[fixfon]

Rolling back a Claude fork’s first run previously created an empty native session. The timeline retained inherited messages, but the next provider request lost that history. The fork now records the copied transcript’s remapped head, then resumes the same session at that head after rollback. Ordinary threads and forks without a recorded head keep the existing fresh-session fallback.

Thanks @fixfon for #21188. The contributor’s commits are preserved, with current main merged. The optional cursor metadata and adapter behavior remain together because neither provides the fix independently.

Fixes #21166, confirmed on main by a maintainer.

Verification:

• The two focused adapter/query-runner suites went from 292 to 293 passing tests, while removing 65 lines of test code. The standalone rollback harness was replaced with the existing completed-turn fixture, covering recorded fork heads, forks without a recorded head, and ordinary threads. Query-runner coverage checks remapped head capture and unreadable transcripts.
• With main production restored temporarily, the fork rollback regression fails; both fresh-session fallback rows pass. The head-read tests also distinguish the new query-runner behavior. Restoring the fix returns all 293 tests to passing.
• Another 28 existing fork/replay/rollback integration tests pass, for 321 passing tests across five files. Scoped lint and formatting pass with one inherited unused-variable warning; server and contracts typechecks pass. The implementation resolves the rollback cursor once and reuses the existing resume path. Independent Claude Opus 5.5 and Codex gpt-6-sol full-PR reviews found no code blockers. An optional suggestion to log failed head reads was left out; the successful-fork fallback is deliberate and covered.
• Installed SDK/CLI before-and-after request capture: SDK 0.3.276 forks an isolated synthetic transcript and remaps its UUIDs. Native Claude CLI 2.1.303 then resumes through the SDK against a local HTTP capture server. A fresh session loses inherited messages; plain resume retains the unwanted fork run; resume at the captured inherited head preserves inherited user/assistant messages and excludes both fork-run messages. The retained session identity is also checked. The capture server returns HTTP 400 deliberately, so no model inference or real account is involved.
• This is a server behavior change; the live proof exercises the installed SDK/native CLI boundary with synthetic transcript data, not a complete client rollback flow or model response. macOS, Windows, Electron desktop, iOS, and Android were not run. Forks created before this change, or whose copied transcript cannot be read, have no saved head and retain the old fallback.

Current-head CI passes after rerunning a failed web job caused by a Playwright route-handling rejection. Macroscope has no check on this rebuilt head; its approval comment is for the original contributor head, so fresh approval remains a maintainer follow-up.

Maintainer takeover: Codex gpt-6-astra tests and gpt-6.1-sol implementation, with independent Claude Opus 5.5 and Codex gpt-6-sol review through T3 Code.

[macroscopeapp]

Approvability

Verdict: Approved at 54d6102

Macroscope's review found this PR approvable — This is a focused Claude rollback bug fix with backward-compatible optional metadata, preserved fallback behavior, and targeted coverage for forked and non-forked threads. Its runtime impact is localized to restoring inherited history for the affected fork rollback path.

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Reviewing files that changed from the base of the PR and between 0ade8f0 and d92b806.

📒 Files selected for processing: 5

• apps/server/src/claudeHistoryWorker.ts
• apps/server/src/orchestration-v2/Adapters/ClaudeAdapterV2.test.ts
• apps/server/src/orchestration-v2/Adapters/ClaudeAdapterV2.ts
• apps/server/src/orchestration-v2/Adapters/ClaudeAgentSdkQueryRunner.test.ts
• packages/contracts/src/orchestrationV2.ts

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📒 Files selected for processing: 3

• apps/server/src/orchestration-v2/Adapters/ClaudeAdapterV2.test.ts
• apps/server/src/orchestration-v2/Adapters/ClaudeAdapterV2.ts
• apps/server/src/orchestration-v2/Adapters/ClaudeAgentSdkQueryRunner.test.ts

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📝 Walkthrough

Claude forks now retain the copied transcript’s last message UUID as native thread metadata when it can be read. A rollback to thread start resumes a fork at that message. A non-fork thread still receives a fresh native session.

Changes: Claude fork rollback

Layer / File(s)	Summary
Capture and retain fork head apps/server/src/orchestration-v2/Adapters/ClaudeAdapterV2.ts, packages/contracts/src/orchestrationV2.ts, apps/server/src/orchestration-v2/Adapters/ClaudeAgentSdkQueryRunner.test.ts	The query runner reads the forked transcript and returns its last message UUID when available. The adapter stores the UUID in provider-thread native metadata. Tests cover readable transcripts and transcript-read failures.
Rollback from thread start apps/server/src/orchestration-v2/Adapters/ClaudeAdapterV2.ts, apps/server/src/orchestration-v2/Adapters/ClaudeAdapterV2.test.ts	A fork with a stored head resumes at that message after rollback. Without a stored fork head, rollback allocates a fresh native session. Tests cover both cases and verify that fork lineage is retained.

Priority: ⬇️ Low

Estimated code review effort: 3 (Moderate) | ~20 minutes

Change: Bug fix · Severity of issue fixed: Low

Suggested reviewers: t3dotgg

Merge Risk: ⚪ Minimal · up to 0ade8

The change preserves inherited history when a fork head is available and retains the fresh-session fallback. No actionable merge-blocking issue is established.

Security architecture risk: 🔵 Low · up to 0ade8

This is a narrow conversation-rollback change with no demonstrated expansion of access or tool privileges. Risk is low rather than minimal because cursor validity and recovery during interrupted or concurrent operations were not fully established.

Retained concerns
No architecture-level concerns identified.

Security review details

Security Blast Radius

• inferred — On the normal creation path, the changed context exposure is the inherited transcript of the selected forked conversation. The cursor chooses a position within that fork's native session; it does not select another session or grant a credential. Broader tenant, account, or data-store exposure was not established by this inspection.

Trust Boundaries and Controls

• observed — The rollback service loads the provider thread from the requested app-thread projection, verifies that it remains the active thread for the selected provider instance, and opens the matching provider session. The adapter rejects rollback during an active turn and closes the matching live query before returning the rewind state.

Resilience and Maintainability Implications

• observed — Rollback invokes the provider before restoring files and persisting the resulting provider-thread snapshot under the thread-command lock. Query closure has timeout handling, and terminal rollback failures have a failure-recording path. These controls do not establish atomicity across provider state, files, and event persistence, or complete serialization with concurrent message dispatch; no introduced security regression was established from that gap.

Pre-merge checks: 4

Check name	Status	Explanation
Title check		The title clearly and concisely describes the primary fix: preserving inherited history when rolling back a Claude fork's first run.
Linked Issues check		Issue [#21166] requires first-run rollback of a Claude fork to preserve inherited provider history. The change records the copied transcript head in forkHeadMessageId and resumes the existing native…
Out of Scope Changes check		The changes stay within issue [#21166]. They update Claude fork metadata, fork-head detection, rollback behavior, the related contract, and focused automated tests. The summary identifies no unrelated…
Description check		The description provides the problem, implementation, scope approval, detailed verification results, limitations, and agent attribution. It does not use the template's explicit Problem, Change, and Sc…

Full details: Linked Issues check

Explanation

Issue [#21166] requires first-run rollback of a Claude fork to preserve inherited provider history. The change records the copied transcript head in forkHeadMessageId and resumes the existing native session at that head during thread_start rollback. Missing head metadata keeps the existing fresh-session fallback. Tests cover recorded heads, missing heads, ordinary threads, and unreadable transcripts.

Full details: Out of Scope Changes check

Explanation

The changes stay within issue [#21166]. They update Claude fork metadata, fork-head detection, rollback behavior, the related contract, and focused automated tests. The summary identifies no unrelated product behavior or files.

Full details: Description check

Explanation

The description provides the problem, implementation, scope approval, detailed verification results, limitations, and agent attribution. It does not use the template's explicit Problem, Change, and Scope and approval headings, but the required information is present and sufficiently complete.

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[juliusmarminge]

Taking over this one for maintainer batch claude-08. I’ll merge current main, reduce the tests, rebuild the fork rollback path, and verify SDK fork/resume behavior before independent reviews. The original author’s commits will be preserved.