deepseek-ai/deepseek-harness · error · FsError

FS_NOT_OBSERVED

FS_NOT_OBSERVED

Error message

cannot overwrite existing "${target.displayPath}" without reading it first

What it means

Error "cannot overwrite existing "${target.displayPath}" without reading it first" thrown in deepseek-ai/deepseek-harness.

Source

Thrown at packages/fs/fs-local/src/index.ts:186

    content: string,
    expected?: FsWriteIntent,
    signal?: AbortSignal,
  ): Promise<FsWriteOutcome> {
    return this.withLock(target.targetKey, async () => {
      const existing = await probe(target.targetKey)
      if (existing && existing.type !== 'file') {
        throw new FsError(`cannot write "${target.displayPath}": not a regular file`, 'FS_NOT_REGULAR_FILE')
      }

      if (expected?.kind === 'replaceIfVersion') {
        // Stale guard: the file must still exist at the version the owner observed.
        if (!existing) throw new FsError(`cannot write "${target.displayPath}": file no longer exists`, 'FS_STALE_VERSION')
        if (existing.version !== expected.version) {
          throw new FsError(`cannot write "${target.displayPath}": file changed since it was read`, 'FS_STALE_VERSION')
        }
      } else if (expected?.kind === 'createIfAbsent' && existing) {
        // createIfAbsent onto an existing file: a blind overwrite — require a read first.
        throw new FsError(`cannot overwrite existing "${target.displayPath}" without reading it first`, 'FS_NOT_OBSERVED')
      }
      // No expectation means an unconditional but still atomic write.

      // Capture an optional contextual-diff basis before the write. The bounded
      // reader checks the opened file itself, so an external replacement after
      // `probe()` cannot turn this best-effort presentation read into an
      // unbounded allocation. Either side at/above the configured limit yields
      // `before: null`; consumers retain their whole-file fallback.
      const diffable = existing !== null
        && Buffer.byteLength(content, 'utf8') < this.config.diffBasisMaxBytes
      const before = diffable
        ? await readTextForDiff(target.targetKey, this.config.diffBasisMaxBytes, signal)
        : null
      await writeFileAtomic(
        target.targetKey,
        content,
        existing?.mode,
        signal,

View on GitHub (pinned to b150a551b8)

When it happens

Trigger: Thrown at packages/fs/fs-local/src/index.ts:186 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of deepseek-ai/deepseek-harness@b150a551b8 (2026-08-24). Data as JSON: /api/errors/7525416546a8d861. Report an issue: GitHub.