# Mystcraft Legacy instability audit (Milestone 6, issue #63)

This is a behavior contract for Milestone 6, **not a completed runtime instability system**. It compares the user-provided 0.13.7.06 class files at `/home/dnorberg/Documents/mystcraft-src/mystcraft-1.12.2-0.13.7.06/` with [Mystcraft Legacy source at commit `9bc8ddc`](https://github.com/Mystcraft/Mystcraft-Legacy/tree/9bc8ddc061845df0cd5ea47f4fdef773cff786ae). Values below are source defaults, not a claim that every historical config or server used them. Rivencraft 0.5.1.0 saves a provisional writing-instability score and repaired active-page order, but has no hazard loop yet.

## Score, grammar, and selection in Legacy

Legacy's [`AgeController`](https://github.com/Mystcraft/Mystcraft-Legacy/blob/9bc8ddc061845df0cd5ea47f4fdef773cff786ae/src/main/java/com/xcompwiz/mystcraft/world/AgeController.java) calculates `debug + symbol + block + book/base + bonus`, then applies difficulty 0/1/2/3 multipliers of 0.25/0.5/1/1.75. Global instability is enabled by default; an Age also has its own enable flag. The unmodified score is not simply “number of bad pages.” Block profiling may delay a usable score: `blockinstability` is null until **more than** 400 Age chunks are profiled, and `getInstabilityScore()` returns zero until then. It is recalculated after additional profiling. [`ChunkProfiler`](https://github.com/Mystcraft/Mystcraft-Legacy/blob/9bc8ddc061845df0cd5ea47f4fdef773cff786ae/src/main/java/com/xcompwiz/mystcraft/world/profiling/ChunkProfiler.java) compares watched block abundance with a baseline, subtracting only positive excess above each baseline. The baseline is profiled or read from balance config; [`InstabilityDataCalculator`](https://github.com/Mystcraft/Mystcraft-Legacy/blob/9bc8ddc061845df0cd5ea47f4fdef773cff786ae/src/main/java/com/xcompwiz/mystcraft/world/profiling/InstabilityDataCalculator.java) sets its default tolerance to 1.05, and default `useconfigs=false`. We should not copy its 400-chunk profiling delay or dynamic block scan into 1.21.1 without a separate performance case.

| Input | Verified Legacy behavior | Rivencraft M6 interpretation |
| --- | --- | --- |
| Missing required controller | Terrain, biome controller, weather, and lighting are generated when missing. `InstabilityData.missing.controller = 0`; lighting explicitly adds zero. Missing pages themselves are not a penalty. | Keep Age-seeded completion. No penalty solely for an omitted branch. |
| Repeated same symbol | `addSymbol` increments a per-`IAgeSymbol` count and adds that symbol's `instabilityModifier(count)`. This method is symbol-specific; there is no universal “duplicate = N” rule. | Distinguish legal repeated features/materials from repeated single-choice pages. Do not add a flat duplicate penalty to every occurrence. |
| Extra/conflicting controller | Registering a second terrain, biome, weather, or lighting controller adds `InstabilityData.extra.controller = 500`; the **last registered** controller replaces the prior one. This is separate from each symbol's own modifier. | Eligible supported conflicts may become unstable rather than fatal in #65, with deterministic winner and a saved penalty. |
| Dangling modifier | An unconsumed modifier contributes its `dangling` value; a default `Modifier` has `dangling=100`. Replacing a pending modifier charges the old one. `clearModifiers()` charges 20% (`clearPercentage=0.20`) of each pending value, with Java integer compound-assignment truncation. | Record the ordered offending page and a reason; calculate a deterministic penalty from the consumed/leftover modifier semantics, not from GUI position alone. |
| Unsupported/unmatched page | Legacy logs unmatched symbols during reconstruction and skips their logic; its `AgeData.getBaseInstability()` still has a TODO for calculating instability from pages. This is not a sound compatibility contract. | Remains fatal for *new* books until semantic and runtime support exists; never silently erase the page or pretend its effect applied. Existing saved books retain their IDs. |
| Other penalties/bonuses | `AgeController.addInstability(int)` is available to symbol logic. The base/book score is persisted as a `short`; Legacy's [`InstabilityBonusManager`](https://github.com/Mystcraft/Mystcraft-Legacy/blob/9bc8ddc061845df0cd5ea47f4fdef773cff786ae/src/main/java/com/xcompwiz/mystcraft/instability/bonus/InstabilityBonusManager.java) also has dynamic player death/behavior components. | Persist a versioned score breakdown for Age writing and environmental contributions. Do not infer death/troll mechanics from the mere existence of Legacy classes. |

Source for controller and modifier defaults: [`InstabilityData`](https://github.com/Mystcraft/Mystcraft-Legacy/blob/9bc8ddc061845df0cd5ea47f4fdef773cff786ae/src/main/java/com/xcompwiz/mystcraft/instability/InstabilityData.java), [`AgeController`](https://github.com/Mystcraft/Mystcraft-Legacy/blob/9bc8ddc061845df0cd5ea47f4fdef773cff786ae/src/main/java/com/xcompwiz/mystcraft/world/AgeController.java). The local 0.13.7.06 `Modifier.class` confirms `dangling_default=100`. Legacy grammar **ranks** weight which missing symbols are selected; they are not a direct instability score or deck tier. See [grammar audit](LEGACY_AGE_GRAMMAR_AUDIT.md) and [random weights](RANDOM_AGE_WEIGHTS.md).

[`InstabilityController`](https://github.com/Mystcraft/Mystcraft-Legacy/blob/9bc8ddc061845df0cd5ea47f4fdef773cff786ae/src/main/java/com/xcompwiz/mystcraft/instability/InstabilityController.java) rounds its working score toward zero to the current smallest registered positive provider cost (500 by default), then rebuilds active effects when that rounded score changes. Each seeded deck preserves its saved card order; new cards are shuffled with the Age seed. For each deck it subtracts the deck entry cost, then walks cards in order, paying each provider activation cost until the next card cannot be afforded. A provider's occurrences become its level. **Deck costs are gates, not mutually exclusive severity bands**: at high score multiple decks can contribute effects. Provider `.enabled` config can remove cards. The actual effect set cannot be inferred from a score alone without the saved deck orders and enabled providers ([`Deck`](https://github.com/Mystcraft/Mystcraft-Legacy/blob/9bc8ddc061845df0cd5ea47f4fdef773cff786ae/src/main/java/com/xcompwiz/mystcraft/instability/Deck.java), [`InstabilityManager`](https://github.com/Mystcraft/Mystcraft-Legacy/blob/9bc8ddc061845df0cd5ea47f4fdef773cff786ae/src/main/java/com/xcompwiz/mystcraft/instability/InstabilityManager.java)).

| Legacy deck | Entry cost | Examples of registered cards |
| --- | ---: | --- |
| basic | 0 | enemy regeneration/resistance, fatigue, hunger, poison, slowness, weakness |
| harsh | 2,500 | stronger/global potions, burning, lightning, wither |
| destructive | 10,000 | crumble, explosions, lightning, meteors, wither |
| eating | 15,000 | colored decay, blindness, nausea, wither |
| death | 20,000 | global blindness/nausea/wither, colored decay |

These entry costs are from [`InstabilityData.initialize()`](https://github.com/Mystcraft/Mystcraft-Legacy/blob/9bc8ddc061845df0cd5ea47f4fdef773cff786ae/src/main/java/com/xcompwiz/mystcraft/instability/InstabilityData.java), not guaranteed first-activation scores: each card also costs 500–5,000 depending on provider. A zero-cost basic deck still needs enough score to buy its first card. `stability.*` numbers in that file are provider activation costs, despite the misleading field name.

## Effect inventory and modern policy

[`InstabilityData.initialize()`](https://github.com/Mystcraft/Mystcraft-Legacy/blob/9bc8ddc061845df0cd5ea47f4fdef773cff786ae/src/main/java/com/xcompwiz/mystcraft/instability/InstabilityData.java) is the authoritative list of *registered* providers. Some implemented classes are commented out there; their existence does not mean they occur normally. Each Legacy environmental effect is called for chunks that the Age's runtime processes, often with its own chance. No per-Age global work budget is visible in these effect classes.

| Family | Legacy behavior | M6 disposition |
| --- | --- | --- |
| Player and hostile-mob potions | Local/global blindness, fatigue, hunger, nausea, poison, slowness, weakness, wither; hostile regeneration/resistance ([`EffectPotion`](https://github.com/Mystcraft/Mystcraft-Legacy/blob/9bc8ddc061845df0cd5ea47f4fdef773cff786ae/src/main/java/com/xcompwiz/mystcraft/effects/EffectPotion.java)). | Implement in #67 with server-only, Age-scoped entity targeting and rate limits. No effects in preview/snapshot worlds. |
| Colored decay | Blue, purple, red, white providers place advancing decay and extra-tick it; black provider is commented out. Decay handlers differ in spread/consumption ([providers](https://github.com/Mystcraft/Mystcraft-Legacy/tree/9bc8ddc061845df0cd5ea47f4fdef773cff786ae/src/main/java/com/xcompwiz/mystcraft/instability/providers), [handlers](https://github.com/Mystcraft/Mystcraft-Legacy/tree/9bc8ddc061845df0cd5ea47f4fdef773cff786ae/src/main/java/com/xcompwiz/mystcraft/instability/decay)). | Implement bounded, reversible-by-admin world mutation in #68; exact 1.12 spread/update rates require adaptation and tests. Exclude protected spawn/portal areas. Black/green/yellow are **not** proven active Legacy providers. |
| Lightning and explosions | Random per-chunk strike/explosion attempts ([`EffectLightning`](https://github.com/Mystcraft/Mystcraft-Legacy/blob/9bc8ddc061845df0cd5ea47f4fdef773cff786ae/src/main/java/com/xcompwiz/mystcraft/effects/EffectLightning.java), [`EffectExplosions`](https://github.com/Mystcraft/Mystcraft-Legacy/blob/9bc8ddc061845df0cd5ea47f4fdef773cff786ae/src/main/java/com/xcompwiz/mystcraft/effects/EffectExplosions.java)). | Implement in #69 with explicit block-damage and fire policy; no effect outside the Age. |
| Meteor, scorching | Meteor entity spawn and sky-exposed entity ignition ([`EffectMeteor`](https://github.com/Mystcraft/Mystcraft-Legacy/blob/9bc8ddc061845df0cd5ea47f4fdef773cff786ae/src/main/java/com/xcompwiz/mystcraft/effects/EffectMeteor.java), [`EffectScorched`](https://github.com/Mystcraft/Mystcraft-Legacy/blob/9bc8ddc061845df0cd5ea47f4fdef773cff786ae/src/main/java/com/xcompwiz/mystcraft/effects/EffectScorched.java)). | #70: modern meteor entity/impact needs an explicit damage budget; scorching can use modern fire/damage checks. Legacy `meteor/roar.ogg` is available. |
| Crumble and erosion | Crumble maps blocks to weaker states; erosion spreads adjacent fluids and has extra lake-generation methods ([`EffectCrumble`](https://github.com/Mystcraft/Mystcraft-Legacy/blob/9bc8ddc061845df0cd5ea47f4fdef773cff786ae/src/main/java/com/xcompwiz/mystcraft/effects/EffectCrumble.java), [`EffectErosion`](https://github.com/Mystcraft/Mystcraft-Legacy/blob/9bc8ddc061845df0cd5ea47f4fdef773cff786ae/src/main/java/com/xcompwiz/mystcraft/effects/EffectErosion.java)). | #70: bounded block palette and protected-area checks. Erosion's provider is commented out in Legacy registration: treat it as deliberate opt-in adaptation, not baseline parity. |
| Extra ticks | Registered alongside blue/purple/red/white decay, targeting decay blocks ([`EffectExtraTicks`](https://github.com/Mystcraft/Mystcraft-Legacy/blob/9bc8ddc061845df0cd5ea47f4fdef773cff786ae/src/main/java/com/xcompwiz/mystcraft/effects/EffectExtraTicks.java)). | Implement only as a bounded decay helper in #68; do not accelerate arbitrary blocks/block entities. |
| Other dormant code | Black decay, global burning, bedrock crumble, erosion provider are commented out. | Defer unless a later issue explicitly requests them. An authored symbol requiring one must fail clearly until supported. |

Assets in the supplied local tree: `assets/mystcraft/textures/blocks/decay_{black,blue,green,purple,red,white,yellow}.png`, corresponding decay block/item model JSON, and `assets/mystcraft/sounds/entity/meteor/roar.ogg`. Before importing, review attribution/license and fit modern 16×16 assets. Texture availability does not make an effect active. Use current Minecraft effects/sounds where adaptation is cleaner; no new artwork is needed for this audit.

## Rivencraft boundary and proposed safety contract

[`WritingGrammar`](../src/main/java/net/dnorberg/rivencraft/writing/WritingGrammar.java) classifies `INCOMPLETE` as seeded completion and supported writing defects as accepted instability. `AgeGenerationPlan.compile()` freezes the original writing, repaired active-page indexes, and a provisional writing-instability score before world generation. #64 now persists a versioned score breakdown; saved provider/deck choice remains future work. The plan must not mutate an already-created Age when a data pack changes. Server-side settings may disable execution, but should not rewrite the saved authored score.

For #65, **eligible-to-become-unstable** means a known, supported page whose semantics and resulting world are still deterministic: repeated/conflicting single-choice pages and otherwise valid out-of-order or misplaced pages. The implementation retains every original page, uses the last single-choice page, sorts active categories, and saves 500 per extra/conflicting choice or 100 per misplaced page. These are provisional Rivencraft values, not a full port of every `IAgeSymbol.instabilityModifier`. Missing branches are explicitly classified as zero-cost seeded completion; legal repeated feature/material pages are not automatically errors. **Remain fatal**: missing/duplicate/misordered Link Panel, over-capacity book, unresolved or schema-v1 display-only symbol, unsupported weather/angle/runtime profile/biome/feature, unavailable required optional mod, and any combination the compiler cannot represent safely. Binder and unbound-book previews distinguish blocked writing, seeded completion, and accepted instability before binding; the server revalidates on output. This intentionally differs from Legacy's silent unmatched-symbol skip, universal controller cost assumptions, and modifier-specific dangling costs. A full symbol-specific Legacy penalty port remains a separate balance task, not a claim of parity in this slice.

Automated #65 checks cover classification, preserved input slots on rejection, and an accepted unstable preview. The live output/one-time Age creation check is assigned to in-game testing because the GameTest storage phase stalled when that transaction ran; the test world is not retained.

Proposed server defaults for #66–#72 (to confirm during implementation): instability scoring on for newly created Ages; passive entity effects on; world-mutating hazards **off by default** until an operator opts in; explicit per-Age toggle and separate per-family switches. Enforce a central work budget rather than letting every loaded chunk and provider roll independently: default at most one hazard attempt per Age per 20 ticks, one block mutation per successful attempt, and no forced chunk loads. Budgets should be configurable with hard upper bounds, including active Ages, target radius, tick interval, block changes/explosions/meteor impacts, entity effect attempts, and decay spread. Never target another dimension, unloaded chunk, book preview/snapshot, protected spawn/link platform, or portal. Stop safely when the Age unloads or settings change. These are **Rivencraft proposals**, not Legacy defaults or code that exists today; implementation issues must test/adjust them, especially multiple concurrent Ages. Expose score breakdown, selected effects, enablement, and budget suppression in server diagnostics (#72).

M6 owns scoring, selection, effects, controls, and regression. M7 still owns portal/transport and broader polish; M6 must not depend on new M7 structures. An illegal biome/terrain combination that is presently unrepresentable remains a generation failure until a separate, safe compiler path exists; instability must not be used to disguise absent worldgen support. Existing pre-release saves need explicit migration behavior in #73 rather than a silent rescore.

## Verification and open questions

- Inspected pinned source for `AgeController`, `AgeData`, `GrammarTree`, `InstabilityData`, `InstabilityManager`, `InstabilityController`, `Deck`, all active provider families, effect classes, `ChunkProfiler`, and `InstabilityDataCalculator`; checked matching local 0.13.7.06 class names and `Modifier.dangling_default` with `javap`.
- The supplied extraction has no generated user balance config; registered defaults can be overridden or providers disabled. There is no single universal instability value for “wrong order” or “duplicate page.” `IAgeSymbol.instabilityModifier(count)` implementations and runtime configs determine the final Legacy value.
- Exact Legacy visual/decay behavior, dynamic bonus registration, and full 1.12 block-baseline parity need focused checks when their slices are implemented. Do not label proposed modern caps as source facts.