---
id: review-002-srv11-srv12-router-ordering
name: Router-layering fixes — double token resolution on WS and mcp, decoy 405 on extra routes (SRV-11, SRV-12)
status: completed
depends_on: []
scope: narrow
risk: medium
impact: component
level: implementation
tags: [server, review-002, stealth]
---

## Description

Two review-002 findings in `server/adapter.rs`'s `build_router` — both
are axum `route_layer`/merge-ordering semantics (empirically verified
in review 002 with an axum 0.8.9 harness; `route_layer` wraps routes
registered *before* the call):

- **SRV-11**: the router-wide `bearer_auth_middleware` layer (:328)
  wraps the WS route (registered earlier at :307-317 with its own
  `ws_bearer_auth`) and the `/mcp` nest (own layer at :288-292) — the
  token resolves **twice** on both, and the code comment claims the
  opposite ("resolves the token exactly once"). Benign today
  (ag stashes agree), but a provider with token-use side effects
  double-counts.
- **SRV-12**: `method_not_allowed_fallback(decoy_method_not_allowed)`
  (:322) covers only routers registered before the extras merge —
  wrong-method probes on **extra routes** return axum's bare 405 (no
  body, no `Server: nginx`), the exact stealth probe SRV-07's fix
  neutralized for the default surface.

## Acceptance Criteria

- [ ] SRV-11: the WS route resolves the token exactly once (drop the
      router-wide layer's application to it — e.g. verify with an
      axum-semantics-confirmed mechanism: register the WS route after
      the route_layer call, or exclude via per-route wrapping) and
      `/mcp` likewise (keep exactly one auth layer for it); the
      corrected comment states axum's actual `route_layer` semantics
- [ ] SRV-11 test: a counting IdentityProvider — one WS upgrade
      request resolves the token exactly once (and one `/mcp` request
      likewise, feature-gated)
- [ ] SRV-12: `method_not_allowed_fallback(decoy_method_not_allowed)`
      re-applied after the extras merge; test: wrong-method probe on
      an extra route carries the decoy body + `Server: nginx` header
- [ ] Re-verify the existing router tests (extra-routes auth, decoy
      405 default-surface, reserved-path panics) still pass — the
      merge-order changes must not regress SRV-01's guarantee
- [ ] `cargo test`, `cargo clippy --all-targets -- -D warnings`,
      `cargo fmt --check` pass

## References

- docs/reviews/002-post-remediation-review.md (Part A', SRV-11, SRV-12; hot-spot 2 in the server pass)
- src/server/adapter.rs:274-345 (build_router), :296-320 (comment + WS route), :322 (405 fallback), :328 (router-wide layer)
- tasks/server/review-001-extra-routes-auth.md (the SRV-01 ordering this must preserve), tasks/server/review-001-hyper-server-knobs.md (SRV-07's decoy-405 work)

## Notes

Order-sensitivity warning (from the server pass): "any future route
addition must re-derive these semantics empirically" — after fixing,
add the counting test + the extra-route 405 test so the invariants are
pinned, not just commented. The SRV-01 opt-out shape (inner layers
win) must remain exactly as tested. Keep the SRV-10 fold-in fix
(historical) intact — this task is about the *comment* being false and
the double-resolve being real.

## Summary

WS upgrade route + /mcp nest moved after the router-wide bearer route_layer (single token resolution each; WS MethodRouter fallback carries the decoy 405); method_not_allowed_fallback re-applied after the extras merge (SRV-12). 6 counting/shape tests pin the ordering invariants.