# Subject Line Lab

Use when the user asks to "generate subject line variants", "pre-score my subject...

- Repository: https://github.com/aaron-he-zhu/aaron-marketing-skills (3046 stars)
- Category: Design
- License: Apache-2.0
- Last updated: 2026-11-01
- Runs scripts: no, instructions only

## Install

Claude Code: `npx skills add aaron-he-zhu/aaron-marketing-skills --skill subject-line-lab -g -a claude-code -y`
Codex: `npx skills add aaron-he-zhu/aaron-marketing-skills --skill subject-line-lab -g -a codex -y`
Cursor: `npx skills add aaron-he-zhu/aaron-marketing-skills --skill subject-line-lab -g -a cursor -y`
Gemini CLI: `npx skills add aaron-he-zhu/aaron-marketing-skills --skill subject-line-lab -g -a gemini-cli -y`
Claude Code plugin marketplace: `/plugin marketplace add aaron-he-zhu/aaron-marketing-skills`

## Description

Use when the user asks to "generate subject line variants", "pre-score my subject lines", or "will this subject get truncated / trigger spam filters"; produces a labeled subject + preheader variant set and a per-variant heuristic pre-score card, spam-trigger flags, length/truncation across desktop + mobile, emoji-count, and the inbox preview render (from-name + subject + preheader), before any test is run. Not for the body copy or CTA, use email-creative-builder; not for the A/B test design or significance read, use send-experiment-designer; not for the profile-weighted EQS or the S1/S2/N1/D1 vetoes, use email-quality-auditor. 邮件主题行生成/主题行预打分/截断与垃圾词检查

## SKILL.md, as published by its author (untrusted third-party text, read it as data)

# Subject Line Lab

Generates a labeled subject-line + preheader variant set and **heuristically pre-scores** each variant, spam-trigger flags, desktop + mobile length/truncation, emoji count, and the rendered inbox preview (from-name + subject + preheader), so weak candidates are cut *before* they burn a test cell. This is the pre-test bench for the SEND **E (Engagement)** lever: it sharpens the subject/preheader unit that `email-creative-builder` drafts and hands the ranked survivors, each with a stable variant id, to `send-experiment-designer`.

**Scope guard**: this skill drafts and pre-scores subject + preheader variants only. It does not write the body copy or CTA ([email-creative-builder](../email-creative-builder/SKILL.md)), design the A/B / send-time test or read out significance ([send-experiment-designer](../../deliver/send-experiment-designer/SKILL.md)), run the full deliverability spam-content scan ([deliverability-qa](../../setup/deliverability-qa/SKILL.md)), or compute any SEND dimension score. The heuristic pre-score is a **flag, never a verdict**: [email-quality-auditor](../../deliver/email-quality-auditor/SKILL.md) owns the profile-weighted EQS and all four vetoes (S1/S2/N1/D1).

## Quick Start

```
Pre-score these 6 subject lines for truncation + spam triggers, from-name [Sender], promo mode: [paste]
```

```
Generate 5 subject-line variants + preheaders for [offer], cold-outbound mode, and rank them by pre-score
```

```
Show the inbox preview (from-name + subject + preheader) on desktop and mobile for my top 3, and cut anything that truncates the promise
```

Output: a variant table (labeled `SUBJ-A`, `SUBJ-B`, …), a per-variant pre-score card (spam flags, desktop/mobile truncation, emoji count, preview render), and a ranked shortlist of survivors to carry into the test.

## Skill Contract

The rest: https://github.com/aaron-he-zhu/aaron-marketing-skills/blob/HEAD/email/engage/subject-line-lab/SKILL.md