Ingot molds empty themselves (no F); removing a mold returns its set metal

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

docs/DESIGN.md

@@ -78,9 +78,10 @@ Details and numbers live in the code and in `docs/systems/`.
     pipes, pumps, outlets.
   - Machines: fan, Refiner, Stone cutter, Silo.
   - Molds: ingot, bit, tank. Ingot bars drop out of the bottom onto whatever is under the mold;
-    leave one open block below and a belt under that carries them off. F is optional upkeep: it
-    cleans the trough, chips off slag and rakes the furnace grate. Short stubs stay for the next
-    firing.
+    leave one open block below and a belt under that carries them off. Ingot molds empty themselves:
+    junk and mixed scrap drop below, slag is thrown away and the grate above is raked. Short stubs
+    stay for the next firing. Removing any mold returns its set metal to the bag: whole bars as
+    bars, the rest as scrap.
   - Build actions: drag for lines, Shift-drag for rectangles, hold G to replace, hold C / X and
     drag to copy / cut, V to paste, Ctrl+Z to undo, middle mouse to pick,
     Shift+Q/E to switch build tabs.
@@ -137,7 +138,7 @@ above, including:
 **2026-10-23:**
 - **Ingot molds drop bars below automatically.** The owner reported bars being thrown into the
   furnace above and wants belts underneath to carry them off. Blocked bars wait in the trough;
-  short stubs stay for the next firing. F stays available for cleaning and raking.
+  short stubs stay for the next firing. The mold cleans itself and rakes the grate after dropping bars or clearing junk.
 - **Screw tubes carry no more than belts:** they move every other tick. For more throughput,
   build more lines.
 - **A heap on a belt moves as one**, up to 96 grains deep, not just its bottom layer. If a grain is blocked,
@@ -172,6 +173,8 @@ above, including:
 - **The build tool has a compact top-left card** like the other tools. The owner asked for it
   back after it was hidden; the long description stays in the hover popup.
 
+- **Ingot molds need no F.** They push junk and mixed metal out of the bottom as loose grains with the bars, throw slag away and rake the grate. Removing any mold returns its set metal: whole bars as bars, the rest as scrap. The owner asked what F was for once bars dropped on their own, and chose this over keeping F for cleaning.
+
 ## Ideas not built yet
 
 - **Concrete**, as a stronger wall material from rubble.

docs/PROJECT_MAP.md

@@ -257,8 +257,8 @@ How belts, filters and screw tubes move what is on or in them. What rests on a b
 Building blocks: placing, integrity, removing, lines and rectangles of blocks.
 - functions: blockOf, blockCellList, pieceCost, canPlaceBlock, placeBlock, blockIntegrity, removeBlock, blockLine, blockRect, blockInReach, blockIs, placeBlocks
 
-### src/sim/molds.js (298 lines)
-Molds: cavities for castings; ingot troughs drop bars out of the bottom.
+### src/sim/molds.js (328 lines)
+Molds: cavities for castings; ingot troughs empty themselves below. Removal returns set metal.
 - functions: moldCellsAt, canPlaceMold, newMoldRecord, addMold, castMix, cavityState, troughState, clearCavity, moldPlugCells, rakeAbove, furnaceJunkHint, unplugMold, ejectIngot, checkMolds, moldAt, knockNote, tally, collectMold, removeMold
 - variables: DROSS, grains, barWord
 

docs/agent-log.md

@@ -4,6 +4,26 @@ 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: ingot molds need no F; removing a mold returns its metal (Claude Code, with Codex)
+
+Note: "now that the ingot molds drop the ingots, what is the purpose of F…". The owner chose no F
+on ingot molds.
+
+- `src/sim/molds.js` `ejectIngot`: when nothing over or in the mold is molten, junk and mixed
+  metal (as scrap) and plugs over the trough or frozen in the grate are written as loose grains
+  into the 4 rows under the mold; what doesn't fit waits. Slag and ash are thrown away. After a
+  drop or a clean-out the grate above is raked. Bars and the short stub work as before.
+- `collectMold` on an ingot mold only says "Ingot molds empty themselves." Bit and tank molds
+  keep F. `removeMold` (every kind) gives the set metal to the bag: whole bars as bars, the rest
+  as scrap; molten metal is left alone.
+- Text: `troughState` flaws, `info.js`, `overlays.js` (no "· F" on ingots), `pieces.js`,
+  `progress.js`, `notebook.js`, `docs/systems/stone-and-liquids.md`, `docs/DESIGN.md`.
+- Tests: `t_molds` 60 checks (F does nothing on ingots; plate, slag and rake cases now
+  automatic; junk out, mixed metal out as scrap, junk waits when blocked and while molten;
+  removal returns bars and scrap, leaves molten metal). `furnace_play.js` adapted. All 11
+  headless suites and `play.py` (122) pass.
+- Open: undoing a mold removal brings the mold back empty (its metal stays in the bag).
+
 ## 2026-10-23: compact build card top-left (Claude Code, with Codex)
 
 Note: "build tool has no info box like the other tools." The owner chose a compact card.

docs/systems/stone-and-liquids.md

@@ -71,6 +71,9 @@ through another refiner.
 - **Glass bricks.**
   - Sand melts to molten glass in a fan furnace (peak about 2000°C measured).
   - Cast in an Ingot mold, it drops out of the bottom as glass bricks, worth $14 each.
+  - Ingot molds empty themselves: bars, junk and mixed scrap drop below; slag is thrown away
+    and the grate above is raked. Removing any mold returns its set metal to the bag: whole
+    bars as bars, the rest as scrap.
   - Glass bricks build glass wall blocks. Glass is too brittle for a bit mold.
 - **Stone cutter** (machine, 2×2, $90).
   - A saw under a hopper. Every 8 grains of stone rubble become one stone brick, which drops out