Distillation

Date: Sep 17, 2026

• 🟡 (00:38) Validation ran tsgo --noEmit and then targeted Bun tests in packages/core/test/session-runner.test.ts; SessionRunnerLLM > settles cancellation when Step start notification is interrupted failed with Interrupted Session settlement failed: ses_runner_test. Result: 2 pass, 107 filtered out, 1 fail, 9 expect() calls across 1 file in 3.18s.
• 🟡 (00:38) Initial debugging hypothesis: the runner reached the cancellation boundary and published Step.Interrupted using the adopted durable assistant ID, but the test listener lifecycle might be preventing cleanup completion.
• 🟡 (00:40) Second debugging hypothesis: external fiber interruption inside the blocked Step.Started notification might bypass the runner settlement handler; proposed requirement was to run cancellation settlement uninterruptibly after the provider stream captures the interrupt.
• 🟡 (00:41) Inspection of packages/core/src/session/runner/llm.ts showed the provider stream already runs beneath an outer Effect.uninterruptibleMask, with restore(providerStream).pipe(Effect.exit) capturing the stream exit; this ruled out the hypothesis that the runner’s interruption handler was bypassed at the masking boundary.
• 🟡 (00:41) packages/core/test/session-runner.test.ts was instrumented so the regression retained session.interrupt(sessionID).pipe(Effect.exit) and inspected durable state rather than aborting immediately on the cleanup error.
• 🟡 (00:42) Diagnostic test showed session.interrupt(sessionID) failed with defect Interrupted Session settlement failed: ses_runner_test; the execution claim remained present with phase: "cancelling", assistant_seq: 3, expires_at: 30000, and a non-null assistant_message_id, instead of being cleared.
• 🟡 (00:42) Root-cause refinement: interruption during Step.Started notification caused the provider stream finalizer’s fragment-flush defect to replace the interrupt-only cause. Because the resulting cause was no longer interruption-only, the runner skipped interruption settlement even though the durable claim was already in phase: "cancelling".
• 🟡 (00:42) packages/core/src/session/runner/llm.ts was changed to consider durable cancellation state in addition to Cause.hasInterrupts(...); packages/core/test/session-runner.test.ts was updated alongside it.
• 🟡 (00:43) After the durable-phase change, tsgo --noEmit completed without a reported type error, but targeted tests still failed: 3 pass, 106 filtered out, 1 fail, 13 expect() calls across 1 file in 2.07s. session.interrupt(sessionID) still returned a failure with Interrupted Session settlement failed: ses_runner_test.
• 🟡 (00:43) Further diagnostics confirmed the settlement handler was selected but the execution claim still remained in phase: "cancelling" with assistant_seq: 3, expires_at: 30000, and a non-null assistant_message_id; the claim was not cleared.
• 🟡 (00:44) Another hypothesis considered publisher ownership/state: the interrupted startAssistant() might resume post-publication assignments during listener cleanup and conflict with the adopted assistant-ID path.
• 🟡 (00:44) Event-table diagnostics ruled in a publication failure: no session.next.step.interrupted.1 event existed, despite the test expecting exactly one event whose data.assistantMessageID matched the durable claim’s assistant_message_id. Targeted result: 0 pass, 109 filtered out, 1 fail, 3 expect() calls.
• 🔴 (00:45) User stated the execution-claim invariant documented in packages/core/src/session/execution/claim.ts: execution IDs immediately fence a node after takeover, and an expired claim never renews itself.
• 🔴 (00:45) User provided the lease requirement from packages/core/src/session/execution/claim.ts: the lease interval must remain larger than the deployment’s maximum clock skew plus one renewal interval.
• 🟡 (00:45) Final root cause identified: the provider registered an in-memory text fragment before durable Step.Started, but durable Text.Started never committed because notification was interrupted. After adopting the durable assistant ID, generic flush() attempted to end that nonexistent durable fragment and failed before publishing Step.Interrupted.
• 🟡 (00:45) Fix applied in packages/core/src/session/runner/publish-llm-event.ts: the durable-assistant adoption path discards pre-start fragment buffers instead of projecting them as durable content. No post-fix typecheck or test result was reported.