# Phase O — DatPath Unification — Design Spec

**Filed:** 2026-05-21
**Status:** ACTIVE
**Amended:** 2026-05-21 (post O-T1 audit; see [`docs/research/2026-05-21-phase-o-t1-wb-audit.md`](../../research/2026-05-21-phase-o-t1-wb-audit.md))
**Estimated effort:** ~7-8 working days, one ship-window.

> **Tagline:** ONE thing touches the DATs. Today we have two readers in
> process (acdream's `DatCollection` + WorldBuilder's
> `DefaultDatReaderWriter`) reading the same files independently. Phase O
> collapses that to one.

> **Amendment summary (2026-05-21):** O-T1 audit revealed three components
> the original spec listed (`LandSurfaceManager`, `EnvCellRenderManager`,
> `PortalRenderManager`) plus the open §9.2 question on `TerrainRenderManager`
> are **NOT in acdream's actual call graph** — we already have our own ports
> or never used them. **T6 is eliminated** entirely; T5 shrinks to stateless
> helpers only. T4 grows by 0.5d to include a refactor of `ObjectMeshManager`
> to take `DatCollection` directly (avoiding a permanent adapter indirection).
> Net effort estimate unchanged. Open question O-Q1 (thread-model) closed:
> verified safe — no worker-thread access to WB code.

---

## 1. Problem statement

As of Phase N.4 ship (2026-05-08), WorldBuilder is integrated as our
rendering + dat-handling base. Concretely:

- [`WbMeshAdapter.cs:79`](../../../src/AcDream.App/Rendering/Wb/WbMeshAdapter.cs:79) constructs **`_wbDats = new DefaultDatReaderWriter(datDir)`** — WB's own dat reader.
- Our **`DatCollection`** is constructed independently at startup for the rest of the client (network, physics, animation, clothing, audio, UI, etc.).

**Both readers open the same four files** (`client_portal.dat`,
`client_cell_1.dat`, `client_highres.dat`, `client_local_English.dat`)
with independent file handles and independent in-memory index caches.

**Costs:**

- **~50-100 MB duplicated index cache memory** (per [`WbMeshAdapter.cs:27`](../../../src/AcDream.App/Rendering/Wb/WbMeshAdapter.cs:27) comment).
- **Double seek cost** when the same dat block is read by both pipelines (mesh path via WB; surface metadata side-table via our `DatCollection`).
- **Cross-check awkwardness** — [`WbMeshAdapter.cs:224-262`](../../../src/AcDream.App/Rendering/Wb/WbMeshAdapter.cs:224) has explicit "if WE find the cell but WB doesn't" diagnostic code, born from the divergence.
- **Architectural smell** — a third-party feedback signal (AC community comment, 2026-05-21) flagged WB's dat-touching as "built for tools, not runtime."

**WB is MIT-licensed**, so the path to fixing this is to **extract its
load-bearing code into our repo** and route it through our `DatCollection`.
One reader, one cache, one source of dat truth.

---

## 2. Decisions log

| # | Decision | Why |
|---|---|---|
| O-D1 | **Extract WB code verbatim into our repo.** No re-port from retail decomp. No "improvements" while extracting. Discipline applies to algorithms (meshing math, texture decode, particle pipeline) — NOT to mechanical changes like parameter type renames. | CLAUDE.md is explicit: "Re-porting from retail decomp when WB already has a tested port is how subtle bugs (scenery edge-vertex, triangle-Z) keep slipping in." Verbatim copy preserves all the corner-case fixes WB already has. |
| O-D2 | **Make extracted code consume `DatCollection`**, not `IDatReaderWriter`. | Single source of dat truth. The whole point of the phase. |
| O-D3 | **Drop the `WorldBuilder.Shared` + `Chorizite.OpenGLSDLBackend` project references** at the end of the phase. | If we still reference WB after extraction, we haven't actually finished the work. |
| O-D4 | **Keep WB in `references/` for reading/comparison**. Don't delete the vendored directory. | We'll still want to grep WB during ports of NEW pieces (e.g., minimap renderer if/when we add it). |
| O-D5 | **MIT attribution per WB convention**. Add `NOTICE.md` entry crediting WorldBuilder for the extracted code. | License compliance. |
| O-D6 | **One ship-window, not sliced**. Either the whole extraction lands and `references/WorldBuilder` is dropped, or we roll back the entire phase. | Half-extracted state (some WB code in our repo, some still referenced) is worse than either endpoint. |
| **O-D7** | **Refactor `ObjectMeshManager` to take `DatCollection` directly** (not via an adapter). Safety check at T4 — fall back to thin `DatCollectionAdapter : IDatReaderWriter` if `_dats.X` call-site count inside ObjectMeshManager exceeds 20. | After extraction, `ObjectMeshManager` is OUR code; our code should use our types. An adapter would be permanent tech debt obscuring data flow. O-D1's "verbatim copy" discipline applies to algorithms, not parameter types. |
| **O-D8** | **Drop four originally-listed components from the extract list:** `LandSurfaceManager`, `EnvCellRenderManager`, `PortalRenderManager`, `TerrainRenderManager`. | O-T1 audit confirmed these aren't reachable from acdream's code graph. `LandSurfaceManager` and `TerrainRenderManager` have our own ports (`TerrainBlending.cs`, `TerrainModernRenderer.cs`); EnvCell/Portal are rendered via the mesh pipeline, not via WB's dedicated renderers. |
| **O-D9** | **Promote 3 `internal` types in Chorizite to `public`** when extracted: `EmbeddedResourceReader`, `TextureFormatExtensions`, `BufferUsageExtensions`. | We vendor them; we control the namespace. Keeping internal would force same-assembly placement with no benefit. |
| **O-D10** | **Strip `[MemoryPackable]` from `TerrainEntry`** when copying into our tree. | We don't serialize the struct. Avoids adding `MemoryPack` as a NuGet dep for an unused attribute. |
| **O-D11** | **Namespace `AcDream.Core.Rendering.Wb.*`** for extracted code (vs topic-based namespaces). | Preserves the "this came from WB" audit trail. A later phase can re-organize once the dust settles. |
| **O-D12** | **Drop `ResolveId(uint)` and the `[indoor-upload] NULL_RESULT` diagnostic block** in `WbMeshAdapter.cs` at T7. | Only caller of `ResolveId` is the diagnostic; the diagnostic depends on the second `_wbDats` which goes away. The block has served its Phase 2 cell-resolution-divergence investigation purpose. |

---

## 3. Architecture overview

### Today (Phase N.4–A.5 state)

```
┌─────────────────────────┐       ┌──────────────────────────────────┐
│ acdream subsystems      │       │ WorldBuilder (referenced project)│
│ - Network               │       │  ┌────────────────────────────┐  │
│ - Physics               │ ───→  │  │ DefaultDatReaderWriter     │  │
│ - Animation             │       │  │  (opens 4 .dat files)      │  │
│ - Clothing/Audio/UI     │       │  └────────────┬───────────────┘  │
│ - Surface metadata      │       │               │                  │
└──────────┬──────────────┘       │  ┌────────────▼───────────────┐  │
           │                      │  │ ObjectMeshManager          │  │
           │ DatCollection        │  │ TextureHelpers             │  │
           │ (opens same 4 files) │  │ SceneryHelpers             │  │
           │                      │  │ OpenGLGraphicsDevice       │  │
           ▼                      │  └────────────────────────────┘  │
    ┌──────────────┐              └──────────────────────────────────┘
    │ Dat files    │              ▲
    │ (same files, │──────────────┘
    │  two readers)│
    └──────────────┘
```

### Phase O target

```
┌─────────────────────────────────────────────────────────────────┐
│ acdream subsystems                                              │
│ - Network / Physics / Animation / Clothing / Audio / UI         │
│ - Mesh pipeline   (extracted from WB.ObjectMeshManager,         │
│                    refactored to take DatCollection)            │
│ - Texture decode  (extracted from WB.TextureHelpers)            │
│ - Scenery helpers (extracted from WB.SceneryHelpers)            │
│ - Terrain helpers (extracted from WB.TerrainUtils + TerrainEntry)│
│ - GL infra        (extracted from WB.OpenGLGraphicsDevice etc.) │
└──────────────────────────┬──────────────────────────────────────┘
                           │
                           │ DatCollection (the ONLY reader)
                           ▼
                  ┌──────────────┐
                  │ Dat files    │
                  └──────────────┘
```

### What stays acdream-original (unchanged by this phase)

- [`TerrainModernRenderer.cs`](../../../src/AcDream.App/Rendering/TerrainModernRenderer.cs) (Phase N.5b — uses `LandblockMesh.Build` with retail's `FSplitNESW`).
- [`TerrainBlending.cs`](../../../src/AcDream.Core/Terrain/TerrainBlending.cs) (our port of WB's `LandSurfaceManager` — already lives in acdream).
- Network, physics, animation, movement, UI, audio, chat, streaming controller, plugin API.
- Our `DatCollection` (becomes the **only** dat reader).
- The `Wb*` adapter layer (`WbMeshAdapter`, `WbDrawDispatcher`, `LandblockSpawnAdapter`, `EntitySpawnAdapter`, etc.) — those stay in `AcDream.App/Rendering/Wb/`; they bridge our world to the extracted code.

---

## 4. Component changes (audit-corrected)

### 4.1 Mesh pipeline (T4 — the load-bearing extraction)

> **Layer placement:** mesh-pipeline files live under `src/AcDream.App/Rendering/Wb/` (NOT Core), because `ObjectMeshManager` and its supports use `Silk.NET.OpenGL` types directly (ManagedGL*, GLSLShader, etc.) and CLAUDE.md forbids Core depending on GL.

| WB source | New acdream home | Adaptation |
|---|---|---|
| `Chorizite.OpenGLSDLBackend.Lib.ObjectMeshManager` | `src/AcDream.App/Rendering/Wb/ObjectMeshManager.cs` | **Refactor**: replace `IDatReaderWriter` field/ctor-param with `DatCollection` (Core type — App can reference it). Update `_dats.X` call sites. Safety check at T4: if >20 sites, fall back to thin adapter. |
| `Chorizite.OpenGLSDLBackend.Lib.ObjectRenderBatch` + `ObjectRenderData` | Same directory | Verbatim copy. |
| Particle batcher + emitter (T4 supports) | Same | Verbatim copy. |
| `Chorizite.OpenGLSDLBackend.Lib.DebugRenderSettings` | Same | Verbatim copy (constructor parameter type only). |
| `GlobalMeshBuffer`, modern render data structs | Same | Verbatim copy. |

### 4.2 Texture pipeline + GL infrastructure (T3)

> **Layer split:** `TextureHelpers` is pure (no GL, no dat) → goes to Core. All other GL infra → App.

| WB source | New acdream home | Adaptation |
|---|---|---|
| `Chorizite.OpenGLSDLBackend.Lib.TextureHelpers` | `src/AcDream.Core/Rendering/Wb/TextureHelpers.cs` | Verbatim. Pure functions — no dat / no GL. |
| `Chorizite.OpenGLSDLBackend.OpenGLGraphicsDevice` | `src/AcDream.App/Rendering/Wb/OpenGLGraphicsDevice.cs` | Verbatim. Touches GL. |
| `ManagedGL{Texture,TextureArray,VertexBuffer,IndexBuffer,VertexArray,FrameBuffer,UniformBuffer}` | App `Wb/` directory | Verbatim. Touches GL. |
| `GLSLShader`, `GLHelpers`, `GLStateScope` | App `Wb/` directory | Verbatim. Touches GL. |
| `EmbeddedResourceReader` (internal → public) | App `Wb/` directory | Promote `internal` → `public`. |
| `TextureFormatExtensions`, `BufferUsageExtensions` (internal → public) | App `Wb/` directory | Promote `internal` → `public`. |

### 4.3 Stateless helpers (T5)

| WB source | New acdream home | Adaptation |
|---|---|---|
| `Chorizite.OpenGLSDLBackend.Lib.SceneryHelpers` | `src/AcDream.Core/Rendering/Wb/SceneryHelpers.cs` | Verbatim. Pure functions. |
| `WorldBuilder.Shared.Modules.Landscape.Lib.TerrainUtils` | `src/AcDream.Core/Rendering/Wb/TerrainUtils.cs` | Verbatim. |
| `WorldBuilder.Shared.Modules.Landscape.Models.TerrainEntry` | Same | Verbatim **except** strip `[MemoryPackable]`. |
| `WorldBuilder.Shared.Modules.Landscape.Models.CellSplitDirection` | Same | Verbatim enum. |

### 4.4 NOT extracted (dropped from spec §4)

Audit confirmed these are not in acdream's reachable closure. Documented here for posterity so the next person looking at the spec knows why they're missing.

| Component | Why not extracted |
|---|---|
| `LandSurfaceManager` | Already ported as [`src/AcDream.Core/Terrain/TerrainBlending.cs`](../../../src/AcDream.Core/Terrain/TerrainBlending.cs). |
| `SceneryRenderManager` | Acdream uses only the stateless `SceneryHelpers`. The render pipeline is `WbDrawDispatcher`. |
| `EnvCellRenderManager` | Acdream renders env cells via `ObjectMeshManager.PrepareEnvCellMeshData` + `WbDrawDispatcher`. |
| `PortalRenderManager` | Same — portal cells go through the same path. |
| `TerrainRenderManager` | Already replaced by [`src/AcDream.App/Rendering/TerrainModernRenderer.cs`](../../../src/AcDream.App/Rendering/TerrainModernRenderer.cs) (Phase N.5b). |
| `FontRenderer`, `MinimapRenderer`, `BackendGizmoDrawer`, `AudioPlaybackEngine` | Editor-only or replaced by our own subsystems. |
| `WorldBuilder.Shared/Hubs`, `Migrations`, `Repositories`, editor `Services` | Editor-only (SignalR, EF Core). |

### 4.5 What we DROP outright

- `_wbDats = new DefaultDatReaderWriter(datDir)` in [`WbMeshAdapter.cs:79`](../../../src/AcDream.App/Rendering/Wb/WbMeshAdapter.cs:79) — replaced with the existing `_dats: DatCollection` field passed straight to `ObjectMeshManager`.
- The `[indoor-upload] NULL_RESULT` cross-check block at [`WbMeshAdapter.cs:224-262`](../../../src/AcDream.App/Rendering/Wb/WbMeshAdapter.cs:224) and the `_pendingEnvCellRequests` tracker. Phase 2 cell-resolution diagnostic; no longer needed.
- `_wbDats?.Dispose()` in `WbMeshAdapter.Dispose()`.
- The two `<ProjectReference>` entries in [`AcDream.App.csproj:38-39`](../../../src/AcDream.App/AcDream.App.csproj:38) and [`AcDream.Core.csproj:27-28`](../../../src/AcDream.Core/AcDream.Core.csproj:27) to `WorldBuilder.Shared` + `Chorizite.OpenGLSDLBackend`.
- The two `WorldBuilder.Shared/Services/{IDatReaderWriter,DefaultDatReaderWriter}.cs` files — never copied into our repo.
- [`tests/AcDream.Core.Tests/Terrain/SplitFormulaDivergenceTest.cs`](../../../tests/AcDream.Core.Tests/Terrain/SplitFormulaDivergenceTest.cs) — one-time data-collection test that informed the N.5b path-C decision; job done.

---

## 5. Task breakdown

| Task | Description | Effort |
|---|---|---|
| O-T1 | **DONE 2026-05-21.** Audit WB call graph — produce closure of every WB type/file we transitively use. Output: [`docs/research/2026-05-21-phase-o-t1-wb-audit.md`](../../research/2026-05-21-phase-o-t1-wb-audit.md). | 0.5d ✓ |
| O-T2 | Create `src/AcDream.Core/Rendering/Wb/` + `src/AcDream.App/Rendering/Wb/` (already exists) directory structure. Add `NOTICE.md` entry with MIT attribution to WB. | 0.25d |
| O-T3 | **Extract texture / GL infrastructure** (~15 files, ~3.1K LOC): `TextureHelpers`, `OpenGLGraphicsDevice`, `ManagedGL*`, `GLSLShader`, `GLHelpers`, `GLStateScope`. Promote 3 internal types to public. **Verify**: does our closure touch `SixLabors.ImageSharp`? If yes, strip imports / inline byte handling. If no, document. Build green. | 1d |
| O-T4 | **Extract mesh pipeline** (~8 files, ~3.3K LOC): `ObjectMeshManager`, `ObjectRenderBatch`, `ObjectRenderData`, supports. **First 30 min: count `_dats.X` call sites inside `ObjectMeshManager`. If ≤20, refactor in place to take `DatCollection`. If >20, write thin `DatCollectionAdapter : IDatReaderWriter` and pass that.** Document the choice + actual count in the T4 commit. Build green. All existing tests green. | 2.5d |
| O-T5 | **Extract stateless helpers** (5 files, ~782 LOC): `SceneryHelpers` (Chorizite), `TerrainUtils` + `TerrainEntry` + `CellSplitDirection` (WB.Shared). Strip `[MemoryPackable]` from `TerrainEntry`. Update `using` lines in [`SceneryGenerator.cs`](../../../src/AcDream.Core/World/SceneryGenerator.cs), [`WbSceneryAdapter.cs`](../../../src/AcDream.Core/World/WbSceneryAdapter.cs), [`SurfaceDecoder.cs`](../../../src/AcDream.Core/Textures/SurfaceDecoder.cs), and [`tests/AcDream.Core.Tests/Textures/TextureDecodeConformanceTests.cs`](../../../tests/AcDream.Core.Tests/Textures/TextureDecodeConformanceTests.cs) to point at the new `AcDream.Core.Rendering.Wb.*` namespace. Build green. | 0.5d |
| ~~O-T6~~ | ~~EnvCell + portal renderers~~ | **eliminated** by O-D8 |
| O-T7 | **Drop project references** from [`AcDream.App.csproj`](../../../src/AcDream.App/AcDream.App.csproj) and [`AcDream.Core.csproj`](../../../src/AcDream.Core/AcDream.Core.csproj). Drop `_wbDats` field + ctor + dispose + the `[indoor-upload] NULL_RESULT` block from `WbMeshAdapter`. Delete `SplitFormulaDivergenceTest.cs`. Build green + tests green (minus the deleted test). | 0.5d |
| O-T8 | **Verification gate** — visual side-by-side with main against retail in three scenes: Holtburg town (outdoor + scenery), inn interior (EnvCell), and a dungeon (portals). **Screenshots captured BEFORE T3 starts**, compared after T7. User confirms "looks identical." Measure resident memory at radius=4 + 50 entities visible; confirm ≥50 MB reduction vs main. | 1d (incl. user time) |
| O-T9 | **Ship** — single merge to main with one descriptive commit per task (T2..T7), then a "drop WB references" final commit. Update CLAUDE.md to remove the "WB is referenced as projects" language and replace with "extracted into src/AcDream.Core/Rendering/Wb/." Update [`docs/architecture/worldbuilder-inventory.md`](../../architecture/worldbuilder-inventory.md). | 0.5d |
| **Total** | | **~6.75d focused work + 1d verification + 0.5d ship ≈ 7.75d** |

---

## 6. Acceptance criteria

**Build + test:**

- [ ] `dotnet build` green across the solution.
- [ ] `dotnet test` green; no regression vs the **1147 + 8 baseline minus
      `SplitFormulaDivergenceTest.cs`'s test count** (delete is deliberate, not a regression).

**Reference deletion (the architectural goal):**

- [ ] **Zero references to `WorldBuilder.*` or `Chorizite.OpenGLSDLBackend.*` namespaces** in `AcDream.App.csproj` and `AcDream.Core.csproj`. (`PackageReference` for `Chorizite.DatReaderWriter` stays — that's the NuGet DatReaderWriter lib, not WB.)
- [ ] **Zero `using WorldBuilder.*` or `using Chorizite.OpenGLSDLBackend*`** in `src/AcDream.*` (extracted code lives in `AcDream.Core.Rendering.Wb.*` now).
- [ ] **`DefaultDatReaderWriter` referenced in exactly zero places** in our source. `DatCollection` is the only dat reader.
- [ ] `_wbDats` field + ctor + dispose removed from `WbMeshAdapter.cs`. `[indoor-upload] NULL_RESULT` block at lines 224-262 removed.
- [ ] `SplitFormulaDivergenceTest.cs` deleted.

**Memory + visual (user-facing wins):**

- [ ] Resident memory at `streaming: radius=4` + 50 entities visible: **>50 MB reduction** vs. pre-Phase-O main.
- [ ] **Visual side-by-side with main**: Holtburg town, an inn interior, a dungeon — all render identically. User confirms via screenshots taken BEFORE T3 and AFTER T7.

**New per audit:**

- [ ] T4 commit message documents the `ObjectMeshManager` dat-shim path taken (refactor in place if ≤20 sites, or adapter if >20). With the actual count.
- [ ] T3 commit message documents the 3 internal-to-public type promotions in Chorizite (`EmbeddedResourceReader`, `TextureFormatExtensions`, `BufferUsageExtensions`).
- [ ] T3 commit message states whether `SixLabors.ImageSharp` was reachable. If yes: documents which paths were stripped. If no: explicit "ImageSharp not reachable" note.

**Docs + attribution:**

- [ ] `NOTICE.md` includes WB attribution per its MIT license.
- [ ] `references/WorldBuilder/` directory remains in the repo as a read-reference; not in any csproj.
- [ ] `CLAUDE.md` updated: WB is now a *read reference*, not a *project dependency*. The "WB integration cribs" section is rewritten to point at our extracted code.
- [ ] [`docs/architecture/worldbuilder-inventory.md`](../../architecture/worldbuilder-inventory.md) updated to reflect the new ownership.

---

## 7. Risks + mitigations (audit-updated)

| Risk | Likelihood | Severity | Mitigation |
|---|---|---|---|
| Re-introduce bugs WB already fixed (edge-vertex, triangle-Z) | Medium | High | **Verbatim copy at the algorithm level.** The refactor change at T4 is API-shape only; meshing math / texture decode / particle pipeline stay byte-identical. |
| `ObjectMeshManager` refactor reveals >20 `_dats.X` call sites | Low-Medium | Medium | **T4 safety check.** First 30 min of T4 is a grep + count. If threshold breached, fall back to thin `DatCollectionAdapter : IDatReaderWriter` and document. Either path keeps T4 in its 2.5d budget. |
| `DatCollection` doesn't implement a method `ObjectMeshManager` calls | Medium | Medium | **T4 audit, fill the gap when found.** Add missing methods to `DatCollection` (we own it) rather than stub them. Bounded — at most a handful of methods. |
| `SixLabors.ImageSharp` shows up in the closure at T3 | Low | Low | **Verify-at-T3 + strip.** Grep T3 source on first pass; if found, replace with our existing byte-handling or BCnEncoder calls. |
| Visual regression we don't catch in side-by-side | Low | Medium | **Screenshot Holtburg + inn + dungeon BEFORE starting T3.** Compare after T7. Don't trust eyeballs alone. |
| Loss of `[indoor-upload]` diagnostic removes useful Phase 2 evidence | Low | Low | The diagnostic's findings are already documented in commit history and the audit. The block was a one-time probe; its job is done. |
| Hidden transitive WB deps we missed | Low | Low | Audit complete (33 files, ~7.7K LOC, fully bucketed). Build break at T7 would catch any miss. **Was Medium pre-audit — reduced to Low.** |
| User upstream-tracks WB for some reason | Low | Low | `references/WorldBuilder/` stays in-tree as read-reference. Re-sync diffs are manual ports (same as today). |

---

## 8. Out of scope (explicitly)

- **Re-porting from retail decomp** anywhere in the extracted code. We copy WB verbatim. If a retail-faithfulness audit is needed later, file a separate phase.
- **Performance optimization** of extracted code. Even if WB's `ObjectMeshManager` has a 30% improvement waiting in it, this phase ships it as-is.
- **API cleanup** of the extracted code beyond the dat-surface change at T4. If the constructor has 8 parameters and it's ugly, ugly it stays. Refactor in a follow-up.
- **Refactoring `WbMeshAdapter` itself.** Phase O drops the second reader; the adapter shape stays.
- **`tools/InspectCoatTex` or other tools that use the NuGet `Chorizite.DatReaderWriter`**. Those keep working — they use the NuGet `DatReaderWriter`, not the WB project reference.
- **Re-organizing the extracted namespace.** O-D11 picked `AcDream.Core.Rendering.Wb.*`; topic-based reorganization is a follow-up phase.

---

## 9. Open questions

All originally-open questions have been resolved by the O-T1 audit or this brainstorm:

1. **O-Q1 (thread-model):** CLOSED. Verified safe — adapters run render-thread only; WB's own code uses `ConcurrentDictionary` + locks as defense in depth. See O-T1 audit §6.
2. **O-Q2 (TerrainRenderManager):** CLOSED. Confirmed not reachable; we use our own `TerrainModernRenderer`. `LandSurfaceManager` also not reachable (we have our own port). Both dropped from extract list per O-D8.
3. **O-Q3 (namespace):** CLOSED. Adopted `AcDream.Core.Rendering.Wb.*` (option A) per O-D11.
4. **O-Q4 (Chorizite.DatReaderWriter NuGet):** CLOSED. Stays as NuGet — separate from WB project refs.
5. **O-Q5 (NEW — SixLabors.ImageSharp):** Deferred to T3. Verify reachability during extraction. Strip if found; document if not.

---

## 10. Naming + filing

- **Phase name:** O (letter remains).
- **Phase tagline:** "ONE thing touches the DATs."
- **Roadmap entry:** already in [`docs/plans/2026-04-11-roadmap.md`](../../plans/2026-04-11-roadmap.md) under "currently active". Move to "shipped" at T9.
- **Issue tracking:** filed as a Phase, not an issue (multi-commit, multi-day, infrastructural).

---

## 11. After Phase O ships

Things that become unblocked or cheaper:

- **Single-cache memory pressure budget.** Easier to size streaming radii, MSAA, anisotropic budget.
- **Audit a single dat-touching code path** instead of two when investigating bugs like the cell-resolution divergence the `[indoor-upload]` probe was built to investigate.
- **Future N.6+ rendering work** doesn't have to ask "is this WB's concern or ours?" — it's ours.
- **AC community-friendly architecture** — the "WB is for tools" criticism is addressed at the structural level.
- **A follow-up phase to refactor namespaces** from `AcDream.Core.Rendering.Wb.*` into topic-based (`Meshes.*`, `Textures.*`) becomes possible. Estimated 0.5d when scheduled.
