deepseek-ai/deepseek-harness · error · FsError

FS_SANDBOX_DENIED

FS_SANDBOX_DENIED

Error message

cannot write "${target.displayPath}": file access denied under read-only mode

What it means

Error "cannot write "${target.displayPath}": file access denied under read-only mode" thrown in deepseek-ai/deepseek-harness.

Source

Thrown at packages/fs/fs-sandbox/src/index.ts:131

  }

  /**
   * Enforce the per-call policy against `target` and return the EXACT target the
   * mutation must use, so the checked identity is the mutated one (no
   * check-here-write-there TOCTOU). `read-only` denies; `workspace-write`
   * re-canonicalizes NOW (`resolve` realpaths the deepest existing ancestor,
   * reflecting a concurrently swapped symlink), requires containment under a
   * writable root, and returns THAT fresh target; `danger-full-access` returns
   * the caller's target unfenced. Throws the structured `FS_SANDBOX_DENIED` on
   * refusal — the tool layer maps it to the model-facing `[sandbox: …]` marker
   * and the escalation hint.
   */
  private async checkedTarget(target: FsTarget, sandboxPolicy?: SandboxExecutionPolicy): Promise<FsTarget> {
    const policy = sandboxPolicy ?? this.ctx.sandboxPolicy.resolve()
    const { mode } = policy
    if (mode === 'danger-full-access') return target
    if (mode === 'read-only') {
      throw new FsError(`cannot write "${target.displayPath}": file access denied under read-only mode`, 'FS_SANDBOX_DENIED')
    }
    // workspace-write: containment on the FRESH canonical path (catches a
    // symlink ancestor swapped since the tool resolved this target), and the
    // mutation delegates with THIS fresh target — never the stale one.
    const fresh = await this.resolve(target.displayPath)
    let contained = false
    for (const root of writableRoots(policy)) {
      if (await isPathUnder(fresh.targetKey, root)) {
        contained = true
        break
      }
    }
    if (!contained) {
      throw new FsError(`cannot write "${target.displayPath}": file access denied under workspace-write mode`, 'FS_SANDBOX_DENIED')
    }
    return fresh
  }
}

View on GitHub (pinned to b150a551b8)

When it happens

Trigger: Thrown at packages/fs/fs-sandbox/src/index.ts:131 when the library encounters an invalid state.

Common situations: See trigger scenarios.

Understand the failure class

• Authentication and authorization failures — expired tokens, bad credentials, and missing scopes.

AI-assisted analysis of deepseek-ai/deepseek-harness@b150a551b8 (2026-08-24). Data as JSON: /api/errors/168cf1536b5a6c96. Report an issue: GitHub.