Generic multi-provider adapter for the harness LLM seam backed by [`@earendil-works/pi-ai`](https://www.npmjs.com/package/@earendil-works/pi-ai). One plugin instance owns a dict of provider profiles keyed by route; every request selects a profile with `GenerateOptions.provider` and resolves `GenerateOptions.model` against that route's configured catalog. A route naming an installed pi-ai provider inherits its endpoint, wire protocol, and model catalog as defaults and overrides them field by field; a route pi-ai does not ship is declared outright, so an OpenAI-compatible gateway, a self-hosted server, or a provider newer than the installed catalog is configuration rather than a code change.
Configure credentials, the model catalog, and deployment-specific transport settings per provider, keyed by the provider route itself. Prefer `apiKeyEnv` — a credential *reference* resolved per request — over a literal `apiKey`, so no secret enters this file. Omitting **both** is what leaves the route unauthenticated, which for an installed catalog route means pi-ai's provider-native ambient discovery; a configured reference that resolves to nothing fails the request with `MISSING_CREDENTIAL` instead, because falling through would authenticate with whatever unrelated key the environment happens to hold. One credential serves every model on its route.
The dict shape makes duplicate routes unrepresentable, and the pre-release array shape (with per-profile `provider` fields) fails load with migration directions. `providers` may also be empty or omitted entirely: the adapter then mounts **dormant** — zero routes, no extra catalog entries — and registers routes the moment the `llm-pi-ai:` settings section supplies profiles, dropping them again when it empties. Dormant or not, the plugin declares every installed catalog provider in the configurable-provider directory (`ctx.llm.listConfigurableProviders()`, settings path `providers.<provider>`), joined with every route the current profiles declare, so configuration surfaces can offer the full catalog before any route exists and can still address a hand-declared one. Which adapters exist is composition; which providers run can be entirely the user's settings document. Registration with `ctx.llm` is atomic: a collision with any provider route already owned by another adapter fails plugin loading without registering the remaining routes. Model ids are not lifecycle config; a model the route does not configure fails before any provider request with `LlmError('UNKNOWN_MODEL')`.
## Catalog resolution
A profile's `models` list *replaces* the route's installed catalog rather than extending it; omitting it (or leaving it empty) serves that catalog unchanged. Each entry defaults its unset fields from the installed model of the same `id`, so narrowing a catalog route to two models, correcting one capacity, or adding a model newer than the installed catalog are all one-line edits. Only the fields the harness consumes are configurable — `id`, `name`, `contextWindow`, `maxTokens`, and `reasoning`; pricing and input modalities have no harness consumer and ride the installed entry or are absent, while reasoning-level spellings and OpenAI-compatibility quirks have no configuration surface at all because restating them cannot be validated.
Resolution fails loud, naming the offending route and model, when a route cannot be served: a model the installed catalog does not describe needs an explicit `contextWindow` and `maxTokens`, and a route the catalog does not ship needs `api`, `baseURL`, and a non-empty `models` list. `api` accepts the protocols in `supportedProtocols()` — pi-ai's own streaming API set — and is only needed when the catalog cannot supply one: a model absent from the catalog inherits the protocol its shipped siblings agree on, so adding a model to a single-protocol catalog route restates nothing.
`baseURL` sets the endpoint of every model on the route, so private proxies such as `https://proxy.example.com:8443` remain supported; a catalog route that omits it keeps each catalog model's own endpoint. Naming `api` on a catalog route repoints the whole route at that protocol, which is how a deployment moves a provider between, say, Responses and Chat Completions.
The adapter reads its profiles through a thunk **once per operation** instead of freezing them at construction. The plugin registers the `llm-pi-ai` namespace on the optional `ctx.settings` seam with this same `Config` schema and its `cordis.yml` entry as the composition `base`, and because `providers` is a dict, the base and the user's `llm-pi-ai:` settings section merge **per provider**: a user can add a route, override one field of a composition route, or point a route at another proxy, all effective on the next request with no restart. Without a mounted settings service the entry config alone drives the adapter, unchanged.
Credentials resolve per stream call: a non-empty literal `apiKey` wins, then `apiKeyEnv` through the optional `ctx.credentials` seam (`$DSH_HOME/.env` under the live environment; exactly that variable without a mounted seam). A profile naming no credential at all — and only that case — defers to pi-ai's ambient discovery. The route set and each route's captured retry policy are the registration-level facts: when either changes, the plugin replaces its registration atomically (same adapter instance, candidate set validated first), so a route another adapter already owns leaves the previous routes serving and reverting to a working configuration re-applies. Provider key order never counts as a change. A live settings snapshot naming an unknown provider (or failing any other resolver bound) keeps the last good profiles and logs the failure; the entry config itself still fails plugin load.
The adapter exposes each configured route's models through `ctx.llm.listModels(provider)`. This is provider-neutral selector metadata read from the same pi-ai `Models` collection the request path uses, so discovery does not create a second model registry. `ctx.llm.resolveModelInfo(provider, model)` performs that exact descriptor lookup once and returns its identity, context window, configured output cap, and selectable thinking levels, keeping authoritative metadata on the route-owning adapter rather than its consumers. A model's `maxTokens` becomes the seam's `defaultMaxTokens`, so a request that names no output cap carries the configured one.
The `reasoning.efforts` list is pi-ai's ordered `getSupportedThinkingLevels(model)` result without filtering or normalization, including `off` and the model-specific availability of `xhigh` or `max`. The Harness exposes each canonical pi-ai level as an opaque ID; provider/model wire spellings remain inside pi-ai's `thinkingLevelMap`. A non-reasoning model therefore exposes pi-ai's `off` choice. The profile `reasoning` value, including `off`, is the deployment default when configured; omitting it preserves the provider default. Per-request `GenerateOptions.reasoningEffort` takes precedence, and any explicit value absent from the exact model capability fails with `UNSUPPORTED_REASONING_EFFORT` before network I/O instead of being clamped. pi-ai's common stream options represent `off` by omitting `reasoning`.
Supported profile fields are `apiKey`, `apiKeyEnv`, `displayName`, `api`, `baseURL`, `models`, `headers`, `reasoning`, `thinkingBudgets`, `cacheRetention`, `transport`, `timeoutMs`, `websocketConnectTimeoutMs`, `streamIdleTimeoutMs`, and `retryPolicy`. Each profile's optional retry policy is captured with that provider route; omission uses bounded normal defaults. The stream-idle interval is a positive finite Node timer delay, defaults to five minutes, and covers only an outstanding provider read, not consumer think time. Harness app attribution wins a conflicting configured header name.
The adapter forces pi-ai's SDK `maxRetries` to zero so one `stream()` call makes one provider request. The removed profile fields `maxRetries` and `maxRetryDelayMs` fail load instead of silently multiplying or hiding the separately composed agent-level retry budget. Idle expiry aborts the SDK's stable request signal and surfaces `TIMEOUT`; an earlier caller abort remains `ABORTED`.
Each resolved route contributes one pi-ai `Provider` to the adapter's `createModels()` collection, and requests reach the provider through `Models.streamSimple()`. A catalog route that keeps its catalog protocol **reuses** the installed provider with its model list replaced, because that provider owns API implementations this package cannot reconstruct — Bedrock loads its Smithy module through a separate entry point — so rebuilding it from parts would silently narrow which providers work. Every other route is built by `createProvider()` over the protocol table behind `supportedProtocols()`, whose entries are the same factories pi-ai's own provider factories use.
Credentials never enter that collection. The harness resolves a route's key through its own seam before the request reaches pi-ai and passes it as the request's `apiKey` option, which pi-ai treats as the highest-priority auth override; `Models` therefore holds no credential store, and the harness keeps its fail-loud reference semantics. A route naming no credential resolves as configured-but-keyless and leaves the requirement to the protocol, which is where it actually lives.
The selected model descriptor supplies the protocol implementation. This includes native API differences such as OpenAI models whose descriptor uses the Responses API rather than Chat Completions; the harness adapter does not hardcode endpoint selection by model name.
Successful assistant responses store a versioned, lossless-JSON replay state beside their durable provider/model provenance. At request time, `LlmService` passes replay state only when the historical provider route and target provider route are currently owned by this same `PiAiAdapter` instance. The adapter validates the state and restores pi-ai response ids and provider signatures even when the target provider or model changes; pi-ai then decides which metadata its target API can reuse. History without replay state is translated as foreign provider-neutral content and never impersonates a native pi-ai response.
If a listener rewrites assembled assistant content, the loop drops replay state before logging the message because its provider metadata no longer describes the content. Invalid versions, malformed metadata, provenance provider/model mismatches, and content/block mismatches fail explicitly with `LlmError('INVALID_REPLAY_STATE')`.
- pi-ai reports failures as in-stream error events; these map to `finish {kind:'error'|'aborted', failure}` chunks. Provider-specific error text distinguishes terminal `QUOTA` from transient `RATE_LIMIT`, while text and usage signals evaluated against the resolved model's context window normalize overflow to `CONTEXT_WINDOW_EXCEEDED`. A terminal `stop` whose message carries no content blocks maps to a `finish {kind:'error'}` with code `EMPTY_RESPONSE` (retried by default policy) instead of a successful empty message.
Every request carries the shared attribution header from dsh-llm's `attributionHeaders()`, merged through pi-ai's `headers` stream option. Provider-specific app-attribution headers are not synthesized. See [dsh-llm § App attribution](../llm/README.md#app-attribution-attributionts).
pi-ai installs several provider SDKs and lazy-loads the one selected by the catalog model. The dependency weight is isolated to this opt-in adapter package.
The selected catalog model receives `GenerateOptions.system`, history, tools, and sampling fields supported by pi-ai's common streaming API. This package adds no prompt prose. Provider-native replay metadata is restored only when the adapter validates it for the historical content.
Provider tokenization governs exact input. Conversion adds no model-visible text; replay metadata may let a native API reuse provider-side state.
#### KV Cache effect
Conversion preserves logical request order without adding text, while the selected provider's serialization and replay state determine reuse. Changing adapter instance, provider, model, or any upstream request token may prevent reuse from the first difference.
pi-ai events become harness reasoning, text, tool-call, usage, and finish chunks. Parsed tool arguments cross the harness boundary as raw JSON strings.
#### Token effect
Generated content affects later inputs only after the loop records it. pi-ai folds reasoning tokens into output usage when the provider does not report them separately.
Recorded response content appends to the next request and does not invalidate its earlier reusable prefix. Unrecorded transport metadata and usage accounting do not affect cache identity.
- **Settings can add or override routes, not remove composition routes** — the user layer merges over the composition `base`, so deleting a `cordis.yml`-provided provider is a composition change; `replace` on the namespace only resets the user layer.
- **`headers` can carry a credential the redactor never sees** — the profile's `headers` dict is plain strings, so `Authorization` or `api-key` set there is returned verbatim by a redacted `describe()` and rendered by any configuration UI. Store credentials as `apiKeyEnv` references; making the dict write-only is deferred with the rest of the [wire-boundary work](../llm/README.md#known-limitations-and-deferred-work).
- **Model discovery is configuration, not a provider query** — the route's catalog is whatever `settings.yaml` says; nothing fetches a provider's `/models` endpoint, so a model list is only as current as its last edit. A one-shot discovery action that offers a provider's live list for the user to adopt belongs to the configuration surface and is deferred with it.
- **One wire protocol per route** — `api` applies to the whole route, so a mixed-protocol catalog route (an OpenAI-style catalog spanning Responses and Chat Completions) cannot host a model of the other protocol, and adding a model such a route does not describe requires naming `api` and moving every model onto it. Splitting the provider across two route keys is the workaround.
- **An unauthenticated route depends on its protocol** — naming no credential resolves the route as configured-but-keyless, but pi-ai's OpenAI-compatible implementation still requires an API key or an `Authorization` header, so a keyless local server needs a placeholder `apiKey` or an `Authorization` entry in `headers`.
- **`GenerateOptions.stop` is unsupported** — pi-ai's common stream options cannot guarantee stop-sequence behavior across providers, so the adapter rejects the field.
- **In-history `system` messages use pi-ai's common context conversion** — provider-specific placement follows pi-ai rather than a harness-owned wire override.
- **Provider HTTP status is unavailable** — pi-ai error events do not expose a stable HTTP status across providers; failures expose only stable harness error codes.
- **Retry policy is provider-owned, not an SDK retry** — each provider profile may configure nested `retryPolicy`, which `dsh-llm-retry` executes at the agent failed-step seam; pi-ai SDK retries stay disabled so durable agent steps and `llm/retry` events own every visible attempt, and direct `ctx.llm.stream()` calls remain single-attempt.
