Function microcompactMessages

src/services/compact/microCompact.ts:253–293

(
  messages: Message[],
  toolUseContext?: ToolUseContext,
  querySource?: QuerySource,
)

}

export async function microcompactMessages(
  messages: Message[],
  toolUseContext?: ToolUseContext,
  querySource?: QuerySource,
): Promise<MicrocompactResult> {
  // Clear suppression flag at start of new microcompact attempt
  clearCompactWarningSuppression()

  // Time-based trigger runs first and short-circuits. If the gap since the
  // last assistant message exceeds the threshold, the server cache has expired
  // and the full prefix will be rewritten regardless — so content-clear old
  // tool results now, before the request, to shrink what gets rewritten.
  // Cached MC (cache-editing) is skipped when this fires: editing assumes a
  // warm cache, and we just established it's cold.
  const timeBasedResult = maybeTimeBasedMicrocompact(messages, querySource)
  if (timeBasedResult) {
    return timeBasedResult
  }

  // Only run cached MC for the main thread to prevent forked agents
  // (session_memory, prompt_suggestion, etc.) from registering their
  // tool_results in the global cachedMCState, which would cause the main
  // thread to try deleting tools that don't exist in its own conversation.
  if (feature('CACHED_MICROCOMPACT')) {
    const mod = await getCachedMCModule()
    const model = toolUseContext?.options.mainLoopModel ?? getMainLoopModel()
    if (
      mod.isCachedMicrocompactEnabled() &&
      mod.isModelSupportedForCacheEditing(model) &&
      isMainThreadSource(querySource)
    ) {
      return await cachedMicrocompactPath(messages, querySource)
    }
  }

  // Legacy microcompact path removed — tengu_cache_plum_violet is always true.
  // For contexts where cached microcompact is not available (external builds,
  // non-ant users, unsupported models, sub-agents), no compaction happens here;
  // autocompact handles context pressure instead.
  return { messages }
}

/**
 * Cached microcompact path - uses cache editing API to remove tool results