fix(core): exclude fragment delimiter from URI template matches

[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

[pkg-pr-new]

Open in StackBlitz

@modelcontextprotocol/client

npm i https://pkg.pr.new/@modelcontextprotocol/client@3010

@modelcontextprotocol/codemod

npm i https://pkg.pr.new/@modelcontextprotocol/codemod@3010

@modelcontextprotocol/core

npm i https://pkg.pr.new/@modelcontextprotocol/core@3010

@modelcontextprotocol/server

npm i https://pkg.pr.new/@modelcontextprotocol/server@3010

@modelcontextprotocol/server-legacy

npm i https://pkg.pr.new/@modelcontextprotocol/server-legacy@3010

@modelcontextprotocol/express

npm i https://pkg.pr.new/@modelcontextprotocol/express@3010

@modelcontextprotocol/fastify

npm i https://pkg.pr.new/@modelcontextprotocol/fastify@3010

@modelcontextprotocol/hono

npm i https://pkg.pr.new/@modelcontextprotocol/hono@3010

@modelcontextprotocol/node

npm i https://pkg.pr.new/@modelcontextprotocol/node@3010

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.