loro-dev · lodystage · Jul 30, 2026 · Jul 30, 2026
diff --git a/AGENTS.md b/AGENTS.md
@@ -35,10 +35,9 @@
 - App-server events: prefer `thread/*`, `turn/*`, and `item/*` event surfaces; avoid the deprecated `codex/event/*` API (planned removal). Keep implementations aligned with generated types in `src/app-server` (including `v2` exports).
 - Steer uses app-server `turn/steer` on the tracked active turn. Correlate `clientUserMessageId` and acknowledge only the matching `item/completed(userMessage)`; never emulate steer with a second `turn/start`.
 - Session fork uses app-server `thread/fork` and installs the returned child as an independent ACP
-  session. The temporary `_meta.lody.forkAtMessage` extension carries a standard ACP `messageId`;
-  resolve the containing Codex turn with `thread/read` inside this adapter before setting
-  `thread/fork.lastTurnId`. Never expose Codex turn IDs as ACP message IDs or emulate fork by
-  replaying source history.
+  session. Agent message updates expose their Codex turn id as `_meta.lody.turnId`;
+  `_meta.lody.forkAtTurn.turnId` is passed directly to `thread/fork.lastTurnId`. Do not maintain
+  a message-id mapping or emulate fork by replaying source history.
 - Codex reasoning summaries can echo trailing empty HTML comments from model instructions. Keep
   that provider-specific cleanup in `src/ReasoningText.ts` across live deltas and history replay;
   do not filter assistant text, raw reasoning, or HTML globally in the client renderer.

diff --git a/src/AcpExtensions.ts b/src/AcpExtensions.ts
@@ -12,19 +12,16 @@ export const ACP_EXT_SESSION_USAGE_UPDATE_METHOD = "_acp_ext:session_usage_updat
 export const ACP_EXT_SESSION_RATE_LIMITS_METHOD = "_acp_ext:session_rate_limits";
 export const ACP_EXT_CODEX_PROPOSED_PLAN_METHOD = "_acp_ext:codex_proposed_plan";
 export const CODEX_STEER_APPLIED_METHOD = "_codex/steerApplied";
-export const LODY_FORK_MESSAGE_BEFORE_ACTIVE_TURN_METHOD =
-    "_lody/session/fork-message-before-active-turn";
-
-export function getLodyForkMessageId(meta: unknown): string | null {
+export function getLodyForkTurnId(meta: unknown): string | null {
     if (typeof meta !== "object" || meta === null) return null;
     const lody = (meta as Record<string, unknown>)["lody"];
     if (typeof lody !== "object" || lody === null) return null;
-    const forkAtMessage = (lody as Record<string, unknown>)["forkAtMessage"];
-    if (typeof forkAtMessage !== "object" || forkAtMessage === null) return null;
-    const version = (forkAtMessage as Record<string, unknown>)["version"];
-    const messageId = (forkAtMessage as Record<string, unknown>)["messageId"];
-    return version === 1 && typeof messageId === "string" && messageId.length > 0
-        ? messageId
+    const forkAtTurn = (lody as Record<string, unknown>)["forkAtTurn"];
+    if (typeof forkAtTurn !== "object" || forkAtTurn === null) return null;
+    const version = (forkAtTurn as Record<string, unknown>)["version"];
+    const turnId = (forkAtTurn as Record<string, unknown>)["turnId"];
+    return version === 1 && typeof turnId === "string" && turnId.length > 0
+        ? turnId
         : null;
 }
 

diff --git a/src/CodexAcpClient.ts b/src/CodexAcpClient.ts
@@ -23,7 +23,7 @@ import {AgentMode} from "./AgentMode";
 import path from "node:path";
 import {logger} from "./Logger";
 import {sanitizeMcpServerName} from "./McpServerName";
-import {getLodyForkMessageId} from "./AcpExtensions";
+import {getLodyForkTurnId} from "./AcpExtensions";
 import type {
     AccountLoginCompletedNotification,
     AccountUpdatedNotification,
@@ -356,10 +356,7 @@ export class CodexAcpClient {
     ): Promise<SessionMetadata> {
         const additionalDirectories = readAdditionalDirectories(request.cwd, request.additionalDirectories, request._meta);
         await this.refreshSkills(request.cwd, additionalDirectories);
-        const forkMessageId = getLodyForkMessageId(request._meta);
-        const forkTurnId = forkMessageId
-            ? await this.resolveForkTurnIdForMessage(request.sessionId, forkMessageId)
-            : null;
+        const forkTurnId = getLodyForkTurnId(request._meta);
 
         const response = await this.codexClient.threadFork({
             config: await this.createSessionConfig(request.cwd, additionalDirectories, request.mcpServers ?? []),
@@ -382,44 +379,6 @@ export class CodexAcpClient {
         };
     }
 
-    async resolveForkTurnIdForMessage(threadId: string, messageId: string): Promise<string> {
-        const response = await this.codexClient.threadRead({
-            threadId,
-            includeTurns: true,
-        });
-        const turn = response.thread.turns.find((candidate) =>
-            candidate.items.some((item) => item.type === "agentMessage" && item.id === messageId)
-        );
-        if (!turn) {
-            throw RequestError.invalidRequest("ACP message is not a forkable Codex turn boundary");
-        }
-        return turn.id;
-    }
-
-    async findMessageBeforeTurn(threadId: string, activeTurnId: string): Promise<string> {
-        const response = await this.codexClient.threadRead({
-            threadId,
-            includeTurns: true,
-        });
-        const turns = response.thread.turns;
-        const activeIndex = turns.findIndex((turn) => turn.id === activeTurnId);
-        if (activeIndex < 0) {
-            throw RequestError.invalidRequest("Active turn changed before its preceding message was captured");
-        }
-        for (let index = activeIndex - 1; index >= 0; index--) {
-            const turn = turns[index];
-            if (turn && turn.status !== "inProgress") {
-                const agentMessage = [...turn.items]
-                    .reverse()
-                    .find((item) => item.type === "agentMessage");
-                if (agentMessage) {
-                    return agentMessage.id;
-                }
-            }
-        }
-        throw RequestError.invalidRequest("No completed assistant message exists before the active turn");
-    }
-
     async loadSession(request: acp.LoadSessionRequest, onSubscribed?: () => void): Promise<SessionMetadataWithThread> {
         const additionalDirectories = readAdditionalDirectories(request.cwd, request.additionalDirectories, request._meta);
         await this.refreshSkills(request.cwd, additionalDirectories);

diff --git a/src/CodexAcpServer.ts b/src/CodexAcpServer.ts
@@ -47,7 +47,6 @@ import {
     getCodexSteerId,
     isExtMethodRequest,
     LEGACY_SET_SESSION_MODEL_METHOD,
-    LODY_FORK_MESSAGE_BEFORE_ACTIVE_TURN_METHOD,
 } from "./AcpExtensions";
 import {
     createCollabAgentToolCallUpdate,
@@ -81,7 +80,7 @@ import {isJetBrains2026_1Client} from "./JBUtils";
 import {resolveTerminalOutputMode, type TerminalOutputMode} from "./TerminalOutputMode";
 import {sanitizeReasoningParts} from "./ReasoningText";
 import {
-    createCodexMessagePhaseMeta,
+    createCodexAgentMessageMeta,
     createAgentTextMessageChunk,
     createAgentTextThoughtChunk,
     createUserMessageChunk,
@@ -268,7 +267,7 @@ export class CodexAcpServer {
                         steer: CODEX_STEER_CAPABILITY,
                     },
                     lody: {
-                        forkAtMessage: {version: 1, beforeActiveTurn: true},
+                        forkAtTurn: {version: 1},
                     },
                 },
             },
@@ -669,22 +668,6 @@ export class CodexAcpServer {
         };
     }
 
-    async resolveMessageBeforeActiveTurn(params: {sessionId: string}): Promise<{messageId: string}> {
-        const session = this.sessions.get(params.sessionId);
-        const activeTurnId = session?.currentTurnId;
-        if (!activeTurnId) {
-            throw RequestError.invalidRequest("Session has no active turn");
-        }
-        const messageId = await this.runWithProcessCheck(() =>
-            this.codexAcpClient.findMessageBeforeTurn(params.sessionId, activeTurnId)
-        );
-        logger.log("Resolved ACP message before active turn", {
-            sessionId: params.sessionId,
-            method: LODY_FORK_MESSAGE_BEFORE_ACTIVE_TURN_METHOD,
-        });
-        return {messageId};
-    }
-
     async listSessions(params: acp.ListSessionsRequest): Promise<acp.ListSessionsResponse> {
         logger.log("Listing sessions...", {cwd: params.cwd, cursor: params.cursor});
         await this.checkAuthorization();
@@ -1205,7 +1188,7 @@ export class CodexAcpServer {
         const threadUpdates: UpdateSessionEvent[] = [];
         for (const turn of thread.turns) {
             for (const item of turn.items) {
-                const updates = await this.createHistoryUpdates(item, sessionState);
+                const updates = await this.createHistoryUpdates(item, sessionState, turn.id);
                 threadUpdates.push(...updates);
             }
         }
@@ -1279,7 +1262,11 @@ export class CodexAcpServer {
         return normalized.length > 0 ? normalized : null;
     }
 
-    private async createHistoryUpdates(item: ThreadItem, sessionState: SessionState): Promise<UpdateSessionEvent[]> {
+    private async createHistoryUpdates(
+        item: ThreadItem,
+        sessionState: SessionState,
+        turnId: string,
+    ): Promise<UpdateSessionEvent[]> {
         switch (item.type) {
             case "userMessage":
                 return this.createUserMessageUpdates(item);
@@ -1288,12 +1275,11 @@ export class CodexAcpServer {
             case "sleep":
                 return [];
             case "agentMessage": {
-                const meta = createCodexMessagePhaseMeta(item.phase);
                 return [{
                     sessionUpdate: "agent_message_chunk",
                     messageId: item.id,
                     content: { type: "text", text: item.text },
-                    ...(meta ? { _meta: meta } : {}),
+                    _meta: createCodexAgentMessageMeta(item.phase, turnId),
                 }];
             }
             case "reasoning":

diff --git a/src/CodexEventHandler.ts b/src/CodexEventHandler.ts
@@ -69,6 +69,7 @@ import { stripShellPrefix } from "./CommandUtils";
 import {createTerminalOutputMeta, type TerminalOutputMode} from "./TerminalOutputMode";
 import {ReasoningSummaryFilter, sanitizeReasoningParts} from "./ReasoningText";
 import {
+    createCodexAgentMessageMeta,
     createCodexMessagePhaseMeta,
     createAgentTextMessageChunk,
     createAgentTextThoughtChunk,
@@ -364,7 +365,11 @@ export class CodexEventHandler {
 
     private async createTextEvent(event: AgentMessageDeltaNotification): Promise<UpdateSessionEvent> {
         const phase = this.agentMessagePhases.get(event.itemId) ?? null;
-        return createAgentTextMessageChunk(event.delta, event.itemId, createCodexMessagePhaseMeta(phase));
+        return createAgentTextMessageChunk(
+            event.delta,
+            event.itemId,
+            createCodexAgentMessageMeta(phase, event.turnId),
+        );
     }
 
     private async createConfigWarningEvent(event: ConfigWarningNotification): Promise<UpdateSessionEvent> {

diff --git a/src/ContentChunks.ts b/src/ContentChunks.ts
@@ -10,6 +10,16 @@ export function createCodexMessagePhaseMeta(phase: string | null | undefined): A
     return { codex: { phase } };
 }
 
+export function createCodexAgentMessageMeta(
+    phase: string | null | undefined,
+    turnId: string,
+): AcpMeta {
+    return {
+        ...(phase ? {codex: {phase}} : {}),
+        lody: {turnId},
+    };
+}
+
 export function createUserMessageChunk(content: ContentBlock, messageId?: string, meta?: AcpMeta): UpdateSessionEvent {
     if (messageId) {
         return {

diff --git a/src/__tests__/CodexACPAgent/data/agent-message-phases.json b/src/__tests__/CodexACPAgent/data/agent-message-phases.json
@@ -13,6 +13,9 @@
         "_meta": {
           "codex": {
             "phase": "commentary"
+          },
+          "lody": {
+            "turnId": "turn-1"
           }
         }
       }
@@ -34,6 +37,9 @@
         "_meta": {
           "codex": {
             "phase": "final_answer"
+          },
+          "lody": {
+            "turnId": "turn-1"
           }
         }
       }

diff --git a/src/__tests__/CodexACPAgent/data/follow-up-no-duplicates.json b/src/__tests__/CodexACPAgent/data/follow-up-no-duplicates.json
@@ -9,6 +9,11 @@
         "content": {
           "type": "text",
           "text": "He"
+        },
+        "_meta": {
+          "lody": {
+            "turnId": "string"
+          }
         }
       }
     }
@@ -25,6 +30,11 @@
         "content": {
           "type": "text",
           "text": "ll"
+        },
+        "_meta": {
+          "lody": {
+            "turnId": "string"
+          }
         }
       }
     }
@@ -41,6 +51,11 @@
         "content": {
           "type": "text",
           "text": "o!"
+        },
+        "_meta": {
+          "lody": {
+            "turnId": "string"
+          }
         }
       }
     }

diff --git a/src/__tests__/CodexACPAgent/data/load-session-history.json b/src/__tests__/CodexACPAgent/data/load-session-history.json
@@ -53,6 +53,11 @@
         "content": {
           "type": "text",
           "text": "Hello!"
+        },
+        "_meta": {
+          "lody": {
+            "turnId": "turn-1"
+          }
         }
       }
     }

diff --git a/src/__tests__/CodexACPAgent/data/load-session-response-item-history-fallback.json b/src/__tests__/CodexACPAgent/data/load-session-response-item-history-fallback.json
@@ -197,6 +197,11 @@
         "content": {
           "type": "text",
           "text": "The directory contains README.md and src."
+        },
+        "_meta": {
+          "lody": {
+            "turnId": "turn-1"
+          }
         }
       }
     }

diff --git a/src/__tests__/CodexACPAgent/data/multiple-sessions.json b/src/__tests__/CodexACPAgent/data/multiple-sessions.json
@@ -9,6 +9,11 @@
         "content": {
           "type": "text",
           "text": "Hello-1"
+        },
+        "_meta": {
+          "lody": {
+            "turnId": "string"
+          }
         }
       }
     }
@@ -25,6 +30,11 @@
         "content": {
           "type": "text",
           "text": "Hello-2"
+        },
+        "_meta": {
+          "lody": {
+            "turnId": "string"
+          }
         }
       }
     }

diff --git a/src/__tests__/CodexACPAgent/data/output-acp-events.json b/src/__tests__/CodexACPAgent/data/output-acp-events.json
@@ -9,6 +9,11 @@
         "content": {
           "type": "text",
           "text": "He"
+        },
+        "_meta": {
+          "lody": {
+            "turnId": "string"
+          }
         }
       }
     }
@@ -25,6 +30,11 @@
         "content": {
           "type": "text",
           "text": "ll"
+        },
+        "_meta": {
+          "lody": {
+            "turnId": "string"
+          }
         }
       }
     }
@@ -41,6 +51,11 @@
         "content": {
           "type": "text",
           "text": "o!"
+        },
+        "_meta": {
+          "lody": {
+            "turnId": "string"
+          }
         }
       }
     }

diff --git a/src/__tests__/CodexACPAgent/initialize.test.ts b/src/__tests__/CodexACPAgent/initialize.test.ts
@@ -70,9 +70,8 @@ describe('CodexACPAgent - initialize', () => {
                         },
                     },
                     lody: {
-                        forkAtMessage: {
+                        forkAtTurn: {
                             version: 1,
-                            beforeActiveTurn: true,
                         },
                     },
                 },