feat(acp): honor per-session cwd — run each ACP session in its own workspace
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:
@@ -24,8 +24,8 @@ It is a **client-driver / UI plugin**, the structured analogue of the readline `
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| ACP method | Harness seam | Notes |
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|---|---|---|
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| `initialize` | static | negotiate `protocolVersion`; advertise text-only `promptCapabilities` and `loadSession: true` |
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| `session/new` | `ctx.agents.create({ sessionId, meta:{cwd} })` | creates a new session/agent; N concurrent sessions are allowed (RFC 011), keyed by id; `cwd` must be absolute AND equal the server launch dir; `additionalDirectories` rejected; `mcpServers` ignored |
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| `session/load` | `ctx.agents.resume(...)` | replays the persisted event log to the client as `session/update` — the USER side (`user/message` → `user_message_chunk`), assistant text/reasoning (`assistant/chunk`), and tool calls/results (`tool/call` + `tool/result`). Re-loading an already-live id is rejected; the id's load slot is reserved (`loadingIds`) BEFORE the async resume so a pipelined load of the SAME id can't leak a second agent (distinct ids load concurrently); the PERSISTED header `cwd` is validated via a metadata-only `list()` BEFORE resume (not just the requested `cwd`), so a mismatch rejects without ever constructing an agent. After the async resume a `closed` re-check refuses to install a record if the bridge tore down mid-load |
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| `session/new` | `ctx.agents.create({ sessionId, meta:{cwd} })` | creates a new session/agent; N concurrent sessions are allowed (RFC 011), keyed by id; `cwd` must be absolute (it becomes the session's workspace — see Per-session cwd); `additionalDirectories` rejected; `mcpServers` ignored |
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| `session/load` | `ctx.agents.resume(...)` | replays the persisted event log to the client as `session/update` — the USER side (`user/message` → `user_message_chunk`), assistant text/reasoning (`assistant/chunk`), and tool calls/results (`tool/call` + `tool/result`). Re-loading an already-live id is rejected; the id's load slot is reserved (`loadingIds`) BEFORE the async resume so a pipelined load of the SAME id can't leak a second agent (distinct ids load concurrently). The resumed session keeps its PERSISTED header `cwd`, so its bash tools run in the original workspace; the requested `cwd` only needs to be absolute. After the async resume a `closed` re-check refuses to install a record if the bridge tore down mid-load |
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| `session/prompt` | `agent.send()` | text-only; rejects image/audio and empty prompts; one in-flight prompt PER session (independent); settles on the OWNING turn's end (a turn that ends in `error` rejects the RPC) |
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| `session/cancel` | `agent.abort()` | aborts a running step + settles the prompt `cancelled` for ONLY that session — a cancel never touches another session's stream or prompt (see limitation below) |
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| `session/update` | `session/event` | `agent_message_chunk` (text-delta), `agent_thought_chunk` (reasoning-delta), `user_message_chunk` (load replay), `tool_call`/`tool_call_update` |
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@@ -36,6 +36,10 @@ The bridge multiplexes N sessions over one connection. Live sessions are held in
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Background-task isolation rides on `dsh-tool-bash`: bash task ids are global and predictable, so the tool layer records each background task's owning agent and `bash_output`/`bash_kill` reject a task owned by a different agent — one session's agent can't read or kill another's task.
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## Per-session cwd
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Each session runs in its own workspace, recorded as the session's `SessionHeader.cwd`. On `session/new` the (absolute) request `cwd` becomes that header cwd; on `session/load` the resumed session keeps its PERSISTED header cwd (the request `cwd` is only shape-checked — it does not override the stored one), and a load whose persisted session has no absolute cwd is REJECTED up front via a metadata-only `list()` check, BEFORE resume constructs an agent (else bash would silently fall back to the server's launch dir, and a post-resume reject would leak the registered agent). `dsh-tool-bash` then defaults the bash workdir to the calling agent's `session.header.cwd` (an explicit model `workdir` still wins; a relative one resolves against the session cwd; with no session cwd the executor falls back to its own config / `process.cwd()`). So the server no longer has to be launched in the workspace — an editor can open any project folder, and N sessions over one connection can each target a different directory. (`additionalDirectories` is still rejected: widening the tool/filesystem scope beyond the single cwd is a separate sandbox concern.)
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## Settle-exactly-once
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A `session/prompt` resolves (or rejects) exactly once, keyed off the canonical session log (the `session/event` stream), NOT the `agent/turn-start`/`agent/turn-end` events. One listener captures the prompt's owning turn from the log's `turn/start` and settles on the matching `turn/end` — the one signal that always fires (`closeTurn` appends it unconditionally, even when a boundary emit throws and the `agent/turn-end` EVENT is skipped). A prompt settles only on ITS OWN turn (`inflight.turn === turn/end.turn`), so a stale `turn/end` for a previously-cancelled turn whose end arrives late can never settle the wrong prompt. A turn that ends `error` REJECTS the RPC with an internal error carrying the failure message (ACP has no error stop reason); every other reason resolves via the codec. As a fallback, when the agent settles to `idle`/`disposed` with a prompt still pending — e.g. a `session/event` listener registered before the bridge threw and starved the bridge's listener — an `agent/status` handler reconciles the prompt from the log (the owning turn's `turn/end`, or `cancelled` if the turn was torn down without one). An empty/whitespace prompt is rejected up front — it would queue no work, so no turn would start and the RPC would hang.
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@@ -49,7 +53,7 @@ Teardown reaches quiescence: for EVERY live session settle any pending prompt as
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- **`TODO(rfc010-permission-gate)`** — the `tools/execute` permission gate (`session/request_permission`) is NOT implemented; tools run with the executor's full authority. The `agent→sessionId` reverse map is in place so the gate can route a permission request (which receives only `exec.agent`) back to its originating session. RFC 010/011 stay `proposed` until the gate (and per-session permission ownership) land.
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- **`TODO(rfc010-cancel-prestep)`** — `session/cancel` (and teardown/disconnect) is honest RPC/UI cancellation plus best-effort abort: a *running* step is aborted, but a turn that is queued-but-not-yet-started (the gap before `agent.abort()` has an `AbortController` to signal) may still run to completion. This same window means disposal/disconnect can return while one short queued turn per session still runs, and a prompt accepted right after a pre-step cancel can be batched into the cancelled turn (the loop merges queued messages into one turn). A loop-level queue-aware cancel will close this; the single-in-flight-per-session rule bounds the worst case to one extra prompt per session.
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- **`TODO(rfc010-agent-disposal)`** — the factory (`ctx.agents.create`/`resume`) returns no per-agent disposer, so teardown aborts+drains each agent but cannot individually unregister it; on a bare client disconnect (no host dispose) the idled agents linger in `ctx.agents` until the host context disposes. A reconnect spins up a fresh context, so this strands no work; a per-agent disposal seam is the follow-up.
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- **`cwd`** — only the server's launch directory is honored; a `session/new.cwd` (or a persisted `session/load` header cwd) that differs is rejected (RFC 010 § Deferred — no path from session cwd to the bash workdir yet).
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- **`additionalDirectories`** — rejected. A session operates in its single `cwd` (see Per-session cwd); widening the tool/filesystem scope to extra roots is a separate sandbox concern, not yet implemented.
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## stdout is the protocol
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