acp-extension-dsh

ACP session controls and a pinned coding profile for DeepSeek Harness.

The package is a Cordis plugin, not a replacement for Harness. It adds ACP model, reasoning-effort, permission, and agent-preset selectors, accepts inline images when DeepSeek-V4-Flash-Vision-Exp is selected, and mounts ACP-provided stdio or Streamable HTTP MCP servers into each Harness Agent scope. Harness continues to own model execution, sandbox enforcement, persistence, preset composition, tool execution, and one-shot approvals.

The adapter advertises Core's _meta.lody.compaction capability and translates Harness compaction/start and compaction/end events into a standard ACP tool lifecycle carrying _meta.lody.activity. Manual and automatic compaction remain distinguishable, and failed compactions keep the Harness error reason. Committed assistant images are read back through the attachment store and sent as ACP image blocks. Prompt completion and cancellation wait for admission, Harness idle, and ordered output delivery before releasing the session's prompt slot.

ACP model choices are discovered from Harness when each session is created and returned through both the standard model config option and the legacy ACP models response. Exact per-model metadata controls the reasoning selector and image admission, and the legacy response carries model[effort] entries so a host can cache the reasoning choices for every model rather than only the model that happened to be active during the probe. Permission choices use the composed Harness preset table. When DEEPSEEK_BASE_URL is set, the adapter requests its OpenAI-compatible GET /models endpoint once per ACP connection, resolves every advertised id through Harness, and selects the first result initially. Discovery is bounded, does not follow redirects, and reports an actionable startup failure when the endpoint cannot provide a usable list. Without an endpoint, the Harness catalog remains advisory: an explicitly configured or selected model is still resolved even when it is not listed.

The ACP host mounts Harness's file-backed settings provider. It reads $DSH_HOME/settings.yaml, falling back to ~/.dsh/settings.yaml, and exposes user sections to settings-aware plugins. Missing settings preserve composition defaults; malformed settings documents fail startup instead of being silently ignored. The llm-deepseek.models array replaces the local catalog in full, so retain any default models and their vision metadata that should remain selectable. For example:

llm-deepseek:
  models:
    - id: deepseek-v4-flash
      name: DeepSeek-V4-Flash
    - id: deepseek-v4-pro
      name: DeepSeek-V4-Pro
    - id: deepseek-v4-flash-vision-exp
      name: DeepSeek-V4-Flash-Vision-Exp
      inputModalities: [text, image]
    - id: custom-model
      name: Custom model

The provider watches file edits, but ACP model choices are cached per connection. Reconnect and refresh the host's model capabilities after catalog edits. DEEPSEEK_BASE_URL still selects endpoint discovery: this setting does not merge local-only model IDs into an endpoint's /models response. API credentials remain in the host environment; generated compositions contain no credentials.

Exports

• acp-extension-dsh exports the Cordis plugin: apply, inject, and name.
• acp-extension-dsh/capabilities exports the selector vocabulary for host UIs.
• acp-extension-dsh/profile exports the pinned Harness package set and ACP host-composition builder.

The host launches the pinned dsh-acp-demo executable with the generated composition and stages this package's official standard/code/minimal/cordis preset snapshot beside the ACP adapter. Harness mounts the selected preset per session and also discovers user presets below $DSH_HOME/.agent-presets. MCP tools use Harness's native mcp__<server>__<tool> naming and are removed with their owning ACP session.

The generated profile defaults session persistence to upstream's zstd encoding. A host that reuses an existing Harness session root may pass none to the profile builder only after verifying that the root contains raw session.jsonl artifacts and no session.jsonl.zstd artifacts. Harness roots are single-encoding stores: hosts must refuse mixed roots without moving, rewriting, or deleting user artifacts.

The ACP profile keeps the session-query service mounted for exact reads but sets its full-text SQLite index to openAt: never. This composition does not expose the session-search tool, and public Node distributions cannot be assumed to include SQLite FTS5. Disabling the unused index prevents ACP startup from depending on that optional SQLite build feature.

Development

npm install
npm run build
npm test
npm run format:check

Node.js 22 or newer is required.

The optional real-runtime settings regression test uses a preinstalled profile closure. Install every package in DEEPSEEK_HARNESS_NPX_PACKAGES at DEEPSEEK_HARNESS_VERSION in a separate directory first, then run:

DSH_TEST_RUNTIME_ROOT=/absolute/runtime/node_modules npm run test:settings-profile

The test itself uses isolated temporary homes, synthetic settings, and ACP initialization/session creation only. It does not install packages, use API keys, send model requests, or edit the user's Harness home. It checks first-request catalog visibility, absent settings, invalid YAML, non-mapping settings documents, and preservation of the settings document. The profile's ACP entry explicitly waits for settings so catalog discovery cannot race the initial file read.

Plan configuration

Core’s boolean plan_mode option is available only when the current Agent preset mounts the native Plan service. It calls planMode.set, preserves sandbox/approval settings, and publishes durable Plan changes as config updates. A pending selection is reflected until its next-step commit; Plan is guidance, not a sandbox policy.