Antithesis Multiverse Debugger

Use the agent-browser skill to interact with the Antithesis multiverse debugger.

Every debugging session should use:

• a fresh, unique SESSION value such as antithesis-debug-$(date +%s)-$$

Use --session-name antithesis so agent-browser manages shared authentication state automatically, while --session "$SESSION" keeps each debugging run isolated from other concurrent agents. Close the unique live session when debugging is complete.

When to use this skill

Use this when the user gives:

• an Antithesis debugging-session URL
• a bug report URL that should be debugged interactively
• a request to inspect container filesystem, runtime state, or events inside Antithesis

For auth and report navigation, use the antithesis-triage skill. It already encodes the right agent-browser session model. This skill handles the debugger itself.

Gathering user input

Before starting, collect the following from the user:

1. Debugger URL (required) — A debugging-session URL like https://TENANT.antithesis.com/debugging-session/....
2. What to investigate — Are they checking filesystem contents? Runtime state? Specific artifacts?
3. Container name (if known) — The name of the container to target. If not provided, the log view or container dropdown will show available containers.

Simplified vs. advanced mode

The debugger has two modes. Prefer simplified mode — it is sufficient for most tasks.

Detecting which mode is active

Different tenants may open the debugger in either mode by default. After injecting the runtime (see references/setup-session.md), check which mode is active:

agent-browser --session "$SESSION" eval \
  "window.__antithesisDebug.getMode()"

Returns "simplified" or "advanced". To switch:

agent-browser --session "$SESSION" eval \
  'window.__antithesisDebug.switchMode("simplified")'

When to escalate to advanced mode

Switch to advanced mode only when you need:

• Branching (moment.branch()) and advancing time
• Event set queries (environment.events.up_to(moment))
• Fault injector state inspection
• Complex multi-cell notebook workflows
• The full JavaScript notebook API

To switch modes, use the three-dot menu (vertical dots icon) in the top-right corner of the debug timeline header. See references/simplified-debugger.md for details.

Reference files

Each reference file covers a specific interaction mode or task. Read the relevant file before performing that task.

Simplified mode (default — start here)

Advanced mode (notebook)

Recommended workflows

Simplified: Run a command in a container

1. Read references/setup-session.md — open the debugger URL
2. Read references/simplified-debugger.md — click a log line to set the moment and container, enter a bash command, press Send, read the output
3. Report findings with concrete evidence

Simplified: Extract a file

1. Read references/setup-session.md — open the debugger URL
2. Read references/simplified-debugger.md — click a log line, toggle "Extract file", enter the file path, press Send
3. Read the download link from the output

Advanced: Programmatic investigation

1. Read references/setup-session.md — open the debugger URL and inject runtime
2. Switch to advanced mode: window.__antithesisDebug.switchMode("advanced")
3. Read references/notebook.md — understand the seeded notebook
4. Read references/common-inspections.md — pick inspection cells
5. Read references/actions.md — authorize actions and read results
6. Report findings with evidence chain

Runtime injection

The JS runtime is required for both simplified and advanced modes. It provides the window.__antithesisDebug API with three namespaces: simplified, notebook, and actions.

Use the browser-side runtime file:

• assets/antithesis-debug.js

Inject it into the current page with:

cat assets/antithesis-debug.js \
  | agent-browser --session "$SESSION" eval --stdin

Injecting the file registers methods on window.__antithesisDebug. Call those methods with agent-browser eval.

Method call examples:

# Simplified mode
agent-browser --session "$SESSION" eval \
  'window.__antithesisDebug.simplified.runCommand("ls -la /")'

# Advanced mode
agent-browser --session "$SESSION" eval \
  "window.__antithesisDebug.notebook.getSource()"

agent-browser eval awaits Promises automatically, so async and sync methods use the same call pattern.

If window.__antithesisDebug is missing, inject assets/antithesis-debug.js and retry the method call.

Do not run method calls in parallel with agent-browser open, navigation, or any other command that can replace the page. Wait until the target page is settled before starting eval calls. Run queries sequentially; mutations will interfere with each other if launched in parallel.

After every open call or any interaction that may navigate or replace the page, first confirm the browser has landed on the debugger page, then inject assets/antithesis-debug.js and call the appropriate waitForReady() before running other methods.

Page loading checks

After navigation, inject the runtime, then call the appropriate waitForReady:

# Simplified mode
agent-browser --session "$SESSION" eval \
  "window.__antithesisDebug.simplified.waitForReady()"

# Advanced mode
agent-browser --session "$SESSION" eval \
  "window.__antithesisDebug.notebook.waitForReady()"

Both poll for up to 60 seconds and return { ok, ready, attempts, waitedMs }. On timeout, the result also includes details.

One-shot probes:

agent-browser --session "$SESSION" eval \
  "window.__antithesisDebug.simplified.loadingFinished()"

agent-browser --session "$SESSION" eval \
  "window.__antithesisDebug.notebook.loadingFinished()"

Diagnostics:

agent-browser --session "$SESSION" eval \
  "window.__antithesisDebug.simplified.loadingStatus()"

agent-browser --session "$SESSION" eval \
  "window.__antithesisDebug.notebook.loadingStatus()"

General guidance

• Start in simplified mode. The simplified debugger handles most debugging tasks. Only switch to advanced mode when you specifically need the notebook API.
• Defer to antithesis-triage for auth. If the debugger URL requires authentication, use the antithesis-triage skill's references/setup-auth.md for the interactive login flow. Use the same --session-name antithesis so auth state is shared.
• Use disposable sessions. Generate a unique SESSION for each debugging run, pair it with the shared --session-name antithesis, and agent-browser --session "$SESSION" close when you finish or abort.
• Run commands sequentially. In both modes, wait for each command to complete before sending the next one.
• Do not fabricate container names. Use the container dropdown (simplified) or environment.containers.list({moment}) (advanced) to determine valid container names.
• Present results clearly. When reporting filesystem contents, include the full path and listing. When reporting artifact searches, include what was found and what was not.

Advanced mode only

• Inject the runtime after navigation. After every open call or page reload, inject assets/antithesis-debug.js and call notebook.waitForReady() before the next method call.
• Retry missing-runtime errors by reinjecting. If a command fails because window.__antithesisDebug is undefined or missing, inject the runtime and rerun the same method.
• Authorize actions one at a time. Each bash\...`` cell needs explicit authorization. Read the result before injecting the next cell.

Self-Review

Before declaring this skill complete, review your work against the criteria below. This skill's output is conversational (summaries, evidence, analysis), so the review should happen in your current context. Re-read the guidance in this file, then systematically check each item below against the answers and analysis you produced.

Review criteria:

• Every filesystem listing or artifact search was extracted from actual debugger output, not inferred or assumed
• The evidence chain is clear: which commands were run, what they returned, and what conclusions follow
• The summary distinguishes between what the debugger shows and what you interpret or recommend
• The browser session was closed at the end of the debugging run