# dsh-llm

English | [中文](README.zh.md)

Provider-neutral LLM vocabulary and abstract service. This package defines the canonical language spoken by the agent loop, session logs, and every plugin.

## Service: `LlmService` (ctx key: `llm`)

An adapter registry plus a single streaming call surface, interceptable via a waterfall event.

### Public API

- `ctx.llm.registerAdapter(providers: string[], adapter: LlmAdapter): () => void` Register one adapter instance for the given provider routes. Registration is all-or-nothing, and is disposed with the calling fiber.
- `ctx.llm.listProviders(): LlmProviderInfo[]` Describe registered provider routes in registration order.
- `ctx.llm.providerRetryPolicy(provider: string): ResolvedRetryPolicy` Return the provider-owned retry policy captured during registration, with normal defaults resolved.
- `ctx.llm.listModels(provider: string): Promise<LlmModelInfo[]>` Discover the models one registered provider currently advertises.
- `ctx.llm.resolveModelInfo(provider: string, model: string, signal?: AbortSignal): Promise<LlmResolvedModelInfo>` Resolve validated exact-model identity plus available context and reasoning metadata from the owning adapter, with optional cancellation for asynchronous adapters.
- `ctx.llm.resolveCallConfig(config: LlmCallConfig, signal?: AbortSignal): Promise<LlmCallConfig>` Validate an explicit effort and materialize an adapter-configured default without clamping.
- `ctx.llm.prepareCall(config: LlmCallConfig, signal?: AbortSignal): Promise<PreparedLlmCall>` Resolve a config and capture its current adapter registration as one cancellable, one-shot call.
- `ctx.llm.stream(options: GenerateOptions): AsyncIterable<StreamChunk>` Stream one model call as raw chunks (token-level deltas). Consumers assemble the chunks into blocks/messages with `BlockAssembler`.

`LlmService` preserves errors from final adapter selection, synchronous dispatch, iterator construction, and iteration, and binds their provenance to the exact stream handle returned for that model call. `isLlmAdapterFailure(stream, value)` reports only errors from that call's final adapter boundary; `llmFailureOf(stream, value)` returns the adjacent immutable `LlmFailure`; `llmRetryPolicyOf(stream)` returns the immutable policy of the exact registration selected at that boundary, even if the route is later disposed or replaced. A call that never reaches a final adapter has no serving policy. Nested model calls, `llm/stream` middleware, and downstream consumer failures remain unclassified for the outer call. Classification never replaces or mutates the adapter's original coded `Error`.

Provider and model metadata is a discovery surface, not a routing whitelist. `registerAdapter()` still owns provider exclusivity and captures the adapter's retry policy for each route, while an adapter may accept model ids absent from `listModels()`; consumers must not reject a request because its model is unlisted. Returned selector metadata is detached and invalid or duplicate adapter entries fail with `INVALID_ADAPTER` or `INVALID_CATALOG`.

Exact-model metadata is a separate correctness query, not a catalog decoration or global LLM setting. `resolveModelInfo()` asks the adapter that owns the exact provider/model route once; an adapter can describe an unlisted dynamic model, and absent `context` or `reasoning` fields mean only that those capabilities are unavailable. Invalid identity, context, or reasoning metadata fails with `INVALID_MODEL_INFO`, `INVALID_MODEL_CONTEXT`, or `INVALID_MODEL_REASONING`.

Reasoning identifiers are opaque adapter-owned strings rather than a core enum. An adapter publishes its ordered selectable list, including an `off` id when that model's capability API exposes one. `resolveCallConfig()` accepts only an exact advertised identifier, materializes `defaultEffort` when present, and otherwise preserves the provider default. Asynchronous model resolvers receive the caller's signal and must settle promptly after cancellation. `prepareCall()` additionally retains the exact adapter registration through header logging and terminal dispatch, so HMR cannot combine one adapter's capability result with another adapter's request; reusing its one-shot handle or changing its call-config fields fails with `INVALID_PREPARED_CALL`. An unsupported explicit or configured effort fails with `UNSUPPORTED_REASONING_EFFORT` before provider I/O.

### Events

| Event | Mode | Purpose |
|---|---|---|
| `llm/stream` | waterfall | Intercept/wrap every streaming model call for caching, logging, or routing |

### Extension points

- Subclass `LlmAdapter` and call `ctx.llm.registerAdapter(providers, adapter)` to add one or more provider routes. `GenerateOptions.provider` selects the adapter; `GenerateOptions.model` is adapter-owned and may be resolved dynamically. Override `providerRetryPolicy()` to supply provider-owned recovery configuration, `providerInfo()` and asynchronous `listModels()` to expose selector metadata, then implement `resolveModel()` when exact identity, capacity, or selectable reasoning efforts are available; an asynchronous resolver must honor its optional cancellation signal. The defaults use bounded normal retry policy, use the route and model ids as names, advertise no models, and return no capacity or reasoning metadata.
- Wrap `llm/stream` via `ctx.on()` waterfall listeners for caching, logging, or routing. A wrapper that retries after emitting a chunk has no durable attempt boundary; shipped agent retry policy therefore uses `agent/request-error` instead.

### Messages (`message.ts`) and content blocks (`types.ts`)

`Message` is the shared immutable value used by delivery, durable history, and model requests. Every message has a required `MessageId`, role, content, and typed source from creation onward. `createMessage(input)` mints the identity and returns a detached deep-frozen value; `createUserMessage({ content, source })` fixes the user role; `createAssistantMessage({ content, source })` fixes the assistant role and model source kind; `createToolResultMessage({ callId, content, isError })` fixes the user role and couples the tool source to its result block; `freezeMessage(message)` imports an identity that already exists and never replaces it. Message rewrites preserve the identity and produce another frozen value. Browser code imports these value constructors from the dependency-minimal `@deepseek-ai/dsh-llm/message` entry instead of the service-bearing package root.

Message content is an array of typed blocks: `text`, `reasoning`, `tool-call`, `tool-result`. The union is derived from the merge-extensible `ContentBlockMap`, so plugins can add block types via declaration merging. Assistant messages use a model source carrying provider/model provenance and optional adapter-private replay state. Before dispatch, `LlmService` retains that state only when the historical provider route and target provider route are currently owned by the exact same adapter instance; the adapter then decides whether it can restore or convert the state across models/providers. The core block set is limited to blocks every shipping path honors — multimodal content (images, audio, …) has no core block type; a feature that needs one adds it via the map together with the adapter/UI/compaction support that honors it.

Streaming is a raw chunk protocol (`block-start`, `text-delta`, `reasoning-delta`, `tool-call-delta`, `block-end`, `usage`, `finish`). `BlockAssembler` is the single shared implementation that assembles chunks into blocks/messages.

### Call configuration (`call-config.ts`)

`LlmCallConfig` is the provider, model, optional adapter-owned reasoning effort, and sampling scalars of one conversation's requests (`provider`, `model`, `reasoningEffort`, `temperature`, `maxTokens`, `stop` — each mapping 1:1 onto the same-named `GenerateOptions` field). It is per-conversation state recorded in the session log as part of the request header (see the dsh-session `request/header` events), never a silently-adjustable per-call knob: the `agent/request` waterfall proposes a replacement, `prepareCall()` validates and defaults it under the turn signal, and the loop logs the effective value before using the prepared call's registration-bound stream. `callConfigEquals(a, b)` is the field-wise real-change detector; `deepFreeze(value)` is the ownership helper the loop applies to every built request before dispatch (`llm/stream` listeners and adapters read, never rewrite). `markAgentLoopRequest()` gives that exact object process-local loop provenance, and `isAgentLoopRequest()` lets observers distinguish it from independently logged auxiliary calls that may also be frozen and session-associated. `GenerateOptions.purpose` classifies logged auxiliary compaction and session-title calls so adapters can apply purpose-specific transport policy without changing ordinary conversation requests.

### App attribution (`attribution.ts`)

Every product adapter sends application identity on provider HTTP requests. `attributionHeaders(identity?)` builds the standard `User-Agent`, defaulting to public `APP_IDENTITY`; white-label deployments may replace but not suppress it. Adapters verify the wire header directly or through their library hook. See [the attribution Agent Note](../../../.agents/notes/implemented/architecture/2026-06-21-mandatory-app-attribution-headers.md).

### Classes

- `LlmAdapter` — abstract base class for provider adapters. The only required method is `stream()`.
- `BlockAssembler` — incrementally assembles raw chunks into complete content blocks and can create an identified, frozen assistant message from them. The agent loop feeds it raw chunks (logging them for replay) while reading the assembled blocks for history.
- `HarnessError` — base class for the harness error taxonomy: a stable `code` string (distinct from the human `message`) plus `cause` chaining. Lives here, in the leaf package every other imports, so a single base is shared without a new dependency edge. Per-package errors (`LlmError`, `ToolArgsError`, `InvariantError`, …) extend it. `isHarnessError(value)` narrows at seams.
- `LlmError` — extends `HarnessError`; its stable `code` string (`NO_ADAPTER`, `DUPLICATE_ADAPTER`, and adapter codes like `AUTH`/`RATE_LIMIT`) matches its frozen serializable `failure.code`. The payload may also retain validated status, `Retry-After`, and branded provider request id facts; policy remains outside the error.
- `errorChain(value)` — renders a thrown value with its full `cause` chain and AggregateError members for diagnostic surfaces (UI notices, logger lines, durable `turn/end` messages), so transport wrappers like undici's `TypeError: fetch failed` surface the underlying `ECONNREFUSED`/DNS/TLS detail instead of masking it. Rendering only — route on `code`, never by parsing the result.
- `CONTEXT_WINDOW_EXCEEDED_CODE` — the provider-neutral code both DeepSeek adapters use when a request exceeds the model context window, regardless of thrown-HTTP versus in-band finish delivery. `isContextWindowExceededError(detail)` is their shared conservative classifier for OpenAI-compatible provider detail.
- `QUOTA_EXCEEDED_CODE` — the non-transient provider-neutral code for exhausted account quota, balance, credits, budget, or usage limits. `isQuotaExceededError(detail)` keeps those failures distinct from request-rate limits.
- `EMPTY_RESPONSE_CODE` — the provider-neutral code both adapters use for a degenerate provider completion: a terminal `stop` that carried no content blocks at all. Classified as an error finish (not a successful empty message) because the attempt produced nothing durable; `dsh-llm-retry` retries it by default.

### Real adapters

Two adapters implement `LlmAdapter` on different internals: [`@deepseek-ai/dsh-llm-deepseek`](../llm-deepseek) uses direct fetch with `eventsource-parser` SSE framing for the `deepseek` route, while [`@deepseek-ai/dsh-llm-pi-ai`](../llm-pi-ai) dynamically resolves configured provider/model pairs through `@earendil-works/pi-ai`. Both follow the `StreamChunk` conventions in `types.ts`: usage precedes finish, tool arguments remain raw strings, and errors take one of two sanctioned paths. See [the twin LLM adapters](../../../.agents/notes/implemented/architecture/2026-06-13-twin-llm-adapters.md) for the design rationale.

## Model Experience

None, as the service adds no model-bound text, schema, or message; it only materializes and logs an adapter-configured reasoning effort.

#### KV Cache effect

Pass-through; the registry preserves the assembled request prefix, while the selected adapter and provider own cache reuse and routing boundaries.

## Known Limitations and Deferred Work

- **No retry execution, caching, or rate limiting ships in this service** — provider registration stores retry policy, but `llm/stream` remains a single-attempt call-wrapper seam. The agent loop separately offers proven model-request failures to `agent/request-error`, whose default preserves the original failure; `@deepseek-ai/dsh-llm-retry` is the optional executor loaded by the shared example spine.
- **`GenerateOptions` sampling is `temperature`/`maxTokens`/`stop` only** — no `tool_choice`, `top_p`, or penalty fields; the vocabulary grows when a producer lands ([dropped inert knobs](../../../.agents/notes/archived/simplification/2026-07-04-drop-inert-request-knobs.md)).
- **Producer-gated variants stay out until produced** — `prefill`, per-tool `strict`, block `cache` hints, and the `agent` message-source variant were pruned as producerless ([Agent Note](../../../.agents/notes/archived/simplification/2026-07-04-prune-producerless-vocabulary-variants.md)).
- **`BlockAssembler` handles core block kinds only** — a plugin-added block type whose stream is never closed by `block-end` makes `blocks()` throw.
- **`APP_IDENTITY.url` names a repository that does not exist yet** — `FIXME`: creating the public `deepseek-ai/deepseek-harness-sdk` repo gates the first release.
- **`GenerateOptions.sessionId` is a locally-declared brand** — importing dsh-session's `SessionId` would cycle; a future ids-owning package would dissolve the workaround.
