Resting faces steeper than the angle of repose topple: blown sand towers collapse (t93)

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

docs/DESIGN.md

@@ -570,6 +570,21 @@ above, including:
   Resting heaps do not enter this path; world generation keeps its recorded settling rules
   and seed layouts.
 
+- **Nozzle-built sand towers topple from rest (t93 round 3, 2026-10-28).** The owner
+  reproduced vertical sand towers by continuously blowing straight up. Landing places grains
+  at or above impact; supported face grains need to release before the outer falling column
+  clears. A tall body now spills from a supported exposed face as well as a falling one.
+  Apply this to free-flowing powders (STICK=1); cohesive grains retain their stickier release
+  and do not inherit the outward motion. Require an open side and a steep drop, backed eight grains inward by a continuous column
+  at least 32 grains high (look at most 24 rows each way). This leaves short feeds and the
+  deliberately steeper small clay heaps on their existing settling rules. The spill is still
+  bounded to eight grains horizontally and vertically, checking every crossed cell.
+  Two cell flag bits retain the collapse direction while the released grain falls: up to two
+  grains outward and eight down per tick. Removing support passes that direction to the grain
+  immediately above, so the falling layer drains promptly. Contact below cancels this motion;
+  ordinary repose rules take over. Keep stamped moves, barriers, burning-bed protection and
+  worker independence. The existing worldgen POWDER_FAN switch disables new face releases.
+
 ## Ideas not built yet
 
 - **Concrete**, as a stronger wall material from rubble.

docs/PROJECT_MAP.md

@@ -225,9 +225,9 @@ Material definitions: ids, properties and metal families. ids, and drill/tank ti
 - functions: def, metalFamily
 - variables: EMPTY, GRASS, DIRT, LDIRT, SAND, GRAVEL, CLAY, STONE, GRANITE, BASALT, NMAT, MD, FIRETO
 
-### src/sim/material-tables.js (54 lines)
+### src/sim/material-tables.js (55 lines)
 Material tables: typed properties, casting groups, flags, parts and tool tiers. Typed property tables
-- variables: PH, DENS, KC, ICAP, CASTMETAL, METAL_TIER, SOLIDMETAL, F_NAT, F_CAST, F_BURN, P_NONE, P_SCREW_U, P_SCREW_D, P_SCREW_L, P_SCREW_R, P_GRATE, P_GOPEN, P_WHEEL, P_INTAKE, P_FILTER, P_PIPE, P_SCREW_UR, P_SCREW_DR, P_SCREW_DL, P_SCREW_UL, SCREW_PARTS, SCREW_DIRS, IS_SCREW, SCREW_DX, SCREW_DY, BIT_TIERS, TANK_TIERS, REACH
+- variables: PH, DENS, KC, ICAP, CASTMETAL, METAL_TIER, SOLIDMETAL, F_NAT, F_CAST, F_BURN, F_AVALANCHE, F_AVALANCHE_R, P_NONE, P_SCREW_U, P_SCREW_D, P_SCREW_L, P_SCREW_R, P_GRATE, P_GOPEN, P_WHEEL, P_INTAKE, P_FILTER, P_PIPE, P_SCREW_UR, P_SCREW_DR, P_SCREW_DL, P_SCREW_UL, SCREW_PARTS, SCREW_DIRS, IS_SCREW, SCREW_DX, SCREW_DY, BIT_TIERS, TANK_TIERS, REACH
 
 ### src/sim/pieces.js (179 lines)
 Everything the player can build (PIECES): blocks, machines and molds, with costs and descriptions; filter settings; wall materials and their cost.
@@ -254,9 +254,9 @@ Exploration only: never changes grains or the random stream.
 - functions: fogAlloc, fogMark, fogSeen, fogInit, fogLook, fogRevealAround, fogRevealAll
 - variables: FOG, FOG_SENSE, FOG_SENSE_FADE, fog, FW, FH
 
-### src/sim/cells.js (272 lines)
+### src/sim/cells.js (321 lines)
 Cell helpers (setCell, move, enter) and the falling-sand movement of powders, liquids and gases (simMove).
-- functions: setCell, swapCells, swapCellData, move, enter, enterFree, powder, passable, liquid, liquidSearch, gas, wakeBotPowder, simMove, moveChunk
+- functions: setCell, swapCells, swapCellData, move, enter, enterFree, powderSpill, avalancheMove, powder, passable, liquid, liquidSearch, gas, wakeBotPowder, simMove, moveChunk
 - variables: SORTP, SORTP_FUEL, LSTEP, LFILM, CORNER_SEAL, POWDER_FAN
 
 ### src/sim/heat.js (266 lines)
@@ -630,11 +630,14 @@ The frame loop and boot.
 - `test/harness.js`: Loads the simulation (the src/sim/ files listed in src/manifest.json, joined in order into one script, the same way build.py joins them) so scenarios can drive it headlessly in Node. Errors point at the real file and line (sim/pipes.js:42), not at the joined script.
 - `test/light-cases.js`: Lighting behaviour checks executed by the GPU browser harness.
 - `test/light-readback.js`: Read float source channels, including transmittance, from the WGSL light pass.
+- `test/pile-blow.js`: Shared reproduction: continuously blow plain bagged sand straight above a stationary bot.
 - `test/pile-cut.js`: Shared Node/browser reproduction: vacuum the foot of settled 60-grain heaps, one stroke per tick.
 - `test/play.py`: Play-test in a real browser: mouse, keyboard and a mocked gamepad drive the game; save and continue. Screenshots go to shots/play/ (or the folder given as the first argument). Pixel look unless the second argument is 'smooth'.
 - `test/run_all.py`: Run the test suites and report.
 - `test/t_bar_stacking.js`: Resting bars snap into pairs of grains and tip off narrow supports.
 - `test/t_basics.js`: Basics: drilling to rubble, the vacuum and blowing, walls, the ingot mold and bars, belts, blueprints, save/load.
+- `test/t_blow_collapse.js`: Owner's upward nozzle recipe, inline and with real shared-memory helpers.
+- `test/t_blow_collapse.py`: Straight-up bagged sand nozzle in the real pixel frame loop.
 - `test/t_build.js`: Building: undo (Ctrl+Z), cut, replace a machine with Ctrl, pasting ghosts, and the fan heat warning.
 - `test/t_caps.py`: Capability detection, title notices and the required-WebGPU startup gate.
 - `test/t_conveyors.js`: Screw conveyors that never carry liquid (it flows through), screw and belt throughput, filters.

docs/TESTING.md

@@ -86,6 +86,13 @@ checks waking within eight ticks separately from the probabilistic consumption o
   bot-near/far, grain conservation, equal material bytes and forced-awake resting stability.
   It also checks a broad 120-grain wall within 600 ticks and a spill stopped by cleats
   across chunk edges, where the source chunk's one-grain barrier flag is clear.
+- `test/t_blow_collapse.py` continuously blows bagged sand straight above a stationary bot
+  at nozzle radius 6 for 1200 real frame-loop ticks, then checks the pile after 480 idle
+  ticks with actual helper dispatch. Pixel captures are `shots/t93c-before.png` and
+  `shots/t93c-after.png`. `test/t_blow_collapse.js` repeats the recipe inline and with
+  1/2/8 Node helpers, compares material and motion flags, conserves all bag/flying/landed
+  sand, and forces visits to check resting stability. It also directly checks a supported
+  face releasing immediately and a spill stopped by a cleat across a chunk boundary.
 - `test/t_smooth.py` checks WebGPU smooth shapes, seams, joins, fog and the thermal lens.
 - `test/t_gpu_golden.py` compares 28 cropped frozen reference PNGs (384x288, under
   `test/fixtures/golden/`) against WebGPU: renderer, joins, sky and four light scenes,

docs/agent-log.md

@@ -6,6 +6,51 @@ open or not verified. Keep each entry short; the git history has the details.
 
 
 
+
+## 2026-10-28: t93 round 3, nozzle-built resting sand faces (Codex)
+
+- Reproduced the owner's continuous straight-up radius-6 sand nozzle recipe, not a
+  vacuum cut: 1200 toolBlow ticks under open sky. Matching original-code Node and real
+  pixel frame-loop browser controls fail the new regression. Browser, NVIDIA RTX 5070,
+  two active helpers: 79-grain cliff at blow end, still 61 after 480 idle ticks. Active
+  chunks remain; neither sticky rolls (sand already has STICK=1) nor missing wakes explain it.
+- Cause: landFlyer/depositNear stack grains at or above impact, while supported exposed
+  grains only slide a single diagonal cell. The earlier fan rule requires empty space below
+  and misses the resting face. Simply extending the initial spill leaves the falling layer
+  blocking further release. Tall bodies now release from rest and carry a bounded outward
+  fall through the newly unsupported column; contact below cancels that motion. Cohesive
+  grains retain their existing release and do not inherit it. A continuous 32-grain backing
+  column eight grains inward distinguishes towers from short feeds. Read reach <=24,
+  write reach <=8, no per-grain allocation, existing worldgen switch retained.
+- New shared nozzle fixture and headless/browser regressions cover the actual tool, direct
+  supported-face release, cross-chunk cleats, conservation, 0/1/2/8 helpers, exact material
+  and motion-flag bytes, and forced-awake stability. Larger equal-mass clay/sand check:
+  7200 grains, final heights 90/75. Rejected broad release and persistent motion on contact
+  experiments after they changed small heaps, clay or transport checks; no old test weakened.
+- Final headless suite passes. Served pixel browser nozzle check passes at exactly 480 idle
+  ticks: cliff 32 -> 1, all 40000 grains retained in bag/flight/pile, final pile sleeps.
+  Saved and inspected shots/t93c-before.png and shots/t93c-after.png; matching old-rule
+  captures are shots/t93c-control-{before,after}.png. Final full
+  python3 test/run_all.py --browser: ALL PASSED, 35 headless and 10 browser suites,
+  including nozzle 25, collapse 17, vacuum 44, threads 12, gameplay 361, both browser
+  collapse regressions, original worldgen hashes and liquids. Log: /tmp/t93c-all-browser.log.
+  Ticked round-3 feedback with a report and moved t93 to Review. Owner playtesting
+  remains open. No commit.
+- Isolated real-GPU requested profile, no concurrent tests: original-code control -> final
+  total ms/tick: settled 1.9359 -> 1.9413 (+0.3%), heat 2.6679 -> 2.7080 (+1.5%).
+  Versus historical tools/perf-after-t88.json: +7.5%/+3.2%; the control already measures
+  +7.2%/+1.7%. Awake counts match (425/494). Movement ms/tick 0.9520 -> 0.9570 and
+  1.3460 -> 1.3850; unchanged heat work 0.9060 -> 0.9067 and 1.2425 -> 1.2424.
+  Logs/JSON: /tmp/t93c-perf-{control,final}.{log,json}. Some real-loop frame-tail timings
+  are noisier and exceed the profiler's 10% marker; the requested isolated simulation
+  tick averages are within a few percent of the matching control.
+- Files: src/sim/cells.js, src/sim/material-tables.js, test/pile-blow.js,
+  test/t_blow_collapse.{js,py}, test/run_all.py, docs/DESIGN.md, docs/TESTING.md,
+  regenerated docs/PROJECT_MAP.md, t93 task and this log. Further evidence:
+  /tmp/t93c-red.log, /tmp/t93c-browser-red.log, /tmp/t93c-browser-final.log,
+  /tmp/t93c-final-headless2.log.
+
+
 ## 2026-10-28: t93 reopened, vacuum-cut faces drain in columns (Codex)
 
 - Read AGENTS, the t93 task/log and 807217b; inspected both new owner screenshots.