[rwzdk]

Treat { issues: [] } as a Standard Schema validation failure instead of returning { success: true, data: undefined }. The spec distinguishes results by the presence of issues, not its length: https://standardschema.dev/schema.

The branch is rebased onto the current main, so it is no longer behind the base branch.

Adds sync/async regressions, transformed/undefined success controls, and a client/server patch changeset. This is a straightforward bug fix under CONTRIBUTING.md's small-fix exception; no API or dependency changes.

Validation on Windows, Node 24.21.0, pnpm 10.26.1:

• The two new regressions fail on unchanged main and pass with the fix.
• Core-internal: 1,840 passed; client: 1,076 passed; server: 671 passed, 3 skipped; integration: 444 passed.
• Workspace build, typecheck and lint passed.
• The full workspace test command is not green locally: codemod's directory-symlink test fails with EPERM; two stdio shutdown-escalation cases (2025-11-25 and 2026-07-28) time out waiting for the SIGTERM marker on Windows.

AI disclosure: Codex generated the investigation, implementation, tests and this description, executed the listed checks, and performed a separate agent review. No production incident or human review is claimed.

[changeset-bot]

🦋 Changeset detected

Latest commit: 3f07d25

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

This PR includes changesets to release 6 packages

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

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commit: 3f07d25