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[Schema] fix: allow URIs without double slash in Resource and ResourceTemplate (RFC 3986)#297

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chr-hertel merged 2 commits intomodelcontextprotocol:mainfrom
blackwell-systems:fix/uri-pattern-rfc3986
May 8, 2026
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[Schema] fix: allow URIs without double slash in Resource and ResourceTemplate (RFC 3986)#297
chr-hertel merged 2 commits intomodelcontextprotocol:mainfrom
blackwell-systems:fix/uri-pattern-rfc3986

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@blackwell-systems blackwell-systems commented May 2, 2026

Summary

The URI regex in Resource and ResourceTemplate requires :// after the scheme, rejecting valid URIs where the hier-part does not start with //. Per RFC 3986, the authority component (and its // prefix) is optional.

What breaks

// All of these throw InvalidArgumentException:
new Resource(uri: 'urn:isbn:0451450523', name: 'book');
new Resource(uri: 'mailto:user@example.com', name: 'contact');
new Resource(uri: 'data:text/plain;base64,SGVsbG8=', name: 'data');
new Resource(uri: 'config:myapp/settings', name: 'settings');

new ResourceTemplate(uriTemplate: 'config:{key}', name: 'config');

The MCP spec allows custom URI schemes following RFC 3986.

Fix

Changed :// to : in both regex patterns:

- '/^[a-zA-Z][a-zA-Z0-9+.-]*:\/\/[^\s]*$/'
+ '/^[a-zA-Z][a-zA-Z0-9+.-]*:[^\s]*$/'

- '/^[a-zA-Z][a-zA-Z0-9+.-]*:\/\/.*{[^{}]+}.*/'
+ '/^[a-zA-Z][a-zA-Z0-9+.-]*:.*{[^{}]+}.*/'

URIs with :// (like file://path) continue to match.

Test plan

  • Added data-provider tests for urn:, mailto:, data:, and custom schemes without //
  • Added data-provider tests for resource templates without //
  • All 20 tests pass (phpunit tests/Unit/Schema/)
  • Existing tests unchanged

Fixes #293

@blackwell-systems
fix: allow URIs without double slash in Resource and ResourceTemplate…
97d98d4 
… (RFC 3986)

The URI regex required "://" after the scheme, rejecting valid URIs
like urn:isbn:123, mailto:user@example.com, config:key, and data:
URIs. RFC 3986 only requires ":" after the scheme; the "//" is part
of the authority component which is optional.

Changed both Resource.URI_PATTERN and ResourceTemplate.URI_TEMPLATE_PATTERN
to require ":" instead of "://".

Adds data-provider tests for URIs without double slash in both classes.

Fixes modelcontextprotocol#293
chr-hertel
chr-hertel reviewed May 8, 2026
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Comment thread tests/Unit/Schema/ResourceTemplateTest.php Outdated
chr-hertel
chr-hertel reviewed May 8, 2026
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Comment thread tests/Unit/Schema/ResourceTest.php Outdated
@chr-hertel chr-hertel changed the title fix: allow URIs without double slash in Resource and ResourceTemplate (RFC 3986) [Schema] fix: allow URIs without double slash in Resource and ResourceTemplate (RFC 3986) May 8, 2026
@chr-hertel chr-hertel added Schema Issues & PRs related to the Schema component P2 Moderate issues affecting some users, edge cases, potentially valuable feature bug Something isn't working labels May 8, 2026
chr-hertel
chr-hertel approved these changes May 8, 2026
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Thanks @blackwell-systems - briefly renamed some test methods while merging, JFYI.

@chr-hertel chr-hertel merged commit 7974727 into modelcontextprotocol:main May 8, 2026
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@chr-hertel chr-hertel chr-hertel approved these changes

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[Schema] URI Regex doesn't seem to be correct

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