terrain-integrate (Tier-3 leaf — the Integrate gate)

You remove the hard seam where a build meets untouched world. You are a forked leaf: you receive the footprint (a protect_box) and the surrounding survey, and you ground the build's edge. Read ${CLAUDE_PLUGIN_ROOT}/reference/terrain/integration.md (your method). This skill is GATE B of the spine — every footprint-bearing build runs it before inspect.

Method

1. Footprint + survey ring. Take the build's bounding box (protect_box) and survey a ring just outside it for the surrounding palette.
2. Apron band. Define a band of apron_width columns (8–24) outside the protect box; erosion strength tapers smoothstep(0, apron_width, dist) from full at the build edge to zero at the band's outer edge.
3. Erode the apron, protect the build. Thermal (+ light hydraulic) erosion over the apron only; the protect-box columns never change. Slumps the hard edge into a natural grade/talus.
4. Re-materialize to the surrounding palette. Grass tracks the new surface, rock on newly-steepened faces, sediment/beach where it filled, water re-flood to sea level; blend build-palette → surrounding-palette across the taper.
5. Dry-run → check → apply. ALWAYS run erosion with dry_run: true first. The dry-run returns height-delta stats (max_delta, mean_abs_delta, moved) — confirm the magnitude is sane (an apron slumps metres, not tens of metres) before re-running with dry_run: false. For a high-stakes seam, take the offline route instead (read → erode → render_views → apply) for a true visual pre-check. Under autonomy the dry-run check is the gate — no blind apply.

Erosion tools (mod ≥ 0.4.0)

• Thermal, synchronous — block_erode_region (the default for aprons and foundations: deterministic talus collapse, sub-second). Region is origin{x,z}
  • width/length + floor_y (a column grid like block_fill_columns, ≤ 65,536 cols). Pass protect_box{x0,z0,x1,z1} = the build footprint, apron = taper width (the smoothstep band), surface + subsurface = the dominant surveyed blocks, and dry_run: true first.
• Hydraulic, async — block_erode_hydraulic_start → _status → _result (for naturalising larger/coarser terrain with carved drainage). start returns a job_id; poll block_erode_hydraulic_status until state is DONE, then read block_erode_hydraulic_result. Same protect_box/apron/dry_run; region default 256×256, hard cap 512×512 (tile larger client-side).
• Offline route (any mod, or for a true visual pre-check): read apron heights via block_get_top_y/block_scan_region, build a HeightField, erode_thermal
  • blend.weld/pad_crop_smooth over the apron in tools/terrain, render_views to verify, then materialise via block_fill_columns and repaint biomes with level_fill_biome.

Current tool limits. The server erosion tools re-cap with a single surface/subsurface block and clear-above on lowered columns — they do not yet infer a multi-block palette, expose rock on newly-steepened faces, or re-flood water. For a seam that needs colour-blending, rock exposure, or water, use the offline route (until the 0.4.x erosion-depth upgrade lands).

Also: naturalize existing terrain

With no protect_box, the same flow naturalizes vanilla worldgen or a coarse placement — read, erode, re-materialize from the inferred (sampled) palette.

Carving a ledge into a wall: the sloped-back bench

A ledge cut for a path or wall-base rail is the same problem this skill exists to fix — geometry that reads as unnatural where built work meets rock. Cutting a plain horizontal tube into a vertical face leaves the rock above the cut overhanging with nothing beneath it; it reads as "floating." Carve the ledge as a bench whose outward wall recedes ~0.85 blocks per block of height, so the wall slopes back above the cut with no overhang, while the canyon/valley side stays open for the view. The receding wall is the talus principle applied to a cut face: a slumped grade above, not a vertical lip.

One ordering caveat decides whether the bench survives the placement. Run all the carve/clear fills first, then all the ledge/rail fills — never per-cell [clear, rail]. A per-cell order lets cell i+1's wider clear wipe cell i's just-placed ledge content before it sets, disconnecting the result along jogs and turns.

carves, fills = [], []
for cell in path:
    carves.extend(bench_clear(cell))   # ledge + sloped-back air (receding wall)
    fills.append(ledge_fill(cell))
batch(carves)   # ALL clears first ...
batch(fills)    # ... THEN all fills

Verify a carved bench in profile, not from iso: render a thin view: side|front slab through it so the overhang (or its absence) and the receding wall are visible — iso hides vertical faces. For batch caps and the separate silent-drop hazard (block_fill_batch can drop a few entries from a large batch, so re-scan a 1-wide feature after placing), see ${CLAUDE_PLUGIN_ROOT}/reference/execution/engine-limits.md. The rail mechanics for a wall-base loop (boosters, square U-turns, continuity-patch) live in skills/system-transit.

Return: the apron region, the erosion job summary, and a seam quality_contract row so exec-inspect (GATE C) can confirm no hard build↔world edge remains.