Screw tubes use all their lanes: grains spread sideways inside a tube

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

docs/DESIGN.md

@@ -188,6 +188,12 @@ above, including:
 - **The silo has pixel art in the pixel look**, drawn grain by grain like the rest of the world;
   the smooth look keeps the illustrated silo. The owner noticed it looked the same in both.
 
+- **Screw tubes use all their lanes.** Grains in an up or down tube shift sideways toward the
+  emptier lanes of the block, and grains taken in from the side go to the far lanes first. A
+  block-wide lift fed by a belt from the side now carries about 90% of what the belt brings
+  (before, only the edge lane filled: the owner saw one line on either side). Belts keep their
+  speed.
+
 ## Ideas not built yet
 
 - **Concrete**, as a stronger wall material from rubble.

docs/PROJECT_MAP.md

@@ -244,13 +244,13 @@ Pipes, pumps and outlets: each joined line holds one liquid as a count, not as g
 - functions: sideOf, pipeClosedSide, pipeJoins, rebuildPipes, pipeNetOf, pipeTakeShare, faceCell, pumpDraw, outletPour, pipesTick
 - variables: PIPE_CAP, PUMP_RATE, OUTLET_RATE, PUMP_MAX_T, SIDE_V, PUMP_V, OUTLET_V, pipeNets, pipeNetAt, pipesDirty
 
-### src/sim/machine-tick.js (158 lines)
+### src/sim/machine-tick.js (166 lines)
 Per-tick machine work: steam engines, fans, belts, filters, screw tubes (machinesTick).
 - functions: engineIntake, fanBlow, machinesTick
 
-### src/sim/conveyors.js (114 lines)
+### src/sim/conveyors.js (127 lines)
 How belts, filters and screw tubes move what is on or in them. What rests on a belt or filter rides along: the whole stack standing on the carrying surface steps one cell toward d together (belts run front of the line first, so the way ahead is clear). If a powder grain is blocked, the load above it stands still and the belt slips underneath. A filter's own material drops through it instead, unless it is already full.
-- functions: carryColumn, beltDrain, launchGrain, rebuildFilters, filterCarry, setFilter, filterRun, roomFor, tubeIntake
+- functions: carryColumn, beltDrain, launchGrain, rebuildFilters, filterCarry, setFilter, filterRun, roomFor, tubeSpread, tubeIntake
 - variables: CARRY_DEPTH, filterR, filterL, filtersDirty
 
 ### src/sim/blocks.js (132 lines)

docs/agent-log.md

@@ -4,6 +4,27 @@ What agents have done, newest first. Add an entry for every piece of work: the d
 note or request it was for, what changed, the files touched, the tests run, and anything left
 open or not verified. Keep each entry short; the git history has the details.
 
+## 2026-10-23: screw tubes use all their lanes (Claude Code, with Codex)
+
+Note: "maybe the belts can move faster/carry more than the tubes… the tubes only carry one line of
+materials on either side." The owner chose to fill every lane; belt speed is unchanged.
+
+- Measured first (`test/t_conveyors.js`, a belt with a sand heap into the side of a 6-block up
+  tube, 3,000 ticks): 1,459 grains out, lanes `[2940, 0, 0, 10]`; the edge lane was full (one
+  lane carries at most ~1,500). Spreading only at intake changed little (1,486): belts push
+  straight into the edge lane without going through `tubeIntake`.
+- `src/sim/machine-tick.js`: on each tube beat a grain in a vertical tube may step sideways
+  within its block to a lane with clearly fewer grains ahead (a strict gap stops shuffling).
+  `src/sim/conveyors.js`: `tubeSpread`, shared by side intake (far lanes first) and corners.
+- After: 2,071 out (92% of the 2,243 the same belt delivers to an open drop), lanes
+  `[1937, 1116, 486, 872]`, sand conserved. Checks: all four lanes, conservation, at least 90%
+  of the belt's delivery, a side-fed sideways tube fills more than one row. All 11 headless
+  suites and `play.py` pass. `docs/DESIGN.md`, `docs/PROJECT_MAP.md`.
+- Found on the way: Codex's sandbox (`workspace-write`) blocks network sockets, and headless
+  Chrome crashes at startup without one (SIGTRAP core dumps in pairs). Codex runs now pass
+  `-c sandbox_workspace_write.network_access=true`.
+- Open: nothing.
+
 ## 2026-10-23: the build card describes the build tool, not the piece (Claude Code)
 
 Note: "instead of the current info box for the build tool showing the current building selected,