key-cape/docs/tenant-claim-contract.md
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Document tenant claim ownership and prove registration binding
Answers the GLAS-WP-0015 tenant-alignment request. The JWT tenant is
tenant:coulomb for all four reviewed service registrations; the approval store
tenant and the policy tenant belong to other owners and KeyCape does no
normalization between them. No mapping is invented and no live registration
changes.

Adds regression tests proving the tenant claim is bound at registration and is
not influenced by request parameters, that distinct registrations never carry
each other's tenant, and that human tokens fall back to the platform tenant
rather than an empty claim.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01NV9oijZukGyGbRQGGKnK4P

Assistant: claude-code
Assistant-Model: opus
Assistant-Process: 713576@bnt-lap001
Assistant-Session: 384c511d-9bce-4cb8-a676-2aef6c0c8df6
2026-09-06 20:33:06 +02:00

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Markdown

# Tenant claim contract
Answers the tenant-alignment question in glas-harness message
`356f6977-d361-4e3b-83ab-b2c7f4759286` (GLAS-WP-0015). It states what KeyCape
owns and emits; it does not create a mapping between tenant vocabularies.
## What KeyCape emits
The `tenant` claim is bound at registration or directory-resolution time and is
never influenced by request parameters.
| Principal | Source of `tenant` | Value in the reviewed registrations |
| --- | --- | --- |
| Service (`client_credentials`) | The client's `tenant` field. Required by config validation — a `client_credentials` client without `serviceSubject` and `tenant` fails startup validation. | `tenant:coulomb` for all four clients in `config/service-clients.example.yaml`, including `secrets-engine-approval` and `approval-engine-operator`. |
| Human (`authorization_code`) | The directory user's tenant, falling back to the platform default when unset. | Directory value, else `tenant:coulomb`. |
`tenant`, `tenant_hint`, `audience` and `resource` request parameters cannot
change the claim. `tenant_hint` on `/authorize` reaches registration/enrollment
handoffs only; it is not a claim input.
## The three values in the request
- **JWT tenant** — `tenant:coulomb`. Owned by KeyCape, emitted verbatim from the
registration above. This is the only one of the three KeyCape owns.
- **Approval store tenant** — `platform`. Owned by approval-engine.
- **Policy tenant / CheckRequest tenant** — `tenant:platform`. Owned by flex-auth.
KeyCape performs **no** normalization, prefix-stripping or aliasing. A resource
server comparing `tenant` must use exact string comparison, so as things stand a
token issued to `secrets-engine-approval` (`tenant:coulomb`) does not match an
approval store tenant `platform` or a policy tenant `tenant:platform`.
## What is not decided here
Whether these three identify the same tenant across layers is not a KeyCape
decision, and spelling similarity is not a mapping. Two admissible resolutions
exist, both owned outside this repository:
1. The consuming owners accept `tenant:coulomb` as the JWT tenant and record the
layer mapping in their own contract; KeyCape changes nothing.
2. The owners decide the approval clients belong to a different tenant, in which
case KeyCape changes the `tenant` field on those two registrations only, under
an explicit decision reference, and re-issues.
KeyCape will not change the `tenant` value on a live registration without such a
reference. No unilateral change to live clients or policy subjects was made.
## Evidence
`src/internal/server/oidc/tenant_test.go`:
- `TestServiceTenantIsBoundToRegistrationAndIgnoresRequestParameters` — a request
supplying `tenant=tenant:platform` and `tenant_hint=platform` still yields the
registered `tenant`, signature-verified against `/jwks`.
- `TestServiceTenantsAreDistinctPerRegistration` — two registrations with
different tenants yield their own values and never each other's; this is the
wrong-tenant denial basis for an exact-comparison resource server.
- `TestHumanTenantClaimUsesDirectoryValueThenPlatformDefault` — human tokens carry
the directory tenant, defaulting to `tenant:coulomb` rather than an empty claim.
These are local issuance proofs. They are not live-rollout evidence; see
`docs/approval-engine-auth-contract.md` and KEY-WP-0013-T02 for the deployment
boundary. No token or secret values appear in this document or in test output.