Microsoft has shipped Visual Studio Code 1.133, and the headline change is architectural rather than cosmetic: AI agent sessions now run in a dedicated background process rather than within the editor’s extension host.
The release, which rolled out August 12, moves agent execution into what Microsoft calls the Agent Host, a standalone process built on a new open specification: the Agent Host Protocol (AHP). Microsoft published the AHP spec on GitHub under an MIT license, positioning it alongside the Language Server Protocol (LSP) and Debug Adapter Protocol (DAP) as infrastructure other tools can build on, not just a VS Code implementation detail.
The practical effect for developers is that an agent session no longer has to live and die with a single editor window. Because the host runs independently, multiple VS Code windows can connect to the same session and see a synchronized view. The protocol uses JSON-RPC, immutable state, and pure reducers to keep clients in sync, with each state change carrying a sequence number so nothing arrives out of order. Sessions can also run remotely, reached over SSH or a dev tunnel, which matters for teams running agents against machines that aren’t sitting on a developer’s desk.
“Moving agent sessions into a standalone host lets a developer reconnect to a running session from another window or over SSH. The agent no longer dies when one editor closes. It starts behaving like shared infrastructure,” said Mitch Ashley, VP and practice lead, Software Lifecycle Engineering and AI-Native Software Engineering, for The Futurum Group.
Microsoft built first-party adapters for Copilot, Claude, and Codex that translate each agent’s native runtime into the common AHP session model. For DevOps teams standardizing on Copilot, one of the more useful changes is in Claude sessions: you can now mix Anthropic and Copilot models in the same session. The model picker groups both under separate headings, and you choose per turn — models under Anthropic bill against your API key, models under Copilot draw on your Copilot subscription. Previously, switching providers meant reconfiguring the agent host entirely.
VS Code also added an experimental setting, chat.agentHost.allowSignedOutWhenUsable, that lets the Agents window open without a mandatory GitHub sign-in prompt. That prompt used to block anyone whose machine couldn’t reach github.com, or who simply didn’t want to authenticate against GitHub to use an agent they’d already configured through an API key. With the setting enabled, GitHub authentication attaches to individual agents or models rather than gating the entire window. For now, that only works with Claude; Microsoft says support for Copilot with custom model keys and for Codex is coming in a future release.
Developers who want to run the host themselves, rather than relying on VS Code to spin one up automatically, can type “code agent host” in a terminal to start a server on localhost, which is protected by a connection token by default. Adding the –tunnel flag exposes it through a dev tunnel for remote access. If none of this appeals to you yet, nothing forces your hand: sessions created before the Agent Host was enabled continue to run under the old extension-host model, and flipping chat.agentHost.enabled to false reverts to that behavior entirely.
The rest of the update is smaller but still worth knowing about. Sticky scroll now applies to chat prompts, not just code: as you scroll back through a long conversation, the prompt you’ve scrolled past stays pinned at the top so you don’t lose track of which response belongs to which question. You can click it to jump back, or step through prompts with the previous and next buttons beside it. And the integrated browser now auto-refreshes local HTML files when they change on disk, a small fix that removes a manual refresh step developers have been hitting for a while, whether the change came from an agent’s edit or their own save.
Ashley sees the open spec as much a land grab as an engineering decision. “Publishing the protocol as an open spec, alongside LSP and DAP, is Microsoft staking the agent execution surface before rivals do,” he said. “Open beats proprietary only if the adapters for Claude and Codex stay first-class. Buyers should test that promise before committing a stack.”
None of this is a dramatic user-facing overhaul on its own. But the architecture shift underneath it is the more interesting story for anyone tracking where AI-assisted development is headed. By separating the agent host from the editor and publishing the protocol openly, Microsoft is inviting other tools and IDEs to plug into the same session model, rather than keeping agent orchestration locked inside VS Code. That’s a bet that agent sessions are becoming infrastructure in their own right, something teams run, monitor, and reconnect to, rather than a chat window that disappears the moment you close a tab.
For teams already leaning on Copilot or Claude in VS Code, the near-term upside is simpler: fewer forced logins, an easier way to compare models without breaking your workflow, and a chat interface that’s a little less likely to lose your place. The update is rolling out gradually through VS Code’s built-in updater, or developers can trigger it immediately with Check for Updates in the toolbar menu.