Agent Configs

AI Agent Configuration Comparison

This document provides a detailed breakdown and comparison of configuration paths across major AI coding agent platforms: Claude Code, OpenAI Codex, Google Antigravity, Google Antigravity CLI, OpenCode, Kilo Code, Cursor, GitHub Copilot, and Aider.

NOTE

Google Antigravity vs. Antigravity CLI: Both surfaces run on the same shared underlying agent harness and customization engine. They share identical public paths for Main Context Files (AGENTS.md), MCP Server definitions (mcp_config.json), and Agent Skills (skills/). However, the CLI maintains separate surface-level settings at ~/.gemini/antigravity-cli/settings.json.

The comparison is organized across seven core functional dimensions:

1. Main Context File (instruction manuals and rule briefs like AGENTS.md or CLAUDE.md)
2. MCP Servers (Model Context Protocol configuration files)
3. Agent Skills (reusable capabilities and workflows)
4. Execution Hooks (pre/post tool execution handlers and lifecycle scripts)
5. Custom Subagents & Modes (specialized agent definitions and mode paths)
6. File Access & Ignore Controls (workspace exclusion files like .antigravityignore or .claudeignore)
7. Plugin & Extension Bundling (packaged deployment units containing plugin.json)

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1. Main Context File

Overview

The Main Context File provides persistent instructions, rules, coding guidelines, and project architecture overviews to the AI agent. Rather than needing to repeat instructions in every prompt, agents automatically load these Markdown files at startup to ground their reasoning and tool usage.

Configuration Matrix

Platform / Agent	User-Level Config Path	Per-Project Config Path	Multi-Path / Hierarchical Search
Claude Code	~/.claude/CLAUDE.md	./CLAUDE.md ./.claude/CLAUDE.md	Yes: Traverses from working directory up to git/project root, combining with global user rules.
OpenAI Codex	~/.codex/AGENTS.md	./AGENTS.md ./.codex/AGENTS.md	Yes: Scans directory tree; nested/closer directory files take precedence over parent or global files.
Google Antigravity	~/.gemini/config/AGENTS.md	./AGENTS.md ./.agents/AGENTS.md	Yes: Performs parent traversal from current file folder to workspace root, loading all AGENTS.md files.
Google Antigravity CLI	~/.gemini/config/AGENTS.md	./AGENTS.md ./.agents/AGENTS.md	Yes: Uses identical parent directory traversal and scoped rule aggregation as Antigravity Desktop/IDE.
OpenCode	~/.config/opencode/AGENTS.md	./AGENTS.md ./.opencode/AGENTS.md	Yes: Evaluates global and project-level files in priority hierarchy (Project > Global > Remote).
Kilo Code	~/.config/kilo/AGENTS.md	./AGENTS.md ./.kilocode/AGENTS.md	Yes: Supports nested AGENTS.md files in subdirectories, overriding parent or global rules.
Cursor	~/.cursor/rules/	./AGENTS.md ./.cursorrules ./.cursor/rules/*.mdc	Yes: Evaluates workspace root rules, glob-matched .mdc rules, and global user rules.
GitHub Copilot	~/.config/github-copilot/instructions.md	./AGENTS.md ./.github/copilot-instructions.md ./.github/instructions/*.md	Yes: Combines repository instructions with subfolder-scoped .github/instructions/*.md files.
Aider	~/.aider.conf.yml	./AGENTS.md ./CONVENTIONS.md ./.aider.conventions.md	Yes: Reads global config defaults, workspace conventions files, and git repository rules.

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2. MCP Servers

Overview

The Model Context Protocol (MCP) is an open standard that allows AI agents to securely connect to external tools, databases, documentation servers, and third-party APIs. MCP configuration files define server executables, transport mechanisms (stdio, SSE, or streamable HTTP), and environment variables.

Configuration Matrix

Platform / Agent	User-Level Config Path	Per-Project Config Path	Multi-Path / Hierarchical Search
Claude Code	~/.claude.json	./.mcp.json	Yes: Merges global servers in ~/.claude.json with project-specific servers in .mcp.json.
OpenAI Codex	~/.codex/config.toml	./.codex/config.toml ./.codex/mcp.json	Yes: Aggregates global configuration entries with project-level settings.
Google Antigravity	~/.gemini/config/mcp_config.json	./.agents/mcp_config.json	Yes: Aggregates server definitions across global user configs, workspace paths, and active plugins.
Google Antigravity CLI	~/.gemini/config/mcp_config.json	./.agents/mcp_config.json	Yes: Shares the core MCP engine and discovery logic with Antigravity Desktop/IDE.
OpenCode	~/.config/opencode/opencode.json	./opencode.json ./.opencode/opencode.json	Yes: Merges global opencode.json settings with per-project configurations.
Kilo Code	~/.config/kilo/kilo.jsonc	./kilo.jsonc ./.kilo/kilo.jsonc	Yes: Merges user-level kilo.jsonc configurations with project-level config files.
Cursor	~/.cursor/mcp.json	./.cursor/mcp.json	Yes: Merges global Cursor MCP configuration with workspace .cursor/mcp.json.
GitHub Copilot	~/.config/github-copilot/mcp.json	./.github/mcp.json	Yes: Combines global Copilot tool integrations with workspace .github/mcp.json.
Aider	~/.aider.conf.yml	./.aider.conf.yml	Yes: Merges mcp-servers settings defined in global and local .aider.conf.yml files.

MCP Format Examples & Compatibility

Format 1: Standard mcpServers JSON Object

The standard format defined by the core Model Context Protocol ecosystem.

{
  "mcpServers": {
    "github": {
      "command": "npx",
      "args": ["-y", "@modelcontextprotocol/server-github"],
      "env": {
        "GITHUB_PERSONAL_ACCESS_TOKEN": "ghp_xxx"
      }
    },
    "remote-service": {
      "url": "https://mcp.example.com/sse",
      "headers": {
        "Authorization": "Bearer token123"
      }
    }
  }
}

• Compatible Platforms: Claude Code, Google Antigravity, Google Antigravity CLI, Kilo Code, and OpenCode (via fallback parser).

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Format 2: OpenCode Custom JSON Object (mcp)

Uses an "mcp" key with explicit type declarations ("local" vs "remote") and command arrays.

{
  "mcp": {
    "github": {
      "type": "local",
      "command": ["npx", "-y", "@modelcontextprotocol/server-github"],
      "environment": {
        "GITHUB_PERSONAL_ACCESS_TOKEN": "ghp_xxx"
      }
    },
    "remote-service": {
      "type": "remote",
      "url": "https://mcp.example.com/sse"
    }
  }
}

• Compatible Platforms: OpenCode (opencode.json).

---

Format 3: OpenAI Codex TOML Configuration

Defines servers using TOML table syntax ([mcp_servers.<name>]).

[mcp_servers.github]
command = "npx"
args = ["-y", "@modelcontextprotocol/server-github"]
env = { GITHUB_PERSONAL_ACCESS_TOKEN = "ghp_xxx" }
 
[mcp_servers.remote-service]
url = "https://mcp.example.com/sse"

• Compatible Platforms: OpenAI Codex (config.toml).

---

3. Agent Skills

Overview

Agent Skills are directory-based capability packages containing a SKILL.md manifest (with metadata and instructions) alongside supporting scripts, documentation references, or assets. Skills operate on a progressive disclosure model: agents load only skill names and descriptions into primary context, retrieving full instructions and scripts only when relevant to a specific user prompt.

Configuration Matrix

Platform / Agent	User-Level Config Path	Per-Project Config Path	Multi-Path / Hierarchical Search
Claude Code	~/.claude/skills/	./.claude/skills/	Yes: Discovers skills from both global (~/.claude/skills/) and project (.claude/skills/) directories.
OpenAI Codex	~/.codex/skills/	./.codex/skills/ ./skills/	Yes: Discovers installed skills from both user home directories and local repository paths.
Google Antigravity	~/.gemini/config/skills/	./.agents/skills/	Yes: Collects skills across user home directories, workspace folders (and parent traversals), and loaded plugins.
Google Antigravity CLI	~/.gemini/config/skills/	./.agents/skills/	Yes: Shares skill resolution and progressive disclosure pipeline with Antigravity Desktop/IDE.
OpenCode	~/.config/opencode/skills/	./.opencode/skills/	Yes: Automatically indexes skills from global user folders and local workspace directories.
Kilo Code	~/.kilocode/skills/	./.kilocode/skills/	Yes: Scans global and project-level skill folders, dynamically serving instructions based on intent.
Cursor	~/.cursor/skills/	./.cursor/rules/ ./.cursor/skills/	Yes: Discovers workspace rules and tool definitions in .cursor/.
GitHub Copilot	~/.config/github-copilot/skills/	./.github/skills/	Yes: Discovers repository skills and extension capabilities.
Aider	~/.aider/skills/	./.aider/skills/	Yes: Discovers python helper utilities and custom command scripts.

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4. Execution Hooks

Overview

Execution Hooks are event-driven handlers that automatically execute scripts or commands during specific stages of the agent’s interaction lifecycle (such as before running shell commands, after editing files, upon receiving user input, or prior to tool invocation).

Configuration Matrix

Platform / Agent	User-Level Config Path	Per-Project Config Path	Multi-Path / Hierarchical Search
Claude Code	~/.claude/hooks.json	./.claude/hooks.json	Yes: Merges user-level and project-level hook definitions.
OpenAI Codex	~/.codex/config.toml	./.codex/config.toml	Yes: Aggregates [hooks] definitions in global and local configuration files.
Google Antigravity	~/.gemini/config/hooks.json	./.agents/hooks.json	Yes: Discovers hook definitions across user home directories, workspace parent traversals, and active plugins.
Google Antigravity CLI	~/.gemini/config/hooks.json	./.agents/hooks.json	Yes: Shares hook resolution and event trigger pipelines with Antigravity Desktop/IDE.
OpenCode	~/.config/opencode/opencode.json	./opencode.json ./.opencode/opencode.json	Yes: Combines lifecycle event listeners configured in global and local opencode.json files.
Kilo Code	~/.config/kilo/kilo.jsonc	./kilo.jsonc ./.kilo/kilo.jsonc	Yes: Combines global and workspace-level hook configurations.
Cursor	~/.cursor/hooks.json	./.cursor/hooks.json	Yes: Merges global Cursor hooks with project-level .cursor/hooks.json.
GitHub Copilot	~/.config/github-copilot/hooks.json	./.github/hooks.json	Yes: Triggers pre/post tool hooks configured in global and workspace settings.
Aider	~/.aider.conf.yml	./.aider.conf.yml	Yes: Executes configured lint-cmd and test-cmd hooks post-edit.

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5. Custom Subagents & Modes

Overview

Custom Subagents and Modes allow developers to define specialized secondary assistants with targeted prompt instructions, scoped tool allowances, and restricted file execution permissions (such as dedicated code-reviewer, security auditor, architect, or planning agents).

Configuration Matrix

Platform / Agent	User-Level Config Path	Per-Project Config Path	Multi-Path / Hierarchical Search
Claude Code	~/.claude/skills/	./.claude/skills/	Yes: Invokes specialized skill routines on demand via /skill-name or prompt matching.
OpenAI Codex	~/.codex/agents/	./.codex/agents/	Yes: Discovers custom subagent definitions across global and project paths.
Google Antigravity	~/.gemini/config/agents/	./.agents/agents/	Yes: Aggregates subagent definitions across user home directories, workspace parent traversals, and loaded plugins.
Google Antigravity CLI	~/.gemini/config/agents/	./.agents/agents/	Yes: Shares subagent discovery and invocation engines with Antigravity Desktop/IDE.
OpenCode	~/.config/opencode/agents/	./.opencode/agents/	Yes: Indexes custom primary and subagent Markdown definitions across global and project paths.
Kilo Code	~/.config/kilo/modes/	./.kilocode/modes/	Yes: Configures custom mode routines (e.g., Code, Architect, Ask) in global or project paths.
Cursor	~/.cursor/agents/	./.cursor/agents/	Yes: Supports custom agent prompts and subagent routines in .cursor/.
GitHub Copilot	~/.config/github-copilot/agents/	./.github/agents/	Yes: Supports custom agent participants and Copilot extensions.
Aider	N/A	./.aider.conf.yml	Yes: Toggles dual-agent pairing modes (Architect vs. Editor) via .aider.conf.yml.

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6. File Access & Ignore Controls

Overview

File Access and Ignore Controls define workspace exclusion rules and sandboxing guardrails using glob patterns (similar to .gitignore) to prevent AI agents from accessing, indexing, or modifying sensitive files, credentials, dependency directories, or build outputs.

Configuration Matrix

Platform / Agent	User-Level Config Path	Per-Project Config Path	Multi-Path / Hierarchical Search
Claude Code	~/.claude/settings.json	./.claudeignore	Yes: Checks .claudeignore at workspace root and respects .gitignore rules.
OpenAI Codex	~/.codex/config.toml	./.codexignore	Yes: Evaluates [security.ignore] settings in config.toml alongside workspace .codexignore rules.
Google Antigravity	N/A	./.antigravityignore	Yes: Enforces workspace .antigravityignore patterns and automatically respects standard .gitignore rules.
Google Antigravity CLI	N/A	./.antigravityignore	Yes: Shares file sandboxing and exclusion guardrails with Antigravity Desktop/IDE.
OpenCode	~/.config/opencode/opencode.json	./.opencodeignore	Yes: Merges global ignore configurations in opencode.json with workspace .opencodeignore rules.
Kilo Code	~/.config/kilo/kilo.jsonc	./.kilocodeignore	Yes: Enforces path-level permission rules defined in .kilocodeignore and kilo.jsonc.
Cursor	N/A	./.cursorignore	Yes: Filters files using .cursorignore patterns and respects workspace .gitignore.
GitHub Copilot	N/A	./.copilotignore	Yes: Excludes patterns in .copilotignore and respects workspace .gitignore.
Aider	N/A	./.aiderignore	Yes: Filters files using .aiderignore patterns and respects standard .gitignore.

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7. Plugin & Extension Bundling

Overview

Plugin and Extension Bundling allows teams to package and distribute rules, MCP servers, hooks, skills, and subagents into single, version-controlled deployment units that can be shared across teams or installed via marketplaces.

Configuration Matrix

Platform / Agent	User-Level Config Path	Per-Project Config Path	Multi-Path / Hierarchical Search
Claude Code	~/.claude/plugins/	./.claude/plugins/	Yes: Scans user-installed plugin packages and workspace plugin folders.
OpenAI Codex	~/.codex/plugins/	./.codex/plugins/	Yes: Indexes user-level installed extensions and repository plugin manifests.
Google Antigravity	~/.gemini/antigravity-cli/plugins/	./.agents/plugins/	Yes: Discovers namespaced plugin bundles containing plugin.json, mcp_config.json, hooks.json, skills/, agents/, and rules/.
Google Antigravity CLI	~/.gemini/antigravity-cli/plugins/	./.agents/plugins/	Yes: Shares plugin discovery and module loading pipelines with Antigravity Desktop/IDE.
OpenCode	~/.config/opencode/plugins/	./.opencode/plugins/	Yes: Loads installed global plugins and project-level plugin folders.
Kilo Code	~/.kilocode/plugins/	./.kilocode/plugins/	Yes: Loads extensions installed from the Kilo Marketplace or specified in project settings.
Cursor	~/.cursor/extensions/	./.cursor/plugins/	Yes: Discovers installed extensions and workspace plugin bundles.
GitHub Copilot	Copilot Extensions Marketplace	./.github/plugins/	Yes: Integrates GitHub Copilot App extensions and repository plugins.
Aider	~/.aider/plugins/	./.aider/plugins/	Yes: Discovers installed python extensions and custom scripts.