🤖 fix: keep compaction identity across startup auto-retry

[coadler]

Summary

Startup auto-retry of an interrupted compaction lost the compaction-request metadata, so the resumed stream was no longer tracked as a compaction. The model's summary reply became a plain assistant response and the chat never compacted.

Background

When a stream is interrupted (crash, restart), deriveStartupAutoRetryRequest rebuilds send options from persisted state. Its compaction branch rebuilt model/agentId/toolPolicy but dropped muxMetadata, because StartupRetrySendOptions.muxMetadata only allowed workspace-turn-task metadata.

On resume, resolveCompactionRequest scans history backward for the compaction-request row. Without the stream identifying as a compaction request, any trailing synthetic user row — a <system-file-update> file-change notice or the [CONTINUE] sentinel — aborts the scan. activeCompactionRequest stayed undefined, compactionHandler.handleCompletion treated the stream-end as a normal turn, and no boundary summary was written.

Implementation

• Widen StartupRetrySendOptions.muxMetadata to also accept { type: "compaction-request" }.
• In the compaction branch of deriveStartupAutoRetryRequest, carry the original muxMetadata through so the resumed stream still identifies itself; resolveCompactionRequest then resolves via the options path regardless of trailing synthetic rows.

Validation

• New regression test seeds durable history with a compaction-request row plus a trailing synthetic row, runs the real startup auto-retry path (scheduleStartupAutoRetryIfNeeded), and asserts the boundary lands. Fails before the fix, passes after.
• Added a control test proving plain synthetic agent-initiated sends (the parent-to-child guidance path) compact correctly end-to-end.
• Added a characterization test documenting that family-payload (preTurnMessages) sends intentionally skip on-send compaction.
• make static-check, targeted compaction suites green. Full src/node/services run shows only failures verified pre-existing on the pristine baseline (unrelated hooks/browser suites).

Risks

Low. The metadata now flows through the same option field resumeStream already consumes; normalizeGatewaySendOptions spreads it through untouched. The widened union is additive: existing workspace-turn-task behavior is unchanged, and non-compaction retries never set the field.

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Generated with xum • Model: openrouter:stealth/ox-alpha • Thinking: high • Cost: $0.04

[coadler]

@codex review

[chatgpt-codex-connector]

Codex Review: Didn't find any major issues. Delightful!

Reviewed commit: 3555414d0a

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[chatgpt-codex-connector]

Security review completed. No security issues were found in this pull request.

Reviewed commit: 3555414d0a

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