Vellum AI Coding Assistant

A powerful command-line AI coding agent with a rich Terminal User Interface, Vim modal editing, extensible slash command system, and project-aware configuration via AGENTS.md files.

What This Skill Does

This skill helps you work with the Vellum CLI, a next-generation AI coding assistant that provides:

Instructions

When the user requests help with Vellum CLI:

1. **Identify the Task Category**

- Installation and setup

- Interactive mode usage

- TUI customization

- Slash commands

- AGENTS.md configuration management

- Language/theme preferences

- Custom command development

2. **Installation Tasks**

```bash

# Global installation

npm install -g @butlerw/vellum

```

3. **Basic Usage**

```bash

# Start interactive mode

vellum

# Run with specific prompt

vellum "Create a React component"

# Run with configuration file

vellum --config vellum.config.json

# Start with specific language

vellum --language zh

```

4. **AGENTS.md Management**

**Initialize new AGENTS.md:**

```bash

# Interactive wizard

vellum init

# Minimal template (skip wizard)

vellum init --minimal

# Overwrite existing

vellum init --force

# Non-interactive (CI mode)

vellum init --non-interactive

```

**Show current configuration:**

```bash

# Display merged config

vellum agents show

# JSON output

vellum agents show --json

# Verbose with sources

vellum agents show --verbose

# Scope-specific config

vellum agents show --scope ./src

```

**Validate AGENTS.md files:**

```bash

# Validate all files

vellum agents validate

# Validate specific file

vellum agents validate ./AGENTS.md

# JSON output for CI

vellum agents validate --json

```

**Generate AGENTS.md from project:**

```bash

# Auto-detect and generate

vellum agents generate

# Preview without writing

vellum agents generate --dry-run

# Custom output path

vellum agents generate --output ./config/AGENTS.md

# Merge with existing

vellum agents generate --merge

```

5. **Slash Commands**

Available commands in interactive mode:

| Command | Usage | Description |

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

| `/help [topic]` | `/help`, `/h`, `/?` | Show help |

| `/clear` | `/clear`, `/cls` | Clear screen |

| `/exit [--force]` | `/exit`, `/q` | Exit application |

| `/login [provider]` | `/login anthropic` | Add credentials |

| `/logout [provider]` | `/logout anthropic` | Remove credentials |

| `/credentials` | `/credentials` | Show credential status |

| `/language [code]` | `/language zh` | Change language |

Command syntax examples:

```bash

# Basic command

/help

# With positional argument

/login anthropic

# With flags

/exit --force

/exit -f

# With flag and value

/login anthropic --store keychain

# Mixed arguments

/config theme --value dark --global

```

6. **Language Configuration**

```bash

# Show current language

/language

# Switch to Chinese

/language zh

# Switch to English

/language en

# Auto-detect

/language auto

# Or use environment variable

export VELLUM_LANGUAGE=zh

```

Language priority (highest first):

1. `--language` CLI flag

2. `VELLUM_LANGUAGE` env var

3. Saved preference

4. System locale

5. Default (en)

7. **TUI Customization**

When user needs to customize the interface:

```typescript

import { RootProvider, Layout, TextInput, MessageList, StatusBar } from "@vellum/cli";

function App() {

return (

<RootProvider theme="dracula">

<Layout

header={<StatusBar model={{ provider: "anthropic", model: "claude-3" }} />}

footer={<TextInput value={input} onChange={setInput} />}

>

<MessageList messages={messages} />

</Layout>

</RootProvider>

);

}

```

Available themes: `dark`, `light`, `dracula`, `nord`, `solarized`

8. **Custom Command Development**

When user wants to extend functionality:

```typescript

import { CommandRegistry, type SlashCommand } from "@vellum/cli";

const myCommand: SlashCommand = {

name: "greet",

description: "Send a greeting",

kind: "user",

category: "tools",

positionalArgs: [

{

name: "name",

type: "string",

description: "Name to greet",

required: false,

},

],

namedArgs: [

{

name: "loud",

shorthand: "l",

type: "boolean",

description: "Use uppercase",

required: false,

default: false,

},

],

execute: async (ctx) => {

const name = ctx.parsedArgs.positional[0] ?? "World";

const loud = ctx.parsedArgs.named.loud;

const message = `Hello, ${name}!`;

return {

kind: "success",

message: loud ? message.toUpperCase() : message,

};

},

};

registry.register(myCommand);

```

9. **Key Features to Highlight**

- **Autocomplete**: Type `/` to trigger fuzzy-matching command autocomplete

- **Vim Mode**: Enable with `vimMode: true` in config

- **Copy Mode**: Visual text selection and copy in TUI

- **Project Detection**: Auto-detects frameworks, languages, build tools

- **Validation**: Syntax checking for AGENTS.md files

- **Merge Support**: Hierarchical AGENTS.md configuration

10. **Development Commands**

```bash

# Development mode

pnpm dev

# Build

pnpm build

# Test

pnpm test

# Benchmarks

pnpm exec vitest bench

# Type check

pnpm typecheck

```

Important Notes

Example Workflows

**Setting up a new project:**

```bash

Install globally

npm install -g @butlerw/vellum

Initialize project configuration

vellum init

Validate configuration

vellum agents validate

Start interactive mode

vellum

```

**Working with existing project:**

```bash

Show current config

vellum agents show --verbose

Generate updated config from project

vellum agents generate --merge

Start with Chinese UI

vellum --language zh

```

**Custom integration:**

```bash

Show config as JSON for tooling

vellum agents show --json

Validate in CI pipeline

vellum agents validate --json