eval-harness

Implements eval-driven development with pass/fail criteria and pass@k metrics for Claude Code sessions.

1|Updated Oct 11, 2025
One-click install
npx skills add https://github.com/ibytechaos/claude --skill eval-harness-ibytechaos
Or copy as Structured Prompt for Agent
Please help me install this Agent Skill.
Skill: eval-harness
Source: https://github.com/ibytechaos/claude/tree/main/plugins/everything-claude-code/skills/eval-harness
Command: npx skills add https://github.com/ibytechaos/claude --skill eval-harness-ibytechaos

SYSTEM DOCUMENTATION & REQUIREMENTS

What problem does it solve? AI-assisted coding lacks a systematic way to verify that Claude Code sessions actually accomplish their goals and that changes do not break existing functionality. This Skill provides a formal evaluation framework that treats evals as the unit tests of AI development, letting you define success criteria before implementation and measure agent reliability quantitatively. ## Core Features & Use Cases - Capability and Regression Evals: Define structured eval templates that test whether Claude can perform new tasks and whether changes break existing behavior. - Multiple Grader Types: Use deterministic code-based graders, model-based LLM-as-judge graders, or human review flags depending on the output being evaluated. - Reliability Metrics: Track pass@k (at least one success in k attempts) and pass^k (all k trials succeed) to benchmark agent performance across model versions. - Use Case: Before adding an authentication feature, define capability evals (user registration, login, session persistence) and regression evals (existing routes unchanged), then run evals after implementation and generate a report showing pass@3 of 100% before shipping. ## Quick Start Ask Claude to define an eval for a new feature using the eval-harness framework, including capability evals, regression evals, and pass@k success thresholds stored under .claude/evals/.

Frequently Asked Questions about eval-harness

High-intent search queries and answers about installing and using this skill.

FAQPage Schema
How do I set up eval-driven development for Claude Code?

Define capability and regression evals before writing code, using the markdown templates provided. Store eval definitions in .claude/evals/<feature>.md, implement the feature, then run the evals and generate a report tracking pass/fail results and pass@k metrics.

What is the difference between pass@k and pass^k metrics?

pass@k measures whether at least one of k attempts succeeds, indicating practical reliability under retries. pass^k requires all k trials to succeed, serving as a stricter stability test recommended for release-critical regression paths.

When should I use a code grader versus a model grader?

Use code graders for deterministic checks like grep patterns, test suites, and build success since they are reproducible. Use model graders for open-ended outputs requiring judgment, such as code structure quality or edge case handling, and human graders for security-sensitive changes.

What pass rate thresholds should evals meet before release?

The recommended thresholds are pass@3 of at least 0.90 for capability evals and pass^3 of 1.00 for regression evals on release-critical paths. These targets balance practical reliability with the stability required for shipping.

What are common eval anti-patterns to avoid?

Avoid overfitting prompts to known eval examples, measuring only happy-path outputs, ignoring cost and latency drift while chasing pass rates, and allowing flaky graders in release gates. Keep evals fast and version them alongside code.