Auto-compact may run before session memory extraction finishes (race condition)

[sfc-gh-mochen]

Description

The last few messages in a session can be lost during auto-compaction due to a race condition with session memory extraction.

Background

Session memory extraction runs asynchronously after each turn. Auto-compaction can trigger at the start of a new turn when token count exceeds the threshold.

The wait function (MC2/oj2) only waits while session memory is actively running - it checks a timestamp variable that's set when extraction starts and cleared when it finishes:

async function waitForSessionMemory() {
  while (sessionMemoryStartedTimestamp) {  // Only waits if currently running
    if (Date.now() - sessionMemoryStartedTimestamp > 60000) return;  // Stale
    if (Date.now() - waitStart > 15000) return;  // Timeout
    await sleep(1000);
  }
}

The Problem

If session memory extraction hasn't started yet when auto-compact triggers (due to debouncing or timing), the wait function returns immediately because the timestamp variable is undefined. Compaction then proceeds without the latest session memory.

Result: The last few messages/prompts may not be included in the session memory summary, effectively losing that context after compaction.

Timeline

1. User sends message, turn completes
2. Session memory extraction is queued (debounced)
3. User sends another message
4. Token threshold exceeded → auto-compact triggers
5. Wait function called, but sessionMemoryStartedTimestamp is still undefined
6. Wait returns immediately
7. Compaction runs with stale session memory
8. Session memory extraction finally runs (too late)
9. Latest context is lost

Suggested Fix

Move the wait call earlier in the auto-compact flow, or ensure session memory extraction is triggered synchronously before checking whether to wait.

Thanks!