fix(core): set span.status to error when MCP tool returns JSON-RPC error response#20082
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fix(core): set span.status to error when MCP tool returns JSON-RPC error response#20082
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…ror response When a tool handler threw an error, completeSpanWithResults() was ending the span without setting its status to error. This caused all MCP tool spans to appear with span.status=ok in Sentry, breaking the failure_rate() metric in the MCP insights dashboard. The fix passes hasError=true to completeSpanWithResults() when the outgoing JSON-RPC response contains an error object, setting the span status to internal_error directly on the stored span (bypassing getActiveSpan() which doesn't return the right span at send() time). Co-Authored-By: claude-sonnet-4-6 <noreply@anthropic.com>
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Adds an `always-error` tool to the MCP e2e test apps and a test step that verifies the resulting transaction has span.status=internal_error when a tool throws. This covers the fix in the span status correlation path end-to-end, complementing the existing unit tests. Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
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Apr 2, 2026
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When an MCP tool returns a JSON-RPC error response (i.e. the response has an
errorfield instead ofresult), the span was being ended withstatus=ok. This meantfailure_rate()read 0% in the MCP insights dashboard even when tools were consistently failing.Root cause
completeSpanWithResultsalways ended the span without checking whether the response was an error. ThecaptureErrorpath usesgetActiveSpan(), which returnsnulloutside awithActiveSpan()context — so errors were never reflected in span status.Fix
Pass
!!message.erroras ahasErrorflag tocompleteSpanWithResults. Whentrue, setSPAN_STATUS_ERRORwithmessage: 'internal_error'directly on the stored span before ending it.Changes
correlation.ts—completeSpanWithResultsaccepts optionalhasErrorparam; sets error status when truetransport.ts— passes!!message.errorwhen completing spans on outgoing sendtransportInstrumentation.test.ts— two new tests: error response sets error status; success response does notCloses #20083