Codex Ran for 35 Hours
I gave Codex a task, and it ran continuously for 35 hours to complete it.
A personal record for me.

No /goal.
No skills.
No additional setup.
Just Codex, and talking to it.
It was a decently complex TypeScript CLI for an idea I had been thinking about for months. This was not in our existing product repo, so built from scratch.
I did spend a week on the design and technical details while doing my day job:
- the shape of the idea
- the data model
- the tech stack
- the rough implementation order
- the tests that would prove each part worked
Then on Saturday, I spent a few more hours on the details, and I ended up with 18 implementation steps. 18 PRs, I thought.
Each PR had its own objective and tests, both manual and automated.
Saying manual testing is a bit funny, because there is nothing manual about it. It is asking Computer Use to test scenarios while it monitors the DB and Docker logs.
For each PR, I asked Codex to create a branch, write tests, implement the change, run the tests, review its own code with codex exec, fix the issues, and repeat until the tests passed and the review found no important issues.
Over the last few months, I had built enough muscle with Codex to run 8-10 hour tasks confidently. I knew where it would usually give up, so I applied everything I had learned to this project.
I thought this was a similar task. I was genuinely surprised by how long it ran.
The repo had 4 or 5 PRs before this started. I skipped the approval process for this and asked Codex to merge. The repo was at PR 64 when it finished.
It did not work in one shot though.
There were quirks, and I had to spend another couple of hours getting it to a working version.
I estimated this would take two people at least a couple of weeks, and I could not afford to allocate resources for a project that might be vanity.
I spent a few hours over a week on the idea, and another few hours after implementation to get a working prototype.
I am starting to believe the bottleneck is not the tool anymore, but my ability to understand its capabilities and shape the work.
If I can describe the outcome clearly, split it into testable pieces, and define the exit criteria, Codex can go much further than I expected.
Early in my career, I remember spending 30-35 continuous hours in the office a few times. Prepping for go-live. Resolving some production issues. I remember colleagues staying even longer than I did.
So there was something poetic about this task taking 35 hours. I swear it was not planned.
I started it on Saturday afternoon. It finished late Sunday night.
During that time, I went to watch a movie, went to lunch, and did many other things while just checking Codex progress from my phone.
I still find this hard to believe.
I tried to explain my joy to the folks around me, non-software folks, but obviously, for them, it was not a big deal.
A task that runs for 7 days is my next goal.
Originally posted on LinkedIn.

