Open in editor hangs forever when the server runs inside a Docker container reached over SSH #8278

What happened

Open in editor doesn't work. My client is Cursor on a Mac, but the T3 server runs inside a VM-hosted Docker container that I reach with gcloud compute ssh --tunnel-through-iap into the VM followed by docker exec -it t3 bash. When I click Open in Cursor, Cursor launches on my Mac and shows "connecting" but the connection runs forever and never opens the workspace.

Diagnosis

The environment is classified as a remote SSH environment, so open-in-editor takes the remote-links path and hands the OS a deep link instead of exec'ing an editor on the server host:

cursor://vscode-remote/ssh-remote+<host><container-path>

built by buildRemoteOpenUrl (packages/contracts/src/editor.ts). This is confirmed by the server traces containing no shell.openInEditor RPC span for the attempts — in remote-links mode the deep link fires entirely client-side (openRemoteEditorUrl in apps/web/src/remoteOpen.ts) and never reaches the server.

The deep link can't ever connect, because ssh-remote+<host> can only address an SSH host, while the workspace lives inside a Docker container reachable only via ssh <VM> && docker exec:

• Cursor/VS Code Remote-SSH connects to the VM, whose filesystem does not contain the container path (/workspace/repos/<project>), and
• Remote-SSH cannot perform the docker exec hop, so it stalls bringing up the remote server / never lands on the right filesystem.

There is no ssh alias or advertised target that resolveRemoteOpenState / RemoteOpenTargets could carry that would open a containerized backend, so both open-in-editor strategies are dead ends for this topology:

• remote-links → generates a link to the VM, which hangs (this report).
• local-exec → would exec the editor inside the container, which has no editor on PATH, no DISPLAY, and is the wrong machine anyway.

RemoteOpenTargets.resolveTargets() (apps/server/src/environment/RemoteOpenTargets.ts) also advertises nothing here (no sshd on :22, no Tailscale), so even the direct-remote path has no route — but the failure the user sees is the ssh-alias deep link hanging, not the "No SSH route" dead-end.

Root gap: open-in-editor has no notion of a backend that lives inside a container behind an SSH host. A vscode-remote link would need the attached-container/dev-containers authority (…/attached-container+<hex>…) or an equivalent, not ssh-remote+<host>.

Steps to reproduce

1. Run the T3 server inside a Docker container on a remote VM (npx t3 serve inside docker exec -it <container> bash); the VM is reached over SSH (here via gcloud compute ssh --tunnel-through-iap).
2. Connect the T3 desktop app on a Mac to that server as a remote/SSH environment; have Cursor (or any Remote-SSH-capable editor) installed locally.
3. Open a thread in a project whose workspace is a container path (e.g. /workspace/repos/<project>).
4. Click Open-in-editor → Cursor.

Expected: Cursor opens the workspace on the Mac.
Actual: Cursor launches and hangs on "connecting" indefinitely; the workspace never opens. No shell.openInEditor span appears in server.trace.ndjson.

Version

0.0.34 (tag v0.0.34, latest stable)

Environment

Client: macOS, T3 desktop app (Electron), Cursor installed locally. Server: T3 0.0.34 in a Linux x64 Docker container (Node v24.19.0) on a GCP VM, reached via gcloud compute ssh --tunnel-through-iap + docker exec. Server bound to 127.0.0.1:8787.

Evidence

# Server host (the container): none of the routes open-in-editor relies on exist
$ ss -ltnp | grep ':22'        # -> no sshd
(no output)
$ command -v tailscale          # -> absent
$ command -v code cursor codium code-insiders zed   # -> none installed
$ ls /.dockerenv                # -> present (inside docker)
$ echo "$DISPLAY"               # -> empty (headless)

# RemoteOpenTargets therefore advertises nothing (RemoteOpenTargets.ts):
#   if (!sshdListening) return [];

# Clients on record (auth_sessions; credential columns omitted):
#   desktop  MacIntel  Electron   bearer-access-token   <- the failing client
#   desktop  macOS     Chrome     browser-session-cookie
#   mobile   iOS       Safari     browser-session-cookie

# Workspace roots are container paths (projection_projects):
#   /workspace/repos/<project>
#   /root/repos

# No server-side editor launch for the click:
$ grep -c 'shell.openInEditor' server.trace.ndjson*   # -> 0
#   (remote-links deep link fires client-side; never hits the server RPC)

Related issues

#7530 — same open-in-editor local-vs-remote subsystem, but a different failure: there a same-machine browser on a LAN IP is misclassified as remote and dead-ends at a disabled "No SSH route". This report is the opposite end — the environment is correctly remote, a deep link is generated, but ssh-remote+<host> cannot traverse into a Docker container, so it hangs. Not a duplicate.

Fix applied or workaround

Nothing was written to the machine (no DB writes, no source patches). Workaround: use Cursor's Dev Containers: Attach to Running Container — Remote-SSH into the VM, then attach to the t3 container and open the workspace folder. This is the only flow that crosses the docker exec boundary; T3's button cannot drive it.

Filed by

claude (Opus 4.8) via t3 triage