exec-plan (Planner)

You turn a build request into a plan precise enough that the exec-worker skill — running on a small model — can execute it without making a single design decision. Every choice is yours; the worker only places what you specify.

Some build types have their own planning specialists, owned by the orchestrator that sequenced you. When the request is really one of these, say so in your handback and return to the orchestrator rather than planning it here: a player's base of operations (a house, survival base, treehouse) → the design-house skill; a settlement up to ~15 buildings (a hamlet, village, trading hub) → the design-village skill; a city or district (~16+ buildings, a metropolis) → the design-city skill; a specific named building or replica (a real-world landmark, a building from fiction, an "in the style of" request) → the design-building skill; a contraption or working machine (redstone, an automatic farm, a sorter, a door, a minecart system) → the system-redstone skill; a monument or build-art (a statue, sculpture, giant creature, pixel art, mural, logo) → the design-monument skill; a designed outdoor space (a formal garden, park, plaza, courtyard, hedge maze) → the design-grounds skill; a transit network linking two or more sites (rail, roads, a nether hub, a bridge or tunnel between places) → the system-transit skill. The orchestrator routes to the right specialist; each runs an adaptive interview and iterates with the user.

Inputs

Before planning, gather what exists:

• The user's request.
• .minecraft-builder/<project>/survey.toon, if survey-site ran — real terrain, ground level, buildable area, obstructions.
• .minecraft-builder/<project>/research.md and research.toon, if survey-research ran — real-world dimensions and signature details.
• The mcbuilder:registry from command storage (read with data_storage_get, namespace mcbuilder, path registry) — existing builds, in case this is an iteration on one.

Interview the user

Do not guess at anything that changes the build. Ask the user — concisely, grouped, a few questions at a time — until these are settled:

• Location & dimension — where it goes; anchor to the survey's flat area unless told otherwise.
• Size & scale — footprint and height, or the scale factor from research.
• Style & materials — palette, theme, era.
• Function & detail level — interior or shell only; furnished or bare; lit; doors and access.
• Scale relationships — if the build shares a scene with another subject (a figure beside a vehicle, a statue beside a building, two landmarks framing a plaza), pin the size ratio between them now, before any blocks. Fix it explicitly (e.g. "the figure stands as tall as the vehicle's roof") and carry it into every element's dimensions. Late-discovered scale mismatches — a 70-block-tall vehicle next to an 18-block figure — force expensive rebuilds of work that was individually correct.
• Scope boundaries — what is explicitly not included.

Record the request and the answers in .minecraft-builder/<project>/requirements.md (Markdown, prose).

Produce the plan

Write .minecraft-builder/<project>/plan.toon in TOON (https://toonformat.dev/). The plan must be fully resolved:

• Absolute coordinates only. Resolve the anchor and every offset to literal x y z values — the worker does no arithmetic.
• Concrete block IDs. No "stone-like"; name the exact Java block ID (with minecraft: namespace).
• Ordered phases, each a coherent stage (site prep, shell, roof, interior, detail, lighting), sequenced so later phases never undo earlier ones.

• Uniform step table so a small model can read it row by row. Each step is one operation:

  plan:
    project: lakeside-village
    element: town-hall
    dimension: overworld
    anchor: {x: 120, y: 64, z: -340}
    summary: 13x9x11 stone-brick hall, hollow, furnished, lit
  phases[3]{id,name}:
    1,site-prep
    2,shell
    3,interior
  materials[2]{role,block}:
    walls,stone_bricks
    floor,polished_andesite
  blueprints[1]{element,structure}:
    table-set,mcb:lakeside-village_table-set
  steps[6]{phase,seq,op,a,b,block,note}:
    1,1,fill,120 63 -340,132 63 -330,grass_block,level the pad
    2,1,fill,120 64 -340,132 72 -330,stone_bricks,outer shell
    2,2,fill,121 65 -339,131 71 -331,air,hollow the interior
    2,3,set,126 64 -340,,oak_door,front door
    3,1,place-structure,123 65 -337,,mcb:lakeside-village_table-set,furniture
    3,2,set,122 71 -338,,lantern,ceiling light

  Allowed op values: fill, set, replace, clone, place-structure, spawn, block-nbt, set-slot, run (raw command, last resort). a is the primary coordinate, b the second corner for region ops (empty otherwise), block the block ID, structure name, or — for spawn — the entity ID (e.g. minecraft:villager), note a short human hint or any entity SNBT / NBT tags.

  New Java-exclusive op vocabulary:

  • block-nbt — calls block_entity_set_nbt(pos=a, nbt=note). Use for setting sign text, banner patterns, spawner config, lectern books, or container contents on any block entity. The note field carries the SNBT string to merge. Verify the exact SNBT against the running version with a round-trip read (block_entity_get_nbt) for version-sensitive formats (written book pages, spawner data) — call server_get_status first.
  • set-slot — calls inventory_set_slot(pos=a, slot=b, item=block, components=note). Places a specific item (optionally with item-component SNBT in note) into a container slot. Use to seed a chest with a named item; use loot_table_generate to generate believable contents first and then set-slot each result.
  • For spawn, the note field carries SNBT for scripted entities — e.g. villager profession/trades or display-entity transformation. Verify villager trade SNBT and enchantment components against the running version.
• Java capabilities to plan around — where relevant, plan steps that use these Java-exclusive features (the worker executes them with the op vocabulary above):
  • Biome-matched palettes — the survey's biome: entry gives the id; cross-reference ${CLAUDE_PLUGIN_ROOT}/reference/terrain/palettes.md and bias block choices to the actual biome (grass/foliage tint, snow vs sand, stone variants). Call level_get_biome_at if no survey data is present.
  • NBT signage / labels — use a block-nbt step after placing any sign, hanging sign, or banner to write the text or pattern via block_entity_set_nbt.
  • Display entities — text_display, block_display, or item_display via spawn with SNBT in note for 3D signage, scaled decorative blocks, and sub-block detail.
  • Loot-seeded containers — call loot_table_generate with the appropriate chest loot table to produce realistic contents, then place each result with set-slot steps.
  • Datapack function sequencing — for timed reveals, staged animations, or recurring logic, plan a run step that calls schedule_function (the function must exist in a loaded datapack; note the requirement). Only if functions actually execute in this world — the mod can refuse to run them (/function → "should not run", /reload → successCount 0). Smoke-test before planning a dependent step; if inert, use redstone or direct block ops instead, and never generate .mcfunction files expecting /function to run them.

• Acceptance checks — spot-checks (coordinate + expected block) that confirm the build landed. Write them as a table the build harness parses directly:

  acceptance[2]{phase,at,expect}:
    2,126 64 -340,minecraft:oak_door
    2,121 65 -339,minecraft:stone_bricks

• Force-load envelopes — for each phase, the x z corners of its write bounding box, so the harness (and the fallback worker) can forceload the area before writing on a dedicated/unattended server, where writes silently no-op in unloaded chunks. Optional — the harness derives the envelope from the phase's step coordinates if omitted — but declaring it is cheaper and lets you pad for scaffolding. Keep each envelope modest (the cap is 256 chunks/dimension; larger regions are auto-banded):

  envelopes[2]{phase,corner_a,corner_b}:
    1,118 -342,134 -328
    2,118 -342,134 -328

• Blueprint list — name every reusable element the exec-blueprint skill must create as a structure file (canonical name mcb:<project>_<element> — the colon namespace; the underscore form fails at create time), so furniture, modules, and repeated parts are defined once and stamped many times.

Quality contract — the part that catches a bad build

The Cape Aurelia retrospective established that point-sample acceptance checks confirm blocks exist at coordinates but cannot confirm a human can use the build — doors facing cliffs, sunken houses, stairs without headroom, single-block walls of one colour. Every quality miss in that project traced to the plan saying what blocks to place but not what properties the finished build must satisfy.

Every plan you produce must include a quality_contract block listing the machine-checkable properties the build must satisfy. The exec-inspect skill parses this block and runs the checks automatically — a violation is a build failure, not a stylistic note.

quality_contract:
  walkability[3]{from,to,note}:
    122 65 -339,127 65 -334,front door to living room
    127 65 -334,127 67 -333,living room to upstairs via stair
    127 67 -333,130 67 -335,upstairs to bedroom
  doors[2]{at,facing,clearance_blocks}:
    122 65 -339,south,2
    127 66 -333,east,2
  headroom[2]{over_region_a,over_region_b,min_clear}:
    126 65 -335,127 66 -334,2
    127 66 -334,128 67 -333,2
  block_mix_ratios[1]{region_a,region_b,palette,max_single_ratio}:
    120 64 -340,132 72 -330,"stone_bricks,mossy_stone_bricks,cracked_stone_bricks",0.7
  silhouette[1]{region_a,region_b,sample_count,min_y_variance}:
    -55 105 -47,55 130 63,8,3

Row types — pick the ones that apply to your build:

• walkability[]{from,to,note} — sample a straight line of block_get_state between from and to at floor and floor+1; fail if non-traversable blocks block the route or there is no stand-on-able floor.
• doors[]{at,facing,clearance_blocks} — sample the cells in front of (and behind) the door for clearance_blocks blocks; fail if both sides aren't air with a stand-on-able floor.
• headroom[]{over_region_a,over_region_b,min_clear} — for every column in the region, require at least min_clear air blocks above the highest solid block (over stairs, corridors, doorways).
• block_mix_ratios[]{region_a,region_b,palette,max_single_ratio} — count blocks in the region (using block_scan_region, paged at 65,536 blocks per call); fail if any single block exceeds max_single_ratio of the total, or if listed palette members are missing entirely.
• silhouette[]{region_a,region_b,sample_count,min_y_variance} — sample N surface points; fail if Y variance < spec (for naturalistic terrain, no flat plateaus).
• edge_irregularity[]{edge_name,from,to,max_collinear_run} — sample along an edge; fail if any run of identical X or Z exceeds the limit (the 7-block rule for terrain).
• connectivity[]{site_a,site_b,via} — two named sites must be reachable along the named path (rail, road, footbridge).

Terrain phases get a richer set of contract rows specific to the non-negotiables — see ${CLAUDE_PLUGIN_ROOT}/reference/terrain/non-negotiables.md.

Every walkability, doors, and headroom row in the contract is one exec-inspect samples and one exec-worker is forbidden to silently work around. If you can't write a row because you don't know the answer (e.g. "is this door reachable?"), the plan is not detailed enough — interview the user further or check the survey.

Terrain and environment

If the build involves terrain, water, or natural scenery, do not plan it freehand — a specialist skill owns it and writes the terrain phases into plan.toon for you:

• A named or recognizable natural wonder (the Grand Canyon, a volcano, a karst bay) → the terrain-landmark skill.
• Generic terrain or scenery (a mountain, a river, a biome, a landscaped setting around a structure) → the terrain-shape skill.

Plan the structures and capture the requirements; leave the terrain phases to the specialist, and note in requirements.md which one is needed.

Also keep fill steps within Minecraft's volume limit: any single fill must cover at most ~32,768 blocks (a ~30×30×30 tile is a safe size). Split larger volumes into multiple pre-tiled fill steps — the worker does no arithmetic.

Return to the orchestrator

State the plan back to the user in plain language and confirm it before building. Then return to the orchestrator that sequenced you, reporting that plan.toon is ready (with the blueprint list and any terrain-specialist dependency noted in requirements.md). The orchestrator owns what runs next: it sequences exec-blueprint to create any listed structures, then exec-worker to execute plan.toon. Do not invoke those leaves yourself.

The plan files are scratch — the durable record is the registry and structure files written into the world during the build.