Mythic Masters: friends walk the open world together, cheap by design, hill climb to 8/10, rounds 6+ (from #3684) #3690

Score: 3.75/10 (target 8, on the owner's scale: agent judges halve their number, per the 2026-11-05 reset)

Carries the climb on from #3684 (round 5), #3679 (round 4) and #3674 (round 3), all in PR #3676, and #3670 / #3663 (rounds 2 and 1, PR #3669, merged); their score comments have the judges' tables.
The owner's brief (2026-11-05): make Mythic Masters' open world multiplayer, and make it awesome, performant and cheap. Today the whole game runs in the page on an assets-only Worker (apps/mythic-masters/rustybuns.config.ts); nothing online but eqosys sign-in (src/account.ts). The 77 × 51 km continent, its regions, trails, dens and hunts are in src/world/ and docs/WORLD-EXPANSION.md. The sibling climb for frame time is #3664.

What awesome means here

You see your friends walking the same land with their bound beasts beside them, you meet them at a den, a mythic you both chase is the same mythic, the Book heckles the party as one, and joining takes one code. Not an MMO: a party of up to six on one region at a time, like a hunting trip.

Goalpost: 8/10 from the owner

1. Walk together. Through an eqosys party code (party in @rustybuns/util/eqosys, Qollab is the connecting layer, eqosys the account) friends land in the same region and see each other move, with their lead beast beside them, at a smooth 60 fps: interpolation and dead reckoning on the page, a low send rate (5 Hz or less, deltas, quantised positions), never a per-frame message.
2. One world. Dens, wild food, flocks and the region's mythic are the same for everyone there: seeded by the room, not by each page, so a hunt one player starts the others can join; a fight is still the page's own sim, its result reported and checked for plausibility.
3. Cheap by design, priced before it ships. One Durable Object per occupied region (never per player) using Sockets from @rustybuns/util/room with WebSocket hibernation, token-checked joins (@rustybuns/util/token), TokenBucket, RoomMintGate and originAllowed from @rustybuns/util/limits, no storage writes per tick (the room keeps state in memory, a save is the player's own page). A cost model in the repo (apps/mythic-masters/scripts/cost.ts) that runs the stress script, counts messages, wake time and storage ops, and prints a price per player-hour from Cloudflare's published Durable Object rates. Target: under $0.005 per player-hour at a full party, printed in every round's comment. No deploy by a worker: the owner runs bun run deploy after a plan (DEPLOYS=1 AGENTS=1 CHECKS=1).
4. Honest offline. Alone, nothing changes: no socket, no cost, the save stays local. A dropped connection degrades to solo play and rejoins without losing the trip.
5. Tested the way people play. One journey test through the running app (local() from test/app-kit.ts) with two pages in one room: both see each other, one leaves and rejoins, a hunt stays shared. A stress script (scripts/stress.ts) that runs six bots walking a region for a minute and prints messages per second and the price.

The loop

Each round is one PR against main that says "Part of #N". Shots and numbers: bun run probe mythic-masters with the mythicMasters handle, two headless pages in one room, frame time and bytes per second per player in the comment. A fresh judge scores the five points, halves it, and the comment starts Score: x/10 (target 8) and ends Next: ...; then open "rounds N+ (from #N)", close this one with "Moved up to #new". At the target, a MANUAL RUN: for the owner's own play with a friend. No Vectorize, no third-party realtime service, no new paid binding without an issue for the owner first.