fix: use getLiteralValue for Zod v3 method literal extraction#1876
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JosephDoUrden wants to merge 1 commit intomodelcontextprotocol:v1.xfrom
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fix: use getLiteralValue for Zod v3 method literal extraction#1876JosephDoUrden wants to merge 1 commit intomodelcontextprotocol:v1.xfrom
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…andler Replace inline Zod v3/v4 literal extraction in Server.setRequestHandler and Client.setRequestHandler with the existing getLiteralValue() helper from zod-compat.ts, which already handles the _def.values[0] fallback for late Zod v3 releases (e.g., zod@3.25.1) where the literal value is stored under _def.values instead of _def.value. This fixes "Schema method literal must be a string" errors when constructing McpServer with zod@3.25.x. Fixes modelcontextprotocol#1380
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Summary
Fix
"Schema method literal must be a string"error when constructingMcpServerwith late Zod v3 releases (e.g.,zod@3.25.1) where the literal value is stored under_def.values[0]instead of_def.value.Closes #1380
Root cause
Server.setRequestHandlerandClient.setRequestHandlerhad inline Zod literal extraction that only checked_def.valueand.value. Inzod@3.25.x, the literal is stored under_def.values[0]instead. The existinggetLiteralValue()helper inzod-compat.tsalready handles this fallback correctly, but it wasn't being used in these two locations.Changes
src/server/index.ts: Replace inline v3/v4 literal extraction withgetLiteralValue()callsrc/client/index.ts: Same replacementThis is a v1.x backport as discussed in #1380 — the issue resolves itself in v2 with the Zod v3 removal.
Test plan
npm test)npm run build)AI Disclosure
AI assistance (Claude) was used for issue research and codebase exploration. The implementation was written and reviewed by the author.