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fix(auth): send auth challenge without error when no token is present - #3779

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Jihaochang1 wants to merge 1 commit into
modelcontextprotocol:mainfrom
Jihaochang1:fix/3769-no-auth-header-error
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Jihaochang1 wants to merge 1 commit into
modelcontextprotocol:mainfrom
Jihaochang1:fix/3769-no-auth-header-error

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Summary

Per RFC 6750 §3.1, when a request lacks any authentication, the resource server SHOULD NOT include an error code. The current code returns error="invalid_token" for both missing and invalid tokens, preventing clients from distinguishing between the two cases.

Changes

  • Detects whether an Authorization header was present
  • For missing credentials: returns challenge with resource_metadata and scope (no error code)
  • For invalid credentials: keeps the existing invalid_token response

References

Fixes #3769

@github-actions github-actions Bot added the missing-issue-link Auto-closed: PR needs a linked issue assigned to its author (see CONTRIBUTING.md) label Oct 28, 2026
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This PR has been closed automatically. This repo only keeps pull requests open when they come from a maintainer, or from a contributor a maintainer has assigned to the linked issue, and you aren't currently assigned to #3769.

If a maintainer assigns you to #3769, this PR reopens on its own and there's nothing more you need to do here. Assignment is a maintainer call based on capacity; comments that only ask to be assigned don't factor in. What does help is engaging on the issue itself by confirming the repro, explaining why it matters for your use case, or describing the approach you'd take.

You're welcome to keep pushing commits here (just avoid force-pushing, since GitHub can't reopen a rewritten branch), but that on its own won't get the PR reviewed or the issue assigned, and realistically most auto-closed PRs stay closed. There's no need to open a new PR either way.

CONTRIBUTING.md has the full reasoning, but in short:

  • We're a small team with very little capacity to review community PRs right now.
  • Many recent PRs are AI-generated with little human review, and reviewing one carefully still costs a maintainer as much time as it ever did. A well-described issue is usually more useful to us than the code.

Maintainers: reopen, remove missing-issue-link, or add bypass-issue-check to override.

@github-actions github-actions Bot closed this Oct 28, 2026
Per RFC 6750 §3.1, when a request lacks any authentication, the
resource server SHOULD NOT include an error code. The current code
returns error="invalid_token" for both missing and invalid tokens,
which prevents clients from distinguishing between the two cases.

This change:
- Detects whether an Authorization header was present
- For missing credentials: returns challenge with resource_metadata
  and scope (no error code)
- For invalid credentials: keeps the existing invalid_token response

Fixes modelcontextprotocol#3769
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401 and error for a request with no authorization header (for a request with no token) - as per spec no error should be added

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