---
title: CLAUDE.md Build-Gotchas Archive
type: reference
created: 2026-06-04
---

# CLAUDE.md Build-Gotchas Archive

This note holds the **full, verbose build-gotcha entries** that were condensed out of the committed `CLAUDE.md` on 2026-06-04 to keep that file under its 40 KB context-load limit. The condensed one-liners in `CLAUDE.md` link here and to the per-milestone Decision Records (`Docs/Vault/07_Sessions/_Decisions/DR-###`). Nothing was deleted — this is the long-form source of truth for the operational lessons; the DRs carry the design rationale.

> When a gotcha here is later proven wrong or superseded, strike it through and note the superseding DR rather than deleting it.

---

## Version history & stack status

> ✅ Reconciled 2026-06-02: `manifest.json` pins aligned to the resolved **Unity 6.4.7** lock (entities/entities.graphics 6.4.0, URP 17.4.0, test-framework 1.6.0, ugui 2.0.0, multiplayer.center 1.0.1) — a no-op re-resolve (lock unchanged, console clean). The values in the CLAUDE.md stack table match `packages-lock.json`. See [[DR-008_M5_HomeBase_BaseLayer_Storage]].

> **Version history & status (2026-05-30):** built on **6.4.7** (`6000.4.7f1`; Netcode 1.13.2 / Physics 1.4.6 / Entities 6.4.0). Briefly upgraded to **6.6.0a6**, where Netcode→6.6.0, Physics→6.5.0, Entities→6.5.0 all **renumbered** into the editor line — BUT the alpha's **Netcode/Transport runtime is broken** (all in-editor connections fail with "invalid wrapped network interface"; **confirmed engine bug** via a zero-gameplay repro — see `Docs/Vault` DR-002 and `Docs/UnityBugReport-Netcode-Transport-6.6.0a6.md`). **→ Reverting to Unity 6.4.7 for stable netcode runtime.** If returning to 6.6 later, expect the renumber and re-test the runtime. The M1 player slice should port to 6.4 / Netcode 1.13.2 with no or minimal changes — recompile and `read_console` after the downgrade.

---

## Build gotchas (learned — M1, 2026-05-30)

- **`Unity.Transforms` must be a DIRECT asmdef reference** for any assembly whose source-gen'd systems use `LocalTransform`/`LocalToWorld`. It is its own assembly; transitive visibility compiles your hand-written code but the Entities generator emits **CS0246** inside the `*.g.cs`.
- **Authoring asmdefs need `Unity.Entities.Hybrid`** (defines `Baker<T>`) **and `Unity.Collections`** (baking source-gen). A nested baker class must **not** be named `Baker` (it shadows `Baker<T>` → CS0308/CS0246) — name it `FooBaker`.
- **Never name an `IComponentData` `PlayerInput`**, and don't `using UnityEngine.InputSystem;` in a file that references such a component: it collides with `UnityEngine.InputSystem.PlayerInput`, and the Entities generator binds `RefRW<…>` to the *managed* class → a misleading **CS8377 "must be a non-nullable value type"**. Fully-qualify Input System types (`UnityEngine.InputSystem.Keyboard.current`) instead.
- `IInputComponentData` requires implementing **`FixedString512Bytes ToFixedString()`**.
- An input-gather system that reads the managed Input System belongs in `GhostInputSystemGroup` as a **non-Burst `ISystem`** (or `SystemBase`), never inside the prediction loop.

## Build gotchas (learned — M2 combat, 2026-05-31)

- **The generated Input Actions C# wrapper must live inside an asmdef** any system needs to reference. By default it generates next to the `.inputactions` (e.g. `Assets/Settings/`), which has no asmdef → it compiles into `Assembly-CSharp`, and asmdef assemblies (`ProjectM.Client`) **cannot** reference that. Fix: set the importer's `wrapperCodePath` (in the `.inputactions.meta`) to a path inside the consuming asmdef, e.g. `Assets/_Project/Scripts/Client/Input/ProjectMInput.cs`, and delete the old generated file. Read the action map via a managed `SystemBase` holding the wrapper; gather `Fire` as a netcode **`InputEvent`** (reset the field each frame, `.Set()` on the press edge — netcode latches the absolute `Count` into the command buffer; the live component value is only the per-tick delta).
- **Predicted-spawn classification cannot be `[BurstCompile]`d (Netcode 1.13.2).** The cross-assembly generic `Unity.NetCode.LowLevel.SnapshotDataBufferComponentLookup.TryGetComponentDataFromSnapshotHistory<T>()` trips a Burst **internal compiler error** (type-hash resolution). Make the classifier a plain non-Burst `ISystem` (it only runs when spawns are received — cold path). In 1.13.2 that method takes **`ref DynamicBuffer<SnapshotDataBuffer>`** (the public HelloNetcode sample's by-value `data` is from an older version).
- **A Burst *internal compiler error* corrupts the editor's Burst incremental cache.** After the error is fixed in code, newly-added `[BurstCompile]` entry points (systems **and** generated ghost-component serializers) keep logging `"... is not a known Burst entry point"` and run managed-fallback (slow → server tick-batching, ~30–40s play-enter). A clean compile + green tests + working runtime confirm the code is fine. Clear it with an **editor restart** (or delete `Library/BurstCache` while closed) — a domain reload alone does not.
- **Projectile/area hit tests must be swept, not point checks.** A point distance check tunnels straight through a target when the per-tick step exceeds the target radius — at high projectile speed *or* whenever the server tick-batches under load. Test the segment the projectile traversed this tick (`[curPos - dir*speed*dt, curPos]`) against each target; order the damage system `[UpdateAfter(MoveSystem)]`. (Caught at runtime, not by a point-based unit test — cover hit detection with a tunnelling regression test.)
- **In-editor input injection needs a focused Game view — unless you change two settings.** By default the Input System ignores injected/real device input while the Game view is unfocused, so headless (MCP `execute_code`) keypress simulation won't drive `IInputComponentData`. Fix (both now set in this project): `InputSettings.editorInputBehaviorInPlayMode = AllDeviceInputAlwaysGoesToGameView` + `Application.runInBackground = true`. For deterministic, device-independent validation prefer the editor-only **`DebugInputInjectionSystem`** (`ProjectM.Client`, `#if UNITY_EDITOR`): poke its statics from `execute_code` — `DebugInputInjectionSystem.Fire()` / `.SetMove(x,z)` / `.SetAim(x,z)` / `.Stop()` — to drive the local player's `PlayerInput` through the authentic command→prediction pipeline. (Validated: `SetMove` drives + replicates movement. One-shot `Fire` propagation needs a healthy editor — tick-batching under a degraded/corrupt-Burst editor drops one-shot `InputEvent`s while continuous values survive.)
- **Prototype presentation glue lives in `ProjectM.Client` as MonoBehaviours.** `PrototypeCameraRig` (on the Main Camera) is a tunable player-following ARPG cam (default mid 3/4 ~45° perspective) that reads the local player ghost's `LocalTransform` each LateUpdate. Bright prototype URP-Lit materials are in `Assets/_Project/Materials/` (player cyan, dummy red, projectile yellow, ground grey). `ProjectM.Client` now references `Unity.Transforms` directly (the rig reads `LocalTransform`).

## Build gotchas (learned — M5 physics-in-prediction, 2026-06-01)

- **Editing Assets `.cs` with the raw `Write` tool does NOT reliably trigger a Unity recompile** on an unfocused editor — `refresh_unity` did a domain reload *without* recompiling, so tests + `execute_code` ran a **stale assembly** (symptom: behaviour that exists in *neither* the old nor new source). **Always edit Assets `.cs` via MCP `apply_text_edits` / `create_script`** (Unity's own scripting pipeline) — never `Write`. (`Write`/`Edit` are fine for non-asset files: vault, asmdef JSON, etc.) See [[2026-06-01_M5_Physics_In_Prediction]].
- **Predicted physics is implicit — there is no `PredictedPhysics` toggle.** With the netcode-physics package present (`Unity.NetCode.Physics`, `…Physics.Hybrid`) and predicted ghosts carrying physics components, Netcode relocates `PhysicsSystemGroup` into the **`PredictedFixedStepSimulationSystemGroup`** (a child of `PredictedSimulationSystemGroup`, marked **OrderFirst**). `NetCodePhysicsConfig` only tunes lag-comp / run-mode / history. Put one in the gameplay subscene with `PhysicGroupRunMode = LagCompensationEnabledOrAnyPhysicsEntities` so the group runs whenever physics entities exist.
- **Unity Physics 1.x bakes built-in `UnityEngine` colliders + `Rigidbody`** — the old `PhysicsShapeAuthoring`/`PhysicsBodyAuthoring` (Physics 0.x) are **gone** (`unity_reflect` finds neither). Author a dynamic body with a `CapsuleCollider`/`BoxCollider` + `Rigidbody` (`useGravity=false` → planar/`PhysicsGravityFactor`=0; `isKinematic=false`; `interpolation=Interpolate` → `PhysicsGraphicalSmoothing`). Static colliders = collider, no Rigidbody, baked into the subscene (present identically in server + client worlds, deterministic, no replication).
- **`PhysicsVelocity` auto-replicates** — Netcode ships `PhysicsVelocityDefaultVariant` + a generated serializer, so a predicted-physics ghost needs **no hand-written `[GhostField]`** for velocity (`LocalTransform` is already replicated). Drive the character by writing `PhysicsVelocity.Linear`, not by teleporting `LocalTransform`.
- **`Rigidbody.FreezeRotation` is NOT honored by the DOTS baker** (baked `PhysicsMass.InverseInertia` stays non-zero). Hold a top-down character's facing by zeroing angular velocity each tick + writing rotation directly (`PlayerAimSystem`); set `PhysicsMass.InverseInertia = float3.zero` in a baker/system if a hard lock is needed.
- **Gravity-off bodies accumulate vertical contact impulses permanently** (a capsule rides up a box edge and floats away — looks like tunnelling, isn't). Pin players to the movement plane *after* the physics step: a system in `PredictedSimulationSystemGroup` `[UpdateAfter(PredictedFixedStepSimulationSystemGroup)]` clamping Y to `PlayerSpawner.SpawnPoint.y` + zeroing `Linear.y` (`PlayerPlanarConstraintSystem`).
- **The predicted physics group is OrderFirst**, so a system in `PredictedSimulationSystemGroup` with `[UpdateBefore(PredictedFixedStepSimulationSystemGroup)]` is **ignored** (OrderFirst/OrderLast wins) → 1-tick velocity offset (consistent across server/client/rollback — prediction stays in sync). For same-tick application, put the system *inside* `PredictedFixedStepSimulationSystemGroup` `[UpdateBefore(Unity.Physics.Systems.PhysicsSystemGroup)]` (verified to sort before the step) — but expect cosmetic "invalid UpdateBefore" warnings from the relocation.

> **Note (M5b):** `PlayerMoveSystem` + `PlayerPlanarConstraintSystem` from this milestone were **deleted** when the player became a Unity Character Controller. The predicted-physics infra (`NetCodePhysicsConfig`, baked static walls) is **kept**. See the M5b section.

## Build gotchas (learned — M5b Unity Character Controller, 2026-06-01)

- **The player is now a Unity Character Controller kinematic character, NOT a dynamic Rigidbody.** `PlayerMoveSystem` + `PlayerPlanarConstraintSystem` (M5) are **deleted**. Movement: `PlayerControlSystem` maps `PlayerInput.Move` × `EffectiveCharacterStats.MoveSpeed` → `CharacterControl` (via the unit-tested `CharacterControlMath.DesiredMovement`); `CharacterProcessor` (collide-and-slide) consumes it in `CharacterPhysicsUpdateSystem` (`[UpdateInGroup(KinematicCharacterPhysicsUpdateGroup)]`, relocated into the predicted loop). The DR-006 predicted-physics infra (`NetCodePhysicsConfig`, baked static walls) is **kept** — the CC character sweeps against that same PhysicsWorld.
- **A package declaring an older `com.unity.entities`/`com.unity.physics` dependency can still resolve on our renumbered stack** — Unity treats the dep as a SemVer **floor**, so Entities 6.4.0 satisfies a `1.3.15` requirement and is NOT downgraded. Don't trust a version-string mismatch as "incompatible": **probe** (add the package, confirm `packages-lock.json` kept Entities 6.4.0 / Physics 1.4.6 / Netcode 1.13.2 + a clean compile; rollback if not). CC 1.4.2 verified this way.
- **CC 1.4.2 API shape = `IKinematicCharacterProcessor<T>` + `KinematicCharacterDataAccess` + static `KinematicCharacterUtilities.Update_*`.** The legacy `KinematicCharacterAspect` (IAspect, instance `Update_*`) also exists but is NOT what the 1.4.x samples use — verify the installed shape with `unity_reflect`, don't assume. (A sub-agent's package-cache read disagreed with reflect; reflect + first-try clean compile won.)
- **`KinematicCharacterUtilities.BakeCharacter` aborts** (logs an error, adds nothing) **if the GameObject has a `Rigidbody`** and requires uniform (1,1,1) scale. The player prefab keeps its `CapsuleCollider` (baked into `PhysicsCollider`) but the M5 `Rigidbody` was removed. Two bakers on one prefab GameObject (`PlayerAuthoring` + `PlayerCharacterAuthoring`) is fine — both resolve the same entity.
- **`CharacterInterpolation` must be PredictedClient-only.** `BakeCharacter` adds it to all prefab versions; a `DefaultVariantSystemBase` registers `CharacterInterpolation → [GhostComponent(PrefabType = GhostPrefabType.PredictedClient)]` so it's stripped from server + interpolated-client prefabs (else double-interp on remotes). Verified: server ghost has no `CharacterInterpolation`, client ghost does.
- **Do NOT copy the CC sample's global `LocalTransform → DontSerializeVariant`.** It is project-wide and would break the non-character ghosts here (projectiles/dummies/pickups) that rely on stock `LocalTransform` replication. Our CC character replicates position via the normal owner-predicted `LocalTransform` path; only the `CharacterInterpolation` variant is registered.
- **Top-down CC config (planar, no gravity):** `AuthoringKinematicCharacterProperties` with `SnapToGround=false`, `InterpolateRotation=false` (rotation owned by `PlayerAimSystem`), `SimulateDynamicBody=false` (players don't physically push each other); gravity is handled in the processor by feeding `float3.zero` to `Update_GroundPushing` and never adding a gravity term. Result: stays on the spawn plane (y≈1) with no planar-pin system.

## Build gotchas (learned — M5 home base + shared storage, 2026-06-02)

- **Ownerless interpolated ghost ≠ owner-predicted for buffer replication.** A server-spawned **ownerless** ghost (e.g. the shared storage chest) replicates a `[GhostField]` `IBufferElementData` to all clients with **no `OwnerSendType` and no `GhostOwner`** — server mutations just propagate. `[GhostComponent(OwnerSendType = SendToOwnerType.All)]` (per `StatModifier`) is **only** for the predicting *owner* to recompute its own state; adding it (or a `GhostOwner`) to an ownerless ghost is wrong.
- **One-off shared-state actions belong on an `IRpcCommand`, not a predicted `InputEvent`.** RPCs are reliable, so deposit/withdraw landed even while the server tick-batched (the M2 one-shot `Fire` InputEvent drops under batching). RPC payloads are **plain blittable fields — no `[GhostField]`**; store an op as a **byte**, not an enum (cross-assembly enum-Burst hazard, same one that de-Bursted `ProjectileClassificationSystem`). For a **single** shared target, resolve it as a **server singleton** — never put an `Entity` (not stable cross-world) in the command; only reach for a ghost-id+spawn-tick (`SpawnedGhostEntityMap`) when there are many targets (and that lookup may force the handler off Burst).
- **Apply server-only RPC effects in the server `SimulationSystemGroup`, NOT the predicted loop** — the predicted loop re-runs on rollback and would double-apply. (Mutating a `DynamicBuffer` is not a structural change, so it's safe to do while iterating a *different* entity query, e.g. the RPC requests.)
- **Build-grid math must be deterministic + integer-stable.** Corner-origin + center-returning + **half-open** cell bounds + `math.floor` (not truncation — negatives). Lock `CellSize`/`PlotSize` as a coordinate space once: M6 placement builds on it; changing them later invalidates placed structures. (`BaseGridMath`, unit-tested in EditMode like `PlayerSpawnMath`.)
- **Runtime-spawn shared ghosts; don't bake them into the subscene.** A one-shot server spawner (mirrors `UpgradePickup`/`TrainingDummy`) keeps the subscene ghost-free and dodges the prespawn section-ack/CRC handshake. Do **not** add such a ghost to a connection's `LinkedEntityGroup` if it must survive that player's disconnect (the shared base is world-owned).
- **Build a correctly-configured ghost prefab by duplicating an existing one** (`UpgradePickup.prefab` → `Storage.prefab`, then swap the authoring MonoBehaviour via `manage_prefabs modify_contents`) rather than hand-adding `GhostAuthoringComponent` — its ownerless/interpolated settings (`HasOwner=0`, `DefaultGhostMode=Interpolated`) + `LinkedEntityGroupAuthoring` come along for free.
- **`execute_code` runs as a method body** — **no `using` directives** (they parse as statements → "Identifier expected"); fully-qualify every type (`Unity.Entities.World`, `ProjectM.Simulation.BaseAnchor`, …). Also: world flags overlap a shared `Game` bit, so identify worlds by `world.Name == "ServerWorld"/"ClientWorld"` rather than `(Flags & GameServer)`.
- **An unfocused editor throttles Edit mode to near-idle** → MCP pings time out and the bridge looks hung (it still *queues* commands — `telemetry_ping` succeeds). `Application.runInBackground` only helps in **Play** mode. If it wedges, focus or restart the editor; don't pile `refresh_unity` calls onto a blocked main thread. Prefer `refresh_unity scope=scripts` for code-only changes (`scope=all force` is heavy and contributed to a mid-session hang).

## Build gotchas (learned — M5.5 game feel & identity, 2026-06-02)

- **Move an ownerless INTERPOLATED enemy ghost SERVER-ONLY in the plain `SimulationSystemGroup`, never in `PredictedSimulationSystemGroup`** (interpolated ghosts aren't predicted; the server has no rollback). Use `[UpdateAfter(PredictedSimulationSystemGroup)]`, **NOT `[UpdateBefore]`** — the predicted group is **OrderFirst** in `SimulationSystemGroup`, so `UpdateBefore`/`After` *it* is silently *ignored* (Unity logs "Ignoring invalid UpdateBefore… OrderFirst/OrderLast has higher precedence"). A plain-`SimulationSystemGroup` server system therefore always runs **after** the predicted group, so a contact `DamageEvent` it appends drains the **following** tick (~16ms, fine for melee). Stock `LocalTransform` replication carries position — **no hand-written `[GhostField]`**. Build the enemy ghost by **duplicating an existing interpolated ghost** (`UpgradePickup.prefab` → `Enemy.prefab`) so the ownerless/interpolated `GhostAuthoringComponent` comes free — the training dummy is **not** a ghost (server-only → invisible to clients). See [[DR-009_GameFeel_Identity_FirstBlood]].
- **Derive an enableable gate from already-replicated state instead of replicating it.** Player `Dead` = a LOCAL enableable derived every predicted tick from the replicated `Health<=0` (`PlayerDeathStateSystem`, runs in **both** worlds, before movement/aim/fire) — the same derive-don't-replicate idiom as `StatRecomputeSystem`/`EffectiveCharacterStats`; rollback-correct on server + owner-client with **no `[GhostEnabledBit]`**. To write the bit on a currently-disabled entity the query must visit it: `.WithPresent<Dead>()` (write) vs `.WithDisabled<Dead>()` (alive-only run); `.WithAll<Simulate>()` ANDs independently. **Bake the enableable DISABLED** (`AddComponent<T>(e); SetComponentEnabled<T>(e, false);` in the baker) so instances spawn in the off state (instantiated entities inherit the prefab's enabled state). Respawn TIMING is server-only (`SimulationSystemGroup`, after the predicted group).
- **All juice/HUD = client-only managed `SystemBase` in `PresentationSystemGroup`** (once per frame, no rollback double-fire) that OBSERVES replicated state — never mutates the sim. Read ECS via `SystemAPI.Query` inside `OnUpdate` + `EntityManager.CompleteDependencyBeforeRO<T>()` — NOT from a MonoBehaviour `LateUpdate` (that throws the job-safety exception the camera rig hit). `Entity` is a stable client dict key for a ghost's lifetime — **prune the cache each frame** (a pruned enemy = a kill → death VFX at its last pos; **never `DestroyEntity` a ghost from the client** — `GhostDespawnSystem` owns despawn). Netcode-safe "hit-stop" = a camera punch, **never `Time.timeScale`** (it would corrupt the deterministic sim).
- **Asset-free presentation:** procedural `AudioClip.Create` SFX; a runtime `ParticleSystem` pool (Sprites/Default material + HDR start color so bursts bloom); a code-built uGUI HUD (`RawImage` over `Texture2D.whiteTexture` for anchor-driven bars + legacy `Text` with `Resources.GetBuiltinResource<Font>("LegacyRuntime.ttf")`). To edit a prefab asset's component in code: `PrefabUtility.LoadPrefabContents` → modify → **`SaveAsPrefabAsset(root, path)`** → `UnloadPrefabContents` (`SavePrefabAsset` rejects the contents root — "Can't save a Prefab instance"). Watch **shared-material bleed** when re-tinting (`M_Dummy` doubled as the wall material → orange walls; Husks got their own `M_Husk`). **ACES tonemapping needs the URP asset color grading mode = HDR** (`m_ColorGradingMode = 1`).
- **The "0 = ready" raw-`uint` cooldown sentinel can collide at tick wraparound** — a computed `ServerTick + delay` can equal 0. Route every cooldown/spawn "next tick" write through **`TickUtil.NonZero(...)`** (coerce 0→1), and compare stored ticks with `new NetworkTick(raw).IsNewerThan(serverTick)` / `.TicksSince(...)` — **never** raw `<` / subtraction — the HUD cooldown bar included. (Caught by the adversarial review; `RespawnMath` already guarded it.)
- **An unfocused editor stalls EditMode test INIT** ("tests did not start within timeout") and slows play-enter domain reloads — pass `run_tests(init_timeout=120000)` and retry; ask the operator to focus Unity for heavy build/test sessions (`Application.runInBackground` only helps in Play mode).

## Build gotchas (learned — art import / Synty packs → URP, 2026-06-03)

The imported store art (BefourStudios; future Synty) is **HDRP-authored** but we run **URP 17.4 + Entities Graphics** → source `M_*` materials render **magenta**. The reusable converter is `Assets/_Project/Scripts/Editor/EnvArtTools.cs` (menu `ProjectM/Art/1. Convert Curated Env Materials`); it outputs stock URP/Lit to `Assets/_Project/Materials/Env/`. See [[DR-010_Art_Import_URP_Conversion_Visual_Upgrade]].

- **Convert, don't switch pipelines.** Re-author to **stock URP/Lit** (`933532a4…`, the same shader our prototypes use → DOTS-instancing/Entities-Graphics compatible). FBX meshes + `T_*_B/_N/_ORM` textures are reusable as-is; the auto-generated `MI_*` URP stubs are blank. Switching the project to HDRP is NOT an option (breaks Entities Graphics).
- **A dark-lit screenshot MASKS material bugs — verify material *values*, not just the render.** `S_General` exposes a **float** `_BaseColorMultiply` and the real Color in `_AlbedoTint`. `HasProperty("_BaseColorMultiply")` is true but `GetColor()` on a float returns **(0,0,0)** (and logs a "doesn't have a color property" warning) → black albedo everywhere. **Always `shader.GetPropertyType(idx)`-guard before `GetColor`/`GetFloat`/`GetTexture`.**
- **Gate source emission on the `_Emissive` (0/1) flag AND a fixture name** — `S_General` carries a non-zero default `_EmissiveColor` even when off; reading it unconditionally makes crates/walls/domes glow (flat color can't reproduce the source emission mask).
- **`VolumeProfile.Add<T>()` does NOT persist the override** — on save the `components` list serializes `{fileID:0}` nulls (works in-session, gone after reload). Use `AssetDatabase.AddObjectToAsset(component, profile)` per effect, then `SaveAssets`; verify non-null refs on disk.
- **`LocalTransform.FromPosition()` resets Scale=1**, silently discarding a ghost prefab's authored scale (Scale is a replicated `[GhostField]` → consistent-but-wrong, not a desync). Server spawners must read the prefab's baked `LocalTransform` and override only Position (fixed in `UpgradePickupSpawnSystem`/`SharedStorageSpawnSystem`).
- **High metallic + no reflection probe + dark skybox = near-black.** Keep converted env metallic low (0.1–0.2); rely on albedo + direct light.
- **Static decor goes in the gameplay subscene** (Entities Graphics renders only baked/EG-spawned entities; a SampleScene MeshRenderer renders via classic URP). **Strip colliders** from cosmetic props (else they bake into the static PhysicsWorld the CC sweeps) and put **no GhostAuthoring** on scenery. Edit the subscene via `manage_scene load … additive` → place → `SaveScene` → `close_scene` (re-bakes on Play); the baked-entity view disappears while it's open additively — verify placement via `execute_code` over the scene roots, not the game view.
- **HUD-free beauty shot** = a **positioned `game_view` capture** (`view_position`/`view_rotation`) — direct camera rendering excludes Screen-Space-Overlay UI. `scene_view` rejects positioned capture.
- **VFX (GabrielAguiar) is now imported** (499 prefabs, ~94% Shuriken; 27 VFX-Graph). Wired into combat via [[DR-011_Synty_World_VFX_Integration]] — see the VFX gotchas below. VFX-Graph (hits/beams) packs still need separate URP setup if wanted.

## Build gotchas (learned — Synty world + GabrielAguiar VFX, 2026-06-03)

The world is now a cohesive **Synty** sci-fi colony + GabrielAguiar combat VFX. See [[DR-011_Synty_World_VFX_Integration]] / [[2026-06-03_Synty_World_And_VFX]].

- **Synty is URP-native — NO conversion** (unlike the HDRP BefourStudios art). The grounded world is built as **cosmetic classic-URP GameObjects in SampleScene** (`SyntyWorld` root), NOT the DOTS subscene — the custom `Synty/Generic_Basic` shader just renders, and you never have to verify its Entities-Graphics DOTS-instancing. Only the gameplay subscene needs Entities Graphics + the baked PhysicsWorld.
- **Cosmetic SampleScene colliders are inert to gameplay** — classic PhysX is separate from the DOTS PhysicsWorld (baked only from the subscene); the planar-pinned CC never sees them. So a cosmetic world needs no collider stripping for *gameplay*.
- **"Grounded" = surround + horizon, not a bigger plane** — a skyline ring of tall buildings + a planet/asteroid backdrop + a `Skybox/6 Sided` space skybox + light fog killed the floating-plane far better than extending the ground.
- **Swap a subscene object's VISUAL while keeping collision:** disable its MeshRenderer but keep the BoxCollider — the collider still bakes to the static `PhysicsCollider`, and a disabled renderer bakes no RenderMesh (invisible wall, collision intact). Used to retire the BefourStudios walls under the Synty world.
- **A GA "projectile" prefab is NOT a passive trail** — it ships a non-kinematic `Rigidbody` + collider + `ProjectileMoveScript` (self-propels, collides, spawns secondary muzzle/hit VFX). Any authored VFX dropped into a cosmetic slot must be **stripped to particles**: destroy `Rigidbody`/`Collider` and disable `Projectile`/`Move`-named MonoBehaviours BEFORE their `Start` runs (`CombatFeedbackSystem.StripCosmetic`). Verify a prefab's *components*, not its name.
- **VFX prefab → client SystemBase bridge:** a MonoBehaviour with a static `Instance` + prefab fields in the bootstrap scene (`VFXConfig`, mirrors `PrototypeCameraRig`) hands authored assets to the managed `CombatFeedbackSystem`; keep a procedural fallback so a null slot still runs. Derive VFX TTL from the prefab's longest ParticleSystem (not a blanket constant) and cap concurrent VFX to bound GC churn under swarms.
- **Projectile-follow VFX:** query `SystemAPI.Query<RefRO<LocalTransform>>().WithAll<Projectile>()` each presentation frame; dict-by-`Entity` spawn/reposition/prune (same idiom as the Health FX cache). The one-shot Fire `InputEvent` still drops under the **unfocused** editor, so fire-driven VFX (muzzle/trail/enemy-death) need a focused editor / real client to fire.

## Build gotchas (learned — aim controls: mouse cursor + gamepad, 2026-06-03)

The KBM/gamepad aim rework is [[DR-012_Aim_Controls_Cursor_Gamepad]] / [[2026-06-03_Aim_Controls_Cursor_Gamepad]].

- **Client-derived aim rides the EXISTING `PlayerInput.Aim` `[GhostField]` — no new netcode surface.** Mouse-cursor aim is computed client-side in `PlayerInputGatherSystem` (managed `SystemBase`, `GhostInputSystemGroup`, once/frame): `Mouse.current.position` → `Camera.main.ScreenPointToRay` → `AimMath.PlanarAimFromRay` (pure, Burst-safe, unit-tested) against the player's movement plane → write the player→cursor direction as `Aim`. Only the resulting direction crosses the wire; predicted/server systems are unchanged. Movement (`Move`) is already decoupled from facing (`Aim`/`PlayerFacing`), so **strafe-while-aiming is free** the moment `Aim` is the cursor. Don't add a mouse binding to the `Aim` action — the gather reads the device directly (no `.inputactions` edit → no wrapper regen).
- **Active input scheme = last-meaningful-actuation-wins, replicated as a `byte` (NOT an enum).** Detect KBM vs gamepad each frame (stick/trigger/button past a 0.04 lengthsq deadzone vs mouse-delta/click/movement-key; `InputDevice.lastUpdateTime` breaks ties; hold last when idle) and stream `PlayerInput.Scheme` (`InputSchemeId.KeyboardMouse=0/Gamepad=1`). It is a **byte** because it is compared inside the Burst-compiled `AbilityFireSystem` (the cross-assembly enum-in-Burst ICE hazard). The server gates the `AutoTarget` cone to `applied.InternalInput.Scheme == Gamepad` (read at the fire tick from the same `GetDataAtTick` lookup) → **precise mouse, gamepad-only assist**; mouse then predicts == server (fewer reconcile snaps).
- **A static presentation bridge must reset on play-enter.** `AimPresentation.Scheme` (mirrors `PrototypeCameraRig`/`VFXConfig` statics) needs `[UnityEngine.RuntimeInitializeOnLoadMethod(RuntimeInitializeLoadType.SubsystemRegistration)]` to reset — statics survive **fast-enter-playmode** domain reloads, and a stale value flashes the wrong cursor/reticle for the first frames (caught by the adversarial review).
- **Cursor/reticle = client `PresentationSystemGroup` `SystemBase` (`AimReticleSystem`) that OBSERVES, never mutates.** A flat world-space ground ring (primitive quad, `Sprites/Default` with a null-guard fallback, procedural ring texture) is the aim indicator for BOTH schemes — KBM at the cursor's ground-projection point, gamepad a fixed distance ahead along replicated `PlayerFacing`. The hardware cursor is **hidden while aiming + focused** (`Application.isFocused`-gated) and restored on focus-loss / `OnDestroy`. A radial **dead-zone** (`AimMath.PlanarAimFromRay` `deadZoneRadius`) holds facing when the cursor is over the character. **The KBM ground point is re-raycast INSIDE `AimReticleSystem`** (PresentationSystemGroup runs after the follow-cam's LateUpdate), not latched from the gather (`GhostInputSystemGroup`, before the move) — latching there drifts the ring a frame behind the cursor under the moving camera. Optional camera **aim look-ahead** (`PrototypeCameraRig.AimLeadDistance`, tunable) leads the framed point toward `PlayerFacing` (not the live cursor projection, to avoid a feedback loop). Headless validation: drive `DebugInputInjectionSystem` (now stamps `Scheme`) + force `AimPresentation.Scheme`; the **real cursor / live device-switch needs a focused Game view** (the unfocused editor can't inject mouse position).

## Build gotchas (learned — M6 Aether Cycle core loop, 2026-06-03)

The M6 core-loop slice (Expedition→Defend→Build) + the base/expedition world split. See [[DR-013_M6_Aether_Cycle_Region_Split]] / [[2026-06-03_M6_Aether_Cycle_CoreLoop]]. **Stages 0–1 done; 2–4 are the continuation.**

- **Base/expedition split = coordinate-region + per-connection `GhostRelevancy`, NOT `SceneSystem` streaming** (supersedes DR-008's framing). One server world; the expedition lives at `base + (1000,0,0)`; a server `RegionRelevancySystem` in `GhostSimulationSystemGroup` (before `GhostSendSystem`) sets `GhostRelevancyMode.SetIsIrrelevant` and each tick marks region-tagged ghosts irrelevant to connections whose player is in a different region. **Use `SetIsIrrelevant` (not `SetIsRelevant`)** so untagged/global ghosts (the future cycle director) stay relevant to everyone for free — you only enumerate cross-region ghosts to hide. Verify the API on the installed Netcode (1.13.2) with `unity_reflect`: `GhostRelevancy` singleton has `GhostRelevancyMode` + `NativeParallelHashMap<RelevantGhostForConnection,int> GhostRelevancySet`; `RelevantGhostForConnection{ int Connection; int Ghost }` (`Connection`=`NetworkId.Value`, `Ghost`=`GhostInstance.ghostId`). `RegionTag{byte Region}` is **server-only (NOT a `[GhostField]`)** — the server makes all relevancy decisions; the client just gains/loses ghosts. Reuses the runtime-ghost spawn path verbatim (no baked ghosts → no prespawn handshake), no async-load race; co-op drop-in is free.
- **Region transit + cycle phase use the established byte-RPC + tick-safe + server-`SimulationSystemGroup` patterns.** `RegionTransitRequest{byte TargetRegion}` (resolve sender via `ReceiveRpcCommandRequest.SourceConnection`→`NetworkId`→`GhostOwner`, flip `RegionTag`, teleport `LocalTransform`). The macro loop is a server-only `CycleState` singleton ([GhostField]-pre-annotated for the later CycleDirector ghost) driven by `CyclePhaseSystem` (`[UpdateBefore(WaveSystem)]`); it **gates `WaveSystem`** with a one-line `if (TryGetSingleton<CycleState>(out var c) && c.Phase != CyclePhase.Defend) return;`. All phase timers are wrap-safe `NetworkTick` (`TickUtil.NonZero` + `IsNewerThan`), never raw `uint <`.
- **Editing an existing `[BurstCompile]` ISystem's SystemAPI query set on an UNFOCUSED editor can leave a STALE Burst binary** (managed assembly recompiles with shifted source-gen query indices, Burst's async recompile doesn't finish) → runtime `InvalidOperationException: "… required component type was not declared in the EntityQuery"` thrown from an *unrelated* `GetSingleton<T>` in that system. **Tell:** the Burst stack reports the *old* line number for the failing call. Same family as the M2 Burst-cache gotcha. **Workaround:** `Jobs ▸ Burst ▸ Enable Compilation` OFF for the session (verify `BurstCompiler.Options.EnableBurstCompilation==false`) — everything runs the fresh managed source-gen. **Permanent fix = restart Unity** to clear the cache, then re-enable Burst. Prefer a **focused** editor for Burst-affecting edits.
- **Shared GLOBAL game-state (cycle phase, resource ledger, goal meter) rides an UNTAGGED ghost, never a region-tagged one** — `SetIsIrrelevant` hides a region-tagged ghost (e.g. the base storage) from players in the *other* region. The M6 resource **ledger** is a `StorageEntry` buffer on the global `CycleDirector` ghost, resolved via a distinct `ResourceLedger` tag — **never `GetSingleton<StorageEntry>`** (the base storage container owns a second `StorageEntry` buffer → "multiple instances" throw). Runtime-proven: the director stays relevant to an expedition player while the base storage despawns.
- **A hit/area sweep that runs in the PLAIN `SimulationSystemGroup` must NOT use `SystemAPI.Time.DeltaTime`** — that group sees the variable *wall-frame* delta, not the fixed tick step, so a `cur - dir*Speed*dt` segment is wrong. Store the per-tick step on the projectile (`Projectile.LastStep`, written by `ProjectileMoveSystem` in the fixed-step predicted group) and reconstruct the swept segment as `cur - dir*LastStep` — tunnel-safe with zero dependence on the consuming system's clock. `ResourceHarvestSystem` runs `[UpdateAfter(PredictedSimulationSystemGroup)]` so it only sees projectiles that survived `ProjectileDamageSystem` (relies on the ~1000u base/expedition coordinate gap so a base shot can't reach a node). A node hit by N projectiles in one tick: deposit per hit but `ecb.DestroyEntity` **at-most-once** (destroyed-bitset + local Remaining copy — a double destroy throws at Playback); persist the decremented `[GhostField] Remaining` via `SetComponent` so depletion carries across ticks.
- **New ghost prefab recipe (proven M6):** `manage_asset duplicate` UpgradePickup.prefab → `manage_prefabs modify_contents` (swap the authoring MonoBehaviour; **strip MeshFilter+MeshRenderer for an invisible state-holder**, keep them for a visible node). Wire the baked spawner into the gameplay subscene: `manage_scene load additive` → `set_active_scene Gameplay` → `manage_gameobject create` (+ `manage_components set_property` for the prefab ref, verify via `mcpforunity://scene/gameobject/{id}/component/...`) → `save` → `set_active_scene SampleScene` → `close_scene` (re-bakes on Play).
- **Run an adversarial design-review Workflow (3 critics: netcode/relevancy, determinism/prediction, reuse/scope → synthesize) BEFORE coding a netcode-heavy slice** — for M6 Stage 2 it caught every one of the above pre-implementation (relevancy trap, singleton collision, dt-trap, double-destroy, lazy-create hazard).
- **`manage_gameobject create` `component_properties` SILENTLY DROPS enum + Vector3 fields** (it set object-refs and simple scalars, but baked authoring enums/`Vector3` stayed at their C# defaults — two gates baked identical, one worked only by coincidence). **Always set those via a follow-up `manage_components set_property` (with a `properties` dict) and VERIFY through the `mcpforunity://scene/gameobject/{id}/component/{Type}` resource** (or, for a ghost, by reading the baked component in `execute_code` after Play). Same caveat applies to `manage_prefabs modify_contents` `component_properties`. Per-renderer color via `manage_material set_renderer_color` defaults to a runtime **PropertyBlock that does NOT persist into Play** — create a material asset (`manage_material create`) and `assign_material_to_renderer`, or use a prefab-stage assign, for colors that survive a domain reload.
- **Walk-in region gates (M6 visibility pass):** a baked `ExpeditionGate{FromRegion,ToRegion,Radius,ArrivalPos}` entity (visible primitive, collider stripped so you pass through) + a server `ExpeditionGateSystem` (plain group, `[UpdateAfter(CyclePhaseSystem)]`) proximity-transits a player whose `RegionTag` matches `FromRegion` (flip RegionTag + teleport to `ArrivalPos`, offset from the destination gate so no re-trigger). Returning to base mid-Expedition expires the cycle timer → Defend ("timer cap + early return"). The expedition is a *place* = cosmetic ground/pillars in **SampleScene** at the +1000 offset (classic URP, like SyntyWorld), not the DOTS subscene; gameplay nodes/gates are the baked subscene entities.
- **Build/automation foundation (M6 Stage 3, the M7 contract):** generic `PlacedStructure{[GhostField] byte Type; int2 Cell (server-only); uint NextTick; uint LastProcessedTick}` on an ownerless interpolated ghost (`RegionTag{Base}`, world-owned, runtime-spawned). **Bake the two tick fields NOW** — the turret reuses `NextTick` as its fire cooldown, and they are the deterministic-offline-catch-up linchpin M7 needs and that can't be reconstructed retroactively. Only `Type` replicates (client derives `Cell` from `LocalTransform` via `BaseGridMath.WorldToCell`). Data-driven `StructureCatalog` buffer (`{byte Type; Entity Prefab; byte CostResourceId; int CostAmount}`, modeled on `AbilityPrefabElement`); M7 adds a recipe column additively. **Occupancy is DERIVED** by scanning live structure ghosts into a Temp `NativeHashSet<int2>` (structures are the source of truth — restart/replay-safe), NEVER a mutable buffer on the immutable baked `BaseAnchor`.
- **Co-op placement atomicity:** `BuildPlaceSystem` commits the `StorageMath.Withdraw` + cell-reservation **IN-PLACE inside the RPC foreach** (only the `Instantiate` goes through the ECB) — the `StorageOpReceiveSystem` idiom — so two same-tick `BuildPlaceRequest`s for one cell can't both pass (validated: → exactly one structure + one withdraw). RPC carries `int CellX/CellZ` scalars, not `int2` (scalar-only RPC precedent).
- **Buildable turret = hitscan = reversed `EnemyAISystem`:** snapshot living Husks, nearest-in-same-region-within-Range, on the `NextTick` cooldown append a direct `DamageEvent{Damage, SourceNetworkId=-1}` → reuses `HealthApplyDamageSystem` (despawns at HP≤0). NO projectile → no tunnelling, no friendly-fire/team model. Plain server group `[UpdateAfter(PredictedSimulationSystemGroup)]`.
- **Resource-gated ability tiers reuse `StatModifier` — no new replicated component.** `AbilityUpgradeSystem` spends Aether and grows ONE `StatModifier{Target=Damage, Op=PercentAdd, SourceId=<sentinel>}` on the player (**replace-by-SourceId** so the `[InternalBufferCapacity(8)]` buffer stays bounded — repeated upgrades grow one row, not append); `StatRecomputeSystem` folds it into `EffectiveAbilityStats.Damage` on both worlds (the `UpgradePickup` path). `GoalProgress{[GhostField] int Charge, Target}` lives on the global CycleDirector ghost, single-writer in `CyclePhaseSystem`. **Disk-persistence writer is deferred to post-M7** (in-session-only state, per DR-008); freeze the save schema + bake the structure tick fields now so it's additive. See [[DR-014_M6_Build_Structures_Automation_Foundation]].