fix: add runtime reranking model support

[sanmaxdev]

Summary

• add a runtime rerankingModel() factory to createOpenRouter()
• implement OpenRouterRerankingModel for AI SDK v3 reranking calls
• map OpenRouter /rerank responses into AI SDK ranking results
• add unit coverage for provider exposure and rerank request/response mapping

Closes #500

Testing

• pnpm typecheck
• pnpm vitest --config vitest.node.config.ts --run src/reranking/index.test.ts
• pnpm stylecheck
• pnpm build

[perry-the-pr-reviewer]

Perry's Review

Adds runtime support for rerankingModel() on the OpenRouter provider — a new RerankingModelV3 implementation, its response schema, settings type, provider wiring, and unit tests.

Verdict: 💬 Comments / questions

Details

Risk: 🟡 Medium

CI: all passing ✅ (verified locally: tsc --noEmit clean, 430/430 vitest pass incl. 3 new reranking tests, biome clean)

Findings (see inline comments):

• 🟡 src/reranking/index.ts:90 — provider metadata hardcoded to empty string; sibling embedding model reads it from the response
• 🟡 .changeset/reranking-runtime-provider.md:2 — patch bump for a new public API; repo precedent (#479 videoModel) used minor

Blast radius: purely additive. New src/reranking/ module + one provider wiring line + one barrel re-export. No existing request path, auth flow, or billing logic touched. Implementation mirrors the embedding/image/video siblings 1:1 (config shape, postJsonToApi call, metadata parse, warnings: []). Verified RerankingModelV3 and ProviderV3.rerankingModel exist in @ai-sdk/provider 3.0.8 and the doRerank return shape matches the interface.

Security: no concerns — no new auth/credential handling; reuses the shared getHeaders + extraBody passthrough.

Test coverage: good — covers provider method exposure, instance creation, and a full doRerank round-trip asserting URL, request body mapping (top_n, documents), ranking transform, and cost metadata.

Unresolved threads: none

Review: tier=medium · model=claude-opus-latest · score=5.6

[perry-the-pr-reviewer]

[suggestion] provider: '' hardcodes the provider name to empty — the sibling embedding model reads it from the response instead.

Suggested change

	provider: '',
	provider: responseValue.provider ?? '',

Details

Why: Every other model in this provider surfaces the upstream provider slug in providerMetadata.openrouter.provider (e.g. src/embedding/index.ts:95 does provider: responseValue.provider ?? ''). Here it is pinned to '', so callers can never tell which upstream provider (cohere, jina, etc.) actually served the rerank — useful signal that the rest of the SDK exposes consistently.

The rerank response schema (src/reranking/schemas.ts) uses .passthrough(), so a provider field returned by the API is already preserved on responseValue at runtime; the only missing piece is surfacing it. If the API does not return provider on /rerank, the ?? '' fallback keeps current behaviour, so the change is safe either way. Optionally add provider: z.string().optional() to the schema to make the field explicit.

Reviewed at bd948de

[perry-the-pr-reviewer]

[suggestion] Changeset is marked patch — a new public API method is conventionally a minor bump.

Suggested change

	"@openrouter/ai-sdk-provider": patch
	"@openrouter/ai-sdk-provider": minor

Details

Why: This PR adds a brand-new public surface — provider.rerankingModel() and the exported OpenRouterRerankingModel / OpenRouterRerankingSettings types. Per semver, new backwards-compatible API additions are minor, not patch. The most recent comparable change in this repo — #479, which added provider.videoModel() — shipped as a Minor changeset (see CHANGELOG.md). Marking this patch means the new method lands in a patch release, which under-signals the feature to consumers pinning on ~ ranges.

Non-blocking: if the maintainers intentionally batch feature additions into patch releases for this package, disregard.

Reviewed at bd948de