stardust:replica — same-design migration

Same pages, same content, same design — new platform. replica migrates a site to AEM Edge Delivery (or just re-platforms its front end) keeping the current design near pixel-perfect: the target spec IS the captured current state, the only permitted deltas are the entries of an explicit inconsistency register, and every archetype must pass a measured source-fidelity gate against the live site before anything ships.

Two properties make this a different animal from the redesign pipeline:

1. No creative decisions. The direction step is mechanical promotion of the captured spec — stardust:direct is never invoked. Every judgment call in a replica run is a measurement-policy call, not a taste call.
2. Recreation, not copying. Archetypes are authored as clean semantic HTML/CSS from captured content + values lifted from the source site's own CSS — never DOM copies, never ported page-level stylesheets. Fidelity is proven by instruments, not asserted by construction.

Validated end-to-end (a typographic retail home page, 2026-07-03): 8.31% → 2.93% → 1.31% pixel diff in 3 measured iterations, height Δ 0, content-diff "findings: none" (198/198 nodes). Every fix came off the instruments, never off eyeballing.

Inputs

• <URL> — required. The site to migrate.
• --breakpoints <list> — optional. Gate breakpoints, default 1440,360. Mobile is NOT free: the validation run's 1440-tuned prototype measured 24% at 360. Each breakpoint gets its own gate pass.
• --register <file> — optional. User-supplied inconsistency items to seed the register (see Phase 2). Without it and without an audit, the register is empty — a pure replica.

Setup

1. Run the master skill's setup (../stardust/SKILL.md § Setup): context loader, state read.
2. Verify Playwright is importable from the project root (extract needs it; so do the gate scripts).
3. Install the gate's pixel deps in the project: npm i -D playwright pixelmatch pngjs --no-save --legacy-peer-deps. Same trap as diff's prereq 0: a --no-save install is PRUNED by any later real npm i — re-probe before every gate run (node -e "import('pixelmatch').then(()=>process.exit(0))").
4. Copy scripts into the project and run them from there, not from the plugin: this skill's whole scripts/ dir (stitch-shot, pixel-compare, crop-compare, chrome-parity, row-profile, sibling-variance, anchor, gate.sh, motion-observe) AND the whole ../diff/scripts/ dir (the diff scripts import diff-profiles.mjs, and ALL live-target hardening — including stitch-shot's — lives in its live-session.mjs; stitch-shot resolves it from scripts/diff/ next to scripts/replica/, so keep the two dirs siblings).

Procedure

Five phases. Phases 1 and 5 delegate to existing skills unchanged; phases 2–4 are owned by replica.

Phase 1 — EXTRACT (delegate to stardust:extract --prep --dynamics)

Invoke stardust:extract <URL> --prep, unchanged. Prep mode is required — replica consumes the full migration inventory, not the discovery cap:

• stardust/current/pages/<slug>.json — per-page structure + content (verbatim source of every string the prototypes will carry).
• stardust/current/assets/screenshots/ — per-page captures (ground truth for recreation, alongside the gate's own stitched shots).
• stardust/current/assets/ — fonts (network-intercepted woff2), logo, media.
• stardust/current/PRODUCT.md, DESIGN.md, DESIGN.json — the descriptive current state (Phase 2 promotes these verbatim).
• state.json.pages[].type — page types (each becomes one archetype).
• DESIGN.json.extensions.modules[] — module candidates (become blocks).

Bounded/single-page entry (one-page or pilot runs). --prep is the site-wide contract; it is NOT the only way in. When the ask is "replicate just this page" — or the user wants to pilot one archetype before committing to a full migration — invoke stardust:extract <URL> --single (or --pages <slug,...> for a short list) instead. This is a first-class entry, not an improvisation: the recreation phase needs, per page, the captured page JSON (verbatim content), the per-page screenshot (ground truth), and the captured fonts — all of which a bounded extract provides; the source-CSS harvest and per-breakpoint computed styles come from Phase 3's CSS lifting either way. What a bounded run skips is the prep-only inventory (page typing, module detection), which is only needed when Phase 5 fans out to siblings — a pilot that later grows to site scope re-runs Phase 1 with --prep. A bounded run also skips the descriptive synthesis: crawl.mjs alone writes pages/<slug>.json, screenshots, and _crawl-log.json — it does NOT produce current/PRODUCT.md / DESIGN.md / DESIGN.json, so Phase 2's verbatim promotion has nothing to promote. On this path Phase 2 takes the bounded promotion branch instead (reference/preserve-direction.md § 1a): replica synthesizes a minimal descriptive target spec from the captured page JSON + the Phase-3 CSS lift, marked provenance: bounded-single.

Extract's failure modes apply as-is (bot-management headed fallback, consent handling, no-synthesis rule). If extract had to fall back to headed Chrome, expect the gate captures to need the same treatment.

Phase 2 — PRESERVE DIRECTION (mechanical — never invoke stardust:direct)

Full contract: reference/preserve-direction.md. Summary:

1. Promote stardust/current/PRODUCT.md, DESIGN.md, DESIGN.json verbatim to the project root as the target spec. No divergence roll, no re-direction, no Mode A/B — the current state IS the target. Bounded entry (--single/--pages): those files don't exist — take the bounded promotion branch instead (reference/preserve-direction.md § 1a): synthesize a minimal descriptive spec from the captured page JSON

   • the Phase-3 CSS lift (palette, type ramp, container, buttons — exactly the values the lift produces anyway), provenance bounded-single. Never mix the branches: if current/PRODUCT.md exists, promotion is verbatim.

2. Write stardust/direction.md recording preserve mode: what was promoted, from where, provenance (verbatim --prep promotion vs bounded-single synthesis), and the register pointer. This is what tells downstream skills "the direction step happened".

3. Build the inconsistency register at stardust/replica/inconsistency-register.md — the ONLY permitted design deltas, the "almost" in almost-pixel-perfect. Sources: stardust:audit design findings (run audit only if the user wants improvement candidates) and/or user-supplied items (--register). Every entry needs captured evidence + the minimal change + a status. Empty register = pure replica — that is a valid and common outcome, not a failure.

4. Dynamic surface (migration gate — stardust:dynamics Phases 1–3). Phase 1 must have run extract --dynamics. Run the detector on the archetypes, draft the triage (--target-origin when the EDS host is known), curate stardust/dynamic-features.md + -plan.md. Every row gets a disposition; the static recreation continues regardless. This is what surfaces modals, players, forms, search, tags and host-bound APIs that pixel gates certify as correct. Contract: skills/dynamics/reference/triage.md.

Anything not in the register is out of scope for change. When a recreation choice would "improve" something not registered, it is a fidelity bug.

Phase 3 — RECREATE (one archetype per page type)

Full method: reference/recreation-procedure.md. For each page type in the inventory, author stardust/prototypes/<slug>-proposed.html (+ per-page CSS) as clean semantic HTML/CSS from three sources, in this order:

(a) Captured page JSON content — verbatim. Headings, body, CTAs+hrefs, alt text, metadata from current/pages/<slug>.json. The migrate content-preservation rules (../migrate/reference/content-preservation.md) apply from the first line: no rewording, no fabrication. (b) Exact values lifted from the source site's own CSS. Fetch the live stylesheets; lift container max-widths, the type ramp, button specs, section paddings, radii, shadows, hero heights, the container model. Fidelity values come from the original site's CSS, not the eye — this converts 3–4 guess-and-screenshot loops into one. (c) The captured screenshot as ground truth for everything CSS doesn't name (composition, image crops, paint effects).

Every archetype gets its own standalone prototype — cumulative, never skipped. Never skip to direct platform authoring for a new archetype: prototyped archetypes stayed the quality ceiling in the field (3.5%/5.6%) while direct-authored pages plateaued at 8–16%. Each new prototype imports the shared layers earlier ones already gated (shared canon CSS + a per-archetype file) and iterates only on its NEW modules — full contract: reference/recreation-procedure.md § Cumulative archetype prototypes.

This is recreation, not redesign — do NOT delegate to impeccable craft. Impeccable's redesign gates (critique, anti-template, divergence) do not apply; the source-fidelity gate (Phase 4) replaces them entirely. A "tastefully improved" section is a failing section.

Fonts: use the same public source when available (extract's intercepted woff2 for open/self-hostable faces). For licensed commercial kits: never rehost on the new domain — pick a metric-matched substitute, keep the brand family name first in the font stack so a licensed drop-in later wins, and surface the substitution to the user. (Prior art: an earlier airport-site migration's improvement notes, §3.7.)

CSS-portation is the per-section fallback only — paint-level effects not recoverable from computed styles, JS-hydrated commerce widgets, video or animated heroes. Port the minimal source rules for that section, scoped; never page-level. Criteria in reference/recreation-procedure.md § Fallback.

Phase 4 — SOURCE-FIDELITY GATE (the heart — measured, per breakpoint)

Full contract: reference/source-fidelity-gate.md. Run per archetype, per breakpoint (default 1440 AND 360), live URL as source vs served prototype:

PROTO="http://localhost:8791/<slug>-proposed.html"   # python3 -m http.server from the prototypes dir
# verify the port is YOURS (lsof -nP -iTCP:8791 -sTCP:LISTEN) — a stale foreign
# server silently poisons the gate (gate.sh asserts a page marker, exit 4)
LIVE="https://<site>/<path>"

# Probe 1+2 — the diff skill's two probes, generic profile (--dismiss keeps
# consent + timed marketing modals out of both inventories)
node scripts/diff/content-diff.mjs "$LIVE" "$PROTO" --profile generic --width 1440 --main "<content-root>" --dismiss
node scripts/diff/visual-diff.mjs  "$LIVE" "$PROTO" --profile generic --width 1440 --main "<content-root>" --dismiss

# Probe 3 — replica's pixel probe (stitched captures, NEVER fullPage:true)
node scripts/replica/stitch-shot.mjs "$LIVE"  stardust/replica/gates/<slug>-1440/live.png  --width 1440 --settle
node scripts/replica/stitch-shot.mjs "$PROTO" stardust/replica/gates/<slug>-1440/proto.png --width 1440
node scripts/replica/pixel-compare.mjs stardust/replica/gates/<slug>-1440/live.png \
  stardust/replica/gates/<slug>-1440/proto.png --out stardust/replica/gates/<slug>-1440/diff.png

# Iteration inner loop (gate doc § Band breakdown): anchor probe + pixel round
node scripts/replica/anchor.mjs "$PROTO" --width 1440   # build-side runs are free
# Chrome: computed-style parity BEFORE any pixel round on header/footer/strips
node scripts/replica/chrome-parity.mjs "$LIVE" "$PROTO" --width 1440   # exit 0 = quiet, then crop-compare
scripts/replica/gate.sh <slug> "$LIVE" "$PROTO" 1440 iter2

Pass bar (all four, per breakpoint):

• content-diff: 0 structural 🔴 (🟡/🟠 confirmed intended);
• visual-diff: flags none or justified;
• pixel diff: ≤ 10% full-page, with no per-500px band left unexplained (the band breakdown is the navigation instrument — fix the first hot band, top-down; everything below it is offset-contaminated);
• height delta |Δ| ≤ 8px (pixel-compare's own warning bar).

Iteration discipline: hard cap 3 iterations per breakpoint. Each iteration's fixes come off the instruments, never off eyeballing. After 3, log the residuals in the ledger and move on — a documented 2% residual beats an undocumented fourth loop.

Hardening (each is a recorded false-measurement trap — see the reference doc for the full list): real-Chrome UA plus the standard request headers on every capture (built into the shared diff/scripts/live-session.mjs — the default HeadlessChrome UA gets a Cloudflare challenge that the probes then silently measure AS the source, and the UA alone still 403s on Akamai); a challenge/blocked interstitial fails loud (exit 3), never measured — escalate with --headed, and a site that still blocks needs crawl.mjs-class capture (the gate must not silently degrade); domcontentloaded on live targets, never networkidle; symmetric --main scoping on both sides (--main body is never valid); both overlay classes dismissed via --dismiss (consent AND timed marketing modals); animations frozen for capture; the pointer parked after any dismissal click (a :hover-styled element under the resting cursor captures in hover state); fixed/sticky chrome replicated fixed, with its scroll-state morph, so seam repeats stay symmetric (reference/recreation-procedure.md § Fixed and sticky chrome); granularity-parity policy for JOIN/SPLIT false-reds (#87); capture-state policy for CDN-403 images and hydration placeholders (replicate as captured

• log). Two defect classes only the gate catches — DOM/style capture misses them: rendered-face font forks on inner spans (width probe) and overlay scrims invisible to computed styles (recover by per-row luminance fitting).

The live-target hardening ships as flags on the diff scripts (--ua, --wait-until, --dismiss, --headed, --locale, visual-diff --main) backed by live-session.mjs — copy the scripts and pass flags; a project copy carrying hand-edits is a defect (reference/source-fidelity-gate.md § Script adaptations).

After the static gate passes, interaction parity is a REQUIRED gate output per archetype — not a post-pass (reference/recreation-procedure.md § Interaction parity; optional, it was skipped on 5 of 7 archetypes — all shipped static). Motion is OBSERVED, never inferred from static classes or CSS: run scripts/replica/motion-observe.mjs per archetype live URL → stardust/replica/motion/<slug>.json, implement ONLY behaviors that fired (dead classes = NOT implemented), record motion: {observed, implemented, dead[]} in progress.json, and re-run pixel-compare — the number must return to the gated value. Widgets are implemented, not justified away. Fan-out briefs carry the evidence rule + instrument invocation verbatim.

When all breakpoints pass, present the archetype + its gate metrics for approval per the standard prototype approval flow (hands-off mode records approvedBy: "hands-off" per ../stardust/reference/state-machine.md).

Phase 5 — HANDOFF (delegate — migrate → deploy → rollout, unchanged)

• Pages beyond the archetypes go through stardust:migrate at sibling tier (../migrate/reference/fidelity-tiers.md): structural clone of the gated archetype + content-fidelity + delivery-lint + media-reconcile. Siblings inherit the archetype's source-fidelity gate — never re-author one from scratch. Template constancy is measured, not assumed: before cloning, run scripts/replica/sibling-variance.mjs <archetype> <siblings…> --probe <block>=<sel> … once per template and budget every delta as a block VARIANT class on the sibling's content (same file, § Sibling variance probe). Content-fidelity is measured per page at import time (same file, § Content-count acceptance) so importer bugs surface while cheap to fix.
• Delivery via stardust:deploy per page. Bias the decode tier toward template-slotted for fixed-composition sections (deploy #95): replica sections are fixed compositions matched to a live original. Repeat groups (cards, listings) stay reconstructive. Blocks obey the Experience Workspace editability contract (deploy § 8, EW1–EW10: node-slotting, never value-slotting) and pass block-roundtrip --ew.
• Site-wide rollout via stardust:rollout, unchanged — its block dedup is what implements "same blocks across the whole site".
• The final gate runs against the PUBLISHED origin — not the harness (reference/source-fidelity-gate.md § The published-origin gate): the delivery pipeline transforms markup, so harness numbers understate. Re-run the full gate per delivered page against the preview/live origin, judged in the published-origin regime; only the published number counts.

State: replica writes its own state under stardust/replica/ — the inconsistency register, progress.json (per page type: archetype slug, iterations used, per-breakpoint gate results, residuals, motion inventory), motion/<slug>.json, and gates/<slug>-<width>/ evidence. Pipeline status (extracted → prototyped → approved → migrated) stays in the core state.json per the standard state machine — replica never redefines it.

What replica never does

• No redesign. No new palette, type, spacing, composition, motion. The target spec is the captured current state.
• No content rewriting. Captured strings are verbatim; placeholders and hydration states are replicated as captured, not "fixed".
• No invented improvements. A change without an inconsistency-register entry is a defect, however tasteful.
• No DOM copying. Never paste the live DOM or port page-level CSS as the prototype (that's the snowflake escape hatch, not this skill). Clean re-authoring is the point — byte-fidelity without re-implementation value defeats the migration.

Outputs

stardust/
├── state.json                          ← core state machine (unchanged contract)
├── direction.md                        ← preserve-mode record (Phase 2)
├── current/                            ← from extract --prep
├── prototypes/<slug>-proposed.html     ← gated archetypes (one per page type)
├── replica/
│   ├── inconsistency-register.md       ← the ONLY permitted design deltas
│   ├── progress.json                   ← per-page-type ledger: iterations, gate results, residuals, motion inventory
│   ├── motion/<slug>.json              ← motion-observe evidence
│   └── gates/<slug>-<width>/           ← live.png, proto.png, diff.png, probe outputs per iteration
└── migrated/                           ← from migrate (Phase 5)

PRODUCT.md / DESIGN.md / DESIGN.json    ← promoted verbatim from current/ (Phase 2)

References

• reference/preserve-direction.md — mechanical promotion contract + inconsistency-register entry schema.
• reference/recreation-procedure.md — CSS-lifting method (per gate breakpoint), fonts policy, scrim/luminance recovery, span-face forks, capture-state policy, wrap-junction margins, fixed/sticky chrome, granularity parity, role parity (mirror the live wrapping per string), interaction parity (motion observed, never inferred; Swiper-lock), CSS-portation fallback criteria.
• reference/source-fidelity-gate.md — full gate contract: commands, thresholds, per-breakpoint procedure, hardening rules, band-breakdown reading guide (+ the section-anchor inner loop), iteration discipline, the published-origin gate (EDS pipeline deltas), residual logging format.
• ../diff/SKILL.md — the two probes replica reuses (--profile generic); reading content-diff output; the #87 JOIN/SPLIT limitation.
• ../extract/SKILL.md § Prep mode — what Phase 1 provides.
• ../migrate/reference/fidelity-tiers.md — archetype/sibling model Phase 5 hands off to.
• ../deploy/SKILL.md § decode tiers (#95) — template-slotted bias.