diff --git a/.env.example b/.env.example
index 51e1e246..65362425 100644
--- a/.env.example
+++ b/.env.example
@@ -158,8 +158,11 @@ AGENT_COMPUTER_URL=http://localhost:4100
 # without this value and refuses every request that does not present it. Use a long random value;
 # `scripts/start.sh` sets a development one for you.
 COMPUTER_TOKEN=
-# Local only. Lets a Bot browse this machine's own services; never set this in a deployment.
-AGENT_COMPUTER_ALLOW_PRIVATE_HOSTS=true
+# Local only, and commented out because this file gets copied. Uncommenting it lets a Bot browse this
+# machine's own services, which is what a laptop wants and what a deployment must never have: it
+# lifts the private-address floor in browsing and in the endpoint a Bot may be registered against.
+# The server refuses to start with it set under NODE_ENV=production.
+# AGENT_COMPUTER_ALLOW_PRIVATE_HOSTS=true
 #
 # What a Bot may do on its computer, as one JSON object. Absent uses the built-in default, which
 # permits the acting tools and forbids nothing, and records every action either way.
diff --git a/CHANGELOG.md b/CHANGELOG.md
index 4a0f9206..482f9e54 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -8,6 +8,37 @@ Newest first. `Unreleased` is what is on `main` and not yet tagged.
 
 ## Unreleased
 
+### Upgrading
+
+**A deployment that sets `AGENT_COMPUTER_ALLOW_PRIVATE_HOSTS=true` with `NODE_ENV=production` no
+longer starts.** Remove the line and it starts again. Nothing else needs changing, and a deployment
+that never set it is unaffected.
+
+The switch lets a Bot reach addresses inside the deployment's own network — `10.0.0.5`,
+`192.168.1.1`, `127.0.0.1:5432`, a link-local address — and it does that in two places, not one:
+browsing, and the endpoint a Bot may be registered against. It exists for a laptop, where the
+services a Bot is asked to look at are the ones running beside it.
+
+The reason this is a refusal rather than a warning is how a deployment came to have it. `.env.example`
+shipped the line on, and copying that file is the ordinary way an environment gets filled in, so the
+path to a hosted deployment reaching its own network was not forgetting to set something, it was
+inheriting something. It now ships commented out, which means a laptop that wants the old behaviour
+uncomments it and everything else arrives without it. Under any other `NODE_ENV` the switch works
+exactly as before, with a warning at boot saying it does not travel.
+
+**The one-container image shipped with the switch on, and no longer does.** It set both
+`AGENT_COMPUTER_ALLOW_PRIVATE_HOSTS=true` and `NODE_ENV=production`, so the image really did run
+with private-host browsing enabled. Two things that worked there stop: a Bot browsing a private
+address such as an intranet page, and registering a coworker at a private endpoint like
+`http://10.0.0.20:8000/ag-ui`. Because the image bakes in `NODE_ENV=production`, there is no
+override — a deployment that needs either of those wants the compose setup or its own image rather
+than the all-in-one. The image continues to start, and everything else in it is unchanged.
+
+The cloud metadata addresses — `169.254.169.254`, `metadata.google.internal`, and the IPv6 and
+NAT64 spellings of them — were refused whatever this switch said, before and after. That floor has
+not moved. What changed is that it is no longer the only thing left standing in a production
+deployment that copied the example.
+
 ## 0.0.4
 
 ### A click citing a ref this deployment cannot resolve is refused
diff --git a/Dockerfile b/Dockerfile
index 105ff461..674ce392 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -173,10 +173,15 @@ RUN apt-get update && apt-get install -y --no-install-recommends sudo \
 ENV WORKSPACE_DIR=/workspace
 ENV PROFILES_DIR=/profiles
 
-# The browser is on loopback inside this container and reachable from nowhere else, which is why the
-# private-host allowance is on: the server is browsing to its own sibling process, not the internet.
+# The browser is on loopback inside this container and reachable from nowhere else.
+#
+# No private-host allowance is set for it, and none is needed. Reaching the sibling process goes
+# through `checkComputerAddress`, which decides on the protocol and the metadata floor and never
+# consults `AGENT_COMPUTER_ALLOW_PRIVATE_HOSTS`. That switch governs where a *Bot* may browse and
+# which endpoint one may be registered against, so setting it here bought nothing for this address
+# and let a Bot reach whatever this container's network reaches, which on a default bridge is the
+# host's LAN.
 ENV AGENT_COMPUTER_URL=http://127.0.0.1:4100
-ENV AGENT_COMPUTER_ALLOW_PRIVATE_HOSTS=true
 
 # NOTHING THAT MATTERS RUNS AS ROOT.
 #
diff --git a/README.md b/README.md
index f028234b..c57b4af8 100644
--- a/README.md
+++ b/README.md
@@ -202,7 +202,7 @@ Settings worth knowing:
 | `COMPUTER_SANDBOX`                   | Set to `on` for Chromium's own sandbox, where the host permits it.        |
 | `EMBEDDED_POSTGRES`                  | Set to `on` for a database inside the deployment container.               |
 | `AGENT_COMPUTER_POLICY`              | JSON action policy. Malformed JSON stops server startup.                  |
-| `AGENT_COMPUTER_ALLOW_PRIVATE_HOSTS` | Lets a Bot reach this machine's own services.                             |
+| `AGENT_COMPUTER_ALLOW_PRIVATE_HOSTS` | Lets a Bot reach this machine's own services. Local only, and refused under `NODE_ENV=production`. |
 | `TENANT_PACKAGE_DIR`                 | Directory containing tenant YAML. Defaults to `../examples/fintech`.      |
 | `DEPLOYMENT_ID`                      | Names this deployment when two share one Intelligence project.            |
 
@@ -291,7 +291,7 @@ provider's discovery document listed in `TRUSTED_ORIGINS`, not only the issuer.
 
 - `agent-computer` drives a browser holding real logins. `docker-compose.yml` binds it to loopback; leave it there.
 - Store credentials through `/admin/credentials`, which encrypts them. Do not put credential values in tenant YAML or in committed files.
-- `AGENT_COMPUTER_ALLOW_PRIVATE_HOSTS` lets a Bot reach services on this machine. Unset it if you would rather it could not.
+- `AGENT_COMPUTER_ALLOW_PRIVATE_HOSTS` lets a Bot reach services on this machine. It ships commented out in `.env.example`, is for a laptop only, and a deployment running with `NODE_ENV=production` refuses to start while it is set.
 
 ## Development
 
diff --git a/docs/architecture.md b/docs/architecture.md
index f3a1d9c3..6751e95f 100644
--- a/docs/architecture.md
+++ b/docs/architecture.md
@@ -182,5 +182,5 @@ Connector credentials are stored through the credential vault and referenced by
 - `KEY_ENCRYPTION_KEY` must be a base64-encoded 32-byte value. The example key is refused with `NODE_ENV=production`.
 - Credential plaintext is encrypted at rest, never returned by APIs, and redacted from audit events.
 - Browser navigation allows `http` and `https`; cloud metadata addresses are refused under every configuration.
-- `AGENT_COMPUTER_ALLOW_PRIVATE_HOSTS=true` is for local development only.
+- `AGENT_COMPUTER_ALLOW_PRIVATE_HOSTS=true` is for local development only, and a deployment running with `NODE_ENV=production` refuses to start while it is set.
 - Computer tokens and supervisor tokens must be long random values outside local development.
diff --git a/docs/configuration.md b/docs/configuration.md
index a617f6fc..4a54392d 100644
--- a/docs/configuration.md
+++ b/docs/configuration.md
@@ -178,7 +178,7 @@ where `<provider>` is `google`, `microsoft` or `okta`.
 | `COMPUTER_BROWSER_IDLE_MS`           | How long an untouched browser is kept. 30 minutes by default; `0` keeps them resident.    |
 | `COMPUTER_SUPERVISOR_URL`            | Supervisor URL for per-Bot computers. If absent, Bots share `AGENT_COMPUTER_URL`.         |
 | `SUPERVISOR_TOKEN`                   | Bearer token required by the supervisor.                                                  |
-| `AGENT_COMPUTER_ALLOW_PRIVATE_HOSTS` | Local-only private-host browsing when `true`. Cloud metadata addresses are still refused. |
+| `AGENT_COMPUTER_ALLOW_PRIVATE_HOSTS` | Local-only private-host browsing when `true`. A deployment running with `NODE_ENV=production` refuses to start while it is set. Cloud metadata addresses are refused either way. |
 | `AGENT_COMPUTER_POLICY`              | JSON action policy: `{"mode":"enforce","deny":[...],"allow":[...]}`.                      |
 | `COMPUTER_RUNTIME`                   | Set to `runsc` to run supervised computers under gVisor.                                  |
 | `COMPUTER_SANDBOX`                   | Set to `on` to enable Chromium's own sandbox where the host permits user namespaces. Which way it went is printed at start-up. |
diff --git a/server/src/config.ts b/server/src/config.ts
index e9e7339d..ef04eafe 100644
--- a/server/src/config.ts
+++ b/server/src/config.ts
@@ -480,6 +480,38 @@ function runtimeCapabilities(environment: Environment): RuntimeCapabilities {
   };
 }
 
+/**
+ * Whether a Bot may reach addresses inside this deployment's own network.
+ *
+ * Off unless asked for, and the asking is only allowed on a laptop. The switch exists so that a
+ * local deployment can browse the services running beside it; what it turns off is not one rule but
+ * the whole private-address floor, in navigation and in the endpoint a Bot may be registered
+ * against, so with it on a signed-in person can point a Bot at a link-local address.
+ *
+ * Refused in production for the reason the example encryption key is: the way a deployment ends up
+ * with it is not forgetting to set something, it is copying `.env.example`, which shipped it on. The
+ * cloud metadata addresses are refused underneath this either way — see `computer/target.ts` — but
+ * that floor is the last one, not the only one worth keeping.
+ */
+function privateHostsAllowed(environment: Environment): boolean {
+  if (optional(environment, "AGENT_COMPUTER_ALLOW_PRIVATE_HOSTS") !== "true") {
+    return false;
+  }
+
+  // Through `optional`, so the comparison trims. Read raw, `NODE_ENV="production "` out of an env
+  // file would slip past a gate that the switch beside it, which does trim, would still trip.
+  if (optional(environment, "NODE_ENV") === "production") {
+    throw new Error(
+      "AGENT_COMPUTER_ALLOW_PRIVATE_HOSTS=true is for local development only: it lets a Bot reach this deployment's own network. Remove it from this deployment's environment.",
+    );
+  }
+  console.warn(
+    "AGENT_COMPUTER_ALLOW_PRIVATE_HOSTS=true lets a Bot reach this machine's own services. Fine locally, and for local development only. Remove it before deploying.",
+  );
+
+  return true;
+}
+
 function computerConfig(environment: Environment): ComputerConfig | undefined {
   const supervisorAddress = optional(environment, "COMPUTER_SUPERVISOR_URL");
   const sharedAddress = optional(environment, "AGENT_COMPUTER_URL");
@@ -494,8 +526,7 @@ function computerConfig(environment: Environment): ComputerConfig | undefined {
    */
   const computerToken = optional(environment, "COMPUTER_TOKEN");
 
-  const allowPrivateHosts =
-    optional(environment, "AGENT_COMPUTER_ALLOW_PRIVATE_HOSTS") === "true";
+  const allowPrivateHosts = privateHostsAllowed(environment);
   const policy = actionPolicy(environment);
 
   const supervisorUrl = url(environment, "COMPUTER_SUPERVISOR_URL");
diff --git a/server/tests/config.test.ts b/server/tests/config.test.ts
index 9deec2fa..d41e45dc 100644
--- a/server/tests/config.test.ts
+++ b/server/tests/config.test.ts
@@ -1,4 +1,5 @@
-import { describe, expect, test } from "bun:test";
+import { readFileSync } from "node:fs";
+import { describe, expect, spyOn, test } from "bun:test";
 import { configuredAuthProviders, loadConfig } from "../src/config";
 
 // Intelligence is part of the MINIMUM contract, so it belongs in the base environment every other
@@ -27,6 +28,19 @@ const baseEnvironment = {
  * The provider tests need the opposite starting point, or "Microsoft is configured" cannot be told
  * apart from "Microsoft and the Google that was already there".
  */
+/**
+ * A deployment that is actually deployed.
+ *
+ * `baseEnvironment` carries the example encryption key, which is refused under
+ * `NODE_ENV=production` — so a production case built on it fails on the key before it reaches
+ * whatever it meant to test. A real key here keeps each production test about its own subject.
+ */
+const productionEnvironment = {
+  ...baseEnvironment,
+  NODE_ENV: "production",
+  KEY_ENCRYPTION_KEY: "b3BlbmJvdC1wcm9kdWN0aW9uLXRlc3Qta2V5LTMyMzI=",
+};
+
 const {
   GOOGLE_OAUTH_CLIENT_ID: _googleId,
   GOOGLE_OAUTH_CLIENT_SECRET: _googleSecret,
@@ -418,6 +432,127 @@ describe("deployment configuration", () => {
     expect(loadConfig(baseEnvironment).computer).toBeUndefined();
   });
 
+  // `.env.example` used to ship AGENT_COMPUTER_ALLOW_PRIVATE_HOSTS=true, and copying that file is the
+  // ordinary way a deployment gets its environment. So the way a hosted deployment ends up reaching
+  // its own network is not forgetting to set something, it is inheriting something. Refused in
+  // production for the same reason the example encryption key is: convenient locally, and an opening
+  // anywhere else.
+  test("refuses to start when a production deployment allows private hosts", () => {
+    expect(() =>
+      loadConfig({
+        ...productionEnvironment,
+        AGENT_COMPUTER_URL: "http://localhost:4100",
+        AGENT_COMPUTER_ALLOW_PRIVATE_HOSTS: "true",
+      }),
+    ).toThrow("AGENT_COMPUTER_ALLOW_PRIVATE_HOSTS");
+  });
+
+  // Both sides of the comparison come out of the same env file, and the switch is read through
+  // `optional`, which trims. Comparing NODE_ENV raw would mean a trailing space typed into that file
+  // slipped past the refusal while the switch beside it still counted as set.
+  test("refuses a production deployment whose NODE_ENV carries whitespace", () => {
+    expect(() =>
+      loadConfig({
+        ...productionEnvironment,
+        NODE_ENV: "production ",
+        AGENT_COMPUTER_URL: "http://localhost:4100",
+        AGENT_COMPUTER_ALLOW_PRIVATE_HOSTS: "true",
+      }),
+    ).toThrow("AGENT_COMPUTER_ALLOW_PRIVATE_HOSTS");
+  });
+
+  // The refusal has to name the way out, because the person reading it at boot is looking at a file
+  // they copied and does not necessarily know which line is the problem.
+  test("says to remove the line, and that it is local only", () => {
+    const attempt = () =>
+      loadConfig({
+        ...productionEnvironment,
+        AGENT_COMPUTER_URL: "http://localhost:4100",
+        AGENT_COMPUTER_ALLOW_PRIVATE_HOSTS: "true",
+      });
+
+    expect(attempt).toThrow("local development only");
+    expect(attempt).toThrow("Remove it");
+  });
+
+  // The half of the matrix that was always right and has to stay right: absent means off, including
+  // in the environment where the new refusal lives.
+  test("starts in production when nothing asked for private hosts", () => {
+    const config = loadConfig({
+      ...productionEnvironment,
+      AGENT_COMPUTER_URL: "http://localhost:4100",
+      COMPUTER_TOKEN: "computer-token",
+    });
+
+    expect(config.computer?.allowPrivateHosts).toBe(false);
+  });
+
+  // The local workflow is the reason the flag exists, so outside production it still does exactly
+  // what it did. Warned about, because a laptop is where a deployment is configured and the warning
+  // is the only chance to say this line does not travel.
+  test.each(["development", undefined])(
+    "warns and still allows private hosts under NODE_ENV=%p",
+    (nodeEnv) => {
+      const consoleWarn = spyOn(console, "warn").mockImplementation(() => {});
+
+      try {
+        const config = loadConfig({
+          ...baseEnvironment,
+          ...(nodeEnv ? { NODE_ENV: nodeEnv } : {}),
+          AGENT_COMPUTER_URL: "http://localhost:4100",
+          AGENT_COMPUTER_ALLOW_PRIVATE_HOSTS: "true",
+        });
+
+        expect(config.computer?.allowPrivateHosts).toBe(true);
+        // Searched rather than indexed: `baseEnvironment` carries the example encryption key, which
+        // warns on its own account first.
+        const warning = consoleWarn.mock.calls
+          .map(([first]) => String(first))
+          .find((line) => line.includes("AGENT_COMPUTER_ALLOW_PRIVATE_HOSTS"));
+
+        expect(warning).toBeDefined();
+        expect(warning).toContain("local development only");
+        expect(warning).toContain("Remove it before deploying");
+      } finally {
+        consoleWarn.mockRestore();
+      }
+    },
+  );
+
+  // The refusal above only helps a deployment that reads it. The reason there was anything to refuse
+  // is that the file everybody copies arrived with the switch on, so the file is worth asserting
+  // about directly: a live line here is the regression, whatever the code does afterwards.
+  test("the shipped example does not turn private hosts on", () => {
+    const example = readFileSync(
+      new URL("../../.env.example", import.meta.url),
+      "utf8",
+    );
+
+    // Commented-out mentions are wanted — that is how the switch stays discoverable for a laptop.
+    const live = example
+      .split("\n")
+      .filter((line) =>
+        /^\s*AGENT_COMPUTER_ALLOW_PRIVATE_HOSTS\s*=/.test(line),
+      );
+
+    expect(live).toEqual([]);
+  });
+
+  // Anything that is not the exact opt-in is not an opt-in, so it is not the thing being refused
+  // either. A deployment that wrote something else has private hosts off and starts.
+  test.each(["false", "1", "yes", ""])(
+    "starts in production on AGENT_COMPUTER_ALLOW_PRIVATE_HOSTS=%p",
+    (value) => {
+      const config = loadConfig({
+        ...productionEnvironment,
+        AGENT_COMPUTER_URL: "http://localhost:4100",
+        AGENT_COMPUTER_ALLOW_PRIVATE_HOSTS: value,
+      });
+
+      expect(config.computer?.allowPrivateHosts).toBe(false);
+    },
+  );
+
   test.each([
     ["Docker", "COMPUTER_SUPERVISOR_URL"],
     ["shared", "AGENT_COMPUTER_URL"],