# Evals-driven development

**Source:** https://promtable.com/glossary/evals-driven-development

> Evals-driven development is the discipline of writing the eval suite first, then iterating prompts and models against it — borrowing test-driven development for LLM work.

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Evals-driven development is the discipline of writing the eval suite first, then iterating prompts and models against it — borrowing test-driven development for LLM work.

Evals-driven development inverts the usual order: define what success looks like, encode it as an automated eval against a golden set, then iterate prompts, models, and orchestration until the evals pass. Adopted widely by serious LLM teams in 2026 because it's the only way to ship reliably — vibe-coding prompt changes without evals breaks production. Mature implementations integrate evals into CI: every prompt change runs the suite, regressions block merges, scores trend in a dashboard. Tools: Braintrust, Langfuse, Ragas, Inspect Evals.

## When to use

- Any serious production LLM feature.
- Teams shipping multiple prompt changes per week.

## Common mistakes

- Building evals after shipping — the prompt baked in regressions you didn't catch.
- Eval set that's too small or unrepresentative of real distribution.

## Related terms

- [evals](https://promtable.com/glossary/evals)
- [ab-testing-prompts](https://promtable.com/glossary/ab-testing-prompts)
- [prompt-versioning](https://promtable.com/glossary/prompt-versioning)
- [vibe-eval](https://promtable.com/glossary/vibe-eval)

*Last updated: 2026-06-01*
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Original page: https://promtable.com/glossary/evals-driven-development
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