# STaR Bootstrapping

> Bootstrap reasoning ability by fine-tuning on rationales the model got right.

- **Category**: Agentic AI
- **Subcategory**: Reasoning
- **Canonical URL**: https://designpattern.fyi/patterns/star_bootstrapping/

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## Description
**Intent**: Generate reasoning traces for correct answers, filter to those the model actually got right, fine-tune on those, repeat — bootstrapping reasoning capability from scratch.

**Context**: Writing high-quality CoT rationales at scale is expensive. STaR exploits the fact that when the model gets the right answer, its reasoning trace — however it got there — is a useful training signal. Fine-tune on those traces and the model learns to reason more reliably.

**Solution**: (1) Prompt the model to generate a CoT rationale + answer for each training example. (2) Keep only examples where the final answer is correct. (3) For wrong answers, optionally re-prompt with a hint (the correct answer) and collect the resulting rationale. (4) Fine-tune on the collected rationales. (5) Repeat with the improved model. Requires fine-tuning access. See also: ReST-EM, chain-of-thought, generate-and-test-strategy.



## Use Cases
- Building reasoning capability into a smaller model from a handful of seed examples.
- Domain-specific reasoning (legal, medical, scientific) where human rationale writing is costly.
- Distillation: generate rationales from a large model, fine-tune a small one.






## Trade-offs


### Advantages

- No human-written rationales needed — the model bootstraps from its own successes.

- Iterative improvement — each fine-tuning round raises the bar.

- Works with very few seed examples to kick off the loop.




### Considerations & Drawbacks

- Requires fine-tuning access — not applicable to API-only deployments.

- Wrong answers with wrong rationales are excluded, but wrong answers with plausible-looking wrong rationales can slip through.

- Hint-based rationale collection can introduce shortcut reasoning patterns.







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**Reference**: [Original Source](https://www.agentpatternscatalog.org/patterns/star-bootstrapping/)