[Fix] MCP OAuth registration fails for servers advertising unsupported grants by zoomote[bot] · Pull Request #1532 · Zoo-Code-Org/Zoo-Code

zoomote · 2026-09-05T01:24:43Z

Created by Roomote. Follow up by mentioning @roomote, in the web UI, or in Discord.

What changed

Dynamic OAuth client registration now limits server-advertised grant types to the flows Zoo Code implements: authorization_code and refresh_token. When grant_types_supported is omitted, Zoo Code follows RFC 8414 by selecting only the implemented authorization_code default rather than assuming refresh support. The runtime and token requests share one metadata policy, registration rejects servers that do not support authorization code, and native desktop registration declares application_type: "native".

A bounded pnpm mcp:integration-check command validates all 16 combinations of the two supported grants, JWT bearer, and an unknown extension. Code QA runs it in the compile job beside lifecycle:model-check.

Why this change was made

Some authorization servers advertise grant types that Zoo Code does not implement and that their dynamic registration endpoints reject. Sending only the grants Zoo Code actually uses prevents those metadata values from breaking MCP OAuth registration and keeps registered metadata aligned with the token endpoint.

The integration rules are grounded in:

RFC 7591 section 2: grant_types describes grants the client can use, and token requests must use matching grant_type values.
RFC 7591 section 2.1: authorization-code grants correspond to the code response type.
MCP client registration: DCR clients must specify application_type, with desktop/localhost clients using native.
MCP refresh-token guidance: clients that use refresh tokens should include refresh_token in registration metadata.
RFC 8414 section 2: omitted grant_types_supported defaults to authorization_code and implicit; Zoo Code selects the authorization-code grant it implements.

Impact

MCP OAuth registration succeeds against servers such as PostHog that advertise urn:ietf:params:oauth:grant-type:jwt-bearer but reject it during dynamic client registration. Existing authorization code and refresh token behavior is preserved when those grants are supported, and CI now prevents the registration metadata from drifting away from the flows Zoo Code actually executes.

Fixes #1531

github-actions · 2026-09-05T01:26:40Z

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codecov · 2026-09-05T01:29:11Z

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edelauna · 2026-09-05T02:45:05Z

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coderabbitai · 2026-09-05T02:45:39Z

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🔇 Additional comments (5)

src/services/mcp/oauthMetadata.ts (1)

3-38: LGTM!

src/services/mcp/__tests__/McpOAuthClientProvider.spec.ts (1)

193-198: LGTM!

Also applies to: 200-212, 228-281, 881-920

scripts/check-mcp-oauth-integration.ts (1)

1-77: LGTM!

package.json (1)

19-19: LGTM!

.github/workflows/code-qa.yml (1)

24-24: LGTM!

Also applies to: 40-40, 66-66, 76-76, 86-86, 93-96, 104-104, 118-118, 141-141, 146-146, 161-161, 177-177, 189-189, 197-197, 205-205, 213-213

📝 Summary

Summary by CodeRabbit

Improvements
- Improved MCP OAuth compatibility by advertising only supported grant types.
- Added native application metadata for MCP OAuth client registration.
- MCP connections now use supported authorization-code and refresh-token flows.
- Dynamic client registration can retry when a server rejects unsupported grant types.
Bug Fixes
- Prevented unsupported or unknown OAuth grant types from being propagated during MCP authentication.
- MCP authentication now reports an error when authorization-code support is unavailable.

Walkthrough

MCP OAuth now filters discovered grant types to authorization_code and refresh_token, builds native client metadata, validates unsupported-grant handling, and runs integration checks in CI.

Changes

MCP OAuth integration

Layer / File(s)	Summary
OAuth metadata contracts and selection `src/services/mcp/oauthMetadata.ts`	Defines supported grant types, filters discovered grants, constructs native client metadata, and rejects metadata without `authorization_code`.
Provider metadata and registration flow `src/services/mcp/McpOAuthClientProvider.ts`, `src/services/mcp/__tests__/McpOAuthClientProvider.spec.ts`	Uses shared grant constants and metadata helpers. Tests cover defaults, unsupported grant filtering, native metadata, and missing authorization-code support.
Integration validation and CI wiring `scripts/check-mcp-oauth-integration.ts`, `package.json`, `.github/workflows/code-qa.yml`	Adds exhaustive integration checks and runs them in the compile workflow.

Priority: ➖ Normal

Estimated code review effort: 3 (Moderate) | ~20 minutes

Severity of issue fixed: Medium

Merge Risk: ⚪ Minimal · up to 02db0

MCP OAuth registration now sends only supported authorization-code and refresh-token grants, avoiding registration failures from unsupported server-advertised grants while preserving implemented token flows. The covered behavior is ready to merge.

Sequence Diagram(s)

sequenceDiagram
  participant McpOAuthClientProvider
  participant oauthMetadata
  participant RegistrationEndpoint
  McpOAuthClientProvider->>oauthMetadata: Select supported grant types
  oauthMetadata-->>McpOAuthClientProvider: Return filtered grants
  McpOAuthClientProvider->>oauthMetadata: Build native client metadata
  oauthMetadata-->>McpOAuthClientProvider: Return metadata
  McpOAuthClientProvider->>RegistrationEndpoint: Submit registration metadata

Suggested reviewers: edelauna

🚥 Pre-merge checks | ✅ 7

✅ Passed checks (7 passed)

Check name	Status	Explanation
Linked Issues check	✅ Passed	The changes satisfy issue `#1531` by allowlisting authorization_code and refresh_token, filtering jwt-bearer and unknown grants, testing successful registration against rejected unsupported grants, and …
Out of Scope Changes check	✅ Passed	All changes support the linked OAuth registration fix. The shared metadata helpers, provider updates, tests, integration check, and CI workflow change are directly related to the stated objectives.
Docstring Coverage	✅ Passed	Docstring coverage is 100.00% which is sufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 2 functions across 4 files. (2 skipped: 2 …
Regression Evidence	✅ Passed	Focused coverage exists for each changed OAuth behavior. `McpOAuthClientProvider.spec.ts` checks exact default grants, omitted metadata, JWT and unknown-grant filtering, native application metadata, r…
Trust And Persistence Invariants	✅ Passed	PASS. The changed OAuth path filters discovered grant metadata through the fixed `MCP_OAUTH_GRANT_TYPES` allowlist and emits a new array, so JWT-bearer and unknown grants cannot reach registration. Th…
Title check	✅ Passed	The title clearly identifies the main change: fixing MCP OAuth registration failures caused by unsupported advertised grants.
Description check	✅ Passed	The description links issue `#1531` and clearly explains the implementation, rationale, impact, standards basis, and validation command. It omits the template's explicit Test Procedure and Pre-Submissio…

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Commit unit tests in branch fix/oauth-grant-filter-2iwple0khlo0y

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Actionable comments posted: 1

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Inline comments:
In `@src/services/mcp/oauthMetadata.ts`:
- Line 14: Update the default grant set in the supported grant metadata
construction to use AUTHORIZATION_CODE_GRANT_TYPE when supportedGrantTypes is
omitted, rather than MCP_OAUTH_GRANT_TYPES or refresh_token. Adjust the
integration assertion in the MCP OAuth check to expect the authorization-code
default while preserving explicitly supplied grant types.

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src/services/mcp/oauthMetadata.ts
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zoomote · 2026-09-07T18:27:51Z

Rebased onto current main and addressed all actionable CodeRabbit feedback in 02db02861: omitted grant metadata now follows RFC 8414 without assuming refresh support, the integration/provider regressions cover it, and exported metadata helpers have API documentation. Focused tests, MCP integration validation, model checks, formatting, typecheck, lint, and the full test suite pass. Visual proof timed out; no retry was attempted, and this OAuth/CI change has no rendered UI surface.

edelauna · 2026-09-09T23:18:27Z

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coderabbitai · 2026-09-09T23:18:33Z

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coderabbitai Bot requested changes Sep 5, 2026

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Comment thread src/services/mcp/oauthMetadata.ts Outdated

zoomote Bot force-pushed the fix/oauth-grant-filter-2iwple0khlo0y branch from c5286da to f1ecbbc Compare September 7, 2026 18:35

roomote added 3 commits September 7, 2026 18:36

fix(oauth): filter dynamic registration grant types

be169fa

test(mcp): validate OAuth registration integration

1694bc6

fix(oauth): honor default server grant support

02db028

zoomote Bot force-pushed the fix/oauth-grant-filter-2iwple0khlo0y branch from f1ecbbc to 02db028 Compare September 7, 2026 18:40

github-actions Bot removed the has-conflicts PR has merge conflicts with the base branch label Sep 7, 2026

coderabbitai Bot approved these changes Sep 9, 2026

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edelauna marked this pull request as ready for review September 10, 2026 02:45

edelauna requested review from JamesRobert20, edelauna, hannesrudolph, navedmerchant and taltas as code owners September 10, 2026 02:45

edelauna approved these changes Sep 10, 2026

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edelauna enabled auto-merge September 10, 2026 02:47

edelauna added this pull request to the merge queue Sep 10, 2026

Merged via the queue into main with commit e5248e5 Sep 10, 2026
35 of 36 checks passed

edelauna deleted the fix/oauth-grant-filter-2iwple0khlo0y branch September 10, 2026 03:13

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[Fix] MCP OAuth registration fails for servers advertising unsupported grants - #1532

[Fix] MCP OAuth registration fails for servers advertising unsupported grants#1532
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