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feat(acp): honor per-session cwd — run each ACP session in its own workspace

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Lifts the RFC 010 § Deferred restriction that the server had to launch in the
workspace ("cwd must equal the launch directory"). An editor can now open any
project folder, and N concurrent sessions over one connection can each target a
different directory.

- packages/acp: drop the `cwd === process.cwd()` guard in validateWorkspaceParams
  (keep "must be absolute" — the cwd becomes the session header / bash workdir),
  and drop the persisted-cwd-vs-launch-dir check in session/load (a resumed
  session keeps its original header.cwd, so its bash tools run in its workspace).
- packages/tool-bash: the missing link — default the bash workdir to the calling
  agent's session cwd (`exec.agent.session.header.cwd`) via a new resolveWorkdir
  helper. An explicit model `workdir` still wins; a relative one resolves against
  the session cwd. This is the only correct spot for multi-session: N sessions
  share one ctx.bash executor, so the workdir must come per-call from exec.agent,
  not executor config. Falls back to the executor default when no session cwd is
  available (preserves non-ACP behavior).
- Trust: the cwd originates from the ACP client (the user's editor) at
  session/new — same trust level as the old launch dir; no new untrusted-input
  path. `additionalDirectories` (scope widening / sandbox) stays rejected.
- Tests: bridge accepts any absolute cwd + records it on the header; session/load
  honors the persisted cwd; bash defaults to / resolves relative against the
  session cwd; two sessions with different cwds each run bash in their own dir;
  non-absolute cwd still rejected. 100% per-file coverage maintained.
- Docs: RFC 010 status + § Deferred cwd bullet marked RESOLVED; acp README adds a
  Per-session cwd section; tool-bash + example READMEs and e2e comments updated.
This commit is contained in:
Tianyi Cui
2026-06-17 10:01:18 +08:00
parent 5e3df1b2f5
commit f3906af225
10 changed files with 165 additions and 66 deletions
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6
docs/rfc/010-acp-agent-client-protocol.md
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@@ -2,7 +2,7 @@
Status: proposed
> **Implementation status (MVP landed):** steps 1, 2, 3, 4, 6, 7, 8 are implemented in `packages/acp` + `examples/acp-agent`. **Step 5 (the `session/request_permission` permission gate) is deferred** — the bridge ships a pass-through (tools run with the executor's full authority) marked `TODO(rfc010-permission-gate)`, and lays down only the `WeakMap<Agent, sessionId>` ownership seam the gate will build on. Status stays `proposed` until the gate lands. One further best-effort limitation is tracked as `TODO(rfc010-cancel-prestep)`: `session/cancel` aborts a running step and settles the RPC as `cancelled`, but a turn still queued (not yet started) when the cancel arrives may execute before the abort takes effect, pending a loop-level pre-step cancel.
> **Implementation status (MVP landed):** steps 1, 2, 3, 4, 6, 7, 8 are implemented in `packages/acp` + `examples/acp-agent`. **Step 5 (the `session/request_permission` permission gate) is deferred** — the bridge ships a pass-through (tools run with the executor's full authority) marked `TODO(rfc010-permission-gate)`, and lays down only the `WeakMap<Agent, sessionId>` ownership seam the gate will build on. Status stays `proposed` until the gate lands. One further best-effort limitation is tracked as `TODO(rfc010-cancel-prestep)`: `session/cancel` aborts a running step and settles the RPC as `cancelled`, but a turn still queued (not yet started) when the cancel arrives may execute before the abort takes effect, pending a loop-level pre-step cancel. **Per-session `cwd` is now honored** (lifting the original "launch the server in the workspace root" restriction — see § Deferred): any absolute `cwd` is accepted and routed to the bash workdir via `session.header.cwd`, so an editor can open any project folder and N sessions can each target a different directory.
## Problem
@@ -23,7 +23,7 @@ The mapping between ACP and existing harness seams — each row names the seam a
| ACP (client ⇄ agent) | Harness seam | Notes |
|---|---|---|
| `initialize` | static handler | negotiate `protocolVersion` (echo the supported version, else error); advertise text-only `promptCapabilities` and `loadSession: true`; report agent name/version |
| `session/new {cwd, mcpServers, additionalDirectories}` → `{sessionId}` | the `dsh-agent` create factory (see Dependency note + Plan) | the seam must accept `{ sessionId, meta }` so the ACP-generated `sessionId` becomes the live/persisted session id and the validated `cwd` is attached as the `SessionHeader` (today `AgentLoop.create(id)` hardcodes `${id}-session` and takes no metadata); reject a 2nd session (single-session MVP, see RFC 011); `cwd` validated (require absolute) with "launch the server in the workspace root" documented until the workdir seam exists; `mcpServers` ignored (no `mcpCapabilities` advertised); non-empty `additionalDirectories` rejected for the MVP (the bridge cannot yet widen bash/tool filesystem scope, so silently ignoring them would desync the client's filesystem-scope UI) |
| `session/new {cwd, mcpServers, additionalDirectories}` → `{sessionId}` | the `dsh-agent` create factory (see Dependency note + Plan) | the seam must accept `{ sessionId, meta }` so the ACP-generated `sessionId` becomes the live/persisted session id and the validated `cwd` is attached as the `SessionHeader` (today `AgentLoop.create(id)` hardcodes `${id}-session` and takes no metadata); reject a 2nd session (single-session MVP, see RFC 011); `cwd` validated (require absolute) — any absolute cwd is honored: it becomes the session's `SessionHeader.cwd` and the default bash workdir (per-session cwd, see § Deferred → RESOLVED), so the server need not launch in the workspace; `mcpServers` ignored (no `mcpCapabilities` advertised); non-empty `additionalDirectories` rejected for the MVP (the bridge cannot yet widen bash/tool filesystem scope, so silently ignoring them would desync the client's filesystem-scope UI) |
| `session/load {sessionId, cwd, mcpServers, additionalDirectories}` | the `dsh-agent` resume factory (RFC 009 + Dependency note) | load `{ meta, events }`, seed the session, re-derive history via `deriveMessages()`, replay prior turns to the client as `session/update` per the ACP load contract; `additionalDirectories` rejected as in `session/new` |
| `session/prompt {prompt}` | `agent.send()` (idle) | text blocks → `TextBlock`; reject image/audio per advertised capabilities; one in-flight prompt per session |
| resolve `session/prompt` → `{stopReason}` | `agent/turn-end` (extended, see Plan) | map the harness kebab `TurnEndReason` to the ACP snake_case `StopReason` wire enum: `completed`→`end_turn`, `max-tokens`→`max_tokens`, `aborted`(cancel)→`cancelled`, plus `refusal`/`max_turn_requests` when applicable; honor the batch-into-one-turn and send-not-synchronously-running settle semantics |
@@ -54,7 +54,7 @@ Lifecycle and disposal: the connection, listeners, and in-flight permission prom
Deferred (each names its owning future work):
- Multiplexing concurrent sessions → RFC 011.
- `cwd` honoring. There is no current path from `session/new.cwd` to the bash workdir (`AgentLoop.create` takes only `AgentOptions`; `tool-bash` forwards only an explicit `args.workdir`; `LocalBashExecutor.resolve` defaults to its own config or `process.cwd()`). The MVP validates `cwd` (require absolute) and requires the server to be launched in the workspace root, erroring on a mismatch rather than silently running tools in the wrong directory; honoring an arbitrary `cwd` later means extending the agent-creation seam to carry a workdir.
- ~~`cwd` honoring.~~ **RESOLVED.** Originally there was no path from `session/new.cwd` to the bash workdir (`tool-bash` forwarded only an explicit `args.workdir`; `LocalBashExecutor.resolve` defaulted to its own config or `process.cwd()`), so the MVP validated `cwd` (require absolute) AND required the server to launch in the workspace root, erroring on a mismatch. This is now lifted: the validated `cwd` is stored as `SessionHeader.cwd`, and `dsh-tool-bash` defaults the bash workdir to the calling agent's `session.header.cwd` (an explicit model `workdir` still wins; a relative one resolves against it). Any absolute `cwd` is honored — the server need not launch in the workspace, and N sessions can each target a different directory. Widening scope beyond the single cwd (`additionalDirectories`) remains deferred.
- Client `terminal/*` proxying (a live editor terminal) and `fs/*` (editor-rendered diffs) — a future `BashExecutor` over the [ADR 0009](../adr/0009-capability-seams.md) bash seam, gated on `clientCapabilities.terminal`.
- Image/audio prompts (blocked on the DeepSeek adapter, which skips `image` blocks today), modes, auth, `available_commands`/slash-commands, `plan`, and `usage_update`.