Browser Terminal Use Agent

Browser Terminal Use Agent

Overview

Use this skill to drive Browser Terminal Use as an agent loop runner: issue commands locally, execute in a bound browser terminal tab, stream output, and use remote exit codes as the control signal for next actions.

Read references/runbook.md for concrete command templates and troubleshooting mappings.

Workflow

1. Start or verify daemon connectivity.
2. Ensure extension and terminal tab are ready, then prove the tab is actually bound with a short smoke probe.
3. Run iterative command loops with explicit timeout and request id.
4. Diagnose failures and recover quickly.
5. Enable token hardening when security requirements increase.

1) Start Or Verify Daemon Connectivity

Use global commands:

browterm-daemon --host 127.0.0.1 --port 17373
browterm health

Start daemon on localhost and verify health before running commands.

curl http://127.0.0.1:17373/v1/health

Treat daemon health failure as a hard blocker for agent loops.

2) Ensure Extension And Tab Readiness

Load extension from extension/ in Chrome developer mode. Configure extension bridge URL as ws://127.0.0.1:17373/extension. Bind the browser terminal tab by clicking extension action once. Refresh the target terminal tab after extension reload.

Do not treat browterm health with extensionConnected: true as sufficient evidence that a usable terminal tab exists. Prove tab attachment with a trivial bounded command before any long-running request:

browterm exec --request-id req-tab-smoke --timeout-ms 15000 --json "printf bt-ready"

If the smoke probe does not return the expected sentinel text quickly, stop and treat it as a hard blocker. Common causes are:

• no browser terminal tab is open
• the tab is open but not bound to the extension
• the extension is connected but attached to the wrong tab
• output is only browser or extension telemetry rather than command output

3) Run Iterative Agent Loops

Use exec as the default operation and keep each step deterministic.

• Provide --timeout-ms for bounded execution.
• Provide --request-id so cancellation and traceability stay explicit.
• Prefer --json when post-processing output in automation.
• Use the command exit code as the branching condition for next agent step.

Example:

browterm exec --request-id req-env-check --timeout-ms 120000 --json "uname -a"

Hang Detection Rules

• Run a short smoke probe first. Never start a long remote test until that probe succeeds.
• If a trivial probe stays queued, times out, or produces no command output within its timeout window, cancel it and raise an error immediately.
• If output consists only of browser or extension telemetry and not the command's expected stdout, treat that as "tab not actually attached" and fail early.
• For longer commands, do not cancel just because stdout is quiet.
• If a longer command appears hung, first check daemon health and whether a browser terminal tab is still bound.
• Only treat the run as a tab-binding or transport failure when health or tab checks fail, or when output shows only browser or extension telemetry instead of terminal output.

Quote-Safe Command Rules

These are hard rules, not suggestions. If a command is not quote-safe and stable, do not run it through browterm exec. Rewrite it first.

• Never pass multiline commands to browterm exec.
• Never use heredoc (<<EOF) inside browterm exec command strings.
• Never send commands with unbalanced or hard-to-audit quoting.
• Never rely on shell state that is not made explicit in the same command string.
• Always prefer one-line commands joined by ; or &&.
• Always rewrite fragile commands into quote-safe, deterministic forms before execution.
• For generated files, use printf '%s\n' ... > file instead of heredoc.
• For JSON payload files, prefer jq -n '...' > file.
• If the quoting still looks brittle after one rewrite, stop using inline shell and generate a short script with printf '%s\n' ... > /tmp/<name>.sh; bash /tmp/<name>.sh.

Safe patterns:

browterm exec --request-id req-basic --timeout-ms 120000 --json "hostname; whoami; pwd"

browterm exec --request-id req-json --timeout-ms 120000 --json \
  "jq -n '{input_ids:[1,2,3],stream:false}' > /tmp/req.json; cat /tmp/req.json"

browterm exec --request-id req-script --timeout-ms 120000 --json \
  "printf '%s\n' '#!/usr/bin/env bash' 'set -euo pipefail' 'echo ok' > /tmp/bt_step.sh; bash /tmp/bt_step.sh"

Avoid:

# Avoid multiline/heredoc payloads inside browterm exec
browterm exec --request-id bad --timeout-ms 120000 --json \
  'cat >/tmp/x <<EOF
line1
EOF'

# Avoid nested or ambiguous quoting that is difficult to audit quickly
browterm exec --request-id bad --timeout-ms 120000 --json \
  "python -c 'print(\"unterminated or fragile shell composition here)\""

Cancel stuck or obsolete work by request id:

browterm cancel req-env-check

4) Diagnose And Recover

When execution fails, check in order:

1. Daemon process and /v1/health.
2. Extension options bridge URL.
3. Bound tab status (rebind if needed).
4. Retry command with debug logging on daemon.

Use error-specific playbooks in references/runbook.md.

5) Enable Optional Token Hardening

Keep default local setup tokenless for fastest setup. Enable --token on daemon and CLI for stricter local security boundaries. When enabled, keep daemon, extension options, and CLI token values identical.

Execution Principles

• Keep one active command per loop step.
• Prefer short, composable commands over long opaque scripts.
• Do not execute a command string you cannot quickly prove is quote-safe and stable.
• Persist request ids in logs for auditability.
• Re-run with focused probes before broad retries.

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