12. Ecosystem Interop and Reverse Conversion

12.1 Forward direction

block-array IR → serialize emits .nbt / .litematic / .schem / .mcstructure (Architecture). Each format is just a serializer; existing formats are additional backends around the block-array IR.

12.2 Reverse direction: the compiler only transliterates; an LLM does the lifting

The compiler does not build voxel→“this is a wall/roof” computer vision (it becomes unmaintainable). The compiler implements a robust faithful transliteration + verification + voxel-diff; the meaning lift is done as an LLM refactor of the raw-centric DSL (dogfooding the language). This is consistent with P5’s self-correction loop and the evaluation framework (Evaluation Framework).

cairn import house.litematic --mode raw    → house.raw.crn     # fill/raw_block centric (faithful transliteration)
(an LLM refactors house.raw.crn into a semantic DSL) → house.lifted.crn
cairn compile house.lifted.crn --edition java --target 1.21.4
cairn diff-blocks house.litematic house.lifted.crn           # voxel XOR → into self-correction

The compile→diff→patch self-correction loop:

E_DECOMPILE_DIFF: block IoU = 0.962 < threshold 0.985
  missing bbox=(12,4,3)..(18,6,3) mat=glass_pane → likely window repeat too small
  Suggested patch: edit window[id=front_windows] set repeat=4

Convergence thresholds: block IoU ≥ 0.985 / state_accuracy ≥ 0.995 / residual raw ≤ 5%. Exact match is not required; the residue is kept explicitly as raw_fill id=residual_* origin=imported.

12.3 Three tiers of faithful transliteration

“Naming” is the boundary between transliteration and lift.

L0 raw cells: one voxel per line. Too large; it bloats LLM context, so it is an intermediate only.
L1 spatial-compressed (the compiler’s ceiling): fill aggregation, AABB palette compression, resolved_state → intent_state inversion (stair facing=east half=top), symmetry/period as structural compression into raw_repeat. But no naming.
L2 semantic-lifted (the LLM’s ceiling): fill→wall, repeat→def/use, concrete block→mat_slot+theme.

# L1 (no naming, deterministic)
raw_repeat id=r03 count=5 step=3,0,0: raw_fill mat=@glass_pane from=0,2,0 to=1,3,0
# L2 (the LLM names and gives meaning)
window id=front_windows side=front mat_slot=glass repeat=5 ...

12.4 Import stamping and pitfalls

On import, stamp (edition, version) and provenance onto the block-array IR (.litematic→java, .mcstructure→bedrock, .schem→java). This connects to reproducibility/version awareness (Versioning and Editions).
Do not present import as “recovering author intent” (the biggest pitfall). Only voxels and some regularity can be recovered. Make this explicit in CLI/UI: W_SEMANTIC_LOSS.
Import-origin raw_fill is isolated with origin=imported / residual; it is not treated as first-class design DSL.
Preserve Litematica’s multiple regions / sub-region offsets as provenance rather than flattening, and map regions to a site / multiple structs.
For entity-bearing schematics, do not mark success on block IoU alone; keep a separate entity metric, and extract only first-class entities (Entities) — drop chest contents/command blocks.
Huge schematics (over 48³ / whole villages) blow up LLM context if lifted at once. Require an orchestration of chunk split → per-chunk L1 → per-part lift → join with site (streaming parse).
Legacy numeric-ID .schematic (pre-1.13 flattening) is not supported in v1 (Purpose and Scope).