Function autoCompactIfNeeded

src/services/compact/autoCompact.ts:249–359

(
  messages: Message[],
  toolUseContext: ToolUseContext,
  cacheSafeParams: CacheSafeParams,
  querySource?: QuerySource,
  tracking?: AutoCompactTrackingState,
  snipTokensFreed?: number,
)

}

export async function autoCompactIfNeeded(
  messages: Message[],
  toolUseContext: ToolUseContext,
  cacheSafeParams: CacheSafeParams,
  querySource?: QuerySource,
  tracking?: AutoCompactTrackingState,
  snipTokensFreed?: number,
): Promise<{
  wasCompacted: boolean
  compactionResult?: CompactionResult
  consecutiveFailures?: number
}> {
  if (isEnvTruthy(process.env.DISABLE_COMPACT)) {
    return { wasCompacted: false }
  }

  // Circuit breaker: stop retrying after N consecutive failures.
  // Without this, sessions where context is irrecoverably over the limit
  // hammer the API with doomed compaction attempts on every turn.
  if (
    tracking?.consecutiveFailures !== undefined &&
    tracking.consecutiveFailures >= MAX_CONSECUTIVE_AUTOCOMPACT_FAILURES
  ) {
    return { wasCompacted: false }
  }

  const model = toolUseContext.options.mainLoopModel
  const shouldCompact = await shouldAutoCompact(
    messages,
    model,
    querySource,
    snipTokensFreed,
  )

  if (!shouldCompact) {
    return { wasCompacted: false }
  }

  const recompactionInfo: RecompactionInfo = {
    isRecompactionInChain: tracking?.compacted === true,
    turnsSincePreviousCompact: tracking?.turnCounter ?? -1,
    previousCompactTurnId: tracking?.turnId,
    autoCompactThreshold: getAutoCompactThreshold(model),
    querySource,
  }

  // EXPERIMENT: Try session memory compaction first
  const sessionMemoryResult = await trySessionMemoryCompaction(
    messages,
    toolUseContext.agentId,
    recompactionInfo.autoCompactThreshold,
  )
  if (sessionMemoryResult) {
    // Reset lastSummarizedMessageId since session memory compaction prunes messages
    // and the old message UUID will no longer exist after the REPL replaces messages
    setLastSummarizedMessageId(undefined)
    runPostCompactCleanup(querySource)
    // Reset cache read baseline so the post-compact drop isn't flagged as a