Codex vs Claude Code for large monorepos
We tested both on a 200k+ LOC codebase. Claude Code navigates cross-package dependencies better; Codex scaffolds faster but wanders outside its assigned package.
Workflows, instruction files, comparisons and open questions. Each carries a status — open question, being tested, or established — and an answered question becomes the method page rather than spawning a new one.
18 methods
We tested both on a 200k+ LOC codebase. Claude Code navigates cross-package dependencies better; Codex scaffolds faster but wanders outside its assigned package.
Codex is fast and overshoots; Claude is a pedantic reviewer. Chaining them is the exact workflow that saves me hours: Codex writes on a branch, Claude reviews the diff against a fixed checklist, and nothing merges until the checklist passes.
Same 12 tasks I run on every release. Fable took 9, Opus took 2, one tie — but the interesting part isn't the score.
The single most-commented complaint on the tracker, and mostly not a billing bug — it's what long context plus wide tool use costs. Here's what actually moved the needle for people.
Fifteen lines, ~180 tokens, and it outperforms the 400-line files it replaced. Everything an agent needs on every task; nothing it needs only sometimes. The controversial part is what's missing.
A long-running report with a lot of theories and few confirmed fixes. Collecting what has and hasn't worked, honestly labelled.
Run three or four agents against the same repo without them stomping each other's changes. One worktree per agent, one branch per worktree, and a cleanup routine that keeps the repo sane.
Not benchmarks, not demos — daily driving. Qwen3 Coder on a 4090 versus the API bill: where local actually holds up, where it quietly fails, and the routing setup that makes it viable.
Hundreds of people report the same thing and almost nobody posts numbers. Here are ours, and what we found when we went looking for the cause.
Mine grew to 600 lines and the agent ignores most of it. Time to talk about what earns a slot in the most expensive real estate in your repo.
The most-requested Claude Code feature by comment count. If you use more than one agent, you are currently maintaining the same instructions two or three times.
Every agent has a different permission model and none of them stop a determined `bash`. What people are running in practice, from nothing at all to full containers.
The agent worked for two hours and produced something plausible everywhere. Rubber-stamping is negligence, line-by-line is a full day. What's the actual workflow?
Agents read everything they can reach, including the .env you forgot about. Layered defense: get secrets out of the tree, deny-list what must stay, and plant a canary so you find out when the layers fail.
Claude Code can't see Xcode's build errors unless you hand them over. XcodeBuild MCP plus a formatter that strips the noise gives the agent a real edit-build-test loop for SwiftUI work — the difference between guessing and iterating.
The AGENTS.md running my shipping iOS app. Simulator names, the exact xcodebuild invocations, SwiftUI conventions the agent kept violating until they were written down, and a definition of done that includes a green test run.
Five days, two agents, one working Stripe billing portal: what was delegated, what broke, what it cost ($61.40 all-in), and the day everything went sideways.
Eight days migrating a legacy widget suite to WidgetKit with Claude Code and XcodeBuild MCP: timeline budgets, a haunted pbxproj, and $84 of tokens.