What Problem This Solves

The sidebar lobster pet's random universe was small enough to exhaust quickly: 12 palettes, one visitor species besides strangers (the crab), a single walk-up entrance, and a Lobsterdex that only ever collects palettes and never gives anything back. Regular users see the whole variety space within days, and the collection has no long game.

Why This Change Was Made

Maintainer request: more random lobsters for the bottom-left lobster, built from a reviewed idea list (shinies as a multiplier, real-genetics palettes, an ecosystem of ledge visitors, and making the Lobsterdex feel alive instead of write-only).

User Impact

All decorative, all client-side, all behind the existing "Lobster visits" toggle; reduced motion keeps its guarantees.

• Shiny lobsters (~1 in 512): sparkle overlay + saturated sheen on any palette, ✦ in the name tooltip, tracked per palette in the Lobsterdex (gold star on the mini).
• Two new palettes: cottoncandy (pastel pink/blue with a slow iridescent drift, after the famous Maine catches, ~0.8%) and lumen (bioluminescent photophores that only really glow in the dark theme, ~2%). Rare names: Taffy and Glimmer.
• Old friends return (~8% of loads): a palette the Lobsterdex already remembers comes back wearing its recorded first-visitor name, waves hello on arrival, and the title reads <name> · an old friend.
• The Elder (~1.5% of loads): scale-3, barnacled, sleepy, mighty-clawed "Methuselah · old as the tides". Never molts.
• Crusher/pincer claw asymmetry (~15%): real lobsters have a crusher and a pincer; one claw renders mighty, the other dainty.
• Freckles (~12%) and seeded eye-glint tints (~30%) for common palettes (rare palettes keep their signature glints; offline grey still wins the cascade).
• New ledge traffic inside the unchanged 9.5% passer gate: a snail (90-second crossing — glance away, glance back, still crossing), a rubber duck, and a jellyfish drifting above the ledge, joining the stranger and the crab. Per-kind crossing durations; the resident reacts mid-cross (friends wave, shy pets peek).
• Entrance variants: rare arrivals descend under a balloon (6%) or pop out of a bubble (7%) instead of walking up.
• Message in a bottle (~3% of loads): washes up on its own clock, pet or no pet; clicking it swaps the tooltip to one of 14 fortunes, then the tide reclaims it.
• National Lobster Day (Sept 25): monocles join the seasonal accessory pool. We do not cook friends.
• Completed-Lobsterdex reward: once all 14 palettes have visited, a quiet golden trim appears along the ledge.

Determinism is preserved: every new feature rolls on its own XOR-salted seeded stream, new look traits append after the existing roll sequence, and all legacy probe seeds (0/2/7/21/42/70/91) keep their exact roles.

Also includes a structural refactor to stay under the max-lines cap: static SVG art moved to lobster-pet-sprites.ts, passer/bottle scheduling into a LobsterLedgeTraffic ReactiveController (lobster-pet-traffic.ts), and rare-load identity resolution into lobster-pet-plans.ts.

Evidence

New variants (live components, probed seeds, dark theme):

Ledge traffic + bottle (crossings mid-ledge; snail + opened bottle in the second shot):

Lobsterdex before / after (12 → 14 palettes, shiny stars):

Real sidebar with a visiting pet and the golden completed-dex trim:

Validation (Blacksmith Testbox, provider blacksmith-testbox):

• pnpm test ui/src/components/lobster-pet.test.ts ui/src/components/lobster-dex.test.ts — 69/69 pass (58 pet incl. 11 new rare-load/plan tests, 11 dex incl. shiny immutability).
• pnpm check:changed — full gate green (conflict markers, max-lines ratchet, format, i18n catalog, typecheck core tests, typecheck UI, lint core).
• oxlint clean on all touched files including the max-lines cap after the module split; oxfmt clean.
• Screenshots captured with a Playwright harness against the e2e mock gateway using deterministic probe seeds (harness not committed).
• Codex autoreview (gpt-5.6-sol, high), four rounds: disconnect-lifecycle and dead-export findings accepted and fixed; one accessibility finding consciously rejected (note below).

Review note (consciously rejected finding): Codex autoreview repeatedly flagged that the bottle is aria-hidden, pointer-only, and tooltip-based. This is intentional and consistent with the whole lobster pet surface: every sprite and interaction here (poke, pet, shoo, names, honorifics, moving-day flavor) is decorative, out of the accessibility tree, and rides the native title channel specifically to avoid an i18n surface. A focusable easter-egg button would inject itself into every user's tab order ~3% of loads, and visible fortune text would create a new localized-copy surface — both worse trades. Documented inline at the showBottle scene comment. The reviewer's other findings (traffic-controller disconnect lifecycle, dead exports) were accepted and fixed.