fix: call onerror for silently swallowed transport errors #1529
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Nested try/catch blocks in WebStandardStreamableHTTPServerTransport's handlePostRequest were returning error responses without invoking the onerror callback, making transport errors invisible to consumers. Fixes: - JSON parsing errors (req.json() failures) now call onerror - JSON-RPC message validation errors now call onerror - writeSSEEvent failures now call onerror instead of silently returning false Closes modelcontextprotocol#1395 Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
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@modelcontextprotocol/client
@modelcontextprotocol/server
@modelcontextprotocol/express
@modelcontextprotocol/hono
@modelcontextprotocol/node
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Summary
WebStandardStreamableHTTPServerTransport.handlePostRequestwere returning error responses without invoking theonerrorcallback, making transport errors invisible to consumersreq.json()failures) now callonerrorbefore returning the error responseonerrorwriteSSEEventfailures now callonerrorinstead of silently returningfalseCloses #1395
Test plan
pnpm typecheck:allpassespnpm --filter @modelcontextprotocol/server test— all 37 tests passonerrorfires for invalid JSON request bodyonerrorfires for malformed JSON-RPC messagesonerrorfires when SSE stream write fails🤖 Generated with Claude Code