Document Dev Container Agent Host sessions

[ntrogh]

Product change

• Source: Agent Host: Run Dev Containers on new worktrees vscode#333736, Agent Host: Gate Dev Container worktree sessions vscode#333782
• Merged: 2026-09-01 UTC

The Agents window can experimentally start an Agent Host session inside a repository's Dev Container. This gives the agent the project's containerized tools and dependencies instead of running directly on the local host.

Why the docs need an update

The agent harness and Agents window documentation describes folder and worktree isolation, but does not explain the Dev Container execution option, how to enable it, or its prerequisites.

Suggested documentation

• docs/agents/run/agent-harnesses.md: add Dev Container as an experimental execution option for Agent Host sessions, including setup and limitations.
• docs/agents/run/agents-window.md: explain where the Dev Container checkbox appears when starting an eligible session.

Details to verify

• Enable the option with the application-scoped chat.agentHost.devContainer.enabled setting. It is experimental and defaults to false.
• The option is currently available only in the Agents window.
• Docker CLI must be available on PATH, and the selected local folder must contain .devcontainer/devcontainer.json or .devcontainer.json.
• Combining Dev Container execution with New Worktree is controlled by the hidden, default-off chat.agentHost.devContainer.worktree.enabled experiment and should not be described as generally available.

Acceptance criteria

• Users can determine how to enable and start an Agent Host session in a Dev Container.
• The docs state the setting default, Agents window scope, Docker and configuration-file prerequisites, and current worktree limitation.
• The agent harness comparison remains consistent with the Agents window workflow.