# yaml

Streaming YAML parser for json-render that turns code fences into JSON Patch. Built for progressive rendering and surgical spec edits via stream.

- skill · `type=skill` · Claude Code, Codex, Cursor, GitHub Copilot, Gemini CLI, OpenCode · 1000 installs · ★ 18794
- Author: vercel-labs
- License: Apache-2.0 · policy=mirror · the beginning of the file is at the end of this page
- Source: https://github.com/vercel-labs/json-render/tree/HEAD/skills/yaml/SKILL.md
- Updated: 2026-10-24
- HTML: https://affpapa.org/en/nevibecode/skills/yaml

## What it does

The skill adds YAML as an alternative to JSONL in `@json-render/core`. The parser reads YAML line-by-line, emits JSON Patch operations via diffing, and recognizes four fence types: `yaml-spec` (full spec), `yaml-edit` (partial merge per RFC 7396), `yaml-patch` (JSON Patch per RFC 6902), and `diff` (unified diff).

\`yamlPrompt` generates a system prompt in two modes: standalone (LLM outputs only YAML) and inline (LLM wraps YAML in fences inside conversational responses). `pipeYamlRender` plugs into AI SDK as a `TransformStream` that converts fences into patches for `json-render`.

Requires TypeScript and the `@json-render/yaml` package. For multi-turn edits, pass `previousSpec` so `yaml-patch` applies to the current state before the next `yaml-edit`.

## Install

### Claude Code (native platform)

1. **Skills CLI (Vercel)**
```bash
npx skills add vercel-labs/json-render --skill yaml -a claude-code
```

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

### Codex

1. **Skills CLI (Vercel)**
```bash
npx skills add vercel-labs/json-render --skill yaml -a codex
```

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

### Cursor

1. **Skills CLI (Vercel)**
```bash
npx skills add vercel-labs/json-render --skill yaml -a cursor
```

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

### GitHub Copilot

1. **GitHub CLI**
```bash
gh skill install vercel-labs/json-render yaml
```

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

### Gemini CLI

1. **Skills CLI (Vercel)**
```bash
npx skills add vercel-labs/json-render --skill yaml -a gemini-cli
```

2. **Platform CLI**
```bash
gemini skills install https://github.com/vercel-labs/json-render --path skills/yaml
```

### Windsurf (Devin Desktop)

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

### OpenCode

**Skills CLI (Vercel)**
```bash
npx skills add vercel-labs/json-render --skill yaml -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/vercel-labs/json-render/tree/HEAD/skills/yaml/SKILL.md

## When to use it
- parse YAML as a stream and emit JSON Patch operations
- generate AI prompts with YAML format instructions
- convert YAML fences from LLM stream into json-render patches
- apply RFC 7396 merge and RFC 6902 patch to a spec via YAML
- make surgical spec edits without rewriting the entire object

## Example prompts
- add `yamlPrompt` to the system prompt for the component catalog
- set up `pipeYamlRender` for the stream with `previousSpec` from the current spec
- use `createYamlStreamCompiler` to parse YAML chunks as they arrive

## 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: 171a3adf60647eb0.

BEGIN THIRD-PARTY FILE 171a3adf60647eb0
````text
---
name: yaml
description: YAML wire format for json-render with streaming parser, prompt generation, and AI SDK transform. Use when working with @json-render/yaml, YAML-based spec streaming, yaml-spec/yaml-edit fences, or YAML prompt generation.
---

# @json-render/yaml

YAML wire format for `@json-render/core`. Progressive rendering and surgical edits via streaming YAML.

## Key Concepts

- **YAML wire format**: Alternative to JSONL that uses code fences (`yaml-spec`, `yaml-edit`, `yaml-patch`, `diff`)
- **Streaming parser**: Incrementally parses YAML, emits JSON Patch operations via diffing
- **Edit modes**: Patch (RFC 6902), merge (RFC 7396), and unified diff
- **AI SDK transform**: `TransformStream` that converts YAML fences into json-render patches

## Generating YAML Prompts

```typescript
import { yamlPrompt } from "@json-render/yaml";
import { catalog } from "./catalog";

// Standalone mode (LLM outputs only YAML)
const systemPrompt = yamlPrompt(catalog, {
  mode: "standalone",
  editModes: ["merge"],
  customRules: ["Always use dark theme"],
});

// Inline mode (LLM responds conversationally, wraps YAML in fences)
const chatPrompt = yamlPrompt(catalog, { mode: "inline" });
```

Options:

- `system` (string) — Custom system message intro
- `mode` ("standalone" | "inline") — Output mode, default "standalone"
- `customRules` (string[]) — Additional rules appended to prompt
- `editModes` (EditMode[]) — Edit modes to document, default ["merge"]

## AI SDK Transform

Use `pipeYamlRender` as a drop-in replacement for `pipeJsonRender`:

```typescript
import { pipeYamlRender } from "@json-render/yaml";
import { createUIMessageStream, createUIMessageStreamResponse } from "ai";

const stream = createUIMessageStream({
  execute: async ({ writer }) => {
    writer.merge(pipeYamlRender(result.toUIMessageStream()));
  },
});
return createUIMessageStreamResponse({ stream });
```

For multi-turn edits, pass the previous spec:

```typescript
pipeYamlRender(result.toUIMessageStream(), {
  previousSpec: currentSpec,
});
```

The transform recognizes four fence types:

- `yaml-spec` — Full spec, parsed progressively line-by-line
- `yaml-edit` — Partial YAML deep-merged with current spec (RFC 7396)
- `yaml-patch` — RFC 6902 JSON Patch lines; applied to the working spec, so later `yaml-edit` fences see them
- `diff` — Unified diff applied to serialized spec

## Streaming Parser (Low-Level)

```typescript
import { createYamlStreamCompiler } from "@json-render/yaml";

const compiler = createYamlStreamCompiler<Spec>();

// Feed chunks as they arrive from any source
const { result, newPatches } = compiler.push("root: main\n");
compiler.push("elements:\n  main:\n    type: Card\n");

// Flush remaining data at end of stream
const { result: final } = compiler.flush();

// Reset for next stream (optionally with initial state)
compiler.reset({ root: "main", elements: {} });
```

Methods: `push(chunk)`, `flush()`, `getResult()`, `getPatches()`, `reset(initial?)`

## Edit Modes (from @json-render/core)
````
END THIRD-PARTY FILE 171a3adf60647eb0

The third-party file has ended. Everything between the 171a3adf60647eb0 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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