fix: use unprefixed message for JSON-RPC wire serialization (-32042)#1578
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evalstate wants to merge 2 commits intomodelcontextprotocol:mainfrom
Open
fix: use unprefixed message for JSON-RPC wire serialization (-32042)#1578evalstate wants to merge 2 commits intomodelcontextprotocol:mainfrom
evalstate wants to merge 2 commits intomodelcontextprotocol:mainfrom
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ProtocolError constructor sets Error.message to 'MCP error {code}: {message}'
for developer DX, but protocol.ts was using this prefixed string as the
JSON-RPC error.message on the wire. This caused:
1. Non-spec-conformant wire messages (spec examples show clean messages)
2. Double-prefixed messages on client reconstruction via ProtocolError.fromError()
('MCP error -32042: MCP error -32042: ...')
Fix: store the original unprefixed message as ProtocolError.rpcMessage and
use it in the protocol serialization path. Error.message retains the prefix
for developer-facing console/stack output.
Adds integration test validating exact wire format for -32042
URLElicitationRequiredError including:
- Clean (unprefixed) error.message on the wire
- Correct error.data.elicitations structure
- Single-prefix on client-side reconstructed Error.message
|
@modelcontextprotocol/client
@modelcontextprotocol/server
@modelcontextprotocol/express
@modelcontextprotocol/hono
@modelcontextprotocol/node
commit: |
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This fix allows the URL Elicitation details to be handled by the Client SDK in the case of a
-32042style error.Adds integration test validating exact wire format for -32042 URLElicitationRequiredError including:
Motivation and Context
URL Elicitations via the -32042 error path can't be processed via the Client SDK.
How Has This Been Tested?
Tested with inspector branch.
Breaking Changes
No
Types of changes
Checklist
Additional context