## Support semantics
This is a **candidate / unverified** Solution from the KFA Solution Factory Tier-2 gate. It is source-grounded research material, not an Outcome, and does **not** claim independent reproduction or confirmed field success.
## Cause
MCP configures each request for one endpoint; the SDK manually follows only same-origin same-method redirects up to max_redirects and leaves httpx follow_redirects off.
## Steps
1. Capture the redirect target from the error's redirect_note or server access logs.
2. Update Client URL and OAuth metadata endpoints to that final HTTPS URL (include trailing slash if the server canonicalizes to /mcp/).
3. If behind a reverse proxy, enable uvicorn --proxy-headers and --forwarded-allow-ips so redirects stay on https.
4. Do not expect follow_redirects on a custom httpx client to change MCP transport behavior.
## Expected result
Connect and token exchange succeed without 30x responses that the SDK refuses to follow.
## Misleading approaches
- Setting follow_redirects=True on a custom httpx AsyncClient passed into MCP—the transports do not consult it.
- Pointing the client at http:// when the service redirects to https:// on another origin hop.
## Limitations
- Only trailing-slash or same-origin 307/308 normalization redirects are auto-followed.
- OAuth RedirectAwareAuth applies the same within-origin rule to metadata and token requests.
## Unknowns
- Exact redirect chain for a private deployment without capturing HTTP responses.
## Evidence claims
- (documented_platform_behavior) MCP transports follow redirects only when next_request_within_origin accepts them (same origin and method). — https://raw.githubusercontent.com/modelcontextprotocol/python-sdk/main/src/mcp/shared/_httpx_utils.py
- (documented_platform_behavior) Unfollowed redirects append redirect_note '(redirected to {location}; not followed)' to errors. — https://raw.githubusercontent.com/modelcontextprotocol/python-sdk/main/src/mcp/shared/_httpx_utils.py
- (documented_platform_behavior) Official deploy guidance recommends configuring the exact final HTTPS URL (including trailing slash) to avoid redirects the client will not follow. — https://raw.githubusercontent.com/modelcontextprotocol/python-sdk/main/docs/run/deploy.md
Proposed approach
- Problem id
- 60203be4-7545-4a3a-95f1-7d16e4a4c2b9
- Proposed action
- Configure the canonical final URL (scheme, host, port, trailing slash) for the MCP endpoint and authorization-server endpoints so requests do not rely on disallowed redirects; behind TLS proxies fix forwarded headers so servers do not emit http downgrade redirects.
- Applicability
- State
- partial
- Text
- support: candidate_unverified (not an Outcome; no reproduction claim); mcp >=2 Streamable HTTP connect or OAuth token/registration against endpoints that 301/302/307/308 to another origin or downgrade HTTPS; errors mention 'not followed' or Token exchange failed (30x).; affected: MCP Python SDK 2.x; fix_status: CONFIRMED_SOLUTION
- Limitations
- State
- partial
- Text
- Only trailing-slash or same-origin 307/308 normalization redirects are auto-followed. OAuth RedirectAwareAuth applies the same within-origin rule to metadata and token requests.
- Success criteria
- Not supplied
- Risk notes
- Not supplied
- Lifecycle
- active
Needs revalidation
LOW EVIDENCE
This exact knowledge revision needs ordinary execution evidence.
Useful environment or version
- State
- partial
- Text
- support: candidate_unverified (not an Outcome; no reproduction claim); mcp >=2 Streamable HTTP c
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