Visual Studio Code 1.133 introduces a new Agent Host process and major AI session architecture shift
Another VS Code released today. Microsoft just shipped VS Code 1.133, and it fundamentally changes how the editor handles AI agents. Starting today, agent sessions run in a dedicated background process instead of inside the editor's extension host. The move unlocks shared multi-window access, remote execution, and an open protocol that Microsoft is explicitly positioning alongside LSP and DAP.
It's been nearly a year since the initial agent preview landed, and the architecture has clearly matured. Back when agents first ran inside the extension host, you could practically hear the main thread groan under a single long-running Codex loop. The new Agent Host process decouples that work entirely. Sessions continue running even after you close the editor window. You can hand off control to another VS Code instance, a web dashboard, or a CLI tool without breaking the conversation.
The Agent Host Protocol
Microsoft is calling the new communication layer AHP, short for Agent Host Protocol. The spec just dropped on GitHub under an MIT license, and it mirrors the exact extensibility model that made VS Code what it is today. Clients subscribe to URI-addressed channels for sessions, terminals, and changesets. Every state change carries a monotonic sequence number and broadcasts to all subscribers in strict order.
First-party adapters for Copilot, Claude, and Codex all translate their native runtimes into AHP. You can run a host locally or point it at a remote machine via SSH or dev tunnels. Just type code agent host in your terminal to spin one up. The extension host stays active as a fallback if you flip chat.agentHost.enabled to false.
Mixed models and quality-of-life tweaks
The process overhaul isn't the only change in this build. Claude sessions now let you mix Anthropic API models and Copilot-backed models in the same conversation. The model picker groups them under two clear headings, and switching between turns takes a single click. You pay out of pocket for the heavier reasoning tasks and burn through Copilot credits for the routine work.
There's also a new experimental toggle that opens the Agents window without forcing a GitHub sign-in. That's a welcome change for developers working with their own API keys on machines that can't reach GitHub. Sticky scroll for chat prompts pins your most recent question to the top of the conversation as you scroll through history. The integrated browser now auto-reloads HTML files when they change on disk, which finally cuts out the manual refresh cycle.
It's a heavy engineering undertaking, though the friction points it removes are real. The open AHP spec is exactly the kind of move that tends to build a healthy ecosystem, even if early adapters will need to map their own tooling to the protocol. Not cheap to implement, but the payoff is a session model that actually feels like a shared resource rather than a locked app window.
VS Code 1.133 is rolling out to Windows, macOS, and Linux across x64 and Arm64 builds. You can grab the update through the built-in update checker, or head here for the download.
