Day 20 of 21

Build your pre-session safety checklist

Goal: Create the complete pre-session safety checklist you will use before every Codex session for the rest of your building career. By the end of today, the checklist is saved, tested, and added to AGENTS.md.

What to do

Understand why a checklist works — and why it has to be a literal list

A mental checklist is not a checklist — it is a hope. A checklist you can see and tick works because it forces you to stop before each item, not to rush. The goal is a checklist you can copy, paste into your notes, and tick off in under two minutes at the start of any session. If it takes more than two minutes, it is too long and you will skip it.

Copy the full pre-session checklist and personalise it

The checklist below is the complete version. Copy it into your codex-workflow.txt file or a new text file. Then personalise each item marked with [YOUR...] by filling in your project-specific detail. The items without brackets are universal — do not remove them.

PRE-SESSION SAFETY CHECKLIST
Run this before every Codex session. Takes 3-5 minutes the first few times, under 2 minutes once you know it.

[ ] 1. BRANCH CHECK
    Open GitHub Desktop.
    Current branch shown at top: ________________
    Is this the right branch, (NOT main unless intended)
    If wrong: create or switch to working branch BEFORE opening Codex.

[ ] 2. TASK WRITTEN DOWN
    My task for this session (one sentence):
    ________________________________________
    If I cannot write it in one sentence, the task is too vague. Split it first.

[ ] 3. TASK SIZE CHECK
    Will this task touch more than 3 files, yes / no
    If yes: split into phases and approve only Phase 1 today.
    [YOUR RULE: add a note about what "too big" looks like for your project]

[ ] 4. PROMPT READY
    Does my Codex prompt include:
    - A plan-first instruction, yes / no
    - A specific file restriction, yes / no
    - A stop-after instruction, yes / no
    If any "no": fix the prompt before pasting it into Codex.

[ ] 5. AGENTS.MD CURRENT GOAL UPDATED
    Does AGENTS.md say the right current goal?
    Current goal in AGENTS.md: ________________
    Does it match today's task, yes / no
    If no: update it now before opening Codex.

[ ] 6. ROLLBACK PLAN
    If this session goes wrong, I will:
    [ ] Discard uncommitted changes in GitHub Desktop
    [ ] Revert last commit using History > right-click > Revert
    [YOUR RULE: add any project-specific rollback step]

[ ] 7. POST-SESSION PLAN
    After the session, before committing, I will:
    [ ] Paste the closing prompt and read the report
    [ ] Review the diff in GitHub Desktop
    [ ] Preview in browser
    [ ] Commit only if all three look correct

Run the checklist right now as a practice run

Do not wait until Day 21 to use the checklist for the first time. Run through it right now as a practice session. Open GitHub Desktop, confirm your branch, write a one-sentence task for today, check your prompt, confirm AGENTS.md is current, and confirm your rollback plan. Tick each item as you complete it. The goal is to find anything that takes too long or does not make sense for your project — so you can fix it before the final build day.

Add the checklist to AGENTS.md so Codex sees it

Add a short reference to the checklist at the bottom of your AGENTS.md. You do not need to paste the full checklist in there — just a note that tells Codex a checklist exists and what it does. This means Codex will know about your pre-session process when it reads AGENTS.md.

Add this section to the bottom of your AGENTS.md:

## Pre-session safety checklist
Before every session, I run a 7-item pre-session safety checklist stored in codex-workflow.txt.
Key rules from that checklist that apply to you:
- I will always be on a working branch, never main, before starting
- You must write a plan before touching any file
- The task for this session is written in my AGENTS.md Current Goal line
- After finishing, wait for me to paste the closing prompt before we end the session

Commit the checklist and prepare for Day 21

Commit codex-workflow.txt and the updated AGENTS.md to your current branch. Write a clear commit message. Then open a notepad and write your one-sentence task for Day 21 — the final build day. You will use the checklist before Day 21 for real. The better prepared you are tonight, the smoother tomorrow's session will be.

Expected result

You have a complete seven-item pre-session safety checklist saved in codex-workflow.txt, committed to your branch. AGENTS.md references the checklist. You ran through it once as a practice. Your Day 21 one-sentence task is written down.

Key takeaway

A checklist is only useful if you actually run it. Write it, save it where you can find it instantly, and run it as the very first thing before every Codex session. The two minutes it takes is not overhead — it is the difference between a session you can explain and one you cannot.

Day 19 Day 21