VS Code 1.146 adds an agent Inbox and Fusion in model comparisons, and starts the Local harness countdown

VS Code 1.146, released on 11 November, is mostly about the Agents window. The change that needs action is a deprecation: the Local agent harness is frozen now and will be removed in February 2027.

The Local harness countdown

The Copilot harness has been the default for new agent sessions since VS Code 1.143. Microsoft says it is built on the Copilot SDK, runs sessions through the Agent Host so they keep going in the background, and enforces managed sandbox and permission policies for organizations that the Local harness does not.

From this release the Local harness gets no new features. In three months it disappears, along with vscode.temporaryDefaultToLocalHarness, the enterprise setting added in 1.142 to keep Local as the default. If the harness picker shows “Copilot” when you start a session, you are already on the new one. Microsoft’s transition guide covers custom configurations, continuing old Local conversations, and rollout checks for organizations.

Inbox mode for sessions (experimental)

Turn on sessions.list.inboxEnabled, off by default, and choose Grouping > Inbox Mode in the Agents window. Sessions that need you sit at the top, above Working, Ready to merge, On hold and Done. You can dismiss a session from the Inbox, put it on hold or snooze it. It is a single view across projects, so you stop checking each workspace for a stuck agent.

Model comparison gets Fusion and an agent driver

Compare Models (preview) runs one prompt across several models, scores the results with a judge model and merges the best parts with a synthesizer. In 1.146:

• A judge and synthesizer can now run on chat-only answers, without picking a workspace.
• Copilot Fusion, GitHub’s model router, can be chosen with its effort tiers for an attempt, the judge or the synthesizer.
• An experimental setting, sessions.chat.compareAgents.tools.enabled, lets agents discover models, launch comparisons and summarize results themselves. It is off by default.

Chat windows (preview) also let you pop a chat into its own window with its editors, and those windows come back after a restart. That continues the multi-session work from VS Code 1.140.

Visual Studio 18.12: Bring Your Own Model is GA

On the full IDE side, Visual Studio 2026 version 18.12 shipped on 10 November with Bring Your Own Model generally available. It adds several configurations per provider, a custom-endpoint flow that includes local models, more control over API compatibility and better proxy support. Copilot Chat in 18.12 also moves onto the Copilot SDK, the same base as the VS Code harness above.

Why this matters

Microsoft is putting its editors on one agent engine, the Copilot SDK, and retiring the older path on a fixed date. Teams that pinned the Local harness by policy have until February 2027 to test the Copilot harness. Built-in model comparison with a judge also gives you a cheap way to check a model switch on your own prompts before rolling it out.