diff --git a/src/__tests__/session-codex-install.test.ts b/src/__tests__/session-codex-install.test.ts
new file mode 100644
index 000000000..0a9ea7bd0
--- /dev/null
+++ b/src/__tests__/session-codex-install.test.ts
@@ -0,0 +1,101 @@
+/**
+ * Codex counts as installed before its first session: `~/.codex/sessions/` only
+ * appears once Codex has run a session, so a member who installed Codex but
+ * never used it must still be a valid migrate target.
+ */
+import { afterEach, beforeEach, describe, expect, it, vi } from 'vitest';
+import fs from 'node:fs';
+import os from 'node:os';
+import path from 'node:path';
+
+const mocks = vi.hoisted(() => ({ home: '' }));
+
+vi.mock('node:os', async (importOriginal) => {
+  const actual = (await importOriginal()) as unknown as Record<string, unknown> & { default?: object };
+  const patched: Record<string, unknown> = { ...actual, homedir: () => mocks.home };
+  patched.default = { ...actual.default, homedir: () => mocks.home };
+  return patched;
+});
+
+import { getAdapter, listInstalledPlatforms } from '../session-flow/adapters/index.js';
+import { MigrationEngine } from '../session-flow/migrate.js';
+import type { Session } from '../session-flow/ir.js';
+
+const SESSION_ID = '11111111-2222-4333-8444-555555555555';
+
+let tmp = '';
+let emptyBin = '';
+const savedPath = process.env.PATH;
+
+beforeEach(() => {
+  tmp = fs.mkdtempSync(path.join(os.tmpdir(), 'codex-install-'));
+  mocks.home = path.join(tmp, 'home');
+  fs.mkdirSync(mocks.home);
+  emptyBin = path.join(tmp, 'empty-bin');
+  fs.mkdirSync(emptyBin);
+  process.env.PATH = emptyBin;
+});
+
+afterEach(() => {
+  process.env.PATH = savedPath;
+  mocks.home = '';
+  fs.rmSync(tmp, { recursive: true, force: true });
+});
+
+/** Plants a Claude Code session for `cwd` and returns its id. */
+async function plantClaudeSession(cwd: string): Promise<string> {
+  fs.mkdirSync(path.join(mocks.home, '.claude', 'projects'), { recursive: true });
+  const session: Session = {
+    sessionId: SESSION_ID,
+    title: 'hello codex',
+    cwd,
+    platform: 'claude-code',
+    createdAt: '2026-09-20T10:00:00.000Z',
+    updatedAt: '2026-09-20T10:01:00.000Z',
+    messages: [
+      { role: 'user', content: [{ type: 'text', text: 'hello codex' }], timestamp: '2026-09-20T10:00:00.000Z' },
+      { role: 'assistant', content: [{ type: 'text', text: 'hi' }], timestamp: '2026-09-20T10:00:30.000Z' },
+    ],
+    metadata: {},
+  };
+  return getAdapter('claude-code').writeSession(session, cwd);
+}
+
+describe('Codex installed without a sessions directory', () => {
+  it('migrates into Codex when only ~/.codex exists, creating the dated sessions dir', async () => {
+    const cwd = path.join(tmp, 'proj');
+    fs.mkdirSync(cwd);
+    const sourceId = await plantClaudeSession(cwd);
+    fs.mkdirSync(path.join(mocks.home, '.codex'));
+
+    const result = await new MigrationEngine('claude-code', 'codex').migrate(sourceId, cwd);
+
+    expect(result.error).toBeUndefined();
+    expect(result.success).toBe(true);
+    const dayDir = path.join(mocks.home, '.codex', 'sessions', '2026', '09', '20');
+    const rollouts = fs.readdirSync(dayDir).filter((f) => f.endsWith('.jsonl'));
+    expect(rollouts).toHaveLength(1);
+    expect(rollouts[0]).toContain(result.targetSessionId);
+  });
+
+  it('lists Codex as installed when the codex CLI is on PATH and ~/.codex does not exist yet', () => {
+    const bin = path.join(tmp, 'bin');
+    fs.mkdirSync(bin);
+    const exe = path.join(bin, 'codex');
+    fs.writeFileSync(exe, '#!/bin/sh\n');
+    fs.chmodSync(exe, 0o755);
+    process.env.PATH = bin;
+
+    expect(listInstalledPlatforms()).toContain('codex');
+  });
+
+  it('does not list Codex when neither ~/.codex nor the codex CLI is present', () => {
+    expect(listInstalledPlatforms()).not.toContain('codex');
+  });
+
+  it('lists no Codex sessions, without failing, when ~/.codex has no sessions dir', async () => {
+    fs.mkdirSync(path.join(mocks.home, '.codex'));
+
+    await expect(getAdapter('codex').listConversations()).resolves.toEqual([]);
+  });
+});
diff --git a/src/__tests__/session-sync.test.ts b/src/__tests__/session-sync.test.ts
index a51359725..6f16e91cb 100644
--- a/src/__tests__/session-sync.test.ts
+++ b/src/__tests__/session-sync.test.ts
@@ -1,4 +1,5 @@
 import { describe, it, expect, beforeEach, afterEach } from 'vitest';
+import { execFileSync } from 'node:child_process';
 import fs from 'node:fs';
 import os from 'node:os';
 import path from 'node:path';
@@ -392,6 +393,52 @@ describe('rebuildIndex', () => {
   });
 });
 
+describe('session pull (gitPull + rebuildIndex) on a team checkout', () => {
+  const identity = 'github.com/org/alpha';
+  const git = (cwd: string, ...args: string[]): string =>
+    execFileSync('git', args, { cwd, encoding: 'utf-8', stdio: ['ignore', 'pipe', 'pipe'] }).trim();
+
+  function initCheckout(dir: string, name: string): void {
+    git(dir, 'config', 'user.name', name);
+    git(dir, 'config', 'user.email', `${name}@example.com`);
+  }
+
+  function pushSession(checkout: string, sessionId: string, title: string): void {
+    const mgr = new SyncManager(checkout);
+    mgr.saveSession(mkSession({ sessionId, title }), mkMeta({ sessionId, title }));
+    expect(mgr.gitCommit(`push ${title}`).status).toBe('committed');
+    mgr.gitPush();
+  }
+
+  function pull(checkout: string): void {
+    const mgr = new SyncManager(checkout);
+    mgr.gitPull();
+    mgr.rebuildIndex(identity);
+  }
+
+  it('leaves the checkout clean when nothing changed, so the next index change merges', () => {
+    const remote = path.join(repoRoot, 'team.git');
+    git(repoRoot, 'init', '-q', '--bare', '-b', 'main', remote);
+    const alice = path.join(repoRoot, 'alice');
+    git(repoRoot, 'init', '-q', '-b', 'main', alice);
+    initCheckout(alice, 'alice');
+    git(alice, 'remote', 'add', 'origin', remote);
+    pushSession(alice, 's-1', 'fix payment');
+    const bob = path.join(repoRoot, 'bob');
+    git(repoRoot, 'clone', '-q', remote, bob);
+    initCheckout(bob, 'bob');
+
+    pull(bob);
+    pull(bob);
+    expect(git(bob, 'status', '--porcelain')).toBe('');
+
+    pushSession(alice, 's-2', 'add refunds');
+    pull(bob);
+    expect(git(bob, 'status', '--porcelain')).toBe('');
+    expect(new SyncManager(bob).listSessions(identity).map((s) => s.sessionId).sort()).toEqual(['s-1', 's-2']);
+  });
+});
+
 describe('canonicalizeRemote', () => {
   it('strips credentials embedded in the remote URL', () => {
     // Tokens live in remotes on CI checkouts; publishing them into the
diff --git a/src/session-flow/adapters/codex.ts b/src/session-flow/adapters/codex.ts
index 0c120ab27..694c7844e 100644
--- a/src/session-flow/adapters/codex.ts
+++ b/src/session-flow/adapters/codex.ts
@@ -47,6 +47,7 @@ import { titleFromUserText, visibleUserText } from '../title.js';
 import { assertSafeSessionFileId, resolveWriteSessionId } from '../ids.js';
 import { findSqlite3 } from '../sqlite.js';
 import { log } from '../../utils/logger.js';
+import { isOnPath } from '../../utils/lookpath.js';
 import {
   getCodexSessionsDir,
   resolveRealCwd,
@@ -276,8 +277,13 @@ export class CodexAdapter extends AgentAdapter {
     return getCodexSessionsDir();
   }
 
+  /**
+   * Codex creates `sessions/` on its first session, so an installed Codex that
+   * has not run one yet only has its root (or just the CLI); writeSession
+   * creates the dated directory itself.
+   */
   isReady(): boolean {
-    return dirExists(this.storageRoot);
+    return dirExists(path.dirname(this.storageRoot)) || (this.platform === 'codex' && isOnPath('codex'));
   }
 
   private scanJsonlFiles(): string[] {
diff --git a/src/session-flow/sync.ts b/src/session-flow/sync.ts
index a9264da09..d4dff78ff 100644
--- a/src/session-flow/sync.ts
+++ b/src/session-flow/sync.ts
@@ -441,8 +441,18 @@ export class SyncManager {
     // then be checking a path that already exists on the wrong side.
     this.guardWrite(path.join(dir, '_index.json'));
     fs.mkdirSync(dir, { recursive: true });
-    index.updatedAt = utcNow();
     const target = path.join(dir, '_index.json');
+    // Same sessions → leave the file byte-identical. A fresh updatedAt on every
+    // `session pull` kept the team checkout modified, and the next pull that
+    // brought index changes then refused to merge.
+    try {
+      const previous = fs.readFileSync(target, 'utf-8');
+      const updatedAt = (JSON.parse(previous) as RepoIndex).updatedAt;
+      if (JSON.stringify({ ...index, updatedAt }, null, 2) === previous) return;
+    } catch {
+      // No index yet, or a corrupt one: write it.
+    }
+    index.updatedAt = utcNow();
     // Atomic write: land a temp file, then rename. A direct writeFileSync lets two concurrent pushes
     // truncate each other and leave a partial (or empty) _index.json, which makes every session in the repo
     // look like it vanished. rename is atomic on the same filesystem, so readers see either the old value or the new one.
@@ -886,6 +896,22 @@ export class SyncManager {
       }
     }
 
+    // Push records the session's own updatedAt, which meta does not keep, and
+    // appends in push order. Keep both from the current index so rebuilding an
+    // unchanged archive reproduces the committed index instead of modifying it.
+    const key = (e: IndexEntry) => `${e.sessionName}:${e.author}`;
+    let known: IndexEntry[] = [];
+    try {
+      const sessions = (JSON.parse(fs.readFileSync(path.join(dir, '_index.json'), 'utf-8')) as RepoIndex).sessions;
+      if (Array.isArray(sessions)) known = sessions;
+    } catch {
+      // No index yet, or a corrupt one: rebuild from disk alone.
+    }
+    const knownAt = new Map(known.map((e, i) => [key(e), { i, updatedAt: e.updatedAt }]));
+    for (const e of entries) e.updatedAt = knownAt.get(key(e))?.updatedAt ?? e.updatedAt;
+    const rank = (e: IndexEntry) => knownAt.get(key(e))?.i ?? known.length;
+    entries.sort((a, b) => rank(a) - rank(b));
+
     this.writeIndex(
       repoIdentity,
       {