diff --git a/.github/workflows/publish.yml b/.github/workflows/publish.yml
index d1f8834..05b65d2 100644
--- a/.github/workflows/publish.yml
+++ b/.github/workflows/publish.yml
@@ -104,8 +104,7 @@ jobs:
           import { writeFileSync } from 'node:fs';
 
           const token = process.env.POSTHOG_PROJECT_TOKEN?.trim() || '';
-          const host =
-            process.env.POSTHOG_HOST?.trim() || 'https://us.i.posthog.com';
+          const host = process.env.POSTHOG_HOST?.trim() || '';
           const source = [
             '/** Generated in the release workspace by publish.yml. */',
             `export const BUILT_IN_POSTHOG_PROJECT_TOKEN = ${JSON.stringify(token)};`,
diff --git a/src/telemetry-build-config.ts b/src/telemetry-build-config.ts
index cd90435..76369a8 100644
--- a/src/telemetry-build-config.ts
+++ b/src/telemetry-build-config.ts
@@ -3,4 +3,4 @@
  * the plugin bundle is built. Local and source builds keep telemetry disabled.
  */
 export const BUILT_IN_POSTHOG_PROJECT_TOKEN = '';
-export const BUILT_IN_POSTHOG_HOST = 'https://us.i.posthog.com';
+export const BUILT_IN_POSTHOG_HOST = '';
diff --git a/src/telemetry.ts b/src/telemetry.ts
index a7248b0..cb1f547 100644
--- a/src/telemetry.ts
+++ b/src/telemetry.ts
@@ -10,9 +10,7 @@ import {
 
 const DEFAULT_POSTHOG_HOST = 'https://us.i.posthog.com';
 const POSTHOG_PROJECT_TOKEN =
-  process.env.POSTHOG_PROJECT_TOKEN ||
-  process.env.POSTHOG_API_KEY ||
-  BUILT_IN_POSTHOG_PROJECT_TOKEN;
+  process.env.POSTHOG_PROJECT_TOKEN || BUILT_IN_POSTHOG_PROJECT_TOKEN;
 const POSTHOG_HOST =
   process.env.POSTHOG_HOST || BUILT_IN_POSTHOG_HOST || DEFAULT_POSTHOG_HOST;
 
diff --git a/test/plugin-package.test.ts b/test/plugin-package.test.ts
index b84e475..6533d73 100644
--- a/test/plugin-package.test.ts
+++ b/test/plugin-package.test.ts
@@ -182,6 +182,35 @@ test('releases the root plugin package with plugin-specific artifacts', () => {
   );
 });
 
+// codex/019fb375-79ec-7b02-b9d8-19fc4bfcc939/019fb37b-45f5-7d20-a5e9-82491ecced7d
+test('keeps the release PostHog host explicit', () => {
+  const publishWorkflow = readFileSync(
+    join(pluginRoot, '.github', 'workflows', 'publish.yml'),
+    'utf8'
+  );
+  const telemetryBuildConfig = readFileSync(
+    join(pluginRoot, 'src', 'telemetry-build-config.ts'),
+    'utf8'
+  );
+  const telemetrySource = readFileSync(
+    join(pluginRoot, 'src', 'telemetry.ts'),
+    'utf8'
+  );
+
+  assert.match(
+    publishWorkflow,
+    /const host = process\.env\.POSTHOG_HOST\?\.trim\(\) \|\| '';/
+  );
+  assert.match(
+    telemetryBuildConfig,
+    /export const BUILT_IN_POSTHOG_HOST = '';/,
+  );
+  assert.match(
+    telemetrySource,
+    /const DEFAULT_POSTHOG_HOST = 'https:\/\/us\.i\.posthog\.com';/
+  );
+});
+
 test('registers prompt submission and stop hooks from the plugin root', () => {
   const config = JSON.parse(
     readFileSync(join(pluginRoot, 'hooks', 'hooks.json'), 'utf8')
diff --git a/test/prompt-hook.test.ts b/test/prompt-hook.test.ts
index 5b6ba5a..bd7d176 100644
--- a/test/prompt-hook.test.ts
+++ b/test/prompt-hook.test.ts
@@ -3,6 +3,7 @@ import { execFileSync, spawn, spawnSync } from 'node:child_process';
 import { once } from 'node:events';
 import {
   cpSync,
+  existsSync,
   mkdirSync,
   mkdtempSync,
   readFileSync,
@@ -294,6 +295,7 @@ test('the executable performs both phases without model-visible output', () => {
   assert.equal(storedPrompt?.previousAgentOutput, null);
 });
 
+// codex/019fb375-79ec-7b02-b9d8-19fc4bfcc939/019fb376-ca9b-7243-af54-c8affdbc0dc3
 test('the executable flushes metadata-only telemetry before exiting', async () => {
   closeDb();
   const capturePath = join(root, 'telemetry-capture.jsonl');
@@ -309,7 +311,7 @@ test('the executable flushes metadata-only telemetry before exiting', async () =
         env: {
           ...process.env,
           DO_NOT_TRACK: '',
-          POSTHOG_API_KEY: 'test-api-key',
+          POSTHOG_PROJECT_TOKEN: 'test-project-token',
           POSTHOG_HOST: receiver.host,
           RUDDER_HOME: process.env.RUDDER_HOME,
         },
@@ -330,7 +332,7 @@ test('the executable flushes metadata-only telemetry before exiting', async () =
       env: {
         ...process.env,
         DO_NOT_TRACK: '',
-        POSTHOG_API_KEY: 'test-api-key',
+        POSTHOG_PROJECT_TOKEN: 'test-project-token',
         POSTHOG_HOST: receiver.host,
         RUDDER_HOME: process.env.RUDDER_HOME,
       },
@@ -354,6 +356,44 @@ test('the executable flushes metadata-only telemetry before exiting', async () =
   }
 });
 
+// codex/019fb375-79ec-7b02-b9d8-19fc4bfcc939/019fb376-ca9b-7243-af54-c8affdbc0dc3
+test('the legacy PostHog API key does not enable telemetry', async () => {
+  closeDb();
+  const capturePath = join(root, 'legacy-telemetry-capture.jsonl');
+  const receiver = await startTelemetryReceiver(capturePath);
+
+  try {
+    const stdout = execFileSync(
+      process.execPath,
+      [hookExecutable, '--source', 'codex'],
+      {
+        cwd: repo,
+        encoding: 'utf8',
+        env: {
+          ...process.env,
+          DO_NOT_TRACK: '',
+          POSTHOG_API_KEY: 'legacy-api-key',
+          POSTHOG_PROJECT_TOKEN: '',
+          POSTHOG_HOST: receiver.host,
+          RUDDER_HOME: process.env.RUDDER_HOME,
+        },
+        input: JSON.stringify({
+          hook_event_name: 'UserPromptSubmit',
+          session_id: 'legacy-telemetry-session',
+          turn_id: 'legacy-telemetry-turn',
+          prompt: 'This prompt must stay local.',
+          cwd: repo,
+        }),
+      }
+    );
+
+    assert.equal(stdout, '');
+    assert.equal(existsSync(capturePath), false);
+  } finally {
+    await receiver.stop();
+  }
+});
+
 test('a release build sends telemetry without user environment configuration', async () => {
   closeDb();
   const capturePath = join(root, 'built-telemetry-capture.jsonl');