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openspec/specs/api-auth/spec.md

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+<!-- markdownlint-disable MD024 -->
+
+# Capability Spec: api-auth
+
+**Package**: `@suaveplan/api-auth`
+**Status**: SHIPPED (0.1.0)
+
+> Every requirement carries a `**Verified by:**` line.
+
+## Requirements
+
+### Requirement: SessionResolver contract
+
+The package SHALL export `SessionResolver` interface: `resolve(req: Request): Promise<Principal | null>`, `dispose(): Promise<void>`. A resolver returning `null` means "I don't recognise this request" — NOT "auth failed." Auth failure (401) is the host's decision based on chain outcome + route's `publicRoutes` membership.
+
+#### Scenario: every method present
+
+- **WHEN** `expectTypeOf<SessionResolver>()` is checked
+- **THEN** `resolve` and `dispose` are declared with the documented signatures
+
+**Verified by:** `src/resolver/resolver.spec-conformance.test.ts::"SessionResolver declares resolve and dispose"`
+
+---
+
+### Requirement: `import z from "zod"` everywhere
+
+Every Zod import MUST use the default form.
+
+#### Scenario: no named import of z
+
+- **WHEN** the test greps `import z` from `"zod"`
+- **THEN** zero matches
+
+**Verified by:** `tests/zod-import-form.test.ts::"every src file uses default-import z"`
+
+---
+
+### Requirement: Resolver chain — first-match-wins
+
+The package SHALL export `SessionResolverChain(resolvers: readonly SessionResolver[]).resolve(req): Promise<Principal | null>` running each resolver in order; the first non-null result wins; if all return null, the chain returns null. An empty chain MUST throw `AUTH.CHAIN_EMPTY` at construction. By default, a resolver throwing MUST surface `AUTH.RESOLVER_THREW` AND short-circuit the chain (fail-closed). An opt-in `continueOnThrow: true` flag lets the chain try the next resolver; this is documented as escape-hatch only.
+
+#### Scenario: first non-null wins
+
+- **WHEN** chain `[null, principalA, principalB]` is run
+- **THEN** the chain returns `principalA` AND resolver B is NOT called
+
+#### Scenario: all null returns null
+
+- **WHEN** every resolver returns null
+- **THEN** the chain returns null
+
+#### Scenario: throw is fail-closed by default
+
+- **WHEN** resolver A throws AND `continueOnThrow` is false (default)
+- **THEN** the chain throws `AUTH.RESOLVER_THREW` AND resolver B is NOT called
+
+#### Scenario: empty chain rejected at construction
+
+- **WHEN** `new SessionResolverChain([])` is called
+- **THEN** it throws `AUTH.CHAIN_EMPTY`
+
+**Verified by:** `src/chain/chain.test.ts::"first non-null wins, later resolvers skipped"` AND `src/chain/chain.test.ts::"all null returns null"` AND `src/chain/chain.test.ts::"throw is fail-closed by default"` AND `src/chain/chain.test.ts::"empty chain rejected at construction"`
+
+---
+
+### Requirement: SecuritySchemeContribution
+
+The package SHALL export `SecuritySchemeContribution` with `{ name: string, scheme: OpenApiSecurityScheme }`. Every concrete `SessionResolver` MUST contribute exactly one scheme so `api-openapi` can emit the right `securitySchemes` block. An `AuthAdapter` whose `securityScheme` is absent at registration MUST surface `AUTH.SECURITY_SCHEME_MISSING`.
+
+#### Scenario: missing scheme rejected
+
+- **WHEN** an `AuthAdapter` without `securityScheme` is registered
+- **THEN** registration throws `AUTH.SECURITY_SCHEME_MISSING`
+
+**Verified by:** `src/security-scheme/security-scheme.test.ts::"registration rejects adapter without securityScheme"`
+
+---
+
+### Requirement: CSRF default policy
+
+The package SHALL export `CsrfPolicy.requiresCsrf(scheme: OpenApiSecurityScheme): boolean`. Cookie-based schemes (`type: "apiKey"` AND `in: "cookie"`) default ON; JWT/Bearer schemes (`type: "http"` AND `scheme: "bearer"`) default OFF. Per-route `csrf: false` opt-out is honoured by the host (this package exposes the default; the host applies the override).
+
+#### Scenario: cookie scheme defaults to CSRF ON
+
+- **WHEN** `requiresCsrf({ type: "apiKey", in: "cookie", ... })` is called
+- **THEN** the result is `true`
+
+#### Scenario: bearer scheme defaults to CSRF OFF
+
+- **WHEN** `requiresCsrf({ type: "http", scheme: "bearer" })` is called
+- **THEN** the result is `false`
+
+**Verified by:** `src/csrf-policy/csrf-policy.test.ts::"cookie schemes default to CSRF ON"` AND `src/csrf-policy/csrf-policy.test.ts::"bearer schemes default to CSRF OFF"`
+
+---
+
+### Requirement: CapabilityId augmentation contributes "auth.session"
+
+The package SHALL augment the `CapabilityId` union to include `"auth.session"`.
+
+#### Scenario: auth.session assignable to CapabilityId
+
+- **WHEN** `expectTypeOf<"auth.session">().toMatchTypeOf<CapabilityId>()` is checked
+- **THEN** the assertion passes
+
+**Verified by:** `src/capability-id/capability-id.spec-conformance.test.ts::"auth.session is a valid CapabilityId after augmentation"`
+
+---
+
+### Requirement: Error codes registry frozen
+
+The package SHALL export `AUTH_CODES` containing exactly: `RESOLVER_THREW`, `CHAIN_EMPTY`, `PRINCIPAL_INVALID_SHAPE`, `SECURITY_SCHEME_MISSING`.
+
+#### Scenario: every code reachable
+
+- **WHEN** the test enumerates `AUTH_CODES`
+- **THEN** every code has a production throw site
+
+**Verified by:** `src/error-codes/error-codes.spec-conformance.test.ts::"every AUTH_CODES entry thrown by production path"`
+
+---
+
+### Requirement: Conformance harness for resolvers
+
+The package SHALL export `runAuthSessionConformance({ factory, label })`. Every concrete resolver in Stages 4/6/8 MUST pass it.
+
+#### Scenario: harness covers resolve null, resolve principal, dispose
+
+- **WHEN** the harness is run against a stub resolver
+- **THEN** test categories exist for each documented behavior
+
+**Verified by:** `src/testing/conformance.test.ts::"harness covers resolve null, resolve principal, dispose lifecycle"`