New-world lakes start level; no trees in water (t96)

docs/DESIGN.md

@@ -590,6 +590,13 @@ above, including:
   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.
 
+- **New-world lakes wake immediately; keep the seed layout (t96, 2026-10-29).** Keep the
+  recorded worldgen settling speeds and material/temperature output. Wake water after the
+  final startup reset so unfinished lakes level without drilling. Retain tree candidates and
+  their random draws, then omit whole trees whose bases are wet or on an open bank connected
+  to water at base height after settling. This keeps trees out of the lake as it spreads.
+  Existing load wake scheduling and later snowmelt/flooding rules stay as they are.
+
 ## Ideas not built yet
 
 - **Concrete**, as a stronger wall material from rubble.

docs/PROJECT_MAP.md

@@ -383,7 +383,7 @@ World generation helpers: noise and removal of tiny hard rock specks.
 - functions: makeNoise, fbm, clearHardSpecks
 - variables: SPECK_MIN
 
-### src/sim/worldgen.js (286 lines)
+### src/sim/worldgen.js (303 lines)
 World generation: staged terrain, ore, caves and placement, with synchronous and async entry points.
 - functions: generateWorld, generateWorldAsync
 
@@ -656,6 +656,7 @@ The frame loop and boot.
 - `test/t_gpu_golden.py`: Frozen world references; seven smooth crops corrected for continuous noise in t91.
 - `test/t_gpu_light.py`: The former CPU light behavioural checks, now read from the actual GPU light grid.
 - `test/t_joins.js`: The oracle states the geometric rule independently of the precomputed neighbour tables.
+- `test/t_lakes.js`: Generated lakes wake without a tool, settle on their own, and have dry tree bases.
 - `test/t_load.js`: Reload wakes nearby areas first, without losing distant water, fire or saved state.
 - `test/t_molds.js`: Molds and furnaces stay usable: ingots drop below and keep their stubs, plugs over molds are cleared, spoiled castings can be knocked out, grains never drop through a grate by teleporting, and slag lets the fire breathe.
 - `test/t_nozzle.js`: Blowing aims within the nozzle's reach, with room for the brush and settling.

docs/TESTING.md

@@ -69,6 +69,11 @@ seeded sand pile bounds in `t_corner_seal.js`; the heat oracle now supports pass
 The conveyor fixture uses a wider feed pile, the screen fixture warms longer, and `t_load.js`
 checks waking within eight ticks separately from the probabilistic consumption of fuel.
 
+`test/t_lakes.js` pins SHA-256 over raw `mat` followed by Float32 `temp` bytes for seeds
+7, 42 and 424242 at 2048x1024. These hashes predate t96 and must not be re-baselined for a
+wake/background-tree change. It also checks generated tree bases, startup wakes, and the
+seed-7 lake leveling within two grains after 6,000 undisturbed ticks, fresh and reloaded.
+
 ## Browser tests
 
 - They need the `.venv` from README.md → Develop; plain `python3` switches to it on its own.

docs/agent-log.md

@@ -4,6 +4,18 @@ 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.
 
+## 2026-10-29: t96 wake new-world lakes and keep trees off their banks (Codex)
+
+- Wake water after startup reset; omit whole tree candidates on wet/water-connected low banks.
+  Original mat+temp hashes match for seeds 7/42/424242; pinned settling, physics and save format unchanged.
+- Files: src/sim/worldgen.js, test/t_lakes.js, docs/{DESIGN,TESTING,PROJECT_MAP}.md, tasks/t96* and this log.
+- Tests failed first; all 38 headless suites pass (23 lake checks; /tmp/t96-headless.log).
+  Only browser test: /tmp/playwright-test-t96.py (fresh/reloaded seed 7, pixel, two helpers, no page errors;
+  /tmp/t96-browser-final.log). Inspected shots/t96-{fresh,fresh-settled,reloaded-settled}.png.
+  Sandbox graphics startup stalled; outside-sandbox run passed. No full browser suite.
+- Lake moves on tick 1; levels within two grains by 6,000 ticks (100 seconds). Later snowmelt
+  can flood other trees; that behavior is unchanged. Owner playtest pending. No commit.
+
 ## 2026-10-29: t95 separate nozzle and rain flight allowances (Codex)
 
 - Nozzle counts bag flyers only, up to 4,000, with “Too much in the air.” feedback;

src/sim/worldgen.js

@@ -190,12 +190,14 @@ function* worldSteps(seedIn, w, h) {
   }
   yield [0.72, 'Snow and trees'];
   // trees
+  const trees = [];
   for (let x = 12; x < w - 12;) {
     const sy = surfY[x];
     const ok = mat[sy * w + x] === GRASS && mat[sy * w + x + 1] === GRASS && !noTree[x] && Math.abs(x - spawnX) > 6 && !(x > spawnX + 14 && x < spawnX + 72); // none where the dock goes
     if (ok && rng() < 0.7) {
+      const tree = { x, y: sy - 1, cells: [] }; trees.push(tree);
       const th = 9 + Math.floor(rng() * 8);
-      const setW = (xx, yy) => { if (xx < 0 || yy < 1 || xx >= w) return; const i = yy * w + xx; if (mat[i] === EMPTY) bgm[i] = WOOD; };
+      const setW = (xx, yy) => { if (xx < 0 || yy < 1 || xx >= w) return; const i = yy * w + xx; if (mat[i] === EMPTY) { bgm[i] = WOOD; tree.cells.push(i, WOOD); } };
       for (let k = 1; k <= th; k++) for (let dx = 0; dx < 2; dx++) setW(x + dx, sy - k);
       // two branches
       for (const side of [-1, 1]) { const by = sy - th + 3 + Math.floor(rng() * 3); for (let k = 1; k <= 3; k++) setW(x + (side < 0 ? -k : 1 + k), by - (k >> 1)); }
@@ -206,7 +208,7 @@ function* worldSteps(seedIn, w, h) {
         for (let yy = Math.floor(cy - r); yy <= cy + r; yy++) for (let xx = Math.floor(cx - r); xx <= cx + r; xx++) {
           if (xx < 0 || yy < 1 || xx >= w) continue;
           const ex = (xx - cx) / r, ey = (yy - cy) / (r * 0.85);
-          if (ex * ex + ey * ey <= 1 && hash2(xx, yy, worldSeed + 7) % 9 !== 0) { const i = yy * w + xx; if (mat[i] === EMPTY && !bgm[i]) bgm[i] = LEAVES; }
+          if (ex * ex + ey * ey <= 1 && hash2(xx, yy, worldSeed + 7) % 9 !== 0) { const i = yy * w + xx; if (mat[i] === EMPTY && !bgm[i]) { bgm[i] = LEAVES; tree.cells.push(i, LEAVES); } }
         }
       }
       x += 16 + Math.floor(rng() * 20);
@@ -258,9 +260,24 @@ function* worldSteps(seedIn, w, h) {
   // re-ambient after settling, then start clean
   for (let i = 0; i < N; i++) { const m = mat[i]; if (m !== MAGMA) temp[i] = AMB[(i / w) | 0]; life[i] = PH[m] === PH_LIQUID && FRZ[m] ? 255 : 0; }
   tick = 0;
+  // Settling can carry lakes past noTree; leave their connected low banks treeless too.
+  bgm.fill(0);
+  for (const tree of trees) {
+    let wet = false;
+    for (let root = tree.x; root <= tree.x + 1 && !wet; root++) for (const d of [-1, 1]) {
+      for (let x = root; x >= 0 && x < w; x += d) {
+        const m = mat[tree.y * w + x];
+        if (m === WATER) { wet = true; break; }
+        if (m !== EMPTY && PH[m] !== PH_GAS) break;
+      }
+    }
+    if (!wet) for (let k = 0; k < tree.cells.length; k += 2) bgm[tree.cells[k]] = tree.cells[k + 1];
+  }
   findTreeBases();
   placeDock(spawnX + 34);
   hot.fill(0); awake.fill(0); updateRoof();
+  // Keep the generated grains intact, but let unfinished lakes level from the first tick.
+  for (let i = 0; i < N; i++) if (mat[i] === WATER) wakeIdx(i);
   resetEconomy(); resetWeather();
   weather.base = worldWater();
   bot.x = spawnX - 2; bot.y = surfY[spawnX] - 14; bot.vx = 0; bot.vy = 0;

test/t_lakes.js

@@ -0,0 +1,51 @@
+// Generated lakes wake without a tool, settle on their own, and have dry tree bases.
+const { load, suite, ticks } = require('./harness');
+const { createHash } = require('node:crypto');
+const { run } = load();
+const { check, done } = suite();
+const water = run('WATER');
+function surfacePools() {
+  return run(`(() => {
+    const pools = []; let pool = null;
+    for (let x = 0; x < W; x++) {
+      let y = 0; while (y < H && mat[y * W + x] === EMPTY) y++;
+      if (mat[y * W + x] !== WATER) { pool = null; continue; }
+      if (!pool) { pool = { x0: x, x1: x, width: 0, min: y, max: y }; pools.push(pool); }
+      pool.x1 = x; pool.width++; pool.min = Math.min(pool.min, y); pool.max = Math.max(pool.max, y);
+    }
+    return pools.filter(p => p.width > 20);
+  })()`);
+}
+for (const [seed, expected] of [
+  [7, '865ac320f743ff5ed573acab3333773b5ebc2e10f15600438dd15f1767acb72e'],
+  [42, '94930e108f7bd948c6f3dbe8b15b2950eed695cb3d57376d05a8ad781c2015b7'],
+  [424242, '8b8a4b44c2cc98d3ab86515eb55f38ce7cb3d6a283e29e0ed758af937ea8e8c8'],
+]) {
+  run(`generateWorld(${seed}, 2048, 1024); weather.next = 1e15;`);
+  const hash = createHash('sha256');
+  for (const name of ['mat', 'temp']) hash.update(Buffer.from(run(name).buffer));
+  check(`seed ${seed} preserves generated material and temperature bytes`, hash.digest('hex') === expected);
+  check(`seed ${seed} restores pinned generation switches`, run('LSTEP === 8 && LFILM === 4 && SORTP === 0.06 && CORNER_SEAL && POWDER_FAN'));
+  check(`seed ${seed} starts every water area awake`, run(`mat.every((m, i) => m !== WATER || awake[((i / W) >> 5) * CW + ((i % W) >> 5)] > 0)`));
+  check(`seed ${seed} has no submerged tree base`, run('treeBases.every(i => !treeHeld(i) || mat[i] !== WATER)'));
+  check(`seed ${seed} retains dry trees`, run('treeBases.filter(i => treeHeld(i)).length > 20'));
+  // Seed 7 reproduces the owner's long slope. No drill, forced wakes, or terrain edits.
+  if (seed === 7) {
+    run('globalThis.lakeSave = serializeWorld();');
+    for (const state of ['fresh', 'reloaded']) {
+      if (state === 'reloaded') run('deserializeWorld(lakeSave.meta, lakeSave.buffers); weather.next = 1e15;');
+      check(`${state} world starts with dry tree bases`, run('treeBases.every(i => !treeHeld(i) || mat[i] !== WATER)'));
+      const before = run('mat.slice(270 * W, 340 * W)');
+      const wakeTicks = state === 'fresh' ? 1 : 171;
+      ticks(run, wakeTicks);
+      check(`${state} lake moves within its startup wake window`, run('mat.subarray(270 * W, 340 * W)').some((m, i) => m !== before[i] && (m === water || before[i] === water)));
+      ticks(run, 6000 - wakeTicks);
+      const pools = surfacePools();
+      check(`${state} lake levels within two grains without disturbance`, pools.length > 0 && pools.every(p => p.max - p.min <= 2), JSON.stringify(pools));
+      // Reload can also thaw mountain snow into new puddles; check the original lake here.
+      const lake = pools.reduce((a, b) => a.width > b.width ? a : b);
+      check(`${state} original lake has no submerged tree base after settling`, run(`treeBases.every(i => i % W < ${lake.x0} || i % W > ${lake.x1} || !treeHeld(i) || mat[i] !== WATER)`));
+    }
+  }
+}
+done();