diff --git a/README.md b/README.md
index 319989c..c48aa4c 100644
--- a/README.md
+++ b/README.md
@@ -92,7 +92,8 @@ them at once. A variable already present in the real environment wins
 over the file's value for the same name.
 
 The environment is selected by setting `WEBHOOKER_ENVIRONMENT` to `dev`
-or `prod` (default: `dev`). The setting controls exactly one behavior:
+or `prod` (default: `prod`; `dev` must be set explicitly). The setting
+controls exactly one behavior:
 
 | Behavior | `dev`                   | `prod`           |
 | -------- | ----------------------- | ---------------- |
@@ -134,7 +135,7 @@ TTY detection, and security headers are always applied.
 
 | Variable                | Description                         | Default  |
 | ----------------------- | ----------------------------------- | -------- |
-| `WEBHOOKER_ENVIRONMENT` | `dev` or `prod`                     | `dev`    |
+| `WEBHOOKER_ENVIRONMENT` | `dev` or `prod`                     | `prod`   |
 | `PORT`                  | HTTP listen port                    | `8080`   |
 | `BIND_ADDRESS`          | IP address the HTTP listener binds. Loopback by default, so the cleartext listener is not published on every interface. The Docker image ships `0.0.0.0` instead. See [Bind address](#bind-address) | `127.0.0.1` (image: `0.0.0.0`) |
 | `DATA_DIR`              | Directory for all SQLite databases  | `/var/lib/webhooker` |
@@ -400,9 +401,9 @@ 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 —
-not only when `WEBHOOKER_ENVIRONMENT=prod`, because that variable
-defaults to `dev` and an operator who never set it is precisely the
-one at risk. The warning is informational when nothing proxies to the
+the warning does not depend on `WEBHOOKER_ENVIRONMENT`, because an
+operator who never configured the deployment is precisely the one at
+risk. 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.
@@ -754,15 +755,15 @@ reports.
    that.
 2. **Set `WEBHOOKER_ENVIRONMENT=prod`, and make sure the proxy sends
    `X-Forwarded-Proto`.** These are two requirements, not one. The
-   environment setting decides CORS and nothing else: the default
-   `dev` answers every origin with `Access-Control-Allow-Origin: *`
-   (without credentials), which a server-rendered production
-   deployment has no use for. Cookie `Secure` and the strict
-   Origin/Referer mode are **not** tied to it — they are decided per
-   request from the transport, which 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).
+   environment setting decides CORS and nothing else: `dev` answers
+   every origin with `Access-Control-Allow-Origin: *` (without
+   credentials), which a server-rendered production deployment has no
+   use for, and `prod` — the default — disables it. Cookie `Secure`
+   and the strict Origin/Referer mode are **not** tied to it — they
+   are decided per request from the transport, which 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
diff --git a/internal/config/config.go b/internal/config/config.go
index 6a7a628..0c09163 100644
--- a/internal/config/config.go
+++ b/internal/config/config.go
@@ -585,12 +585,14 @@ func resolveMetricsAuth() (string, string, error) {
 	)
 }
 
-// resolveEnvironment reads WEBHOOKER_ENVIRONMENT, defaulting to
-// dev, and rejects unrecognised values.
+// resolveEnvironment reads WEBHOOKER_ENVIRONMENT, defaulting to prod
+// when it is unset so a deployment that forgets the variable is not
+// silently permissive; dev must be set explicitly. It rejects
+// unrecognised values.
 func resolveEnvironment() (string, error) {
 	environment := os.Getenv("WEBHOOKER_ENVIRONMENT")
 	if environment == "" {
-		environment = EnvironmentDev
+		environment = EnvironmentProd
 	}
 
 	if environment != EnvironmentDev &&
@@ -772,10 +774,10 @@ func (c *Config) warnEgressAllowlist(log *slog.Logger) {
 // everyone else's wrong passwords, and the receiver's limits become
 // service-wide ceilings.
 //
-// The warning is deliberately not gated on WEBHOOKER_ENVIRONMENT. That
-// variable defaults to dev, so gating on it would silence the warning
-// for exactly the operator who forgot to configure the deployment —
-// the case it exists to catch.
+// The warning is deliberately not gated on WEBHOOKER_ENVIRONMENT: an
+// operator who never configured the deployment is exactly the case it
+// exists to catch, so the exposure it announces is independent of the
+// environment setting.
 //
 // The default of trusting nobody is deliberate — trusting forwarded
 // headers from arbitrary peers lets any client choose its own bucket —
diff --git a/internal/config/config_test.go b/internal/config/config_test.go
index f38f7fd..4c8850e 100644
--- a/internal/config/config_test.go
+++ b/internal/config/config_test.go
@@ -44,9 +44,9 @@ func TestEnvironmentConfig(t *testing.T) {
 		isProd      bool
 	}{
 		{
-			name:   "default is dev",
-			isDev:  true,
-			isProd: false,
+			name:   "default is prod",
+			isDev:  false,
+			isProd: true,
 		},
 		{
 			name:     "explicit dev",
@@ -848,10 +848,10 @@ func TestEgressAllowlistWarning(t *testing.T) {
 // 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: WEBHOOKER_ENVIRONMENT defaults to dev, so gating
-// on it would silence the warning for exactly the operator who never
-// configured the deployment. It stays quiet once proxies are named.
+// counting. It must fire whenever TRUSTED_PROXIES is empty, in any
+// environment: the warning does not depend on WEBHOOKER_ENVIRONMENT,
+// since an operator who never configured the deployment is exactly the
+// one it exists to catch. It stays quiet once proxies are named.
 func TestSharedRateLimitBucketWarning(t *testing.T) {
 	tests := []struct {
 		name           string
@@ -871,10 +871,9 @@ func TestSharedRateLimitBucketWarning(t *testing.T) {
 			expectWarning:  false,
 		},
 		{
-			// The default environment. An internet-exposed
-			// deployment whose operator never set
-			// WEBHOOKER_ENVIRONMENT lands here and has exactly
-			// the exposure the warning announces.
+			// An internet-exposed deployment whose operator set
+			// WEBHOOKER_ENVIRONMENT=dev has exactly the exposure
+			// the warning announces.
 			name:          "dev without trusted proxies warns",
 			environment:   config.EnvironmentDev,
 			expectWarning: true,
diff --git a/internal/middleware/csrf_test.go b/internal/middleware/csrf_test.go
index 4273964..f1660ed 100644
--- a/internal/middleware/csrf_test.go
+++ b/internal/middleware/csrf_test.go
@@ -380,9 +380,8 @@ func csrfTookStrictPath(
 
 // TestCSRF_ForwardedProtoSpellingsTakeStrictPath runs the header
 // spellings a real proxy emits through the middleware. The environment
-// is dev -- the DEFAULT when WEBHOOKER_ENVIRONMENT is unset -- to pin
-// that the routing is a per-request transport decision and owes
-// nothing to configuration.
+// is set to dev -- the permissive setting -- to pin that the routing is
+// a per-request transport decision and owes nothing to configuration.
 func TestCSRF_ForwardedProtoSpellingsTakeStrictPath(t *testing.T) {
 	t.Parallel()