fix(everything): allow re-registration of session resources #3252
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When a tool like `gzip-file-as-resource` is called multiple times with the same output name (especially the default `README.md.gz`), the server would throw "Resource already registered" because the SDK doesn't allow registering duplicate URIs. This fix: - Tracks registered resources by URI in a module-level Map - Before registering a new resource, checks if the URI already exists - If it does, removes the old resource using the SDK's `remove()` method - Then registers the new resource with fresh content This allows tools to be called repeatedly with the same parameters without errors, which is important for LLM agents that may retry tool calls. Found using Bellwether (https://bellwether.sh), an MCP server validation tool. Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
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Summary
gzip-file-as-resourcemultiple times with the same output nameProblem
When a tool that creates session resources (like
gzip-file-as-resource) is called multiple times with the same output name, the server throws:This is particularly problematic because:
gzip-file-as-resourcetool has a default name ofREADME.md.gzSolution
The fix tracks registered session resources by URI in a Map, and before registering a new resource, it checks if one already exists with the same URI. If so, it uses the SDK's
remove()method to unregister the old resource first, then registers the new one.Test plan
gzip-file-as-resource10 times with default parameters - all succeedHow this was found
This bug was discovered using Bellwether, an open-source MCP server validation and documentation tool. Bellwether runs automated schema validation and behavioral testing against MCP servers, which caught this regression when repeatedly testing the
gzip-file-as-resourcetool.🤖 Generated with Claude Code