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fix(tabs): forking into a tab no longer picks a turn that is still running - #277
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…nning Continuing a sibling tab, forking onto another model, or forking from before a message chose the latest completed assistant message. A running Claude turn completes messages between its tool calls, so the fork could point at the in-progress run, which the orchestrator rejects and the tab route reported as internal_error. The fork point now skips responses of runs that have not finished, using the same forkable-status rule as the orchestrator (moved to contracts). The tab service also refuses an explicit fork of the source's active run as an invalid request instead of a dispatch failure. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
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Continuing a sibling tab from an empty tab's context pill failed with "Could not fork into a new tab — The environment failed to answer this request (internal_error)" while that sibling was mid-turn. The server picked the latest completed assistant message as the fork point, but a running Claude turn completes messages between its tool calls, so the point landed on the in-progress run. The orchestrator then refused it (
Fork source run … is running; in-progress and rolled-back runs cannot be forked), and the tab route turned that dispatch failure into a 500.Fix
latestThreadForkPointnow takes the thread's runs and skips responses whose run has not finished, using the orchestrator's ownisForkableSourceRunStatusrule (moved into contracts so both share it). Continuing from a busy tab now forks from its last finished turn.ThreadTabs.forkTabrefuses an explicit fork of the source's active run asinvalid_requestwith a readable detail, rather than letting it fail as an internal dispatch error. Agents opening tabs over MCP get that message.The per-response fork button already hides during a running turn on web and mobile, so it needed no change.
Tests:
vp test run packages/client-runtime/src/threadTabs.test.ts apps/server/src/threadTabs/ThreadTabs.test.ts apps/server/src/orchestration-v2/ThreadForkService.test.ts(26 passed). Typecheck clean for contracts, client-runtime, server, web, mobile.Done by Claude Opus 5.5 in Claude Code (via T3 Code).
🤖 Generated with Claude Code