Function runForkedAgent

src/utils/forkedAgent.ts:489–626

({
  promptMessages,
  cacheSafeParams,
  canUseTool,
  querySource,
  forkLabel,
  overrides,
  maxOutputTokens,
  maxTurns,
  onMessage,
  skipTranscript,
  skipCacheWrite,
}: ForkedAgentParams)

 * ```
 */
export async function runForkedAgent({
  promptMessages,
  cacheSafeParams,
  canUseTool,
  querySource,
  forkLabel,
  overrides,
  maxOutputTokens,
  maxTurns,
  onMessage,
  skipTranscript,
  skipCacheWrite,
}: ForkedAgentParams): Promise<ForkedAgentResult> {
  const startTime = Date.now()
  const outputMessages: Message[] = []
  let totalUsage: NonNullableUsage = { ...EMPTY_USAGE }

  const {
    systemPrompt,
    userContext,
    systemContext,
    toolUseContext,
    forkContextMessages,
  } = cacheSafeParams

  // Create isolated context to prevent mutation of parent state
  const isolatedToolUseContext = createSubagentContext(
    toolUseContext,
    overrides,
  )

  // Do NOT filterIncompleteToolCalls here — it drops the whole assistant on
  // partial tool batches, orphaning the paired results (API 400). Dangling
  // tool_uses are repaired downstream by ensureToolResultPairing in claude.ts,
  // same as the main thread — identical post-repair prefix keeps the cache hit.
  const initialMessages: Message[] = [...forkContextMessages, ...promptMessages]

  // Generate agent ID and record initial messages for transcript
  // When skipTranscript is set, skip agent ID creation and all transcript I/O
  const agentId = skipTranscript ? undefined : createAgentId(forkLabel)
  let lastRecordedUuid: UUID | null = null
  if (agentId) {
    await recordSidechainTranscript(initialMessages, agentId).catch(err =>
      logForDebugging(
        `Forked agent [${forkLabel}] failed to record initial transcript: ${err}`,
      ),
    )
    // Track the last recorded message UUID for parent chain continuity
    lastRecordedUuid =
      initialMessages.length > 0
        ? initialMessages[initialMessages.length - 1]!.uuid
        : null
  }

  // Run the query loop with isolated context (cache-safe params preserved)
  try {
    for await (const message of query({
      messages: initialMessages,