[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. 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: grant_types_supported is optional authorization-server capability metadata.

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 · 2026-09-05T02:45:13Z

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coderabbitai · 2026-09-05T02:45:39Z

📝 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 require authorization-code support and use supported authorization 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.

Walkthrough

MCP OAuth now filters discovered grant types to authorization_code and refresh_token, builds native client metadata, validates registration behavior, and runs exhaustive integration checks in CI.

Changes

MCP OAuth integration

Layer / File(s)	Summary
OAuth metadata contracts and selection `src/services/mcp/oauthMetadata.ts`	Defines the 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 unsupported grant filtering, native metadata, missing authorization-code support, and registration retry behavior.
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.

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

Merge Risk: 🟡 Moderate · up to c5286

OAuth registration can still fail for servers that omit grant metadata but accept only authorization-code clients, because the client advertises refresh-token support. Update the omitted-metadata default and its integration assertion before merge.

Suggested reviewers: edelauna

🚥 Pre-merge checks | ✅ 6 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. 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 …	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (6 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly identifies the MCP OAuth registration failure caused by unsupported advertised grants and matches the primary change.
Description check	✅ Passed	The description explains the problem, implementation, impact, linked issue, and test coverage. It omits the repository template headings and checklist, but it provides the required information in subs…
Linked Issues check	✅ Passed	The changes satisfy issue `#1531` by allowlisting authorization_code and refresh_token, filtering JWT-bearer and unknown grants, preserving supported OAuth flows, and adding tests for filtering and succ…
Out of Scope Changes check	✅ Passed	The changes are focused on MCP OAuth registration. The shared metadata helpers, provider updates, tests, integration check, and CI step directly support the linked issue.
Regression Evidence	✅ Passed	PASS. The changed OAuth behavior has focused coverage. `McpOAuthClientProvider.spec.ts` checks native metadata, JWT-bearer and unknown-grant filtering, authorization-code absence, DCR success, and bot…
Trust And Persistence Invariants	✅ Passed	PASS: No changed path matches the explicit failure conditions. `selectMcpOAuthGrantTypes` intersects server-advertised values with the fixed `authorization_code` and `refresh_token` allowlist, so JWT-…

Full details: Docstring Coverage

Explanation

Docstring coverage is 0.00% which is insufficient. 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 unsupported.)

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src/services/mcp/McpOAuthClientProvider.ts

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src/services/mcp/oauthMetadata.ts

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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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📒 Files selected for processing (6)

.github/workflows/code-qa.yml
package.json
scripts/check-mcp-oauth-integration.ts
src/services/mcp/McpOAuthClientProvider.ts
src/services/mcp/__tests__/McpOAuthClientProvider.spec.ts
src/services/mcp/oauthMetadata.ts

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Check persistence and lifecycle invariants: awaited atomic writes, rollback or explicit partial-failure behavior, cross-window state consistency, stale listeners/watchers, cancellation, idempotency, and safe restart/resume without lost or d...