Function call

src/tools/FileWriteTool/FileWriteTool.ts:223–417

(
    { file_path, content },
    { readFileState, updateFileHistoryState, dynamicSkillDirTriggers },
    _,
    parentMessage,
  )

    return { result: true }
  },
  async call(
    { file_path, content },
    { readFileState, updateFileHistoryState, dynamicSkillDirTriggers },
    _,
    parentMessage,
  ) {
    const fullFilePath = expandPath(file_path)
    const dir = dirname(fullFilePath)

    // Discover skills from this file's path (fire-and-forget, non-blocking)
    const cwd = getCwd()
    const newSkillDirs = await discoverSkillDirsForPaths([fullFilePath], cwd)
    if (newSkillDirs.length > 0) {
      // Store discovered dirs for attachment display
      for (const dir of newSkillDirs) {
        dynamicSkillDirTriggers?.add(dir)
      }
      // Don't await - let skill loading happen in the background
      addSkillDirectories(newSkillDirs).catch(() => {})
    }

    // Activate conditional skills whose path patterns match this file
    activateConditionalSkillsForPaths([fullFilePath], cwd)

    await diagnosticTracker.beforeFileEdited(fullFilePath)

    // Ensure parent directory exists before the atomic read-modify-write section.
    // Must stay OUTSIDE the critical section below (a yield between the staleness
    // check and writeTextContent lets concurrent edits interleave), and BEFORE the
    // write (lazy-mkdir-on-ENOENT would fire a spurious tengu_atomic_write_error
    // inside writeFileSyncAndFlush_DEPRECATED before ENOENT propagates back).
    await getFsImplementation().mkdir(dir)
    if (fileHistoryEnabled()) {
      // Backup captures pre-edit content — safe to call before the staleness
      // check (idempotent v1 backup keyed on content hash; if staleness fails
      // later we just have an unused backup, not corrupt state).
      await fileHistoryTrackEdit(
        updateFileHistoryState,
        fullFilePath,
        parentMessage.uuid,
      )
    }

    // Load current state and confirm no changes since last read.
    // Please avoid async operations between here and writing to disk to preserve atomicity.
    let meta: ReturnType<typeof readFileSyncWithMetadata> | null
    try {
      meta = readFileSyncWithMetadata(fullFilePath)
    } catch (e) {
      if (isENOENT(e)) {
        meta = null
      } else {
        throw e
      }
    }

    if (meta !== null) {
      const lastWriteTime = getFileModificationTime(fullFilePath)