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Claude Desktop update breaks local MCP servers over JSON Schema dialect issues

By PulseAugur Editorial · [1 sources] ·

An update to Claude Desktop's bundled Model Context Protocol (MCP) client has caused issues for users running local MCP servers. The updated client, version 2.0.0-beta.4, defaults to stricter JSON Schema validation (2020-12) and rejects schemas declared with older dialects like draft-07, which were previously generated by tools like zod-to-json-schema. This has led to servers failing to register, even though the MCP specification allows for older dialects. A fix has been merged upstream for the MCP TypeScript SDK, but Claude Desktop has not yet adopted the updated client, leaving users to implement workarounds such as a stdio proxy to modify schema declarations before they are processed. AI

IMPACT A bug in Claude Desktop's bundled client has caused compatibility issues for local MCP servers, requiring users to implement workarounds.

RANK_REASON The cluster describes a bug in a specific software component (Claude Desktop's bundled MCP client) and a workaround, rather than a new release or significant industry event.

Read on dev.to — MCP tag →

AI-generated summary · Google Gemini · from 1 sources. How we write summaries →

Claude Desktop update breaks local MCP servers over JSON Schema dialect issues

How we ranked this

Signal score
13 / 100
Composite score across the factors below. Higher = stronger signal that this story matters right now.
Newsworthiness bucket
Tool
The cluster describes a bug in a specific software component (Claude Desktop's bundled MCP client) and a workaround, rather than a new release or significant industry event.
Source corroboration
Single-source cluster
Only one publisher covered this so far. Single-source stories can still rank when the publisher is high-authority, but they lack cross-source corroboration.
Topics
product, infra
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High
Clearly on-topic for AI-industry coverage.
Story freshness
Breaking (< 6h)
Fresh story with cross-source coverage still developing. Ranking may shift as more sources report.

Full methodology in our editorial standards.

COVERAGE [1]

  1. dev.to — MCP tag TIER_1 Svenska(SV) · MilkyWay008 ·

    Claude Desktop update broke my MCP server: JSON Schema draft-07 vs 2020-12

    <p>If your Claude Desktop app updated itself overnight and your local MCP servers stopped registering the next morning, this is probably why. It's not your config, and it's not your server code. A newer bundled MCP client started rejecting your tool schemas over a version string …

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