# How Edward Z. Yang actually uses coding agents

PyTorch at Meta, ghstack

**If you take one thing:** `sl follow / sl adopt`, restack parallel agents. two Sapling aliases let agents in several worktrees amend one shared stack without trampling each other.

- **Agent:** Claude Code (cli) ([source, 2026-10-06](https://github.com/ezyang/piano-pad/blob/fc9c0ab3dc8b5a24528e4e57ace5eb62f2d28472/CLAUDE.md#L10-L11))
- **Agent:** Codex ([source, 2026-05-30](https://github.com/ezyang/mergedog/blob/a1ed015cab57b3a7c38d6dd2fea37ec00ed2a1c3/CLAUDE.md#L19))
- **Model:** Claude Opus 5.5 ([source, 2026-10-06](https://github.com/ezyang/piano-pad/commit/fc9c0ab3dc8b5a24528e4e57ace5eb62f2d28472))
- **Model:** Claude Fable 5 ([source, 2026-08-12](https://github.com/ezyang/fable-nanny/blob/48da0da97c7eefc33c6fcf95c2d23c078819f8e9/run-fable.sh#L21))
- **Review:** Reads every line, steers with questions and edits ([source, 2026-03-10](https://blog.ezyang.com/2026/03/ai-assisted-programming-for-spmd-types/))
- **At once:** 3 work streams ([source, 2026-03-13](https://blog.ezyang.com/2026/03/parallel-agents-heart-sapling/))
- **Harness:** iTerm2 + tmux -CC to a remote GPU box, three worktrees, Sapling ([source, 2026-03-10](https://blog.ezyang.com/2026/03/ai-assisted-programming-for-spmd-types/))
- **Rules file:** Per-repo CLAUDE.md / AGENTS.md; piano-pad's assigns roles to three agents ([source, 2026-10-06](https://github.com/ezyang/piano-pad/blob/fc9c0ab3dc8b5a24528e4e57ace5eb62f2d28472/CLAUDE.md#L19))
- **Skills:** pt2-triage, pt2-triage-rubric ([source, 2026-01-20](https://github.com/ezyang/pt2-triage/tree/3e1f179198dfd553a922ce371869e2f3ae032e3d/.claude/skills))
- **Hooks:** UserPromptSubmit: small-chunks reminder, StopFailure: self re-prompt via tmux ([source, 2026-08-12](https://github.com/ezyang/fable-nanny/blob/48da0da97c7eefc33c6fcf95c2d23c078819f8e9/run-fable.sh#L16-L17))

## In their words

> The project is run by three long-lived Claude sessions. The human (the parent)
gives high-level direction, usually by texting one agent over Remote Control.

> Codex shell commands may not have working external internet access, even when the local machine does.

> Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

> export ANTHROPIC_MODEL=us.anthropic.claude-fable-5

> The basic development flow here is I have three work streams going in parallel:


Archetype (our label): Purist. Newest source: 2026-10-06.
Card: https://www.prehistoriq.com/stacks/ezyang/ · Data: https://github.com/prehistoriq/stacks/blob/main/data/stacks/ezyang.json