[sentry-junior]

What failed

JUNIOR-9M: getActiveMailboxTurnId throws Conversation … has multiple active mailbox Turns (for example local:web:67232d03… and slack:C0B595QDZLL:1793638594.088319). Every resume attempt of the Conversation throws, retries run out (conversation.work.retry.exhausted), and the Conversation stays stuck until a person posts again.

Root cause

Generic conversation work can stop a Turn without closing its Turn cursor. Examples: the heartbeat clears an expired lease after a worker is lost (deploy rollout, freeze), lost-lease recovery runs out of retries, or a final-attempt Run failure in conversation-turn.ts that marks the Turn failed in the Conversation but leaves the checkpoint running/paused. The next web or event message starts a new Turn next to it. New input only superseded auth-paused Turns, so the Conversation now has two open mailbox Turns. When the new Turn yields, its resume fails.

Fix

When new mailbox input starts a Turn, abandon every other open web or event Turn, not only auth-paused ones. The OAuth prompt cleanup still runs only when an auth-paused Turn is superseded. Slack Turns are not mailbox Turns and stay as before.

Why a Turn that waits to resume is not superseded

New mailbox input starts a Turn only when no yielded Turn waits:

• Every path that leaves a Turn to resume sets execution paused: yield (requestAnotherSlice), expired-lease recovery (clearExpiredConversationLease), a counted retry (recordConversationRetry), and lost-lease recovery in the worker.
• selectAttemptMessages returns no web or event input while execution is paused. A steered web message is not an attempt interrupt while paused. Deferred input appended while paused keeps paused.
• The lost-worker retry pause from fix(task-execution): Resume a turn once after its worker stops checking in #2298 runs only in runNextPausedTurn (Slack and dispatch workers). Mailbox Turns do not use it.
• A Slack mention can interrupt a paused Conversation. It does not reach this path: resolveMailboxTurnWork returns no work for Slack input, and the Slack worker resumes the paused Turn and steers the mention into it.

So a different open mailbox Turn at this point is stale. conversation-turn-work.test.ts › "resumes a paused dashboard Turn before a deferred event" protects the selection rule: it fails when the paused check in selectAttemptMessages is removed.

Review evidence

An end-to-end run through processConversationQueueMessage, the real conversation-turn worker and recoverConversationWork reproduces JUNIOR-9M: a web Turn yields, five workers take the lease and are lost, and the heartbeat sets the Conversation to failed with the cursor still paused. On main, the next message yields and every resume fails with "multiple active mailbox Turns". On this branch, the stale Turn is abandoned and the next message yields, resumes and replies.

That test is not in this PR: scripts/check-test-architecture.mjs does not allow tests in packages/junior/tests to run the agent or compose the worker. Its home is evals/integration/conversation/lifecycle.eval.ts, with a fixture step that loses workers. That needs new model recordings.

Other checks:

• A late save from a lost worker of the abandoned Turn does not reopen it after the new Turn commits history: the save fails with AgentHistoryBranchError and the cursor stays abandoned.
• No terminal lifecycle event is written for the superseded Turn. Do not add one here: the new Turn already wrote turn_started, and the dashboard reads the latest lifecycle event to show that Junior is responding.

Remaining risk

• A stale Turn is closed only when new input arrives. A Conversation that is already stuck still needs a new message, but that message now unsticks it.
• The abandoned Turn sends no reply. The person who sent it is not told that it was dropped. This is the "nothing finishes the Turn" gap in Run every agent on one Conversation execution core #2567.
• Between the abandon and the new Turn's first history commit, a late save from a lost worker could still reopen the old cursor. Turn saves do not check the Conversation lease (Run every agent on one Conversation execution core #2567, item 8).
• JUNIOR-NP (multiple active agent invocations for child Conversations) is the same class of bug. fix(agent-invocations): Keep one active agent invocation per child #2558 fixed it: the worker ends every other active agent invocation of the child before it starts a new one.

via @dcramer.

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Project	Deployment	Actions	Updated
junior-docs	Ready	Preview	Nov 2, 2026 8:03pm UTC

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