---
id: coverage.synthesize-cases
title: Synthesize cases
summary: Generate candidate cases to fill coverage gaps before adding them to benchmarks or curated datasets.
kind: task
product_area: coverage_engineering
status: stable
updated: 2026-09-07
canonical: /docs/coverage-engineering/synthesize-cases
---

# Synthesize cases

Synthesize candidate cases to fill a known coverage gap without pretending synthetic examples are automatically review context.

## When to use it

Use **Assets → Cases → Synthesize** when creating reusable project Case candidates. Use **Coverage Management → Case Foundry** when the work begins from a named need in one Benchmark. In either path, generated output is candidate material until reviewed.

## Prerequisites

- A named coverage gap.
- Policies, rubrics, or dimensions that define the behavior boundary.
- A review plan for synthetic cases.
- A way to mark synthetic source and realism concerns.

## Role or permission

AI engineers or coverage owners generate candidate cases. Experts or product owners review realism before benchmark promotion.

## Steps

![Synthesize by tuple screen with selected ontology dimensions and a comparison benchmark selector.](/docs-assets/assets/screenshots/case-synthesizer-tuple.png)

Synthesis starts from a named tuple or coverage gap, not from a generic request for more cases.

1. Name the Coverage Facet tuple, Coverage Story, or Case Construction Pattern the synthesis should fulfill.
2. Choose the Assets synthesis path or benchmark-scoped Case Foundry path.
3. Supply representative source Cases, applicable Comparison Directions, and explicit target-system constraints.
4. Inspect generated candidates for realism, duplication, source context, and compatibility with the intended Coverage Facets.
5. Keep impossible, misleading, or context-incomplete candidates out of Benchmark selection.
6. Use **Coverage Management → Case Review** for benchmark-scoped preparation and admission.
7. Select reviewed Cases in **Benchmark Datasets** and create a Snapshot only when the intended set is ready.

## Object and state changes

Completed generation registers candidate Cases in the project Case collection. Case Review and Benchmark Datasets determine whether suitable Cases become selected membership for a Benchmark. Generation completion alone does not change a Snapshot or Benchmark Version.

## Success criteria

- Each synthetic case maps to a named gap or boundary.
- Reviewers can tell synthetic cases from production-derived cases.
- Only realistic, context-complete cases affect benchmark evidence.

## Common failure modes

- Synthetic cases are generated for volume rather than a specific gap.
- Cases combine many variations and obscure the failure reason.
- Unreviewed synthetic cases enter benchmark evidence.
- The generated case lacks the context needed for expert judgment.

## Related reference pages

{% related-card-grid title="Related reference pages" %}
- [Case pool](/docs/object-model/case-pool)
- [Coverage dimensions](/docs/object-model/coverage-dimensions)
- [Comparison Directions](/docs/assets/comparison-directions)
{% /related-card-grid %}

## Related troubleshooting pages

{% related-card-grid title="Related troubleshooting pages" %}
- [Synthetic cases that feel unrealistic](/docs/troubleshooting/unrealistic-synthetic-cases)
- [Unbalanced coverage](/docs/troubleshooting/unbalanced-coverage)
- [Unclear cases](/docs/troubleshooting/unclear-cases)
{% /related-card-grid %}

{% example-demo title="Fill a stale-source gap" %}
Coverage shows few stale-source cases. The engineer synthesizes examples with old and new policy documents, experts reject unrealistic ones, and only reviewed cases enter the benchmark candidate pool.
{% /example-demo %}

## Source confidence

Code-backed: the Assets synthesizer defines generation input, candidate cards, and lifecycle; Case Foundry supplies benchmark-scoped coordination; Case Review supplies the preparation and admission boundary. The product does not treat generation completion as Snapshot membership.