fix(session): observe resume picker rejections without process kill (#3804)

[innocarpe]

Summary

Successor to closed PR #3830 addressing the single REQUEST_CHANGES blocker.

Managed-candidate preparation can reject before the inner switchSession() catch. The session picker dispatched resume through a void onSelect, so that rejection escaped as an unhandled promise rejection and could kill the process (observed on Windows upgrade resume).

The previous exact head was behavior-correct (identity fence preserved, no auto-retry, rejections observed, current session remains usable). CI/review only blocked on Biome formatter wrapping in two new test files.

Changes

• Same recovery as fix(session): observe resume picker rejections without process kill (#3804) #3830: observe async rejections at controller + component UI dispatch; showError; no auto-retry.
• Formatter-clean the three expect(...) call sites called out in the fix(session): observe resume picker rejections without process kill (#3804) #3830 review (bun --cwd=packages/coding-agent run fmt on the new tests).

Test plan

• Focused selector/resume tests pass
• Biome format matches review diffs (single-line expects)
• Live interactive TUI resume race (not run)

Notes

• Replaces closed fix(session): observe resume picker rejections without process kill (#3804) #3830.
• Fixes Windows: resume crashes after 0.12.7 to 0.12.11 upgrade when managed session changes #3804.

[Yeachan-Heo]

Red-team read-only review: async rejection observation / no retry / identity fence

Head SHA verified: 8e125acc4644529ee6964a60c90bbfa8ab8a0c2d

Scope

5 files (2 source, 3 test). This PR is the successor to closed #3830: a74d8a326 provides the behavior fix, 8e125acc4 is the biome formatting follow-up.

Validation performed

1. Async rejection observation — ✅
session-selector.ts:250-264 introduces #dispatchSelect() which wraps this.onSelect(sessionPath) in void Promise.resolve(...).catch(...). The catch handler:

• If picker is "settled": surfaces error via #showError + #requestRender (host already closed the picker)
• Otherwise: resets to "browsing" state, unfreezes input, shows error, requests render

This prevents async onSelect rejections from becoming process-killing unhandled rejections. Verified by test observes async onSelect rejections without unhandled rejection (#3804):

• expect(unhandled).not.toHaveBeenCalled() — no unhandled rejection
• expect(text(component)).toContain("Error: ...") — error surfaced in UI
• expect(text(component)).toContain("one") — picker stays usable

2. No retry — ✅
selector-controller-session-delete.test.ts:371:

expect(prepareManagedCandidateForStrictAdoption).toHaveBeenCalledTimes(1);

The managed-candidate race (where prepareManagedCandidateForStrictAdoption rejects) is attempted exactly once. No auto-retry of the same candidate. switchSession is NOT called (line 373), and the current session remains active (line 375).

3. Identity fence — ✅
selector-controller-session-delete.test.ts:372:

expect(prepareManagedCandidateForStrictAdoption).toHaveBeenCalledWith(selected.path, "copy-retain", identity);

The identity parameter is passed through to the strict adoption check — the managed candidate is validated against the inspected identity before any migration authority is adopted. When the check rejects (managed session changed), the fence holds: no switch, current session retained.

4. Biome formatting — ✅

bunx biome check <affected test files> → OK

Three expect() calls reformatted to fit within the 120-col limit (the sole purpose of commit 8e125acc4). No behavior change in the formatting commit.

5. Test execution — ✅

bun test session-selector-resume-confirm.test.ts selector-controller-session-delete.test.ts → 20 pass, 0 fail

6. CI status — ✅
17 SUCCESS, 6 SKIPPED, 0 FAILURE. Mergeable.

Verdict

The async rejection observation mechanism is correct: all onSelect return values (sync or async) are observed via Promise.resolve().catch(), preventing unhandled rejections. The identity fence and no-retry contract are enforced by the strict adoption path. Formatting-only follow-up is clean.

Approved.

— gaebal-gajae