* feat(relay): ambient token endpoint mode for gateway.idp.token_url
When gateway.idp.token_url is configured WITHOUT client_id/client_secret,
treat the URL as a metadata-server-style ambient credential endpoint:
plain GET, response body is the token (raw JWT or {"access_token": ...}
JSON envelope). Covers workload-identity proxies such as Domino's
$DOMINO_API_PROXY/access-token, which mint short-lived user-scoped OIDC
tokens with no client registration.
Previously this configuration was a hard error (client_id/client_secret
missing), so no working deployment changes behaviour: creds present keeps
the OAuth2 client_credentials POST, no token_url keeps Nous Portal. The
misconfig error now self-diagnoses (names the ambient fallback and how to
select the client_credentials grant instead).
* fix(relay): reject short plain-text bodies in ambient token shape gate
Review finding: the shape gate accepted any base64url-alphabet word, so an
IdP answering the ambient GET with a terse error body ('unauthorized',
'error', 'null') had that word returned as a bearer token instead of the
fail-closed misconfiguration error. Tighten the gate to JWT-like dotted
tokens (3+ segments) or long opaque tokens (>= 32 chars); short bare words
now raise the self-diagnosing ambient error.
* fix(relay): partial IdP client credentials keep the loud error, never select ambient GET
The ambient-endpoint dispatch used 'not client_id or not client_secret',
so configuring exactly one credential (a mistyped client_credentials
setup) silently issued a GET at the IdP token endpoint and then raised
'no client_id/client_secret configured' — factually wrong for that
operator, and a stray request the old hard error never made.
Ambient mode now requires NEITHER credential; a partial pair raises
immediately, names the missing key, and issues no HTTP request (tests
assert urlopen is never called). Docstring and relay.md now say
'neither' instead of 'without'.
* fix(relay): ambient JSON envelope requires a string access_token, no coercion
Review finding (P2): the JSON-envelope branch accepted any truthy
access_token via str() coercion — a number became '12345…', a boolean
became 'True', an object became its Python repr — bypassing the fail-
closed contract and deferring the failure to the connector, where it
hides the real endpoint problem.
The envelope value must now be a non-empty string, the same contract the
client_credentials path enforces on its token response. Deliberately NO
shape gate on envelope values: an envelope is an intentional token
response (mode-1 symmetry), and opaque tokens may use the standard-base64
alphabet the raw-body gate rejects. Mutation check: reverting the branch
to str() coercion sends the 3 coercion tests red (3 failed, 15 passed).
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Co-authored-by: Ben Barclay <ben@nousresearch.com>
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