) => ({
   sectionId,
   lineId,
@@ -61,7 +67,7 @@ const createRollbackState = ({
     currentIndex: hasInitialPointer ? 0 : -1,
     isRestoring: false,
     replayStartIndex,
-    baselineVariables: structuredClone(baselineVariables ?? {}),
+    baselineVariables: cloneStateValue(baselineVariables ?? {}),
     timeline: hasInitialPointer
       ? [
           createRollbackCheckpoint({
@@ -91,7 +97,7 @@ const ensureRollbackState = (lastContext, options = {}) => {
       lastContext.rollback.replayStartIndex = 0;
     }
     if (lastContext.rollback.baselineVariables === undefined) {
-      lastContext.rollback.baselineVariables = structuredClone(
+      lastContext.rollback.baselineVariables = cloneStateValue(
         lastContext.variables ?? {},
       );
     }
@@ -171,6 +177,39 @@ const applyRollbackableLineActions = (state, payload) => {
   }
 };
 
+const applyRollbackRestorableLineActions = (state, payload) => {
+  const { sectionId, lineId } = payload;
+  const section = selectSection({ state }, { sectionId });
+  const line = section?.lines?.find((item) => item.id === lineId);
+  const actions = line?.actions;
+
+  if (!actions) {
+    return;
+  }
+
+  const restorableActions = {
+    showDialogueUI,
+    hideDialogueUI,
+    toggleDialogueUI,
+    showDialogueHistory,
+    hideDialogueHistory,
+    setNextLineConfig,
+    pushLayeredView,
+    popLayeredView,
+    replaceLastLayeredView,
+    clearLayeredViews,
+  };
+
+  Object.entries(actions).forEach(([actionType, actionPayload]) => {
+    const action = restorableActions[actionType];
+    if (!action) {
+      return;
+    }
+
+    action({ state }, actionPayload);
+  });
+};
+
 const restoreRollbackCheckpoint = (state, checkpointIndex) => {
   const lastContext = state.contexts?.[state.contexts.length - 1];
   if (!lastContext) {
@@ -197,11 +236,20 @@ const restoreRollbackCheckpoint = (state, checkpointIndex) => {
   rollback.isRestoring = true;
   rollback.currentIndex = checkpointIndex;
 
-  lastContext.variables = structuredClone(rollback.baselineVariables ?? {});
+  lastContext.variables = cloneStateValue(rollback.baselineVariables ?? {});
+  state.global.dialogueUIHidden = false;
+  state.global.isDialogueHistoryShowing = false;
+  state.global.nextLineConfig = cloneStateValue(DEFAULT_NEXT_LINE_CONFIG);
+  state.global.layeredViews = [];
+  state.global.isLineCompleted = true;
 
   const replayStartIndex = rollback.replayStartIndex ?? 0;
   for (let i = replayStartIndex; i <= checkpointIndex; i++) {
+    if (i > replayStartIndex) {
+      resetNextLineConfigIfSingleLine(state);
+    }
     applyRollbackableLineActions(state, rollback.timeline[i]);
+    applyRollbackRestorableLineActions(state, rollback.timeline[i]);
   }
 
   lastContext.pointers.read = {
@@ -218,9 +266,12 @@ const restoreRollbackCheckpoint = (state, checkpointIndex) => {
     };
   }
 
-  state.global.isLineCompleted = true;
   rollback.isRestoring = false;
 
+  state.global.pendingEffects = state.global.pendingEffects.filter(
+    (effect) => effect?.name !== "render",
+  );
+
   state.global.pendingEffects.push({
     name: "render",
   });
@@ -1129,8 +1180,8 @@ export const saveSaveSlot = ({ state }, payload) => {
   const slotKey = String(slot);
 
   const currentState = {
-    contexts: structuredClone(state.contexts),
-    viewedRegistry: structuredClone(state.global.viewedRegistry),
+    contexts: cloneStateValue(state.contexts),
+    viewedRegistry: cloneStateValue(state.global.viewedRegistry),
   };
 
   const saveData = {
@@ -1166,8 +1217,10 @@ export const loadSaveSlot = ({ state }, payload) => {
   const slotKey = String(slot);
   const slotData = state.global.saveSlots[slotKey];
   if (slotData) {
-    state.global.viewedRegistry = slotData.state.viewedRegistry;
-    state.contexts = structuredClone(slotData.state.contexts);
+    state.global.viewedRegistry = cloneStateValue(
+      slotData.state.viewedRegistry,
+    );
+    state.contexts = cloneStateValue(slotData.state.contexts);
     state.contexts?.forEach((context) => {
       ensureRollbackState(context, { compatibilityAnchor: !context.rollback });
     });

From cff5ec78fe6143caeab46bddc7b5b03309eee928 Mon Sep 17 00:00:00 2001
From: han4wluc <han4wluc@yuusoft.com>
Date: Mon, 30 Mar 2026 20:32:01 +0800
Subject: [PATCH 3/5] Implement rollback timeline and expand VT coverage

---
 rettangoli.config.yaml                        |   2 +
 spec/RouteEngine.systemState.test.js          | 128 +++++
 .../system/actions/rollbackByOffset.spec.yaml | 358 ++++++++++---
 spec/system/actions/rollbackToLine.spec.yaml  | 474 ++++++++++------
 .../actions/setNextLineConfig.spec.yaml       |  34 ++
 .../selectors/selectLineIdByOffset.spec.yaml  |  73 ++-
 spec/systemStore.rollbackDraftSafety.test.js  | 239 ++++++++-
 src/RouteEngine.js                            |  11 +-
 src/stores/constructRenderState.js            |   1 -
 src/stores/system.store.js                    | 505 ++++++++----------
 .../rollback/auto-suppressed--capture-01.webp |   3 +
 .../rollback/back-one-line--capture-01.webp   |   3 +
 .../rollback/by-offset--capture-01.webp       |   3 +
 .../rollback/choice-event--capture-01.webp    |   3 +
 .../rollback/cross-section--capture-01.webp   |   3 +
 .../layered-view-restore--capture-01.webp     |   3 +
 .../rollback/to-line--capture-01.webp         |   3 +
 .../variables/rollback-offset-test-01.webp    |   3 -
 vt/reference/variables/rollback-test-01.webp  |   3 -
 vt/specs/rollback/auto-suppressed.yaml        | 137 +++++
 vt/specs/rollback/back-one-line.yaml          | 413 ++++++++++++++
 vt/specs/rollback/by-offset.yaml              | 223 ++++++++
 vt/specs/rollback/choice-event.yaml           | 225 ++++++++
 vt/specs/rollback/cross-section.yaml          | 184 +++++++
 vt/specs/rollback/layered-view-restore.yaml   | 219 ++++++++
 .../to-line.yaml}                             | 162 +++---
 vt/specs/variables/rollback-offset-test.yaml  | 273 ----------
 27 files changed, 2798 insertions(+), 890 deletions(-)
 create mode 100644 vt/reference/rollback/auto-suppressed--capture-01.webp
 create mode 100644 vt/reference/rollback/back-one-line--capture-01.webp
 create mode 100644 vt/reference/rollback/by-offset--capture-01.webp
 create mode 100644 vt/reference/rollback/choice-event--capture-01.webp
 create mode 100644 vt/reference/rollback/cross-section--capture-01.webp
 create mode 100644 vt/reference/rollback/layered-view-restore--capture-01.webp
 create mode 100644 vt/reference/rollback/to-line--capture-01.webp
 delete mode 100644 vt/reference/variables/rollback-offset-test-01.webp
 delete mode 100644 vt/reference/variables/rollback-test-01.webp
 create mode 100644 vt/specs/rollback/auto-suppressed.yaml
 create mode 100644 vt/specs/rollback/back-one-line.yaml
 create mode 100644 vt/specs/rollback/by-offset.yaml
 create mode 100644 vt/specs/rollback/choice-event.yaml
 create mode 100644 vt/specs/rollback/cross-section.yaml
 create mode 100644 vt/specs/rollback/layered-view-restore.yaml
 rename vt/specs/{variables/rollback-test.yaml => rollback/to-line.yaml} (53%)
 delete mode 100644 vt/specs/variables/rollback-offset-test.yaml

diff --git a/rettangoli.config.yaml b/rettangoli.config.yaml
index 5c6a34bf..f342ea24 100644
--- a/rettangoli.config.yaml
+++ b/rettangoli.config.yaml
@@ -43,6 +43,8 @@ vt:
           files: "save"
         - title: "Keyboard"
           files: "keyboard"
+        - title: "Rollback"
+          files: "rollback"
         - title: "Variables"
           files: "variables"
         - title: "initialization"
diff --git a/spec/RouteEngine.systemState.test.js b/spec/RouteEngine.systemState.test.js
index 8b13de61..ca3e87c4 100644
--- a/spec/RouteEngine.systemState.test.js
+++ b/spec/RouteEngine.systemState.test.js
@@ -37,6 +37,74 @@ const createMinimalProjectData = () => ({
   },
 });
 
+const createRollbackChoiceProjectData = () => ({
+  screen: {
+    width: 1920,
+    height: 1080,
+    backgroundColor: "#000000",
+  },
+  resources: {
+    layouts: {},
+    sounds: {},
+    images: {},
+    videos: {},
+    sprites: {},
+    characters: {},
+    variables: {
+      score: {
+        type: "number",
+        scope: "context",
+        default: 0,
+      },
+    },
+    transforms: {},
+    sectionTransitions: {},
+    animations: {},
+    fonts: {},
+    colors: {},
+    textStyles: {},
+  },
+  story: {
+    initialSceneId: "scene1",
+    scenes: {
+      scene1: {
+        initialSectionId: "source",
+        sections: {
+          source: {
+            lines: [{ id: "line1", actions: {} }],
+          },
+          result: {
+            lines: [
+              {
+                id: "line1",
+                actions: {
+                  dialogue: {
+                    content: [{ text: "Result" }],
+                  },
+                },
+              },
+            ],
+          },
+        },
+      },
+    },
+  },
+});
+
+const createRouteEngineWithInlineEffects = () => {
+  let engine;
+  const handlePendingEffects = (pendingEffects) => {
+    pendingEffects.forEach((effect) => {
+      if (effect.name === "handleLineActions") {
+        engine.handleLineActions();
+      }
+    });
+  };
+
+  engine = createRouteEngine({ handlePendingEffects });
+  return engine;
+};
+
 describe("RouteEngine selectSystemState", () => {
   it("returns a cloned system-state snapshot", () => {
     const engine = createRouteEngine({
@@ -72,4 +140,64 @@ describe("RouteEngine selectSystemState", () => {
     expect(engine.selectCurrentLine).toBeUndefined();
     expect(engine.selectNextLineConfig).toBeUndefined();
   });
+
+  it("records a mixed interaction batch on the checkpoint where the batch started", () => {
+    const engine = createRouteEngineWithInlineEffects();
+
+    engine.init({
+      initialState: {
+        global: {
+          variables: {},
+        },
+        projectData: createRollbackChoiceProjectData(),
+      },
+    });
+
+    engine.handleActions({
+      sectionTransition: {
+        sectionId: "result",
+      },
+      updateVariable: {
+        id: "chooseA15",
+        operations: [
+          {
+            variableId: "score",
+            op: "set",
+            value: 15,
+          },
+        ],
+      },
+    });
+
+    let state = engine.selectSystemState();
+    expect(state.contexts[0].variables.score).toBe(15);
+    expect(state.contexts[0].pointers.read).toEqual({
+      sectionId: "result",
+      lineId: "line1",
+    });
+
+    engine.handleAction("rollbackByOffset", { offset: -1 });
+
+    state = engine.selectSystemState();
+    expect(state.contexts[0].variables.score).toBe(15);
+    expect(state.contexts[0].pointers.read).toEqual({
+      sectionId: "source",
+      lineId: "line1",
+    });
+    expect(state.contexts[0].rollback.timeline[0].executedActions).toEqual([
+      {
+        type: "updateVariable",
+        payload: {
+          id: "chooseA15",
+          operations: [
+            {
+              variableId: "score",
+              op: "set",
+              value: 15,
+            },
+          ],
+        },
+      },
+    ]);
+  });
 });
diff --git a/spec/system/actions/rollbackByOffset.spec.yaml b/spec/system/actions/rollbackByOffset.spec.yaml
index 53ae5669..6c5bd4fb 100644
--- a/spec/system/actions/rollbackByOffset.spec.yaml
+++ b/spec/system/actions/rollbackByOffset.spec.yaml
@@ -68,12 +68,18 @@ in:
               sectionId: "section1"
               lineId: "2"
             history: {}
-          historySequence:
-            - sectionId: "section1"
-              initialState: {}
-              lines:
-                - id: "1"
-                - id: "2"
+          rollback:
+            currentIndex: 1
+            isRestoring: false
+            replayStartIndex: 0
+            baselineVariables: {}
+            timeline:
+              - sectionId: "section1"
+                lineId: "1"
+                rollbackPolicy: "free"
+              - sectionId: "section1"
+                lineId: "2"
+                rollbackPolicy: "free"
   - {}
 out:
   projectData:
@@ -89,8 +95,19 @@ out:
       variables: {}
   global:
     isLineCompleted: true
+    dialogueUIHidden: false
+    isDialogueHistoryShowing: false
+    layeredViews: []
+    nextLineConfig:
+      manual:
+        enabled: true
+        requireLineCompleted: false
+      auto:
+        enabled: false
+      applyMode: "persistent"
     pendingEffects:
-      - name: "handleLineActions"
+      - name: "clearNextLineConfigTimer"
+      - name: "render"
   contexts:
     - variables: {}
       currentPointerMode: "read"
@@ -102,13 +119,20 @@ out:
           sectionId: null
           lineId: null
           historySequenceIndex: null
-      historySequence:
-        - sectionId: "section1"
-          initialState: {}
-          lines:
-            - id: "1"
+      rollback:
+        currentIndex: 0
+        isRestoring: false
+        replayStartIndex: 0
+        baselineVariables: {}
+        timeline:
+          - sectionId: "section1"
+            lineId: "1"
+            rollbackPolicy: "free"
+          - sectionId: "section1"
+            lineId: "2"
+            rollbackPolicy: "free"
 ---
-case: rolls back one line with offset -1 and reverts variables
+case: rolls back one line with inclusive checkpoint state
 in:
   - state:
       projectData:
@@ -135,7 +159,7 @@ in:
               scope: context
               default: 0
       global:
-        isLineCompleted: true
+        isLineCompleted: false
         pendingEffects: []
       contexts:
         - variables:
@@ -146,16 +170,22 @@ in:
               sectionId: "section1"
               lineId: "3"
             history: {}
-          historySequence:
-            - sectionId: "section1"
-              initialState:
-                score: 0
-              lines:
-                - id: "1"
-                - id: "2"
-                  updateVariableIds:
-                    - "act1"
-                - id: "3"
+          rollback:
+            currentIndex: 2
+            isRestoring: false
+            replayStartIndex: 0
+            baselineVariables:
+              score: 0
+            timeline:
+              - sectionId: "section1"
+                lineId: "1"
+                rollbackPolicy: "free"
+              - sectionId: "section1"
+                lineId: "2"
+                rollbackPolicy: "free"
+              - sectionId: "section1"
+                lineId: "3"
+                rollbackPolicy: "free"
   - offset: -1
 out:
   projectData:
@@ -183,11 +213,22 @@ out:
           default: 0
   global:
     isLineCompleted: true
+    dialogueUIHidden: false
+    isDialogueHistoryShowing: false
+    layeredViews: []
+    nextLineConfig:
+      manual:
+        enabled: true
+        requireLineCompleted: false
+      auto:
+        enabled: false
+      applyMode: "persistent"
     pendingEffects:
-      - name: "handleLineActions"
+      - name: "clearNextLineConfigTimer"
+      - name: "render"
   contexts:
     - variables:
-        score: 0
+        score: 10
       currentPointerMode: "read"
       pointers:
         read:
@@ -197,13 +238,22 @@ out:
           sectionId: null
           lineId: null
           historySequenceIndex: null
-      historySequence:
-        - sectionId: "section1"
-          initialState:
-            score: 0
-          lines:
-            - id: "1"
-            - id: "2"
+      rollback:
+        currentIndex: 1
+        isRestoring: false
+        replayStartIndex: 0
+        baselineVariables:
+          score: 0
+        timeline:
+          - sectionId: "section1"
+            lineId: "1"
+            rollbackPolicy: "free"
+          - sectionId: "section1"
+            lineId: "2"
+            rollbackPolicy: "free"
+          - sectionId: "section1"
+            lineId: "3"
+            rollbackPolicy: "free"
 ---
 case: does nothing when at first line with offset -1
 in:
@@ -234,12 +284,16 @@ in:
               sectionId: "section1"
               lineId: "1"
             history: {}
-          historySequence:
-            - sectionId: "section1"
-              initialState:
-                score: 0
-              lines:
-                - id: "1"
+          rollback:
+            currentIndex: 0
+            isRestoring: false
+            replayStartIndex: 0
+            baselineVariables:
+              score: 0
+            timeline:
+              - sectionId: "section1"
+                lineId: "1"
+                rollbackPolicy: "free"
   - offset: -1
 out:
   projectData:
@@ -268,14 +322,18 @@ out:
           sectionId: "section1"
           lineId: "1"
         history: {}
-      historySequence:
-        - sectionId: "section1"
-          initialState:
-            score: 0
-          lines:
-            - id: "1"
+      rollback:
+        currentIndex: 0
+        isRestoring: false
+        replayStartIndex: 0
+        baselineVariables:
+          score: 0
+        timeline:
+          - sectionId: "section1"
+            lineId: "1"
+            rollbackPolicy: "free"
 ---
-case: handles duplicate line entries correctly (uses last occurrence)
+case: handles duplicate checkpoints using rollback cursor
 in:
   - state:
       projectData:
@@ -295,6 +353,13 @@ in:
                               op: set
                               value: 10
                     - id: "3"
+                      actions:
+                        updateVariable:
+                          id: "act2"
+                          operations:
+                            - variableId: score
+                              op: increment
+                              value: 5
         resources:
           variables:
             score:
@@ -302,7 +367,7 @@ in:
               scope: context
               default: 0
       global:
-        isLineCompleted: true
+        isLineCompleted: false
         pendingEffects: []
       contexts:
         - variables:
@@ -313,17 +378,25 @@ in:
               sectionId: "section1"
               lineId: "2"
             history: {}
-          historySequence:
-            - sectionId: "section1"
-              initialState:
-                score: 0
-              lines:
-                - id: "1"
-                - id: "2"
-                  updateVariableIds:
-                    - "act1"
-                - id: "3"
-                - id: "2"
+          rollback:
+            currentIndex: 3
+            isRestoring: false
+            replayStartIndex: 0
+            baselineVariables:
+              score: 0
+            timeline:
+              - sectionId: "section1"
+                lineId: "1"
+                rollbackPolicy: "free"
+              - sectionId: "section1"
+                lineId: "2"
+                rollbackPolicy: "free"
+              - sectionId: "section1"
+                lineId: "3"
+                rollbackPolicy: "free"
+              - sectionId: "section1"
+                lineId: "2"
+                rollbackPolicy: "free"
   - offset: -1
 out:
   projectData:
@@ -343,6 +416,13 @@ out:
                           op: set
                           value: 10
                 - id: "3"
+                  actions:
+                    updateVariable:
+                      id: "act2"
+                      operations:
+                        - variableId: score
+                          op: increment
+                          value: 5
     resources:
       variables:
         score:
@@ -351,11 +431,22 @@ out:
           default: 0
   global:
     isLineCompleted: true
+    dialogueUIHidden: false
+    isDialogueHistoryShowing: false
+    layeredViews: []
+    nextLineConfig:
+      manual:
+        enabled: true
+        requireLineCompleted: false
+      auto:
+        enabled: false
+      applyMode: "persistent"
     pendingEffects:
-      - name: "handleLineActions"
+      - name: "clearNextLineConfigTimer"
+      - name: "render"
   contexts:
     - variables:
-        score: 10
+        score: 15
       currentPointerMode: "read"
       pointers:
         read:
@@ -365,16 +456,25 @@ out:
           sectionId: null
           lineId: null
           historySequenceIndex: null
-      historySequence:
-        - sectionId: "section1"
-          initialState:
-            score: 0
-          lines:
-            - id: "1"
-            - id: "2"
-              updateVariableIds:
-                - "act1"
-            - id: "3"
+      rollback:
+        currentIndex: 2
+        isRestoring: false
+        replayStartIndex: 0
+        baselineVariables:
+          score: 0
+        timeline:
+          - sectionId: "section1"
+            lineId: "1"
+            rollbackPolicy: "free"
+          - sectionId: "section1"
+            lineId: "2"
+            rollbackPolicy: "free"
+          - sectionId: "section1"
+            lineId: "3"
+            rollbackPolicy: "free"
+          - sectionId: "section1"
+            lineId: "2"
+            rollbackPolicy: "free"
 ---
 case: rolls back across sections using rollback timeline replay
 in:
@@ -536,3 +636,121 @@ out:
           - sectionId: "section2"
             lineId: "10"
             rollbackPolicy: "free"
+---
+case: restores nextLineConfig auto without restarting scene timer
+in:
+  - state:
+      projectData:
+        story:
+          scenes:
+            scene1:
+              sections:
+                section1:
+                  lines:
+                    - id: "1"
+                    - id: "2"
+                      actions:
+                        setNextLineConfig:
+                          auto:
+                            enabled: true
+                            trigger: "fromComplete"
+                            delay: 750
+                    - id: "3"
+        resources:
+          variables: {}
+      global:
+        isLineCompleted: false
+        nextLineConfig:
+          manual:
+            enabled: true
+            requireLineCompleted: false
+          auto:
+            enabled: false
+          applyMode: "persistent"
+        pendingEffects: []
+      contexts:
+        - variables: {}
+          currentPointerMode: "read"
+          pointers:
+            read:
+              sectionId: "section1"
+              lineId: "3"
+            history: {}
+          rollback:
+            currentIndex: 2
+            isRestoring: false
+            replayStartIndex: 0
+            baselineVariables: {}
+            timeline:
+              - sectionId: "section1"
+                lineId: "1"
+                rollbackPolicy: "free"
+              - sectionId: "section1"
+                lineId: "2"
+                rollbackPolicy: "free"
+              - sectionId: "section1"
+                lineId: "3"
+                rollbackPolicy: "free"
+  - offset: -1
+out:
+  projectData:
+    story:
+      scenes:
+        scene1:
+          sections:
+            section1:
+              lines:
+                - id: "1"
+                - id: "2"
+                  actions:
+                    setNextLineConfig:
+                      auto:
+                        enabled: true
+                        trigger: "fromComplete"
+                        delay: 750
+                - id: "3"
+    resources:
+      variables: {}
+  global:
+    isLineCompleted: true
+    dialogueUIHidden: false
+    isDialogueHistoryShowing: false
+    layeredViews: []
+    nextLineConfig:
+      manual:
+        enabled: true
+        requireLineCompleted: false
+      auto:
+        enabled: true
+        trigger: "fromComplete"
+        delay: 750
+      applyMode: "persistent"
+    pendingEffects:
+      - name: "clearNextLineConfigTimer"
+      - name: "render"
+  contexts:
+    - variables: {}
+      currentPointerMode: "read"
+      pointers:
+        read:
+          sectionId: "section1"
+          lineId: "2"
+        history:
+          sectionId: null
+          lineId: null
+          historySequenceIndex: null
+      rollback:
+        currentIndex: 1
+        isRestoring: false
+        replayStartIndex: 0
+        baselineVariables: {}
+        timeline:
+          - sectionId: "section1"
+            lineId: "1"
+            rollbackPolicy: "free"
+          - sectionId: "section1"
+            lineId: "2"
+            rollbackPolicy: "free"
+          - sectionId: "section1"
+            lineId: "3"
+            rollbackPolicy: "free"
diff --git a/spec/system/actions/rollbackToLine.spec.yaml b/spec/system/actions/rollbackToLine.spec.yaml
index 9e767c29..2ee0ab96 100644
--- a/spec/system/actions/rollbackToLine.spec.yaml
+++ b/spec/system/actions/rollbackToLine.spec.yaml
@@ -5,7 +5,7 @@ suites: [rollbackToLine]
 suite: rollbackToLine
 exportName: rollbackToLine
 ---
-case: resets to initialState before replay
+case: restores target checkpoint state inclusively
 in:
   - state:
       projectData:
@@ -14,7 +14,25 @@ in:
             scene1:
               sections:
                 section1:
-                  lines: []
+                  lines:
+                    - id: "1"
+                    - id: "2"
+                      actions:
+                        updateVariable:
+                          id: "act1"
+                          operations:
+                            - variableId: score
+                              op: set
+                              value: 15
+                    - id: "3"
+                      actions:
+                        updateVariable:
+                          id: "act2"
+                          operations:
+                            - variableId: score
+                              op: increment
+                              value: 10
+                    - id: "4"
         resources:
           variables:
             score:
@@ -22,11 +40,11 @@ in:
               scope: context
               default: 0
       global:
-        isLineCompleted: true
+        isLineCompleted: false
         pendingEffects: []
       contexts:
         - variables:
-            score: 999
+            score: 25
           currentPointerMode: "history"
           pointers:
             read:
@@ -35,17 +53,27 @@ in:
             history:
               sectionId: "section1"
               lineId: "2"
-          historySequence:
-            - sectionId: "section1"
-              initialState:
-                score: 0
-              lines:
-                - id: "1"
-                - id: "2"
-                - id: "3"
-                - id: "4"
+          rollback:
+            currentIndex: 3
+            isRestoring: false
+            replayStartIndex: 0
+            baselineVariables:
+              score: 0
+            timeline:
+              - sectionId: "section1"
+                lineId: "1"
+                rollbackPolicy: "free"
+              - sectionId: "section1"
+                lineId: "2"
+                rollbackPolicy: "free"
+              - sectionId: "section1"
+                lineId: "3"
+                rollbackPolicy: "free"
+              - sectionId: "section1"
+                lineId: "4"
+                rollbackPolicy: "free"
   - sectionId: "section1"
-    lineId: "1"
+    lineId: "3"
 out:
   projectData:
     story:
@@ -53,7 +81,25 @@ out:
         scene1:
           sections:
             section1:
-              lines: []
+              lines:
+                - id: "1"
+                - id: "2"
+                  actions:
+                    updateVariable:
+                      id: "act1"
+                      operations:
+                        - variableId: score
+                          op: set
+                          value: 15
+                - id: "3"
+                  actions:
+                    updateVariable:
+                      id: "act2"
+                      operations:
+                        - variableId: score
+                          op: increment
+                          value: 10
+                - id: "4"
     resources:
       variables:
         score:
@@ -62,28 +108,52 @@ out:
           default: 0
   global:
     isLineCompleted: true
+    dialogueUIHidden: false
+    isDialogueHistoryShowing: false
+    layeredViews: []
+    nextLineConfig:
+      manual:
+        enabled: true
+        requireLineCompleted: false
+      auto:
+        enabled: false
+      applyMode: "persistent"
     pendingEffects:
-      - name: "handleLineActions"
+      - name: "clearNextLineConfigTimer"
+      - name: "render"
   contexts:
     - variables:
-        score: 0
+        score: 25
       currentPointerMode: "read"
       pointers:
         read:
           sectionId: "section1"
-          lineId: "1"
+          lineId: "3"
         history:
           sectionId: null
           lineId: null
           historySequenceIndex: null
-      historySequence:
-        - sectionId: "section1"
-          initialState:
-            score: 0
-          lines:
-            - id: "1"
+      rollback:
+        currentIndex: 2
+        isRestoring: false
+        replayStartIndex: 0
+        baselineVariables:
+          score: 0
+        timeline:
+          - sectionId: "section1"
+            lineId: "1"
+            rollbackPolicy: "free"
+          - sectionId: "section1"
+            lineId: "2"
+            rollbackPolicy: "free"
+          - sectionId: "section1"
+            lineId: "3"
+            rollbackPolicy: "free"
+          - sectionId: "section1"
+            lineId: "4"
+            rollbackPolicy: "free"
 ---
-case: replays actions forward to line before target
+case: rolls back directly across sections using rollback timeline
 in:
   - state:
       projectData:
@@ -97,20 +167,21 @@ in:
                     - id: "2"
                       actions:
                         updateVariable:
-                          id: "act1"
+                          id: "set-score-10"
                           operations:
                             - variableId: score
                               op: set
-                              value: 15
-                    - id: "3"
+                              value: 10
+                section2:
+                  lines:
+                    - id: "10"
                       actions:
                         updateVariable:
-                          id: "act2"
+                          id: "add-score-5"
                           operations:
                             - variableId: score
-                              op: increment
-                              value: 10
-                    - id: "4"
+                              op: add
+                              value: 5
         resources:
           variables:
             score:
@@ -118,34 +189,37 @@ in:
               scope: context
               default: 0
       global:
-        isLineCompleted: true
+        isLineCompleted: false
         pendingEffects: []
       contexts:
         - variables:
-            score: 25
+            score: 15
           currentPointerMode: "history"
           pointers:
             read:
-              sectionId: "section1"
-              lineId: "4"
+              sectionId: "section2"
+              lineId: "10"
             history:
-              sectionId: "section1"
-              lineId: "2"
-          historySequence:
-            - sectionId: "section1"
-              initialState:
-                score: 0
-              lines:
-                - id: "1"
-                - id: "2"
-                  updateVariableIds:
-                    - "act1"
-                - id: "3"
-                  updateVariableIds:
-                    - "act2"
-                - id: "4"
+              sectionId: "section2"
+              lineId: "10"
+          rollback:
+            currentIndex: 2
+            isRestoring: false
+            replayStartIndex: 0
+            baselineVariables:
+              score: 0
+            timeline:
+              - sectionId: "section1"
+                lineId: "1"
+                rollbackPolicy: "free"
+              - sectionId: "section1"
+                lineId: "2"
+                rollbackPolicy: "free"
+              - sectionId: "section2"
+                lineId: "10"
+                rollbackPolicy: "free"
   - sectionId: "section1"
-    lineId: "3"
+    lineId: "2"
 out:
   projectData:
     story:
@@ -158,20 +232,21 @@ out:
                 - id: "2"
                   actions:
                     updateVariable:
-                      id: "act1"
+                      id: "set-score-10"
                       operations:
                         - variableId: score
                           op: set
-                          value: 15
-                - id: "3"
+                          value: 10
+            section2:
+              lines:
+                - id: "10"
                   actions:
                     updateVariable:
-                      id: "act2"
+                      id: "add-score-5"
                       operations:
                         - variableId: score
-                          op: increment
-                          value: 10
-                - id: "4"
+                          op: add
+                          value: 5
     resources:
       variables:
         score:
@@ -180,32 +255,49 @@ out:
           default: 0
   global:
     isLineCompleted: true
+    dialogueUIHidden: false
+    isDialogueHistoryShowing: false
+    layeredViews: []
+    nextLineConfig:
+      manual:
+        enabled: true
+        requireLineCompleted: false
+      auto:
+        enabled: false
+      applyMode: "persistent"
     pendingEffects:
-      - name: "handleLineActions"
+      - name: "clearNextLineConfigTimer"
+      - name: "render"
   contexts:
     - variables:
-        score: 15
+        score: 10
       currentPointerMode: "read"
       pointers:
         read:
           sectionId: "section1"
-          lineId: "3"
+          lineId: "2"
         history:
           sectionId: null
           lineId: null
           historySequenceIndex: null
-      historySequence:
-        - sectionId: "section1"
-          initialState:
-            score: 0
-          lines:
-            - id: "1"
-            - id: "2"
-              updateVariableIds:
-                - "act1"
-            - id: "3"
+      rollback:
+        currentIndex: 1
+        isRestoring: false
+        replayStartIndex: 0
+        baselineVariables:
+          score: 0
+        timeline:
+          - sectionId: "section1"
+            lineId: "1"
+            rollbackPolicy: "free"
+          - sectionId: "section1"
+            lineId: "2"
+            rollbackPolicy: "free"
+          - sectionId: "section2"
+            lineId: "10"
+            rollbackPolicy: "free"
 ---
-case: throws error for invalid lineId
+case: throws error for invalid lineId in rollback timeline
 in:
   - state:
       projectData:
@@ -222,21 +314,25 @@ in:
           pointers:
             read:
               sectionId: "section1"
-              lineId: "3"
-            history:
-              sectionId: "section1"
-              lineId: "1"
-          historySequence:
-            - sectionId: "section1"
-              initialState: {}
-              lines:
-                - id: "1"
-                - id: "2"
+              lineId: "2"
+            history: {}
+          rollback:
+            currentIndex: 1
+            isRestoring: false
+            replayStartIndex: 0
+            baselineVariables: {}
+            timeline:
+              - sectionId: "section1"
+                lineId: "1"
+                rollbackPolicy: "free"
+              - sectionId: "section1"
+                lineId: "2"
+                rollbackPolicy: "free"
   - sectionId: "section1"
     lineId: "nonExistentLine"
-throws: "Line nonExistentLine not found in section section1 history"
+throws: "Line nonExistentLine not found in section section1 rollback timeline"
 ---
-case: handles multiple operations in single action
+case: handles multiple operations in a rollbackable action
 in:
   - state:
       projectData:
@@ -266,31 +362,35 @@ in:
               scope: context
               default: 0
       global:
-        isLineCompleted: true
+        isLineCompleted: false
         pendingEffects: []
       contexts:
         - variables:
-            score: 100
+            score: 15
           currentPointerMode: "history"
           pointers:
             read:
               sectionId: "section1"
               lineId: "3"
-            history:
-              sectionId: "section1"
-              lineId: "1"
-          historySequence:
-            - sectionId: "section1"
-              initialState:
-                score: 0
-              lines:
-                - id: "1"
-                - id: "2"
-                  updateVariableIds:
-                    - "act1"
-                - id: "3"
+            history: {}
+          rollback:
+            currentIndex: 2
+            isRestoring: false
+            replayStartIndex: 0
+            baselineVariables:
+              score: 0
+            timeline:
+              - sectionId: "section1"
+                lineId: "1"
+                rollbackPolicy: "free"
+              - sectionId: "section1"
+                lineId: "2"
+                rollbackPolicy: "free"
+              - sectionId: "section1"
+                lineId: "3"
+                rollbackPolicy: "free"
   - sectionId: "section1"
-    lineId: "3"
+    lineId: "2"
 out:
   projectData:
     story:
@@ -320,8 +420,19 @@ out:
           default: 0
   global:
     isLineCompleted: true
+    dialogueUIHidden: false
+    isDialogueHistoryShowing: false
+    layeredViews: []
+    nextLineConfig:
+      manual:
+        enabled: true
+        requireLineCompleted: false
+      auto:
+        enabled: false
+      applyMode: "persistent"
     pendingEffects:
-      - name: "handleLineActions"
+      - name: "clearNextLineConfigTimer"
+      - name: "render"
   contexts:
     - variables:
         score: 15
@@ -329,23 +440,29 @@ out:
       pointers:
         read:
           sectionId: "section1"
-          lineId: "3"
+          lineId: "2"
         history:
           sectionId: null
           lineId: null
           historySequenceIndex: null
-      historySequence:
-        - sectionId: "section1"
-          initialState:
-            score: 0
-          lines:
-            - id: "1"
-            - id: "2"
-              updateVariableIds:
-                - "act1"
-            - id: "3"
+      rollback:
+        currentIndex: 1
+        isRestoring: false
+        replayStartIndex: 0
+        baselineVariables:
+          score: 0
+        timeline:
+          - sectionId: "section1"
+            lineId: "1"
+            rollbackPolicy: "free"
+          - sectionId: "section1"
+            lineId: "2"
+            rollbackPolicy: "free"
+          - sectionId: "section1"
+            lineId: "3"
+            rollbackPolicy: "free"
 ---
-case: rollback to first line resets to initialState only (no replay)
+case: rollback to first line resets to baseline when first checkpoint has no rollbackable actions
 in:
   - state:
       projectData:
@@ -371,7 +488,7 @@ in:
               scope: context
               default: 0
       global:
-        isLineCompleted: true
+        isLineCompleted: false
         pendingEffects: []
       contexts:
         - variables:
@@ -381,18 +498,20 @@ in:
             read:
               sectionId: "section1"
               lineId: "2"
-            history:
-              sectionId: "section1"
-              lineId: "1"
-          historySequence:
-            - sectionId: "section1"
-              initialState:
-                score: 10
-              lines:
-                - id: "1"
-                - id: "2"
-                  updateVariableIds:
-                    - "act1"
+            history: {}
+          rollback:
+            currentIndex: 1
+            isRestoring: false
+            replayStartIndex: 0
+            baselineVariables:
+              score: 10
+            timeline:
+              - sectionId: "section1"
+                lineId: "1"
+                rollbackPolicy: "free"
+              - sectionId: "section1"
+                lineId: "2"
+                rollbackPolicy: "free"
   - sectionId: "section1"
     lineId: "1"
 out:
@@ -420,8 +539,19 @@ out:
           default: 0
   global:
     isLineCompleted: true
+    dialogueUIHidden: false
+    isDialogueHistoryShowing: false
+    layeredViews: []
+    nextLineConfig:
+      manual:
+        enabled: true
+        requireLineCompleted: false
+      auto:
+        enabled: false
+      applyMode: "persistent"
     pendingEffects:
-      - name: "handleLineActions"
+      - name: "clearNextLineConfigTimer"
+      - name: "render"
   contexts:
     - variables:
         score: 10
@@ -434,14 +564,21 @@ out:
           sectionId: null
           lineId: null
           historySequenceIndex: null
-      historySequence:
-        - sectionId: "section1"
-          initialState:
-            score: 10
-          lines:
-            - id: "1"
+      rollback:
+        currentIndex: 0
+        isRestoring: false
+        replayStartIndex: 0
+        baselineVariables:
+          score: 10
+        timeline:
+          - sectionId: "section1"
+            lineId: "1"
+            rollbackPolicy: "free"
+          - sectionId: "section1"
+            lineId: "2"
+            rollbackPolicy: "free"
 ---
-case: global variables are NOT replayed during rollback
+case: global variables are not replayed during rollback
 in:
   - state:
       projectData:
@@ -470,7 +607,7 @@ in:
       global:
         variables:
           volume: 100
-        isLineCompleted: true
+        isLineCompleted: false
         pendingEffects: []
       contexts:
         - variables: {}
@@ -480,17 +617,23 @@ in:
               sectionId: "section1"
               lineId: "3"
             history: {}
-          historySequence:
-            - sectionId: "section1"
-              initialState: {}
-              lines:
-                - id: "1"
-                - id: "2"
-                  updateVariableIds:
-                    - "globalAct"
-                - id: "3"
+          rollback:
+            currentIndex: 2
+            isRestoring: false
+            replayStartIndex: 0
+            baselineVariables: {}
+            timeline:
+              - sectionId: "section1"
+                lineId: "1"
+                rollbackPolicy: "free"
+              - sectionId: "section1"
+                lineId: "2"
+                rollbackPolicy: "free"
+              - sectionId: "section1"
+                lineId: "3"
+                rollbackPolicy: "free"
   - sectionId: "section1"
-    lineId: "3"
+    lineId: "2"
 out:
   projectData:
     story:
@@ -519,25 +662,42 @@ out:
     variables:
       volume: 100
     isLineCompleted: true
+    dialogueUIHidden: false
+    isDialogueHistoryShowing: false
+    layeredViews: []
+    nextLineConfig:
+      manual:
+        enabled: true
+        requireLineCompleted: false
+      auto:
+        enabled: false
+      applyMode: "persistent"
     pendingEffects:
-      - name: "handleLineActions"
+      - name: "clearNextLineConfigTimer"
+      - name: "render"
   contexts:
     - variables: {}
       currentPointerMode: "read"
       pointers:
         read:
           sectionId: "section1"
-          lineId: "3"
+          lineId: "2"
         history:
           sectionId: null
           lineId: null
           historySequenceIndex: null
-      historySequence:
-        - sectionId: "section1"
-          initialState: {}
-          lines:
-            - id: "1"
-            - id: "2"
-              updateVariableIds:
-                - "globalAct"
-            - id: "3"
+      rollback:
+        currentIndex: 1
+        isRestoring: false
+        replayStartIndex: 0
+        baselineVariables: {}
+        timeline:
+          - sectionId: "section1"
+            lineId: "1"
+            rollbackPolicy: "free"
+          - sectionId: "section1"
+            lineId: "2"
+            rollbackPolicy: "free"
+          - sectionId: "section1"
+            lineId: "3"
+            rollbackPolicy: "free"
diff --git a/spec/system/actions/setNextLineConfig.spec.yaml b/spec/system/actions/setNextLineConfig.spec.yaml
index 584b83f1..9026bd69 100644
--- a/spec/system/actions/setNextLineConfig.spec.yaml
+++ b/spec/system/actions/setNextLineConfig.spec.yaml
@@ -356,3 +356,37 @@ out:
     pendingEffects:
       - name: "clearNextLineConfigTimer"
       - name: "render"
+---
+case: suppresses timer side effects during rollback restore
+in:
+  - state:
+      global:
+        isLineCompleted: true
+        nextLineConfig:
+          manual:
+            enabled: true
+          auto:
+            enabled: false
+        pendingEffects: []
+      contexts:
+        - rollback:
+            isRestoring: true
+  - auto:
+      enabled: true
+      trigger: "fromComplete"
+      delay: 2000
+out:
+  global:
+    isLineCompleted: true
+    nextLineConfig:
+      manual:
+        enabled: true
+      auto:
+        enabled: true
+        trigger: "fromComplete"
+        delay: 2000
+    pendingEffects:
+      - name: "render"
+  contexts:
+    - rollback:
+        isRestoring: true
diff --git a/spec/system/selectors/selectLineIdByOffset.spec.yaml b/spec/system/selectors/selectLineIdByOffset.spec.yaml
index 352e954a..084abac9 100644
--- a/spec/system/selectors/selectLineIdByOffset.spec.yaml
+++ b/spec/system/selectors/selectLineIdByOffset.spec.yaml
@@ -1,14 +1,11 @@
 file: "../../../src/stores/system.store.js"
 group: systemStore selectors
-suites:
-  [
-    selectLineIdByOffset,
-  ]
+suites: [selectLineIdByOffset]
 ---
 suite: selectLineIdByOffset
 exportName: selectLineIdByOffset
 ---
-case: returns previous line with offset -1
+case: returns previous line from rollback timeline
 in:
   - state:
       global: {}
@@ -18,19 +15,27 @@ in:
             read:
               sectionId: "section1"
               lineId: "3"
-          historySequence:
-            - sectionId: "section1"
-              initialState: {}
-              lines:
-                - id: "1"
-                - id: "2"
-                - id: "3"
+          rollback:
+            currentIndex: 2
+            isRestoring: false
+            replayStartIndex: 0
+            baselineVariables: {}
+            timeline:
+              - sectionId: "section1"
+                lineId: "1"
+                rollbackPolicy: "free"
+              - sectionId: "section1"
+                lineId: "2"
+                rollbackPolicy: "free"
+              - sectionId: "section1"
+                lineId: "3"
+                rollbackPolicy: "free"
   - offset: -1
 out:
   sectionId: "section1"
   lineId: "2"
 ---
-case: returns null when at first line with offset -1
+case: returns null when at first rollback checkpoint with offset -1
 in:
   - state:
       global: {}
@@ -40,15 +45,19 @@ in:
             read:
               sectionId: "section1"
               lineId: "1"
-          historySequence:
-            - sectionId: "section1"
-              initialState: {}
-              lines:
-                - id: "1"
+          rollback:
+            currentIndex: 0
+            isRestoring: false
+            replayStartIndex: 0
+            baselineVariables: {}
+            timeline:
+              - sectionId: "section1"
+                lineId: "1"
+                rollbackPolicy: "free"
   - offset: -1
 out: null
 ---
-case: handles duplicate line entries after backtracking (findLastIndex behavior)
+case: handles duplicate checkpoints after backtracking using rollback cursor
 in:
   - state:
       global: {}
@@ -58,14 +67,24 @@ in:
             read:
               sectionId: "section1"
               lineId: "2"
-          historySequence:
-            - sectionId: "section1"
-              initialState: {}
-              lines:
-                - id: "1"
-                - id: "2"
-                - id: "3"
-                - id: "2"
+          rollback:
+            currentIndex: 3
+            isRestoring: false
+            replayStartIndex: 0
+            baselineVariables: {}
+            timeline:
+              - sectionId: "section1"
+                lineId: "1"
+                rollbackPolicy: "free"
+              - sectionId: "section1"
+                lineId: "2"
+                rollbackPolicy: "free"
+              - sectionId: "section1"
+                lineId: "3"
+                rollbackPolicy: "free"
+              - sectionId: "section1"
+                lineId: "2"
+                rollbackPolicy: "free"
   - offset: -1
 out:
   sectionId: "section1"
diff --git a/spec/systemStore.rollbackDraftSafety.test.js b/spec/systemStore.rollbackDraftSafety.test.js
index 3e3f329e..4af94dbd 100644
--- a/spec/systemStore.rollbackDraftSafety.test.js
+++ b/spec/systemStore.rollbackDraftSafety.test.js
@@ -4,6 +4,8 @@ import {
   loadSaveSlot,
   rollbackByOffset,
   saveSaveSlot,
+  sectionTransition,
+  updateVariable,
 } from "../src/stores/system.store.js";
 
 const createProjectData = () => ({
@@ -58,6 +60,76 @@ const createProjectData = () => ({
   },
 });
 
+const createInvalidRollbackProjectData = () => ({
+  story: {
+    initialSceneId: "scene1",
+    scenes: {
+      scene1: {
+        initialSectionId: "section1",
+        sections: {
+          section1: {
+            lines: [
+              { id: "1" },
+              {
+                id: "2",
+                actions: {
+                  updateVariable: {
+                    id: "invalid-score-toggle",
+                    operations: [
+                      {
+                        variableId: "score",
+                        op: "toggle",
+                      },
+                    ],
+                  },
+                },
+              },
+              { id: "3" },
+            ],
+          },
+        },
+      },
+    },
+  },
+  resources: {
+    variables: {
+      score: {
+        type: "number",
+        scope: "context",
+        default: 0,
+      },
+    },
+  },
+});
+
+const createEventDrivenRollbackProjectData = () => ({
+  story: {
+    initialSceneId: "scene1",
+    scenes: {
+      scene1: {
+        initialSectionId: "section1",
+        sections: {
+          section1: {
+            lines: [{ id: "1" }, { id: "2" }],
+          },
+          section2: {
+            lines: [{ id: "10" }],
+          },
+        },
+      },
+    },
+  },
+  resources: {
+    variables: {
+      score: {
+        type: "number",
+        scope: "context",
+        default: 0,
+      },
+    },
+  },
+});
+
 describe("system.store rollback/save draft safety", () => {
   it("saveSaveSlot does not throw when cloning live draft state", () => {
     vi.spyOn(Date, "now").mockReturnValue(1700000000000);
@@ -108,8 +180,9 @@ describe("system.store rollback/save draft safety", () => {
       saveSaveSlot({ state: draft }, { slot: 1, thumbnailImage: null });
     });
 
-    expect(nextState.global.saveSlots["1"]?.state?.contexts?.[0]?.rollback)
-      .toEqual(baseState.contexts[0].rollback);
+    expect(
+      nextState.global.saveSlots["1"]?.state?.contexts?.[0]?.rollback,
+    ).toEqual(baseState.contexts[0].rollback);
     vi.restoreAllMocks();
   });
 
@@ -143,7 +216,7 @@ describe("system.store rollback/save draft safety", () => {
     const baseState = {
       global: {
         saveSlots: {
-          "1": {
+          1: {
             slotKey: "1",
             date: 1700000000000,
             image: null,
@@ -279,4 +352,164 @@ describe("system.store rollback/save draft safety", () => {
       applyMode: "persistent",
     });
   });
+
+  it("rollbackByOffset replays event-driven checkpoint actions on the source line", () => {
+    const state = {
+      projectData: createEventDrivenRollbackProjectData(),
+      global: {
+        autoMode: false,
+        skipMode: false,
+        isLineCompleted: false,
+        dialogueUIHidden: false,
+        isDialogueHistoryShowing: false,
+        nextLineConfig: {
+          manual: {
+            enabled: true,
+            requireLineCompleted: false,
+          },
+          auto: {
+            enabled: false,
+          },
+          applyMode: "persistent",
+        },
+        layeredViews: [],
+        pendingEffects: [],
+        variables: {},
+      },
+      contexts: [
+        {
+          variables: {
+            score: 0,
+          },
+          currentPointerMode: "read",
+          pointers: {
+            read: { sectionId: "section1", lineId: "2" },
+            history: {},
+          },
+          rollback: {
+            currentIndex: 1,
+            isRestoring: false,
+            replayStartIndex: 0,
+            baselineVariables: {
+              score: 0,
+            },
+            timeline: [
+              {
+                sectionId: "section1",
+                lineId: "1",
+                rollbackPolicy: "free",
+              },
+              {
+                sectionId: "section1",
+                lineId: "2",
+                rollbackPolicy: "free",
+              },
+            ],
+          },
+        },
+      ],
+    };
+
+    updateVariable(
+      { state },
+      {
+        id: "choiceScore15",
+        operations: [
+          {
+            variableId: "score",
+            op: "set",
+            value: 15,
+          },
+        ],
+      },
+    );
+    sectionTransition({ state }, { sectionId: "section2" });
+    rollbackByOffset({ state }, { offset: -1 });
+
+    expect(state.contexts[0].variables.score).toBe(15);
+    expect(state.contexts[0].pointers.read).toEqual({
+      sectionId: "section1",
+      lineId: "2",
+    });
+    expect(state.contexts[0].rollback.timeline[1].executedActions).toEqual([
+      {
+        type: "updateVariable",
+        payload: {
+          id: "choiceScore15",
+          operations: [
+            {
+              variableId: "score",
+              op: "set",
+              value: 15,
+            },
+          ],
+        },
+      },
+    ]);
+  });
+
+  it("rollbackByOffset clears the restoring guard when replay throws", () => {
+    const state = {
+      projectData: createInvalidRollbackProjectData(),
+      global: {
+        isLineCompleted: false,
+        dialogueUIHidden: false,
+        isDialogueHistoryShowing: false,
+        nextLineConfig: {
+          manual: {
+            enabled: true,
+            requireLineCompleted: false,
+          },
+          auto: {
+            enabled: false,
+          },
+          applyMode: "persistent",
+        },
+        layeredViews: [],
+        pendingEffects: [],
+      },
+      contexts: [
+        {
+          variables: {
+            score: 0,
+          },
+          currentPointerMode: "read",
+          pointers: {
+            read: { sectionId: "section1", lineId: "3" },
+            history: {},
+          },
+          rollback: {
+            currentIndex: 2,
+            isRestoring: false,
+            replayStartIndex: 0,
+            baselineVariables: {
+              score: 0,
+            },
+            timeline: [
+              {
+                sectionId: "section1",
+                lineId: "1",
+                rollbackPolicy: "free",
+              },
+              {
+                sectionId: "section1",
+                lineId: "2",
+                rollbackPolicy: "free",
+              },
+              {
+                sectionId: "section1",
+                lineId: "3",
+                rollbackPolicy: "free",
+              },
+            ],
+          },
+        },
+      ],
+    };
+
+    expect(() => rollbackByOffset({ state }, { offset: -1 })).toThrow(
+      'Operation "toggle" is not valid for variable "score" of type "number". Valid operations: set, increment, decrement, multiply, divide',
+    );
+    expect(state.contexts[0].rollback.isRestoring).toBe(false);
+  });
 });
diff --git a/src/RouteEngine.js b/src/RouteEngine.js
index 7d1bc544..7767fadd 100644
--- a/src/RouteEngine.js
+++ b/src/RouteEngine.js
@@ -91,9 +91,14 @@ export default function createRouteEngine(options) {
   const handleActions = (actions, eventContext) => {
     const context = buildActionTemplateContext(eventContext);
     const processedActions = processActionTemplates(actions, context);
-    Object.entries(processedActions).forEach(([actionType, payload]) => {
-      handleAction(actionType, payload);
-    });
+    _systemStore.beginRollbackActionBatch({});
+    try {
+      Object.entries(processedActions).forEach(([actionType, payload]) => {
+        handleAction(actionType, payload);
+      });
+    } finally {
+      _systemStore.endRollbackActionBatch({});
+    }
   };
 
   const handleLineActions = () => {
diff --git a/src/stores/constructRenderState.js b/src/stores/constructRenderState.js
index 45af997a..7e5e9189 100644
--- a/src/stores/constructRenderState.js
+++ b/src/stores/constructRenderState.js
@@ -1710,7 +1710,6 @@ export const addControl = (
     skipMode,
     canRollback,
     saveSlots = [],
-    isLineCompleted,
     skipTransitionsAndAnimations,
   },
 ) => {
diff --git a/src/stores/system.store.js b/src/stores/system.store.js
index 22ada45a..417e9b0d 100644
--- a/src/stores/system.store.js
+++ b/src/stores/system.store.js
@@ -50,6 +50,8 @@ const cloneStateValue = (value) => {
   return structuredClone(source);
 };
 
+const rollbackActionBatchStack = [];
+
 const createRollbackCheckpoint = ({ sectionId, lineId, rollbackPolicy }) => ({
   sectionId,
   lineId,
@@ -143,6 +145,146 @@ const appendRollbackCheckpoint = (state, payload) => {
   rollback.currentIndex = rollback.timeline.length - 1;
 };
 
+const getCurrentRollbackCheckpoint = (state) => {
+  const lastContext = state.contexts?.[state.contexts.length - 1];
+  const rollback = lastContext?.rollback;
+
+  if (
+    !rollback ||
+    rollback.isRestoring ||
+    !Array.isArray(rollback.timeline) ||
+    typeof rollback.currentIndex !== "number"
+  ) {
+    return null;
+  }
+
+  const activeBatch =
+    rollbackActionBatchStack[rollbackActionBatchStack.length - 1];
+  const checkpointIndex =
+    typeof activeBatch?.checkpointIndex === "number"
+      ? activeBatch.checkpointIndex
+      : rollback.currentIndex;
+
+  if (checkpointIndex < 0 || checkpointIndex >= rollback.timeline.length) {
+    return null;
+  }
+
+  if (
+    typeof activeBatch?.checkpointIndex !== "number" &&
+    checkpointIndex < rollback.timeline.length - 1
+  ) {
+    rollback.timeline = rollback.timeline.slice(0, checkpointIndex + 1);
+  }
+
+  return rollback.timeline[checkpointIndex] ?? null;
+};
+
+export const beginRollbackActionBatch = ({ state }) => {
+  const lastContext = state.contexts?.[state.contexts.length - 1];
+  const rollback = lastContext?.rollback;
+  if (
+    !rollback ||
+    rollback.isRestoring ||
+    !Array.isArray(rollback.timeline) ||
+    typeof rollback.currentIndex !== "number" ||
+    rollback.currentIndex < 0 ||
+    rollback.currentIndex >= rollback.timeline.length
+  ) {
+    rollbackActionBatchStack.push({ checkpointIndex: null });
+    return state;
+  }
+
+  if (rollback.currentIndex < rollback.timeline.length - 1) {
+    rollback.timeline = rollback.timeline.slice(0, rollback.currentIndex + 1);
+  }
+
+  rollbackActionBatchStack.push({
+    checkpointIndex: rollback.currentIndex,
+  });
+  return state;
+};
+
+export const endRollbackActionBatch = ({ state }) => {
+  rollbackActionBatchStack.pop();
+  return state;
+};
+
+const recordRollbackAction = (state, actionType, payload) => {
+  const checkpoint = getCurrentRollbackCheckpoint(state);
+  if (!checkpoint) {
+    return;
+  }
+
+  if (!Array.isArray(checkpoint.executedActions)) {
+    checkpoint.executedActions = [];
+  }
+
+  checkpoint.executedActions.push({
+    type: actionType,
+    payload: cloneStateValue(payload),
+  });
+};
+
+const applyRollbackCheckpointUpdateVariable = (state, payload) => {
+  const lastContext = state.contexts?.[state.contexts.length - 1];
+  if (!lastContext) {
+    return;
+  }
+
+  const operations = payload?.operations ?? [];
+  for (const { variableId, op, value } of operations) {
+    const variableConfig = state.projectData.resources?.variables?.[variableId];
+    const scope = variableConfig?.scope;
+    const type = variableConfig?.type;
+
+    validateVariableScope(scope, variableId);
+    validateVariableOperation(type, op, variableId);
+
+    if (scope === "context") {
+      lastContext.variables[variableId] = applyVariableOperation(
+        lastContext.variables[variableId],
+        op,
+        value,
+      );
+    }
+  }
+};
+
+const replayRecordedRollbackActions = (state, checkpoint) => {
+  if (!Array.isArray(checkpoint?.executedActions)) {
+    return false;
+  }
+
+  const restorableActions = {
+    showDialogueUI,
+    hideDialogueUI,
+    toggleDialogueUI,
+    showDialogueHistory,
+    hideDialogueHistory,
+    setNextLineConfig,
+    pushLayeredView,
+    popLayeredView,
+    replaceLastLayeredView,
+    clearLayeredViews,
+  };
+
+  checkpoint.executedActions.forEach(({ type, payload }) => {
+    if (type === "updateVariable") {
+      applyRollbackCheckpointUpdateVariable(state, payload);
+      return;
+    }
+
+    const action = restorableActions[type];
+    if (!action) {
+      return;
+    }
+
+    action({ state }, payload);
+  });
+
+  return true;
+};
+
 const applyRollbackableLineActions = (state, payload) => {
   const { sectionId, lineId } = payload;
   const section = selectSection({ state }, { sectionId });
@@ -236,45 +378,49 @@ const restoreRollbackCheckpoint = (state, checkpointIndex) => {
   rollback.isRestoring = true;
   rollback.currentIndex = checkpointIndex;
 
-  lastContext.variables = cloneStateValue(rollback.baselineVariables ?? {});
-  state.global.dialogueUIHidden = false;
-  state.global.isDialogueHistoryShowing = false;
-  state.global.nextLineConfig = cloneStateValue(DEFAULT_NEXT_LINE_CONFIG);
-  state.global.layeredViews = [];
-  state.global.isLineCompleted = true;
+  try {
+    lastContext.variables = cloneStateValue(rollback.baselineVariables ?? {});
+    state.global.dialogueUIHidden = false;
+    state.global.isDialogueHistoryShowing = false;
+    state.global.nextLineConfig = cloneStateValue(DEFAULT_NEXT_LINE_CONFIG);
+    state.global.layeredViews = [];
+    state.global.isLineCompleted = true;
 
-  const replayStartIndex = rollback.replayStartIndex ?? 0;
-  for (let i = replayStartIndex; i <= checkpointIndex; i++) {
-    if (i > replayStartIndex) {
-      resetNextLineConfigIfSingleLine(state);
+    const replayStartIndex = rollback.replayStartIndex ?? 0;
+    for (let i = replayStartIndex; i <= checkpointIndex; i++) {
+      if (i > replayStartIndex) {
+        resetNextLineConfigIfSingleLine(state);
+      }
+      if (!replayRecordedRollbackActions(state, rollback.timeline[i])) {
+        applyRollbackableLineActions(state, rollback.timeline[i]);
+        applyRollbackRestorableLineActions(state, rollback.timeline[i]);
+      }
     }
-    applyRollbackableLineActions(state, rollback.timeline[i]);
-    applyRollbackRestorableLineActions(state, rollback.timeline[i]);
-  }
-
-  lastContext.pointers.read = {
-    sectionId: checkpoint.sectionId,
-    lineId: checkpoint.lineId,
-  };
 
-  lastContext.currentPointerMode = "read";
-  if (lastContext.pointers?.history) {
-    lastContext.pointers.history = {
-      sectionId: null,
-      lineId: null,
-      historySequenceIndex: null,
+    lastContext.pointers.read = {
+      sectionId: checkpoint.sectionId,
+      lineId: checkpoint.lineId,
     };
-  }
 
-  rollback.isRestoring = false;
+    lastContext.currentPointerMode = "read";
+    if (lastContext.pointers?.history) {
+      lastContext.pointers.history = {
+        sectionId: null,
+        lineId: null,
+        historySequenceIndex: null,
+      };
+    }
 
-  state.global.pendingEffects = state.global.pendingEffects.filter(
-    (effect) => effect?.name !== "render",
-  );
+    state.global.pendingEffects = state.global.pendingEffects.filter(
+      (effect) => effect?.name !== "render",
+    );
 
-  state.global.pendingEffects.push({
-    name: "render",
-  });
+    state.global.pendingEffects.push({
+      name: "render",
+    });
+  } finally {
+    rollback.isRestoring = false;
+  }
 
   return state;
 };
@@ -838,12 +984,14 @@ export const selectRenderState = ({ state }) => {
 export const pushLayeredView = ({ state }, payload) => {
   state.global.layeredViews.push(payload);
   state.global.pendingEffects.push({ name: "render" });
+  recordRollbackAction(state, "pushLayeredView", payload);
   return state;
 };
 
 export const popLayeredView = ({ state }) => {
   state.global.layeredViews.pop();
   state.global.pendingEffects.push({ name: "render" });
+  recordRollbackAction(state, "popLayeredView", undefined);
   return state;
 };
 
@@ -852,12 +1000,14 @@ export const replaceLastLayeredView = ({ state }, payload) => {
     state.global.layeredViews[state.global.layeredViews.length - 1] = payload;
   }
   state.global.pendingEffects.push({ name: "render" });
+  recordRollbackAction(state, "replaceLastLayeredView", payload);
   return state;
 };
 
 export const clearLayeredViews = ({ state }) => {
   state.global.layeredViews = [];
   state.global.pendingEffects.push({ name: "render" });
+  recordRollbackAction(state, "clearLayeredViews", undefined);
   return state;
 };
 
@@ -967,6 +1117,7 @@ export const showDialogueUI = ({ state }) => {
   state.global.pendingEffects.push({
     name: "render",
   });
+  recordRollbackAction(state, "showDialogueUI", undefined);
   return state;
 };
 
@@ -975,6 +1126,7 @@ export const hideDialogueUI = ({ state }) => {
   state.global.pendingEffects.push({
     name: "render",
   });
+  recordRollbackAction(state, "hideDialogueUI", undefined);
   return state;
 };
 
@@ -994,6 +1146,7 @@ export const showDialogueHistory = ({ state }) => {
   state.global.pendingEffects.push({
     name: "render",
   });
+  recordRollbackAction(state, "showDialogueHistory", undefined);
   return state;
 };
 
@@ -1002,6 +1155,7 @@ export const hideDialogueHistory = ({ state }) => {
   state.global.pendingEffects.push({
     name: "render",
   });
+  recordRollbackAction(state, "hideDialogueHistory", undefined);
   return state;
 };
 
@@ -1103,6 +1257,8 @@ export const setNextLineConfig = ({ state }, payload) => {
   const { manual, auto, applyMode } = payload;
   const previousAutoEnabled = state.global.nextLineConfig.auto?.enabled;
   const previousApplyMode = state.global.nextLineConfig?.applyMode;
+  const isRollbackRestoring =
+    state.contexts?.[state.contexts.length - 1]?.rollback?.isRestoring === true;
 
   // If both manual and auto are provided, do complete replacement
   if (manual && auto) {
@@ -1137,7 +1293,11 @@ export const setNextLineConfig = ({ state }, payload) => {
   const currentAutoEnabled = state.global.nextLineConfig.auto?.enabled;
 
   // If auto.enabled state has changed, dispatch timer effects
-  if (currentAutoEnabled === true && !previousAutoEnabled) {
+  if (
+    !isRollbackRestoring &&
+    currentAutoEnabled === true &&
+    !previousAutoEnabled
+  ) {
     const trigger = state.global.nextLineConfig.auto?.trigger;
 
     // Event-based: only start timer immediately if trigger is "fromStart"
@@ -1155,7 +1315,11 @@ export const setNextLineConfig = ({ state }, payload) => {
         payload: { delay: state.global.nextLineConfig.auto.delay },
       });
     }
-  } else if (currentAutoEnabled === false && previousAutoEnabled) {
+  } else if (
+    !isRollbackRestoring &&
+    currentAutoEnabled === false &&
+    previousAutoEnabled
+  ) {
     state.global.pendingEffects.push({
       name: "clearNextLineConfigTimer",
     });
@@ -1164,6 +1328,7 @@ export const setNextLineConfig = ({ state }, payload) => {
   state.global.pendingEffects.push({
     name: "render",
   });
+  recordRollbackAction(state, "setNextLineConfig", payload);
   return state;
 };
 
@@ -1844,6 +2009,7 @@ export const updateVariable = ({ state }, payload) => {
   let contextVariableModified = false;
   let globalDeviceModified = false;
   let globalAccountModified = false;
+  const contextOperations = [];
 
   operations.forEach(({ variableId, op, value }) => {
     const variableConfig = state.projectData.resources?.variables?.[variableId];
@@ -1860,6 +2026,7 @@ export const updateVariable = ({ state }, payload) => {
     // Track which scope was modified
     if (scope === "context") {
       contextVariableModified = true;
+      contextOperations.push({ variableId, op, value });
     } else if (scope === "global-device") {
       globalDeviceModified = true;
     } else if (scope === "global-account") {
@@ -1873,6 +2040,11 @@ export const updateVariable = ({ state }, payload) => {
   // Log updateVariableId to current line's history entry (EVENT SOURCING)
   // Only log if context variables were modified (global variables not tracked for rollback)
   if (contextVariableModified) {
+    recordRollbackAction(state, "updateVariable", {
+      id,
+      operations: contextOperations,
+    });
+
     const historySequence = lastContext.historySequence;
     if (historySequence && historySequence.length > 0) {
       const currentSection = historySequence[historySequence.length - 1];
@@ -1926,57 +2098,7 @@ export const updateVariable = ({ state }, payload) => {
 };
 
 /**
- * Recursively traverses any object/array looking for updateVariable actions with matching ID.
- * This is a generic approach that works regardless of where actions are defined.
- * @param {any} obj - The object to search
- * @param {string} updateVariableId - The ID to find
- * @param {string} parentKey - The key that led to this object (used to detect updateVariable context)
- * @returns {Object|undefined} The action definition or undefined
- */
-const findUpdateVariableRecursive = (obj, updateVariableId, parentKey = "") => {
-  if (obj === null || obj === undefined) return undefined;
-
-  // If this is an updateVariable object with matching ID, return it
-  if (
-    parentKey === "updateVariable" &&
-    typeof obj === "object" &&
-    obj.id === updateVariableId &&
-    Array.isArray(obj.operations)
-  ) {
-    return obj;
-  }
-
-  // Recurse into arrays
-  if (Array.isArray(obj)) {
-    for (const item of obj) {
-      const found = findUpdateVariableRecursive(
-        item,
-        updateVariableId,
-        parentKey,
-      );
-      if (found) return found;
-    }
-    return undefined;
-  }
-
-  // Recurse into objects
-  if (typeof obj === "object") {
-    for (const key of Object.keys(obj)) {
-      const found = findUpdateVariableRecursive(
-        obj[key],
-        updateVariableId,
-        key,
-      );
-      if (found) return found;
-    }
-  }
-
-  return undefined;
-};
-
-/**
- * Selects a line ID by relative offset from current position in history.
- * Uses findLastIndex to handle duplicate line entries after rollback.
+ * Selects a line ID by relative offset from the active rollback timeline.
  *
  * @param {Object} state - Current state object
  * @param {Object} payload - Selector payload
@@ -2003,66 +2125,26 @@ export const selectLineIdByOffset = ({ state }, payload) => {
 
   const rollback = lastContext.rollback;
   if (
-    Array.isArray(rollback?.timeline) &&
-    typeof rollback?.currentIndex === "number"
+    !Array.isArray(rollback?.timeline) ||
+    typeof rollback?.currentIndex !== "number"
   ) {
-    const targetIndex = rollback.currentIndex + offset;
-    if (targetIndex < 0 || targetIndex >= rollback.timeline.length) {
-      return null;
-    }
-
-    const targetLine = rollback.timeline[targetIndex];
-    return {
-      sectionId: targetLine.sectionId,
-      lineId: targetLine.lineId,
-    };
-  }
-
-  // Get current position from read pointer
-  const currentSectionId = lastContext.pointers.read?.sectionId;
-  const currentLineId = lastContext.pointers.read?.lineId;
-
-  if (!currentSectionId || !currentLineId) {
-    return null;
-  }
-
-  // Find section in history
-  const historySequence = lastContext.historySequence;
-  const sectionEntry = historySequence?.find(
-    (entry) => entry.sectionId === currentSectionId,
-  );
-
-  if (!sectionEntry?.lines || sectionEntry.lines.length === 0) {
-    return null;
-  }
-
-  // Use findLastIndex to handle duplicate entries after rollback
-  // When user rolls back and moves forward again, same lineIds may appear multiple times
-  const currentIndex = sectionEntry.lines.findLastIndex(
-    (line) => line.id === currentLineId,
-  );
-
-  if (currentIndex === -1) {
     return null;
   }
 
-  // Calculate target index
-  const targetIndex = currentIndex + offset;
-
-  // Check bounds (within section only, as per user requirement)
-  if (targetIndex < 0 || targetIndex >= sectionEntry.lines.length) {
+  const targetIndex = rollback.currentIndex + offset;
+  if (targetIndex < 0 || targetIndex >= rollback.timeline.length) {
     return null;
   }
 
-  const targetLine = sectionEntry.lines[targetIndex];
+  const targetLine = rollback.timeline[targetIndex];
   return {
-    sectionId: currentSectionId,
-    lineId: targetLine.id,
+    sectionId: targetLine.sectionId,
+    lineId: targetLine.lineId,
   };
 };
 
 /**
- * Checks if rollback is possible (not at first line of history).
+ * Checks if rollback is possible (not at the first rollback checkpoint).
  * Used for UI to conditionally enable/disable back button.
  *
  * @param {Object} state - Current state object
@@ -2074,8 +2156,7 @@ export const selectCanRollback = ({ state }) => {
 };
 
 /**
- * Rolls back by a relative offset from current position.
- * Convenience action that combines selectLineIdByOffset with rollbackToLine.
+ * Rolls back by a relative offset from the current rollback checkpoint.
  *
  * @param {Object} state - Current state object
  * @param {Object} payload - Action payload
@@ -2097,48 +2178,23 @@ export const rollbackByOffset = ({ state }, payload) => {
   }
 
   const lastContext = state.contexts?.[state.contexts.length - 1];
-  const rollback = lastContext?.rollback;
-
-  if (
-    Array.isArray(rollback?.timeline) &&
-    typeof rollback?.currentIndex === "number"
-  ) {
-    const targetIndex = rollback.currentIndex + offset;
-    if (targetIndex < 0 || targetIndex >= rollback.timeline.length) {
-      return state;
-    }
-
-    return restoreRollbackCheckpoint(state, targetIndex);
+  if (!lastContext) {
+    return state;
   }
 
-  // Get target using the selector
-  const target = selectLineIdByOffset({ state }, { offset });
-
-  if (!target) {
+  const rollback = ensureRollbackState(lastContext, {
+    compatibilityAnchor: !lastContext.rollback,
+  });
+  const targetIndex = rollback.currentIndex + offset;
+  if (targetIndex < 0 || targetIndex >= rollback.timeline.length) {
     return state;
   }
 
-  return rollbackToLine(
-    { state },
-    {
-      sectionId: target.sectionId,
-      lineId: target.lineId,
-    },
-  );
+  return restoreRollbackCheckpoint(state, targetIndex);
 };
 
 /**
- * Rolls back to a specific line using replay-forward algorithm.
- *
- * Algorithm:
- *   1. Get initialState from current section
- *   2. Reset context variables to initialState
- *   3. For each line in history BEFORE targetLineId:
- *      - For each updateVariableId in line:
- *        - Look up action definition in project data
- *        - Execute the action (apply operations)
- *   4. Set pointer to targetLineId
- *   5. Switch to read mode
+ * Rolls back to a specific line using the active rollback timeline.
  *
  * @param {Object} state - Current state object
  * @param {Object} payload - Action payload
@@ -2154,111 +2210,22 @@ export const rollbackToLine = ({ state }, payload) => {
     throw new Error("No context available for rollbackToLine");
   }
 
-  const rollback = lastContext.rollback;
-  if (Array.isArray(rollback?.timeline) && rollback.timeline.length > 0) {
-    const visibleTimeline = rollback.timeline.slice(
-      0,
-      rollback.currentIndex + 1,
-    );
-    const targetLineIndex = visibleTimeline.findLastIndex(
-      (checkpoint) =>
-        checkpoint.sectionId === sectionId && checkpoint.lineId === lineId,
-    );
-
-    if (targetLineIndex === -1) {
-      throw new Error(
-        `Line ${lineId} not found in section ${sectionId} rollback timeline`,
-      );
-    }
-
-    return restoreRollbackCheckpoint(state, targetLineIndex);
-  }
-
-  // Find the section in history
-  const historySequence = lastContext.historySequence;
-  const sectionEntry = historySequence?.find(
-    (entry) => entry.sectionId === sectionId,
+  const rollback = ensureRollbackState(lastContext, {
+    compatibilityAnchor: !lastContext.rollback,
+  });
+  const visibleTimeline = rollback.timeline.slice(0, rollback.currentIndex + 1);
+  const targetLineIndex = visibleTimeline.findLastIndex(
+    (checkpoint) =>
+      checkpoint.sectionId === sectionId && checkpoint.lineId === lineId,
   );
 
-  if (!sectionEntry?.lines) {
+  if (targetLineIndex === -1) {
     throw new Error(
-      `Section ${sectionId} not found in history or has no lines`,
+      `Line ${lineId} not found in section ${sectionId} rollback timeline`,
     );
   }
 
-  // Find target line index by lineId
-  const targetLineIndex = sectionEntry.lines.findIndex(
-    (line) => line.id === lineId,
-  );
-  if (targetLineIndex === -1) {
-    throw new Error(`Line ${lineId} not found in section ${sectionId} history`);
-  }
-
-  // Step 1: Reset context variables to initialState
-  const initialState = sectionEntry.initialState || {};
-  lastContext.variables = { ...initialState };
-
-  // Step 2: Replay all actions BEFORE the target line
-  // (We want state as it was BEFORE target line executed)
-  for (let i = 0; i < targetLineIndex; i++) {
-    const lineEntry = sectionEntry.lines[i];
-    const updateVariableIds = lineEntry.updateVariableIds || [];
-
-    for (const actionId of updateVariableIds) {
-      // Look up action definition in project data
-      const actionDef = findUpdateVariableRecursive(
-        state.projectData,
-        actionId,
-      );
-
-      if (!actionDef) {
-        throw new Error(`Action definition not found for ID: ${actionId}`);
-      }
-
-      // Apply the action's operations
-      const operations = actionDef.operations || [];
-      for (const { variableId, op, value } of operations) {
-        const variableConfig =
-          state.projectData.resources?.variables?.[variableId];
-        const scope = variableConfig?.scope;
-
-        // Only apply context-scoped variables during rollback
-        if (scope === "context") {
-          lastContext.variables[variableId] = applyVariableOperation(
-            lastContext.variables[variableId],
-            op,
-            value,
-          );
-        }
-      }
-    }
-  }
-
-  // Step 3: Truncate history to target line position
-  // This removes entries at and after targetLineIndex
-  sectionEntry.lines = sectionEntry.lines.slice(0, targetLineIndex);
-
-  // Step 4: Add target line to history (fresh entry for rollback support)
-  sectionEntry.lines.push({ id: lineId });
-
-  // Step 5: Update pointer to target line
-  lastContext.pointers.read = { sectionId, lineId };
-
-  // Step 6: Switch to read mode (makes choices interactive)
-  lastContext.currentPointerMode = "read";
-  lastContext.pointers.history = {
-    sectionId: null,
-    lineId: null,
-    historySequenceIndex: null,
-  };
-
-  // Skip animations when rolling back - set to true to disable animation
-  state.global.isLineCompleted = true;
-
-  // Queue render and line actions
-  state.global.pendingEffects.push({ name: "handleLineActions" });
-
-  return state;
+  return restoreRollbackCheckpoint(state, targetLineIndex);
 };
 
 /**************************
@@ -2309,6 +2276,8 @@ export const createSystemStore = (initialState) => {
     hideDialogueHistory,
     clearPendingEffects,
     appendPendingEffect,
+    beginRollbackActionBatch,
+    endRollbackActionBatch,
     addViewedLine,
     addViewedResource,
     setNextLineConfig,
diff --git a/vt/reference/rollback/auto-suppressed--capture-01.webp b/vt/reference/rollback/auto-suppressed--capture-01.webp
new file mode 100644
index 00000000..452721e0
--- /dev/null
+++ b/vt/reference/rollback/auto-suppressed--capture-01.webp
@@ -0,0 +1,3 @@
+version https://git-lfs.github.com/spec/v1
+oid sha256:b3e1768be16fdec7f41c194ab943b2b8d61fc7d23032f28fbc2cdef2083f7e0e
+size 3520
diff --git a/vt/reference/rollback/back-one-line--capture-01.webp b/vt/reference/rollback/back-one-line--capture-01.webp
new file mode 100644
index 00000000..07b08b1e
--- /dev/null
+++ b/vt/reference/rollback/back-one-line--capture-01.webp
@@ -0,0 +1,3 @@
+version https://git-lfs.github.com/spec/v1
+oid sha256:eb0b83d4a84d3a58a21a9d49586ebe0e88c50f497728a52ef971a286012a159d
+size 3786
diff --git a/vt/reference/rollback/by-offset--capture-01.webp b/vt/reference/rollback/by-offset--capture-01.webp
new file mode 100644
index 00000000..76f9e509
--- /dev/null
+++ b/vt/reference/rollback/by-offset--capture-01.webp
@@ -0,0 +1,3 @@
+version https://git-lfs.github.com/spec/v1
+oid sha256:1be3f47b2f58af00aa715bc4365633c91ef4af86712934a5d21dc9af7f6a7e62
+size 2814
diff --git a/vt/reference/rollback/choice-event--capture-01.webp b/vt/reference/rollback/choice-event--capture-01.webp
new file mode 100644
index 00000000..b1398e69
--- /dev/null
+++ b/vt/reference/rollback/choice-event--capture-01.webp
@@ -0,0 +1,3 @@
+version https://git-lfs.github.com/spec/v1
+oid sha256:bc0d2e11be01f6cbd818a3da910cb80ad248b547a83acc69264045193701505a
+size 4942
diff --git a/vt/reference/rollback/cross-section--capture-01.webp b/vt/reference/rollback/cross-section--capture-01.webp
new file mode 100644
index 00000000..adf3f641
--- /dev/null
+++ b/vt/reference/rollback/cross-section--capture-01.webp
@@ -0,0 +1,3 @@
+version https://git-lfs.github.com/spec/v1
+oid sha256:712feeef436a09701c02ea301c67ab001d2bcf5464b56065e4cc1ae6ffd2faba
+size 3522
diff --git a/vt/reference/rollback/layered-view-restore--capture-01.webp b/vt/reference/rollback/layered-view-restore--capture-01.webp
new file mode 100644
index 00000000..b421626c
--- /dev/null
+++ b/vt/reference/rollback/layered-view-restore--capture-01.webp
@@ -0,0 +1,3 @@
+version https://git-lfs.github.com/spec/v1
+oid sha256:37e670357b4bdd3fe40cb9d82c3fb8e3ce128b6bd751b400f08d2ac7fd01455a
+size 4580
diff --git a/vt/reference/rollback/to-line--capture-01.webp b/vt/reference/rollback/to-line--capture-01.webp
new file mode 100644
index 00000000..c4404a13
--- /dev/null
+++ b/vt/reference/rollback/to-line--capture-01.webp
@@ -0,0 +1,3 @@
+version https://git-lfs.github.com/spec/v1
+oid sha256:219f4acea930ae78e89e645b629d3eed254b51b2199199ddc15aea3d974a59d0
+size 4078
diff --git a/vt/reference/variables/rollback-offset-test-01.webp b/vt/reference/variables/rollback-offset-test-01.webp
deleted file mode 100644
index 5923bfbc..00000000
--- a/vt/reference/variables/rollback-offset-test-01.webp
+++ /dev/null
@@ -1,3 +0,0 @@
-version https://git-lfs.github.com/spec/v1
-oid sha256:64a6bb49936016b65f7fb8182d6471a6fadb6768a6fc1ef738a04a7c6d81c924
-size 5214
diff --git a/vt/reference/variables/rollback-test-01.webp b/vt/reference/variables/rollback-test-01.webp
deleted file mode 100644
index b8752f13..00000000
--- a/vt/reference/variables/rollback-test-01.webp
+++ /dev/null
@@ -1,3 +0,0 @@
-version https://git-lfs.github.com/spec/v1
-oid sha256:96e92e3f5633aa2d65bbbe21896e670d095aad8f884da26d5a7aad34b7f9f39e
-size 3714
diff --git a/vt/specs/rollback/auto-suppressed.yaml b/vt/specs/rollback/auto-suppressed.yaml
new file mode 100644
index 00000000..207ec80a
--- /dev/null
+++ b/vt/specs/rollback/auto-suppressed.yaml
@@ -0,0 +1,137 @@
+---
+title: Rollback Auto Suppression
+description: Rolling back to a line with scene auto enabled should not restart the line auto timer
+specs:
+  - scene auto advances from line 1 to line 2 on first load
+  - rollback returns to line 1
+  - waiting longer than the auto delay does not advance again after rollback
+skipInitialScreenshot: true
+viewport:
+  id: capture
+  width: 960
+  height: 540
+steps:
+  - action: wait
+    ms: 420
+  - action: click
+    x: 195
+    y: 360
+  - action: wait
+    ms: 520
+  - action: screenshot
+---
+screen:
+  width: 1920
+  height: 1080
+  backgroundColor: "#000000"
+resources:
+  characters:
+    narrator:
+      name: Guide
+  layouts:
+    baseLayout:
+      elements:
+        - id: bg
+          type: rect
+          width: 1920
+          height: 1080
+          click:
+            payload:
+              actions:
+                nextLine: {}
+          colorId: bg
+    dialogueLayout:
+      mode: adv
+      elements:
+        - id: dialogue-box
+          type: rect
+          x: 100
+          y: 760
+          width: 1720
+          height: 240
+          colorId: panel
+        - id: dialogue-text
+          type: text
+          x: 140
+          y: 835
+          width: 1400
+          content: ${dialogue.content[0].text}
+          textStyleId: textMain
+        - id: rollback-button
+          type: rect
+          x: 100
+          y: 680
+          width: 320
+          height: 60
+          colorId: button
+          click:
+            payload:
+              actions:
+                rollbackByOffset:
+                  offset: -1
+        - id: rollback-label
+          type: text
+          x: 130
+          y: 700
+          content: "[ROLLBACK]"
+          textStyleId: textButton
+  fonts:
+    fontDefault:
+      fileId: Arial
+  colors:
+    bg:
+      hex: "#000000"
+    panel:
+      hex: "#4D4D4D"
+    button:
+      hex: "#737373"
+    fg:
+      hex: "#FFFFFF"
+  textStyles:
+    textMain:
+      fontId: fontDefault
+      colorId: fg
+      fontSize: 30
+      fontWeight: "400"
+      fontStyle: normal
+      lineHeight: 1.2
+    textButton:
+      fontId: fontDefault
+      colorId: fg
+      fontSize: 28
+      fontWeight: "400"
+      fontStyle: normal
+      lineHeight: 1.2
+story:
+  initialSceneId: main
+  scenes:
+    main:
+      initialSectionId: story
+      sections:
+        story:
+          lines:
+            - id: line1
+              actions:
+                background:
+                  resourceId: baseLayout
+                setNextLineConfig:
+                  manual:
+                    enabled: true
+                  auto:
+                    enabled: true
+                    trigger: fromStart
+                    delay: 250
+                  applyMode: persistent
+                dialogue:
+                  mode: adv
+                  ui:
+                    resourceId: dialogueLayout
+                  content:
+                    - text: "Line 1. After rollback, this line should stay visible."
+                  characterId: narrator
+            - id: line2
+              actions:
+                dialogue:
+                  content:
+                    - text: "Line 2. Roll back, then wait longer than the auto delay."
+                  characterId: narrator
diff --git a/vt/specs/rollback/back-one-line.yaml b/vt/specs/rollback/back-one-line.yaml
new file mode 100644
index 00000000..47b22227
--- /dev/null
+++ b/vt/specs/rollback/back-one-line.yaml
@@ -0,0 +1,413 @@
+---
+title: Rollback Back One Line
+description: A twenty-line rollback sandbox that crosses multiple sections and scenes while exposing only a single-step back action
+specs:
+  - covers twenty visible checkpoints in total
+  - crosses four sections across two scenes
+  - boundary lines enter the next section or scene on a normal screen click
+  - uses only single-step rollback so you can back up one line at a time
+skipInitialScreenshot: true
+viewport:
+  id: capture
+  width: 960
+  height: 540
+steps:
+  - action: click
+    x: 480
+    y: 270
+  - action: wait
+    ms: 80
+  - action: click
+    x: 480
+    y: 270
+  - action: wait
+    ms: 80
+  - action: click
+    x: 480
+    y: 270
+  - action: wait
+    ms: 80
+  - action: click
+    x: 480
+    y: 270
+  - action: wait
+    ms: 100
+  - action: click
+    x: 480
+    y: 270
+  - action: wait
+    ms: 100
+  - action: click
+    x: 480
+    y: 270
+  - action: wait
+    ms: 80
+  - action: click
+    x: 480
+    y: 270
+  - action: wait
+    ms: 80
+  - action: click
+    x: 480
+    y: 270
+  - action: wait
+    ms: 80
+  - action: click
+    x: 480
+    y: 270
+  - action: wait
+    ms: 100
+  - action: click
+    x: 480
+    y: 270
+  - action: wait
+    ms: 100
+  - action: click
+    x: 480
+    y: 270
+  - action: wait
+    ms: 80
+  - action: click
+    x: 480
+    y: 270
+  - action: wait
+    ms: 80
+  - action: click
+    x: 480
+    y: 270
+  - action: wait
+    ms: 80
+  - action: click
+    x: 480
+    y: 270
+  - action: wait
+    ms: 100
+  - action: click
+    x: 480
+    y: 270
+  - action: wait
+    ms: 100
+  - action: click
+    x: 480
+    y: 270
+  - action: wait
+    ms: 80
+  - action: click
+    x: 480
+    y: 270
+  - action: wait
+    ms: 80
+  - action: click
+    x: 480
+    y: 270
+  - action: wait
+    ms: 80
+  - action: click
+    x: 480
+    y: 270
+  - action: wait
+    ms: 80
+  - action: click
+    x: 200
+    y: 360
+  - action: wait
+    ms: 150
+  - action: screenshot
+---
+screen:
+  width: 1920
+  height: 1080
+  backgroundColor: "#000000"
+resources:
+  characters:
+    narrator:
+      name: Guide
+  layouts:
+    baseLayout:
+      elements:
+        - id: bg
+          type: rect
+          width: 1920
+          height: 1080
+          click:
+            payload:
+              actions:
+                nextLine: {}
+          colorId: bg
+    toSectionA2Layout:
+      elements:
+        - id: bg
+          type: rect
+          width: 1920
+          height: 1080
+          click:
+            payload:
+              actions:
+                sectionTransition:
+                  sectionId: sectionA2
+          colorId: bg
+    toSectionB1Layout:
+      elements:
+        - id: bg
+          type: rect
+          width: 1920
+          height: 1080
+          click:
+            payload:
+              actions:
+                sectionTransition:
+                  sectionId: sectionB1
+          colorId: bg
+    toSectionB2Layout:
+      elements:
+        - id: bg
+          type: rect
+          width: 1920
+          height: 1080
+          click:
+            payload:
+              actions:
+                sectionTransition:
+                  sectionId: sectionB2
+          colorId: bg
+    dialogueLayout:
+      mode: adv
+      elements:
+        - id: dialogue-box
+          type: rect
+          x: 100
+          y: 760
+          width: 1720
+          height: 240
+          colorId: panel
+        - id: dialogue-text
+          type: text
+          x: 140
+          y: 835
+          width: 1460
+          content: ${dialogue.content[0].text}
+          textStyleId: textMain
+        - id: rollback-button
+          type: rect
+          x: 100
+          y: 680
+          width: 320
+          height: 60
+          colorId: button
+          click:
+            payload:
+              actions:
+                rollbackByOffset:
+                  offset: -1
+        - id: rollback-label
+          type: text
+          x: 130
+          y: 700
+          content: "[BACK 1 LINE]"
+          textStyleId: textButton
+        - id: hint-label
+          type: text
+          x: 1820
+          y: 70
+          anchorX: 1
+          content: "Click screen to advance"
+          textStyleId: textHint
+  fonts:
+    fontDefault:
+      fileId: Arial
+  colors:
+    bg:
+      hex: "#000000"
+    panel:
+      hex: "#4D4D4D"
+    button:
+      hex: "#737373"
+    fg:
+      hex: "#FFFFFF"
+    fgMuted:
+      hex: "#D9D9D9"
+  textStyles:
+    textMain:
+      fontId: fontDefault
+      colorId: fg
+      fontSize: 30
+      fontWeight: "400"
+      fontStyle: normal
+      lineHeight: 1.2
+    textButton:
+      fontId: fontDefault
+      colorId: fg
+      fontSize: 26
+      fontWeight: "400"
+      fontStyle: normal
+      lineHeight: 1.2
+    textHint:
+      fontId: fontDefault
+      colorId: fgMuted
+      fontSize: 28
+      fontWeight: "400"
+      fontStyle: normal
+      lineHeight: 1.2
+story:
+  initialSceneId: sceneA
+  scenes:
+    sceneA:
+      initialSectionId: sectionA1
+      sections:
+        sectionA1:
+          lines:
+            - id: line1
+              actions:
+                background:
+                  resourceId: baseLayout
+                dialogue:
+                  mode: adv
+                  ui:
+                    resourceId: dialogueLayout
+                  content:
+                    - text: "1/20. Scene A, section A1."
+                  characterId: narrator
+            - id: line2
+              actions:
+                dialogue:
+                  content:
+                    - text: "2/20. Scene A, section A1."
+                  characterId: narrator
+            - id: line3
+              actions:
+                dialogue:
+                  content:
+                    - text: "3/20. Scene A, section A1."
+                  characterId: narrator
+            - id: line4
+              actions:
+                dialogue:
+                  content:
+                    - text: "4/20. Scene A, section A1."
+                  characterId: narrator
+            - id: line5
+              actions:
+                background:
+                  resourceId: toSectionA2Layout
+                dialogue:
+                  content:
+                    - text: "5/20. Boundary checkpoint. Click anywhere to enter scene A, section A2."
+                  characterId: narrator
+        sectionA2:
+          lines:
+            - id: line1
+              actions:
+                background:
+                  resourceId: baseLayout
+                dialogue:
+                  mode: adv
+                  ui:
+                    resourceId: dialogueLayout
+                  content:
+                    - text: "6/20. Scene A, section A2."
+                  characterId: narrator
+            - id: line2
+              actions:
+                dialogue:
+                  content:
+                    - text: "7/20. Scene A, section A2."
+                  characterId: narrator
+            - id: line3
+              actions:
+                dialogue:
+                  content:
+                    - text: "8/20. Scene A, section A2."
+                  characterId: narrator
+            - id: line4
+              actions:
+                dialogue:
+                  content:
+                    - text: "9/20. Scene A, section A2."
+                  characterId: narrator
+            - id: line5
+              actions:
+                background:
+                  resourceId: toSectionB1Layout
+                dialogue:
+                  content:
+                    - text: "10/20. Boundary checkpoint. Click anywhere to enter scene B, section B1."
+                  characterId: narrator
+    sceneB:
+      initialSectionId: sectionB1
+      sections:
+        sectionB1:
+          lines:
+            - id: line1
+              actions:
+                background:
+                  resourceId: baseLayout
+                dialogue:
+                  mode: adv
+                  ui:
+                    resourceId: dialogueLayout
+                  content:
+                    - text: "11/20. Scene B, section B1."
+                  characterId: narrator
+            - id: line2
+              actions:
+                dialogue:
+                  content:
+                    - text: "12/20. Scene B, section B1."
+                  characterId: narrator
+            - id: line3
+              actions:
+                dialogue:
+                  content:
+                    - text: "13/20. Scene B, section B1."
+                  characterId: narrator
+            - id: line4
+              actions:
+                dialogue:
+                  content:
+                    - text: "14/20. Scene B, section B1."
+                  characterId: narrator
+            - id: line5
+              actions:
+                background:
+                  resourceId: toSectionB2Layout
+                dialogue:
+                  content:
+                    - text: "15/20. Boundary checkpoint. Click anywhere to enter scene B, section B2."
+                  characterId: narrator
+        sectionB2:
+          lines:
+            - id: line1
+              actions:
+                background:
+                  resourceId: baseLayout
+                dialogue:
+                  mode: adv
+                  ui:
+                    resourceId: dialogueLayout
+                  content:
+                    - text: "16/20. Scene B, section B2."
+                  characterId: narrator
+            - id: line2
+              actions:
+                dialogue:
+                  content:
+                    - text: "17/20. Scene B, section B2."
+                  characterId: narrator
+            - id: line3
+              actions:
+                dialogue:
+                  content:
+                    - text: "18/20. Scene B, section B2."
+                  characterId: narrator
+            - id: line4
+              actions:
+                dialogue:
+                  content:
+                    - text: "19/20. Scene B, section B2."
+                  characterId: narrator
+            - id: line5
+              actions:
+                dialogue:
+                  content:
+                    - text: "20/20. Final checkpoint. Use BACK 1 LINE to step backward one line at a time."
+                  characterId: narrator
diff --git a/vt/specs/rollback/by-offset.yaml b/vt/specs/rollback/by-offset.yaml
new file mode 100644
index 00000000..7094aa7b
--- /dev/null
+++ b/vt/specs/rollback/by-offset.yaml
@@ -0,0 +1,223 @@
+---
+title: Rollback By Offset
+description: rollbackByOffset should jump back multiple checkpoints and restore score and line state
+specs:
+  - advances through five lines with cumulative score changes
+  - rolls back three checkpoints in one action
+  - restores the earlier line and its score total
+skipInitialScreenshot: true
+viewport:
+  id: capture
+  width: 960
+  height: 540
+steps:
+  - action: click
+    x: 480
+    y: 270
+  - action: click
+    x: 480
+    y: 270
+  - action: click
+    x: 480
+    y: 270
+  - action: click
+    x: 480
+    y: 270
+  - action: wait
+    ms: 120
+  - action: click
+    x: 420
+    y: 360
+  - action: wait
+    ms: 150
+  - action: screenshot
+---
+screen:
+  width: 1920
+  height: 1080
+  backgroundColor: "#000000"
+resources:
+  variables:
+    score:
+      type: number
+      scope: context
+      default: 0
+    lineVisited:
+      type: number
+      scope: context
+      default: 1
+  characters:
+    narrator:
+      name: Guide
+  layouts:
+    baseLayout:
+      elements:
+        - id: bg
+          type: rect
+          width: 1920
+          height: 1080
+          click:
+            payload:
+              actions:
+                nextLine: {}
+          colorId: bg
+    dialogueLayout:
+      mode: adv
+      elements:
+        - id: dialogue-box
+          type: rect
+          x: 100
+          y: 760
+          width: 1720
+          height: 240
+          colorId: panel
+        - id: dialogue-text
+          type: text
+          x: 140
+          y: 835
+          width: 1300
+          content: ${dialogue.content[0].text}
+          textStyleId: textMain
+        - id: score-display
+          type: text
+          x: 1780
+          y: 70
+          anchorX: 1
+          content: "Score: ${variables.score}"
+          textStyleId: textScore
+        - id: rollback-three
+          type: rect
+          x: 520
+          y: 680
+          width: 360
+          height: 60
+          colorId: button
+          click:
+            payload:
+              actions:
+                rollbackByOffset:
+                  offset: -3
+        - id: rollback-three-label
+          type: text
+          x: 555
+          y: 700
+          content: "[BACK 3 LINES]"
+          textStyleId: textButton
+  fonts:
+    fontDefault:
+      fileId: Arial
+  colors:
+    bg:
+      hex: "#000000"
+    panel:
+      hex: "#4D4D4D"
+    button:
+      hex: "#737373"
+    fg:
+      hex: "#FFFFFF"
+    fgMuted:
+      hex: "#D9D9D9"
+    fgSoft:
+      hex: "#A6A6A6"
+  textStyles:
+    textMain:
+      fontId: fontDefault
+      colorId: fg
+      fontSize: 30
+      fontWeight: "400"
+      fontStyle: normal
+      lineHeight: 1.2
+    textScore:
+      fontId: fontDefault
+      colorId: fgMuted
+      fontSize: 32
+      fontWeight: bold
+      fontStyle: normal
+      lineHeight: 1.2
+    textLine:
+      fontId: fontDefault
+      colorId: fgSoft
+      fontSize: 28
+      fontWeight: "400"
+      fontStyle: normal
+      lineHeight: 1.2
+    textButton:
+      fontId: fontDefault
+      colorId: fg
+      fontSize: 26
+      fontWeight: "400"
+      fontStyle: normal
+      lineHeight: 1.2
+story:
+  initialSceneId: main
+  scenes:
+    main:
+      initialSectionId: story
+      sections:
+        story:
+          lines:
+            - id: line1
+              actions:
+                background:
+                  resourceId: baseLayout
+                updateVariable:
+                  id: visit1
+                  operations:
+                    - variableId: lineVisited
+                      op: set
+                      value: 1
+                dialogue:
+                  mode: adv
+                  ui:
+                    resourceId: dialogueLayout
+                  content:
+                    - text: "Line 1. Start at score 0."
+                  characterId: narrator
+            - id: line2
+              actions:
+                updateVariable:
+                  id: visit2
+                  operations:
+                    - variableId: score
+                      op: increment
+                      value: 5
+                dialogue:
+                  content:
+                    - text: "Line 2. Score is 5."
+                  characterId: narrator
+            - id: line3
+              actions:
+                updateVariable:
+                  id: visit3
+                  operations:
+                    - variableId: score
+                      op: increment
+                      value: 10
+                dialogue:
+                  content:
+                    - text: "Line 3. Score is 15."
+                  characterId: narrator
+            - id: line4
+              actions:
+                updateVariable:
+                  id: visit4
+                  operations:
+                    - variableId: score
+                      op: increment
+                      value: 15
+                dialogue:
+                  content:
+                    - text: "Line 4. Score is 30."
+                  characterId: narrator
+            - id: line5
+              actions:
+                updateVariable:
+                  id: visit5
+                  operations:
+                    - variableId: score
+                      op: increment
+                      value: 20
+                dialogue:
+                  content:
+                    - text: "Line 5. Score is 50. Roll back three lines."
+                  characterId: narrator
diff --git a/vt/specs/rollback/choice-event.yaml b/vt/specs/rollback/choice-event.yaml
new file mode 100644
index 00000000..9cde3b48
--- /dev/null
+++ b/vt/specs/rollback/choice-event.yaml
@@ -0,0 +1,225 @@
+---
+title: Rollback Choice Event
+description: Choice click actions should stay attached to the source checkpoint through rollback
+specs:
+  - two branch choices are visible on the source line
+  - a choice click updates score and transitions to another section
+  - rollback returns to the source line instead of the result section
+  - the source line keeps the branch score from the executed choice action
+skipInitialScreenshot: true
+viewport:
+  id: capture
+  width: 960
+  height: 540
+steps:
+  - action: click
+    x: 780
+    y: 140
+  - action: wait
+    ms: 150
+  - action: click
+    x: 195
+    y: 360
+  - action: wait
+    ms: 150
+  - action: screenshot
+---
+screen:
+  width: 1920
+  height: 1080
+  backgroundColor: "#000000"
+resources:
+  variables:
+    score:
+      type: number
+      scope: context
+      default: 0
+  characters:
+    narrator:
+      name: Guide
+  layouts:
+    baseLayout:
+      elements:
+        - id: bg
+          type: rect
+          width: 1920
+          height: 1080
+          colorId: bg
+    dialogueLayout:
+      mode: adv
+      elements:
+        - id: dialogue-box
+          type: rect
+          x: 100
+          y: 760
+          width: 1720
+          height: 240
+          colorId: panel
+        - id: dialogue-text
+          type: text
+          x: 140
+          y: 835
+          width: 1200
+          content: ${dialogue.content[0].text}
+          textStyleId: textMain
+        - id: score-display
+          type: text
+          x: 1780
+          y: 70
+          anchorX: 1
+          content: "Score: ${variables.score}"
+          textStyleId: textScore
+        - id: rollback-button
+          type: rect
+          x: 100
+          y: 680
+          width: 320
+          height: 60
+          colorId: button
+          click:
+            payload:
+              actions:
+                rollbackByOffset:
+                  offset: -1
+        - id: rollback-label
+          type: text
+          x: 130
+          y: 700
+          content: "[ROLLBACK]"
+          textStyleId: textButton
+    choiceLayout:
+      elements:
+        - id: choice-a-button
+          type: rect
+          x: 260
+          y: 220
+          width: 1400
+          height: 80
+          colorId: button
+          click:
+            payload:
+              actions:
+                updateVariable:
+                  id: chooseA15
+                  operations:
+                    - variableId: score
+                      op: set
+                      value: 15
+                sectionTransition:
+                  sectionId: result
+        - id: choice-a-label
+          type: text
+          x: 320
+          y: 245
+          content: "Choose A"
+          textStyleId: textMain
+        - id: choice-b-button
+          type: rect
+          x: 260
+          y: 330
+          width: 1400
+          height: 80
+          colorId: button
+          click:
+            payload:
+              actions:
+                updateVariable:
+                  id: chooseB5
+                  operations:
+                    - variableId: score
+                      op: set
+                      value: 5
+                sectionTransition:
+                  sectionId: resultB
+        - id: choice-b-label
+          type: text
+          x: 320
+          y: 355
+          content: "Choose B"
+          textStyleId: textMain
+  fonts:
+    fontDefault:
+      fileId: Arial
+  colors:
+    bg:
+      hex: "#000000"
+    panel:
+      hex: "#4D4D4D"
+    button:
+      hex: "#737373"
+    fg:
+      hex: "#FFFFFF"
+    fgMuted:
+      hex: "#D9D9D9"
+  textStyles:
+    textMain:
+      fontId: fontDefault
+      colorId: fg
+      fontSize: 30
+      fontWeight: "400"
+      fontStyle: normal
+      lineHeight: 1.2
+    textScore:
+      fontId: fontDefault
+      colorId: fgMuted
+      fontSize: 32
+      fontWeight: bold
+      fontStyle: normal
+      lineHeight: 1.2
+    textButton:
+      fontId: fontDefault
+      colorId: fg
+      fontSize: 28
+      fontWeight: "400"
+      fontStyle: normal
+      lineHeight: 1.2
+story:
+  initialSceneId: main
+  scenes:
+    main:
+      initialSectionId: source
+      sections:
+        source:
+          lines:
+            - id: line1
+              actions:
+                background:
+                  resourceId: baseLayout
+                dialogue:
+                  mode: adv
+                  ui:
+                    resourceId: dialogueLayout
+                  content:
+                    - text: "Source line. Score should stay at 15 after rollback."
+                  characterId: narrator
+                choice:
+                  resourceId: choiceLayout
+                  items:
+                    - id: a
+                      content: Choose A
+                    - id: b
+                      content: Choose B
+        result:
+          lines:
+            - id: line1
+              actions:
+                choice: {}
+                dialogue:
+                  mode: adv
+                  ui:
+                    resourceId: dialogueLayout
+                  content:
+                    - text: "Result line after the choice click."
+                  characterId: narrator
+        resultB:
+          lines:
+            - id: line1
+              actions:
+                choice: {}
+                dialogue:
+                  mode: adv
+                  ui:
+                    resourceId: dialogueLayout
+                  content:
+                    - text: "Result line after choice B."
+                  characterId: narrator
diff --git a/vt/specs/rollback/cross-section.yaml b/vt/specs/rollback/cross-section.yaml
new file mode 100644
index 00000000..3b4ec91b
--- /dev/null
+++ b/vt/specs/rollback/cross-section.yaml
@@ -0,0 +1,184 @@
+---
+title: Rollback Cross Section
+description: Rollback should replay to a checkpoint in a previous section and restore that section's state
+specs:
+  - advances from a source section into a result section
+  - the result section adds more context state on arrival
+  - rollbackToLine returns directly to the source checkpoint and restores its score
+skipInitialScreenshot: true
+viewport:
+  id: capture
+  width: 960
+  height: 540
+steps:
+  - action: click
+    x: 480
+    y: 270
+  - action: click
+    x: 480
+    y: 270
+  - action: wait
+    ms: 150
+  - action: click
+    x: 200
+    y: 360
+  - action: wait
+    ms: 150
+  - action: screenshot
+---
+screen:
+  width: 1920
+  height: 1080
+  backgroundColor: "#000000"
+resources:
+  variables:
+    score:
+      type: number
+      scope: context
+      default: 0
+  characters:
+    narrator:
+      name: Guide
+  layouts:
+    baseLayout:
+      elements:
+        - id: bg
+          type: rect
+          width: 1920
+          height: 1080
+          click:
+            payload:
+              actions:
+                nextLine: {}
+          colorId: bg
+    dialogueLayout:
+      mode: adv
+      elements:
+        - id: dialogue-box
+          type: rect
+          x: 100
+          y: 760
+          width: 1720
+          height: 240
+          colorId: panel
+        - id: dialogue-text
+          type: text
+          x: 140
+          y: 835
+          width: 1320
+          content: ${dialogue.content[0].text}
+          textStyleId: textMain
+        - id: score-display
+          type: text
+          x: 1780
+          y: 70
+          anchorX: 1
+          content: "Score: ${variables.score}"
+          textStyleId: textScore
+        - id: rollback-button
+          type: rect
+          x: 100
+          y: 680
+          width: 320
+          height: 60
+          colorId: button
+          click:
+            payload:
+              actions:
+                rollbackToLine:
+                  sectionId: source
+                  lineId: line2
+        - id: rollback-label
+          type: text
+          x: 130
+          y: 700
+          content: "[BACK TO SOURCE]"
+          textStyleId: textButton
+  fonts:
+    fontDefault:
+      fileId: Arial
+  colors:
+    bg:
+      hex: "#000000"
+    panel:
+      hex: "#4D4D4D"
+    button:
+      hex: "#737373"
+    fg:
+      hex: "#FFFFFF"
+    fgMuted:
+      hex: "#D9D9D9"
+  textStyles:
+    textMain:
+      fontId: fontDefault
+      colorId: fg
+      fontSize: 30
+      fontWeight: "400"
+      fontStyle: normal
+      lineHeight: 1.2
+    textScore:
+      fontId: fontDefault
+      colorId: fgMuted
+      fontSize: 32
+      fontWeight: bold
+      fontStyle: normal
+      lineHeight: 1.2
+    textButton:
+      fontId: fontDefault
+      colorId: fg
+      fontSize: 25
+      fontWeight: "400"
+      fontStyle: normal
+      lineHeight: 1.2
+story:
+  initialSceneId: main
+  scenes:
+    main:
+      initialSectionId: source
+      sections:
+        source:
+          lines:
+            - id: line1
+              actions:
+                background:
+                  resourceId: baseLayout
+                dialogue:
+                  mode: adv
+                  ui:
+                    resourceId: dialogueLayout
+                  content:
+                    - text: "Source line 1. Advance to the checkpoint line."
+                  characterId: narrator
+            - id: line2
+              actions:
+                updateVariable:
+                  id: sourceScore10
+                  operations:
+                    - variableId: score
+                      op: set
+                      value: 10
+                dialogue:
+                  content:
+                    - text: "Source line 2. Score is 10 here."
+                  characterId: narrator
+            - id: line3
+              actions:
+                sectionTransition:
+                  sectionId: result
+        result:
+          lines:
+            - id: line1
+              actions:
+                updateVariable:
+                  id: resultAdd5
+                  operations:
+                    - variableId: score
+                      op: increment
+                      value: 5
+                dialogue:
+                  mode: adv
+                  ui:
+                    resourceId: dialogueLayout
+                  content:
+                    - text: "Result line. Score is 15 before rollback."
+                  characterId: narrator
diff --git a/vt/specs/rollback/layered-view-restore.yaml b/vt/specs/rollback/layered-view-restore.yaml
new file mode 100644
index 00000000..520b6f23
--- /dev/null
+++ b/vt/specs/rollback/layered-view-restore.yaml
@@ -0,0 +1,219 @@
+---
+title: Rollback Restores Layered View
+description: Rolling back to a checkpoint should restore the current line layered view state
+specs:
+  - line 2 opens a layered info panel
+  - line 3 clears the layered view
+  - rollback returns to line 2 and restores the info panel
+skipInitialScreenshot: true
+viewport:
+  id: capture
+  width: 960
+  height: 540
+steps:
+  - action: click
+    x: 885
+    y: 360
+  - action: click
+    x: 885
+    y: 360
+  - action: wait
+    ms: 120
+  - action: click
+    x: 195
+    y: 360
+  - action: wait
+    ms: 150
+  - action: screenshot
+---
+screen:
+  width: 1920
+  height: 1080
+  backgroundColor: "#000000"
+resources:
+  characters:
+    narrator:
+      name: Guide
+  layouts:
+    baseLayout:
+      elements:
+        - id: bg
+          type: rect
+          width: 1920
+          height: 1080
+          click:
+            payload:
+              actions:
+                nextLine: {}
+          colorId: bg
+    dialogueLayout:
+      mode: adv
+      elements:
+        - id: dialogue-box
+          type: rect
+          x: 100
+          y: 760
+          width: 1720
+          height: 240
+          colorId: panel
+        - id: dialogue-text
+          type: text
+          x: 140
+          y: 835
+          width: 1400
+          content: ${dialogue.content[0].text}
+          textStyleId: textMain
+        - id: rollback-button
+          type: rect
+          x: 100
+          y: 680
+          width: 320
+          height: 60
+          colorId: button
+          click:
+            payload:
+              actions:
+                rollbackByOffset:
+                  offset: -1
+        - id: rollback-label
+          type: text
+          x: 130
+          y: 700
+          content: "[ROLLBACK]"
+          textStyleId: textButton
+        - id: next-button
+          type: rect
+          x: 1540
+          y: 680
+          width: 280
+          height: 60
+          colorId: button
+          click:
+            payload:
+              actions:
+                nextLine: {}
+        - id: next-label
+          type: text
+          x: 1600
+          y: 700
+          content: "[NEXT]"
+          textStyleId: textButton
+    infoPanel:
+      elements:
+        - id: info-panel
+          type: rect
+          x: 500
+          y: 180
+          width: 920
+          height: 220
+          opacity: 0.92
+          colorId: button
+        - id: info-title
+          type: text
+          x: 560
+          y: 225
+          content: "Overlay Restored"
+          textStyleId: textOverlayTitle
+        - id: info-body
+          type: text
+          x: 560
+          y: 290
+          width: 420
+          content: "This panel exists only on line 2."
+          textStyleId: textOverlayBody
+        - id: info-rollback-button
+          type: rect
+          x: 1080
+          y: 325
+          width: 260
+          height: 50
+          colorId: panel
+          click:
+            payload:
+              actions:
+                rollbackByOffset:
+                  offset: -1
+        - id: info-rollback-label
+          type: text
+          x: 1125
+          y: 340
+          content: "[BACK]"
+          textStyleId: textOverlayBody
+  fonts:
+    fontDefault:
+      fileId: Arial
+  colors:
+    bg:
+      hex: "#000000"
+    panel:
+      hex: "#4D4D4D"
+    button:
+      hex: "#737373"
+    fg:
+      hex: "#FFFFFF"
+    fgMuted:
+      hex: "#D9D9D9"
+  textStyles:
+    textMain:
+      fontId: fontDefault
+      colorId: fg
+      fontSize: 30
+      fontWeight: "400"
+      fontStyle: normal
+      lineHeight: 1.2
+    textButton:
+      fontId: fontDefault
+      colorId: fg
+      fontSize: 28
+      fontWeight: "400"
+      fontStyle: normal
+      lineHeight: 1.2
+    textOverlayTitle:
+      fontId: fontDefault
+      colorId: fg
+      fontSize: 34
+      fontWeight: bold
+      fontStyle: normal
+      lineHeight: 1.2
+    textOverlayBody:
+      fontId: fontDefault
+      colorId: fgMuted
+      fontSize: 24
+      fontWeight: "400"
+      fontStyle: normal
+      lineHeight: 1.2
+story:
+  initialSceneId: main
+  scenes:
+    main:
+      initialSectionId: story
+      sections:
+        story:
+          lines:
+            - id: line1
+              actions:
+                background:
+                  resourceId: baseLayout
+                dialogue:
+                  mode: adv
+                  ui:
+                    resourceId: dialogueLayout
+                  content:
+                    - text: "Line 1. Move forward to the overlay line."
+                  characterId: narrator
+            - id: line2
+              actions:
+                pushLayeredView:
+                  resourceId: infoPanel
+                  resourceType: layout
+                dialogue:
+                  content:
+                    - text: "Line 2. Overlay restored."
+                  characterId: narrator
+            - id: line3
+              actions:
+                clearLayeredViews: {}
+                dialogue:
+                  content:
+                    - text: "Line 3. Overlay is cleared. Roll back one line."
+                  characterId: narrator
diff --git a/vt/specs/variables/rollback-test.yaml b/vt/specs/rollback/to-line.yaml
similarity index 53%
rename from vt/specs/variables/rollback-test.yaml
rename to vt/specs/rollback/to-line.yaml
index 6815af05..78ad3ffb 100644
--- a/vt/specs/variables/rollback-test.yaml
+++ b/vt/specs/rollback/to-line.yaml
@@ -1,6 +1,33 @@
 ---
-title: Rollback Test
-description: Simple visual novel simulation to test variable rollback
+title: Rollback To Line
+description: Direct rollbackToLine should restore the source line and reset context score
+specs:
+  - advances through score-changing lines
+  - uses rollbackToLine to return to the first line
+  - restores score and dialogue content for the target line
+skipInitialScreenshot: true
+viewport:
+  id: capture
+  width: 960
+  height: 540
+steps:
+  - action: click
+    x: 480
+    y: 270
+  - action: click
+    x: 480
+    y: 270
+  - action: click
+    x: 480
+    y: 270
+  - action: wait
+    ms: 120
+  - action: click
+    x: 200
+    y: 360
+  - action: wait
+    ms: 150
+  - action: screenshot
 ---
 screen:
   width: 1920
@@ -26,104 +53,83 @@ resources:
             payload:
               actions:
                 nextLine: {}
-          colorId: layoutColor1
-    dialogueUI:
-      name: Dialogue UI
+          colorId: bg
+    dialogueLayout:
       mode: adv
       elements:
-        - id: dialogueBox
+        - id: dialogue-box
           type: rect
           x: 100
-          y: 750
+          y: 760
           width: 1720
-          height: 280
-          opacity: 0.9
-          click:
-            payload:
-              actions:
-                nextLine: {}
-          colorId: layoutColor2
-        - id: charName
-          type: text
-          content: ${dialogue.character.name}
-          x: 150
-          y: 770
-          textStyleId: textStyle1
-        - id: dialogueText
+          height: 240
+          colorId: panel
+        - id: dialogue-text
           type: text
+          x: 140
+          y: 835
+          width: 1400
           content: ${dialogue.content[0].text}
-          x: 150
-          y: 820
-          width: 1620
-          textStyleId: textStyle2
-        - id: scoreDisplay
+          textStyleId: textMain
+        - id: score-display
           type: text
-          content: "Score: ${variables.score}"
-          x: 1700
-          y: 50
+          x: 1780
+          y: 70
           anchorX: 1
-          textStyleId: textStyle3
-        - id: backBtn
-          type: text
-          content: "[BACK to Line 1]"
+          content: "Score: ${variables.score}"
+          textStyleId: textScore
+        - id: rollback-button
+          type: rect
           x: 100
-          y: 700
-          hover:
-            textStyleId: textStyle5
+          y: 680
+          width: 320
+          height: 60
+          colorId: button
           click:
             payload:
               actions:
                 rollbackToLine:
                   sectionId: story
                   lineId: line1
-          textStyleId: textStyle4
+        - id: rollback-label
+          type: text
+          x: 130
+          y: 700
+          content: "[BACK TO LINE 1]"
+          textStyleId: textButton
   fonts:
     fontDefault:
       fileId: Arial
   colors:
-    color1:
-      hex: "#737373"
-    color2:
-      hex: "#D9D9D9"
-    color3:
-      hex: "#A6A6A6"
-    layoutColor1:
+    bg:
       hex: "#000000"
-    layoutColor2:
+    panel:
       hex: "#4D4D4D"
+    button:
+      hex: "#737373"
+    fg:
+      hex: "#FFFFFF"
+    fgMuted:
+      hex: "#D9D9D9"
   textStyles:
-    textStyle1:
+    textMain:
       fontId: fontDefault
-      colorId: color1
-      fontSize: 28
-      fontWeight: bold
-      fontStyle: normal
-      lineHeight: 1.2
-    textStyle2:
-      fontId: fontDefault
-      colorId: color2
-      fontSize: 24
+      colorId: fg
+      fontSize: 30
       fontWeight: "400"
       fontStyle: normal
       lineHeight: 1.2
-    textStyle3:
+    textScore:
       fontId: fontDefault
-      colorId: color3
+      colorId: fgMuted
       fontSize: 32
       fontWeight: bold
       fontStyle: normal
       lineHeight: 1.2
-    textStyle4:
-      fontId: fontDefault
-      colorId: color1
-      fontSize: 28
-      fontWeight: "400"
-      fontStyle: normal
-      lineHeight: 1.2
-    textStyle5:
+    textButton:
       fontId: fontDefault
-      colorId: color3
-      fontSize: 28
+      colorId: fg
+      fontSize: 26
       fontWeight: "400"
       fontStyle: normal
       lineHeight: 1.2
@@ -131,11 +137,9 @@ story:
   initialSceneId: main
   scenes:
     main:
-      name: Main Scene
       initialSectionId: story
       sections:
         story:
-          name: Story
           lines:
             - id: line1
               actions:
@@ -144,43 +148,37 @@ story:
                 dialogue:
                   mode: adv
                   ui:
-                    resourceId: dialogueUI
+                    resourceId: dialogueLayout
                   content:
-                    - text: Welcome! Your current score is 0. Click to continue...
+                    - text: "Line 1. After rollback, score should be back at 0."
                   characterId: narrator
             - id: line2
               actions:
                 dialogue:
                   content:
-                    - text: This is the second line. Nothing changes here yet.
+                    - text: "Line 2. Score is still 0."
                   characterId: narrator
             - id: line3
               actions:
                 updateVariable:
-                  id: uvAddScore
+                  id: add10
                   operations:
                     - variableId: score
                       op: increment
                       value: 10
                 dialogue:
                   content:
-                    - text: You gained +10 points! Watch the score in the corner.
+                    - text: "Line 3. Score increased to 10."
                   characterId: narrator
             - id: line4
               actions:
                 updateVariable:
-                  id: uvAddMore
+                  id: add20
                   operations:
                     - variableId: score
                       op: increment
                       value: 20
                 dialogue:
                   content:
-                    - text: Another +20 points! Now try clicking [BACK] to return to line 1.
-                  characterId: narrator
-            - id: line5
-              actions:
-                dialogue:
-                  content:
-                    - text: If rollback works, your score should reset to 0 when you go back!
+                    - text: "Line 4. Score is now 30. Use rollback."
                   characterId: narrator
diff --git a/vt/specs/variables/rollback-offset-test.yaml b/vt/specs/variables/rollback-offset-test.yaml
deleted file mode 100644
index af28dcb2..00000000
--- a/vt/specs/variables/rollback-offset-test.yaml
+++ /dev/null
@@ -1,273 +0,0 @@
----
-title: Rollback By Offset Test
-description: Test rollbackByOffset action - go back N lines with variable reversion
----
-screen:
-  width: 1920
-  height: 1080
-  backgroundColor: "#000000"
-resources:
-  variables:
-    score:
-      type: number
-      scope: context
-      default: 0
-    lineVisited:
-      type: number
-      scope: context
-      default: 1
-  characters:
-    narrator:
-      name: Guide
-  layouts:
-    baseLayout:
-      elements:
-        - id: bg
-          type: rect
-          width: 1920
-          height: 1080
-          click:
-            payload:
-              actions:
-                nextLine: {}
-          colorId: layoutColor1
-    dialogueUI:
-      name: Dialogue UI
-      mode: adv
-      elements:
-        - id: dialogueBox
-          type: rect
-          x: 100
-          y: 750
-          width: 1720
-          height: 280
-          opacity: 0.9
-          click:
-            payload:
-              actions:
-                nextLine: {}
-          colorId: color4
-        - id: charName
-          type: text
-          content: ${dialogue.character.name}
-          x: 150
-          y: 770
-          textStyleId: textStyle1
-        - id: dialogueText
-          type: text
-          content: ${dialogue.content[0].text}
-          x: 150
-          y: 820
-          width: 1620
-          textStyleId: textStyle2
-        - id: scoreDisplay
-          type: text
-          content: "Score: ${variables.score}"
-          x: 1700
-          y: 50
-          anchorX: 1
-          textStyleId: textStyle3
-        - id: lineIndicator
-          type: text
-          content: "Line visited: ${variables.lineVisited}"
-          x: 1700
-          y: 100
-          anchorX: 1
-          textStyleId: textStyle4
-        - id: backOneBtn
-          type: text
-          content: "[BACK 1 LINE]"
-          x: 100
-          y: 680
-          hover:
-            textStyleId: textStyle5
-          click:
-            payload:
-              actions:
-                rollbackByOffset:
-                  offset: -1
-          textStyleId: textStyle4
-        - id: backTwoBtn
-          type: text
-          content: "[BACK 2 LINES]"
-          x: 350
-          y: 680
-          hover:
-            textStyleId: textStyle4
-          click:
-            payload:
-              actions:
-                rollbackByOffset:
-                  offset: -2
-          textStyleId: textStyle4
-        - id: backThreeBtn
-          type: text
-          content: "[BACK 3 LINES]"
-          x: 620
-          y: 680
-          hover:
-            textStyleId: textStyle4
-          click:
-            payload:
-              actions:
-                rollbackByOffset:
-                  offset: -3
-          textStyleId: textStyle6
-  fonts:
-    fontDefault:
-      fileId: Arial
-  colors:
-    color1:
-      hex: "#737373"
-    color2:
-      hex: "#D9D9D9"
-    color3:
-      hex: "#A6A6A6"
-    color4:
-      hex: "#4D4D4D"
-    layoutColor1:
-      hex: "#000000"
-  textStyles:
-    textStyle1:
-      fontId: fontDefault
-      colorId: color1
-      fontSize: 28
-      fontWeight: bold
-      fontStyle: normal
-      lineHeight: 1.2
-    textStyle2:
-      fontId: fontDefault
-      colorId: color2
-      fontSize: 24
-      fontWeight: "400"
-      fontStyle: normal
-      lineHeight: 1.2
-    textStyle3:
-      fontId: fontDefault
-      colorId: color3
-      fontSize: 32
-      fontWeight: bold
-      fontStyle: normal
-      lineHeight: 1.2
-    textStyle4:
-      fontId: fontDefault
-      colorId: color1
-      fontSize: 24
-      fontWeight: "400"
-      fontStyle: normal
-      lineHeight: 1.2
-    textStyle5:
-      fontId: fontDefault
-      colorId: color3
-      fontSize: 24
-      fontWeight: "400"
-      fontStyle: normal
-      lineHeight: 1.2
-    textStyle6:
-      fontId: fontDefault
-      colorId: color4
-      fontSize: 24
-      fontWeight: "400"
-      fontStyle: normal
-      lineHeight: 1.2
-story:
-  initialSceneId: main
-  scenes:
-    main:
-      name: Main Scene
-      initialSectionId: story
-      sections:
-        story:
-          name: Story
-          lines:
-            - id: line1
-              actions:
-                background:
-                  resourceId: baseLayout
-                updateVariable:
-                  id: uvLine1
-                  operations:
-                    - variableId: lineVisited
-                      op: set
-                      value: 1
-                dialogue:
-                  mode: adv
-                  ui:
-                    resourceId: dialogueUI
-                  content:
-                    - text: "LINE 1: Score is 0. Use the back buttons above to test offset rollback!"
-                  characterId: narrator
-            - id: line2
-              actions:
-                updateVariable:
-                  id: uvLine2Score
-                  operations:
-                    - variableId: score
-                      op: increment
-                      value: 5
-                    - variableId: lineVisited
-                      op: set
-                      value: 2
-                dialogue:
-                  content:
-                    - text: "LINE 2: +5 points! (Total: 5)"
-                  characterId: narrator
-            - id: line3
-              actions:
-                updateVariable:
-                  id: uvLine3Score
-                  operations:
-                    - variableId: score
-                      op: increment
-                      value: 10
-                    - variableId: lineVisited
-                      op: set
-                      value: 3
-                dialogue:
-                  content:
-                    - text: "LINE 3: +10 points! (Total: 15)"
-                  characterId: narrator
-            - id: line4
-              actions:
-                updateVariable:
-                  id: uvLine4Score
-                  operations:
-                    - variableId: score
-                      op: increment
-                      value: 15
-                    - variableId: lineVisited
-                      op: set
-                      value: 4
-                dialogue:
-                  content:
-                    - text: "LINE 4: +15 points! (Total: 30)"
-                  characterId: narrator
-            - id: line5
-              actions:
-                updateVariable:
-                  id: uvLine5Score
-                  operations:
-                    - variableId: score
-                      op: increment
-                      value: 20
-                    - variableId: lineVisited
-                      op: set
-                      value: 5
-                dialogue:
-                  content:
-                    - text: "LINE 5: +20 points! (Total: 50) - Try the back buttons now!"
-                  characterId: narrator
-            - id: line6
-              actions:
-                updateVariable:
-                  id: uvLine6
-                  operations:
-                    - variableId: lineVisited
-                      op: set
-                      value: 6
-                dialogue:
-                  content:
-                    - text:
-                        "LINE 6: End of test. Expected behavior: [BACK 1] goes to line 5 (score
-                        30), [BACK 2] goes to line 4 (score 15), etc."
-                  characterId: narrator

From 6aac44b8c8d959b50c825492e5fb7c1098f6f626 Mon Sep 17 00:00:00 2001
From: han4wluc <han4wluc@yuusoft.com>
Date: Mon, 30 Mar 2026 21:27:58 +0800
Subject: [PATCH 4/5] Derive rollback restore state from project defaults

---
 docs/Rollback.md                              |  5 +-
 docs/RollbackImplementationPlan.md            | 26 ++++++---
 spec/system/actions/loadSaveSlot.spec.yaml    | 11 ----
 spec/system/actions/nextLine.spec.yaml        |  6 ---
 .../actions/nextLineFromSystem.spec.yaml      |  4 --
 .../system/actions/rollbackByOffset.spec.yaml | 20 -------
 spec/system/actions/rollbackToLine.spec.yaml  | 25 ++-------
 spec/system/actions/saveSaveSlot.spec.yaml    |  8 ---
 .../actions/sectionTransition.spec.yaml       |  1 -
 spec/system/createInitialState.spec.yaml      | 10 ----
 .../selectors/selectLineIdByOffset.spec.yaml  |  3 --
 spec/systemStore.rollbackDraftSafety.test.js  | 53 ++++++++++++++-----
 src/stores/system.store.js                    | 44 +++++++++------
 13 files changed, 93 insertions(+), 123 deletions(-)

diff --git a/docs/Rollback.md b/docs/Rollback.md
index b934e844..aa3c0df4 100644
--- a/docs/Rollback.md
+++ b/docs/Rollback.md
@@ -241,6 +241,7 @@ The exact field names may differ, but the model should support:
 - ordered line checkpoints across section boundaries
 - replaying rollbackable story actions from timeline history
 - an array-index cursor for the current rollback position
+- deriving rollback start state from project-defined context variable defaults
 - a temporary restore guard for rollback reconstruction
 - future rollback policy expansion
 
@@ -265,7 +266,7 @@ The model is:
 
 - rollback timeline stores the visited line sequence
 - each entry identifies a visited line by `sectionId` and `lineId`
-- rollback restoration resets context-scoped story state to the context baseline
+- rollback restoration resets context-scoped story state to the default values of context-scoped variables from project data
 - the engine replays rollbackable story actions from the start of the timeline up to the target timeline index
 - presentation is then reconstructed from the resulting story state
 
@@ -274,6 +275,7 @@ This means:
 - presentation snapshots are never stored
 - context variable snapshots are not the source of truth
 - story state is derived from the rollback timeline
+- rollback state should not store a duplicate `baselineVariables` snapshot when the same start state can be derived from project data
 
 For now, replayability is based on line sequence plus rollbackable action classification.
 
@@ -338,6 +340,7 @@ That means:
 
 - saves must serialize the rollback timeline
 - saves must serialize the current rollback cursor
+- loads must recompute rollback start state from project-defined context variable defaults
 - loading a save must restore rollback ability from that saved point
 
 Compatibility behavior for older saves without rollback timeline should be defined during implementation.
diff --git a/docs/RollbackImplementationPlan.md b/docs/RollbackImplementationPlan.md
index f04e984c..2c838228 100644
--- a/docs/RollbackImplementationPlan.md
+++ b/docs/RollbackImplementationPlan.md
@@ -116,7 +116,7 @@ Specifically:
 - do not snapshot presentation
 - do not treat variable snapshots as the source of truth
 - on rollback:
-  - reset context variables to the context baseline
+  - reset context variables to the default values of context-scoped variables derived from project data
   - replay rollbackable story actions from the start of the timeline up to the target index
   - move `read` pointer to the target checkpoint
   - reconstruct presentation/render state from restored story state
@@ -183,6 +183,11 @@ rollback: {
 }
 ```
 
+Target model rule:
+
+- rollback state should not store a duplicate `baselineVariables` snapshot
+- restore start state should be derived on demand from project-defined defaults for context-scoped variables
+
 Checkpoint shape:
 
 ```js
@@ -367,7 +372,7 @@ Responsibilities:
 2. stop skip mode
 3. set `rollback.isRestoring = true`
 4. set `rollback.currentIndex`
-5. reset context variables to the context baseline
+5. reset context variables to the default values of context-scoped variables derived from project data
 6. replay rollbackable actions from `timeline[0..checkpointIndex]`
 7. restore `pointers.read`
 8. set `rollback.isRestoring = false`
@@ -459,7 +464,7 @@ So rollback should not attempt to store or restore:
 
 Instead:
 
-1. reset story state to the context baseline
+1. reset story state to the default values of context-scoped variables derived from project data
 2. replay rollbackable timeline entries up to target index
 3. restore pointer to target line
 4. queue normal render effects
@@ -537,10 +542,13 @@ Implementation requirement:
 - loading a save must restore both:
   - `rollback.timeline`
   - `rollback.currentIndex`
+- rollback save data should not store a duplicate `baselineVariables` snapshot
+- restore start state should be recomputed from project data after load
 
 Compatibility requirement:
 
 - define explicit behavior for older saves that do not contain rollback state
+- define whether older saves that still contain `baselineVariables` ignore that field or receive a one-time migration
 
 Recommended default:
 
@@ -589,6 +597,7 @@ Add or migrate tests for:
 15. `rollback.isRestoring` prevents duplicate checkpoint append
 16. `rollback.isRestoring` prevents duplicate `updateVariable` execution
 17. old-save compatibility initializes a minimal rollback timeline correctly
+18. rollback restore start state is derived from project defaults, not serialized baseline snapshots
 
 ### Regression tests for divergence
 
@@ -618,11 +627,12 @@ Recommended order:
 4. add branch truncation logic
 5. add `rollback.isRestoring` guard and restore helper
 6. implement replay-based rollback reconstruction from timeline start
-7. switch `rollbackByOffset` to new timeline
-8. switch UI-facing back flows to true rollback
-9. stop rollback logic from depending on `historySequence`
-10. update docs and tests
-11. evaluate whether `prevLine` / `history` pointer can be simplified or removed later
+7. derive rollback restore start state from project-defined context defaults instead of stored baseline snapshots
+8. switch `rollbackByOffset` to new timeline
+9. switch UI-facing back flows to true rollback
+10. stop rollback logic from depending on `historySequence`
+11. update docs and tests
+12. evaluate whether `prevLine` / `history` pointer can be simplified or removed later
 
 ## Risks
 
diff --git a/spec/system/actions/loadSaveSlot.spec.yaml b/spec/system/actions/loadSaveSlot.spec.yaml
index e65e4e54..67c313ee 100644
--- a/spec/system/actions/loadSaveSlot.spec.yaml
+++ b/spec/system/actions/loadSaveSlot.spec.yaml
@@ -45,7 +45,6 @@ out:
         currentIndex: 0
         isRestoring: false
         replayStartIndex: 1
-        baselineVariables: {}
         timeline:
           - sectionId: "sec2"
             lineId: "line2"
@@ -185,10 +184,6 @@ out:
         currentIndex: 0
         isRestoring: false
         replayStartIndex: 1
-        baselineVariables:
-          playerName: "Alice"
-          score: 150
-          soundEnabled: true
         timeline:
           - sectionId: "sec2"
             lineId: "line2"
@@ -218,8 +213,6 @@ in:
                     currentIndex: 2
                     isRestoring: false
                     replayStartIndex: 0
-                    baselineVariables:
-                      score: 0
                     timeline:
                       - sectionId: "sec1"
                         lineId: "line1"
@@ -254,8 +247,6 @@ out:
                 currentIndex: 2
                 isRestoring: false
                 replayStartIndex: 0
-                baselineVariables:
-                  score: 0
                 timeline:
                   - sectionId: "sec1"
                     lineId: "line1"
@@ -282,8 +273,6 @@ out:
         currentIndex: 2
         isRestoring: false
         replayStartIndex: 0
-        baselineVariables:
-          score: 0
         timeline:
           - sectionId: "sec1"
             lineId: "line1"
diff --git a/spec/system/actions/nextLine.spec.yaml b/spec/system/actions/nextLine.spec.yaml
index b185b947..1713cd16 100644
--- a/spec/system/actions/nextLine.spec.yaml
+++ b/spec/system/actions/nextLine.spec.yaml
@@ -184,7 +184,6 @@ out:
         currentIndex: 1
         isRestoring: false
         replayStartIndex: 1
-        baselineVariables: {}
         timeline:
           - sectionId: "section1"
             lineId: "1"
@@ -271,7 +270,6 @@ out:
         currentIndex: 1
         isRestoring: false
         replayStartIndex: 1
-        baselineVariables: {}
         timeline:
           - sectionId: "section1"
             lineId: "1"
@@ -351,7 +349,6 @@ out:
         currentIndex: 1
         isRestoring: false
         replayStartIndex: 1
-        baselineVariables: {}
         timeline:
           - sectionId: "section1"
             lineId: "1"
@@ -396,7 +393,6 @@ in:
             currentIndex: 1
             isRestoring: false
             replayStartIndex: 0
-            baselineVariables: {}
             timeline:
               - sectionId: "section1"
                 lineId: "1"
@@ -447,7 +443,6 @@ out:
         currentIndex: 2
         isRestoring: false
         replayStartIndex: 0
-        baselineVariables: {}
         timeline:
           - sectionId: "section1"
             lineId: "1"
@@ -815,7 +810,6 @@ out:
         currentIndex: 1
         isRestoring: false
         replayStartIndex: 1
-        baselineVariables: {}
         timeline:
           - sectionId: "section1"
             lineId: "1"
diff --git a/spec/system/actions/nextLineFromSystem.spec.yaml b/spec/system/actions/nextLineFromSystem.spec.yaml
index 322908fc..f87b8b71 100644
--- a/spec/system/actions/nextLineFromSystem.spec.yaml
+++ b/spec/system/actions/nextLineFromSystem.spec.yaml
@@ -108,7 +108,6 @@ out:
         currentIndex: 1
         isRestoring: false
         replayStartIndex: 1
-        baselineVariables: {}
         timeline:
           - sectionId: "section1"
             lineId: "1"
@@ -183,7 +182,6 @@ out:
         currentIndex: 1
         isRestoring: false
         replayStartIndex: 1
-        baselineVariables: {}
         timeline:
           - sectionId: "section1"
             lineId: "1"
@@ -259,7 +257,6 @@ out:
         currentIndex: 1
         isRestoring: false
         replayStartIndex: 1
-        baselineVariables: {}
         timeline:
           - sectionId: "section1"
             lineId: "1"
@@ -331,7 +328,6 @@ out:
         currentIndex: 1
         isRestoring: false
         replayStartIndex: 1
-        baselineVariables: {}
         timeline:
           - sectionId: "section1"
             lineId: "1"
diff --git a/spec/system/actions/rollbackByOffset.spec.yaml b/spec/system/actions/rollbackByOffset.spec.yaml
index 6c5bd4fb..f66157f0 100644
--- a/spec/system/actions/rollbackByOffset.spec.yaml
+++ b/spec/system/actions/rollbackByOffset.spec.yaml
@@ -72,7 +72,6 @@ in:
             currentIndex: 1
             isRestoring: false
             replayStartIndex: 0
-            baselineVariables: {}
             timeline:
               - sectionId: "section1"
                 lineId: "1"
@@ -123,7 +122,6 @@ out:
         currentIndex: 0
         isRestoring: false
         replayStartIndex: 0
-        baselineVariables: {}
         timeline:
           - sectionId: "section1"
             lineId: "1"
@@ -174,8 +172,6 @@ in:
             currentIndex: 2
             isRestoring: false
             replayStartIndex: 0
-            baselineVariables:
-              score: 0
             timeline:
               - sectionId: "section1"
                 lineId: "1"
@@ -242,8 +238,6 @@ out:
         currentIndex: 1
         isRestoring: false
         replayStartIndex: 0
-        baselineVariables:
-          score: 0
         timeline:
           - sectionId: "section1"
             lineId: "1"
@@ -288,8 +282,6 @@ in:
             currentIndex: 0
             isRestoring: false
             replayStartIndex: 0
-            baselineVariables:
-              score: 0
             timeline:
               - sectionId: "section1"
                 lineId: "1"
@@ -326,8 +318,6 @@ out:
         currentIndex: 0
         isRestoring: false
         replayStartIndex: 0
-        baselineVariables:
-          score: 0
         timeline:
           - sectionId: "section1"
             lineId: "1"
@@ -382,8 +372,6 @@ in:
             currentIndex: 3
             isRestoring: false
             replayStartIndex: 0
-            baselineVariables:
-              score: 0
             timeline:
               - sectionId: "section1"
                 lineId: "1"
@@ -460,8 +448,6 @@ out:
         currentIndex: 2
         isRestoring: false
         replayStartIndex: 0
-        baselineVariables:
-          score: 0
         timeline:
           - sectionId: "section1"
             lineId: "1"
@@ -542,8 +528,6 @@ in:
             currentIndex: 2
             isRestoring: false
             replayStartIndex: 0
-            baselineVariables:
-              score: 0
             timeline:
               - sectionId: "section1"
                 lineId: "1"
@@ -624,8 +608,6 @@ out:
         currentIndex: 1
         isRestoring: false
         replayStartIndex: 0
-        baselineVariables:
-          score: 0
         timeline:
           - sectionId: "section1"
             lineId: "1"
@@ -680,7 +662,6 @@ in:
             currentIndex: 2
             isRestoring: false
             replayStartIndex: 0
-            baselineVariables: {}
             timeline:
               - sectionId: "section1"
                 lineId: "1"
@@ -743,7 +724,6 @@ out:
         currentIndex: 1
         isRestoring: false
         replayStartIndex: 0
-        baselineVariables: {}
         timeline:
           - sectionId: "section1"
             lineId: "1"
diff --git a/spec/system/actions/rollbackToLine.spec.yaml b/spec/system/actions/rollbackToLine.spec.yaml
index 2ee0ab96..36d2ba52 100644
--- a/spec/system/actions/rollbackToLine.spec.yaml
+++ b/spec/system/actions/rollbackToLine.spec.yaml
@@ -57,8 +57,6 @@ in:
             currentIndex: 3
             isRestoring: false
             replayStartIndex: 0
-            baselineVariables:
-              score: 0
             timeline:
               - sectionId: "section1"
                 lineId: "1"
@@ -137,8 +135,6 @@ out:
         currentIndex: 2
         isRestoring: false
         replayStartIndex: 0
-        baselineVariables:
-          score: 0
         timeline:
           - sectionId: "section1"
             lineId: "1"
@@ -206,8 +202,6 @@ in:
             currentIndex: 2
             isRestoring: false
             replayStartIndex: 0
-            baselineVariables:
-              score: 0
             timeline:
               - sectionId: "section1"
                 lineId: "1"
@@ -284,8 +278,6 @@ out:
         currentIndex: 1
         isRestoring: false
         replayStartIndex: 0
-        baselineVariables:
-          score: 0
         timeline:
           - sectionId: "section1"
             lineId: "1"
@@ -320,7 +312,6 @@ in:
             currentIndex: 1
             isRestoring: false
             replayStartIndex: 0
-            baselineVariables: {}
             timeline:
               - sectionId: "section1"
                 lineId: "1"
@@ -377,8 +368,6 @@ in:
             currentIndex: 2
             isRestoring: false
             replayStartIndex: 0
-            baselineVariables:
-              score: 0
             timeline:
               - sectionId: "section1"
                 lineId: "1"
@@ -449,8 +438,6 @@ out:
         currentIndex: 1
         isRestoring: false
         replayStartIndex: 0
-        baselineVariables:
-          score: 0
         timeline:
           - sectionId: "section1"
             lineId: "1"
@@ -462,7 +449,7 @@ out:
             lineId: "3"
             rollbackPolicy: "free"
 ---
-case: rollback to first line resets to baseline when first checkpoint has no rollbackable actions
+case: rollback to first line resets to context defaults when first checkpoint has no rollbackable actions
 in:
   - state:
       projectData:
@@ -486,7 +473,7 @@ in:
             score:
               type: number
               scope: context
-              default: 0
+              default: 10
       global:
         isLineCompleted: false
         pendingEffects: []
@@ -503,8 +490,6 @@ in:
             currentIndex: 1
             isRestoring: false
             replayStartIndex: 0
-            baselineVariables:
-              score: 10
             timeline:
               - sectionId: "section1"
                 lineId: "1"
@@ -536,7 +521,7 @@ out:
         score:
           type: number
           scope: context
-          default: 0
+          default: 10
   global:
     isLineCompleted: true
     dialogueUIHidden: false
@@ -568,8 +553,6 @@ out:
         currentIndex: 0
         isRestoring: false
         replayStartIndex: 0
-        baselineVariables:
-          score: 10
         timeline:
           - sectionId: "section1"
             lineId: "1"
@@ -621,7 +604,6 @@ in:
             currentIndex: 2
             isRestoring: false
             replayStartIndex: 0
-            baselineVariables: {}
             timeline:
               - sectionId: "section1"
                 lineId: "1"
@@ -690,7 +672,6 @@ out:
         currentIndex: 1
         isRestoring: false
         replayStartIndex: 0
-        baselineVariables: {}
         timeline:
           - sectionId: "section1"
             lineId: "1"
diff --git a/spec/system/actions/saveSaveSlot.spec.yaml b/spec/system/actions/saveSaveSlot.spec.yaml
index fb3067af..0fd0c945 100644
--- a/spec/system/actions/saveSaveSlot.spec.yaml
+++ b/spec/system/actions/saveSaveSlot.spec.yaml
@@ -281,8 +281,6 @@ in:
             currentIndex: 2
             isRestoring: false
             replayStartIndex: 0
-            baselineVariables:
-              score: 0
             timeline:
               - sectionId: "sec1"
                 lineId: "line1"
@@ -312,8 +310,6 @@ out:
                 currentIndex: 2
                 isRestoring: false
                 replayStartIndex: 0
-                baselineVariables:
-                  score: 0
                 timeline:
                   - sectionId: "sec1"
                     lineId: "line1"
@@ -343,8 +339,6 @@ out:
                       currentIndex: 2
                       isRestoring: false
                       replayStartIndex: 0
-                      baselineVariables:
-                        score: 0
                       timeline:
                         - sectionId: "sec1"
                           lineId: "line1"
@@ -368,8 +362,6 @@ out:
         currentIndex: 2
         isRestoring: false
         replayStartIndex: 0
-        baselineVariables:
-          score: 0
         timeline:
           - sectionId: "sec1"
             lineId: "line1"
diff --git a/spec/system/actions/sectionTransition.spec.yaml b/spec/system/actions/sectionTransition.spec.yaml
index 2651375e..a321e366 100644
--- a/spec/system/actions/sectionTransition.spec.yaml
+++ b/spec/system/actions/sectionTransition.spec.yaml
@@ -74,7 +74,6 @@ out:
         currentIndex: 1
         isRestoring: false
         replayStartIndex: 1
-        baselineVariables: {}
         timeline:
           - sectionId: "section1"
             lineId: "1"
diff --git a/spec/system/createInitialState.spec.yaml b/spec/system/createInitialState.spec.yaml
index d2f5423e..46cdaf6d 100644
--- a/spec/system/createInitialState.spec.yaml
+++ b/spec/system/createInitialState.spec.yaml
@@ -75,7 +75,6 @@ out:
         currentIndex: 0
         isRestoring: false
         replayStartIndex: 0
-        baselineVariables: {}
         timeline:
           - sectionId: "section1"
             lineId: "line1"
@@ -192,11 +191,6 @@ out:
         currentIndex: 0
         isRestoring: false
         replayStartIndex: 0
-        baselineVariables:
-          inventory:
-            items:
-              - id: sword
-                name: Steel Sword
         timeline:
           - sectionId: "section1"
             lineId: "line1"
@@ -288,8 +282,6 @@ out:
         currentIndex: 0
         isRestoring: false
         replayStartIndex: 0
-        baselineVariables:
-          settings: {}
         timeline:
           - sectionId: "section1"
             lineId: "line1"
@@ -401,7 +393,6 @@ out:
         currentIndex: 0
         isRestoring: false
         replayStartIndex: 0
-        baselineVariables: {}
         timeline:
           - sectionId: "section1"
             lineId: "line1"
@@ -484,7 +475,6 @@ out:
         currentIndex: 0
         isRestoring: false
         replayStartIndex: 0
-        baselineVariables: {}
         timeline:
           - sectionId: "section1"
             lineId: "line2"
diff --git a/spec/system/selectors/selectLineIdByOffset.spec.yaml b/spec/system/selectors/selectLineIdByOffset.spec.yaml
index 084abac9..7b9dc2cc 100644
--- a/spec/system/selectors/selectLineIdByOffset.spec.yaml
+++ b/spec/system/selectors/selectLineIdByOffset.spec.yaml
@@ -19,7 +19,6 @@ in:
             currentIndex: 2
             isRestoring: false
             replayStartIndex: 0
-            baselineVariables: {}
             timeline:
               - sectionId: "section1"
                 lineId: "1"
@@ -49,7 +48,6 @@ in:
             currentIndex: 0
             isRestoring: false
             replayStartIndex: 0
-            baselineVariables: {}
             timeline:
               - sectionId: "section1"
                 lineId: "1"
@@ -71,7 +69,6 @@ in:
             currentIndex: 3
             isRestoring: false
             replayStartIndex: 0
-            baselineVariables: {}
             timeline:
               - sectionId: "section1"
                 lineId: "1"
diff --git a/spec/systemStore.rollbackDraftSafety.test.js b/spec/systemStore.rollbackDraftSafety.test.js
index 4af94dbd..778e9ee8 100644
--- a/spec/systemStore.rollbackDraftSafety.test.js
+++ b/spec/systemStore.rollbackDraftSafety.test.js
@@ -156,9 +156,6 @@ describe("system.store rollback/save draft safety", () => {
             currentIndex: 1,
             isRestoring: false,
             replayStartIndex: 0,
-            baselineVariables: {
-              score: 0,
-            },
             timeline: [
               {
                 sectionId: "section1",
@@ -182,7 +179,23 @@ describe("system.store rollback/save draft safety", () => {
 
     expect(
       nextState.global.saveSlots["1"]?.state?.contexts?.[0]?.rollback,
-    ).toEqual(baseState.contexts[0].rollback);
+    ).toEqual({
+      currentIndex: 1,
+      isRestoring: false,
+      replayStartIndex: 0,
+      timeline: [
+        {
+          sectionId: "section1",
+          lineId: "1",
+          rollbackPolicy: "free",
+        },
+        {
+          sectionId: "section1",
+          lineId: "2",
+          rollbackPolicy: "free",
+        },
+      ],
+    });
     vi.restoreAllMocks();
   });
 
@@ -261,7 +274,28 @@ describe("system.store rollback/save draft safety", () => {
       loadSaveSlot({ state: draft }, { slot: 1 });
     });
 
-    expect(nextState.contexts[0].rollback).toEqual(savedRollback);
+    expect(nextState.contexts[0].rollback).toEqual({
+      currentIndex: 2,
+      isRestoring: false,
+      replayStartIndex: 0,
+      timeline: [
+        {
+          sectionId: "section1",
+          lineId: "1",
+          rollbackPolicy: "free",
+        },
+        {
+          sectionId: "section1",
+          lineId: "2",
+          rollbackPolicy: "free",
+        },
+        {
+          sectionId: "section2",
+          lineId: "10",
+          rollbackPolicy: "free",
+        },
+      ],
+    });
     expect(nextState.global.viewedRegistry.sections[0]).toEqual({
       sectionId: "section2",
       lastLineId: "10",
@@ -306,9 +340,6 @@ describe("system.store rollback/save draft safety", () => {
             currentIndex: 2,
             isRestoring: false,
             replayStartIndex: 0,
-            baselineVariables: {
-              score: 0,
-            },
             timeline: [
               {
                 sectionId: "section1",
@@ -390,9 +421,6 @@ describe("system.store rollback/save draft safety", () => {
             currentIndex: 1,
             isRestoring: false,
             replayStartIndex: 0,
-            baselineVariables: {
-              score: 0,
-            },
             timeline: [
               {
                 sectionId: "section1",
@@ -482,9 +510,6 @@ describe("system.store rollback/save draft safety", () => {
             currentIndex: 2,
             isRestoring: false,
             replayStartIndex: 0,
-            baselineVariables: {
-              score: 0,
-            },
             timeline: [
               {
                 sectionId: "section1",
diff --git a/src/stores/system.store.js b/src/stores/system.store.js
index 417e9b0d..9314c708 100644
--- a/src/stores/system.store.js
+++ b/src/stores/system.store.js
@@ -58,18 +58,28 @@ const createRollbackCheckpoint = ({ sectionId, lineId, rollbackPolicy }) => ({
   rollbackPolicy: rollbackPolicy ?? "free",
 });
 
-const createRollbackState = ({
-  pointer,
-  baselineVariables,
-  replayStartIndex = 0,
-}) => {
+const getRollbackContextVariableDefaults = (projectData) => {
+  const { contextVariableDefaultValues } = getDefaultVariablesFromProjectData(
+    projectData ?? {},
+  );
+  return cloneStateValue(contextVariableDefaultValues);
+};
+
+const removeLegacyRollbackBaseline = (rollback) => {
+  if (!rollback || !("baselineVariables" in rollback)) {
+    return;
+  }
+
+  delete rollback.baselineVariables;
+};
+
+const createRollbackState = ({ pointer, replayStartIndex = 0 }) => {
   const hasInitialPointer = pointer?.sectionId && pointer?.lineId;
 
   return {
     currentIndex: hasInitialPointer ? 0 : -1,
     isRestoring: false,
     replayStartIndex,
-    baselineVariables: cloneStateValue(baselineVariables ?? {}),
     timeline: hasInitialPointer
       ? [
           createRollbackCheckpoint({
@@ -83,6 +93,7 @@ const createRollbackState = ({
 
 const ensureRollbackState = (lastContext, options = {}) => {
   if (lastContext?.rollback) {
+    removeLegacyRollbackBaseline(lastContext.rollback);
     if (!Array.isArray(lastContext.rollback.timeline)) {
       lastContext.rollback.timeline = [];
     }
@@ -98,18 +109,12 @@ const ensureRollbackState = (lastContext, options = {}) => {
     if (typeof lastContext.rollback.replayStartIndex !== "number") {
       lastContext.rollback.replayStartIndex = 0;
     }
-    if (lastContext.rollback.baselineVariables === undefined) {
-      lastContext.rollback.baselineVariables = cloneStateValue(
-        lastContext.variables ?? {},
-      );
-    }
     return lastContext.rollback;
   }
 
   const pointer = lastContext?.pointers?.read;
   lastContext.rollback = createRollbackState({
     pointer,
-    baselineVariables: lastContext?.variables ?? {},
     replayStartIndex: options.compatibilityAnchor ? 1 : 0,
   });
   return lastContext.rollback;
@@ -379,7 +384,9 @@ const restoreRollbackCheckpoint = (state, checkpointIndex) => {
   rollback.currentIndex = checkpointIndex;
 
   try {
-    lastContext.variables = cloneStateValue(rollback.baselineVariables ?? {});
+    lastContext.variables = getRollbackContextVariableDefaults(
+      state.projectData,
+    );
     state.global.dialogueUIHidden = false;
     state.global.isDialogueHistoryShowing = false;
     state.global.nextLineConfig = cloneStateValue(DEFAULT_NEXT_LINE_CONFIG);
@@ -499,7 +506,6 @@ export const createInitialState = (payload) => {
         variables: contextVariableDefaultValues,
         rollback: createRollbackState({
           pointer: initialPointer,
-          baselineVariables: contextVariableDefaultValues,
         }),
       },
     ],
@@ -1343,9 +1349,13 @@ export const setNextLineConfig = ({ state }, payload) => {
 export const saveSaveSlot = ({ state }, payload) => {
   const { slot, thumbnailImage } = payload;
   const slotKey = String(slot);
+  const contexts = cloneStateValue(state.contexts);
+  contexts?.forEach((context) => {
+    removeLegacyRollbackBaseline(context.rollback);
+  });
 
   const currentState = {
-    contexts: cloneStateValue(state.contexts),
+    contexts,
     viewedRegistry: cloneStateValue(state.global.viewedRegistry),
   };
 
@@ -2225,6 +2235,10 @@ export const rollbackToLine = ({ state }, payload) => {
     );
   }
 
+  if (targetLineIndex === rollback.currentIndex) {
+    return state;
+  }
+
   return restoreRollbackCheckpoint(state, targetLineIndex);
 };
 

From cc658a30d14aab3ce419b7631792490627fb0b1a Mon Sep 17 00:00:00 2001
From: han4wluc <han4wluc@yuusoft.com>
Date: Mon, 30 Mar 2026 21:59:50 +0800
Subject: [PATCH 5/5] Support NVL loop layouts and refresh VT baselines

---
 docs/vt-guidelines.md                         |   1 +
 package.json                                  |   2 +-
 spec/system/renderState/addDialogue.spec.yaml |  42 ++++-
 src/stores/constructRenderState.js            | 145 +++++++++++++++---
 .../completion-text-animation-choice-01.webp  |   4 +-
 .../rollback/auto-suppressed--capture-01.webp |   4 +-
 .../rollback/back-one-line--capture-01.webp   |   4 +-
 .../rollback/choice-event--capture-01.webp    |   4 +-
 .../rollback/cross-section--capture-01.webp   |   4 +-
 .../layered-view-restore--capture-01.webp     |   4 +-
 .../rollback/to-line--capture-01.webp         |   4 +-
 11 files changed, 180 insertions(+), 38 deletions(-)

diff --git a/docs/vt-guidelines.md b/docs/vt-guidelines.md
index 492d2b22..8e6567d5 100644
--- a/docs/vt-guidelines.md
+++ b/docs/vt-guidelines.md
@@ -28,6 +28,7 @@ Define one stable standard for VT authoring in this repo:
 - Accept an intentional visual change with `rtgl vt accept`.
 - If the sync step needs a different upstream build, point `VT_ROUTE_GRAPHICS_URL` at the desired CDN file.
 - Local VT defaults to `2` Docker workers and a `60000ms` timeout.
+- Local VT reports default to a `0.8%` diff threshold to tolerate small Docker text raster drift.
 - VT is currently local-only. GitHub Actions VT is disabled again until the runner instability is fixed separately.
 
 ## Visual Standard
diff --git a/package.json b/package.json
index ee6e121e..52f4f8a1 100644
--- a/package.json
+++ b/package.json
@@ -42,7 +42,7 @@
     "vt:sync-route-graphics": "bun scripts/sync-vt-route-graphics.js",
     "vt:generate": "bun scripts/sync-vt-route-graphics.js && bun run esbuild.js && rtgl vt generate",
     "vt:docker": "bun scripts/sync-vt-route-graphics.js && bun run esbuild.js && docker run --rm ${VT_DOCKER_ARGS:-} --user $(id -u):$(id -g) -e RTGL_VT_DEBUG=true -v \"$PWD:/app\" -w /app docker.io/han4wluc/rtgl:playwright-v1.57.0-rtgl-v1.0.10 rtgl vt screenshot --wait-event vt:ready --concurrency ${VT_DOCKER_CONCURRENCY:-2} --timeout ${VT_DOCKER_TIMEOUT:-60000}",
-    "vt:report": "bun run vt:docker && rtgl vt report",
+    "vt:report": "bun run vt:docker && rtgl vt report --diff-threshold ${VT_REPORT_DIFF_THRESHOLD:-0.8}",
     "vt:accept": "rtgl vt accept",
     "serve": "bun run esbuild.js && bunx serve -p 3004 .rettangoli/vt/_site"
   },
diff --git a/spec/system/renderState/addDialogue.spec.yaml b/spec/system/renderState/addDialogue.spec.yaml
index 5e1bcccb..6b632fbb 100644
--- a/spec/system/renderState/addDialogue.spec.yaml
+++ b/spec/system/renderState/addDialogue.spec.yaml
@@ -94,7 +94,18 @@ in:
           elements:
             - id: "nvl-container"
               type: "container"
-              children: []
+              children:
+                - $for line, i in dialogueLines:
+                    - id: "line-${i}"
+                      type: "container"
+                      children:
+                        - $if line.characterName:
+                            - id: "name-${i}"
+                              type: "text"
+                              content: "${line.characterName}"
+                        - id: "text-${i}"
+                          type: "text"
+                          content: "${line.content[0].text}"
       characters:
         narrator:
           name: "Narrator"
@@ -114,7 +125,34 @@ out:
       children:
         - id: "nvl-container"
           type: "container"
-          children: []
+          children:
+            - id: "line-0"
+              type: "container"
+              children:
+                - id: "name-0"
+                  type: "text"
+                  content: "Narrator"
+                - id: "text-0"
+                  type: "text"
+                  content: "First line"
+            - id: "line-1"
+              type: "container"
+              children:
+                - id: "name-1"
+                  type: "text"
+                  content: "Alice"
+                - id: "text-1"
+                  type: "text"
+                  content: "Second line"
+            - id: "line-2"
+              type: "container"
+              children:
+                - id: "name-2"
+                  type: "text"
+                  content: "Bob"
+                - id: "text-2"
+                  type: "text"
+                  content: "Third line"
   animations: []
 ---
 case: resolves textStyleId in dialogue ui layout elements
diff --git a/src/stores/constructRenderState.js b/src/stores/constructRenderState.js
index 7e5e9189..baa6b6f0 100644
--- a/src/stores/constructRenderState.js
+++ b/src/stores/constructRenderState.js
@@ -7,6 +7,99 @@ const jemplFunctions = {
   formatDate,
 };
 
+const LOOP_DIRECTIVE_RE =
+  /^\$for\s+([A-Za-z_][A-Za-z0-9_]*)(?:\s*,\s*([A-Za-z_][A-Za-z0-9_]*))?\s+in\s+(.+):$/;
+
+const resolveTemplatePath = (data, expression) => {
+  const normalized = String(expression || "").trim();
+  if (!normalized) {
+    return undefined;
+  }
+
+  const parts = normalized.match(/[A-Za-z_][A-Za-z0-9_]*|\[\d+\]/g) || [];
+  let current = data;
+  for (const part of parts) {
+    if (part.startsWith("[")) {
+      const index = Number(part.slice(1, -1));
+      current = Array.isArray(current) ? current[index] : undefined;
+      continue;
+    }
+    current = current?.[part];
+  }
+  return current;
+};
+
+const expandLoopTemplates = (node, templateData, options) => {
+  if (Array.isArray(node)) {
+    const expanded = [];
+
+    for (const item of node) {
+      if (
+        item &&
+        typeof item === "object" &&
+        !Array.isArray(item) &&
+        Object.keys(item).length === 1
+      ) {
+        const [maybeLoopKey] = Object.keys(item);
+        const loopMatch = LOOP_DIRECTIVE_RE.exec(maybeLoopKey);
+        if (loopMatch) {
+          const [, itemName, indexName, sourceExpression] = loopMatch;
+          const iterable = resolveTemplatePath(templateData, sourceExpression);
+          if (!Array.isArray(iterable)) {
+            continue;
+          }
+
+          const loopTemplate = Array.isArray(item[maybeLoopKey])
+            ? item[maybeLoopKey]
+            : [];
+          iterable.forEach((loopItem, loopIndex) => {
+            const loopData = {
+              ...templateData,
+              [itemName]: loopItem,
+            };
+            if (indexName) {
+              loopData[indexName] = loopIndex;
+            }
+
+            loopTemplate.forEach((loopNode) => {
+              const expandedLoopNode = expandLoopTemplates(
+                loopNode,
+                loopData,
+                options,
+              );
+              const rendered = parseAndRender(
+                expandedLoopNode,
+                loopData,
+                options,
+              );
+              if (Array.isArray(rendered)) {
+                expanded.push(...rendered);
+              } else {
+                expanded.push(rendered);
+              }
+            });
+          });
+          continue;
+        }
+      }
+
+      expanded.push(expandLoopTemplates(item, templateData, options));
+    }
+
+    return expanded;
+  }
+
+  if (!node || typeof node !== "object") {
+    return node;
+  }
+
+  const expanded = {};
+  Object.entries(node).forEach(([key, value]) => {
+    expanded[key] = expandLoopTemplates(value, templateData, options);
+  });
+  return expanded;
+};
+
 const LEGACY_ANIMATION_TYPE_MAP = {
   live: "update",
   replace: "transition",
@@ -1504,6 +1597,24 @@ export const addDialogue = (
               presentationState.dialogue.content,
               "dialogue.content",
             );
+      const dialogueLines = (presentationState.dialogue?.lines || []).map(
+        (line, index) => {
+          const lineContent = ensureDialogueContentItems(
+            line.content,
+            `dialogue.lines[${index}].content`,
+          );
+
+          return {
+            content: lineContent.map((item) => ({
+              ...item,
+              text: interpolateDialogueText(item.text, { variables }),
+            })),
+            characterName: line.characterId
+              ? resources.characters?.[line.characterId]?.name || ""
+              : "",
+          };
+        },
+      );
 
       const templateData = {
         variables,
@@ -1517,6 +1628,7 @@ export const addDialogue = (
           ? 0
           : (variables?._soundVolume ?? 500),
         textSpeed: variables?._textSpeed ?? 50,
+        dialogueLines,
         dialogue: {
           character: {
             name: character?.name || "",
@@ -1525,30 +1637,21 @@ export const addDialogue = (
             ...item,
             text: interpolateDialogueText(item.text, { variables }),
           })),
-          lines: (presentationState.dialogue?.lines || []).map(
-            (line, index) => {
-              const lineContent = ensureDialogueContentItems(
-                line.content,
-                `dialogue.lines[${index}].content`,
-              );
-
-              return {
-                content: lineContent.map((item) => ({
-                  ...item,
-                  text: interpolateDialogueText(item.text, { variables }),
-                })),
-                characterName: line.characterId
-                  ? resources.characters?.[line.characterId]?.name || ""
-                  : "",
-              };
-            },
-          ),
+          lines: dialogueLines,
         },
       };
 
-      const result = parseAndRender(wrappedTemplate, templateData, {
-        functions: jemplFunctions,
-      });
+      const renderOptions = { functions: jemplFunctions };
+      const expandedTemplate = expandLoopTemplates(
+        wrappedTemplate,
+        templateData,
+        renderOptions,
+      );
+      const result = parseAndRender(
+        expandedTemplate,
+        templateData,
+        renderOptions,
+      );
       const uiElements = resolveLayoutResourceIds(
         settleTextRevealIfCompleted(result?.elements, {
           isLineCompleted,
diff --git a/vt/reference/nextLineConfig/completion-text-animation-choice-01.webp b/vt/reference/nextLineConfig/completion-text-animation-choice-01.webp
index 154369ef..f8e861d2 100644
--- a/vt/reference/nextLineConfig/completion-text-animation-choice-01.webp
+++ b/vt/reference/nextLineConfig/completion-text-animation-choice-01.webp
@@ -1,3 +1,3 @@
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