React Devtools Agent Skill

React DevTools CLI for AI agents. Use when the user asks you to debug a React or React Native app at runtime, inspect component props/state/hooks, diagnose render performance, profile re-renders, find slow components, or understand why something re-renders. Triggers include "why does this re-render", "inspect the component", "what props does X have", "profile the app", "find slow components", "debug the UI", "check component state", "the app feels slow", or any React runtime debugging task.

6k tokens

context cost

the whole folder, loaded on every use

files

instructions only

copies elsewhere

how many repositories repackaged it

236

stars on the repo

on the repository, not the skill itself

Install

one command, takes just this skill from the repository

npx skills add https://github.com/callstackincubator/agent-react-devtools --skill react-devtools

What comes with it

13 993 bytes besides the instruction

references/commands.md

references/profiling-guide.md

references/setup.md

What it tells the agent to use

found in the instruction text

Bash runs shell commands — read the instruction before connecting

The instruction itself

19 sections, as written by the author

agent-react-devtools

CLI that connects to a running React or React Native app via the React DevTools protocol and exposes the component tree, props, state, hooks, and profiling data in a token-efficient format.

Core Workflow

Ensure connection — check agent-react-devtools status. If the daemon is not running, start it with agent-react-devtools start. Use agent-react-devtools wait --connected to block until a React app connects.
Inspect — get the component tree, search for components, inspect props/state/hooks.
Profile — start profiling, trigger the interaction (or ask the user to), stop profiling, analyze results.
Act — use the data to fix the bug, optimize performance, or explain what's happening.

Essential Commands

Daemon

agent-react-devtools start              # Start daemon (auto-starts on first command)
agent-react-devtools stop               # Stop daemon
agent-react-devtools status             # Check connection, component count, last event
agent-react-devtools wait --connected   # Block until a React app connects
agent-react-devtools wait --component App # Block until a component appears

Component Inspection

agent-react-devtools get tree           # Full component hierarchy (labels: @c1, @c2, ...)
agent-react-devtools get tree --depth 3 # Limit depth
agent-react-devtools get component @c5  # Props, state, hooks for a specific component
agent-react-devtools find Button        # Search by display name (fuzzy)
agent-react-devtools find Button --exact # Exact match
agent-react-devtools count              # Count by type: fn, cls, host, memo, ...
agent-react-devtools errors             # List components with errors or warnings

Performance Profiling

agent-react-devtools profile start              # Start recording
agent-react-devtools profile stop               # Stop and collect data
agent-react-devtools profile slow               # Slowest components by avg render time
agent-react-devtools profile slow --limit 10    # Top 10
agent-react-devtools profile rerenders          # Most re-rendered components
agent-react-devtools profile report @c5         # Detailed report for one component
agent-react-devtools profile timeline --limit 10                        # First 10 commits (use --limit; uncapped can dump 300+ lines)
agent-react-devtools profile timeline --limit 10 --offset 10           # Next 10 (pagination)
agent-react-devtools profile timeline --sort duration --limit 5        # Top 5 most expensive commits
agent-react-devtools profile timeline --sort timeline --limit 5        # Explicit chronological order (same as default)
agent-react-devtools profile commit 3           # Detail for commit #3
agent-react-devtools profile export profile.json # Export as React DevTools Profiler JSON
agent-react-devtools profile diff before.json after.json  # Compare two exports

Understanding the Output

Component Labels

Every component gets a stable label like @c1, @c2. Use these to reference components in follow-up commands:

@c1 [fn] App
├─ @c2 [fn] Header
├─ @c3 [fn] TodoList
│  ├─ @c4 [fn] TodoItem key=1
│  └─ @c5 [fn] TodoItem key=2
└─ @c6 [host] div

Type abbreviations: fn = function, cls = class, host = DOM element, memo = React.memo, fRef = forwardRef, susp = Suspense, ctx = context.

Components with errors or warnings show annotations: ⚠2 = 2 warnings, ✗1 = 1 error. Use agent-react-devtools errors to list only affected components.

Inspected Component

@c3 [fn] TodoList
props:
  items: [{"id":1,"text":"Buy milk"},{"id":2,"text":"Walk dog"}]
  onDelete: ƒ
state:
  filter: "all"
hooks:
  useState: "all"
  useMemo: [...]
  useCallback: ƒ

ƒ = function value. Values over 60 chars are truncated.

Profiling Output

Slowest (by avg render time):
  @c3 [fn] ExpensiveList  avg:12.3ms  max:18.1ms  renders:47  causes:props-changed  changed: props: items, filter
  @c4 [fn] TodoItem  avg:2.1ms  max:5.0ms  renders:94  causes:parent-rendered, props-changed  changed: props: onToggle

Render causes: props-changed, state-changed, hooks-changed, parent-rendered, force-update, first-mount.

When specific changed keys are available, a changed: suffix shows exactly which props, state keys, or hooks triggered the render (e.g. changed: props: onClick, className state: count hooks: #0).

Common Patterns

Wait for the app to connect after a reload

agent-react-devtools wait --connected --timeout 10
agent-react-devtools get tree

Use this after triggering a page reload or HMR update to avoid querying empty state.

Diagnose slow interactions

agent-react-devtools profile start
# User interacts with the app (or use agent-browser to drive the UI)
agent-react-devtools profile stop
agent-react-devtools profile slow --limit 5
agent-react-devtools profile rerenders --limit 5

Then inspect the worst offenders with get component @cN and profile report @cN.

Browse a long timeline in chunks

agent-react-devtools profile timeline --limit 20               # commits 0–19
agent-react-devtools profile timeline --limit 20 --offset 20   # commits 20–39
agent-react-devtools profile timeline --offset 30 --limit 10   # skip warm-up, show 30–39

Use profile commit <N> to drill into a specific commit once you spot a spike.

Find a component and check its state

agent-react-devtools find SearchBar
agent-react-devtools get component @c12

Verify a fix worked

agent-react-devtools profile start
# Repeat the interaction
agent-react-devtools profile stop
agent-react-devtools profile slow --limit 5
# Compare render counts and durations to the previous run

Using with agent-browser

When using agent-browser to drive the app while profiling or debugging, you must use headed mode (--headed). Headless Chromium does not execute ES module scripts the same way as a real browser, which prevents the devtools connect script from running properly.

agent-browser --session devtools --headed open http://localhost:5173/
agent-react-devtools status  # Should show 1 connected app

Important Rules

Labels reset when the app reloads or components unmount/remount. After a reload, use wait --connected then re-check with get tree or find.
status first — if status shows 0 connected apps, the React app is not connected. The user may need to run npx agent-react-devtools init in their project first.
Headed browser required — if using agent-browser, always use --headed mode. Headless Chromium does not properly load the devtools connect script.
Profile while interacting — profiling only captures renders that happen between profile start and profile stop. Make sure the relevant interaction happens during that window.
Use --depth on large trees — a deep tree can produce a lot of output. Start with --depth 3 or --depth 4 and go deeper only on the subtree you care about.

References

| File | When to read |

|------|-------------|

| commands.md | Full command reference with all flags and edge cases |

| profiling-guide.md | Step-by-step profiling workflows and interpreting results |

| setup.md | How to connect different frameworks (Vite, Next.js, Expo, CRA) |

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How to use it

Copy the folder

Take callstackincubator/react-devtools from the repository into ~/.claude/skills for personal use, or into .claude/skills inside a project.

Check the name does not clash

The agent identifies a skill by the name field in its header. Two skills with the same name cannot sit side by side — one of them will be ignored.

Install what it needs

The instructions reference npx. Without those the skill loads but fails at the first command.