Fix Content-Length mismatch in authz response filter with remote proxies#4092
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Fix Content-Length mismatch in authz response filter with remote proxies#4092
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Codecov Report✅ All modified and coverable lines are covered by tests. Additional details and impacted files@@ Coverage Diff @@
## main #4092 +/- ##
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+ Coverage 68.60% 68.61% +0.01%
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Files 447 447
Lines 45758 45761 +3
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+ Hits 31391 31400 +9
+ Misses 11946 11939 -7
- Partials 2421 2422 +1 ☔ View full report in Codecov by Sentry. 🚀 New features to boost your workflow:
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JAORMX
approved these changes
Mar 11, 2026
When httputil.ReverseProxy forwards a response from a remote MCP server, it copies the backend's Content-Length header to the ResponseWriter via Header(). ResponseFilteringWriter does not override Header(), so the original Content-Length leaks to the real writer. After Cedar policy filtering changes the response body size, Go's HTTP server detects the mismatch and tears down the connection. Delete the stale Content-Length header before writing filtered responses for both JSON and SSE content types. Go's HTTP library will handle correct framing automatically. Fixes: #4044 Co-Authored-By: ChandraMohan0316 <chandrashanmugam007@gmail.com>
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JAORMX
approved these changes
Mar 11, 2026
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When httputil.ReverseProxy forwards a response from a remote MCP server, it copies the backend's Content-Length header to the ResponseWriter via Header(). ResponseFilteringWriter does not override Header(), so the original Content-Length leaks to the real writer. After Cedar policy filtering changes the response body size, Go's HTTP server detects the mismatch and tears down the connection.
Delete the stale Content-Length header before writing filtered responses for both JSON and SSE content types. Go's HTTP library will handle correct framing automatically.
Fixes: #4044