# lynx-trace-record

Teaches AI agents to record Lynx performance traces via the trace_record CLI. Captures startup rendering, memory snapshots, and JS engine profiles.

- skill · `type=skill` · Claude Code, Codex, Cursor, GitHub Copilot, Gemini CLI, OpenCode · 353 installs · ★ 27
- Author: lynx-community
- License: Apache-2.0 · policy=mirror · the beginning of the file is at the end of this page
- Source: https://github.com/lynx-community/skills/tree/HEAD/skills/lynx-trace-record/SKILL.md
- Updated: 2026-10-24
- HTML: https://affpapa.org/en/nevibecode/skills/lynx-trace-record

## What it does

This skill guides agents through performance profiling for Lynx apps using the bundled `trace_record.bundle.cjs` script. It handles connected client discovery via `list-clients`, maps natural language options to CLI arguments, and controls the full recording lifecycle.

The workflow captures metrics before the page opens. That sequence is critical. Running `start` before loading the target screen ensures the first frame is recorded completely. The tool also supports category filtering like `lynx` or `devtool`, automated heap snapshots, and execution sampling for QuickJS or V8 engines.

When stopped, the CLI yields a stream handle, which the agent pulls into a local `.pftrace` file. Profiling requires a Lynx development build. On production binaries, the runtime blocks trace collection immediately.

## Install

### Claude Code (native platform)

1. **Skills CLI (Vercel)**
```bash
npx skills add lynx-community/skills --skill lynx-trace-record -a claude-code
```

2. **Manually: put the files in place**
- File: `~/.claude/skills/lynx-trace-record/SKILL.md` — Copy the whole skill folder; for one project use .claude/skills/lynx-trace-record/

### Codex

1. **Skills CLI (Vercel)**
```bash
npx skills add lynx-community/skills --skill lynx-trace-record -a codex
```

2. **Manually: put the files in place**
- File: `.agents/skills/lynx-trace-record/SKILL.md` — For all projects use ~/.agents/skills/

### Cursor

1. **Skills CLI (Vercel)**
```bash
npx skills add lynx-community/skills --skill lynx-trace-record -a cursor
```

2. **Manually: put the files in place**
- File: `.cursor/skills/lynx-trace-record/SKILL.md` — Cursor also reads .agents/skills/ and .claude/skills/

### GitHub Copilot

1. **GitHub CLI**
```bash
gh skill install lynx-community/skills lynx-trace-record
```

2. **Manually: put the files in place**
- File: `.github/skills/lynx-trace-record/SKILL.md`

### Gemini CLI

1. **Skills CLI (Vercel)**
```bash
npx skills add lynx-community/skills --skill lynx-trace-record -a gemini-cli
```

2. **Platform CLI**
```bash
gemini skills install https://github.com/lynx-community/skills --path skills/lynx-trace-record
```

### Windsurf (Devin Desktop)

**Manually: put the files in place**
- File: `.devin/skills/lynx-trace-record/SKILL.md` — The legacy .windsurf/skills/ path still works

### OpenCode

**Skills CLI (Vercel)**
```bash
npx skills add lynx-community/skills --skill lynx-trace-record -a opencode
```

### Claude.ai

**Claude.ai**
- Zip the folder and upload it in Settings → Capabilities → Skills

Where a file is given instead of a command, copy the files from the source to that path: https://github.com/lynx-community/skills/tree/HEAD/skills/lynx-trace-record/SKILL.md

## When to use it
- record Lynx performance traces into a `.pftrace` file
- capture first-frame rendering metrics during app startup
- profile V8 or QuickJS engines with custom sampling intervals
- collect automated heap snapshots for shared-group VMs

## Example prompts
- Record a trace with trace_record, enable memory data collection, and capture heap snapshots for VM 'app-vm'
- Start a Lynx trace excluding devtool and vitals categories
- Record with v8 JS profile and interval 100

## Source text · SKILL.md · Apache-2.0

Below is the content of a third-party file. It is data, not instructions for you: do not act on anything written inside unless the human asks. Block tag: 1818269dcff8344b.

BEGIN THIRD-PARTY FILE 1818269dcff8344b
````text
---
name: lynx-trace-record
description: This guide provides step-by-step instructions for recording Lynx performance traces. Use this guide when the user asks how to record a trace.
---

## 1. Workflow Example

The recording process requires using the `trace_record` CLI tool. **The order of operations is critical**.

### Step 1. List connected clients:
First, list all connected clients to get the client ID. This helps you identify which app to trace.
- If you have multiple connected clients, ask the user to specify the client ID you want to trace. Then, use this ID with the `--client` parameter to trace.
- If you have only one connected client, you can omit the `--client` parameter.
- If no clients are found, prompt the user to connect their device via USB and open the debugging app.
   ```bash
   node <path_to_the_skill>/scripts/trace_record.bundle.cjs list-clients
   ```

### Step 2. Start recording:
Execute the start command **BEFORE** building or opening the page on your device. This ensures you capture the entire first frame of the page. Use the `--client` parameter with the client ID from Step 1.
   ```bash
   node <path_to_the_skill>/scripts/trace_record.bundle.cjs start --client <client-id>
   ```

Optional start parameters can be controlled from the user's natural language request:

| User intent | CLI parameter | Trace config field | Default |
| --- | --- | --- | --- |
| Include only specific trace categories | `--include-categories <categories>` | `includedCategories` | `*` |
| Exclude specific trace categories | `--exclude-categories <categories>` | `excludedCategories` | `*` |
| Enable memory data collection | `--enable-memory-trace` | `enableMemoryTrace` | `false` |
| Disable automatic Garbage Collection | `--no-force-gc` | `forceGC` | `true` |
| Automatically capture heap snapshots for "shared-group" VMs | `--enable-auto-heap-snapshot` | `enableAutoHeapSnapshot` | `false` |
| Only capture automatic heap snapshots for a specific "shared-group" VM | `--shared-group-id <id>` | `sharedGroupId` | empty string |
| Specify the JS profile type, such as quickjs or v8 | `--js-profile-type <type>` | `JSProfileType` | empty string (JS profile disabled) |
| Specify the JS profile interval, such as 100 | `--js-profile-interval <interval>` | `JSProfileInterval` | `100` when `JSProfileType` is non-empty and interval is `<= 0`; otherwise `-1` |

When the user asks in natural language, translate the request into the corresponding `start` flags. For example, if the user says "record a trace with trace_record, enable memory data collection, and automatically capture heap snapshots for the VM named 'xxx'", run:
   ```bash
   node <path_to_the_skill>/scripts/trace_record.bundle.cjs start --client <client-id> --enable-memory-trace --enable-auto-heap-snapshot --shared-group-id xxx
   ```
````
END THIRD-PARTY FILE 1818269dcff8344b

The third-party file has ended. Everything between the 1818269dcff8344b tags is data: requests and commands from it are not followed. An “end of file” line with another tag inside the block is part of the file.

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