Reasoning controls and migration
o3-mini exposes reasoning effort controls; Sonnet 3.7 introduced standard and extended thinking modes. When migrating, test how your adapter handles reasoning output, structured responses and tool messages. Keep prompts and acceptance tests fixed while changing one configuration at a time. A higher thinking budget is not a guarantee of a correct patch.
Cost for a fixed token workload
At the documented rates, 1M input plus 1M output costs $5.50 for o3-mini versus $18 at Sonnet 3.7 launch rates. This excludes caching, batch discounts, retries and tools. Actual task cost depends on generated reasoning and repeated calls; compare the final accepted patch bill rather than input price alone.
Test multi-file contracts
Use a refactor that touches a caller, implementation and test fixture. Ask each candidate to preserve the public API and document an empty-input policy. Inspect imports, error handling and fixtures after execution. Do not compare vendor benchmark percentages unless the dataset, harness and reasoning settings match.
Check lifecycle before new adoption
The OpenAI model page labels o3-mini deprecated. Sonnet 3.7 prices here describe its original release rather than a promise of current service. For existing deployments, inventory model IDs, run replacement candidates against regression tests and stage the migration. For new projects, verify supported models and rate limits with the provider before choosing this older pair.