Build a Definition of Done for Claude Code & Codex

I'm Greg. I ship with agents daily.

The next forty minutes

One promise: by part four you have something you can run tonight.

A coding agent is a conversation with hands

> add a /healthz endpoint

⚙ tool call: Read src/app.ts
⚙ tool call: Edit src/app.ts
⚙ tool call: Bash npm test
   → 14 passing

Done! Added /healthz and the
tests pass. ← just words. no tool call.

Hold on to that last line: words, no tool call. It's about to matter a lot.

The model can't touch your computer. The harness can.

The model is a text function: it can ask to run a test; it can't run one. The harness is the program wrapped around it: it executes the tool calls, feeds results back… and decides when to loop and when to stop.

Claude Code · Codex CLI · Gemini CLI · Copilot CLI: different badges, same job. "Agent" = model + harness.

The loop you're already running

Claude Code, Codex, Gemini CLI, Copilot: different products, same while-loop. Reason, act, observe, repeat…

…and the run ends the moment the model replies without calling a tool. Nothing checks anything at that boundary by default.

"Done" is a feeling

Definition of Done: the origin

Why it worked, and why it transfers

Increment ↔ the diff  ·  developer says "done" ↔ model says "done"  ·  DoD ↔ executable checks  ·  Sprint Review gate ↔ the loop's exit condition

2026: the loop gets a target

Real progress: the loop finally has a destination, and the harness won't let the model wander off. But look who decides you've arrived…

Who's grading the homework?

A judge answers "does this look done?" A check answers "is this done?"

Two files. That's the lesson.

#!/usr/bin/env bash
set -e
npm test                # tests pass
test -f dist/app.js     # artifact exists
grep -q '"/healthz"' \
  src/app.ts            # it's really there

#!/usr/bin/env bash
until ./check.sh; do
  claude -p "Goal in TODO.md. Run ./check.sh,
    read the first failure, fix it, commit." \
    --allowedTools "Bash,Read,Edit" \
    --permission-mode acceptEdits
done
echo "DONE: check.sh exited 0"

until is the whole orchestration layer. The exit code is the Definition of Done. The model's opinion never touches the exit condition. Exit 0 = an Increment is born.

Using Codex instead of Claude? One change: the claude -p … line becomes codex exec --full-auto "…" with the same prompt.

$ ./loop.sh
── turn 1 ─────────────────────────────
$ ./check.sh
✗ npm test              2 failing
exit 1 → claude -p "…fix the first failure…"
  ⚙ read failures · edited src/date.ts · commit 9f3a21c
── turn 2 ─────────────────────────────
$ ./check.sh
✓ npm test
✗ test -f dist/app.js   missing
exit 1 → claude -p …
  ⚙ ran npm run build · commit 4c81d02
── turn 3 ─────────────────────────────
$ ./check.sh
✓ npm test
✓ test -f dist/app.js
✓ grep -q '"/healthz"' src/app.ts
exit 0

Done · exit 0 · stamped by the check, not the model

I didn't decide it was done. The model didn't decide. The exit code decided.

The loop, one step further

#!/usr/bin/env bash
chmod 444 check.sh          # ③ lock the gate
for attempt in 1 2 3 4 5; do  # ② budget
  out=$(./check.sh 2>&1) &&
    { echo "DONE on try $attempt"; exit 0; }
  # ① feed the failure back in:
  claude -p "Goal in TODO.md. check.sh failed:
$out
Fix the code, never the check. Commit." \
    --allowedTools "Bash,Read,Edit" \
    --permission-mode acceptEdits
done
echo "NOT DONE after 5 tries"; exit 1

Feedback → deadreckon's per-turn gate report · the budget → its spend caps & resumable turns · the lock → dr-gate. You just reinvented the next slide.

Same idea, industrial grade

curl -fsSL https://deadreckon.sh/install.sh | sh  ·  open source · MIT · supervises the CLI you already use (Claude Code, Codex, Gemini, Copilot…)

Say "done" in English. Get a gate.

$ deadreckon def-done "tests pass, dist/app.js exists, /healthz is served"
compiling plain English → .deadreckon/acceptance.yaml
checks:
  - kind: build_success     # npm test, green
  - kind: file_exists       # {working_dir}/dist/app.js
  - kind: content_match     # "/healthz" in src/app.ts
$ deadreckon start "Goal in TODO.md"
dr-gate re-runs these checks itself and signs the pass.
the agent can't reach either one.
✓ gate passed · run promoted

The same three check species you just wrote by hand in check.sh. Here the English is the source, and the gate lives outside the agent's reach.

When to skip the ceremony

If you're watching, you are the definition of done. If you're walking away, write one a machine can check.

Five things we talked about

Tonight, in three steps

Two more lessons this month

Mon · Jul 20

Build an environment-aware AI Agent from Scratch

An agent harness isn't a black box. It's a loop you can build yourself in an afternoon. With John Berryman (GitHub Copilot; author, Prompt Engineering for LLMs).

Mon · Jul 27

Make Your Repo Agent-Ready: Rules, Docs, Reviews

Most agent failures aren't the model's fault. They're the repo's. With Dan Gerlanc (co-founder, .txt / Outlines).

And for your chart table · the field guide

• 25 Patterns in Agentic Engineering · free PDF
• The moves that ship software when the agent writes the code and the human owns the proof
• Drawn from 1,310 captured agent sessions & 4,670 commits
• specstory.com/books/25-patterns-in-agentic-engineering-book-2026.pdf

Watching the recording? Everything lives at maven.com/specstory: lessons, recordings, and the course.

Questions: put them in the chat

👍 the ones you want answered. Specific beats general. Bring your actual task.

Sources: deadreckon.sh · "Goal Engineering" & "The Green Checkmark is Not a Fact" (gregceccarelli.com) · Scrum Guide 2020 · Claude Code & Codex CLI docs