fix(mcp): MCP OAuth broken - PEP 525 generator delegation bug (#12400) - #12409
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vominh1919 wants to merge 1 commit into
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fix(mcp): MCP OAuth broken - PEP 525 generator delegation bug (#12400)#12409vominh1919 wants to merge 1 commit into
vominh1919 wants to merge 1 commit into
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…ync_auth_flow The plain 'async for item in super().async_auth_flow(request): yield item' pattern does NOT forward asend() values back to the inner generator due to a PEP 525 limitation. The MCP SDK's auth flow (httpx.Auth flow) expects the caller to asend() the HTTP response back in, so without manual forwarding the flow silently receives None and OAuth token exchange / refresh breaks. Fixes NousResearch#12400
alt-glitch
added
type/bug
Collaborator
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Likely stale — #12717 (merged) already fixed the same MCP OAuth bidirectional auth_flow issue. Please verify this is still needed. |
Contributor
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Thanks for the thorough write-up and the correct diagnosis of the PEP 525 limitation, @vominh1919! This is an automated hermes-sweeper review. After verifying against current
The fix is already live on |
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Problem
MCP OAuth is broken because
async for item in super().async_auth_flow(request): yield itemdoes not forwardasend()values back to the inner generator.This is a known PEP 525 limitation — the
async for ... initeration protocol does not support bidirectional communication. The MCP SDK'sOAuthClientProvider.async_auth_flow(built onhttpx.Auth) usesasend()to receive the HTTP response from the caller. Without manual forwarding, the inner generator silently receivesNone, breaking token exchange and refresh.Fix
Replace the
async for ... yielddelegation with explicit bidirectional forwarding that properly handlesasend(),athrow(), andaclose().Files Changed
tools/mcp_oauth_manager.py—HermesMCPOAuthProvider.async_auth_flowmethod (lines 128-130 → bidirectional forwarding pattern)Closes #12400