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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

d3k find-component "nav"  # Find React component source

Browser Interaction

First run d3k cdp-port to get the port number, then use it directly in all browser commands:

d3k cdp-port                                          # Returns e.g. 9222
d3k agent-browser --cdp 9222 open http://localhost:3000/page
d3k agent-browser --cdp 9222 snapshot -i    # Get element refs (@e1, @e2)
d3k agent-browser --cdp 9222 click @e2
d3k agent-browser --cdp 9222 fill @e3 "text"
d3k agent-browser --cdp 9222 screenshot /tmp/shot.png

Browser Tool Choice

Use the browser tool that matches the task:

• agent-browser
  • Default choice.
  • Best for generic web apps and for driving the exact headed browser session d3k is already monitoring.
  • Use it when you need snapshot, ref-based click, fill, or to reproduce what the user sees in the monitored tab.
• next-browser
  • Next.js-specific tool.
  • Best for Next/React introspection: tree, errors, logs, routes, project, and related Next dev-server diagnostics.

Practical rule:

• Need to drive the same monitored browser session: use agent-browser.
• Need Next.js component-tree or Next-specific diagnostics: use next-browser.

Examples:

# Same monitored browser session
d3k agent-browser --cdp 9222 snapshot -i
d3k agent-browser --cdp 9222 click @e2

# Next.js-specific inspection
d3k next-browser open http://localhost:3000
d3k next-browser tree
d3k next-browser errors
d3k next-browser logs

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

d3k --browser-tool agent-browser
d3k --browser-tool next-browser

Fix Workflow

1. d3k errors --context - See errors and what triggered them
2. Fix the code
3. Run d3k cdp-port to get the port, then d3k agent-browser --cdp <port> open <url> then 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 (run d3k cdp-port first to get the port):

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

2. After making changes , screenshot localhost:

   d3k agent-browser --cdp <port> open http://localhost:3000/affected-page d3k agent-browser --cdp <port> 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.

Weekly Installs

106

Repository

vercel-labs/dev3000

GitHub Stars

1.1K

First Seen

Feb 8, 2026

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Installed on

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