deepseek-harness/packages/fs/README.md

fs/ - filesystem capability family

The filesystem stack: a provider seam (text IO + atomic mutation with an optional version guard), a local implementation, a policy gate plugin (observed-state + read-before-edit + version-guarded write/edit), the model-facing file tools + executor, and the bash-backed discovery tools. All product packages.

Package	Role	ctx key
fs/	Provider seam: text IO + atomic mutation primitives (optional version guard); owns the fs/* policy events	ctx.fs
fs-local/	Local-filesystem FileSystem implementation	(registers ctx.fs)
fs-sandbox/	Sandbox-enforcing FileSystem: extends fs-local and fences write/edit by the per-call sandbox mode (read-only denies, workspace-write contains to the workspace + temp roots), reads pass through	(registers ctx.fs)
fs-policy/	Policy gate plugin: observed-state + read-before-edit + version-guarded write/edit, via the fs/* event gate	(no service — fs/* listeners)
tool-fs/	Model-facing read/write/edit tools AND the executor (reads via ctx.fs, owns read windowing, dispatches fs/*); advertises the sandbox escalation fields when the mounted ctx.fs confines	(registers on ctx.tools)
tool-fs-search/	Model-facing glob/grep discovery tools, backed by fixed ripgrep commands through the bash seam (ctx.bash), NOT by ctx.fs provider methods	(registers on ctx.tools)

The interface lives at fs/fs/. A sandboxed, remote, or project-scoped filesystem backend can replace fs-local without touching the seam, the policy gate, or the model-facing tool schemas — fs-sandbox is the first such replacement (an in-process path fence over the shared sandbox mode; see the cross-family fs sandbox Agent Note). The policy (fs-policy/) is a plugin that participates only through the fs/* event gate, not a service the tool injects — so dropping it gracefully loses the policy and leaves the unconstrained bare provider rather than breaking the tool. A deployment that loads tool-fs/ is expected to also load it. The mode fence and the read-before-edit gate are orthogonal and compose. Discovery (tool-fs-search/) deliberately does NOT extend the provider seam: search is a process-backed rg workflow on the bash executor, so filesystem backends stay free of a universal search contract; its results are follow-up-readable when the bash workdir and the read root are the same workspace (the co-located deployment its README documents).

No timeouts on file IO

read/write/edit take no timeoutMs, and the provider seam arms no deadline — unlike bash and web (which consume @deepseek-ai/dsh-timeout) and the bash-backed glob/grep (whose declared timeoutMs is enforced by @deepseek-ai/dsh-timeout-policy): those are process-backed, where a deadline can really kill the work. A local syscall is best-effort-abortable at most: a timeout could not force an in-progress fsync/rename to stop, so a deadline here would be a knob that cannot deliver on its promise. Adding one would also be an implicit default in the exact place explicit-over-implicit forbids. Both reference agents (Claude Code, Codex) leave file IO untimed for the same reason; cancellation still propagates through the tool-execution signal for best-effort abort at syscall boundaries.