Deepest ChatGPT integration
If you live in ChatGPT, Atlas is the most seamless way to use it. The assistant is woven through the browsing experience in a way a separate MCP client cannot fully match.
The ChatGPT Atlas alternative that does not lock you to one AI.
ChatGPT Atlas bakes one assistant, ChatGPT, into the browser. Sessionat is the open-source Mac browser that lets you bring your own AI through MCP (Claude, Cursor, or OpenAI Codex), runs read-only by default, and adds Arc-style workspaces with auto-saved sessions.
At a glance
Sessionat
ChatGPT Atlas
Engine
Chromium
Chromium (Blink)
AI control (MCP)
Bring your own: Claude, Cursor, Codex
ChatGPT only, built in
Auto-saved sessions
Every 30s, named restore
No journal
Workspaces
Arc-style sidebar
Tabs only
Open source
Yes (MIT)
No (closed)
Price
Free
Free; Agent Mode needs Plus (~$20/mo)
Compiled June 2026 from public sources. Browser features change fast, so verify before relying on a detail.
The trade-off
Atlas ships one AI in the box. Sessionat lets you bring your own.
ChatGPT Atlas is OpenAI’s Chromium browser with ChatGPT built in and an "Agent Mode" that can act on pages for you. It launched on macOS on October 21, 2025, and Agent Mode requires a ChatGPT Plus subscription (around $20 a month). If you already live inside ChatGPT, the integration is genuinely deep and well made.
Sessionat takes the opposite bet. Instead of wiring in one vendor’s assistant, it speaks the open MCP standard, so you connect whichever client you prefer (Claude Desktop, Cursor, or OpenAI Codex) and it clicks, types, and navigates in your real browser, on the accounts you are already signed into. It runs read-only by default, with write access granted per client, so an agent cannot act until you say so. On top of that you get Arc-style workspaces and sessions auto-saved every 30 seconds with named restore.
Worth stating plainly: in 2025 LayerX reported a "Tainted Memories" CSRF issue in Atlas and found its built-in phishing protection weak (blocking far fewer in-the-wild attacks than Chrome or Edge). Sessionat’s read-only-by-default posture and local-first, no-telemetry design are a different stance, but agentic browsing is new for everyone, so verify the current state before trusting any of them with sensitive accounts.
| Feature | Sessionat | ChatGPT Atlas |
|---|---|---|
| Bring your own AI via MCP | ✗ | |
| AI acts on your real logins | ||
| Read-only by default, per-client write permission | ✗ | |
| Built-in agent for one vendor’s AI | Any MCP client | |
| Arc-style workspaces | ✗ | |
| Auto-saved session journal | ✗ | |
| Local visit history your AI can search | ChatGPT memory | |
| Open source | ✗ | |
| No telemetry, local-first | ✗ | |
| No paid subscription for AI control | Plus for Agent |
Honest assessment
Where ChatGPT Atlas is the better choice.
A strong built-in agent
For ChatGPT Plus subscribers, Atlas Agent Mode is a capable, polished agent out of the box, with no setup of an external MCP client required.
Backed by OpenAI
Atlas ships from OpenAI with a fast release cadence and tight ties to the latest ChatGPT models and features as they land.
Zero-config AI for ChatGPT users
Sign in once and the AI is there. Sessionat asks you to connect an MCP client and grant write permission, which is a little more setup up front.
FAQ
Real questions about switching from ChatGPT Atlas.
Is Sessionat just ChatGPT Atlas with a different name?
No. Atlas builds ChatGPT directly into the browser and is closed source. Sessionat is open source (MIT) and vendor-neutral: you connect your own AI through the open MCP standard, whether that is Claude, Cursor, or OpenAI Codex.
Can I use ChatGPT with Sessionat?
You can browse to chatgpt.com like in any browser. For agentic control, Sessionat uses MCP, so you can point an MCP-capable client (including OpenAI Codex) at it. It does not embed ChatGPT as a built-in assistant the way Atlas does.
How does Sessionat handle the security concerns raised about Atlas?
In 2025 LayerX reported a "Tainted Memories" CSRF issue in Atlas and weak built-in phishing protection. Sessionat takes a different approach: it runs read-only by default, grants write access per MCP client, and is local-first with no telemetry. Agentic browsing is new across the board, so always review permissions before granting them.
Does Atlas Agent Mode cost money? Does Sessionat?
Atlas is free to download, but its Agent Mode requires a ChatGPT Plus subscription (around $20 a month). Sessionat is free and open source, and connecting your AI via MCP does not require a Sessionat subscription.
Do either of these isolate browser fingerprints?
No, and neither claims to. Atlas has no fingerprint or profile isolation, and Sessionat is not an anti-detect tool either (that is a separate paid product). Both are macOS browsers focused on AI-assisted browsing, not stealth.
Give your AI a real browser.
Free, open source, no account needed. Keep ChatGPT Atlas installed and try Sessionat side by side.
Download Sessionat for Mac (free)