deepseek-harness/packages/llm/llm-deepseek/README.md

@deepseek-ai/dsh-llm-deepseek

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DeepSeek chat-completions adapter for the harness LLM seam: direct fetch + SSE (framed by eventsource-parser) translating the official wire format (source of truth: the API docs — guides/thinking_mode, guides/tool_calls, api/create-chat-completion) into the StreamChunk protocol.

A second, library-backed implementation of the same seam exists in @deepseek-ai/dsh-llm-pi-ai. This package owns the deepseek-official provider route — deliberately distinct from pi-ai's catalog name deepseek, so one composition can mount both DeepSeek paths side by side; registering another adapter for deepseek-official itself still throws LlmError('DUPLICATE_ADAPTER').

The package root exposes the Cordis plugin contract and DeepSeekAdapter; wire serialization, SSE parsing, and chunk translation helpers are not part of that root contract.

Config

- id: llm-deepseek
  name: '@deepseek-ai/dsh-llm-deepseek'
  config:
    apiKeyEnv: DEEPSEEK_API_KEY  # default; resolved per request via ctx.credentials, then the environment
    baseURL: https://api.deepseek.com # optional; $DEEPSEEK_BASE_URL then the public API when omitted
    thinking: enabled        # optional; provider default is enabled
    reasoningEffort: high    # optional; off | high | max — omitted ⇒ high
    maxTokens: 256000        # optional positive per-request output cap; this is the default
    streamIdleTimeoutMs: 300000 # optional; positive finite Node timer delay; five-minute default
    retryPolicy:             # optional; omission uses bounded normal defaults
      mode: always           # normal | always
      backoff:
        initialDelayMs: 500
        maxDelayMs: 10000
        jitterRatio: 0.1
    defaultContextWindow: 1000000 # optional positive-integer fallback; this is the default
    models:                  # optional; defaults to V4 Flash and V4 Pro
      - id: deepseek-v4-flash
        name: DeepSeek-V4-Flash
      - id: private-reasoner
        description: Company-hosted reasoning model
        contextWindow: 512000

The plugin registers the single provider route deepseek-official together with its resolved retryPolicy. A request selects it with provider: deepseek-official; its model is passed through as the wire model string, so changing DeepSeek models does not require lifecycle-time registration. Omitting models advertises deepseek-v4-flash as DeepSeek-V4-Flash and deepseek-v4-pro as DeepSeek-V4-Pro, each with a 1,000,000-token context window; an explicit list replaces those defaults, while models: [] advertises none. Catalog entries are exposed through ctx.llm.listModels('deepseek-official') for clients such as ACP editors and the Web selector, but remain advisory: unlisted model ids still pass through unchanged. An omitted entry name defaults to its id.

contextWindow is optional per configured model and is not exposed through the advisory catalog. ctx.llm.resolveModelInfo('deepseek-official', model).context returns an exact model value first, then defaultContextWindow for an entry without capacity or an unlisted pass-through id. The adapter default is 1,000,000; pressure-sensitive plugins therefore get deployment-owned capacity without treating the model selector as authoritative. Registering another adapter for deepseek-official throws LlmError('DUPLICATE_ADAPTER').

maxTokens is the adapter-configured output cap for conversation requests and defaults to 256,000. Exact-model resolution exposes it as defaultMaxTokens; LlmService materializes that value into GenerateOptions.maxTokens before the agent loop writes request/header, so the wire request remains reconstructable. An explicit request or AgentOptions.maxTokens value wins and is serialized as max_tokens. The adapter does not clamp this request budget against contextWindow; deployments with a smaller context or provider output limit must configure a compatible maxTokens.

The same exact-model result exposes ordered off, high, and max efforts under reasoning for every pass-through model when deployment policy permits thinking. reasoningEffort selects the deployment default and falls back to high when omitted. agent/request can replace it on each conversation step; the resolved value is logged in request/header. high and max enable thinking and serialize as the official top-level reasoning_effort; adapter-owned off instead serializes thinking.type: disabled and omits reasoning_effort. An unsupported value fails with UNSUPPORTED_REASONING_EFFORT before network I/O.

thinking: disabled is a deployment lock that publishes only off with off as its default. Omitting reasoningEffort or configuring it as off is valid; configuring high or max fails plugin loading, and a direct per-request attempt to enable thinking fails before network I/O. A request with GenerateOptions.purpose: 'session-title' also forces thinking disabled and omits the already-resolved effort, reserving its bounded output for visible title text without changing conversation or compaction defaults.

streamIdleTimeoutMs bounds each outstanding provider read, including the initial fetch, without counting time the consumer spends between chunks. One stable abort signal reaches the request and body reader for the whole call; expiry stops the transport and throws LlmError('TIMEOUT'), while an earlier caller abort throws LlmError('ABORTED'). The adapter makes exactly one provider request per stream() call; it registers the configured policy as provider metadata, and dsh-llm-retry separately executes it at durable agent-step boundaries.

Dynamic configuration (settings + credentials)

Connection facts are not frozen at load. resolveAdapterOptions is the one explicit resolve step from raw config to validated facts, and the adapter re-reads them through a thunk once per operation: base URL, catalog, request defaults, and idle budget all take effect on the next request, while an in-flight stream keeps the facts it started with. Two optional seams feed that thunk:

• ctx.settings — the plugin registers the llm-deepseek namespace with this same Config schema and its cordis.yml entry as the composition base, so a llm-deepseek: section in the user settings document overrides any field without a restart. Without a mounted settings service the entry config alone drives the adapter, unchanged. A live settings snapshot that passes the schema but fails a beyond-schema bound (a duplicate catalog id, a broken thinking/effort pair) keeps the last good facts and logs the failure; the entry config itself still fails plugin load.
• ctx.credentials — the API key resolves per stream call, from the same resolved snapshot that supplies the endpoint. Configuration carries only apiKeyEnv, never a literal key: the reference resolves through the credential seam, and without a mounted seam through the trusted environment layers. Because credential facts travel with the connection facts, a settings snapshot the resolver rejects contributes neither its endpoint nor its key: the whole previous generation keeps serving. A request with no key anywhere fails with MISSING_CREDENTIAL naming every configuration entry point, while the route stays registered and the catalog stays browsable — first-run onboarding is "browse models, store the key, prompt again", with no restart between.

The one registration-captured fact is the retry policy: when its resolved value changes, the plugin re-registers the route in place (same adapter instance, one synchronous section), so ctx.llm.providerRetryPolicy('deepseek-official') always reports the current policy.

The plugin also declares its route in the configurable-provider directory (ctx.llm.listConfigurableProviders()): provider deepseek-official, settings namespace llm-deepseek, empty settings path — the whole section is the profile. Configuration surfaces use that entry to offer this adapter alongside dormant pi-ai providers.

App attribution

Every request carries the shared attribution header from dsh-llm's attributionHeaders() - the mandatory User-Agent baseline identifying the harness (see dsh-llm § App attribution). Direct DeepSeek requests and OpenAI-compatible gateway requests get no provider-specific app-attribution headers under this adapter contract; OpenRouter app attribution is deferred to a future explicit OpenRouter adapter or mode. A request whose GenerateOptions.purpose is compaction (dsh-compact-basic's auxiliary summarization call) additionally carries x-deepseek-harness-compact: 1, so the host can separate compaction traffic from conversation requests.

Wire-format notes (verified live + against the official docs)

• Streaming only (stream_options.include_usage always on). usage may arrive attached to the finish chunk or as a trailing usage-only chunk — the translator defers both to [DONE], so usage always precedes finish and nothing follows finish.
• The adapter-owned off effort maps to thinking: {type: 'disabled'} and never crosses the wire as reasoning_effort: 'off'.
• The first thinking-mode chunk carries reasoning_content: "" — handled (no spurious reasoning block).
• Reasoning passback rule: on assistant turns that carried tool calls, reasoning_content is serialized back in history (required by the API in thinking mode); on tool-call-free turns it is dropped (ignored anyway — saves tokens).
• Cache accounting: cacheReadTokens ← prompt_cache_hit_tokens / prompt_tokens_details.cached_tokens; DeepSeek reports no cache-write metric.

Errors

Non-2xx responses throw LlmError with stable codes: AUTH (401/403), QUOTA (a response whose provider details identify exhausted quota, balance, or credits), RATE_LIMIT (other 429s), CONTEXT_WINDOW_EXCEEDED (a 400 whose provider code, type, or message identifies context overflow), INVALID_REQUEST (other 400s), SERVER (5xx), HTTP_<status> otherwise. Its serializable failure retains the HTTP status plus a valid positive Retry-After seconds/date delay and x-request-id / x-deepseek-request-id when present. A pre-response transport failure (DNS, refused connection, TLS, proxy) throws TRANSPORT naming the configured endpoint and chaining the original rejection as cause; caller aborts throw ABORTED, and the loop's cancellation signal remains authoritative. Protocol violations throw STREAM_CLOSED (no [DONE]) or MALFORMED_RESPONSE (bad JSON payload). Unknown wire finish_reasons (e.g. content_filter, insufficient_system_resource) become finish {kind: 'error', failure} chunks, and a completed stream whose stop (or absent) finish opened no content blocks becomes a finish {kind: 'error'} with code EMPTY_RESPONSE (retried by default policy).

Testing

Unit suites run against a local node:http mock SSE server (no network), including dynamic high/off/max selection, structured HTTP facts, malformed/truncated streams, caller abort, connection failure, and proof that idle timeout aborts the actual body. tests/dynamic-config.spec.ts drives real settings-local and credentials-local providers (next-request base-URL/key pickup, literal precedence, keyless onboarding, last-good snapshots, retry-policy re-registration), and tests/loader-composition.spec.ts boots the full chain from a test-only cordis.yml through the actual Loader and edits settings.yaml/.env on disk. Real-API coverage lives in tests/adapter.e2e.ts (pnpm run test:e2e, key-gated): V4 Flash + V4 Pro across thinking enabled/disabled and both official effort levels, including the thinking+tools round trip with reasoning passback and a request whose key exists only in a credentials-local document.

Model Experience

DeepSeek request

What the model sees

The selected DeepSeek model receives the harness system prompt, message history, tool schemas, stop sequences, and call config without adapter-authored prompt prose. On a prior assistant turn with tool calls, its reasoning content is passed back as required; reasoning from tool-call-free turns is omitted.

Token effect

Provider tokenization governs exact input. Conditional reasoning passback increases tool-round-trip context, while dropping other reasoning avoids paying those tokens again; cache-read usage is reported when available.

KV Cache effect

An unchanged assembled prefix is eligible for DeepSeek cache reuse, which this adapter reports in usage. A model-route change or any upstream prompt, schema, prefix, or history change may prevent reuse from the first changed token; reasoning passback appends during tool round trips.

DeepSeek response

What the model sees

Reasoning, text, and raw-string tool arguments are translated into harness chunks for the loop to log and assemble.

Token effect

Generated tokens follow the request's logged reasoning effort and maxTokens; only loop-retained blocks affect later input.

KV Cache effect

Loop-retained response blocks append to the next request and preserve its earlier reusable prefix; dropped blocks have no later cache effect. Changing the provider or model selects a different cache domain.

Known Limitations and Deferred Work

• A settings models list replaces the composition list wholesale — settings-layer merging is per-field, and arrays are one field; per-entry catalog merging would need a keyed shape.
• tool_choice is not mapped — not part of the core vocabulary (MVP cut, shared with the pi-ai twin).
• Requests use raw fetch, not @cordisjs/plugin-http — no shared proxy/interception configuration; adoption is deferred until a second adapter wants it (TODO(http)).
• Serialization flattens user and tool-result content to text blocks — plugin-added block types are skipped, and empty tool output crosses the wire as the literal (no output).