Agent Client Protocol × DeepSeek Harness
deepseek-harness-acp
Use DeepSeek Harness from
Agent Client Protocol clients such as
Zed and
Backchat.
The adapter composes the harness in-process and maps its session-event log
onto the full ACP vocabulary: streamed text and reasoning, tool calls with
diffs and display terminals, plans, permission requests, session modes,
config options, slash commands, skills, and MCP servers. Credentials never
touch your editor config — it reuses the key you saved in the dsh Web UI, or
dsh-acp login saves one to the same store.
One package, standalone or plugin
| A · dsh profile plugin (recommended) | B · Standalone server |
|---|
| Best for | Normal installation and upgrades | Connecting an ACP client without managing a dsh profile |
| Install | dsh plugin --profile acp add @openma/deepseek-harness-acp@latest | npm i -g @openma/deepseek-harness-acp |
| Zed runs | dsh --profile acp | dsh-acp |
| Harness | The dsh that owns the profile | Your installed dsh, then the package's locked private runtime |
| Composition | dsh-base + this bundle + your profile's own patches | dsh-base + this bundle (profile machinery booted in-process) |
Both shapes share $DSH_HOME: the same credential store, settings, presets,
and session logs as dsh web — conversations started in the Web UI can be
listed and loaded from the editor.
Other dsh surfaces can mount the transport-independent
@openma/deepseek-harness-acp/plugin on their Base Host tree and own the
transport adapter. The TUI profile uses this path: it starts a separate TUI
Client process and connects ACP over that process's standard stdin/stdout; it
does not start dsh-acp or use an in-process Client stream.
The package is therefore not only a CLI wrapper. It is also the ACP surface
plugin used by other dsh applications: one Host composition can expose the
same sessions, tools, presets, skills, and persistence through a transport
chosen by the surface.
DSH compatibility
This release supports @deepseek-ai/dsh >=0.1.7-rc.2 — a minimum-version
floor declared in engines.dsh (the field dsh's own plugin loader checks, with
prereleases included), never an exact-version list. It is deliberately not a
@deepseek-ai/dsh peer dependency: npm and pnpm match peer ranges without
prereleases, so a peer floor would reject every dsh prerelease. A newer dsh is
always attempted: API differences between dsh generations are feature-detected
where they are used (for example dsh 0.2.1's subagents.drainDescendants
versus 0.2.0's drainContinuableDescendants), and a dsh newer than the newest
tested version (0.2.1-rc.2) only logs a warning. Only a dsh below the floor
is refused. CI exercises the tested profile matrix (runtime/compatibility.json)
plus the next dist-tag. The bundled runtime is
DSH 0.2.0-rc.2, including the upstream cross-process session write lock.
Runtime selection has exactly two rules (Martty issue #157):
- Standalone (
dsh-acp bin): the packaged runtime is always used —
ambient installs in the invoking directory, on PATH, or in global npm are
never consulted. An explicit --dsh-path/DSH_PATH/DSH_ACP_HOST
(or the literal value bundled) selects an installation instead, and is
refused with a message naming the version found, its source, and the
supported range when it falls outside it.
- Plugin mode (
dsh plugin add, Martty launched as a dsh plugin): the
hosting dsh is the runtime, checked against the same range at mount time;
an out-of-range host fails with the same refusal message.
The resolved runtime is always reported: the launcher logs
harness host: @deepseek-ai/dsh <version> via <source> to stderr, and the
initialize response carries agentCapabilities._meta.dsh.runtime
({base, version, source}) for clients to display.
A competing load/resume returns a standard JSON-RPC error. Closing the
session or exiting the owner process allows another process to resume it.
Every process writing shared sessions must use a fixed backend; older hosts
do not participate in this lock.
Restoring historical sessions uses the host's V3 migration, which preserves
the original log. Upgraded sessions cannot be read by older hosts.
Multi-root workspaces remain unsupported.
A · dsh profile plugin (recommended)
npm install -g @deepseek-ai/dsh
dsh web # save your API key once
dsh plugin --profile acp add @openma/deepseek-harness-acp@latest
// Zed settings.json
{
"agent_servers": {
"DeepSeek Harness": { "command": "dsh", "args": ["--profile", "acp"] }
}
}
The plugin command creates $DSH_HOME/profiles/acp, installs or upgrades the
adapter, and registers its dsh.bundle patch. The bridge mounts over
@deepseek-ai/dsh-base — the same product baseline as dsh web, with the
module-reload watcher off. Extend the profile in
$DSH_HOME/profiles/acp/cordis.patch.yml like any other dsh profile. A global
dsh-acp installation is not required for this path.
B · Standalone server
npm install -g @openma/deepseek-harness-acp
dsh-acp login # interactive; or save the key in the dsh Web UI
// Zed settings.json
{
"agent_servers": {
"DeepSeek Harness": { "command": "dsh-acp" }
}
}
The standalone binary uses the runtime archived inside this package unless a
harness is named explicitly via --dsh-path / DSH_PATH / DSH_ACP_HOST.
DSH is declared as an engines.dsh floor (see DSH compatibility), never an
npm-installed dependency: plugin mode uses the
Host's tree, while standalone maps the same imports to the private runtime.
When a real $DSH_HOME/profiles/acp exists, that profile owns the composition.
Plugin and extension model
There are two independent ways to extend an ACP-backed surface.
To use portable Agent Plugins, Codex plugins, Claude Code plugins, or Pi
packages through an ACP client, add the
Agent Plugins Bridge to the
same profile:
dsh plugin --profile acp add @openma/dsh-agents-plugins-bridge@latest
The Bridge contributes ordinary Host rows. Imported commands, skills, tools,
hooks, MCP connections, agents, and Pi extensions therefore reach ACP through
this adapter's existing projections; there is no ACP-specific plugin import
runtime. The Bridge's Web management panel and MCP Apps HTML renderer remain
Web surfaces and are not sent over ACP.
For extensions that need a session-owned background lifecycle without an open
terminal UI, use
Martty owner.
It is a generic ACP rpc client: this package remains the server/transport,
while Martty owns the long-lived Session and explicit startup/shutdown slash
commands.
Extend the Host composition
The ACP adapter rides the Cordis tree that the profile already owns. Add dsh
plugins to that profile to change the agent composition instead of forking the
ACP server: providers and models join the live catalog, commands and skills
join the advertised session surface, tools and subagents appear through
standard session/update, and the same session persistence remains available
to every surface.
For applications embedding ACP, the public package entries are:
| Export | Role |
|---|
@openma/deepseek-harness-acp/plugin | Complete Host-side surface plugin. It fills the ACP-required Host services that Base leaves to a surface and provides ctx.acpServer. It does not claim a transport. |
@openma/deepseek-harness-acp/server | Lower-level transport-independent acpServer provider for a Host tree that already supplies the injected composition services. |
@openma/deepseek-harness-acp/stdio | Standard profile adapter: connects ctx.acpServer to process stdin/stdout. |
@openma/deepseek-harness-acp/bridge | Node stream adapter and compatibility entry for older profile patches. |
ctx.acpServer.connect(stream) creates a connection-owned bridge fiber over
the existing Host composition. The transport owner retains process, stream,
and TTY lifecycle; the ACP plugin retains session and agent semantics. This is
the shape used by
@openma/deepseek-harness-tui:
ACP stays on the Base Host tree while a separate TUI Client process owns its
own Cordis tree.
Adding a Cordis service does not automatically invent a wire method. Prefer a
standard ACP capability or event projection whenever one exists; add an
adapter only for behavior that must cross the client boundary.
Extend ACP without breaking ordinary clients
Optional wire behavior follows ACP's extension conventions:
- Advertise support in
initialize metadata, with a namespaced and versioned
capability such as _meta.dsh.cordis.protocol.
- Carry annotations on standard messages in namespaced
_meta fields when no
new request is needed.
- Name custom JSON-RPC requests and notifications with a leading underscore,
and send them only after both peers negotiated the matching capability.
- Keep the standard ACP path complete. A client that does not advertise an
extension must still get normal sessions, prompts, updates, cancellation,
auth, and config options.
DSH tool result values
The ACP metadata registry is the authoritative list of
every _meta field this adapter reads or emits. It records direction, carrier,
shape, negotiation requirements, and replay behavior, including native DSH
tool values at _meta.dsh.toolResult.value.
The current package applies this pattern to the built-in _dsh/cordis/*
family used by the TUI for Client capability discovery, dynamic Package
lifecycle, and package-private Host/Client RPC. It is an explicit, versioned
extension—not a synchronization of Cordis plugin ids, fibers, or inject
across processes. The bridge's internal method registry is not currently a
public arbitrary-extension API; new extension families should first define a
stable capability, ownership, lifecycle, and fallback contract.
Authentication
No keys in editor config, no secrets pasted into chat. ACP clients follow
the protocol: initialize advertises the Agent Auth methods the client
declared it can use.
- API key —
api-key, or api-key:<provider> per live route. The
client may pass _meta["api-key"].apiKey.
- Terminal —
terminal-login, when the client declares
clientCapabilities.auth.terminal (or _meta["terminal-auth"]). The
client runs the advertised dsh-acp login command itself — the adapter
never supplies a command path — and the saved key is picked up on the
next authenticate or session/new.
- Browser —
browser, only when the client declares
clientCapabilities.elicitation.url. The adapter starts a localhost
sign-in page and hands its URL to the client through url elicitation —
headless, SSH, and WSL sessions all see the URL. The secret never
travels over ACP; the page's own timeout bounds the wait, and a decline
or cancel ends the flow with auth_required instead of hanging.
- Custom gateway —
gateway, only when the client opts in with
clientCapabilities.auth._meta.gateway === true. The client sends
_meta.gateway { baseUrl, headers, providerName? }.
The adapter writes credentials to the harness store. Missing credentials
fail session/new and session/prompt with auth_required (-32000)
carrying data.authMethods — the same advertised list — so the client can
open its auth UI from any failure. Typing a native auth command
(/login, /logout) gets a plain "isn't available in this environment"
reply pointing at the client's sign-in/sign-out and ends the turn — it is
never advertised, never reaches the model, never changes credentials, and
never returns auth_required.
logout is scoped to one provider route — the one named by
_meta.provider, or the active provider when omitted — and clears only
that provider's stored key and gateway base-URL. Re-authenticating
overwrites the same provider's credential; authenticating a second
provider adds alongside the first; dsh-acp login --provider <route>
replaces it out of band. The active method, provider, and credential name
are pushed to the client as _auth/status_update whenever they change.
- Harness credential store —
$DSH_HOME/.credentials.yaml (mode 600),
the file the dsh Web UI writes; hot-reloaded. Save a key with
dsh-acp login [--provider <route>], or the Web UI (Settings → Models).
- Process environment —
DEEPSEEK_API_KEY / DEEPSEEK_BASE_URL (and
the matching ANTHROPIC_API_KEY / OPENAI_API_KEY for those routes) in
the environment that launches the agent.
The credential gate is the current provider route. An Anthropic-only
store is enough for an Anthropic session; a DeepSeek key does not unlock
another provider.
Features
- Streaming — assistant text and reasoning deltas; assembled-message fallback.
- Images —
promptCapabilities.image is advertised when the composition mounts ctx.attachments (dsh-base does). ACP image blocks are validated, stored with saveImage, and kept in wire order with surrounding text. resource_link stays a textual file pointer.
- Tool calls — ACP kinds, human titles, file locations, real diffs from fs-tool hunks, raw input/output; command output on a display terminal when the client supports one, fenced output otherwise.
- Permission presets as session modes —
read-only / workspace-write / danger-full-access, each a named {sandbox, approval} pair recorded as a durable session fact (also exposed as a config option for clients that only render those).
- Agent composition — when the profile mounts
agentPresets, an uncategorized config option id: "agent" lists the roster (standard / code / minimal / cordis, plus user copies). Switching rebuilds the agent live with history preserved. Authoring (copy/rm) stays on the Web settings page; there is no /preset slash.
- Live model catalog — providers × models from the running composition (third-party providers added in the Web UI appear immediately), plus reasoning-effort selection that follows your product default. Model option ids are stable: bare model ids while one provider is registered,
provider::model as soon as there are several — never keyed on the current default provider (which every switch rewrites), so an id a client cached keeps working. Bare ids are still accepted on input and resolve to the provider that serves them.
- Slash commands — adapter built-ins (
/status, /model) plus the harness command registry (/compact, /goal, /permission, /plan, …) executed without a model turn, plus skills (/skill-name — the harness's own invocation gesture). Login and logout are ACP methods, not chat commands.
- Plans & usage —
todo_write snapshots as ACP plans; token accounting as usage_update and per-turn usage.
- Sessions —
session/resume restores a durable session without replaying its transcript; remains the full-history path. Also supports , silent restore when a client prompts an old session after an agent restart, and titles as . Multi-root sessions are not advertised: non-empty on , , , or return until .
Configuration
Flags win over environment variables, which win over defaults. All optional —
with no flags, sessions follow your product defaults (settings.yaml).
| Flag | Env | Default | Purpose |
|---|
--dsh-path | DSH_PATH | auto-detect | DeepSeek Harness installation |
--provider | DSH_PROVIDER | product default | Provider route override |
--model | DSH_MODEL | product default | Model override |
--max-tokens | DSH_MAX_TOKENS | provider default | Per-request output-token cap |
--permission-mode | DSH_PERMISSION_MODE | workspace-write | Initial permission preset |
--reasoning-effort | DSH_REASONING_EFFORT | product default | off / high / max |
| — | DEEPSEEK_API_KEY | — | API credential (fallback to the credential store) |
| — | DEEPSEEK_BASE_URL | DeepSeek endpoint | OpenAI-compatible endpoint override |
| — | DSH_ACP_DEBUG | off | Verbose stderr diagnostics |
Subcommands: dsh-acp login [api-key] (interactive when omitted; input never
echoes), dsh-acp update (self-update via npm).
Permissions and sandboxing
Sessions start in workspace-write: bash and file mutations are confined to
the session's cwd (plus shared temp roots), and a model retry requesting
wider access raises an ACP permission request. Always allow (this
session) flips the approval policy to never for that session.
danger-full-access disables both the sandbox and the prompts — use it only
in disposable checkouts or containers. Each level is one durable preset
(sandbox + approval together), the same three the Web UI offers.
Architecture
ACP client (Zed, …)
│ ACP JSON-RPC over stdio
▼
dsh-acp
├─ src/bin.ts selects one DSH tree before Host imports evaluate
├─ src/profile-boot.ts boots the harness's own profile machinery
│ (dsh-base + this bundle + $DSH_HOME layers)
├─ src/harness.ts host discovery (DSH_PATH → cwd → PATH → npm -g → bundled runtime)
└─ src/bridge/ the ACP bridge (a cordis plugin)
├─ index.ts sessions, prompts, cancel, modes, options,
│ commands, credentials, MCP mounts
├─ translate.ts session-event → ACP update projection (pure)
├─ history.ts stored-log replay for session/load (pure)
├─ fork.ts session/fork meta, message lookup, inclusive cut (pure)
└─ prompt.ts ACP prompt blocks → harness content blocks (pure)
▼
external or package-bundled dsh (agent spine, llm, persistence, sandbox,
tools, presets, skills, compaction, …)
When embedded by another surface, only the transport edge changes:
dsh Base Host Cordis tree
├─ product plugins (agents, tools, skills, persistence, …)
└─ @openma/deepseek-harness-acp/plugin
└─ acpServer.connect(Stream)
│ standard ACP + negotiated extensions
▼
surface-owned Client process
The bridge consumes the harness session/event firehose — the same
append-only log persistence stores — so live streaming, history replay, and
session/list agree by construction. All harness modules, including cordis
itself, load from one host tree: plugin and service identity is never split
across copies.
Development
npm install # dev deps include the harness packages (types + tests)
npm run typecheck # tsc --noEmit
npm test # vitest: unit + e2e smoke (boots the real composition; no model calls)
npm run build # esbuild → dist/
To also run the e2e suite against a standalone host install:
npm install --prefix /tmp/dsh-host @deepseek-ai/dsh
DSH_ACP_TEST_HOST=/tmp/dsh-host npm test
Live iteration: paired profiles
Keep the profile your editor uses on the published package, and point a
second profile at this worktree via a pnpm symlink:
dsh plugin --profile acp add -w @openma/deepseek-harness-acp # stable
dsh plugin --profile acp-test add -w "link:$PWD" # dev (symlink)
The dev loop is npm run build + restart — dist/ and cordis.patch.yml
are read through the link. (pnpm treats file: as a copy install and caches
same-version tarballs; link: avoids both.)
{
"agent_servers": {
"DeepSeek Harness": { "command": "dsh", "args": ["--profile", "acp"] },
"DeepSeek Harness (dev)": { "command": "dsh", "args": ["--profile", "acp-test"] }
}
}
Automated compatibility review
When .github/workflows/dsh-update.yml opens a new bundled-dsh upgrade PR, it automatically dispatches a Cursor cloud agent to review ACP compatibility with the new dsh version. The agent:
- Reads dsh release notes and API changes between versions
- Tests the ACP adapter with the new dsh version
- Pushes fixes directly to the PR branch if needed
- Posts a verdict comment on the PR (safe to merge / safe after fixes / not safe)
This requires the CURSOR_API_KEY organization or repository secret (a Cursor API key from the Cursor Dashboard). If the secret is not configured, the workflow skips the agent dispatch with a warning and leaves the PR open for manual review.
The agent uses the Cursor Cloud Agents API v1 with workOnCurrentBranch: true to push directly to the PR's head branch without creating a new branch or PR.
To manually test the review workflow on an existing PR, trigger the workflow via Actions → Update bundled dsh → Run workflow and provide the PR number. The dispatch logic lives in scripts/dispatch-cursor-review.sh.
License
Apache-2.0.
