Your preview isn’t the inbox.
Your agent says the email looks great, then the Gmail app turns the header pale and the logo never loads. The Email Pack makes it prove the email against the built output and a real send, whatever sends it: Postmark, SureContact, Supabase Auth, WordPress, FluentCRM or anything else that sends custom HTML email.
$39. Every pack, now and later: $149.
Works with
Fit check
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Every requirement, in detailSound familiar?
Tap every one you’ve lived through.
Nothing yet? Check your phone in dark mode.
Why it keeps happening
An agent checks email where it can see it: the source, and a browser preview in light and dark. Apple Mail and the Gmail app repaint colors on their own, and every image loads from your host. It isn’t lying. It checked the preview and reported on the inbox.
So you become the test inbox. You send it to your phone, switch to dark mode, find the header gone gray, and explain it again. And a reviewer who sees a missing logo reads it as a broken email, not a missing deploy.
What the code claimed
The generator shipped color-scheme: light only, with a comment claiming it prevented inversion.What arrived
macOS Mail inverted it anyway. The #0A0D12 header band arrived mid-gray, with a system-link-blue wordmark.
The fix
The Email Pack is two skills your agent loads and seven scripts it runs. The guards read the built email, not the source, and the Supabase build refuses to write a single file that would break in a real inbox.
Readable in light and dark mode, in Apple Mail and the Gmail app. The header band is carried as an image, so an inverting client can’t repaint it, and the body inverts with its text.
Four guards check the logo, the header lock, contrast in both schemes and every image, each with a self-test that must catch a planted defect.
All thirteen Supabase Auth emails come from one file in your repo, pushed with a partial update that changes nothing else, then read back. Your CRM’s drips, Postmark templates and WordPress’s account mail can come from the same generator, so they share one design.
Proof
Three runs of the shipped download, from a fresh unzip. Two guards catch every defect planted in their self-tests, and the Supabase generator refuses a brand color as link text and writes nothing.
[ Shot 01 ]
band-lock-guard.mjs --selftest
Aimed: planted header defects and correct fixes; each must land as designed
ok live text in the band: refused
ok accent border on a locked button cell: refused
ok the locked frame pattern, label as an image, passes: passed
37 cases behaved as designed
Landed where it was aimed // exit 0
[ Shot 02 ]
build-email-templates.mjs, link #C8A84B
Aimed: a brass brand color as link text; the build must refuse it
build-email-templates: refused, nothing written.
- light: link on card is 2.29:1 (#C8A84B on #FFFFFF), needs 4.5:1
Landed where it was aimed // exit 1
[ Shot 03 ]
hosted-asset-guard.mjs --selftest
Aimed: missing and fake images on a local server; each must be refused
ok 404 refused
ok 200 HTML from a catch-all refused
ok zero-byte image refused
18 cases behaved as designed
Landed where it was aimed // exit 0
On real templates
Emails these skills built for our own products and an agency site: purchase and drip mail from a CRM, and a web app’s Supabase Auth mail. Pick one, then drag the handle to compare light and dark.
Choose an email
These are browser renders, not inbox screenshots: Chromium at 640px, in the light and dark color schemes, with sample data and inert links. The dark-mode rules they follow were measured in the inbox apps themselves: the Gmail app’s dark theme pixel by pixel on September 25, 2026, and Apple Mail on a delivered email on August 30, 2026.
Who it’s for
Two skills, one job each. Start with the craft, which works with any sender, and add the Supabase transport if Supabase sends your auth mail.
polarity-sweep.mjs --selftest
ok browser: unhooked chip fails in the dark: 1.05:1, 1.05:1
ok browser: live text inside a locked band fails only in the Gmail pass: gmail-sim,gmail-sim
selftest behaved as designed
polarity-sweep.mjs --selftest
ok browser: unhooked chip fails in the dark: 1.05:1, 1.05:1
ok browser: live text inside a locked band fails only in the Gmail pass: gmail-sim,gmail-sim
selftest behaved as designed
Dark mode that holds in Apple Mail and in the Gmail app, a logo that sits flush on its header, text you can read in both color schemes, and every image live on your host before the first test send.
build-email-templates.mjs (guards not copied)
- scripts/band-lock-guard.mjs is missing. Copy it (and lockup-guard.mjs, which it imports) from the html-email skill
- scripts/hosted-asset-guard.mjs is missing. Copy it from the html-email skill
The thirteen emails Supabase Auth sends, from sign-up to security notices, come from the same generator as the rest of your mail. The build refuses anything that would break in an inbox, and the push changes those templates and nothing else.
Both skills, each with its job in one line. The craft styles email for any sender, with guides for Postmark, WordPress mail and a hosted store; the Supabase transport builds and pushes your auth mail.
html-email
Dark mode, a flush logo, readable contrast and live images, for any sender, proven on the built email and a real send.
supabase-email-templates
All thirteen from one generator, pushed with a partial update and read back field by field.
One download: two skills for Claude Code, the same instructions to paste into any tool that reads AGENTS.md, and checks that prove the built email, its images and your Supabase templates are what you think they are.
email-pack/
install.sh copies both skills into ~/.claude/skills/, or you can load the whole folder as a Claude Code plugin. It copies, never links, and moves an existing folder aside with a timestamp instead of overwriting it.
ci/email-skills.mjs is the pack’s own proof. It runs every guard’s self-test, builds all thirteen Supabase templates in a throwaway folder, holds each to the guards, and plants a failing link color the build must refuse.
A check that has never failed is a green light with extra steps. Each guard here ships a self-test that plants the defects it exists to catch. Run those first: if a guard calls a planted defect fine, don’t trust it on your real email either.
Run the self-tests first
# run from the project you are checking, with the Email Pack unzipped at /path/to/email-packnode /path/to/email-pack/skills/html-email/scripts/lockup-guard.mjs --selftest # must refuse a logo baked one digit off the bandnode /path/to/email-pack/skills/html-email/scripts/polarity-sweep.mjs --selftest # must fail a code chip with no dark rule, in the darknode /path/to/email-pack/skills/html-email/scripts/hosted-asset-guard.mjs --selftest # must refuse a missing image served as a 200 web pagecd /path/to/email-pack && node ci/email-skills.mjs # must refuse a brand color as link text and write nothingWe call these negative controls: a planted defect the check has to fail on. The self-tests plant a logo one digit off its band, a code chip with no dark rule and a missing image served as a 200 page, and each must go red. The harness builds all thirteen Supabase templates, then must refuse a planted link color.
A guard that has never refused anything is not evidence.
The skills are plain text files your agent reads. The scripts are short, commented, and run only on your computer.
claude --plugin-dir /path/to/email-packThe skills need nothing at all. Every script runs on Node 18 or newer alone, except the contrast sweep’s browser pass, which needs Playwright in your project, and the label drawer, which needs Playwright and sharp:
npm i -D playwright sharp && npx playwright install chromiumShort scripts with comments, and nothing compressed into a blob. A product that says “don't trust a report you can't read” has to be readable itself.
Email Pack
$39.
Please don't resell it or share it outside your company.
All-Access Bundle
Spotter Round, the Agent Setup Pack, the Email Pack, the WordPress Pack, the App Stack Pack and the Campaign Tracker Pack, plus every pack added after them, each with every future version.
Yes. The skills are plain text files and the checks are plain Node scripts, so any agent can run them. Claude Code loads the skills from its skills folder. Codex, Cursor and the rest take a skill pasted into your repository's AGENTS.md, and Gemini CLI reads that file once its settings name it.
Yes. FluentCRM sends the custom HTML you give it, and the method is the same for any CRM, in WordPress or outside it, that sends custom HTML templates: the checks read the email you built, not the service that sends it. A FluentCRM guide with a worked example is in the pipeline.
Yes, if you send HTML email. html-email is the craft and sends nothing, so it works with whatever sends your mail, and its guides cover Postmark, WordPress’s own account mail and a hosted store’s emails. supabase-email-templates is the transport for Supabase Auth. If you send through SureContact, the App Stack Pack’s SureContact skill sends the email you build here, byte for byte.
supabase config push?It builds your whole [auth] section from config.toml, fills every key you didn’t declare with a local default, and sends all of it. A file that only declares templates overwrites your Site URL (with http://127.0.0.1:3000), redirect list, rate limits and MFA settings, and its confirmation prompt defaults to yes when it isn’t attached to a terminal. The push here sends only the fields it built, then reads each one back.
No. A browser’s dark mode shows what a client that honors your color scheme does, and the Gmail app repaints colors on its own. polarity-sweep.mjs --gmail-sim applies a model of that repainting, measured in the app, to every color it reads, but the real test is still a send to a Gmail address, read in the app with the phone in dark mode.
No tracking, no license check, no analytics, nothing phoning home. The image guard, and the contrast sweep’s browser, request only the image URLs in your built email. The push talks to your Supabase project only when you run it, with a token you supply. You can confirm that yourself: the scripts are short enough to read.
Run each guard’s --selftest: it plants the defects the guard exists to catch, and fails if one slips through. ci/email-skills.mjs runs all four, builds the thirteen Supabase templates as a buyer would, and plants a failing color the build must refuse. That's the answer we would want from anybody selling us this.
Numbered downloads with a list of what changed. Every future version of the Email Pack is included at no charge, so you never pay for a new version, and you are never forced to update.
Yes — that's what it's for. One company covers every project that company delivers.
Fourteen days, no questions. A product about checking things that argued with you over a refund would be a poor advertisement for itself.
Sold separately
Each pack is sold on its own and ships its own checks, the same way this one does.
The layout, the pixels, the speed and the live deploy: your agent’s work, proven before it says it’s done.
One set of rules, proven to reach every coding agent, several agents on one project without landing work on each other's branches, and API keys handed over without entering the chat.
Bricks 2.4 and later, Automatic.css and SureCart: the WordPress stack, proven rather than assumed, and sign-in screens on brand, including the Fortress security plugin’s two-factor pages.
Cloudflare Pages, Stripe billing on Supabase, passkey sign-in on Supabase Auth, SureContact and OttoKit: the web-app stack, proven rather than assumed.
Campaign tracking set up the same way for every client: short links from a Google Sheet, first-touch UTM tags without cookies, leads and purchases sent to Meta from the server, and cost per lead in one sheet.
Every pack, now and later: web pages, several agents, email, WordPress, web apps and campaign tracking.
The six separately: $234