modelcontextprotocol / modelcontextprotocol/servers

Please cut a new release of @modelcontextprotocol/server-sequential-thinking — coercion fix from #3533 not on npm

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Description

The latest npm release @modelcontextprotocol/server-sequential-thinking@2025.12.18 rejects valid tool calls from clients (e.g. Claude Code) that send nextThoughtNeeded, thoughtNumber, and totalThoughts as strings:

MCP error -32602: Input validation error
  nextThoughtNeeded: expected boolean, received string
  thoughtNumber: expected number, received string
  totalThoughts: expected number, received string

This was reported in #3428 and fixed by #3533 (merged 2026-03-15) which switches the schema to z.coerce.number() and a coercedBoolean helper. The fix is on main but has not been published — 2025.12.18 is still the latest tag on npm, so npx -y @modelcontextprotocol/server-sequential-thinking continues to pull the broken build.

Request: cut a new release (e.g. 2025.12.19 or 2026.3.x) so downstream users get the fix without having to pin to 2025.11.25 or build from source.

Repro: Call the sequentialthinking tool from Claude Code with nextThoughtNeeded: false, thoughtNumber: 1, totalThoughts: 1.

Workaround: Pin to @2025.11.25 in MCP client config.

Contributor guide

Open the contributing guide

First steps

  1. Read the whole issue, then the project's contributing guide.
  2. Comment on the issue to say you are picking it up — it saves two people doing the same work.
  3. Fork the repository and make your change on a branch.
  4. Open a pull request that references the issue number.

Research direction

Start with the @modelcontextprotocol/server-sequential-thinking package, its current 2025.12.18 npm release, and the fix from #3533 on main. Check the repository's release path and verify the sequentialthinking repro accepts string values after a new release is published to npm.

Written by the indexing model from the issue text.

Assessment

Tech stack
typescript
Domain
release
Issue type
Bug
Difficulty
3/5
Estimated time
1-2 days
Activity status
Active
Clarity
Mostly clear
Newbie friendliness
42/100

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