The DeepSeek Harness SDK agent demo exposed as an **Agent Client Protocol (ACP)** server over JSON-RPC stdio — drive it from Zed or any other ACP client.
The leaf config loads the ACP app, DeepSeek adapter, plan mode, sandboxed bash, the sandboxed filesystem stack, approval and permission services, model-facing tools, and repeat guard. The app bundles the agent spine, JSONL persistence, and bridge, creates agents on `session/new`, and keeps stdout logger-free. [`fs.cordis.yml`](fs.cordis.yml) adds local tool-result spill storage for its dedicated scenarios; [`code-mode.cordis.yml`](code-mode.cordis.yml) adds `run_code` and its generated TypeScript SDK. See [Code Mode](../../packages/core/tools/README.md#code-mode).
This example loads **no stdout logger** — `stdout` carries the JSON-RPC frames, and any other write corrupts them. `@deepseek-ai/dsh-acp-demo` includes no logger entry, so this leaf has none to get wrong by default; do not add one (use a stderr exporter if you need logs).
The editor sets each session's `cwd` to the project it opens. That directory is both bash's default workdir and the session's primary `workspace-write` boundary: every bash or filesystem mutation carries one policy resolved from the calling session, so a single server process may serve concurrent projects. Projects outside the platform temporary areas do not grant either session writes into the other; `/tmp` and `os.tmpdir()` remain shared writable scratch roots under `workspace-write`, so projects placed there are not mutually isolated ([writable-root contract](../../packages/sandbox/sandbox/README.md)). The configured `workspaceRoot: process.cwd()` remains the fallback for calls without a session cwd. The filesystem tools ride the same policy through [`@deepseek-ai/dsh-fs-sandbox`](../../packages/fs/fs-sandbox/), so `read`/`write`/`edit` are available under every mode and confined to the same policy.
The same `demo:acp` server composes [`@deepseek-ai/dsh-plan-mode`](../../packages/plan/plan-mode/), so a capable client advertises `default` and `plan` in its mode picker. ACP owns those protocol ids and projects them onto the plugin's boolean plan state. This composition owns the complete plan instructions in [`cordis.yml`](cordis.yml): remain in plan mode, inspect before asking, avoid mutations, resolve discoverable repository facts, and submit a decision-complete plan through `exit_plan_mode`. Those are the instrumental behaviors shared by the local Codex and Claude Code references; product-specific plan files, phase machinery, and protocol tags stay out of the plugin contract.
Plan mode adds only that configured guidance section. Every tool, including `exit_plan_mode`, keeps the same schema while plan mode is inactive or active; the exit tool describes itself as plan-only and rejects if called while inactive. Stable native schemas and Code Mode SDK bindings avoid tool-catalog churn at the transition. `ask_user_question` carries blocking user-owned choices through ACP elicitation, while `exit_plan_mode` renders the exact logged plan for approval and returns keep-planning feedback to the model. The mode picker and permission select remain independent: switching plan state never changes sandbox or approval state, and deployments that need a hard read-only planning floor configure that policy separately. The [plan-mode Agent Note](../../.agents/notes/implemented/feature/2026-07-07-plan-mode.md) owns the state and review contract.
This example hosts the ACP snapshot suite, including the picker advertisement and both plan-review branches. It replays through `dsh-llm-replay`, which reconstructs model streams from `assistant/chunk` events in each scenario's session JSONL. Recording runs the real ACP agent and harvests its logs; refresh keeps the committed transcript as mock input and rewrites current replay outputs. `replay.override.json` covers throw and hang cases that chunks cannot express, and an optional `workspace/` seeds files. The [snapshot Agent Note](../../.agents/notes/implemented/testing/2026-06-19-acp-snapshot-tests.md) owns the ACP harness design.
The default tree composes [`@deepseek-ai/dsh-sandbox-local`](../../packages/sandbox/sandbox-local/), [`@deepseek-ai/dsh-sandbox-policy`](../../packages/sandbox/sandbox-policy/), [`@deepseek-ai/dsh-bash-sandbox`](../../packages/bash/bash-sandbox/), [`@deepseek-ai/dsh-fs-sandbox`](../../packages/fs/fs-sandbox/), [`@deepseek-ai/dsh-user-approval`](../../packages/ui/user-approval/), and [`@deepseek-ai/dsh-permission`](../../packages/ui/permission/). Bash and the `read`/`write`/`edit` tools start in `workspace-write`; a denied operation returns a structured marker, and a retry with `sandbox_permissions` plus `justification` becomes a one-shot `session/request_permission` prompt in the editor. "Allow once" runs exactly that retry under the wider mode ([sandbox Agent Note § Escalation](../../.agents/notes/implemented/feature/2026-07-06-sandbox.md)).
- **One session config option is live**: a capable client shows one `Permissions` select. `workspace-write` means workspace-confined bash plus `ask`; `danger-full-access` means unconfined bash plus `never`. Switching writes one `permission/preset` event through to the sandbox-mode and approval-policy events, and `session/load` reports the resumed value.
- **Every approval is one-shot**: the choices are `Allow once` and `Reject`; a dismissal, rejection, missing editor, or unavailable runner fails closed.
- **The boundary spans bash and the filesystem tools per session**: bash confines through the OS runner and the `read`/`write`/`edit` tools through an in-process path fence ([`dsh-fs-sandbox`](../../packages/fs/fs-sandbox/)); both receive the calling session's cwd as `workspaceRoot`.
`tests/escalation.e2e.ts` boots this default tree keyless, drives the permission select, and—with a key and usable runner—proves both approval outcomes against the filesystem. The agent-spine e2e independently boots one context with two home-directory project sessions and world-verifies concurrent own-root success plus sibling-root denial through both shipped tool families. The keyless `session-sandbox-root` ACP snapshot places its generated project under the user home while an overlay points the deployment fallback at `/tmp`; its successful `workspace-write` call proves the assembled app used the session cwd. Most snapshots start at `danger-full-access` so bash fixtures remain runner-independent. No fixture pins real runner denial text because its dialect is platform-specific.
The bridge supports N concurrent sessions per connection, each with its own `cwd` (RFC 011). Prompts support ACP's baseline `text` and `resource_link` blocks only; `additionalDirectories` and `mcpServers` are rejected. See [`packages/ui/acp/README.md`](../../packages/ui/acp/README.md) for the full contract.
