Point to the proxy's access log for a login flood's source

No log line records the client address taken from X-Forwarded-For, so the login endpoint section no longer says the source shows in the failure logs; it names the proxy's access log instead. Model: opus-5-5
Say that any private-addressed client can choose its rate-limit key
2026-09-29 09:01:49 +00:00 · 2026-09-29 08:58:10 +00:00 · 2026-09-29 08:58:10 +00:00
24 changed files with 214 additions and 458 deletions
@@ -147,7 +147,7 @@ TTY detection, and security headers are always applied.
 | `RETENTION_SWEEP_INTERVAL` | How often the retention reaper and archive sweeper run (Go duration, must be positive) | `1h` |
 | `SESSION_IDLE_TIMEOUT`  | Idle session timeout (Go duration)  | `24h`    |
 | `RECEIVER_RATE_LIMIT`   | Receiver requests/minute per IP per entrypoint (10x that per IP across the route) | `120` |
-| `TRUSTED_PROXIES`       | CIDRs whose forwarded headers are trusted (unset: all clients behind a proxy share one rate-limit bucket; a correct login password is never throttled either way) | `""` (none) |
+| `TRUSTED_PROXIES`       | CIDRs whose forwarded headers are trusted. A set value replaces the default. Under the default, any client with a private address, whether it connects directly or through the proxy, can choose its own rate-limit key by sending its own `X-Forwarded-For`; if any clients have private addresses, set it to the proxy's address alone. See [Trusted proxies](#trusted-proxies) | `10.0.0.0/8,172.16.0.0/12,192.168.0.0/16` (RFC 1918) |
 | `ALLOWED_EGRESS_CIDRS`  | CIDRs that delivery targets may reach despite the SSRF blocklist. Read [Allowing egress to your own network](#allowing-egress-to-your-own-network) before setting it | `""` (none) |

 #### Allowing egress to your own network
@@ -379,41 +379,48 @@ unlocked.
 `TRUSTED_PROXIES` is a comma-separated list of CIDR blocks (a bare
 address such as `192.168.1.7` is accepted and treated as a single
 host), for example `192.168.1.7, 2001:db8::5`. It decides whose
-`X-Forwarded-For` header the rate limiters believe, so it should name
-the addresses of your reverse proxies and nothing else.
+`X-Forwarded-For` header the rate limiters believe, so it should cover
+the addresses of your reverse proxies.

 `X-Forwarded-For` is honoured **only** when the connecting peer is
 inside one of these blocks; for every other peer the client identity is
-the connection's own address and the header is ignored. The default is
-the empty list, which trusts nobody — anything else would let any
-client pick its own rate limit bucket, minting a fresh one per request
-or draining someone else's. Set it to the address of your reverse
-proxy, and to nothing wider. A set but unparseable value aborts
-startup.
+the connection's own address and the header is ignored. Unset (or
+empty), the list is the RFC 1918 private ranges: `10.0.0.0/8`,
+`172.16.0.0/12` and `192.168.0.0/16`. That covers a reverse proxy
+reaching webhooker over a Docker network or a private LAN without
+anything set. A set value replaces the default entirely. A set but
+unparseable value aborts startup.

-That default is safe against forged headers, but leaving it unset in
-production has a cost you must know about. Production runs behind a
-TLS-terminating reverse proxy, so with `TRUSTED_PROXIES` unset every
-request keys on the proxy's own address and all clients share a single
+Trusting those ranges has two consequences for clients with private
+addresses:
+
+- Any such client, whether it connects directly or through the proxy,
+  can choose its own rate-limit key by sending its own
+  `X-Forwarded-For`. A direct client's header is walked because the
+  client is itself trusted; behind the proxy, the client's own address
+  is skipped as a trusted hop when the chain is walked (below), so the
+  entry it wrote is taken as the client. If any of your clients have
+  private addresses, you must set `TRUSTED_PROXIES` to the proxy's
+  address alone.
+- A client behind the proxy that sends no `X-Forwarded-For` of its own
+  shares the proxy's bucket, because its own address is skipped too.
+  Setting the list to the proxy's address alone gives each its own
+  bucket.
+
+A proxy the list does not cover, such as nginx on the same host
+reaching webhooker over loopback, is not trusted: every request through
+it keys on the proxy's own address and all clients share a single
 bucket per limit. The receiver limits become service-wide ceilings,
 and the login endpoint's failure counting collapses onto one key, so a
 stranger's wrong passwords throttle every other client's wrong
-passwords.
+passwords. Set `TRUSTED_PROXIES` to that proxy's address to restore
+per-client buckets.

 What it cannot do is lock the operator out. The login endpoint
 verifies credentials **before** it consults any limit and charges only
 failures, so a correct password is never throttled no matter how full
 the bucket is. See [Rate Limiting](#rate-limiting).

-The remedy is to set `TRUSTED_PROXIES` to your reverse proxy's
-address, which restores per-client buckets. webhooker logs a warning
-at startup whenever `TRUSTED_PROXIES` is empty, in every environment,
-because behind a proxy every client shares one bucket in `dev` and
-`prod` alike. The warning is informational when nothing proxies to the
-process: with no proxy in front, the peer address is the client's own
-and the buckets are already per-client. See
-[Rate Limiting](#rate-limiting) for what each limit shares.
-
 `X-Real-IP` and `True-Client-IP` are **never** read, from any peer.
 Reverse proxies append to `X-Forwarded-For` but forward other client
 headers verbatim, so a single-valued header is client-controlled even
@@ -435,14 +442,14 @@ Two operator requirements follow:
  (nginx `$proxy_add_x_forwarded_for`, HAProxy `option forwardfor`,
  Caddy and AWS ALB by default), and must append a bare address with
  no port.
- List proxy hosts **only**. Any address inside `TRUSTED_PROXIES`
+- Keep clients out of the list. Any address inside `TRUSTED_PROXIES`
  chooses its own rate-limit key: its `X-Forwarded-For` is walked, so
  it can name a different address on every request to get a fresh
  bucket each time, or name another client's address to drain that
-  client's bucket. Never list a block that also covers clients — a
-  broad `10.0.0.0/8` on a network where clients live in the same range
-  makes all three limits, including the unauthenticated webhook
-  receiver, silently bypassable by every client in the block.
+  client's bucket. A block that also covers clients — the default, on
+  a network where clients have private addresses — makes all three
+  limits, including the unauthenticated webhook receiver, silently
+  bypassable by every client in the block.

 #### Sessions

@@ -764,10 +771,16 @@ repository's `Dockerfile` and runs it. The app needs:

 - **Environment variables:**
    - `WEBHOOKER_ENVIRONMENT=prod`
-    - `TRUSTED_PROXIES`: your reverse proxy's address on that Docker
-      network. The `remoteIP` field of the `http request` log line for a
-      request that came through the proxy shows it; the health check's
-      own lines show `::1`. See [Trusted proxies](#trusted-proxies).
+    - `TRUSTED_PROXIES`: Docker networks use private addresses, so the
+      default covers your reverse proxy on that network. Under the
+      default, any client with a private address, whether it connects
+      directly or through the proxy, can choose its own rate-limit key
+      by sending its own `X-Forwarded-For`. If any clients have private
+      addresses, or the network's addresses are outside the RFC 1918
+      ranges, set it to the proxy's address there. The `remoteIP` field
+      of the `http request` log line for a request that came through
+      the proxy shows it; the health check's own lines show `::1`. See
+      [Trusted proxies](#trusted-proxies).
    - Leave `BIND_ADDRESS` and `DATA_DIR` unset: the image sets
      `BIND_ADDRESS` to `0.0.0.0`, and `DATA_DIR` defaults to
      `/var/lib/webhooker`.
@@ -830,12 +843,14 @@ reports.
   behind a proxy means the `X-Forwarded-Proto` header. The block below
   sets it; without it every request is read as plaintext and cookies
   ship without `Secure`. See [Configuration](#configuration).
-3. **Set `TRUSTED_PROXIES` to the proxy's address.** Unset, every rate
-   limiter keys on the connecting peer, which behind a proxy is the
-   proxy on every request: all clients collapse into one global bucket
-   per limit and the receiver's per-IP limits become service-wide
-   ceilings. See [Trusted proxies](#trusted-proxies). List the proxy
-   and nothing else.
+3. **Make sure `TRUSTED_PROXIES` covers the proxy's address.** Unset,
+   it covers the RFC 1918 private ranges, so a proxy on a Docker
+   network or a private LAN is covered and one on loopback is not. For
+   a proxy it does not cover, every rate limiter keys on the connecting
+   peer, which is the proxy on every request: all clients collapse into
+   one global bucket per limit and the receiver's per-IP limits become
+   service-wide ceilings. See [Trusted proxies](#trusted-proxies). If
+   any clients have private addresses, list the proxy and nothing else.
 4. **Send `Host` as `$http_host`, not `$host`.** `$host` strips the
   port. webhooker's Origin/Referer check compares against the host it
   was given, so on any port other than 443 `$host` makes every form
@@ -1396,10 +1411,11 @@ It uses:
 - **[go-chi/httprate](https://github.com/go-chi/httprate)** for
  sliding-window rate limiting of the password-change and webhook
  receiver endpoints. The bucket is per client IP only when
-  `TRUSTED_PROXIES` names the reverse proxy; unset, every client
-  behind that proxy shares one bucket per limit. The login endpoint
-  counts failed attempts itself instead, so that a correct password is
-  never throttled (see [Rate Limiting](#rate-limiting))
+  `TRUSTED_PROXIES` covers the reverse proxy (by default it covers the
+  RFC 1918 private ranges); otherwise every client behind that proxy
+  shares one bucket per limit. The login endpoint counts failed
+  attempts itself instead, so that a correct password is never
+  throttled (see [Rate Limiting](#rate-limiting))
 - **[Prometheus](https://prometheus.io)** for metrics, served at
  `/metrics` behind basic auth
 - **[Sentry](https://sentry.io)** for optional error reporting
@@ -2580,30 +2596,30 @@ let one subscriber rotate source addresses and mint a fresh bucket per
 request, evading these limits at the network layer without spoofing
 anything; the cost is that distinct clients inside one `/64` share a
 bucket. IPv4-mapped addresses (`::ffff:1.2.3.4`) key as the IPv4 address
-they carry. See [Trusted proxies](#trusted-proxies). Deployed without that
-variable set, a client behind a reverse proxy shares one bucket with
-every other client behind the same proxy. Set `TRUSTED_PROXIES` to the
-proxy's address to get per-client limits back. What the shared bucket
+they carry. See [Trusted proxies](#trusted-proxies). When that variable
+does not cover the reverse proxy, a client behind it shares one bucket
+with every other client behind the same proxy. Set `TRUSTED_PROXIES` to
+the proxy's address to get per-client limits back. What the shared bucket
 costs is not the same for every limiter, and the two cases pull in
 opposite directions:

 - For the **receiver** limits it costs throughput, which is the safe
  direction to be wrong in: sharing can only make a limit bind sooner,
  never let a sender past it. It matters more for the aggregate limit
-  than for the per-entrypoint one: with `TRUSTED_PROXIES` unset behind
-  the reverse proxy a production deployment is required to run behind,
-  every request keys on the proxy, so the aggregate limit becomes a
-  service-wide ceiling of 1200 requests per minute across all senders
-  and all entrypoints, where the per-entrypoint limit's capacity still
-  grows with the number of entrypoints. Any deployment with more than a
-  handful of busy entrypoints must set `TRUSTED_PROXIES`.
+  than for the per-entrypoint one: when `TRUSTED_PROXIES` does not
+  cover the reverse proxy a production deployment is required to run
+  behind, every request keys on the proxy, so the aggregate limit
+  becomes a service-wide ceiling of 1200 requests per minute across all
+  senders and all entrypoints, where the per-entrypoint limit's
+  capacity still grows with the number of entrypoints. Any deployment
+  with more than a handful of busy entrypoints must make sure
+  `TRUSTED_PROXIES` covers its proxy.
 - For the **login and password-change** limits it costs precision, not
  availability. Login failures from every client land in one counter,
  so a stranger's wrong passwords make the operator's own wrong
  passwords answer `429` sooner; the operator's _correct_ password is
  never affected, because it is never counted. Production deployments
-  should still set `TRUSTED_PROXIES`; webhooker warns at startup
-  whenever it is empty, in any environment.
+  should still make sure `TRUSTED_PROXIES` covers their proxy.

 #### The login endpoint

@@ -2706,8 +2722,10 @@ re-fills both verification slots on its first two requests. The
 remedies are to block the source at the reverse proxy, or to
 rate-limit `POST /pages/login` there — the one place a limit can be
 applied without reintroducing the lockout, because the proxy sees the
-real client address. Setting `TRUSTED_PROXIES` does not stop the
-saturation, but it makes the source visible in the failure logs.
+real client address. `TRUSTED_PROXIES` does not stop the saturation.
+The flood's source is in the proxy's access log: webhooker's own logs
+record the proxy's address, not the client's (see
+[Deployment behind a reverse proxy](#deployment-behind-a-reverse-proxy)).

 Finer-grained per-webhook rate limits (configured in the web UI and
 enforced in the webhook handler) can layer on top of this env-level
@@ -2721,7 +2739,7 @@ abuse limit later; they are tracked as future work.
 | ------ | --------------------------- | ----------- |
 | `GET`  | `/`                         | Root redirect, 303 (authenticated → `/sources`, unauthenticated → `/pages/login`) |
 | `GET`  | `/.well-known/healthcheck`  | Health check (JSON: `status`, `now`, `uptimeSeconds`, `uptimeHuman`, `version`, `appname`, `maintenanceMode`) |
-| `GET`, `HEAD` | `/s/*`              | Static file serving (embedded CSS, JS). `GET` and `HEAD` only — `POST`, `PUT`, `PATCH`, `DELETE`, `OPTIONS`, `TRACE` and `CONNECT` are answered `405 Method Not Allowed` with `Allow: GET, HEAD`. Any other method (such as `PROPFIND`) is refused by chi before it reaches this route, and gets `405` without an `Allow` header. Pinned by `TestStaticServesOnlyGetAndHead` |
+| any    | `/s/*`                      | Static file serving (embedded CSS, JS). Mounted for every method, not just `GET`/`HEAD`: chi's `Mount` registers all methods and `http.FileServer` special-cases only `HEAD` (by omitting the body), so a `POST` or `DELETE` to an asset is answered `200` with the file. Pinned by `TestStaticServesEveryMethod` |
 | `POST` | `/webhook/{uuid}`           | Webhook receiver endpoint. `POST` only — every other method is answered `405 Method Not Allowed` with `Allow: POST`. Rate limited (see [Rate Limiting](#rate-limiting)) |

 #### Authentication Endpoints
@@ -3064,10 +3082,9 @@ check, see [The login endpoint](#the-login-endpoint).
  It runs behind session auth, so only a client already holding a
  valid session reaches it, and an operator throttled out of changing
  a password can still log in. The bucket is per client IP only when
-  `TRUSTED_PROXIES` names the reverse proxy; unset, every client
+  `TRUSTED_PROXIES` covers the reverse proxy; otherwise every client
  shares one bucket, which costs precision rather than availability
-  (see [Rate Limiting](#rate-limiting)). webhooker warns at startup
-  whenever `TRUSTED_PROXIES` is empty
+  (see [Rate Limiting](#rate-limiting))
 - Prometheus metrics behind basic auth
 - Static assets embedded in binary (no filesystem access needed at
  runtime)
@@ -16,7 +16,6 @@ import (
 	"sneak.berlin/go/webhooker/internal/handlers"
 	"sneak.berlin/go/webhooker/internal/healthcheck"
 	"sneak.berlin/go/webhooker/internal/logger"
-	"sneak.berlin/go/webhooker/internal/metrics"
 	"sneak.berlin/go/webhooker/internal/middleware"
 	"sneak.berlin/go/webhooker/internal/resetpw"
 	"sneak.berlin/go/webhooker/internal/server"
@@ -178,10 +177,6 @@ func newApp() *fx.App {
 			healthcheck.New,
 			session.New,
 			handlers.New,
-			// The registry /metrics serves, and the delivery
-			// collectors registered on it.
-			metrics.NewRegistry,
-			metrics.New,
 			middleware.New,
 			// The one SSRF guard both target-creation validation
 			// and the delivery dialer consult, so they cannot
@@ -75,6 +75,11 @@ const (
 	// internet-exposed endpoint.
 	defaultReceiverRateLimit = 120

+	// defaultTrustedProxies is TRUSTED_PROXIES when it is unset: the
+	// RFC 1918 private ranges, which a reverse proxy reaching the
+	// process over a Docker network or a private LAN connects from.
+	defaultTrustedProxies = "10.0.0.0/8,172.16.0.0/12,192.168.0.0/16"
+
 	// maxPort is the highest valid TCP port number. The lower
 	// bound (at least 1) is enforced by envPositiveInt.
 	maxPort = 65535
@@ -172,13 +177,14 @@ type Config struct {

 	// TrustedProxies is the set of networks whose members are
 	// allowed to speak for the client with X-Forwarded-For, the
-	// only forwarded header read. It is empty unless
-	// TRUSTED_PROXIES is set, and empty means no peer is
-	// trusted: forwarded headers are then ignored entirely and
-	// clients are identified by the connection's own address.
-	// Members can choose their own rate-limit key, so this must
-	// name proxy hosts only, never a block that also covers
-	// clients.
+	// only forwarded header read. Unless TRUSTED_PROXIES is set it
+	// is the RFC 1918 private ranges (defaultTrustedProxies).
+	// Other peers' forwarded headers are ignored and they are
+	// identified by the connection's own address. Under the
+	// default any client with a private address, directly or
+	// through a proxy, can choose its own rate-limit key, so
+	// where any clients have private addresses this must be set
+	// to the proxy hosts alone.
 	TrustedProxies []netip.Prefix

 	// AllowedEgressCIDRs is the set of networks a delivery target
@@ -460,14 +466,15 @@ func parseCIDR(entry string) (netip.Prefix, error) {

 // envPrefixList returns the value of the named environment variable
 // parsed as a comma-separated list of CIDR blocks (bare addresses
-// allowed). An unset, empty, or blank value yields an empty list. A
-// set value containing an unparseable entry is a hard error naming
-// the key and the bad entry, so startup fails loudly rather than
-// silently running with a list the operator did not intend.
-func envPrefixList(key string) ([]netip.Prefix, error) {
+// allowed). An unset, empty, or blank value is read as defaultValue
+// instead. A set value containing an unparseable entry is a hard
+// error naming the key and the bad entry, so startup fails loudly
+// rather than silently running with a list the operator did not
+// intend.
+func envPrefixList(key, defaultValue string) ([]netip.Prefix, error) {
 	v := strings.TrimSpace(os.Getenv(key))
 	if v == "" {
-		return nil, nil
+		v = defaultValue
 	}

 	var prefixes []netip.Prefix
@@ -681,12 +688,12 @@ func loadFromEnv() (*Config, error) {
 		return nil, err
 	}

-	trustedProxies, err := envPrefixList("TRUSTED_PROXIES")
+	trustedProxies, err := envPrefixList("TRUSTED_PROXIES", defaultTrustedProxies)
 	if err != nil {
 		return nil, err
 	}

-	allowedEgressCIDRs, err := envPrefixList("ALLOWED_EGRESS_CIDRS")
+	allowedEgressCIDRs, err := envPrefixList("ALLOWED_EGRESS_CIDRS", "")
 	if err != nil {
 		return nil, err
 	}
@@ -760,50 +767,6 @@ func (c *Config) warnEgressAllowlist(log *slog.Logger) {
 	)
 }

-// warnSharedRateLimitBucket logs a startup warning whenever
-// TRUSTED_PROXIES is empty, in any environment.
-//
-// With no trusted proxies every rate limiter keys on the connecting
-// peer's address. Whether that is harmless or dangerous depends on
-// what is in front of the process, which this code cannot observe:
-// with nothing in front, the peer is the client and the limits are
-// per-client as intended; behind a reverse proxy the peer is the proxy
-// for every request, so all clients share one bucket per limiter.
-//
-// The login endpoint no longer spends budget on arrival — it verifies
-// credentials first and charges only failures — so a shared bucket
-// cannot deny the operator a correct password. What it does collapse
-// is the failure counting: one client's wrong passwords throttle
-// everyone else's wrong passwords, and the receiver's limits become
-// service-wide ceilings.
-//
-// The warning is deliberately not gated on WEBHOOKER_ENVIRONMENT:
-// behind a proxy every client shares one bucket in dev and prod alike.
-//
-// The default of trusting nobody is deliberate — trusting forwarded
-// headers from arbitrary peers lets any client choose its own bucket —
-// so this warns rather than failing startup or changing the key.
-func (c *Config) warnSharedRateLimitBucket(log *slog.Logger) {
-	if len(c.TrustedProxies) > 0 {
-		return
-	}
-
-	log.Warn(
-		"TRUSTED_PROXIES is empty: every rate limit keys on the "+
-			"connecting peer's address. With nothing proxying to "+
-			"this process that is the client itself and the limits "+
-			"are per-client as intended. Behind a reverse proxy the "+
-			"peer is the proxy on every request, so all clients "+
-			"share one bucket per limit: the receiver limits become "+
-			"service-wide ceilings, and one client's failed logins "+
-			"throttle every other client's failed logins — a "+
-			"correct password still gets in. If anything proxies to "+
-			"this process, set TRUSTED_PROXIES to its address.",
-		"environment", c.Environment,
-		"trustedProxies", len(c.TrustedProxies),
-	)
-}
-
 // New creates a Config by reading environment variables.
 //
 //nolint:revive // lc parameter is required by fx even if unused.
@@ -849,7 +812,6 @@ func New(lc fx.Lifecycle, params ConfigParams) (*Config, error) {
 		"hasMetricsAuth", s.MetricsAuthEnabled(),
 	)

-	s.warnSharedRateLimitBucket(log)
 	s.warnEgressAllowlist(log)

 	return s, nil
@@ -551,6 +551,11 @@ func testReceiverRateLimitSuccess(
 }

 func TestTrustedProxies(t *testing.T) {
+	// Unset, the RFC 1918 private ranges are trusted, so a reverse
+	// proxy on a Docker network or a private LAN is covered without
+	// configuration.
+	defaultProxies := []string{cidrPrivateV4, "172.16.0.0/12", "192.168.0.0/16"}
+
 	tests := []struct {
 		name        string
 		set         bool
@@ -559,18 +564,21 @@ func TestTrustedProxies(t *testing.T) {
 		expected    []string
 	}{
 		{
-			// The default must be "trust nobody": an empty list
-			// means forwarded headers are ignored, never that
-			// every peer may speak for the client.
 			name:     caseUnsetUsesDefault,
 			set:      false,
-			expected: []string{},
+			expected: defaultProxies,
 		},
 		{
-			name:     "blank value trusts nothing",
+			name:     "blank value uses default",
 			set:      true,
 			value:    "  ",
-			expected: []string{},
+			expected: defaultProxies,
+		},
+		{
+			name:     "set value replaces the default entirely",
+			set:      true,
+			value:    "203.0.113.7",
+			expected: []string{"203.0.113.7/32"},
 		},
 		{
 			name:  caseValidValueParsed,
@@ -845,101 +853,6 @@ func TestEgressAllowlistWarning(t *testing.T) {
 	}
 }

-// TestSharedRateLimitBucketWarning covers the startup warning that
-// tells an operator a deployment behind a reverse proxy shares one
-// rate-limit bucket between every client, which turns the receiver
-// limits into service-wide ceilings and collapses login failure
-// counting. It must fire whenever TRUSTED_PROXIES is empty, in any
-// environment, because behind a proxy every client shares one bucket
-// in dev and prod alike. It stays quiet once proxies are named.
-func TestSharedRateLimitBucketWarning(t *testing.T) {
-	tests := []struct {
-		name           string
-		environment    string
-		trustedProxies string
-		expectWarning  bool
-	}{
-		{
-			name:          "prod without trusted proxies warns",
-			environment:   config.EnvironmentProd,
-			expectWarning: true,
-		},
-		{
-			name:           "prod with trusted proxies is quiet",
-			environment:    config.EnvironmentProd,
-			trustedProxies: cidrPrivateV4,
-			expectWarning:  false,
-		},
-		{
-			name:          "dev without trusted proxies warns",
-			environment:   config.EnvironmentDev,
-			expectWarning: true,
-		},
-		{
-			name:           "dev with trusted proxies is quiet",
-			environment:    config.EnvironmentDev,
-			trustedProxies: cidrPrivateV4,
-			expectWarning:  false,
-		},
-	}
-
-	for _, tt := range tests {
-		t.Run(tt.name, func(t *testing.T) {
-			// Cannot use t.Parallel() here because t.Setenv
-			// is incompatible with parallel subtests.
-			t.Setenv("WEBHOOKER_ENVIRONMENT", tt.environment)
-
-			if tt.trustedProxies == "" {
-				require.NoError(
-					t, os.Unsetenv("TRUSTED_PROXIES"),
-				)
-			} else {
-				t.Setenv("TRUSTED_PROXIES", tt.trustedProxies)
-			}
-
-			var buf bytes.Buffer
-
-			log := slog.New(slog.NewJSONHandler(
-				&buf, &slog.HandlerOptions{
-					Level: slog.LevelDebug,
-				},
-			))
-
-			require.NoError(
-				t,
-				config.WarnSharedRateLimitBucketForTest(log),
-			)
-
-			if !tt.expectWarning {
-				assert.Empty(t, buf.String())
-
-				return
-			}
-
-			logged := buf.String()
-
-			assert.Contains(t, logged, `"level":"WARN"`)
-			assert.Contains(t, logged, "TRUSTED_PROXIES")
-			assert.Contains(t, logged, "share one bucket")
-			assert.Contains(
-				t, logged, "throttle every other client's failed logins",
-			)
-			// The warning must not claim a lockout the login
-			// endpoint no longer permits: credentials are verified
-			// before any budget is spent.
-			assert.Contains(
-				t, logged, "a correct password still gets in",
-			)
-			// The text must stay accurate for a developer with
-			// nothing in front of the process, where an empty
-			// list costs nothing.
-			assert.Contains(
-				t, logged, "nothing proxying to this process",
-			)
-		})
-	}
-}
-
 // metricsEnv describes what one subtest below puts in the
 // environment for a single METRICS_ variable. A variable that is
 // set to the empty string and one that is not set at all are
@@ -6,21 +6,6 @@ import "log/slog"
 // the external config_test package so each helper can be covered by
 // its own table-driven test without weakening the package API.

-// WarnSharedRateLimitBucketForTest loads a Config from the current
-// environment and emits its startup warnings to log. The real logger
-// writes to stdout, so this lets the warning's firing condition be
-// asserted against a handler the test controls.
-func WarnSharedRateLimitBucketForTest(log *slog.Logger) error {
-	c, err := loadFromEnv()
-	if err != nil {
-		return err
-	}
-
-	c.warnSharedRateLimitBucket(log)
-
-	return nil
-}
-
 // WarnEgressAllowlistForTest loads a Config from the current
 // environment and emits its egress-allowlist startup warning to
 // log, so a test can assert both that the warning fires only when
@@ -148,7 +148,6 @@ type EngineParams struct {
 	DBManager *database.WebhookDBManager
 	Logger    *logger.Logger
 	SSRFGuard *Guard
-	Metrics   *metrics.Set
 }

 // Engine processes queued deliveries in the background
@@ -168,10 +167,10 @@ type Engine struct {
 	retryCh    chan Task
 	workers    int

-	// mtr is the delivery metric set. Production wires the one
-	// registered on the registry /metrics serves; a test can
-	// substitute a set registered on a registry it holds, so it can
-	// gather what its own deliveries recorded.
+	// mtr is the delivery metric set. Production wires the
+	// process-wide one; a test can substitute a set registered on
+	// a private registry so its assertions are not disturbed by
+	// deliveries other tests are making at the same time.
 	mtr *metrics.Set

 	// targets maps each target type to its implementation.
@@ -205,7 +204,7 @@ func New(
 		deliveryCh: make(chan Task, deliveryChannelSize),
 		retryCh:    make(chan Task, retryChannelSize),
 		workers:    defaultWorkers,
-		mtr:        params.Metrics,
+		mtr:        metrics.Default(),
 	}

 	e.initTargets(&http.Client{
@@ -9,7 +9,6 @@ import (
 	"net/url"
 	"time"

-	"github.com/prometheus/client_golang/prometheus"
 	"go.uber.org/fx"
 	"gorm.io/gorm"
 	"sneak.berlin/go/webhooker/internal/database"
@@ -390,7 +389,7 @@ func NewTestEngine(
 		deliveryCh: make(chan Task, deliveryChannelSize),
 		retryCh:    make(chan Task, retryChannelSize),
 		workers:    workers,
-		mtr:        metrics.New(prometheus.NewRegistry()),
+		mtr:        metrics.Default(),
 	}
 	e.initTargets(client)

@@ -405,7 +404,7 @@ func NewTestEngineSmallRetry(
 	e := &Engine{
 		log:     log,
 		retryCh: make(chan Task, 1),
-		mtr:     metrics.New(prometheus.NewRegistry()),
+		mtr:     metrics.Default(),
 	}
 	e.initTargets(nil)

@@ -428,7 +427,7 @@ func NewTestEngineWithDB(
 		deliveryCh: make(chan Task, deliveryChannelSize),
 		retryCh:    make(chan Task, retryChannelSize),
 		workers:    workers,
-		mtr:        metrics.New(prometheus.NewRegistry()),
+		mtr:        metrics.Default(),
 	}
 	e.initTargets(client)

@@ -436,7 +435,8 @@ func NewTestEngineWithDB(
 }

 // ExportSetMetrics substitutes the engine's metric set, so a test can
-// assert on collectors registered on a registry it holds.
+// assert on collectors registered on a private registry instead of
+// the process-wide ones every other test is also moving.
 func (e *Engine) ExportSetMetrics(mtr *metrics.Set) {
 	e.mtr = mtr
 }
@@ -35,8 +35,9 @@ const (
 )

 // mIsolate gives the setup's engine a metric set registered on a
-// registry this test holds, so its exact assertions can gather from
-// it.
+// private registry. The process-wide collectors are moved by every
+// other delivery test running in parallel, so exact assertions are
+// only possible against a registry this test owns.
 func mIsolate(
 	t *testing.T, s iSetup,
 ) *prometheus.Registry {
@@ -103,9 +103,10 @@ func (h *Handlers) renderLoginError(
 // The credential check runs BEFORE any rate-limit budget is
 // consulted, and only a failed check spends budget. That is what
 // keeps the single administrative path reachable: behind the reverse
-// proxy this deployment requires, with TRUSTED_PROXIES unset, every
-// client shares one bucket, so a limiter spent on arrival lets any
-// stranger deny the operator's own correct password indefinitely.
+// proxy this deployment requires, when TRUSTED_PROXIES does not cover
+// it, every client shares one bucket, so a limiter spent on arrival
+// lets any stranger deny the operator's own correct password
+// indefinitely.
 //
 // Verifying first means every login POST costs an Argon2id hash, so
 // the work is taken under a bounded number of verification slots.
@@ -25,7 +25,7 @@ const (

 	// sharedProxyPeer is the whole point of this file. Production is
 	// required to run behind a TLS-terminating reverse proxy, and
-	// TRUSTED_PROXIES defaults to empty, so every client — attacker
+	// when TRUSTED_PROXIES does not cover it every client — attacker
 	// and operator alike — reaches the process from the proxy's
 	// address and shares one rate-limit bucket. Both parties in
 	// these tests therefore use the same RemoteAddr.
@@ -115,11 +115,11 @@ func floodFailures(
 // done-criterion of https://git.eeqj.de/sneak/webhooker/issues/150.
 //
 // The attacker and the operator share one rate-limit bucket, because
-// behind the mandated reverse proxy with TRUSTED_PROXIES unset every
-// client keys on the proxy's address. The attacker floods the
-// operator's own username — a single-admin product has a predictable
-// one — far past the failure limit. The operator must still be able
-// to log in with the correct password.
+// behind the mandated reverse proxy, when TRUSTED_PROXIES does not
+// cover it, every client keys on the proxy's address. The attacker
+// floods the operator's own username — a single-admin product has a
+// predictable one — far past the failure limit. The operator must
+// still be able to log in with the correct password.
 //
 // This fails if credentials stop being verified ahead of the limiter.
 func TestLogin_StrangersFloodCannotLockOutTheOperator(t *testing.T) {
@@ -12,7 +12,6 @@ import (
 	"net/http"
 	"sync/atomic"

-	"github.com/prometheus/client_golang/prometheus"
 	"go.uber.org/fx"
 	"sneak.berlin/go/webhooker/internal/database"
 	"sneak.berlin/go/webhooker/internal/delivery"
@@ -62,8 +61,6 @@ type HandlersParams struct {
 	Notifier     delivery.Notifier
 	Evictor      delivery.WebhookEvictor
 	SSRFGuard    *delivery.Guard
-	Metrics      *metrics.Set
-	Registry     *prometheus.Registry
 }

 // Handlers provides HTTP handler methods for all application
@@ -125,7 +122,7 @@ func New(
 	s.mw = params.Middleware
 	s.notifier = params.Notifier
 	s.evictor = params.Evictor
-	s.mtr = params.Metrics
+	s.mtr = metrics.Default()
 	s.ssrf = params.SSRFGuard

 	// Parse all page templates once at startup
@@ -20,7 +20,6 @@ import (
 	"sneak.berlin/go/webhooker/internal/handlers"
 	"sneak.berlin/go/webhooker/internal/healthcheck"
 	"sneak.berlin/go/webhooker/internal/logger"
-	"sneak.berlin/go/webhooker/internal/metrics"
 	"sneak.berlin/go/webhooker/internal/middleware"
 	"sneak.berlin/go/webhooker/internal/session"
 )
@@ -110,8 +109,6 @@ func newTestApp(
 			func(r *recordingEvictor) delivery.WebhookEvictor {
 				return r
 			},
-			metrics.NewRegistry,
-			metrics.New,
 			middleware.New,
 			delivery.NewGuard,
 			handlers.New,
@@ -1,20 +0,0 @@
-package handlers
-
-import (
-	"net/http"
-
-	"github.com/prometheus/client_golang/prometheus/promhttp"
-)
-
-// HandleMetrics returns the Prometheus scrape handler for the
-// registry every collector in this process registers on. It is what
-// promhttp.Handler builds for the global default registry, including
-// the promhttp_metric_handler_* series that count scrapes, pointed at
-// that registry instead.
-func (s *Handlers) HandleMetrics() http.HandlerFunc {
-	reg := s.params.Registry
-
-	return promhttp.InstrumentMetricHandler(
-		reg, promhttp.HandlerFor(reg, promhttp.HandlerOpts{}),
-	).ServeHTTP
-}
@@ -3,17 +3,17 @@
 // deliveries are attempted, how they end, how long they take, how
 // deep the queues are, and how many circuit breakers are open.
 //
-// It also builds the registry the authenticated /metrics route
-// serves. These collectors, the inbound HTTP metrics recorded in
-// internal/middleware, and the Go runtime and process collectors all
-// register on that one registry, never on Prometheus's global default.
+// The inbound HTTP metrics come from the go-http-metrics recorder in
+// internal/middleware and land on prometheus.DefaultRegisterer. These
+// collectors register there too, so both surfaces are gathered by the
+// one promhttp handler mounted on the authenticated /metrics route.
 package metrics

 import (
+	"sync"
 	"time"

 	"github.com/prometheus/client_golang/prometheus"
-	"github.com/prometheus/client_golang/prometheus/collectors"
 	"github.com/prometheus/client_golang/prometheus/promauto"
 	"sneak.berlin/go/webhooker/internal/database"
 )
@@ -57,31 +57,25 @@ var knownTargetTypes = []database.TargetType{
 	database.TargetTypeSlack,
 }

-// NewRegistry returns the registry /metrics serves, carrying the Go
-// runtime and process collectors that Prometheus's global default
-// registry carries, so the go_* and process_* series stay in the
-// scrape.
+// defaultSet is the process-wide metric set, registered on the same
+// registry the HTTP middleware and the /metrics handler already use.
+// It is built on first use rather than in an init so that a test
+// binary that never touches metrics never registers them.
 //
-// A registry of its own, rather than the global default, is what lets
-// two dependency graphs in one process — two tests, say — each
-// register their collectors without the second registration
-// panicking.
-func NewRegistry() *prometheus.Registry {
-	reg := prometheus.NewRegistry()
-	reg.MustRegister(
-		collectors.NewGoCollector(),
-		collectors.NewProcessCollector(
-			collectors.ProcessCollectorOpts{},
-		),
-	)
+//nolint:gochecknoglobals // one process-wide registration, by design
+var defaultSet = sync.OnceValue(func() *Set {
+	return New(prometheus.DefaultRegisterer)
+})

-	return reg
+// Default returns the process-wide metric set.
+func Default() *Set {
+	return defaultSet()
 }

 // Set is one registered group of webhooker's delivery collectors.
-// Production builds one on the registry /metrics serves; tests build
-// their own against a private registry so assertions are not
-// disturbed by deliveries other tests are making concurrently.
+// Production uses the single Default set; tests build their own
+// against a private registry so assertions are not disturbed by
+// deliveries other tests are making concurrently.
 type Set struct {
 	eventsReceived      prometheus.Counter
 	deliveryAttempts    *prometheus.CounterVec
@@ -99,7 +93,7 @@ type Set struct {
 // New registers a full set of delivery collectors on reg and returns
 // it. It panics if reg already holds them, which is the intended
 // behaviour for a duplicate registration.
-func New(reg *prometheus.Registry) *Set {
+func New(reg prometheus.Registerer) *Set {
 	factory := promauto.With(reg)

 	s := &Set{
@@ -10,7 +10,8 @@ import (

 // MetricsMiddlewareForTest builds the metrics recording middleware
 // against a caller-supplied recorder, so a test can gather from its
-// own Prometheus registry without building a whole Middleware.
+// own Prometheus registry rather than the process-wide default one
+// that Middleware.Metrics uses.
 func MetricsMiddlewareForTest(
 	rec httpmetrics.Recorder,
 ) func(http.Handler) http.Handler {
@@ -108,10 +108,10 @@ type failureWindow struct {
 //
 // A limiter that spends budget on arrival cannot protect a
 // single-admin product: behind the reverse proxy the deployment
-// requires, with TRUSTED_PROXIES unset, every client keys on the
-// proxy, so a stranger trickling five POSTs a minute keeps the one
-// bucket full and the operator's own correct password is answered 429
-// forever. There is no second administrative path.
+// requires, when TRUSTED_PROXIES does not cover it, every client
+// keys on the proxy, so a stranger trickling five POSTs a minute
+// keeps the one bucket full and the operator's own correct password
+// is answered 429 forever. There is no second administrative path.
 //
 // So budget is spent only by a FAILED verification. A correct
 // password is never throttled, whatever the counters say, which is
@@ -7,6 +7,7 @@ import (

 	"github.com/go-chi/chi"
 	httpmetrics "github.com/slok/go-http-metrics/metrics"
+	prommetrics "github.com/slok/go-http-metrics/metrics/prometheus"
 	ghmm "github.com/slok/go-http-metrics/middleware"
 	"github.com/slok/go-http-metrics/middleware/std"
 )
@@ -151,14 +152,16 @@ func (r boundedLabelRecorder) AddInflightRequests(
 var _ httpmetrics.Recorder = boundedLabelRecorder{}

 // Metrics returns middleware that records Prometheus HTTP metrics on
-// the registry the /metrics route serves. Every call shares the one
-// recorder New built, so any number of routers can install it.
+// the default registry, which is the one the /metrics route gathers.
 func (s *Middleware) Metrics() func(http.Handler) http.Handler {
-	return metricsMiddleware(s.metricsRecorder)
+	return metricsMiddleware(
+		prommetrics.NewRecorder(prommetrics.Config{}),
+	)
 }

 // metricsMiddleware builds the recording middleware against a given
-// recorder, so tests can gather from a registry of their own.
+// recorder, so tests can gather from a registry of their own instead
+// of the process-wide default.
 func metricsMiddleware(
 	rec httpmetrics.Recorder,
 ) func(http.Handler) http.Handler {
@@ -57,8 +57,9 @@ const (
 // Server.setupWebhookRoutes inside it. That ordering is the whole
 // defect, so a test that flattens it would prove nothing.
 //
-// The recorder writes to a registry of the test's own, so each test
-// observes only its own traffic.
+// The recorder writes to a registry of the test's own rather than the
+// process-wide default one, so each test observes only its own
+// traffic.
 func metricsTestRouter(
 	t *testing.T,
 	receiverLimit int,
@@ -13,9 +13,6 @@ import (
 	"github.com/go-chi/chi"
 	"github.com/go-chi/chi/middleware"
 	"github.com/go-chi/cors"
-	"github.com/prometheus/client_golang/prometheus"
-	httpmetrics "github.com/slok/go-http-metrics/metrics"
-	prommetrics "github.com/slok/go-http-metrics/metrics/prometheus"
 	"go.uber.org/fx"
 	"sneak.berlin/go/webhooker/internal/config"
 	"sneak.berlin/go/webhooker/internal/globals"
@@ -151,11 +148,10 @@ const (
 type MiddlewareParams struct {
 	fx.In

-	Logger   *logger.Logger
-	Globals  *globals.Globals
-	Config   *config.Config
-	Session  *session.Session
-	Registry *prometheus.Registry
+	Logger  *logger.Logger
+	Globals *globals.Globals
+	Config  *config.Config
+	Session *session.Session
 }

 // Middleware provides HTTP middleware for logging, CORS, auth, and
@@ -165,12 +161,6 @@ type Middleware struct {
 	params  *MiddlewareParams
 	session *session.Session

-	// metricsRecorder records the inbound HTTP metrics on the
-	// registry /metrics serves. It is built once, in New, because
-	// building it registers its collectors, and a second
-	// registration on the same registry panics; see Metrics.
-	metricsRecorder httpmetrics.Recorder
-
 	// loginGuard counts failed credential verifications and bounds
 	// concurrent password hashing. It is built on first use so that
 	// every construction path gets one; see guard().
@@ -189,9 +179,6 @@ func New(
 	s.params = &params
 	s.log = params.Logger.Get()
 	s.session = params.Session
-	s.metricsRecorder = prommetrics.NewRecorder(
-		prommetrics.Config{Registry: params.Registry},
-	)

 	return s, nil
 }
@@ -123,9 +123,8 @@ func bucketKey(addr netip.Addr) string {
 	return prefix.String()
 }

-// isTrustedProxy reports whether addr belongs to a network the
-// operator listed in TRUSTED_PROXIES. The list is empty by default,
-// so by default nothing is trusted.
+// isTrustedProxy reports whether addr belongs to a network in
+// TRUSTED_PROXIES, which by default is the RFC 1918 private ranges.
 func (m *Middleware) isTrustedProxy(addr netip.Addr) bool {
 	for _, prefix := range m.params.Config.TrustedProxies {
 		if prefix.Contains(addr) {
@@ -426,8 +426,8 @@ func assertSharedBucket(
 }

 // TestRateLimitKey_SpoofedForwardedFromUntrustedPeer is the test
-// this gating exists for: with no trusted proxies configured (the
-// default), a client that rotates a forwarded header on every
+// this gating exists for: from a peer that is not a trusted
+// proxy, a client that rotates a forwarded header on every
 // request must stay in one bucket. If forwarded headers were
 // trusted unconditionally, each spoofed value would mint a fresh
 // bucket and the limit would stop no one.
@@ -24,7 +24,6 @@ import (
 	"sneak.berlin/go/webhooker/internal/handlers"
 	"sneak.berlin/go/webhooker/internal/healthcheck"
 	"sneak.berlin/go/webhooker/internal/logger"
-	"sneak.berlin/go/webhooker/internal/metrics"
 	"sneak.berlin/go/webhooker/internal/middleware"
 	"sneak.berlin/go/webhooker/internal/resetpw"
 	"sneak.berlin/go/webhooker/internal/session"
@@ -164,8 +163,6 @@ func newServerApp(
 			session.New,
 			func() delivery.Notifier { return &noopNotifier{} },
 			func() delivery.WebhookEvictor { return &noopEvictor{} },
-			metrics.NewRegistry,
-			metrics.New,
 			middleware.New,
 			delivery.NewGuard,
 			handlers.New,
@@ -7,6 +7,7 @@ import (
 	sentryhttp "github.com/getsentry/sentry-go/http"
 	"github.com/go-chi/chi"
 	"github.com/go-chi/chi/middleware"
+	"github.com/prometheus/client_golang/prometheus/promhttp"
 	"sneak.berlin/go/webhooker/static"
 )

@@ -91,25 +92,11 @@ func (s *Server) setupGlobalMiddleware() {
 func (s *Server) setupRoutes() {
 	s.router.Get("/", s.h.HandleIndex())

-	// Static assets answer GET and HEAD only. chi's default 405
-	// carries no Allow header, so this group supplies its own.
-	staticFiles := http.StripPrefix(
-		"/s", http.FileServer(http.FS(static.Static)),
+	s.router.Mount(
+		"/s",
+		http.StripPrefix("/s", http.FileServer(http.FS(static.Static))),
 	)

-	s.router.Route("/s", func(r chi.Router) {
-		r.MethodNotAllowed(func(w http.ResponseWriter, _ *http.Request) {
-			w.Header().Set("Allow", "GET, HEAD")
-			http.Error(
-				w,
-				"Method Not Allowed",
-				http.StatusMethodNotAllowed,
-			)
-		})
-		r.Method(http.MethodGet, "/*", staticFiles)
-		r.Method(http.MethodHead, "/*", staticFiles)
-	})
-
 	s.router.Route("/api/v1", func(_ chi.Router) {
 		// API routes will be added here.
 	})
@@ -129,7 +116,12 @@ func (s *Server) setupRoutes() {
 	if s.params.Config.MetricsAuthEnabled() {
 		s.router.Group(func(r chi.Router) {
 			r.Use(s.mw.MetricsAuth())
-			r.Get("/metrics", s.h.HandleMetrics())
+			r.Get(
+				"/metrics",
+				http.HandlerFunc(
+					promhttp.Handler().ServeHTTP,
+				),
+			)
 		})
 	}

@@ -148,11 +140,12 @@ func (s *Server) setupPageRoutes() {
 		r.Use(s.mw.NoCache())

 		// The login POST carries no pre-emptive rate limiter. Behind
-		// the reverse proxy production requires, with TRUSTED_PROXIES
-		// unset, every client shares one bucket, so a limiter spent
-		// on arrival lets any stranger deny the operator the only
-		// administrative path. The handler verifies credentials first
-		// and charges only failures; see Handlers.authenticateUser.
+		// the reverse proxy production requires, when TRUSTED_PROXIES
+		// does not cover it, every client shares one bucket, so a
+		// limiter spent on arrival lets any stranger deny the operator
+		// the only administrative path. The handler verifies
+		// credentials first and charges only failures; see
+		// Handlers.authenticateUser.
 		r.Get("/login", s.h.HandleLoginPage())
 		r.Post("/login", s.h.HandleLoginSubmit())

@@ -23,7 +23,6 @@ import (
 	"sneak.berlin/go/webhooker/internal/handlers"
 	"sneak.berlin/go/webhooker/internal/healthcheck"
 	"sneak.berlin/go/webhooker/internal/logger"
-	"sneak.berlin/go/webhooker/internal/metrics"
 	"sneak.berlin/go/webhooker/internal/middleware"
 	"sneak.berlin/go/webhooker/internal/server"
 	"sneak.berlin/go/webhooker/internal/session"
@@ -113,8 +112,6 @@ func newTestEnvWithConfig(
 			session.New,
 			func() delivery.Notifier { return &noopNotifier{} },
 			func() delivery.WebhookEvictor { return &noopEvictor{} },
-			metrics.NewRegistry,
-			metrics.New,
 			middleware.New,
 			delivery.NewGuard,
 			handlers.New,
@@ -399,15 +396,13 @@ func (e *testEnv) storedHash(t *testing.T, username string) string {

 // --- /s static group ---

-// TestStaticServesOnlyGetAndHead pins the methods the static group
-// answers: GET and HEAD are served the asset, and the other methods
-// chi routes (POST, PUT, DELETE and the rest) are refused with 405
-// and an Allow header naming those two. A method chi does not route,
-// such as PROPFIND, is refused with 405 by the top-level router
-// before it reaches the static group, so it gets no Allow header.
-// The README documents this; the test is what keeps the two from
-// drifting.
-func TestStaticServesOnlyGetAndHead(t *testing.T) {
+// TestStaticServesEveryMethod pins what the static mount actually
+// answers. chi's Mount registers the handler for all methods and
+// http.FileServer only special-cases HEAD (by suppressing the body),
+// so a POST or a DELETE to an asset is served the file rather than
+// refused. The README documents this; the test is what keeps the two
+// from drifting.
+func TestStaticServesEveryMethod(t *testing.T) {
 	t.Parallel()

 	env := newTestEnv(t)
@@ -422,7 +417,6 @@ func TestStaticServesOnlyGetAndHead(t *testing.T) {
 		http.MethodPost,
 		http.MethodPut,
 		http.MethodDelete,
-		"PROPFIND",
 	} {
 		t.Run(method, func(t *testing.T) {
 			t.Parallel()
@@ -434,38 +428,18 @@ func TestStaticServesOnlyGetAndHead(t *testing.T) {
 			w := httptest.NewRecorder()
 			env.router.ServeHTTP(w, req)

-			switch method {
-			case http.MethodGet:
-				assert.Equal(t, http.StatusOK, w.Code)
-				assert.Equal(t, body, w.Body.Bytes(),
-					"the asset itself is returned")
-			case http.MethodHead:
-				assert.Equal(t, http.StatusOK, w.Code)
+			assert.Equal(t, http.StatusOK, w.Code,
+				"static mount answers every method")
+
+			if method == http.MethodHead {
 				assert.Empty(t, w.Body.Bytes(),
 					"HEAD must not carry a body")
-			case "PROPFIND":
-				assert.Equal(
-					t, http.StatusMethodNotAllowed, w.Code,
-				)
-				assert.Empty(t, w.Header().Get("Allow"),
-					"chi refuses a method it does not route "+
-						"before the static group runs")
-				assert.NotContains(
-					t, w.Body.String(), string(body),
-					"a refused method must not get the asset",
-				)
-			default:
-				assert.Equal(
-					t, http.StatusMethodNotAllowed, w.Code,
-				)
-				assert.Equal(
-					t, "GET, HEAD", w.Header().Get("Allow"),
-				)
-				assert.NotContains(
-					t, w.Body.String(), string(body),
-					"a refused method must not get the asset",
-				)
+
+				return
 			}
+
+			assert.Equal(t, body, w.Body.Bytes(),
+				"the asset itself is returned")
 		})
 	}
 }
@@ -964,43 +938,3 @@ func TestMetricsRouteUnmountedOnHalfSetConfig(t *testing.T) {
 		})
 	}
 }
-
-// TestTwoMetricsRoutersInOneProcess pins
-// https://git.eeqj.de/sneak/webhooker/issues/227: a second
-// metrics-enabled router in one process used to panic, because the
-// HTTP metrics registered on Prometheus's global default registry.
-// Two routers are built over separate dependency graphs and a third
-// over the first graph again, and each must still serve the HTTP,
-// delivery and Go runtime series.
-func TestTwoMetricsRoutersInOneProcess(t *testing.T) {
-	t.Parallel()
-
-	first := newTestEnvWithConfig(
-		t, metricsConfig(t, metricsUser, metricsAuthValue),
-	)
-	second := newTestEnvWithConfig(
-		t, metricsConfig(t, metricsUser, metricsAuthValue),
-	)
-	third := &testEnv{
-		router: server.NewRouterForTest(
-			first.log.Get(), first.cfg, first.mw, first.hnd,
-		),
-	}
-
-	for _, env := range []*testEnv{first, second, third} {
-		env.get("/", nil)
-
-		scrape := env.metricsRequest(metricsUser, metricsAuthValue)
-		require.Equal(t, http.StatusOK, scrape.Code)
-
-		for _, series := range []string{
-			"http_request_duration_seconds",
-			"http_response_size_bytes",
-			"http_requests_inflight",
-			"webhooker_events_received_total",
-			"go_goroutines",
-		} {
-			assert.Contains(t, scrape.Body.String(), series)
-		}
-	}
-}