diff --git a/cli/src/agent/sessionFactory.test.ts b/cli/src/agent/sessionFactory.test.ts
new file mode 100644
index 00000000..f6352ce2
--- /dev/null
+++ b/cli/src/agent/sessionFactory.test.ts
@@ -0,0 +1,28 @@
+import { afterEach, describe, expect, it } from 'vitest'
+import { buildSessionMetadata } from './sessionFactory'
+
+describe('buildSessionMetadata', () => {
+    const originalHostname = process.env.HAPI_HOSTNAME
+
+    afterEach(() => {
+        if (originalHostname === undefined) {
+            delete process.env.HAPI_HOSTNAME
+        } else {
+            process.env.HAPI_HOSTNAME = originalHostname
+        }
+    })
+
+    it('uses HAPI_HOSTNAME for session metadata host when provided', () => {
+        process.env.HAPI_HOSTNAME = 'custom-session-host'
+
+        const metadata = buildSessionMetadata({
+            flavor: 'codex',
+            startedBy: 'terminal',
+            workingDirectory: '/tmp/project',
+            machineId: 'machine-1',
+            now: 123
+        })
+
+        expect(metadata.host).toBe('custom-session-host')
+    })
+})
diff --git a/cli/src/agent/sessionFactory.ts b/cli/src/agent/sessionFactory.ts
index 8fc1dfbc..ddbea808 100644
--- a/cli/src/agent/sessionFactory.ts
+++ b/cli/src/agent/sessionFactory.ts
@@ -63,7 +63,7 @@ export function buildSessionMetadata(options: {
 
     return {
         path: options.workingDirectory,
-        host: os.hostname(),
+        host: process.env.HAPI_HOSTNAME || os.hostname(),
         version: packageJson.version,
         os: os.platform(),
         machineId: options.machineId,