Polymorph

Chrome extension that turns posts matching rules you wrote in English into your own images or GIFs. Jev (TypeSafe System One) is the judge. "Show original" is one click. Nothing is ever deleted — the post is hidden in place and a card takes its spot.

Personal daily driver. Load unpacked. Not on the Chrome Web Store.

Load

1. pnpm install and pnpm build
2. Chrome → chrome://extensions → Developer mode → Load unpacked → dist/
3. Open Options and follow the three steps on screen

Set up (the short version)

1. Add your key — Options → OpenRouter key → paste → Save key. The key goes to chrome.storage.local and only the background worker reads it. Use Test connection to make one real Jev call with fixed synthetic text and see the round-trip time.
2. Enable a rule — the three example rules ship OFF on purpose. Flip Enable rule next to one you want; the chip turns Active and the summary reads "1 of 3 rules active". No rule on means no filtering.
3. Add replacement media (optional) — Options → Replacement media → add PNG, JPEG, WebP, or GIF files from your machine. With media, every matched post draws one of your files at random. With an empty library, matched posts collapse to a one-line card instead. Nothing is uploaded.
4. Open a supported site — X, Reddit, Hacker News, or YouTube. The popup shows a readiness line: "Working here — 1 rule active" or the exact reason it is paused.

The popup has the master switch and a switch for the current site. The options page also edits rules, the media library, and the site list. Default allowlist is X, Reddit, HN, and YouTube (with www./old./m. cousins).

Replacement media

Matched posts become a bounded card (max width 480px, art area at most 120px) with an accessible caption, a rule label, and a keyboard-focusable Show original button.

• Your library — add images or GIFs in Options. PNG, JPEG, WebP, and GIF are accepted. SVG, HTML, and anything that is not a real raster/GIF file are rejected with a per-file message. Limits: 5 MB per file, 200 files, 100 MB total.
• Random, stable draw — each post deterministically draws from the ordered pile (hash of post text + rule id). The same post keeps the same file across re-renders and infinite scroll. A short recency list avoids immediate repeats; removing files can change future draws.
• Empty library — Add images or GIFs to replace filtered posts. Without images, posts are collapsed. Every matched post then renders the compact collapse card, never placeholder art.
• GIF fidelity — animated GIFs play normally. Under prefers-reduced-motion the first frame is drawn once (frozen), or the post is collapsed if a frame cannot be produced; animations never run.
• Where the bytes live — originals are stored in IndexedDB in the extension origin, never in chrome.storage, never base64 in settings, never on a server. The content script renders a local blob: URL and revokes it when the page unloads. Diagnostics record an opaque asset id, never a file name, path, or contents.

Rules

Each rule is a name, an instruction in plain English, and an enable switch. Examples ship off. A good rule names the exception: "political argument, except election-mechanics explainers." Every rule draws from the same media library; there are no per-rule visual categories.

Diagnostics

Options → Diagnostics (also linked from the popup) shows per-tab counters (discovered, queued, evaluated, transformed, skipped, errors, restored), the provider pause state, last activity, and the 100 most recent outcomes: time, host, rule, asset id, duration, error kind, and character count. Post text is never stored — only its length; media names and contents are never stored. Copy diagnostics produces redacted text; Clear empties the ring.

Privacy

• One post per Jev request. Author names, HTML, cookies, and page chrome are never sent.
• The OpenRouter key stays in extension local storage and only the background service worker uses it, only against openrouter.ai.
• Your images and GIFs stay on this machine: no upload, no image CDN, no tracker, no new service, and never sent to Jev.
• Mail, banks, password managers, and local hosts are on a hard denylist: no DOM scrape, no Jev call, no popup override.
• If Jev errors, times out, or is unsure, the post stays visible. After provider failures the worker backs off before trying again.

Develop

pnpm test        # pure-module suite: hosts, gate, policy, cache, marking,
                 # media validation/selection/store/service, migration,
                 # reduced motion, diagnostics
pnpm typecheck   # tsc --noEmit
pnpm build       # icons -> typecheck -> pages/worker -> content IIFE
pnpm verify      # checks dist/ is a loadable MV3 package, no bundled media,
                 # and no unexpected external URLs in shipped code
node scripts/qa/run.mjs --dist ./dist --label local [--full]

pnpm build needs rsvg-convert (librsvg) on PATH to render assets/icons/polymorph.svg into 16/32/48/128 PNGs. The build fails closed if the renderer is missing or a PNG comes out the wrong size.

Source layout:

src/background.ts       service worker: key, Jev, cache, backoff, diagnostics,
                        media library -- the only process that touches IndexedDB
src/content.ts          denylist gate, adapters, marking, media pick, card UI
src/card.ts             shadow-DOM replacement card (user image or collapse)
src/marking.ts          state + text-signature marking (US-010)
src/media/              types, magic-byte validation, IndexedDB store,
                        service, base64 transport, selection
src/jev/                client, gate, cache, key, queue, precheck
src/popup/  src/options/  src/ui/
assets/icons/           polymorph.svg source (branding)
scripts/build-icons.mjs, scripts/verify-dist.mjs, scripts/qa/