GPT-6 Astra at high reasoning effort produced the implementation I decided to keep. I still plan to use medium effort by default.
High handled the interactions between retries and persisted state more completely, but its implementation run took about 48 minutes against medium's 31. In a separate review of the same Sol implementation, medium found a startup failure that high missed.
I ran this comparison to choose a default after GPT-5.6 Sol high.
The work behind the comparison
I used Galley, my tool for unattended development. It takes queued tasks through environment preparation, implementation, and verification. When a task is retried, it should preserve the agent's previous work and reuse preparation that is still valid.
