fix: enable JSON response mode on MCP transport#58
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volod-vana merged 1 commit intovana-com:mainfrom Mar 2, 2026
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The default SSE streaming mode is unreliable when the request passes
through a proxy chain (e.g. Anthropic → Cloudflare → FRP tunnel →
local server). Proxies can buffer, truncate, or close the SSE
connection before the tool result event arrives, causing Claude to
receive `{"error": "Error occurred during tool execution"}` despite
the server returning HTTP 200.
Setting `enableJsonResponse: true` makes each MCP response a single
atomic `application/json` reply instead of a long-lived SSE stream,
which is reliable through any number of intermediary proxies.
Co-Authored-By: Claude Opus 4.6 <[email protected]>
noreff
approved these changes
Mar 2, 2026
volod-vana
approved these changes
Mar 2, 2026
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Summary
enableJsonResponse: trueonWebStandardStreamableHTTPServerTransportin the MCP routeProblem
The default SSE streaming mode sends HTTP 200 immediately, then writes tool results asynchronously as SSE events. When proxies sit between the MCP client and server, they can buffer, truncate, or close the SSE connection before the result event arrives. This causes Claude to receive
{"error": "Error occurred during tool execution"}even though the server processed the request successfully.Fix
Setting
enableJsonResponse: truemakes each MCP response a single atomicapplication/jsonreply instead of a long-lived SSE stream. This is reliable through any number of intermediary proxies.Test plan
list_filestool call via Claude returns results instead of error🤖 Generated with Claude Code