latitude-write-path-guards

name	latitude-write-path-guards
description	Canonical debugging + fix strategy for “wrong blocks in the wrong place” bugs. Forces evidence-first identification of the write path and mandates minimal, choke-point fixes (feature cancel / ChunkRegion / ProtoChunk). Forbids guessing via biome reassignment or pipeline invention.

Latitude — Write-Path Guards (Authoritative)

This skill is used when:

• a block appears where it should be impossible (snow/powder snow in warm bands, ice in tropics, etc.)
• a “biome says X but blocks say Y” contradiction occurs
• a symptom persists despite precipitation/surface-rule changes

Core rule: Do not guess the cause. Identify the write path that placed the block, then block/rewrite it at the narrowest safe choke point.

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Definitions

• Base biome: vanilla biome selection prior to Latitude override (often logged as base=).
• Out biome: Latitude-selected biome returned to generation (often logged as out= / what F3 shows).
• Write path: the actual code path that calls setBlockState to place the offending block.

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Mandatory protocol (evidence-first)

Step 1 — Capture the symptom precisely

Record:

• offending block(s) (e.g., powder_snow, snow_block)
• coords (x,y,z)
• F3 biome (out biome)
• zone/band if available

No fix proposals until these exist.

Step 2 — Determine write path

Allowed methods (choose the least invasive that gives proof):

A) Single-shot logs (preferred)

• Add a guard that logs once when it sees the offending block type.
• Include:
  • block id
  • pos
  • band/zone result
  • (optional) chunk origin

B) Stack trace capture (nuclear, one-time)

• On first sighting, throw a controlled exception or log a stack trace.
• Use only once, then remove.

C) Counter overlay

• Maintain counters for:
  • calls
  • matches
  • rewrites
• Expose via debug HUD/actionbar behind a flag.

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Allowed choke points (use this order)

1) Feature-level cancel (best when a known offender exists)

Examples:

• FreezeTopLayerFeature (snow/ice)
• other single features when proven by stack trace

Rule:

• Cancel only in the disallowed bands/zones.
• Log once behind a debug flag.

2) ChunkRegion#setBlockState rewrite (best general guard)

• Catches many feature/placement writes during generation.
• Use @ModifyVariable or @Redirect carefully.
• Must be non-recursive.

3) ProtoChunk#setBlockState rewrite (good for direct chunk writes)

• Catches many worldgen surface placements.
• Often simpler than MaterialRules interception.

4) Biome precipitation hooks (last resort, limited scope)

• Only affects weather-driven snow layers / precipitation checks.
• Does not stop worldgen-placed snow_block or powder_snow.

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Band/zone gating rules (no hardcoding)

Warm-band detection must:

• derive radius from world border:
  • radius = world.getWorldBorder().getSize() * 0.5
• compute:
  • t = abs(z) / radius
• determine zone using the same helper/constants used by Latitude (do not duplicate thresholds unless unavoidable).

If a helper is not available, the assistant must:

• locate it in code first, or
• mark thresholds as UNKNOWN and ask for the file/constant.

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Canonical rewrite policy (snow family)

When in warm bands (equator/tropics/subtropics as defined by Latitude):

• POWDER_SNOW -> AIR
• SNOW (layer) -> AIR
• SNOW_BLOCK -> DIRT above sea level, else STONE

All logging must be behind -Dlatitude.debugSnowGuard=true (or equivalent).

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Required safety constraints

• Guard must be non-recursive (do not call the same setBlockState path in a way that re-triggers).
• Guard must be band-gated (never global nukes unless explicitly set as a one-run diagnostic).
• Debug output must be gated and off by default for release.
• Fix must not change biome eligibility tables to hide the symptom.

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Forbidden fixes

• “Just move snowy biomes out of warm bands” (unless authority table explicitly says so)
• Reordering worldgen stages without proof
• Intercepting deep MaterialRules nested types unless all choke points above are proven insufficient
• Shipping with debug spam enabled

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Output format expected from the assistant

When asked to fix a block-placement bug, the assistant must produce:

1. Hypothesis list (max 3) tied to evidence
2. Chosen choke point and why
3. Exact file(s) + mixin target + method descriptor
4. One commit plan + test step
5. Rollback path (revert commit / toggle flag)