diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 03f8deb..42a3e5a 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -2,18 +2,23 @@ name: CI
 
 on:
   push:
-    branches: [main]
+    branches: [main, 'fix/**']
   pull_request:
 
 jobs:
   check:
-    runs-on: ubuntu-latest
+    strategy:
+      fail-fast: false
+      matrix:
+        os: [ubuntu-latest, windows-latest]
+        node: [20, 22]
+    runs-on: ${{ matrix.os }}
     steps:
       - uses: actions/checkout@v4
       - uses: pnpm/action-setup@v4
       - uses: actions/setup-node@v4
         with:
-          node-version: 22
+          node-version: ${{ matrix.node }}
           cache: pnpm
       - uses: oven-sh/setup-bun@v2
         with:
@@ -22,4 +27,4 @@ jobs:
       - run: pnpm typecheck
       - run: pnpm test
       - name: Bundle for npm and smoke it
-        run: pnpm build:npm && node packages/cli/bin/vibi.mjs --version
+        run: pnpm build:npm && node packages/cli/dist/vibi.mjs --version && node packages/cli/dist/vibi.mjs --help
diff --git a/package.json b/package.json
index 1529ea4..a726ce6 100644
--- a/package.json
+++ b/package.json
@@ -5,7 +5,7 @@
   "packageManager": "pnpm@12.8.1",
   "scripts": {
     "typecheck": "pnpm -r typecheck",
-    "test": "tsx --test packages/shared/test/*.test.ts packages/cli/test/*.test.ts",
+    "test": "node scripts/test.mjs",
     "build:npm": "pnpm --filter vibi build:npm",
     "build:host": "pnpm --filter vibi build:tui:host && pnpm --filter vibi build:host",
     "build": "pnpm --filter vibi build:tui && pnpm --filter vibi build"
diff --git a/packages/cli/src/harnesses/install.ts b/packages/cli/src/harnesses/install.ts
index c5bf529..28f94a2 100644
--- a/packages/cli/src/harnesses/install.ts
+++ b/packages/cli/src/harnesses/install.ts
@@ -41,11 +41,18 @@ export function encodeClaudeProjectDir(projectDir: string) {
 }
 
 function originalBasename(metadata: TraceMetadata, fallback: string) {
-  const base = metadata.sourcePath ? path.basename(metadata.sourcePath) : '';
-  return base && base.endsWith('.jsonl') ? base : fallback;
+  const base = path.win32.basename(path.posix.basename(metadata.sourcePath));
+  return isSafeFilename(base) && base.endsWith('.jsonl') ? base : fallback;
+}
+
+function isSafeFilename(value: string): boolean {
+  return Boolean(value) && value !== '.' && value !== '..' &&
+    !/[<>:"/\\|?*\x00-\x1f]/.test(value) && !/[. ]$/.test(value) &&
+    !/^(con|prn|aux|nul|com[1-9]|lpt[1-9])(?:\.|$)/i.test(value);
 }
 
 export function installPathFor(t: Omit<InstallTarget, 'content' | 'overwrite'>): string {
+  if (!isSafeFilename(t.harnessSessionId)) throw new Error('Invalid harness session id for a local file');
   switch (t.harness) {
     case 'claude':
       return path.join(
diff --git a/packages/cli/test/install-paths.test.ts b/packages/cli/test/install-paths.test.ts
new file mode 100644
index 0000000..658c88c
--- /dev/null
+++ b/packages/cli/test/install-paths.test.ts
@@ -0,0 +1,22 @@
+import assert from 'node:assert/strict';
+import path from 'node:path';
+import { test } from 'node:test';
+import { installPathFor } from '../src/harnesses/install';
+import type { Harness } from '@vibivibi/shared/sessions';
+
+const base = { harnessSessionId: 'session-id', harnessUpdatedAt: '2026-10-01T10:00:00Z', home: path.resolve('test-home'), metadata: {title: '', cwd: '', model: '', messageCount: 0, sourcePath: '', startedAt: null} };
+test('untrusted session IDs cannot escape installation directories or create invalid Windows files', () => {
+  for (const harness of ['claude', 'codex', 'pi', 'sc', 'opencode'] as Harness[]) {
+    for (const id of ['../escape', '..\\escape', '/absolute', 'C:\\absolute', '', '.', '..', 'bad\0id', 'CON', 'name:stream', 'trailing.']) {
+      assert.throws(() => installPathFor({...base, harness, harnessSessionId: id}), /Invalid harness session id/);
+    }
+  }
+});
+test('source filenames survive Windows to Unix and Unix to Windows transfers', () => {
+  for (const sourcePath of ['C:\\Users\\sender\\rollout-original.jsonl', '/Users/sender/rollout-original.jsonl']) {
+    const file = installPathFor({...base, harness: 'codex', metadata: {...base.metadata, sourcePath}});
+    assert.equal(path.basename(file), 'rollout-original.jsonl');
+    assert.equal(path.dirname(file), path.join(base.home, '.codex', 'sessions', '2026', '10', '01'));
+  }
+  assert.equal(path.basename(installPathFor({...base, harness: 'pi', metadata: {...base.metadata, sourcePath: '/x/bad:name.jsonl'}})), 'session-id.jsonl');
+});
diff --git a/packages/cli/test/install.test.ts b/packages/cli/test/install.test.ts
index 80bfa39..3b2a76b 100644
--- a/packages/cli/test/install.test.ts
+++ b/packages/cli/test/install.test.ts
@@ -17,10 +17,11 @@ after(async () => {
 const meta = { title: 't', cwd: '/work/x', model: '', messageCount: 1, sourcePath: '', startedAt: null };
 
 test('Claude Code project directories are encoded the way Claude Code does it', () => {
-  assert.equal(encodeClaudeProjectDir('/Users/hongyinluo/Desktop/cybermind'), '-Users-hongyinluo-Desktop-cybermind');
-  assert.equal(encodeClaudeProjectDir('/Users/me/my_app.v2'), '-Users-me-my-app-v2');
+  const prefix = process.platform === 'win32' ? `${path.parse(process.cwd()).root[0]}--` : '-';
+  assert.equal(encodeClaudeProjectDir('/Users/hongyinluo/Desktop/cybermind'), `${prefix}Users-hongyinluo-Desktop-cybermind`);
+  assert.equal(encodeClaudeProjectDir('/Users/me/my_app.v2'), `${prefix}Users-me-my-app-v2`);
   const file = installPathFor({ harness: 'claude', harnessSessionId: 'abc', harnessUpdatedAt: '2026-10-01T10:00:00Z', metadata: meta, home, projectDir: '/work/x' });
-  assert.equal(file, path.join(home, '.claude', 'projects', '-work-x', 'abc.jsonl'));
+  assert.equal(file, path.join(home, '.claude', 'projects', `${prefix}work-x`, 'abc.jsonl'));
 });
 
 test('other harnesses keep their original file names and date folders', () => {
diff --git a/scripts/test.mjs b/scripts/test.mjs
new file mode 100644
index 0000000..c1b7768
--- /dev/null
+++ b/scripts/test.mjs
@@ -0,0 +1,11 @@
+import { spawnSync } from 'node:child_process';
+import { readdirSync } from 'node:fs';
+import { fileURLToPath } from 'node:url';
+
+const root = fileURLToPath(new URL('../', import.meta.url));
+const files = ['packages/shared/test', 'packages/cli/test'].flatMap((dir) =>
+  readdirSync(new URL(`../${dir}/`, import.meta.url)).filter((name) => name.endsWith('.test.ts')).sort().map((name) => `${dir}/${name}`)
+);
+const result = spawnSync(process.execPath, ['--import', 'tsx', '--test', ...files], {cwd: root, stdio: 'inherit'});
+if (result.error) throw result.error;
+process.exit(result.status ?? 1);