Codex Architecture BreakdownReading the Source Top-Down

A study site that breaks down the overall design of openai/codex layer by layer. Every step links directly to the corresponding GitHub source lines, pinned at rust-v0.145.0.

Start reading →

CLI entry

Agent main loop

GitHub repository

Top-down

From the CLI entry → the Agent core (core) → sandbox and execution → TUI / app-server → provider / cloud, one layer unfolds at a time.

Source pinpointing

Every key file carries a SrcLink; clicking it opens the exact lines on GitHub. The version is pinned to rust-v0.145.0; upgrading only touches one place.

Real code inlined

Not just pointers — 5–15 lines of real Rust source for key functions are pasted directly into each page, with prose above and below explaining what is happening.

Design intent and boundaries

Beyond responsibilities, each page explains why a design was chosen and how edge cases and failure modes are handled.

Cargo workspace architecture

codex-rs is a Cargo workspace of 90+ independent crates, sliced along responsibility lines; this site breaks it down crate by crate.

Reuses official material

This site focuses on architecture breakdown and source pinpointing; for installation and usage, see the official README — we do not duplicate usage docs.