TypeScript MCP SDK: Duplicate Response

ImplementationTypeScript MCP SDKv1.30.0

StatusPassed

Transportstdio

TestedSep 26, 2026

Durationnull ms

Observations

Recorded behavior from this compatibility test.

Error callback reported a response for an unknown ID
Same-session ping succeeded after the duplicate response.

Evidence

Supporting records captured for this run.

observation

Duplicate response was reported through the TypeScript SDK error callback without closing the session.

Source: MCP Failure Lab 0.10.0 duplicate-response compatibility report

View raw evidence

The TypeScript SDK accepted the first result, then reported the repeated response through its error callback because the request ID was no longer pending. The diagnostic did not close the session. A same-session ping completed successfully.

Findings

Reviewed conclusions and upstream reporting state.

protocol-behavior

The TypeScript SDK surfaces duplicate responses through its error callback while keeping the session usable.

Not actionable upstream

Review: verified

Verified compatibility behavior: the TypeScript SDK reported the duplicate response through its error callback, preserved the first result, and remained usable for a same-session ping. No upstream defect was identified in the source report.