lastlight-evals-loop

lastlight-evals-loop is a skill for Claude Code from nearform/lastlight. It costs 200 tokens per session (2,785 once invoked), scanned A, original, MIT.

A disciplined process for improving Last Light's pull-request review evaluation score by repeatedly testing changes against known examples. A pull request is a proposed change to a code repository, and an evaluation measures how well the reviewer performs.

In plain words
What is it for?
Run the review evaluation, study missed findings, propose general fixes, retest them on held-out examples, and keep the best candidate.
Why use it?
It helps improve review quality while guarding against changes that merely memorize the test cases or distort the results.

Skill for Claude Code

Written for Claude Code: shipped in a Claude Code plugin. Also seen: mentions subagents; mentions AGENTS.md.

Part of the lastlight plugin — 7 skills shipped together

Good fit Run the review evaluation, study missed findings, propose general fixes, retest them on held-out examples, and keep the best candidate.

Compare 6 skills from other repositories ↓
Install with agentmods
npx agentmods add skills/nearform/lastlight/lastlight-evals-loop
Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

Any agent
npx skills add nearform/lastlight --skill lastlight-evals-loop
Clone the repo
git clone --depth 1 https://github.com/nearform/lastlight

Made for: Claude Code.

Or install lastlight, the plugin that ships this one along with the rest of its 7 skills.

Wrote this? Show the measurements

A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.

agentmods badge for lastlight-evals-loop

README.md
[![agentmods](https://agentmods.dev/badge/skills/nearform/lastlight/lastlight-evals-loop/github.svg)](https://agentmods.dev/skills/nearform/lastlight/lastlight-evals-loop)
Your own site
<a href="https://agentmods.dev/skills/nearform/lastlight/lastlight-evals-loop"><img src="https://agentmods.dev/badge/skills/nearform/lastlight/lastlight-evals-loop/github.svg" alt="Measured on agentmods" height="20"></a>

Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.

agentmods 80×15 button for lastlight-evals-loop

Your own site · 80×15
<a href="https://agentmods.dev/skills/nearform/lastlight/lastlight-evals-loop"><img src="https://agentmods.dev/badge/skills/nearform/lastlight/lastlight-evals-loop.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 200 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 2,785 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe. Third-party audits
  • NVIDIA SkillSpector warn 7 Sept 2026
SkillSpector: 3 findings, up to medium

These are SkillSpector’s own severities. On a checked sample its high-severity flags on skills were ~96% false positives — a documented command, a public API, a “never do X” rule — so we show them as a caution to read, not a verdict. Why →

  • medium MCP Rug Pull · line 86
    npx commands without a version suffix (e.g. @1.0.0) create a rug-pull risk if the upstream server is compromised and publishes a malicious update.
    Fix: Pin the version: npx @scope/[email protected]
  • medium MCP Rug Pull · line 161
    npx commands without a version suffix (e.g. @1.0.0) create a rug-pull risk if the upstream server is compromised and publishes a malicious update.
    Fix: Pin the version: npx @scope/[email protected]
  • medium MCP Rug Pull · line 171
    npx commands without a version suffix (e.g. @1.0.0) create a rug-pull risk if the upstream server is compromised and publishes a malicious update.
    Fix: Pin the version: npx @scope/[email protected]
How audits are shown
Origin original No closer match found in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5.1 $0.00200 $0.02785
Opus 5.5 $0.00080 $0.01114
Sonnet 5.5 $0.00040 $0.00557
Haiku 4.5 $0.00020 $0.00279

Measured 1mo ago against content hash c09da0484307, method: parsed. Prices are Anthropic first-party input rates as of 2026-10-07, from the pricing page.

Security

Grade A, and why

lastlight-evals-loop scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 1mo ago.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

plugins/lastlight/skills/lastlight-evals-loop/SKILL.md · 211 lines

How it starts

The opening of the file, as written. The whole thing — 211 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Improve an eval, honestly

A loop that raises an eval score without gaming it. The trap: the loop can see both the gold answer and the agent's answer for every case, so it could overfit — hardcode a repo's finding into a prompt, or edit a gold answer to force a pass. That lifts the number and ruins the reviewer. Every guardrail here exists to force generic, cross-cutting changes that would help on repos the loop has never seen.

Scope: the pr-review tier (its judge trace gives you the agent-vs-gold detail diagnosis needs). The pattern extends to triage/code-fix, but start here.

The method — weakness-mine → propose a few minimal candidates → keep the one that survives a blind held-out gate — follows Self-Harness: Harnesses That Improve Themselves (arXiv:2606.09498), adapted to keep our anti-gaming discipline. See references/approach.md for the mapping.

Prerequisites

  • A scaffolded evals workspace with a pr-review dataset and a working provider key — set up via lastlight-evals first if you don't have one. Confirm a bare lastlight-evals run pr-review --limit 1 --no-open grades a case.
  • An instance/ overlay (the deployment overlay) to receive generic edits — see lastlight-overlay. The loop edits copies here, never core.
  • Two helpers ship with the evals package: scripts/mine-failures.ts (ranks the TRAIN failure signatures into an evidence bundle — the diagnosis input) and scripts/diff-runs.ts (compares two runs and calls keep/revert).

The one rule

One change kept per round. A round may explore a few minimal candidates, but at most one is ever kept and committed to instance/ — the rest are reverted. So which edit moved the number is always attributable, and no overfit edit rides along with a good one. Never keep two edits from one round without re-measuring each in isolation.

Start here

You have… Go to
Never run this loop on this dataset §1 Set up the split then §2
A split + baseline already recorded §3 Diagnose (mine failures)
Candidate change(s) ready to test §5 Audit → §6 Apply → §7 Measure → §8 Decide

Read the full file on GitHub · 211 lines

Files

What ships with it

4 files beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. 1mo ago First seen · 211 lines · 200 tokens per session scan A c09da0484307

Subscribe to this mod's changes

lastlight-evals-loop is a skill published in the GitHub repository nearform/lastlight (39 stars, last pushed yesterday), licensed MIT. It adds 200 tokens to every session and 2,785 once invoked, about $0.0008 per session on Opus 5.5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.