# Agent Note: pi-ai routes are declared providers, not catalog lookups

Status: implemented

English | [中文](2026-08-03-pi-ai-declared-provider-catalog.zh.md)

## Problem

`dsh-llm-pi-ai` treated the pi-ai package's generated catalog as the boundary of what could be configured. A route key had to name an installed provider (`resolveProfiles` rejected anything else), model listing returned `getBuiltinModels(provider)` verbatim, and request-time model resolution looked the id up in that same catalog and overrode only `baseURL`. Three consequences followed, and all three were dead ends rather than gaps: an OpenAI-compatible gateway, a self-hosted server, or a provider newer than the installed catalog could not be configured at all; a model the catalog had not caught up with failed with `UNKNOWN_MODEL` even against a correct endpoint; and a model's context window and output cap were whatever the pinned pi-ai release said, so a deployment could neither correct a stale value nor supply one for a model pi-ai had never described. Upgrading the package was the only way to move any of it.

The adapter also streamed through `streamSimple` from `@earendil-works/pi-ai/compat`, an entry point whose own module documentation declares it a temporary compatibility surface — its catalog reads are `@deprecated`, and it is deleted when pi-ai finishes its `ModelManager` migration. The three configuration limits and the deprecated dependency have the same fix, because pi-ai's supported runtime (`createModels()` / `createProvider()`) is built around a provider being *declared* rather than looked up.

## Decision

A provider route is a **declaration**, and the installed catalog is its default. `resolveProfiles` no longer checks route keys against `getBuiltinProviders()`. Instead each route resolves to a materialized model list plus the pi-ai `Provider` that serves it:

- `catalog.ts` merges the installed catalog under the profile's own entries. A profile's `models` list *replaces* the route's catalog (an absent or empty list serves it unchanged), and each entry defaults its unset fields from the installed model of the same `id`. Only the fields the harness consumes are configurable — `id`, `name`, `contextWindow`, `maxTokens`. Pricing and input modalities are absent from the surface because nothing reads them: `replay.ts` zeroes pi-ai's cost metadata and `context.ts` keeps only text blocks. Reasoning is absent for a different reason: a bare capability flag would make pi-ai advertise effort levels with no `thinkingLevelMap` to spell them, so it rides the installed entry or is absent. Materialization spreads the installed entry and overrides those four fields, rather than enumerating the result: an enumerated rebuild silently drops every `Model` field this package does not model, which is how `headers` went missing from an nvidia route once already.
- `provider.ts` builds the route's `Provider`. A catalog route that keeps its catalog protocol **reuses** the installed provider with `getModels()` replaced; every other route is built by `createProvider()` over a protocol table whose entries are the same `@earendil-works/pi-ai/api/*.lazy` factories pi-ai's own provider factories use. That table is narrower than pi-ai's full API set on purpose — it holds only protocols a profile can completely describe with a key, an endpoint, and headers, so Bedrock (SigV4 plus a region), Vertex (project, location, ADC), Azure (provider environment plus an api-version), and Codex (OAuth) are absent rather than offered as routes that cannot authenticate. Catalog routes still reach them through their own provider; only an explicit override is refused.
- `adapter.ts` turns each resolution into an **immutable snapshot** — the profiles plus a `createModels()` collection holding those providers — and every operation captures a whole snapshot before its first `await`.
- A model's **explicitly configured** `maxTokens` becomes the seam's `defaultMaxTokens`. The value inherited from the installed catalog does not: pi-ai requires `Model.maxTokens` as the model's output *capability*, while `defaultMaxTokens` is a cap the deployment chose to send on requests that name none, and materializing the former as the latter would start capping every request at a number nobody picked.

### Snapshots, not a shared collection

`Models.streamSimple()` resolves its provider lazily, when the returned stream is first consumed — which is after the adapter has awaited the route's credential. A single collection mutated in place would therefore let a request that started under one configuration finish under another, or fail on a provider that no longer exists, even though `llm.prepareCall()` already froze that step's config and captured its adapter registration. A configuration change builds a *new* collection and leaves the one in use alone, so the seam's per-step freeze holds all the way down: switching models mid-reply takes effect on the next step, never inside the one in flight.

### The directory replaces atomically

The configurable-provider directory follows the profiles, so it changes whenever a declared route appears or leaves. Withdrawing the old registration and making a new one cannot express that: a candidate set the registry refuses — a profile keyed `deepseek-official`, which `llm-deepseek` already declares — would leave this plugin's whole directory withdrawn and the Models page empty, silently, because the settings-change callback contains the failure. `registerConfigurableProviders` therefore returns a handle carrying `replace(entries)` with the same validate-the-candidate-set-first atomicity `registerAdapter` has, and the plugin uses it. A refused swap costs a diagnostic; the previous entries keep serving.

Resolution fails loud and names the route and model at fault: a model the catalog does not describe falls back to the route's own `defaultContextWindow`/`defaultMaxTokens`, so a listing that discloses nothing but ids still yields a serviceable route; a route the catalog does not ship needs `api`, `baseURL`, and a non-empty `models` list. Because the built `Provider` is part of the resolution result, a protocol or model error keeps the last good route set serving, exactly as a bad settings snapshot already did.

The configurable-provider directory is now the installed catalog **joined with** every route the current profiles declare, re-registered when that set changes. Without the join a hand-declared route would have no settings address and no configuration surface could show or edit it.

### A capability whose only level does nothing is reported unavailable

pi-ai reports a model with no reasoning metadata as supporting the single level `off`, and the adapter used to pass that straight through. It reaches the seam as a one-item effort list, which every surface renders as a picker holding one selectable control — and that control is a lie: `off` becomes an *omitted* reasoning option at dispatch, byte-for-byte the request that naming no effort already produces. A provider whose own default is to think keeps thinking while the surface shows `off` selected.

`reasoningInfo` therefore omits the seam's `reasoning` field whenever `model.reasoning` is falsy. The condition is the model's own metadata, not where the model came from, so this covers every hand-declared model **and** the 251 installed-catalog models pi-ai marks as non-reasoning. Those previously offered the lone `off`; they now offer nothing, and the surface shows the provider default alone. Models that do carry reasoning metadata are untouched — their level list still crosses the seam unfiltered, `off` included, because there it selects between real alternatives.

### Credentials stay outside pi-ai

pi-ai's `Models` carries its own credential concept — a `CredentialStore` keyed by provider id, with `envApiKeyAuth` resolving `credential.key ?? env(VAR)`. Adopting it would have created a second credential source of truth beside `ctx.credentials` and, worse, reintroduced the ambient fallback the harness deliberately forbids: a named-but-missing `apiKeyEnv` must fail with `MISSING_CREDENTIAL` rather than authenticate with whatever unrelated key the environment holds.

`ModelsImpl.applyAuth` honours `options.apiKey` as the request's key, but only through a provider that declares an api-key method: `resolveProviderAuth` short-circuits to that method when the override is present, and otherwise falls through to the credential store and then to ambient discovery, returning nothing — and so failing the request with `Provider is not configured` — when the provider has no api-key method at all. The harness therefore resolves the route's key through its own seam, as before, and passes the result as the request's `apiKey`; the collection is constructed with no credential store.

A route's auth follows from that. A catalog route keeps the installed provider's own `auth`, which preserves provider-native ambient discovery for a profile naming no credential, and keeps it through an `api` override too: which environment a provider reads is a property of the provider, not of the wire format its models speak. The exception is a catalog provider with no api-key method — `openai-codex` authenticates through OAuth alone — where a profile that names a credential also gets the harness method beside the provider's own, because otherwise its configured key would be refused before any request went out. A keyless profile on such a route adds nothing and keeps the honest refusal: this adapter holds no OAuth store to resolve through. A hand-declared route gets a harness-owned `ApiKeyAuth` that reports configured-but-keyless rather than unconfigured, leaving the requirement to the protocol — which is where it lives: pi-ai's OpenAI-compatible implementation still demands a key or an `Authorization` header, and says so itself.

## Alternatives considered

- **Keep `createProvider()` but skip the `Models` collection**, streaming through `provider.streamSimple(model, ctx, {apiKey})`. Smallest diff and the credential path is untouched, but `createProvider`'s `auth` is a required field that this path never invokes — a required-by-signature implementation with no caller. It also leaves `refreshModels` needing a hand-built `RefreshModelsContext`, and keeps the adapter off the runtime pi-ai actually supports.
- **Reuse the installed provider for catalog routes and `createProvider()` only for declared ones**, with no shared resolution. Zero risk to catalog behavior, but catalog materialization, endpoint override, and per-model configuration would each exist twice, and a catalog route that repoints its protocol would have to jump paths mid-resolution. The chosen split confines the asymmetry to provider construction, where it is forced by pi-ai not exposing a built provider's API implementations.
- **Rebuild every route through `createProvider()`**, including catalog ones. Fully symmetric, but a built `Provider` does not expose its `api`, so the protocol table would become the ceiling on which providers work — Bedrock loads its Smithy module through a separate entry point and would silently stop working.
- **Expose pi-ai's whole `Model` shape** (cost, input modalities, `thinkingLevelMap`, `compat`). Maximum configurability, but no current consumer reads those fields, so a configured price or modality would change nothing while reading as supported.

- **Keep one mutable `Models` collection and re-sync it.** Fewer allocations, and correct for every operation that resolves synchronously. It is exactly wrong for the one that does not: `stream()` awaits a credential between capturing its model and dispatching it.
- **Simulate an atomic directory swap with dispose-then-register.** No seam change, and it works whenever the new set is valid — which is the case that never needed atomicity.
- **A runtime dynamic catalog** — `fetchModels` plus `ModelsStore`, refreshed in the background. Rejected for this change: it makes the model list external mutable state needing cache, invalidation, and an offline path, and the product need is a one-shot discovery action whose result the user adopts into `settings.yaml`. That action belongs to the configuration surface and is deferred with it; `settings.yaml` stays the single source of truth for what a route serves.

## Consequences

Configuring a provider no longer depends on a pi-ai release. A gateway, a self-hosted server, or a model newer than the pinned catalog is a `settings.yaml` edit, and a stale context window can be corrected in place. The deprecated `/compat` import is gone, so pi-ai deleting it is no longer a breaking event. `defaultMaxTokens` now flows from configuration when a deployment states one, without inventing a cap from catalog metadata.

What it costs: `settings.yaml` grows for a declared route, because it must state its endpoint, protocol, and model ids. `api` applies to a whole route, so a mixed-protocol catalog route cannot host a model of the other protocol — splitting it across two route keys is the workaround. Nothing queries a provider's `/models`, so a model list is only as current as its last edit. Reported error shape shifts in one case: a route whose auth resolves to nothing now surfaces pi-ai's own diagnostic as an error `finish` chunk before any network call, where the previous adapter sent a keyless request and surfaced the provider's 401.

## Testing

`tests/catalog.spec.ts` covers the contract end to end against local mock servers: a hand-declared route streaming to its own endpoint with its own credential, its appearance in the configurable-provider directory, per-model overrides defaulting from the installed catalog, a model added to a catalog route, protocol repointing with and without an endpoint override, catalog-only metadata surviving an override, the keyless posture and its `Authorization`-header workaround, an OAuth-only catalog route authenticating with the key its profile names while a keyless one stays unconfigured, a repointed route keeping its catalog auth, and every resolution failure that names a route or model. `tests/catalog.spec.ts` also pins the snapshot and directory contracts: an in-flight request whose route set changes during its credential await still reaches the endpoint it resolved against, the next request picks up the new one, a colliding declared route leaves the directory whole, and a declared route's entry appears and leaves with its profile. `packages/llm/llm/tests/topology.spec.ts` covers `replace` — refusing a candidate another registration owns while keeping the current set, accepting a swap over its own entries, allowing an empty set, and failing after disposal. `tests/sdk-options.spec.ts` re-targets the SDK boundary from the removed `/compat` import to the protocol table's lazy api module, which also pins that a setup failure arrives as a terminal error chunk rather than a throw. The twin's [design-verification role](2026-06-13-twin-llm-adapters.md) is unchanged.
