diff --git a/browse/src/browser-manager.ts b/browse/src/browser-manager.ts
index f9f3317b5..9d6351193 100644
--- a/browse/src/browser-manager.ts
+++ b/browse/src/browser-manager.ts
@@ -803,15 +803,14 @@ export class BrowserManager {
     this.tabSessions.delete(tabId);
     this.tabOwnership.delete(tabId);
 
-    // Switch to another tab if we closed the active one
-    if (tabId === this.activeTabId) {
+    // Never leave zero tabs, regardless of which tab was closed — activeTabId
+    // can point at an already-removed id, and the old active-only guard then
+    // skipped auto-create when the last tab closed.
+    if (this.pages.size === 0) {
+      await this.newTab();
+    } else if (tabId === this.activeTabId) {
       const remaining = [...this.pages.keys()];
-      if (remaining.length > 0) {
-        this.activeTabId = remaining[remaining.length - 1];
-      } else {
-        // No tabs left — create a new blank one
-        await this.newTab();
-      }
+      this.activeTabId = remaining[remaining.length - 1];
     }
   }
 
diff --git a/browse/src/server.ts b/browse/src/server.ts
index 301781acc..4c9103edc 100644
--- a/browse/src/server.ts
+++ b/browse/src/server.ts
@@ -664,6 +664,11 @@ export const __testInternals__ = {
   // need shutdown to fire. Without this, the second test's shutdown
   // returns early at the `if (isShuttingDown) return;` guard.
   resetShutdownState: () => { isShuttingDown = false; },
+  // Stop the module-level 60s idle interval. In-process test runs import this
+  // module once for the whole suite; the interval otherwise outlives the test
+  // file and can fire a real process.exit(0) mid-suite, silently truncating
+  // the run with a green exit code.
+  stopIdleTimer: () => { clearInterval(idleCheckInterval); },
 };
 
 // ─── Parent-Process Watchdog ────────────────────────────────────────
diff --git a/browse/test/cdp-e2e.test.ts b/browse/test/cdp-e2e.test.ts
index c6b2c8a8a..2bcd66dfa 100644
--- a/browse/test/cdp-e2e.test.ts
+++ b/browse/test/cdp-e2e.test.ts
@@ -18,6 +18,7 @@ import { startTestServer } from './test-server';
 import { BrowserManager } from '../src/browser-manager';
 
 const TMP_HOME = path.join(os.tmpdir(), `gstack-cdp-e2e-${process.pid}-${Date.now()}`);
+const ORIG_GSTACK_HOME = process.env.GSTACK_HOME;
 process.env.GSTACK_HOME = TMP_HOME;
 process.env.GSTACK_TELEMETRY_OFF = '1'; // don't pollute analytics during tests
 
@@ -36,6 +37,11 @@ beforeAll(async () => {
 });
 
 afterAll(async () => {
+  // Un-leak GSTACK_HOME: it outranks GSTACK_STATE_DIR in bin/gstack-config,
+  // so leaving it set breaks later test files in-process.
+  if (ORIG_GSTACK_HOME === undefined) delete process.env.GSTACK_HOME;
+  else process.env.GSTACK_HOME = ORIG_GSTACK_HOME;
+
   try { await bm.cleanup?.(); } catch {}
   try { testServer.server.stop(); } catch {}
   await fs.rm(TMP_HOME, { recursive: true, force: true });
diff --git a/browse/test/domain-skills-e2e.test.ts b/browse/test/domain-skills-e2e.test.ts
index 29d33c4bc..598d7bdc0 100644
--- a/browse/test/domain-skills-e2e.test.ts
+++ b/browse/test/domain-skills-e2e.test.ts
@@ -17,6 +17,7 @@ import { startTestServer } from './test-server';
 import { BrowserManager } from '../src/browser-manager';
 
 const TMP_HOME = path.join(os.tmpdir(), `gstack-domain-e2e-${process.pid}-${Date.now()}`);
+const ORIG_GSTACK_HOME = process.env.GSTACK_HOME;
 process.env.GSTACK_HOME = TMP_HOME;
 process.env.GSTACK_PROJECT_SLUG = 'e2e-test-slug';
 
@@ -41,6 +42,11 @@ beforeAll(async () => {
 });
 
 afterAll(async () => {
+  // Un-leak GSTACK_HOME: it outranks GSTACK_STATE_DIR in bin/gstack-config,
+  // so leaving it set breaks later test files in-process.
+  if (ORIG_GSTACK_HOME === undefined) delete process.env.GSTACK_HOME;
+  else process.env.GSTACK_HOME = ORIG_GSTACK_HOME;
+
   try { await bm.cleanup?.(); } catch {}
   try { testServer.server.stop(); } catch {}
   await fs.rm(TMP_HOME, { recursive: true, force: true });
diff --git a/browse/test/domain-skills-storage.test.ts b/browse/test/domain-skills-storage.test.ts
index df53d8bc9..c81a0c9f5 100644
--- a/browse/test/domain-skills-storage.test.ts
+++ b/browse/test/domain-skills-storage.test.ts
@@ -1,11 +1,19 @@
-import { describe, it, expect, beforeEach } from 'bun:test';
+import { describe, it, expect, beforeEach, afterAll } from 'bun:test';
 import { promises as fs } from 'fs';
 import * as path from 'path';
 import * as os from 'os';
 
 const TMP_HOME = path.join(os.tmpdir(), `gstack-test-${process.pid}-${Date.now()}`);
+const ORIG_GSTACK_HOME = process.env.GSTACK_HOME;
 process.env.GSTACK_HOME = TMP_HOME;
 
+afterAll(() => {
+  // Un-leak GSTACK_HOME: it outranks GSTACK_STATE_DIR in bin/gstack-config,
+  // so leaving it set breaks later test files in-process.
+  if (ORIG_GSTACK_HOME === undefined) delete process.env.GSTACK_HOME;
+  else process.env.GSTACK_HOME = ORIG_GSTACK_HOME;
+});
+
 // Re-import after env var set so module reads updated GSTACK_HOME
 async function freshImport() {
   // Bun caches modules; force reload by appending a query-string-like hack via dynamic import URL
diff --git a/browse/test/gstack-config.test.ts b/browse/test/gstack-config.test.ts
index e342a50b7..676fa55bc 100644
--- a/browse/test/gstack-config.test.ts
+++ b/browse/test/gstack-config.test.ts
@@ -18,7 +18,12 @@ function run(args: string[] = [], extraEnv: Record<string, string> = {}) {
   const result = Bun.spawnSync(['bash', SCRIPT, ...args], {
     env: {
       ...process.env,
+      // Set all three state-dir vars: other test files leak GSTACK_HOME /
+      // GSTACK_STATE_ROOT into process.env at module scope, and those
+      // outrank GSTACK_STATE_DIR in the script's resolution order.
       GSTACK_STATE_DIR: stateDir,
+      GSTACK_STATE_ROOT: stateDir,
+      GSTACK_HOME: stateDir,
       ...extraEnv,
     },
     stdout: 'pipe',
diff --git a/browse/test/server-factory.test.ts b/browse/test/server-factory.test.ts
index 6b5feb264..0cfc73126 100644
--- a/browse/test/server-factory.test.ts
+++ b/browse/test/server-factory.test.ts
@@ -411,6 +411,27 @@ function makeMockBrowserManager(mode: 'launched' | 'headed') {
 }
 
 describe('idle timer + onDisconnect dual-instance fix', () => {
+  // File-scoped process.exit guard. The shutdown path is fire-and-forget
+  // async: a test's per-call exit stub can be restored while a second
+  // shutdown invocation is still in flight, and that straggler then hits the
+  // REAL process.exit(0) — truncating the whole bun test run mid-suite with
+  // a green exit code and no failure tally. Per-test stubs installed below
+  // capture-and-restore against this file stub, never the real exit.
+  const fileExitStub = mock((_code?: number) => {});
+  let realProcessExit: typeof process.exit;
+  beforeAll(() => {
+    realProcessExit = process.exit;
+    (process as any).exit = fileExitStub;
+  });
+  afterAll(async () => {
+    // Kill the leaked module-level 60s interval so it can't fire shutdown
+    // (with the real process.exit) during a later test file.
+    __testInternals__.stopIdleTimer();
+    // Grace period: let any straggler async shutdown land on the stub.
+    await new Promise<void>(r => setTimeout(r, 300));
+    (process as any).exit = realProcessExit;
+  });
+
   beforeEach(() => {
     __resetRegistry();
     // Reset module state every test. Bun memoizes the server.ts module
@@ -453,14 +474,19 @@ describe('idle timer + onDisconnect dual-instance fix', () => {
       buildFetchHandler(makeMinimalConfig({ browserManager: mockBM as any }));
       __testInternals__.setLastActivity(Date.now() - (31 * 60 * 1000));
       __testInternals__.idleCheckTick();
-      // Drain microtasks: shutdown awaits flushBuffers + cfgBrowserManager.close
-      // before reaching process.exit.
-      await Promise.resolve();
-      await Promise.resolve();
-      await new Promise<void>(r => setImmediate(r));
-      await new Promise<void>(r => setImmediate(r));
+      // Poll until the fire-and-forget shutdown reaches process.exit. A fixed
+      // microtask drain can lose the race on slower hosts — and then the REAL
+      // process.exit(0) fires after the finally restores it, killing the whole
+      // bun test run mid-suite with a green exit code and no failure tally.
+      for (let i = 0; i < 500 && exitMock.mock.calls.length === 0; i++) {
+        await new Promise<void>(r => setTimeout(r, 10));
+      }
       expect(exitMock).toHaveBeenCalled();
     } finally {
+      // Reset activity so the module-level 60s idle interval (which outlives
+      // this file) cannot re-fire shutdown with the real process.exit later
+      // in the suite.
+      __testInternals__.setLastActivity(Date.now());
       (process as any).exit = originalExit;
     }
   });
diff --git a/browse/test/telemetry.test.ts b/browse/test/telemetry.test.ts
index d3cd3219c..f041ea1f4 100644
--- a/browse/test/telemetry.test.ts
+++ b/browse/test/telemetry.test.ts
@@ -8,6 +8,7 @@ const TELEMETRY_FILE = path.join(TMP_HOME, 'analytics', 'browse-telemetry.jsonl'
 
 // Use GSTACK_HOME env to redirect telemetry writes (read each call,
 // not cached at module-load).
+const ORIG_GSTACK_HOME = process.env.GSTACK_HOME;
 process.env.GSTACK_HOME = TMP_HOME;
 process.env.GSTACK_TELEMETRY_OFF = '0';
 
@@ -17,6 +18,10 @@ beforeEach(async () => {
 
 afterAll(async () => {
   await fs.rm(TMP_HOME, { recursive: true, force: true });
+  // Un-leak GSTACK_HOME: it outranks GSTACK_STATE_DIR in bin/gstack-config's
+  // resolution order, so leaving it set breaks later test files in-process.
+  if (ORIG_GSTACK_HOME === undefined) delete process.env.GSTACK_HOME;
+  else process.env.GSTACK_HOME = ORIG_GSTACK_HOME;
 });
 
 async function readEvents(): Promise<any[]> {