fix(gateway): detect stale remote empty-success tool responses#525
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syf2211 wants to merge 1 commit into
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fix(gateway): detect stale remote empty-success tool responses#525syf2211 wants to merge 1 commit into
syf2211 wants to merge 1 commit into
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When a remote streamable-http MCP session goes stale, upstream tool calls can return structurally empty successes (no content blocks) that the gateway previously forwarded as successful results. Detect these responses for remote servers, invalidate the cached client, and retry once when tool annotations declare the call is read-only or idempotent. Otherwise surface a protocol-level error instead of silently returning empty data. Fixes docker#505
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Summary
Detect structurally empty tool successes from stale remote streamable-http sessions and stop forwarding them as successful results.
Motivation
Fixes #505. When a remote MCP session goes stale, upstream
CallToolcan returnerr == nilwith an emptycontentarray. The gateway previously forwarded these as successful tool results, causing silent data loss on writes.Changes
isStaleEmptySuccessto detect empty success responses (!isError, no content blocks, no structured content).InvalidateKeptClientto evict and close a single cached remote client.callRemoteTool:readOnlyHintoridempotentHint, invalidate the stale client and retry once.Tests
All new tests pass.
Notes
serverConfig.IsRemote()only; Docker/stdio paths are unchanged.