Cloud agent error: The execution environment has become unreachable

Where does the bug appear (feature/product)?

Background Agent (GitHub, Slack, Web, Linear)

Describe the Bug

Environment suddenly “stopped working” with an error “The execution environment has become unreachable”. All cloud agent progress is lost. Connection to the workspace does not work and tells “agent’s machine may not be running”. Successive messages to the chat does not help.

Steps to Reproduce

I do not know how to reproduce the bug. It is just an occasion.

Expected Behavior

Environment shall not terminate before cloud agent finishes and pushes to GitHub.

Screenshots / Screen Recordings

Operating System

MacOS

Version Information

Version: 3.7.36
VS Code Extension API: 1.105.1
Commit: 776d1f9d76df50a4e0aeca61819a88e7c1b861e0
Date: 2026-06-13T00:31:56.287Z
Layout: glass
Build Type: Stable
Release Track: Default
Electron: 39.8.1
Chromium: 142.0.7444.265
Node.js: 22.22.1
V8: 14.2.231.22-electron.0
xterm.js: 6.1.0-beta.256
OS: Darwin arm64 25.5.0

For AI issues: which model did you use?

Composer-2.5

For AI issues: add Request ID with privacy disabled

bc-39d0e41a-dff5-4eec-8d37-1809d15b2ca9

Does this stop you from using Cursor

No - Cursor works, but with this issue

More strangely, one hour after the error appeared, the environment seem to revive.

Nothing strange. The environment is UP, but all the cloud agent progress (several hours) is lost.

And the cloud agent switched composer-2.5 to the fast version on its own. This behavior is so upsetting…

This is a known cloud-agent reliability issue we’re actively working on. The agent’s machine can become unreachable mid-run, and in some cases it gets recreated afterward, which is why yours came back about an hour later. Your conversation and history are saved on our side, but file changes made inside the machine that weren’t committed and pushed to GitHub don’t carry over when the machine is recreated. That’s why the in-progress work was lost.

Until the fix lands, the best way to protect long runs is to have the agent commit and push incrementally instead of only at the end. Adding an instruction like “commit and push after each step” to the agent (or as a project rule) means finished work lands on your branch as it goes, so a machine restart costs you the current step at most rather than several hours.

On the model: Composer 2.5 runs in its faster mode by default, so when the run restarted it re-selected that default. It wasn’t a deliberate downgrade. If you want the non-fast variant, pick it explicitly when starting the agent.

I’ll keep tracking the unreachable-environment issue and follow up here once there’s an update.

Thank you! I will surely follow your suggestions!