AI Build Journal · February 7, 2026 - written by Codex to me...OpenAI released codex app for mac this week, so I decided to have a go, and boy - am I blown away!!! In just one day, Codex helped me clear much of my SMT backlog, after a month's break from my AI-coding frenzy from Dec'25.
A Day Building on Codex App with Codex 5.3
This was not “prompt in, code out.” This was a full-day product session: strategy debates, UX corrections, contract audits, feature pivots, test hardening, documentation, and ship.
I started the day with one objective: execute the next phase plan for SMT Platform without losing quality. By the end of the day, we had shipped one of the most ambitious increments in the project so far: Goal Inspections + Community Blueprints Exchange, including end-to-end contribution flow, install lifecycle logic, catalog operations, and test coverage.
What We Shipped in One Day
- Goal lifecycle + inspections system: owner status, weekly comments, PTG tracking, stale/mismatch detection, leadership report table.
- Year Plan CSV/XLSX export: production export flow in toolbar with tested serialization and schema-aware payload handling.
- Community Blueprints Exchange: Top-100 curated catalog, preview modal, search/filter, publish flow, package validation, and install lifecycle UX.
- Launch package generation upgrade: moved to
domain-authored-curated-v2for the launch-25 package set. - Hardening + compliance: contract remediation pass, UX consistency fixes, event rebinding bug fix, and regression-proof e2e updates.
The Metrics That Matter
| Metric | Result |
|---|---|
| Session duration | 11h 56m 43s (10:08:30 → 22:05:13) |
| Timestamped worklog checkpoints | 117 |
| Commits shipped | 4 (2671b68, a502106, c9d8d43, 97bec52) |
| Code delta (same-day commits) | +129,166 / -7,770 (net +121,396) |
| Unique files touched | 77 (113 file-change events across commits) |
| New files created | 27 |
| Unit test progression | 90 → 117 tests (+30%) |
| E2E test progression | 51 → 58 tests across 8 → 9 specs |
| Community blueprint footprint | Top-100 catalog + Launch-25 curated packages |
Note: the large insertion volume includes generated blueprint catalog/package artifacts in addition to application code.
How This Compared to “Typical Solo Dev Pace”
A conservative estimate for this scope with one human engineer is 2–3 weeks: feature architecture, UI wiring, persistence, migration work, docs, and full regression coverage. Here, the value of Codex 5.3 was not just speed in typing code. The leverage came from:
- Staying in implementation mode continuously while preserving test discipline.
- Switching quickly between product decisions, coding, debugging, and documentation.
- Keeping a verifiable trail (
/docs/worklogjournal.md) so context did not get lost.
This Was Collaboration, Not Task Dispatch
The most important part of the day was the interaction pattern. We did not run a one-way backlog. We debated quality and credibility:
- You challenged weak UX states (Install should be locked when unavailable), and we corrected behavior at both tile and preview levels.
- You challenged data realism for “inspired-by” systems, and we replaced simplistic seed generation with richer domain-authored package generation.
- You enforced coding contracts, and we ran an explicit compliance audit plus remediation pass before final push.
- You required proof, not promises, so every major change ended with lint/unit/e2e verification.
The real unlock is not “AI writes code faster.” It is “human judgment + AI execution + strict verification” as one continuous loop.
Lessons Learned
- Contracts first, always: when contract rules are explicit, quality issues become detectable and fixable quickly.
- Feature credibility beats feature count: shipping a marketplace means realism, not placeholder parity.
- Tests are collaboration memory: every bug found late became a permanent test so the fix does not regress.
- Worklogs scale agentic development: detailed timestamped logs made long-session continuity possible.
What’s Next
The obvious next move is to raise the “real-world blueprint” bar further: richer domain fidelity, stronger package QA gates, and a true contribution-driven exchange loop where users generate, validate, publish, and learn from each other’s systems.
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