Your coding agent

A coding agent is steered by files: an instruction file at the root of the project, rules that apply to some paths, skills it can invoke, sub-agents it can delegate to, commands you can call. They are markdown, they live in the repository, and they are the most consequential prose most developers write now. Marginal is built to edit them.

Every agent keeps those files in different places, under different names. Marginal knows the layout of six of them. Tell it which one you use, and the file list shows exactly the files that agent will read, from the workspace and from your home folder, each opened with a click.

Choosing the agent

Open Settings ▸ AI ▸ Coding agent and pick one:

Agent	Made by	Instruction file	Page
Claude Code	Anthropic	CLAUDE.md	Claude Code
Codex	OpenAI	AGENTS.md	Codex
Grok Build	xAI	AGENTS.md	Grok Build
OpenCode	open source	AGENTS.md	OpenCode
Cursor	Anysphere	AGENTS.md and .cursor/rules	Cursor
Qwen Code	Alibaba	QWEN.md	Qwen Code

Claude Code is the default. The choice is saved in your settings and applies to every workspace. Unfold Where … looks for its files under the setting to see every folder the selected agent reads without leaving the app; it also links to the agent’s page here.

Changing the agent rescans the open workspace at once. You do not need to reopen the folder.

What appears in the file list

Below MARKDOWN, a caption names the agent and up to five sections follow:

• the instruction file section, titled with the agent’s own name for it: CLAUDE.md, AGENTS.md, or QWEN.md;
• RULES, for agents that have a rules folder;
• SKILLS, one entry per SKILL.md;
• AGENTS, the sub-agent definitions;
• COMMANDS, custom commands or prompts, shown as /name.

A section is only there when it has entries. Each entry shows the name from the file’s front matter when it has one, its description as a second line, and a badge:

Badge	Meaning
project	In the workspace, shared with everyone who clones it
local	In the workspace but yours alone: CLAUDE.local.md, .qwen/QWEN.local.md
user	In your home folder, applied to every project

Project entries come first, then local, then user. The sections start collapsed; Settings ▸ AI ▸ Unfold agent sections opens them by default, and the file filter opens them while you type.

Switching the agent changes what is listed, not what is on disk. A folder that carries both a CLAUDE.md and an AGENTS.md shows one or the other, depending on which agent you picked.

Where the files come from

Each agent page lists the exact folders, but the pattern is the same for all of them:

• In the workspace. The instruction file at the root and in any subfolder (agents load nested ones when they work in that folder), and the agent’s own dot-folder at the root: .claude, .codex, .grok, .opencode, .cursor, or .qwen. Some agents also read the shared .agents/skills convention, and some read another agent’s folders for compatibility; those are listed under the agent that reads them.
• In your home folder. The same layout under ~/.claude, ~/.codex, and so on, for files that apply to every project. If the agent has an environment variable that moves that folder, such as CLAUDE_CONFIG_DIR or CODEX_HOME, Marginal honours it when it is set in the environment Marginal was started from. An app launched from the Dock or the Start menu sees a different environment from a terminal.
• Nested folders. Where an agent looks for its dot-folder in every directory, not just the root, Marginal does too, and the entry’s name carries the folder: packages/api/style.mdc.

Marginal never writes to these folders on its own. It lists what is there and opens it in a tab; saving is the same as for any other file.

Files that are not markdown

Cursor rules are .mdc, Codex sub-agents and execution rules are .toml and .rules, and Qwen Code still reads its older .toml commands. Marginal lists them because the agent reads them, and opens them in the editor as plain text. The preview treats them as markdown, which is right for .mdc and of little use for the others.

What is not listed

Settings files, hooks, MCP server configuration, plugins, memories written by the agent, and managed or enterprise paths under /etc or /Library/Application Support are not context files and stay out of the list. Each agent page ends with a short list of what it leaves out.

The folders Marginal scans were checked against each agent’s official documentation on 1 September 2026. Agents move fast, so each page says what was documented, what is still read but deprecated, and what is no longer read at all.