diff --git a/apps/cli/__tests__/host-agent.test.ts b/apps/cli/__tests__/host-agent.test.ts
index d63168d5..7d653c80 100644
--- a/apps/cli/__tests__/host-agent.test.ts
+++ b/apps/cli/__tests__/host-agent.test.ts
@@ -4331,13 +4331,13 @@ describe('HostAgentSupervisor — re-link of an env-delivered credential', () =>
     fs.rmSync(tmpRoot, { recursive: true, force: true });
   });
 
-  function boot(auth: AgentAuth) {
+  function boot(auth: AgentAuth, agent = 'claude_code') {
     const a = path.join(tmpRoot, 'dep-a');
     const b = path.join(tmpRoot, 'dep-b');
     fs.mkdirSync(a, { recursive: true });
     fs.mkdirSync(b, { recursive: true });
     let list: Rec[] = [
-      { deployId: 'dep-a', cwd: a, agent: 'claude_code', startedAt: 1 },
+      { deployId: 'dep-a', cwd: a, agent, startedAt: 1 },
       { deployId: 'dep-b', cwd: b, agent: 'codex', startedAt: 2 },
     ];
     const spawned: Array<{ env: Record<string, string>; proc: ReturnType<typeof fakeProc> }> = [];
@@ -4360,7 +4360,7 @@ describe('HostAgentSupervisor — re-link of an env-delivered credential', () =>
         id: 'cmd-refresh',
         sessionId: 'sh-plugin-1',
         type: 'self_hosted_refresh_credentials',
-        payload: { agentId: 'claude_code', sealedAgentAuth: 'sealed-fresh' },
+        payload: { agentId: agent, sealedAgentAuth: 'sealed-fresh' },
       });
     return { sup, spawned, refresh };
   }
@@ -4417,6 +4417,30 @@ describe('HostAgentSupervisor — re-link of an env-delivered credential', () =>
       sup.stop();
     }
   });
+
+  // agy holds its token in memory (verified 2026-11-06: a rewritten token file is never read
+  // again by the running process), so a re-link must restart its sessions or they keep the
+  // expired login.
+  it('oauth_token for Antigravity: rewrites its token file AND restarts only its children', async () => {
+    const blob =
+      '{"token":{"access_token":"ya29.fresh","token_type":"Bearer","refresh_token":"1//fresh","expiry":"2099-01-01T00:00:00Z"},"auth_method":"consumer"}';
+    const { sup, spawned, refresh } = boot({ kind: 'oauth_token', value: blob }, 'antigravity');
+    try {
+      const oldA = bySession(spawned, 'sess-a')[0].proc;
+      const oldB = bySession(spawned, 'sess-b')[0].proc;
+
+      await refresh();
+
+      const file = path.join(tmpRoot, '.gemini', 'antigravity-cli', 'antigravity-oauth-token');
+      expect(JSON.parse(fs.readFileSync(file, 'utf8')).token.access_token).toBe('ya29.fresh');
+      expect(oldA.kill).toHaveBeenCalledWith('SIGTERM');
+      expect(bySession(spawned, 'sess-a')).toHaveLength(2);
+      expect(oldB.kill).not.toHaveBeenCalled();
+      expect(bySession(spawned, 'sess-b')).toHaveLength(1);
+    } finally {
+      sup.stop();
+    }
+  });
 });
 
 /**
diff --git a/apps/cli/src/commands/host-agent.ts b/apps/cli/src/commands/host-agent.ts
index da45208f..f306667b 100644
--- a/apps/cli/src/commands/host-agent.ts
+++ b/apps/cli/src/commands/host-agent.ts
@@ -227,6 +227,16 @@ const HEARTBEAT_INTERVAL_MS = 20_000;
  */
 export const RESUME_RETRY_BACKOFF_MS = [15_000, 30_000, 60_000, 120_000] as const;
 
+/**
+ * Agents whose login FILE is read once at start and then held in memory, so rewriting it on a
+ * re-link changes nothing for a running session: those children are restarted (resume path, same
+ * conversation) like an env-delivered key. Antigravity CLI: verified 2026-11-06 on agy 1.5.2 — after
+ * a rewrite of `~/.gemini/antigravity-cli/antigravity-oauth-token`, the next prompt never read the
+ * file again (its atime stayed behind the rewrite under relatime). Claude Code and Codex re-read
+ * theirs on a 401 and stay in place.
+ */
+export const AUTH_FILE_CACHED_IN_MEMORY: ReadonlySet<string> = new Set(['antigravity']);
+
 /** A child must have been up this long before its death counts as a crash to respawn
  *  (shorter = it never came up → report `failed` instead of looping). */
 export const CRASH_RESPAWN_MIN_UPTIME_MS = 60_000;
@@ -2984,6 +2994,17 @@ export class HostAgentSupervisor {
       const auth = await this.resolveAgentAuth(this.identity, payload.sealedAgentAuth);
       const credEnv = provisionAgentCredentials(payload.agentId, auth, undefined);
       const affected = [...this.children.values()].filter((c) => c.agent === payload.agentId);
+      if (Object.keys(credEnv).length === 0 && AUTH_FILE_CACHED_IN_MEMORY.has(payload.agentId)) {
+        for (const child of affected) {
+          this.credentialEnvByDeploy.delete(child.deployId);
+          this.restartWithFreshCredentials(child);
+        }
+        log.info(
+          'host-agent',
+          `refreshed login file for agent=${payload.agentId}; restarted ${affected.length} child(ren)`,
+        );
+        return;
+      }
       if (Object.keys(credEnv).length === 0) {
         for (const c of affected) this.credentialEnvByDeploy.delete(c.deployId);
         log.info(