OpenCode reads ~/.claude/CLAUDE.md (undocumented Claude Code compatibility)

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# OpenCode reads ~/.claude/CLAUDE.md (undocumented)

If you use both [OpenCode](https://opencode.ai) and [Claude Code](https://docs.anthropic.com/en/docs/claude-code), you may notice that OpenCode automatically picks up your `~/.claude/CLAUDE.md` file.

This is **intentional but undocumented** behavior for Claude Code compatibility.

## How it works

OpenCode loads instruction files from multiple locations:

1. **Project-level** (documented): `AGENTS.md`, `CLAUDE.md`, or `CONTEXT.md` in your project directory
2. **Global** (documented): `~/.config/opencode/AGENTS.md`
3. **Claude Code compat** (undocumented): `~/.claude/CLAUDE.md`

The relevant code is in [`packages/opencode/src/session/system.ts`](https://github.com/anomalyco/opencode/blob/c87939ad122a79150fa6360dacfdef63ea396b2d/packages/opencode/src/session/system.ts#L70-L73):

```typescript
const GLOBAL_RULE_FILES = [path.join(Global.Path.config, "AGENTS.md")]
if (!Flag.OPENCODE_DISABLE_CLAUDE_CODE_PROMPT) {
  GLOBAL_RULE_FILES.push(path.join(os.homedir(), ".claude", "CLAUDE.md"))
}
```

## Disabling this behavior

If you don't want OpenCode to read your `~/.claude/CLAUDE.md` file, set the environment variable:

```bash
export OPENCODE_DISABLE_CLAUDE_CODE_PROMPT=1
```

## What's documented vs undocumented

The [official Rules documentation](https://opencode.ai/docs/rules/) only mentions:
- Project-level `AGENTS.md` files
- Global `~/.config/opencode/AGENTS.md`

It does **not** mention the `~/.claude/CLAUDE.md` compatibility feature.

## Why this matters

If you have different instructions for Claude Code vs OpenCode, you may get unexpected behavior. Your Claude Code instructions will be applied to OpenCode sessions automatically.

## Skills too

OpenCode also scans `~/.claude/skills/` for [agent skills](https://opencode.ai/docs/skills/), as shown in [`packages/opencode/src/skill/skill.ts`](https://github.com/anomalyco/opencode/blob/c87939ad122a79150fa6360dacfdef63ea396b2d/packages/opencode/src/skill/skill.ts#L78-L79):

```typescript
// Also include global ~/.claude/skills/
const globalClaude = `${Global.Path.home}/.claude`
```