Codex CLI vs Claude Code: How to Split Terminal Agent Roles
When Codex CLI and Claude Code share a repo, the useful question is role split—not price. Codex leans on AGENTS.md plus ~/.codex/config.toml approval/sandbox controls; Claude Code leans on CLAUDE.md, permissions, hooks, and subagents / agent view.
This article uses official Codex and Claude Code docs to cover strengths, same-repo collisions, and the IDE triangle. No pricing.
What is each tool strong at?
One-line answer: Codex fits AGENTS.md-driven terminal TUI work with sandbox knobs; Claude Code fits permission rules, hooks, and multi-agent orchestration.
| Axis | Codex CLI | Claude Code |
|---|---|---|
| Instructions | AGENTS.md (+ overrides/nesting) | CLAUDE.md (+ settings) |
| Config | ~/.codex/config.toml | ~/.claude/settings.json, .claude/settings.json |
| Safety | approval_policy + sandbox_mode | permissions allow/ask/deny + sandbox |
| Parallelism | Human-split sessions/worktrees | Subagents, agent view, (experimental) agent teams |
| Extensions | MCP / app-server integrations | Hooks, skills/commands, MCP |
Practical split (not a personal ranking):
- Lean Codex for: single tasks that follow AGENTS.md test/lint commands under a tight sandbox.
- Lean Claude Code for: long sessions with checked-in allow/deny, PreToolUse guards, explore/implement via subagents.
- Either for: one-file bugfixes once that tool’s instruction file is already warm.
Prefer the tool whose instruction file and permission model match the job; avoid “always smarter” claims as UIs and models change.
How do you avoid same-repo collisions?
One-line answer: Never dual-write one dirty tree—split by branch/worktree/issue, and keep shared commands in one AGENTS.md.
Collision points:
- Same files, two TUIs — merge pain on one dirty working tree.
- Divergent instruction files — different test commands → different “green”.
- Mismatched fences — only one side blocks network/
.env→ divergent outcomes.
Prevention:
- One branch or
git worktreeper active agent task. - Root
AGENTS.mdfor Setup commands;CLAUDE.mdpoints there and keeps Claude-only permissions. - Shared ignores for lockfiles/build artifacts.
- One human (or IDE) merge at a time.
Codex documents /import for Claude/Cursor artifacts; it does not serialize concurrent writers.
How does the IDE agent form a triangle?
One-line answer: IDE agents own edit/diff/hooks; terminal agents own long shell/repo-wide runs; hub docs live in AGENTS.md.
| Vertex | Best fit |
|---|---|
| IDE agent | File edits, inline diffs, save/commit hooks, MCP UI |
| Claude Code CLI | Long terminal sessions with permissions/hooks/subagents |
| Codex CLI | AGENTS.md + sandbox-centered TUI sessions |
Operating draft:
- Hub doc:
AGENTS.md(commands + security). - IDE: rules/hooks only for format/dangerous shell—no duplicated repo essays.
- One terminal agent per issue: Codex or Claude Code, not both.
- Handoff: IDE locks the spec → terminal implements → IDE reviews the diff.
Leave plan limits to team policy; this article’s criterion is collision-free roles.
Wrap-up
Split roles with ① strengths (AGENTS+sandbox vs permissions+hooks) → ② worktrees against collisions → ③ IDE–terminal–docs triangle. See Codex CLI, AGENTS.md guide, Claude Code permissions, and Claude Code agents.