fix: prevent double-prefixed McpError message when reconstructing from wire - #2802
Closed
KooshaPari wants to merge 1 commit into
Closed
fix: prevent double-prefixed McpError message when reconstructing from wire#2802KooshaPari wants to merge 1 commit into
KooshaPari wants to merge 1 commit into
Conversation
…m wire (fixes #2786) McpError's constructor prefixes messages with 'MCP error NNNN: ', and the server serializes this prefixed message as error.message. When the client reconstructs the error via fromError, the already-prefixed message gets the prefix added again, resulting in messages like: 'MCP error -32601: MCP error -32601: Unknown tool: nope' Fixed by stripping the prefix in fromError before passing to the constructor, so deserialized errors get exactly one prefix. Also changed the queued-response path in protocol.ts to use fromError consistently instead of new McpError.
|
commit: |
Author
|
Closing per author request. Will re-evaluate repo selection. |
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
Add this suggestion to a batch that can be applied as a single commit.This suggestion is invalid because no changes were made to the code.Suggestions cannot be applied while the pull request is closed.Suggestions cannot be applied while viewing a subset of changes.Only one suggestion per line can be applied in a batch.Add this suggestion to a batch that can be applied as a single commit.Applying suggestions on deleted lines is not supported.You must change the existing code in this line in order to create a valid suggestion.Outdated suggestions cannot be applied.This suggestion has been applied or marked resolved.Suggestions cannot be applied from pending reviews.Suggestions cannot be applied on multi-line comments.Suggestions cannot be applied while the pull request is queued to merge.Suggestion cannot be applied right now. Please check back later.
Fixes #2786
Problem
When a request handler throws
McpError, the client receives a double-prefixed message:This happens because:
McpError's constructor callssuper(MCP error ${code}: ${message}), so.messagealready carries the prefixmessage: error.message, sending the prefixed string over the wireMcpError.fromError()(and onenew McpError()call) reconstructs from the wire message, which adds the prefix againChanges
src/types.ts: AddedMcpError._stripErrorPrefix()to strip the"MCP error NNNN: "prefix before passing the message to the constructor infromError(). This ensures deserialized errors get exactly one prefix.src/shared/protocol.ts: Changed the queued-response error path to useMcpError.fromError()instead ofnew McpError(), so both deserialization paths benefit from the prefix stripping.test/shared/protocol.test.ts: Added 3 tests verifying thatfromErrordoes not double-prefix, correctly handles messages without prefix, and handles negative error codes.Testing