Skill: Colab Session Operator

Operate Google Colab environments via the colab CLI: provision GPU/TPU sessions, run Python/shell on the VM, sync files, and capture work as notebooks.

Installation

If the user does not already have the colab tool installed, it can be acquired by running uv tool install google-colab-cli or pip install google-colab-cli.

When to activate

• Creating or managing TPU/GPU sessions.
• Running Python or shell on a remote Colab VM.
• Syncing files between local and remote.
• Automating environment setup (packages, auth, Drive).
• Exporting session history as a Jupyter notebook.

Mental model (read this first)

• A session == a live Jupyter kernel on a rented VM. colab new allocates a billable VM; colab stop releases it. Nothing reclaims it automatically except a 24h keep-alive cap, so an unstopped session burns compute units indefinitely.
• Kernel state PERSISTS across colab exec / colab repl calls in the same session. Each invocation reattaches to the same kernel (the kernel ID is cached in local state) and only closes the websocket on exit — it does not shut the kernel down. So imports, variables, and defined functions survive between separate colab exec commands. Build up state incrementally; don't re-import everything each call. (colab stop and colab restart-kernel are what actually reset it.)
• Default working directory is /content. Every exec/repl/run cds there first; prefer absolute paths (/content/...) for file work. For colab ls/rm/upload/download, absolute /content/... paths work and the default ls path is content (VM root).
• colab is fire-and-forget. Each command authenticates, does one thing, and exits. A detached background daemon (spawned by colab new) handles keep-alive; you don't manage it.

Authentication (the #1 thing that blocks agents)

• The global flag is --auth={adc,oauth2} and the default is adc (Application Default Credentials). It must come before the subcommand: colab --auth=adc new -s x.
• ADC setup (most reliable for headless/agent use). The Colab backends need a specific scope set, so re-mint ADC with all four scopes:

  gcloud auth application-default login \
    --scopes=openid,\
  https://www.googleapis.com/auth/cloud-platform,\
  https://www.googleapis.com/auth/userinfo.email,\
  https://www.googleapis.com/auth/colaboratory
  

  Why all four: userinfo.email (session backend colab.research.google.com, else 401), colaboratory (RuntimeService colab.pa.googleapis.com keep-alive, else 403), openid+cloud-platform (mandated by gcloud itself; it rejects scope lists missing cloud-platform).
• oauth2 setup: colab --auth=oauth2 <anything> triggers a browser consent flow on first use (token cached at ~/.config/colab-cli/token.json). Requires a client config at ~/.colab-cli-oauth-config.json (or -c PATH). The browser step means it usually needs a human; prefer ADC for agents.
• Verify auth in one shot: colab sessions (read-only, lists server assignments) or colab whoami (hidden debug command: prints the active email, scopes, audience, and expiry). When any call 403s against colab.pa.googleapis.com, the cause is almost always a missing scope — colab whoami shows it instantly.
• colab new pre-flights the keep-alive RPC right after allocating. If your token lacks the colaboratory scope it unassigns the fresh VM (so you don't leak a billable assignment) and prints the exact remediation. Follow that message rather than retrying blindly.
• Do NOT confuse colab auth with CLI authentication. colab auth injects VM-side GCP credentials into the running kernel (so notebook code can call BigQuery/GCS); it is orthogonal to how the CLI itself authenticates. Never suggest "run colab auth" to fix a CLI 401/403 — that's a scope/identity problem fixed via the gcloud command above.

Workflow

Provision

• colab new -s <name> (CPU). Add --gpu A100 or --tpu v6e1 for accelerators. Always pass -s <name> — an omitted name is auto-generated as a random 6-hex string, which makes later commands ambiguous.
• Supported --gpu: T4, L4, G4, H100, A100. Supported --tpu: v5e1, v6e1.
• Gotcha: an unrecognized --gpu value silently falls back to A100 (which then usually fails the next step). A 400 on colab new with an accelerator means no quota/entitlement for it on this account — fall back to --gpu T4 or omit the flag for CPU.
• Accelerator availability is tier-gated; most accounts can only get CPU. Don't assume a GPU/TPU will allocate.

Execute

• Preferred: colab exec -s <name> -f <script.py> runs a local script on the remote VM (read locally, sent to the kernel — no manual upload needed).
• Piped code: echo "print(1)" | colab exec -s <name> or cat script.py | colab exec -s <name>.
• Notebooks: colab exec -s <name> -f nb.ipynb runs each code cell and writes results to <basename>_output.ipynb next to the input. A # @title Foo first line labels the cell in progress output.
• Plots/images: PNG/JPEG outputs are intercepted. Use --output-image <path> on exec/repl to save to a known location (otherwise a temp path is printed). Inline terminal-image escapes are auto-suppressed when stdout isn't a TTY, so piped/captured output stays clean.
• Shell: echo "cmd" | colab console -s <name> for batch shell. Console wraps bash in tmux, so even piped output contains terminal-control bytes — filter with grep -a for a specific line. exec is faster when you don't need a real shell.
• Never run colab repl, colab console, colab auth, or colab drivemount interactively from an agent — they expect a TTY and will hang. repl/console accept piped stdin and exit on EOF; auth/drivemount genuinely require a human at the terminal.

Ephemeral one-shot jobs (colab run)

• colab run [--gpu T4] [--tpu v6e1] [--keep] [-s NAME] script.py [args...] = new + exec + stop in one command. It provisions a fresh VM, runs the script with sys.argv and __name__ == "__main__" set like native python script.py args, then tears the VM down (unless --keep).
• Exit codes propagate: an uncaught exception or sys.exit(N) in the script makes colab run exit non-zero (CPython semantics: sys.exit()/sys.exit(0) → 0, sys.exit(N) → N, sys.exit("msg") → 1).
• Stream separation: colab run writes its own [colab] ... chatter to stderr and the script's output to stdout — so colab run job.py > out.txt captures only the script's stdout. (colab exec streams the script's stdout/stderr live to your stdout/stderr.)
• Works as a shebang: #!/usr/bin/env -S colab run --gpu T4 makes a chmod +x'd .py a self-contained "rent a GPU, run, clean up" script. After editing CLI behavior, reinstall before testing shebangs — they resolve colab via $PATH, not the editable install.
• A nonexistent script path exits non-zero before allocating a VM (no wasted compute).

Automate

• colab auth -s <name> — VM-side GCP creds, needed before in-VM GCS/BigQuery calls (interactive; not agent-runnable).
• colab drivemount -s <name> [PATH] — mounts Drive at /content/drive by default (interactive; not agent-runnable).
• colab install -s <name> pkg1 pkg2 — installs via uv pip install --system, falling back to pip. Also colab install -s <name> -r requirements.txt.

Inspect & report

• colab help (or colab help <cmd>) lists/explains commands; the listing is alphabetical.
• colab sessions lists server-side assignments and auto-prunes stale local entries. Orphans with no local record show as [?].
• colab status [-s <name>] shows hardware, IDLE/BUSY, and last execution.
• colab log -s <name> [-n 20] [-t TYPE] shows recent structured events; invaluable when a task fails (keep-alive errors carry the raw response_body).
• colab log -s <name> -o summary.ipynb exports the session as a notebook (also .md, .txt, .jsonl by suffix).
• colab url -s <name> prints a browser URL that attaches the Colab web UI to your existing CLI session instead of allocating a new VM (add --open to launch it).
• colab skill / colab readme print this skill and the README (handy for self-discovery).

Safety

• Always colab stop -s <name> when done — idle VMs burn compute units. colab run (without --keep) self-cleans even if the script errors.
• Local state lives in ~/.config/colab-cli/sessions.json (settings in settings.json, history in history/*.jsonl). Don't edit by hand.
• Isolate parallel/agent runs with the global --config <path> flag to point session state at a scratch file (e.g. colab --config /tmp/agent.json new -s job). The keep-alive daemon inherits --auth and --config automatically.

Recovery

• "Session not found" / 404 / 401 on exec: the backend pruned the VM. colab exec/repl detect this and clean up local state automatically — run colab sessions and re-create with colab new.
• Execution timeout or wedged kernel: colab restart-kernel -s <name> (keeps the VM, resets the kernel), or colab stop then colab new.
• Keep-alive daemon died (colab log shows keep_alive_stopped reason=consecutive_4xx_errors): almost always the missing colaboratory scope — re-auth per the Authentication section.