deepseek-harness/packages/e2b/fs-e2b/README.md

# @deepseek-ai/dsh-fs-e2b

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E2B implementation of the [`@deepseek-ai/dsh-fs`](../../fs/fs/README.md) provider seam. It has no config: load [`@deepseek-ai/dsh-e2b`](../e2b/README.md) first, then this service in place of `dsh-fs-local`. The provider uses the owner's remote cwd and SDK handle, so file tools observe the same world as E2B-backed Bash processes.

## Behavior

- **Remote identity and metadata** — relative paths resolve as POSIX paths against the caller cwd or `ctx.e2b.cwd`; GNU `realpath -mz` supplies canonical target identity without requiring the final file to exist, and ASCII/base64 plus strict NUL framing preserves newline and multibyte paths across the decoded SDK transport. `stat`, no-follow `lstat`, and stable one-level directory listings project E2B metadata into the filesystem seam; listings reuse returned metadata and resolve symbolic-link entries sequentially. Versions are opaque hashes of E2B metadata plus a per-write extended attribute.
- **Execution-world paths** — canonical targets expose absolute POSIX process paths, percent-encoded `file:` URIs, and provider-owned containment checks, so generic subprocess consumers never parse E2B target ids or apply host path rules.
- **UTF-8 reads** — whole reads and streamed reads preserve cross-chunk decoding, reject invalid UTF-8, and use the seam's 8192-byte NUL sample for binary detection. The model-facing tool still owns size selection and line windowing.
- **Atomic mutations** — writes create a random sibling staging directory, change it to mode `0700` before uploading content, preserve an existing file's POSIX mode, and publish the staged file through E2B's same-filesystem atomic rename. The rename response supplies the committed version, so no fallible metadata request follows the commit point. E2B creates missing parent directories. Literal edits LF-normalize for matching, restore dominant CRLF storage, and serialize mutations per canonical target within the host process. Optional create/version guards keep the base seam's observed-state semantics.
- **Failures and cancellation** — E2B not-found, permission, abort, and other controller failures map to the existing `FsError` vocabulary. Cancellation is best-effort at earlier SDK request boundaries and checked immediately before rename. The signal is not forwarded into the rename RPC, so cancellation cannot interrupt the atomic commit; a successful rename is the commit point.

The provider does not copy, mount, or reconcile the host workspace. Giving it a host path as `cwd` creates a remote directory with the same spelling only.

## Model Experience

Indirectly, through [`dsh-tool-fs`](../../fs/tool-fs/README.md), which renders remote UTF-8 content, directory results, mutation acknowledgements, and provider errors while E2B identity and transport remain internal.

#### KV Cache effect

No direct invalidation; the named consumer owns any request-prefix changes.

## Known Limitations and Deferred Work

- **No host synchronization** — an empty E2B cwd stays empty until a tool, command, or external process populates it; local files are neither uploaded nor reflected back.
- **Mutation coordination is host-process-local** — another harness connection or remote command can race the adapter; version guards detect only metadata changes represented by E2B.
- **Reads reopen canonical targets by path** — a concurrent remote path replacement between resolution and stream opening is not fenced by a stable file handle; no observed product defect justifies a provider-specific bounded-read protocol in this POC.
- **Whole-file mutation costs remain** — overwrite diffs and literal edits read complete files into host memory, and every operation incurs E2B controller latency.
- **The POC targets E2B's default Linux image** — it relies on GNU `realpath`/`base64`/`chmod`, same-filesystem rename, streaming reads, and metadata extended attributes; custom templates are outside this POC.