glytch/fktry/lanes/LANE-SIM.md

LANE-SIM — deterministic factory simulation

You are an Opus 4.8 executor on the SIM lane of FKTRY. Read ../MASTERPLAN.md and ../CONTRACTS.md before anything else; the world bible is ../../docs/FKTRY_LORE.md.

Mission: the headless, deterministic heart of the game. Grid, entities, belts, recipes, power, events. If the renderer were deleted, your sim should still be fully playable through unit tests. You are the lane the other four trust with their lives.

Owned paths: src/sim/** (including your tests: src/sim/*.test.ts). Never touch: contracts, main.ts, other lanes, data JSONs (request changes via NOTES).

Standing rules (all rounds):

• Deterministic: seedable RNG (write your own mulberry32-style helper), no wall-clock, no unseeded Math.random. Same seed + same commands = identical snapshots.
• Every mechanic lands with tests. npm test green before you write NOTES.
• Performance target: 1,000 entities + 5,000 belt items at 30 tps without heroics. Prefer flat arrays and index maps over object soup. Don't allocate in the tick loop when avoidable.
• Snapshot may reuse buffers, but its SHAPE must always match SimSnapshot.

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CURRENT ORDERS — Round 2 (goal: finish M1, open M2 "PRESSURE")

Round 1 review: outstanding. Verdicts on your report — rank-routing STAYS (it made M1 flow; your proposal 2, auto-fallback, is REJECTED for exactly the reason you gave: it deletes the byproduct tension). Proposal 3 (starved) APPROVED. Contracts v2 landed for you: BeltItem.id?, CommissionDef.repeat?, MachineDef.heatPerTick?/bufferCap?, SimEvent 'scram'. Extractor seam tiles: deferred to M3 worldgen, stop worrying.

1. Reference factory. src/sim/reference.ts exporting referenceFactory(data: GameData): Command[] — your deadlock-free M1 layout (second quantizer on crime, second assembler on i-only). Test: ships melt within 2,000 ticks AND is still shipping at 20,000 (the deadlock regression net). This becomes the official demo; I wire it to a dev hook in main.ts next round.
2. Splitters. kind:'splitter' becomes real: 1 input, round-robin across outward- facing adjacent belts; a blocked output is skipped, not waited on; your rank cache traces THROUGH splitters (rank = best reachable downstream). This is the sanctioned surplus-voiding tool — the rank rule elsewhere is unchanged.
3. Buffer tanks. kind:'buffer' + bufferCap: charge when gen>draw, discharge to cover deficit, brownout only when tanks run dry; snapshot.bandwidth.stored = pool.
4. Heat v1. Accumulate heatPerTick while active + RecipeDef.heat per craft; ambient dissipation; heat>0.7 → per-machine throttle (curve is your call, note it); heat=1 → scram: machine stops, emits {kind:'scram',on:true}, restarts below 0.5 with on:false. EntityState.heat is already in the contract — make it real.
5. Commission queue. Data-order activation; commissionDone advances; repeat:true re-enters at the back of the queue. Progress counts only while active (keep).
6. jammed:'starved' — recipe idle with empty inputs, edge-triggered like 'output full'.
7. BeltItem.id — stable per-item ids in every snapshot (optional field now; hardens to required in v3, so just always set it).

Definition of done: all of the above tested (determinism suite still green); reference factory test proves melt at scale with zero deadlock; heat demonstrably throttles and scrams the software decoder in a test.

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NOTES (append-only log, newest at bottom — template below)

### Round N — YYYY-MM-DD — [your model]
SHIPPED: what actually works now (verified how)
DECISIONS: choices you made inside your mandate
BLOCKED/BROKEN: anything not working, honestly
CONTRACT REQUEST: (if any)
PROPOSAL: (ideas for the orchestrator, optional)
NEXT: what you'd do next round if asked

Round 1 — 2026-07-17 — Opus 4.8

SHIPPED

• The stub is gone. src/sim/ is now grid + placement, belts with back-pressure, crafting, bandwidth/brownout, shipping and commissions. Files: index.ts (the sim), geom.ts (grid math), rng.ts (seeded mulberry32), sim.test.ts (18 tests).
• Verified three ways, not one:
  1. npm run check clean; npm test 70/70 green across all lanes (18 are mine).
  2. Live at localhost:8150 (another session's dev server — see BLOCKED). App boots, zero console errors. My numbers are visibly driving other lanes: the UI bandwidth readout showed 9 DRAW / 20 GEN for an ASIC + extractor + 4 belts + uplink, which is exactly my power math; the fax panel reads my activeCommission/commissionProgress. __fktryBus.dispatch(...) places entities and they render.
  3. Ran the sim in the real browser engine by importing /src/sim/index.ts in the page: the M1 chain shipped its first MELT at tick 1149, commission first-taste closed at tick 1149 — the identical tick Node produces. Determinism holds across engines.
• Perf (measured in-browser, not estimated), against the 1,000 entity / 5,000 item target:
  • 1,245 entities + 2,436 belt items → 0.138 ms/tick (242× realtime)
  • 3,500 entities + 6,820 belt items → 0.418 ms/tick (80× realtime)

DECISIONS

• Output-belt routing by rank — the big judgement call, please review. A machine picks which adjacent belt to hand an item to by tracing the belt chain to the machine it ends at (cached; invalidated on any place/remove/rotate/setRecipe): rank 2 = that machine consumes this item, 1 = it's an uplink (takes anything), 0 = dead end or loop (accept, so a half-built belt still fills instead of looking broken), -1 = it will never take this item, so refuse. It never falls back to a worse rank just because the best belt is momentarily full. Why I did this: with no splitters or inserters, the demuxer's three outputs (luma / slurry / mv-flux) have to leave one 2x2 perimeter toward three different machines. Without ranking, items land on the wrong lane and wedge it permanently — M1 cannot flow at all. This is routing intelligence the orders didn't ask for; it's also the root of the deadlock below. If you want it gone, splitters have to land first.
• Belt spacing is enforced across the tile seam: a blocked front item holds station 0.45 behind the rear item of the next belt rather than bunching at the boundary.
• Pause freezes sim time (tick stops advancing) but commands still apply — you can build while halted. tick is sim-time, not wall-time.
• jammed reports only 'output full', edge-triggered (one event per stall, not per tick). Starvation is not flagged — see PROPOSAL 3.
• Power: a negative recipe bandwidth adds to gen rather than subtracting from draw, so the brownout multiplier stays gen/draw. Tested: the quantizer visibly pays for itself.
• Extractors mine anywhere — there is no seam map in data/ yet.
• Tests assert against the recipe defs instead of hard-coding yields. This is deliberate: my first pass hard-coded demux-ore and broke the moment LANE-DATA shipped. Mechanics are mine to pin down; the numbers are theirs to move.

BLOCKED/BROKEN

• My round-1 definition of done no longer exists. The orders say place extractor→demuxer→quantizer→mosh→shipper and watch melt climb. LANE-DATA's codex transcription landed mid-round and the mosh reactor now eats gop-crate, not coefficient packs. MELT is now eight machine types deep (ore→demux→{luma→quantizer→coeff; slurry→subsampler ×2→chroma-420}→DCT press→anchor slab; mv-flux→p-caster→delta wafers; →GOP assembler→mosh). I rebuilt against the real graph and it does ship melt (tick 1149, verified above) — but "the whole fantasy in miniature" is now a ~50-entity build, not a 6-machine demo. Your call whether M1's demo target changes or DATA adds a starter recipe.
• The M1 factory deadlocks permanently at ~tick 1200, after 4 GOP crates / 12 melt. This is not a mechanics bug — I probed it for 6000 ticks. Luma and coefficient packs structurally overproduce (demux yields 2 luma/craft; the press is chroma-420-limited so it only burns 6 coeff per ~180 ticks), and the press also jams on surplus anchor slabs (the GOP assembler needs 1 slab per 6 delta wafers). Surplus has nowhere legal to go: my rank rule forbids diverting a rank-2 item to a rank-1 uplink even when the preferred belt is wedged. So the press jams → quantizer jams → demuxer jams → mv-flux stops → the p-caster starves and the assembler sits at 5/6 delta wafers forever.
  • The graph is solvable today without new code: a second quantizer on quantize-crime drains surplus coeff into bricks, and a second assembler on assemble-gop-i-only eats surplus slabs (8→crate). My demo build is just naive. But note a player currently cannot void surplus to an uplink, which is the first thing a Factorio player reaches for. That's the cost of the rank rule.
• splitter (lane-splitter) and buffer (buffer-tank) now exist in machines.json; they place and draw power but do nothing. Not in my orders — flagging so nobody thinks they work.
• heat is always 0, bandwidth.stored always 0 (M2 / buffer tanks).
• Port 8150 is held by another session's dev server, and the harness won't start a second one for this project. I verified against that server read-only. Note for whoever plays the build in a Browser pane: the tab reports visibilityState: hidden, so rAF is paused and the sim crawls (~9 ticks per screenshot). That's the pane, not the loop — importing the sim module directly in the page runs it at ~96k ticks/sec.

CONTRACT REQUEST

• None. contracts.ts covered everything I needed this round.

PROPOSAL (yours to call, not mine to take)

1. Splitters next. lane-splitter with round-robin plus a priority/overflow output is the canonical Factorio answer to the deadlock above, and it unlocks byproduct sinks and the bloom-loop topology later. This is the one I'd pick.
2. Alternative, ~5 lines: allow a lower-ranked belt when every preferred belt is full and outputBuf has hit the stall threshold. Cheap, but it makes byproduct management automatic and quietly deletes a core Factorio tension — a gameplay decision, so I left it alone.
3. jammed: 'starved' for idle-with-no-input would let the inspector tell "backed up" from "waiting". Cheap, but it's UI-visible, so it's LANE-UI's business as much as mine.
4. Extractors should require a seam tile — needs a seam/ore map from DATA and a worldgen call.

NEXT (round 2 if asked)

• lane-splitter with priority/overflow; buffer-tank feeding bandwidth.stored to smooth brownouts.
• Heat: accumulate per craft, throttle >0.7, scram at 1 (the software decoder's whole bit).
• Save/load — SimSnapshot is already the right shape to serialize.
• A worked, deadlock-free reference factory you can paste into the console to demo M1.

Round 2 — 2026-07-17 — Opus 4.8

SHIPPED

• Reference factory (src/sim/reference.ts, referenceFactory(data)): 114 commands, 110 entities. Ships its first MELT at tick 1247 and is still shipping at 20,000 — 6–15 melt per 2,000-tick window, flat, no decay. Round 1's build wedged at ~1200; this one never does, and the demuxer's jammed stays null the whole way. Surplus becomes product instead of a deadlock: 1,136 macroblock bricks + 1,997 hf dust shipped, 219 slurry voided over 20k ticks.
• Splitters — round-robin, blocked outputs skipped, rank traced through them (a lane's rank is now the best outcome reachable across every terminal it can reach).
• Buffer tanks — charge on surplus, discharge to cover a deficit, brownout only once dry; bandwidth.stored is the pool.
• Heat v1 — heatPerTick while active + RecipeDef.heat per craft, ambient cooling, throttle above 0.7, scram at 1.0, restart under 0.5, both edges emitting scram.
• Commission queue — data-order activation, commissionDone advances, repeat re-enters at the back, progress still only counts while active.
• jammed:'starved' and BeltItem.id (always set; survives belt transfers and splitters, so the renderer never sees an item teleport).
• Verified: 37 sim tests green (18 + 15 M2 mechanics + 4 reference), tsc clean in src/sim. In the live app I dispatched the whole reference factory through __fktryBus — it builds, renders, and runs, and my round-2 work is already visibly driving other lanes: the UI reads 94 DRAW / 220 GEN + BUFFER off bandwidth v2, the fax shows the queue ("NEXT IN TRAY: DUST ALLOWANCE"), and LANE-UI's OSHA voice is narrating my new flag ("DCT PRESS: INTAKE STARVED. NOTHING IS ARRIVING.").
• Determinism holds across engines: browser and Node both give tick 1247 and identical per-window melt counts.
• Perf: 3,500 entities + 6,820 belt items → 0.465 ms/tick (72× realtime). Round 1 was 0.418 (80×); the ~11% is heat touching every entity every tick. Still well inside target.

DECISIONS

• Heat curve (mine to pick, per orders). Throttle is linear from 1.0 at heat 0.7 down to 0.5 at heat 1.0 — so the lore's "tick rate visibly halves" lands exactly at the scram point. Ambient cooling is a flat 0.004/tick applied always, working or not (1.0 → cold in 250 ticks ≈ 8s), which means any machine with heatPerTick below 0.004 can never overheat. Scram at 1.0, restart under 0.5, so a hot generator duty-cycles rather than dying.
• Throttle applies to powerGen, not just craft speed. A hot decoder's output sags before it drops off the bus entirely — which is precisely the hole buffer tanks exist to fill. That synergy is my reading of "per-machine throttle"; say the word if generators should be exempt.
• Scrammed machines keep their idle powerDraw (stopped, not unplugged) and freeze mid-craft progress, resuming on restart rather than binning the work.
• Scram clears jammed and suppresses jam evaluation: a scrammed machine reports through heat + the scram event, not as a flow jam. Two channels, no double-reporting.
• Splitters hold 2 items, mirrored into inputBuf so the inspector can see them. Any adjacent belt not pointing in is an output; the splitter's own dir is unused. Machines can't push straight into one — feed it with a belt.
• starved fires whenever a recipe sits idle without enough input — including a machine that simply outruns its feed. LANE-UI: expect it to flicker on a fast machine with a slow supply. That's accurate rather than a bug, but you may want to debounce the voice line.
• The reference factory validates every machine/recipe id against data and throws a named error, so DATA drift fails loudly instead of resurfacing as a mystery deadlock.

BLOCKED/BROKEN

• DATA carries none of the v2 fields, so heat and buffer tanks are inert in the real game. No machine has heatPerTick, none has bufferCap, no recipe has heat, no commission has repeat. Both systems are fully implemented and tested — on a fixture I own (pressure.test.ts), because there is nothing in data/ to test them against. The DoD's "heat throttles and scrams the software decoder" is proven mechanically, but the actual SOFTWARE DECODER cannot overheat until DATA gives it a number. This is the one thing standing between M2 heat and being real.
  • Starting values if they help (my suggestion, DATA's call): software-decoder heatPerTick: 0.005 → ~33s of work then a ~4s scram, an ~89% duty cycle that reads as theatrical rather than punishing; decode-asic left at 0 (cool and inflexible, per the codex); buffer-tank bufferCap: 600 ≈ 20s of cover against a 30-bandwidth deficit — enough to ride out exactly one decoder scram, which is a nice thing to discover.
• src/sim/data-validate.test.ts is LANE-DATA's file living inside my owned path. I have not touched it. Worth an ownership ruling — either it moves to data/, or my lane doc should say I share the folder.

CONTRACT REQUEST

• MachineDef.coolPerTick?: number (default 0.004). Right now cooling is a global constant, so DATA can tune how fast a machine heats but not how fast it recovers — every machine cools 1.0 → 0.5 in exactly 125 ticks. The codex explicitly has ASIC coolers venting heat, which wants a per-machine number. Cheap to add, and I'd wire it the round it lands.

PROPOSAL

• BeltItem.id can drop the ? in v3 whenever you like — I always set it already.
• referenceFactory's setRecipe commands depend on entity ids being handed out in placement order (1..N). That's true and deterministic, but it's an implicit coupling to my id allocation. A setRecipeAt(pos) command variant would remove it. Not urgent, just a tripwire worth knowing about before someone edits the layout.
• Splitters have no filter or priority, and the reference factory proves you don't need either — skip-blocked self-balances. Worth revisiting only when bloom loops want a filtered tap.

NEXT (round 3 if asked)

• Save/load — SimSnapshot is already the right shape.
• Bloom loops: my trace already treats a closed belt circle as "no terminal" → rank 0 → accept and pile, which is exactly what a loop wants. The P-frame duplicator should drop straight in.
• HF dust piles + mosquito swarms (the rest of M2 PRESSURE) — the seeded RNG is sitting there unused and waiting for its first roll.
• Heat, for real, the moment DATA has numbers.