---

name: "d3k" description: "d3k assistant for debugging web apps"

d3k Commands

d3k captures browser and server logs in a unified log file. Use these commands:

Viewing Errors and Logs

d3k errors              # Show recent errors (browser + server combined)
d3k errors --context    # Show errors + user actions that preceded them
d3k errors -n 20        # Show last 20 errors

d3k logs                # Show recent logs (browser + server combined)
d3k logs --type browser # Browser logs only
d3k logs --type server  # Server logs only

Other Commands

d3k fix                 # Deep analysis of application errors
d3k fix --focus build   # Focus on build errors

d3k crawl               # Discover app URLs
d3k crawl --depth all   # Exhaustive crawl

Browser Interaction

d3k agent-browser auto-connects to the active session's browser via CDP:

d3k agent-browser open http://localhost:3000/page
d3k agent-browser snapshot -i    # Get element refs (@e1, @e2)
d3k agent-browser click @e2
d3k agent-browser fill @e3 "text"
d3k agent-browser screenshot /tmp/shot.png

To target a different browser, run d3k agent-browser connect <port> first.

Codex Fresh Browser/Profile Startup

Use this workflow when the user asks Codex to start d3k with a fresh browser/profile.

1. Close any stale agent-browser daemon before launching with --profile. Otherwise agent-browser will reuse the existing daemon and print --profile ignored.

   d3k agent-browser close --all
   

2. Start the app through d3k in servers-only mode and keep that command running. In Codex, this is more reliable than asking d3k to launch the browser itself when a fresh profile is required.

   d3k --no-agent --no-skills --servers-only --command "npm run dev -- -H 127.0.0.1 -p 3000" --port 3000 --startup-timeout 90 --no-tui
   

   Adjust the package-manager command and port for the project. Prefer --command over --script when passing framework flags. For npm scripts, put flags after --; otherwise tools like Next.js can interpret the port as a project directory.

3. Verify the server before opening more browser windows:

   curl -I http://127.0.0.1:3000
   

4. Open the fresh profile as a separate browser step:

   d3k agent-browser --profile /tmp/d3k-fresh-profile --headed open http://127.0.0.1:3000
   

5. Sanity-check the opened page:

   d3k agent-browser get title
   d3k agent-browser snapshot -i
   d3k errors
   

Practical rules:

• Prefer 127.0.0.1 for this workflow. If localhost hangs or flips between IPv4/IPv6 behavior, do not keep retrying browser launches.
• If curl -I hangs, the server is wedged even if the port appears occupied; restart the d3k server process before opening a browser.
• In servers-only mode there is no d3k-monitored CDP browser. Use regular d3k agent-browser commands, not d3k cdp-port.
• In sandboxed agent environments, rerun local-network checks and agent-browser opens outside the sandbox when sandbox networking blocks access to 127.0.0.1.

Browser Tool Choice

Use agent-browser for browser work.

Practical rule:

• Need to drive the same monitored browser session: use agent-browser.
• Examples:

d3k agent-browser snapshot -i
d3k agent-browser click @e2

To make d3k prefer one locally when it launches helper browser commands, use:

d3k --browser-tool agent-browser

Fix Workflow

1. d3k errors --context - See errors and what triggered them
2. Fix the code
3. d3k agent-browser open <url> then d3k agent-browser click @e1 to replay
4. d3k errors - Verify fix worked

Creating PRs with Before/After Screenshots

When creating a PR for visual changes, always capture before/after screenshots to show the impact:

1. Before making changes, screenshot the production site:

   d3k agent-browser open https://production-url.com/affected-page
   d3k agent-browser screenshot /tmp/before.png
   

2. After making changes, screenshot localhost:

   d3k agent-browser open http://localhost:3000/affected-page
   d3k agent-browser screenshot /tmp/after.png
   

3. Or use the tooling API to capture multiple routes at once:

   capture_before_after_screenshots(
     productionUrl: "https://myapp.vercel.app",
     routes: ["/", "/about", "/contact"]
   )
   

4. Include in PR description using markdown:

   ### Visual Comparison
   | Route | Before | After |
   |-------|--------|-------|
   | `/` | ![Before](before.png) | ![After](after.png) |
   

   Upload screenshots by dragging them into the GitHub PR description.