[sravan-v]

Problem

On current main (43c45f4), UriTemplate.match() treats fragment expressions like reserved expansions. This includes the fragment delimiter in the captured variable and accepts a value without the delimiter.

const template = new UriTemplate('file:///doc{#section}');
template.match(template.expand({ section: 'intro' }));
// Before: { section: '#intro' }
// After:  { section: 'intro' }

template.match('file:///docintro');
// Before: { section: 'intro' }
// After: null

Resource template routing passes these captured variables to resource handlers, so a handler receives the wrong section identifier.

Change

Give the fragment operator its own pattern, with # outside the capture group. Allow an empty fragment value, matching the existing expansion of an empty string to #. Keep reserved expansion matching unchanged.

Includes five test cases and a patch changeset. This is a small bug fix under the contribution guide's straightforward-fix exception.

Validation

• Four regression checks fail against unchanged main and pass with the fix.
• Core-internal suite: 71 files, 1,530 tests passed.
• Core-internal type checking, ESLint and Prettier passed.
• git diff --check passed.
• Repository snippet sync passed via node --import tsx scripts/sync-snippets.ts --check; the normal tsx CLI launcher cannot open its IPC pipe in this environment.
• Repository-wide tests and package lint are still running; results will be added here.

Fragment expansion behavior is documented in RFC 6570 §3.2.4. This change only fixes the matching of the delimiter; it does not change expansion or general decoding behavior.

AI-assisted implementation and test execution.

[changeset-bot]

🦋 Changeset detected

Latest commit: ac4d4df

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 6 packages

Name	Type
@modelcontextprotocol/core	Patch
@modelcontextprotocol/client	Patch
@modelcontextprotocol/core-internal	Patch
@modelcontextprotocol/server-legacy	Patch
@modelcontextprotocol/server	Patch
@modelcontextprotocol/codemod	Patch

Not sure what this means? Click here to learn what changesets are.

Click here if you're a maintainer who wants to add another changeset to this PR

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commit: ac4d4df

[0xamlab]

Confirmed the bug and the fix. On main, the four new fragment-expansion tests fail (4 failed | 39 passed in uriTemplate.test.ts) because the old regex at uriTemplate.ts:233 captured the # delimiter inside the variable group. With this branch, the same file runs 43 passed. The change splitting + and # handling so # uses #(.*) at uriTemplate.ts:238 keeps the delimiter out of the captured value, including empty fragments. Looks good to me.

[sravan-v]

Hi maintainers, could someone take a look at this PR when you have a chance? It fixes URI template matching so the # delimiter is excluded from the captured fragment value. The CI workflows passed, and an independent check confirmed the regression tests fail on main and pass with this change. Happy to address any feedback. Thanks!