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Make a bigger coding model earn its place

Use the same acceptance checks to compare model choices, including retries and human review.

FDO.CODES Field Notes 32: EARN THE BIGGER MODEL. Two precise routes through geometric gates end at one lime acceptance node.

Using the most capable model for every coding step is a simple default. It may also spend more than the task needs. Sending everything to a smaller model can create the opposite problem: cheap attempts that become expensive to review and repair.

A useful experiment is to route work by observed performance on your repository. Keep the acceptance standard fixed while changing which model does the work.

Separate the tasks before comparing models

A mechanical rename, a failing-test diagnosis and a change to an authentication boundary are different jobs. Group a few representative tasks by type and consequence. Do not assume a model that formats documentation well will make good architectural decisions.

For an initial trial, choose low-impact changes in an isolated branch. Record the starting revision, task brief and checks. Run comparable tasks under controlled conditions and review the results using the same criteria.

Avoid sending confidential code to a service your organisation has not approved. Model selection includes the deployment and data-handling arrangement, not just capability.

Define escalation before the retry loop

A reasonable experimental policy might allow one attempt and one bounded repair for a narrow task. If a required check still fails, stop and request a human decision or route to a more capable model with the failure evidence. The exact limit is a design choice to test, not a universal best practice.

Do not let the model’s own confidence determine acceptance. Use the actual test results, diff, requirement coverage and human review. A stronger model can also be confidently wrong.

Anthropic describes routing work between specialised paths, including models with different capability and cost. The practical extension is to test that routing against your own accepted changes. Read the routing discussion.

Count the whole bill

For each accepted change, record model usage, repeated context, tool runs and review time. Track rejection and escalation rates as well. Lower token cost is useful only if the total workflow still meets the quality bar.

Some tasks may be cheaper with ordinary scripts. Some may justify the stronger model immediately. Others may benefit from a small model preparing context for a human or a stronger model.

I would keep the first routing table short and revisit it when the model, codebase or task mix changes. The outcome to optimise is a maintainable accepted change, not the cheapest individual response.

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