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# ctx.fs

`FileSystem` (abstract seam) — provided by `@deepseek-ai/dsh-fs`.

Abstract filesystem provider. Targets must preserve identity across aliases; reads expose regular UTF-8 text or typed errors, listings are stable and content-free, and mutations are atomic. Optional guards add stale protection without changing the unguarded provider contract.

[Source](https://github.com/deepseek-harness/deepseek-harness/blob/master/packages/fs/fs/src/index.ts#L81)

### ctx.fs.sandboxMode

```ts website-api
/**
/**
 * The sandbox mode this backend enforces on mutations BY DEFAULT, or
 * `undefined` when it does not confine at all — the capability fact the tool
 * layer reads to advertise the escalation fields honestly (mirrors
 * `BashExecutor.sandboxMode`). The base class and the bare local backend
 * report `undefined`; a sandboxing backend (`@deepseek-ai/dsh-fs-sandbox`)
 * overrides it with the deployment default. A session override may make the
 * effective mode narrower or wider, so strict escalation widening is checked
 * per call rather than encoded in this default-relative fact.
 * @returns the configured default mode of a sandboxing backend; `undefined`
 *   for a backend that never confines.
 */
get sandboxMode(): SandboxMode | undefined
```

/** The sandbox mode this backend enforces on mutations BY DEFAULT, or `undefined` when it does not confine at all — the capability fact the tool layer reads to advertise the escalation fields honestly (mirrors `BashExecutor.sandboxMode`). The base class and the bare local backend report `undefined`; a sandboxing backend (`@deepseek-ai/dsh-fs-sandbox`) overrides it with the deployment default. A session override may make the effective mode narrower or wider, so strict escalation widening is checked per call rather than encoded in this default-relative fact.

[Source](https://github.com/deepseek-harness/deepseek-harness/blob/master/packages/fs/fs/src/index.ts#L99)

### ctx.fs.resolve(path, opts?)

```ts website-api
/**
 * Resolve a model/plugin-supplied path into a stable {@link FsTarget}. May perform I/O (a
 * remote/sandboxed backend may need a round-trip to map a path to a stable identity), hence
 * async even though the local backend only normalizes + realpaths.
 *
 * @param path - the path to resolve; relative paths resolve against `opts.cwd`.
 * @param opts - optional cwd override and cancellation signal.
 * @returns the stable target; the same file yields the same `targetKey`.
 */
abstract resolve(path: string, opts?: { cwd?: string; signal?: AbortSignal }): Promise<FsTarget>
```

Resolve a model/plugin-supplied path into a stable FsTarget. May perform I/O (a remote/sandboxed backend may need a round-trip to map a path to a stable identity), hence async even though the local backend only normalizes + realpaths.

- `path` — the path to resolve; relative paths resolve against `opts.cwd`.
- `opts` — optional cwd override and cancellation signal.

**Returns** the stable target; the same file yields the same `targetKey`.

[Source](https://github.com/deepseek-harness/deepseek-harness/blob/master/packages/fs/fs/src/index.ts#L112)

### ctx.fs.stat(target, signal?)

```ts website-api
/**
 * Return target metadata, or `undefined` when the target does not exist.
 * @param target - the resolved target to stat.
 * @param signal - aborts the metadata round-trip.
 * @returns metadata only, never content; undefined for an absent target.
 */
abstract stat(target: FsTarget, signal?: AbortSignal): Promise<FsInfo | undefined>
```

Return target metadata, or `undefined` when the target does not exist.

- `target` — the resolved target to stat.
- `signal` — aborts the metadata round-trip.

**Returns** metadata only, never content; undefined for an absent target.

[Source](https://github.com/deepseek-harness/deepseek-harness/blob/master/packages/fs/fs/src/index.ts#L120)

### ctx.fs.lstat(path, opts?, signal?)

```ts website-api
/**
 * Return path metadata without following the final path component when it is a
 * symbolic link. This is intentionally path-shaped, not target-shaped:
 * {@link resolve} follows symlinks to produce the stable identity used by
 * normal reads/writes, while `lstat` lets a consumer reject the path itself
 * before that follow happens.
 *
 * `opts.cwd` follows {@link resolve}'s cwd rules. `undefined` means the path is
 * absent.
 * @param path - the path to inspect; relative paths resolve against `opts.cwd`.
 * @param opts - `cwd` overrides the backend's default base for relative paths.
 * @param signal - aborts the metadata round-trip.
 * @returns metadata only, never content; undefined for an absent path.
 */
abstract lstat(path: string, opts?: { cwd?: string }, signal?: AbortSignal): Promise<FsPathInfo | undefined>
```

Return path metadata without following the final path component when it is a symbolic link. This is intentionally path-shaped, not target-shaped: resolve follows symlinks to produce the stable identity used by normal reads/writes, while `lstat` lets a consumer reject the path itself before that follow happens.
`opts.cwd` follows resolve's cwd rules. `undefined` means the path is absent.

- `path` — the path to inspect; relative paths resolve against `opts.cwd`.
- `opts` — `cwd` overrides the backend's default base for relative paths.
- `signal` — aborts the metadata round-trip.

**Returns** metadata only, never content; undefined for an absent path.

[Source](https://github.com/deepseek-harness/deepseek-harness/blob/master/packages/fs/fs/src/index.ts#L136)

### ctx.fs.readText(target, signal?)

```ts website-api
/**
 * Read the whole regular text file as a single decoded string.
 * @param target - the resolved target to read.
 * @param signal - aborts the read.
 * @returns the full decoded UTF-8 content.
 */
abstract readText(target: FsTarget, signal?: AbortSignal): Promise<string>
```

Read the whole regular text file as a single decoded string.

- `target` — the resolved target to read.
- `signal` — aborts the read.

**Returns** the full decoded UTF-8 content.

[Source](https://github.com/deepseek-harness/deepseek-harness/blob/master/packages/fs/fs/src/index.ts#L144)

### ctx.fs.streamText(target, signal?)

```ts website-api
/**
 * Stream the whole regular text file as decoded text chunks (same text
 * semantics as {@link readText}, for large files). The backend owns
 * cross-chunk UTF-8 decoding and binary rejection so the policy layer never
 * touches raw bytes.
 * @param target - the resolved target to read.
 * @param signal - aborts the stream, including between chunks.
 * @returns the chunk iterable, decoded and validated like {@link readText}.
 */
abstract streamText(target: FsTarget, signal?: AbortSignal): Promise<AsyncIterable<string>>
```

Stream the whole regular text file as decoded text chunks (same text semantics as readText, for large files). The backend owns cross-chunk UTF-8 decoding and binary rejection so the policy layer never touches raw bytes.

- `target` — the resolved target to read.
- `signal` — aborts the stream, including between chunks.

**Returns** the chunk iterable, decoded and validated like `readText`.

[Source](https://github.com/deepseek-harness/deepseek-harness/blob/master/packages/fs/fs/src/index.ts#L155)

### ctx.fs.listDir(target, signal?)

```ts website-api
/**
 * List direct children of a directory in stable name order. Returns resolved
 * child targets plus cheap metadata only; never reads file contents.
 * @param target - the resolved directory target.
 * @param signal - aborts the listing.
 * @returns one entry per direct child, in stable name order.
 */
abstract listDir(target: FsTarget, signal?: AbortSignal): Promise<FsDirEntry[]>
```

List direct children of a directory in stable name order. Returns resolved child targets plus cheap metadata only; never reads file contents.

- `target` — the resolved directory target.
- `signal` — aborts the listing.

**Returns** one entry per direct child, in stable name order.

[Source](https://github.com/deepseek-harness/deepseek-harness/blob/master/packages/fs/fs/src/index.ts#L164)

### ctx.fs.writeText(target, content, expected?, signal?, sandboxMode?)

```ts website-api
/**
 * Atomically create or replace UTF-8 text. `expected` guards intent and
 * staleness; omission allows unconditional overwrite.
 * @param target - the resolved target to write.
 * @param content - the full new file content.
 * @param expected - the write intent guarding the write; omit for unconditional.
 * @param signal - aborts before the atomic rename takes effect.
 * @param sandboxMode - the per-call sandbox mode this write runs under; a
 *   sandboxing backend fences the write by it, the bare backend ignores it.
 *   Omit to leave the backend its own default.
 * @returns the outcome, including the version the write produced.
 */
abstract writeText( target: FsTarget, content: string, expected?: FsWriteIntent, signal?: AbortSignal, sandboxMode?: SandboxMode, ): Promise<FsWriteOutcome>
```

Atomically create or replace UTF-8 text. `expected` guards intent and staleness; omission allows unconditional overwrite.

- `target` — the resolved target to write.
- `content` — the full new file content.
- `expected` — the write intent guarding the write; omit for unconditional.
- `signal` — aborts before the atomic rename takes effect.
- `sandboxMode` — the per-call sandbox mode this write runs under; a sandboxing backend fences the write by it, the bare backend ignores it. Omit to leave the backend its own default.

**Returns** the outcome, including the version the write produced.

[Source](https://github.com/deepseek-harness/deepseek-harness/blob/master/packages/fs/fs/src/index.ts#L178)

### ctx.fs.editText(target, edit, expected?, signal?, sandboxMode?)

```ts website-api
/**
 * Atomically edit literal text. When supplied, the version guard is checked
 * before matching so stale content reports `FS_STALE_VERSION`; omission edits
 * the current content without a freshness precondition.
 * @param target - the resolved target to edit.
 * @param edit - the literal search/replace request.
 * @param expected - the version guard; omit for an unconditional edit.
 * @param signal - aborts before the atomic rename takes effect.
 * @param sandboxMode - the per-call sandbox mode this edit runs under; a
 *   sandboxing backend fences the edit by it, the bare backend ignores it.
 *   Omit to leave the backend its own default.
 * @returns the outcome, including the version the edit produced.
 */
abstract editText( target: FsTarget, edit: FsEditRequest, expected?: { version: FsVersion }, signal?: AbortSignal, sandboxMode?: SandboxMode, ): Promise<FsEditOutcome>
```

Atomically edit literal text. When supplied, the version guard is checked before matching so stale content reports `FS_STALE_VERSION`; omission edits the current content without a freshness precondition.

- `target` — the resolved target to edit.
- `edit` — the literal search/replace request.
- `expected` — the version guard; omit for an unconditional edit.
- `signal` — aborts before the atomic rename takes effect.
- `sandboxMode` — the per-call sandbox mode this edit runs under; a sandboxing backend fences the edit by it, the bare backend ignores it. Omit to leave the backend its own default.

**Returns** the outcome, including the version the edit produced.

[Source](https://github.com/deepseek-harness/deepseek-harness/blob/master/packages/fs/fs/src/index.ts#L199)