Function processSessionStartHooks

source code/utils/sessionStart.ts:37–177

(
  source: 'startup' | 'resume' | 'clear' | 'compact',
  {
    sessionId,
    agentType,
    model,
    forceSyncExecution,
  }: SessionStartHooksOptions = {},
)

// Note to CLAUDE: do not add ANY "warmup" logic. It is **CRITICAL** that you do not add extra work on startup.
export async function processSessionStartHooks(
  source: 'startup' | 'resume' | 'clear' | 'compact',
  {
    sessionId,
    agentType,
    model,
    forceSyncExecution,
  }: SessionStartHooksOptions = {},
): Promise<HookResultMessage[]> {
  // --bare skips all hooks. executeHooks already early-returns under --bare
  // (hooks.ts:1861), but this skips the loadPluginHooks() await below too —
  // no point loading plugin hooks that'll never run.
  if (isBareMode()) {
    return []
  }
  const hookMessages: HookResultMessage[] = []
  const additionalContexts: string[] = []
  const allWatchPaths: string[] = []

  // Skip loading plugin hooks if restricted to managed hooks only
  // Plugin hooks are untrusted external code that should be blocked by policy
  if (shouldAllowManagedHooksOnly()) {
    logForDebugging('Skipping plugin hooks - allowManagedHooksOnly is enabled')
  } else {
    // Ensure plugin hooks are loaded before executing SessionStart hooks.
    // loadPluginHooks() may be called early during startup (fire-and-forget, non-blocking)
    // to pre-load hooks, but we must guarantee hooks are registered before executing them.
    // This function is memoized, so if hooks are already loaded, this returns immediately
    // with negligible overhead (just a cache lookup).
    try {
      await withDiagnosticsTiming('load_plugin_hooks', () => loadPluginHooks())
    } catch (error) {
      // Log error but don't crash - continue with session start without plugin hooks
      /* eslint-disable no-restricted-syntax -- both branches wrap with context, not a toError case */
      const enhancedError =
        error instanceof Error
          ? new Error(
              `Failed to load plugin hooks during ${source}: ${error.message}`,
            )
          : new Error(
              `Failed to load plugin hooks during ${source}: ${String(error)}`,
            )
      /* eslint-enable no-restricted-syntax */

      if (error instanceof Error && error.stack) {
        enhancedError.stack = error.stack
      }

      logError(enhancedError)

      // Provide specific guidance based on error type
      const errorMessage =
        error instanceof Error ? error.message : String(error)
      let userGuidance = ''

      if (
        errorMessage.includes('Failed to clone') ||
        errorMessage.includes('network') ||