Agent isolation "remote" silently runs as a local worktree

Summary

An Agent tool call with isolation: "remote" returned "Async agent launched successfully", but the agent ran on the local machine in a git worktree instead of a cloud session. Nothing in the result, the listing or the notifications said that remote isolation was unavailable or that the call fell back to a local worktree.

Environment

• Claude Code 2.1.283, CLI, macOS (Darwin 25.6.0), zsh
• Model: Opus 5.5
• Date: 25 September 2026

Steps to reproduce

1. In a CLI session inside a git repository with a GitHub remote, call the Agent tool with isolation: "remote" and a background task that edits files and pushes a branch.
2. The tool returns "Async agent launched successfully".
3. Call ListAgents. The agent appears under Subagents as a running local general-purpose agent, and no cloud session is listed.
4. Run git worktree list. A locked worktree at .claude/worktrees/agent-<id> on branch worktree-agent-<id> is present.
5. Stop the agent with TaskStop. Its notification reports task_type as local_agent and names the worktree path and branch.

Expected

The agent runs in a cloud session. If remote isolation is not available in the session, the call fails or states that it fell back to a local worktree.

Actual

The agent ran locally with no indication. A user who closes the machine after such a launch, believing the work runs in the cloud, loses it.