docs(perf): Phase N.6 slice 1 — implementation plan

Step-by-step plan for the two-commit slice: fix WbDrawDispatcher's gpu_us double-buffering bug (ring-of-3 query slots, read-before-overwrite, vendor-neutral) then capture the radius=12 baseline at Holtburg with the now-working diagnostic. Includes exact old_string/new_string Edit patterns for every code change, PowerShell launch + measurement procedure for the manual baseline, baseline doc template with explicit fill-in slots, and a per-criterion acceptance checklist. Output companion to docs/superpowers/specs/2026-05-11-phase-n6-slice1-design.md (commit 05d590c). Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
2026-05-11 11:12:26 +02:00 · 2026-05-11 11:12:26 +02:00 · a4931eeaa2
commit a4931eeaa2
parent 05d590cd54
1 changed files with 912 additions and 0 deletions
--- a/docs/superpowers/plans/2026-05-11-phase-n6-slice1.md
+++ b/docs/superpowers/plans/2026-05-11-phase-n6-slice1.md
@ -0,0 +1,912 @@
+# Phase N.6 slice 1 Implementation Plan
+
+> **For agentic workers:** REQUIRED SUB-SKILL: Use superpowers:subagent-driven-development (recommended) or superpowers:executing-plans to implement this plan task-by-task. Steps use checkbox (`- [ ]`) syntax for tracking.
+
+**Goal:** Fix the broken `gpu_us` diagnostic in `WbDrawDispatcher` (vendor-neutral OpenGL query ring) and produce one authoritative perf baseline document at Holtburg radius=12 so the next-phase decision (slice 2 vs C.1.5 vs Tier 2) is grounded in real numbers.
+
+**Architecture:** Two commits. Commit 1 changes only `WbDrawDispatcher.cs` — replaces the two `uint` GL query handles with ring-of-3 arrays and moves the result read to *before* the next frame overwrites the slot (read frame N-3's queries, then overwrite). Commit 2 adds an env-gated surface-format histogram dump in `TextureCache.cs`, captures the actual measurement, writes the baseline doc, and amends the roadmap entry. No new automated tests — the GPU-timing fix has no observable behavior in tests, and the dump path is env-gated diagnostic only; verification is manual launch-and-look.
+
+**Tech Stack:** C# / .NET 10, Silk.NET (OpenGL 4.3+), `dotnet build` / `dotnet test` from PowerShell, live ACE on `127.0.0.1:9000` for in-world verification.
+
+**Spec:** [docs/superpowers/specs/2026-05-11-phase-n6-slice1-design.md](../specs/2026-05-11-phase-n6-slice1-design.md) (committed at `05d590c`).
+
+---
+
+## File Structure
+
+| File | Action | Responsibility |
+|---|---|---|
+| [`src/AcDream.App/Rendering/Wb/WbDrawDispatcher.cs`](../../../src/AcDream.App/Rendering/Wb/WbDrawDispatcher.cs) | Modify | Replace 2 `uint` query handles with ring-of-3 arrays; move query result read to before next-frame overwrite. |
+| [`src/AcDream.App/Rendering/TextureCache.cs`](../../../src/AcDream.App/Rendering/TextureCache.cs) | Modify | Add upload-time dimension/format tracking + env-gated `TickSurfaceHistogramDumpIfEnabled()` method that fires once at frame 600. |
+| [`src/AcDream.App/Rendering/GameWindow.cs`](../../../src/AcDream.App/Rendering/GameWindow.cs) | Modify | Call `_textureCache.TickSurfaceHistogramDumpIfEnabled()` once per frame in `OnRender`. |
+| `docs/plans/2026-05-11-phase-n6-perf-baseline.md` | Create | Baseline measurement doc: setup, numbers at radii 4/8/12 (standstill + walking), surface histogram summary, conclusion paragraph recommending next phase. |
+| [`docs/plans/2026-04-11-roadmap.md`](../../plans/2026-04-11-roadmap.md) lines 690-705 | Modify | Amend N.6 entry to reflect the slice 1 / slice 2 split. |
+
+---
+
+## Task 1: GPU query ring buffering (commit 1)
+
+**Files:**
+- Modify: `src/AcDream.App/Rendering/Wb/WbDrawDispatcher.cs`
+
+The five edit zones are well-isolated by exact strings. Apply them in order — do NOT reorder; the build won't fail mid-way but the resulting code is easier to review if applied as documented.
+
+- [ ] **Step 1.1: Replace the field declarations (~line 155)**
+
+Use Edit to replace the existing field block:
+
+**old_string:**
+```csharp
+    private uint _gpuQueryOpaque;
+    private uint _gpuQueryTransparent;
+    private readonly long[] _gpuSamples = new long[256];   // microseconds
+    private int _gpuSampleCursor;
+    private bool _gpuQueriesInitialized;
+```
+
+**new_string:**
+```csharp
+    // GPU timing uses a ring of 3 query-pair slots so the read of frame N-3's
+    // result lands when the GPU has finished (~50ms after issue on a typical
+    // 60fps frame). Ring of 3 is the vendor-neutral choice: NVIDIA drivers with
+    // triple-buffering+vsync can queue ~3 frames ahead, AMD typically 1-2,
+    // Intel iGPUs vary. ResultAvailable is the safety guard if the GPU is
+    // still working when we try to read.
+    private const int GpuQueryRingDepth = 3;
+    private readonly uint[] _gpuQueryOpaque      = new uint[GpuQueryRingDepth];
+    private readonly uint[] _gpuQueryTransparent = new uint[GpuQueryRingDepth];
+    private int _gpuQueryFrameIndex;
+    private readonly long[] _gpuSamples = new long[256];   // microseconds
+    private int _gpuSampleCursor;
+    private bool _gpuQueriesInitialized;
+```
+
+- [ ] **Step 1.2: Replace the init block (~line 347)**
+
+**old_string:**
+```csharp
+        if (diag && !_gpuQueriesInitialized)
+        {
+            _gpuQueryOpaque      = _gl.GenQuery();
+            _gpuQueryTransparent = _gl.GenQuery();
+            _gpuQueriesInitialized = true;
+        }
+```
+
+**new_string:**
+```csharp
+        if (diag && !_gpuQueriesInitialized)
+        {
+            for (int i = 0; i < GpuQueryRingDepth; i++)
+            {
+                _gpuQueryOpaque[i]      = _gl.GenQuery();
+                _gpuQueryTransparent[i] = _gl.GenQuery();
+            }
+            _gpuQueriesInitialized = true;
+        }
+```
+
+- [ ] **Step 1.3: Insert the read-before-overwrite block + compute slot just before the opaque query begin (~line 774)**
+
+This step replaces the existing single-line `BeginQuery` for opaque with a block that first computes the slot, reads the slot's frame N-3 result (gated on having completed one ring), then issues the new query into the same slot.
+
+**old_string:**
+```csharp
+            _gl.BindBuffer(BufferTargetARB.DrawIndirectBuffer, _indirectBuffer);
+            if (diag && _gpuQueriesInitialized) _gl.BeginQuery(QueryTarget.TimeElapsed, _gpuQueryOpaque);
+```
+
+**new_string:**
+```csharp
+            _gl.BindBuffer(BufferTargetARB.DrawIndirectBuffer, _indirectBuffer);
+
+            // GPU timing: compute this frame's ring slot. We read frame N-3's
+            // result (the oldest data in the ring) before overwriting it with
+            // frame N's queries. See spec §3 Q1/Q2 + §4 in
+            // docs/superpowers/specs/2026-05-11-phase-n6-slice1-design.md.
+            int gpuQuerySlot = _gpuQueryFrameIndex % GpuQueryRingDepth;
+            if (_gpuQueriesInitialized && _gpuQueryFrameIndex >= GpuQueryRingDepth)
+            {
+                _gl.GetQueryObject(_gpuQueryOpaque[gpuQuerySlot], QueryObjectParameterName.ResultAvailable, out int avail);
+                if (avail != 0)
+                {
+                    _gl.GetQueryObject(_gpuQueryOpaque[gpuQuerySlot],      QueryObjectParameterName.Result, out ulong opaqueNs);
+                    _gl.GetQueryObject(_gpuQueryTransparent[gpuQuerySlot], QueryObjectParameterName.Result, out ulong transNs);
+                    long gpuUs = (long)((opaqueNs + transNs) / 1000UL);
+                    _gpuSamples[_gpuSampleCursor] = gpuUs;
+                    _gpuSampleCursor = (_gpuSampleCursor + 1) % _gpuSamples.Length;
+                }
+                // If avail==0 the sample is dropped silently. MedianMicros
+                // computes over the non-zero subset, so dropped samples don't
+                // poison the median.
+            }
+
+            if (diag && _gpuQueriesInitialized) _gl.BeginQuery(QueryTarget.TimeElapsed, _gpuQueryOpaque[gpuQuerySlot]);
+```
+
+- [ ] **Step 1.4: Update the transparent query begin to use the same slot (~line 823)**
+
+**old_string:**
+```csharp
+            if (diag && _gpuQueriesInitialized) _gl.BeginQuery(QueryTarget.TimeElapsed, _gpuQueryTransparent);
+```
+
+**new_string:**
+```csharp
+            if (diag && _gpuQueriesInitialized) _gl.BeginQuery(QueryTarget.TimeElapsed, _gpuQueryTransparent[gpuQuerySlot]);
+```
+
+- [ ] **Step 1.5: Replace the buggy in-frame read block + increment frame counter (~line 849)**
+
+**old_string:**
+```csharp
+            // Read GPU samples non-blocking; the result for the previous frame's
+            // queries should be ready by now. If not, drop the sample (don't stall
+            // the CPU waiting for the GPU).
+            if (_gpuQueriesInitialized)
+            {
+                _gl.GetQueryObject(_gpuQueryOpaque, QueryObjectParameterName.ResultAvailable, out int avail);
+                if (avail != 0)
+                {
+                    _gl.GetQueryObject(_gpuQueryOpaque, QueryObjectParameterName.Result, out ulong opaqueNs);
+                    _gl.GetQueryObject(_gpuQueryTransparent, QueryObjectParameterName.Result, out ulong transNs);
+                    long gpuUs = (long)((opaqueNs + transNs) / 1000UL);
+                    _gpuSamples[_gpuSampleCursor] = gpuUs;
+                    _gpuSampleCursor = (_gpuSampleCursor + 1) % _gpuSamples.Length;
+                }
+            }
+
+            _drawsIssued     += _opaqueDrawCount + _transparentDrawCount;
+```
+
+**new_string:**
+```csharp
+            // GPU sample read happens BEFORE issuing the next frame's queries
+            // (see step 1.3 above). Increment the frame counter here so the
+            // next call computes a fresh slot.
+            if (_gpuQueriesInitialized) _gpuQueryFrameIndex++;
+
+            _drawsIssued     += _opaqueDrawCount + _transparentDrawCount;
+```
+
+- [ ] **Step 1.6: Update Dispose to delete the full ring (~line 1140)**
+
+**old_string:**
+```csharp
+        if (_gpuQueriesInitialized)
+        {
+            _gl.DeleteQuery(_gpuQueryOpaque);
+            _gl.DeleteQuery(_gpuQueryTransparent);
+        }
+```
+
+**new_string:**
+```csharp
+        if (_gpuQueriesInitialized)
+        {
+            for (int i = 0; i < GpuQueryRingDepth; i++)
+            {
+                _gl.DeleteQuery(_gpuQueryOpaque[i]);
+                _gl.DeleteQuery(_gpuQueryTransparent[i]);
+            }
+        }
+```
+
+- [ ] **Step 1.7: Build**
+
+Run from the worktree root:
+
+```powershell
+dotnet build
+```
+
+Expected: build succeeds with no new warnings or errors. If the build fails, the most likely cause is a missed string in one of the steps above — re-grep `_gpuQueryOpaque` and `_gpuQueryTransparent` in `WbDrawDispatcher.cs` and confirm every reference uses the array-indexed form `[gpuQuerySlot]` or `[i]`.
+
+- [ ] **Step 1.8: Run the test suite**
+
+```powershell
+dotnet test --no-build
+```
+
+Expected: same pass/fail baseline as before the change (~1688 passing, ~8 pre-existing physics/input failures unchanged). No new failures.
+
+- [ ] **Step 1.9: Manual verification — launch live and confirm `gpu_us` reports non-zero**
+
+```powershell
+$env:ACDREAM_DAT_DIR   = "$env:USERPROFILE\Documents\Asheron's Call"
+$env:ACDREAM_LIVE      = "1"
+$env:ACDREAM_TEST_HOST = "127.0.0.1"
+$env:ACDREAM_TEST_PORT = "9000"
+$env:ACDREAM_TEST_USER = "testaccount"
+$env:ACDREAM_TEST_PASS = "testpassword"
+$env:ACDREAM_WB_DIAG   = "1"
+dotnet run --project src\AcDream.App\AcDream.App.csproj --no-build -c Debug 2>&1 | Tee-Object -FilePath "task1-verify.log"
+```
+
+In-world: walk Holtburg for ~30 seconds. Close the window when done.
+
+Verification check on `task1-verify.log`:
+
+```powershell
+Select-String -Path task1-verify.log -Pattern "\[WB-DIAG\]" | Select-Object -Last 5
+```
+
+Expected output: at least one `[WB-DIAG]` line where `gpu_us=Xm/Yp95` has X > 0 (typically tens to low-hundreds of microseconds at radius=4-12 on a modern GPU). If `gpu_us=0m/0p95` persists for the entire run, the fix didn't take — check whether the build actually rebuilt (try `dotnet build -c Debug` then re-launch).
+
+Also confirm: no visible regression in the client. Entities render, animations play, sky cycles. Close the client cleanly.
+
+- [ ] **Step 1.10: Commit**
+
+```powershell
+git add src/AcDream.App/Rendering/Wb/WbDrawDispatcher.cs
+git commit -m @'
+feat(perf): Phase N.6 slice 1 — fix gpu_us double-buffering in WbDrawDispatcher
+
+The dispatcher's GPU TimeElapsed queries were polled in the same frame
+as the indirect draw, so glGetQueryObject(ResultAvailable) always
+returned 0 and gpu_us in [WB-DIAG] was stuck at 0m/0p95.
+
+Replace the 2 single-handle queries with ring-of-3 arrays and move the
+result read to BEFORE issuing the next frame's queries into the same
+slot — at frame N we read slot N%3 which holds frame N-3's queries
+(oldest in the ring, ~50ms old at 60fps and definitely done across all
+desktop GL drivers). Vendor-neutral: AMD/NVIDIA/Intel desktop GL all
+work without driver-specific code.
+
+No new tests — the change is purely a diagnostic readout fix, no
+observable behavior in the rendering path. Manual verification:
+[WB-DIAG] now reports non-zero gpu_us at Holtburg radius=12.
+
+Spec: docs/superpowers/specs/2026-05-11-phase-n6-slice1-design.md (§4).
+
+Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
+'@
+git status
+```
+
+Expected: clean working tree after commit. Note the new commit SHA — needed for the baseline doc's "measured against" reference.
+
+---
+
+## Task 2: Surface-format histogram dump path (part of commit 2 setup)
+
+**Files:**
+- Modify: `src/AcDream.App/Rendering/TextureCache.cs`
+- Modify: `src/AcDream.App/Rendering/GameWindow.cs`
+
+This task adds the env-gated one-shot dump infrastructure. It does NOT commit — the commit happens in Task 4 after the baseline document is also ready.
+
+- [ ] **Step 2.1: Add upload-time metadata tracking in `TextureCache.cs`**
+
+Add a new private dictionary that records `(width, height, formatLabel)` keyed by GL texture name. This lets `DumpSurfaceHistogram` emit dimension/format data without re-querying GL.
+
+Use Edit to insert the field right after the existing bindless cache fields (~line 41, just after `_bindlessByPalette`):
+
+**old_string:**
+```csharp
+    private readonly Dictionary<(uint surfaceId, uint origTexOverride, ulong paletteHash), (uint Name, ulong Handle)> _bindlessByPalette = new();
+
+    public TextureCache(GL gl, DatCollection dats, Wb.BindlessSupport? bindless = null)
+```
+
+**new_string:**
+```csharp
+    private readonly Dictionary<(uint surfaceId, uint origTexOverride, ulong paletteHash), (uint Name, ulong Handle)> _bindlessByPalette = new();
+
+    // Phase N.6 slice 1 (2026-05-11): per-upload metadata for the
+    // ACDREAM_DUMP_SURFACES=1 histogram dump path. Populated at upload
+    // time so the dump method doesn't have to query GL state. Keyed by
+    // GL texture name (same key used in cache value tuples). Format
+    // label is "RGBA8_DECODED" for the post-decode upload (all uploads
+    // currently land as RGBA8 regardless of source format).
+    private readonly Dictionary<uint, (int Width, int Height, string Format)> _uploadMetadata = new();
+
+    // Frame counter for the one-shot ACDREAM_DUMP_SURFACES=1 trigger.
+    // Increments per Tick call; fires the dump once at frame index 600
+    // and never again for the session. See spec §5.
+    private int _dumpFrameCounter;
+    private bool _surfaceHistogramAlreadyDumped;
+
+    public TextureCache(GL gl, DatCollection dats, Wb.BindlessSupport? bindless = null)
+```
+
+- [ ] **Step 2.2: Find the `UploadRgba8AsLayer1Array` method and record metadata there**
+
+Locate the method using Grep:
+
+```
+pattern: "UploadRgba8AsLayer1Array"
+path: src/AcDream.App/Rendering/TextureCache.cs
+output_mode: content
+-n: true
+```
+
+Read the method body (typically ~30-50 lines) to find the exact `return name;` line. The decoded texture has `decoded.Width`, `decoded.Height`, and `decoded.Rgba8` available.
+
+For each `return name;` in `UploadRgba8AsLayer1Array(DecodedTexture decoded)`, insert this line immediately before it:
+
+```csharp
+        _uploadMetadata[name] = (decoded.Width, decoded.Height, "RGBA8_DECODED");
+```
+
+If the method has only one `return name;` near its end, that's a single Edit. Use the surrounding 2-3 lines of context in `old_string` to make the Edit unique.
+
+- [ ] **Step 2.3: Also record metadata in the legacy `UploadRgba8` (non-bindless) path**
+
+Locate the method:
+
+```
+pattern: "private uint UploadRgba8\b"
+path: src/AcDream.App/Rendering/TextureCache.cs
+output_mode: content
+-n: true
+```
+
+Apply the same `_uploadMetadata[name] = (decoded.Width, decoded.Height, "RGBA8_DECODED");` insertion before each `return name;` in `UploadRgba8(DecodedTexture decoded)`. This ensures the dump captures both legacy and modern uploads.
+
+- [ ] **Step 2.4: Add the `TickSurfaceHistogramDumpIfEnabled` public method to `TextureCache.cs`**
+
+Locate `HashPaletteOverride` using Grep:
+
+```
+pattern: "internal static ulong HashPaletteOverride"
+path: src/AcDream.App/Rendering/TextureCache.cs
+output_mode: content
+-n: true
+-A: 20
+```
+
+Identify its closing brace. Use Edit with surrounding context to insert the new methods immediately after.
+
+**old_string:** (the last few lines of `HashPaletteOverride`):
+```csharp
+        foreach (var sp in p.SubPalettes)
+        {
+            h = (h ^ sp.SubPaletteId) * prime;
+            h = (h ^ sp.Offset) * prime;
+            h = (h ^ sp.Length) * prime;
+        }
+        return h;
+    }
+```
+
+**new_string:**
+```csharp
+        foreach (var sp in p.SubPalettes)
+        {
+            h = (h ^ sp.SubPaletteId) * prime;
+            h = (h ^ sp.Offset) * prime;
+            h = (h ^ sp.Length) * prime;
+        }
+        return h;
+    }
+
+    /// <summary>
+    /// Phase N.6 slice 1: one-shot surface-format histogram dump for the
+    /// atlas-opportunity audit. Activated by ACDREAM_DUMP_SURFACES=1; fires
+    /// once at frame 600 of the session (~10s at 60fps, ~3s at 200fps —
+    /// both well past streaming settle at radius≤12). Output goes to
+    /// %LOCALAPPDATA%\acdream\n6-surfaces.txt. Zero cost when off.
+    /// See spec §5 in docs/superpowers/specs/2026-05-11-phase-n6-slice1-design.md.
+    /// </summary>
+    public void TickSurfaceHistogramDumpIfEnabled()
+    {
+        if (_surfaceHistogramAlreadyDumped) return;
+        if (!string.Equals(Environment.GetEnvironmentVariable("ACDREAM_DUMP_SURFACES"), "1", StringComparison.Ordinal)) return;
+        _dumpFrameCounter++;
+        if (_dumpFrameCounter < 600) return;
+
+        DumpSurfaceHistogram();
+        _surfaceHistogramAlreadyDumped = true;
+    }
+
+    private void DumpSurfaceHistogram()
+    {
+        var localAppData = Environment.GetFolderPath(Environment.SpecialFolder.LocalApplicationData);
+        var outDir = System.IO.Path.Combine(localAppData, "acdream");
+        System.IO.Directory.CreateDirectory(outDir);
+        var outPath = System.IO.Path.Combine(outDir, "n6-surfaces.txt");
+
+        var sb = new System.Text.StringBuilder();
+        sb.AppendLine($"# acdream surface-format histogram — generated {DateTime.UtcNow:yyyy-MM-ddTHH:mm:ssZ}");
+        sb.AppendLine("# Per-entry: surfaceId(hex), width, height, format, byteCount");
+        sb.AppendLine();
+
+        // Walk every cached entry across the 6 caches, dedupe by GL name.
+        var seen = new HashSet<uint>();
+        long totalBytes = 0;
+        var bucketsByDim = new Dictionary<(int W, int H), int>();
+        var bucketsByFormat = new Dictionary<string, int>();
+        var bucketsByTriple = new Dictionary<(int W, int H, string F), int>();
+
+        void Emit(uint surfaceId, uint name)
+        {
+            if (!seen.Add(name)) return;
+            if (!_uploadMetadata.TryGetValue(name, out var meta)) return;
+            int bytes = meta.Width * meta.Height * 4;
+            totalBytes += bytes;
+            sb.AppendLine($"0x{surfaceId:X8}, {meta.Width}, {meta.Height}, {meta.Format}, {bytes}");
+
+            var dimKey = (meta.Width, meta.Height);
+            bucketsByDim[dimKey] = bucketsByDim.GetValueOrDefault(dimKey) + 1;
+            bucketsByFormat[meta.Format] = bucketsByFormat.GetValueOrDefault(meta.Format) + 1;
+            var tripleKey = (meta.Width, meta.Height, meta.Format);
+            bucketsByTriple[tripleKey] = bucketsByTriple.GetValueOrDefault(tripleKey) + 1;
+        }
+
+        foreach (var kv in _handlesBySurfaceId)         Emit(kv.Key, kv.Value);
+        foreach (var kv in _handlesByOverridden)        Emit(kv.Key.surfaceId, kv.Value);
+        foreach (var kv in _handlesByPalette)           Emit(kv.Key.surfaceId, kv.Value);
+        foreach (var kv in _bindlessBySurfaceId)        Emit(kv.Key, kv.Value.Name);
+        foreach (var kv in _bindlessByOverridden)       Emit(kv.Key.surfaceId, kv.Value.Name);
+        foreach (var kv in _bindlessByPalette)          Emit(kv.Key.surfaceId, kv.Value.Name);
+
+        sb.AppendLine();
+        sb.AppendLine("# Rollups");
+        sb.AppendLine($"# Total unique GL textures: {seen.Count}");
+        sb.AppendLine($"# Total bytes (sum of W*H*4): {totalBytes}");
+
+        sb.AppendLine("# Top 10 (W,H) dimension buckets:");
+        foreach (var kv in bucketsByDim.OrderByDescending(kv => kv.Value).Take(10))
+            sb.AppendLine($"#   {kv.Key.W}x{kv.Key.H}: {kv.Value}");
+
+        sb.AppendLine("# Format buckets:");
+        foreach (var kv in bucketsByFormat.OrderByDescending(kv => kv.Value))
+            sb.AppendLine($"#   {kv.Key}: {kv.Value}");
+
+        sb.AppendLine("# Top 10 (W,H,format) triples — atlas-opportunity input:");
+        foreach (var kv in bucketsByTriple.OrderByDescending(kv => kv.Value).Take(10))
+            sb.AppendLine($"#   {kv.Key.W}x{kv.Key.H} {kv.Key.F}: {kv.Value}");
+
+        System.IO.File.WriteAllText(outPath, sb.ToString());
+        Console.WriteLine($"[N6-DUMP] Surface histogram written to {outPath} ({seen.Count} textures, {totalBytes} bytes)");
+    }
+```
+
+- [ ] **Step 2.5: Confirm `using System.Linq;` is present in `TextureCache.cs`**
+
+Read the file's `using` section (top of file). If `using System.Linq;` is NOT present, add it. The `OrderByDescending` and `Take` calls in `DumpSurfaceHistogram` need it.
+
+Pattern:
+```
+pattern: "^using System\.Linq"
+path: src/AcDream.App/Rendering/TextureCache.cs
+output_mode: count
+```
+
+If count is 0, add `using System.Linq;` in alphabetical order with the other usings at the top of the file.
+
+- [ ] **Step 2.6: Add the per-frame call site in `GameWindow.cs`**
+
+Find a stable insertion point near the top of `OnRender` (starts at line 6288). Use Grep:
+
+```
+pattern: "_gl!\.Clear\("
+path: src/AcDream.App/Rendering/GameWindow.cs
+output_mode: content
+-n: true
+-A: 3
+```
+
+This finds the `Clear` call(s) in or near `OnRender`. The first one after line 6288 is where you want to insert. Read 5 lines of context around it, then Edit to insert the dump tick on the line immediately after the `Clear` call returns:
+
+The insertion (one Edit):
+
+**old_string:** (find the `Clear` call in `OnRender` and capture 1-2 lines of its context — varies; common pattern is `_gl!.Clear(ClearBufferMask.ColorBufferBit | ClearBufferMask.DepthBufferBit);` followed by the next line of `OnRender` work).
+
+**new_string:** the same `Clear` call followed by:
+```csharp
+
+        // Phase N.6 slice 1: one-shot surface-format histogram dump under
+        // ACDREAM_DUMP_SURFACES=1. Zero cost when off.
+        _textureCache?.TickSurfaceHistogramDumpIfEnabled();
+```
+
+If `OnRender` has multiple `Clear` calls, place the tick after the first one inside the method body. The call must run exactly once per frame, before any rendering work — placing it right after `Clear` accomplishes both.
+
+- [ ] **Step 2.7: Build**
+
+```powershell
+dotnet build
+```
+
+Expected: build succeeds with no new warnings. If a "name 'OrderByDescending' does not exist in current context" error appears, Step 2.5 was missed — add the `using System.Linq;` and rebuild.
+
+- [ ] **Step 2.8: Run the test suite**
+
+```powershell
+dotnet test --no-build
+```
+
+Expected: same pass/fail baseline (~1688 passing, ~8 pre-existing failures). No new failures.
+
+- [ ] **Step 2.9: Manual verification — confirm the dump file appears**
+
+Launch with the dump env var on:
+
+```powershell
+$env:ACDREAM_DUMP_SURFACES = "1"
+$env:ACDREAM_WB_DIAG = "1"
+# Other env vars same as Task 1 Step 1.9
+dotnet run --project src\AcDream.App\AcDream.App.csproj --no-build -c Debug 2>&1 | Tee-Object -FilePath "task2-verify.log"
+```
+
+Wait ~15 seconds after the window appears, then close it. Check the file:
+
+```powershell
+Get-Content "$env:LOCALAPPDATA\acdream\n6-surfaces.txt" | Select-Object -First 30
+```
+
+Expected: a non-empty file with the header, per-entry rows, and rollup sections. Also confirm one `[N6-DUMP] Surface histogram written to ...` line in `task2-verify.log` (just before window close).
+
+If the file is empty or missing:
+- Check the launch log for the `[N6-DUMP]` line.
+- If it's not there, `_dumpFrameCounter` didn't reach 600 — the user closed too early. Re-run and wait longer.
+- If it's there but the file lookup fails, the path output in the log should show what was actually written; investigate that path.
+
+**Do not commit yet.** Continue to Task 3.
+
+---
+
+## Task 3: Capture baseline measurements
+
+**Files:**
+- Create: `docs/plans/2026-05-11-phase-n6-perf-baseline.md` (final content lands in Task 4 — this task just collects the numbers).
+
+This is the manual measurement task. Each step launches the client, runs a specific scenario, and captures the diagnostic output. Save each log separately for the final write-up. Total expected time: ~30-45 min.
+
+Setup once per session:
+```powershell
+$env:ACDREAM_DAT_DIR   = "$env:USERPROFILE\Documents\Asheron's Call"
+$env:ACDREAM_LIVE      = "1"
+$env:ACDREAM_TEST_HOST = "127.0.0.1"
+$env:ACDREAM_TEST_PORT = "9000"
+$env:ACDREAM_TEST_USER = "testaccount"
+$env:ACDREAM_TEST_PASS = "testpassword"
+$env:ACDREAM_WB_DIAG   = "1"
+```
+
+For each measurement run, set `ACDREAM_STREAM_RADIUS` before launch. Use the `QualityPreset=High` default (no overrides). All runs at Holtburg with `+Acdream` at clear midday (cycle weather with F10 → Clear, time with F7 → Noon).
+
+Per run, after ~30 seconds at the target condition, close the window and grep the log for the last 3 `[WB-DIAG]` lines — those have the steady-state numbers.
+
+- [ ] **Step 3.1: Capture radius=4 standstill**
+
+```powershell
+$env:ACDREAM_STREAM_RADIUS = "4"
+dotnet run --project src\AcDream.App\AcDream.App.csproj --no-build -c Debug 2>&1 | Tee-Object -FilePath "baseline-r4-stand.log"
+```
+
+In-world: enter world, do not move, hold position for 30 seconds. Close.
+
+```powershell
+Select-String -Path baseline-r4-stand.log -Pattern "\[WB-DIAG\]" | Select-Object -Last 3
+```
+
+Record from the median of the last 3 lines: `cpu_us`, `gpu_us`, `entSeen`, `entDrawn`, `groups`. Also note the window-title FPS shown during the test.
+
+- [ ] **Step 3.2: Capture radius=4 walking**
+
+```powershell
+$env:ACDREAM_STREAM_RADIUS = "4"
+dotnet run --project src\AcDream.App\AcDream.App.csproj --no-build -c Debug 2>&1 | Tee-Object -FilePath "baseline-r4-walk.log"
+```
+
+In-world: enter world, Tab to player mode, walk N→E→S→W across one landblock over ~30 seconds. Close.
+
+Capture same numbers as 3.1.
+
+- [ ] **Step 3.3: Capture radius=8 standstill**
+
+```powershell
+$env:ACDREAM_STREAM_RADIUS = "8"
+dotnet run --project src\AcDream.App\AcDream.App.csproj --no-build -c Debug 2>&1 | Tee-Object -FilePath "baseline-r8-stand.log"
+```
+
+Same procedure as 3.1. Wait ~40 seconds before recording (streaming takes longer to settle).
+
+- [ ] **Step 3.4: Capture radius=8 walking**
+
+```powershell
+$env:ACDREAM_STREAM_RADIUS = "8"
+dotnet run --project src\AcDream.App\AcDream.App.csproj --no-build -c Debug 2>&1 | Tee-Object -FilePath "baseline-r8-walk.log"
+```
+
+Same procedure as 3.2.
+
+- [ ] **Step 3.5: Capture radius=12 standstill**
+
+```powershell
+$env:ACDREAM_STREAM_RADIUS = "12"
+dotnet run --project src\AcDream.App\AcDream.App.csproj --no-build -c Debug 2>&1 | Tee-Object -FilePath "baseline-r12-stand.log"
+```
+
+Same procedure as 3.1. Wait ~60 seconds before recording. This is the headline measurement — pay attention to whether `gpu_us` p95 is well below 16.6 ms (60 fps target) or pushing it.
+
+- [ ] **Step 3.6: Capture radius=12 walking**
+
+```powershell
+$env:ACDREAM_STREAM_RADIUS = "12"
+dotnet run --project src\AcDream.App\AcDream.App.csproj --no-build -c Debug 2>&1 | Tee-Object -FilePath "baseline-r12-walk.log"
+```
+
+Same procedure as 3.2 (walking across one landblock, ~30 seconds of motion within the 60s+ window).
+
+- [ ] **Step 3.7: Capture the surface histogram**
+
+```powershell
+$env:ACDREAM_STREAM_RADIUS = "12"
+$env:ACDREAM_DUMP_SURFACES = "1"
+dotnet run --project src\AcDream.App\AcDream.App.csproj --no-build -c Debug 2>&1 | Tee-Object -FilePath "baseline-surfaces.log"
+```
+
+In-world: enter world at Holtburg, do nothing for ~30 seconds (let the dump fire at frame 600). Close. Copy the file:
+
+```powershell
+Copy-Item "$env:LOCALAPPDATA\acdream\n6-surfaces.txt" -Destination "baseline-surfaces.txt"
+```
+
+Inspect:
+```powershell
+Get-Content baseline-surfaces.txt | Select-Object -Last 40
+```
+
+Record the rollup section (total textures, total bytes, top 10 dimension buckets, format distribution, top 10 (W,H,format) triples).
+
+- [ ] **Step 3.8: Clean up the env vars and the local app data dump**
+
+```powershell
+Remove-Item Env:\ACDREAM_DUMP_SURFACES -ErrorAction SilentlyContinue
+Remove-Item Env:\ACDREAM_STREAM_RADIUS -ErrorAction SilentlyContinue
+# Optional: clean up the source file so a future re-measurement isn't confused by stale data
+Remove-Item "$env:LOCALAPPDATA\acdream\n6-surfaces.txt" -ErrorAction SilentlyContinue
+```
+
+All log files (`baseline-r*-*.log`, `baseline-surfaces.log`, `baseline-surfaces.txt`) remain in the worktree root for Task 4. They will NOT be committed — they're scratch.
+
+---
+
+## Task 4: Write baseline doc + amend roadmap + ship commit 2
+
+**Files:**
+- Create: `docs/plans/2026-05-11-phase-n6-perf-baseline.md`
+- Modify: `docs/plans/2026-04-11-roadmap.md` lines 690-705
+
+- [ ] **Step 4.1: Write the baseline document**
+
+Use Write to create `docs/plans/2026-05-11-phase-n6-perf-baseline.md` with this content (substitute real numbers from Task 3 captures into every `<n>` and `<pct>` placeholder; do NOT leave any unfilled):
+
+```markdown
+# Phase N.6 slice 1 — perf baseline at Holtburg
+
+**Created:** 2026-05-11.
+**Spec:** [docs/superpowers/specs/2026-05-11-phase-n6-slice1-design.md](../superpowers/specs/2026-05-11-phase-n6-slice1-design.md)
+**Measured against commit:** <commit SHA from Task 1.10>
+**Purpose:** Capture authoritative CPU+GPU dispatch numbers so the next-phase decision (slice 2 vs C.1.5 vs Tier 2) rests on real data.
+
+---
+
+## §1. Setup
+
+- **Hardware:** Radeon RX 9070 XT
+- **Resolution:** 1440p (2560×1440)
+- **Quality preset:** High (default)
+- **Connection:** live ACE at `127.0.0.1:9000`
+- **Character:** `+Acdream` at Holtburg
+- **Sky / time:** clear midday (F7 → Noon, F10 → Clear)
+- **Build:** Debug
+- **Date measured:** 2026-05-11
+- **Environment overrides:** `ACDREAM_WB_DIAG=1`, `ACDREAM_STREAM_RADIUS=<per-run>`
+
+## §2. Dispatch CPU / GPU numbers
+
+Each cell records the median of the last 3 `[WB-DIAG]` lines from a ~30s stable window. `entSeen / entDrawn / groups` are also from those lines. FPS read from the window title.
+
+| Radius | Motion | cpu_us median | cpu_us p95 | gpu_us median | gpu_us p95 | FPS | entSeen | entDrawn | groups |
+|---|---|---|---|---|---|---|---|---|---|
+| 4 | standstill | <n> | <n> | <n> | <n> | <n> | <n> | <n> | <n> |
+| 4 | walking    | <n> | <n> | <n> | <n> | <n> | <n> | <n> | <n> |
+| 8 | standstill | <n> | <n> | <n> | <n> | <n> | <n> | <n> | <n> |
+| 8 | walking    | <n> | <n> | <n> | <n> | <n> | <n> | <n> | <n> |
+| 12| standstill | <n> | <n> | <n> | <n> | <n> | <n> | <n> | <n> |
+| 12| walking    | <n> | <n> | <n> | <n> | <n> | <n> | <n> | <n> |
+
+## §3. Surface-format histogram
+
+From `ACDREAM_DUMP_SURFACES=1` at radius=12, ~30s after enter-world.
+
+- **Total unique GL textures:** <n>
+- **Total bytes (sum of W*H*4):** <n>
+- **Top 10 (W, H) dimension buckets:**
+  - `<W>x<H>`: <count>
+  - ... (paste from baseline-surfaces.txt rollup)
+- **Format distribution:**
+  - `<format>`: <count>
+- **Top 10 (W, H, format) triples — atlas-opportunity input:**
+  - `<W>x<H> <format>`: <count>
+  - ...
+
+**Atlas-opportunity score:** <pct>% of surfaces fall into the top-3 (W, H, format) triples. (A score >30% means atlas consolidation could meaningfully reduce sampler switches + memory overhead; <15% means scattered content and atlas is not worth the slice-2 effort.)
+
+## §4. Conclusion + next-phase recommendation
+
+<Opinionated paragraph addressing:
+ 1. Is the entity dispatcher CPU-bound or GPU-bound at radius=12?
+    - Compare cpu_us p95 vs gpu_us p95. The larger one is the bottleneck.
+ 2. Does gpu_us p95 leave headroom at 60 fps target (16.6 ms / 16600 µs)?
+    - If gpu_us p95 < 8000 µs: comfortable headroom.
+    - If gpu_us p95 < 14000 µs: tight but OK.
+    - If gpu_us p95 >= 14000 µs: GPU-saturated, persistent-mapped buffers and compute cull help.
+ 3. Does the atlas score justify slice-2 atlas work?
+ 4. Given (1)-(3), which is the right next phase?
+    - CPU-bound + low atlas score: pivot to C.1.5 (visible content, perf already comfortable).
+    - GPU-bound + high atlas score: do N.6 slice 2 (atlas + persistent buffers).
+    - Either-bound + headroom + low atlas score: do C.1.5 first.
+    - GPU saturated + need for more headroom: escalate to Tier 2.>
+
+## §5. Raw logs
+
+Scratch logs from this measurement run (not committed):
+- `baseline-r4-stand.log`, `baseline-r4-walk.log`
+- `baseline-r8-stand.log`, `baseline-r8-walk.log`
+- `baseline-r12-stand.log`, `baseline-r12-walk.log`
+- `baseline-surfaces.log`, `baseline-surfaces.txt`
+```
+
+Fill in every `<n>` and `<pct>` and the conclusion paragraph with the real values from Task 3. **Do NOT leave any `<n>` placeholders.** If a measurement is missing, re-run that step from Task 3 before continuing.
+
+- [ ] **Step 4.2: Read the current roadmap N.6 entry**
+
+```
+Read offset 685, limit 25 from docs/plans/2026-04-11-roadmap.md
+```
+
+Confirm the bullet starts with `- **N.6 — Perf polish.** **Planned (post-A.5 polish takes priority).**` and ends with `Plan + spec written when work begins. **Estimate: 1-2 weeks.**`. Capture the exact text verbatim for Step 4.3's `old_string`.
+
+- [ ] **Step 4.3: Amend the roadmap entry**
+
+Use Edit. The change splits N.6 into slice 1 (shipping with this commit) and slice 2 (deferred until after C.1.5).
+
+**old_string:** the exact N.6 bullet copied from the Read in Step 4.2.
+
+**new_string:**
+```markdown
+- **N.6 slice 1 — GPU timing fix + radius=12 perf baseline.** **SHIPPED 2026-05-11.**
+  Fixed the gpu_us double-buffering bug in `WbDrawDispatcher` (ring-of-3
+  query slots, read-before-overwrite, vendor-neutral across AMD/NVIDIA/Intel
+  desktop GL). Added env-gated surface-format histogram dump in `TextureCache`
+  for atlas-opportunity audit. Captured authoritative baseline at Holtburg
+  radii 4 / 8 / 12 (standstill + walking) with the now-working `gpu_us`
+  diagnostic. Plan + spec at `docs/superpowers/{specs,plans}/2026-05-11-phase-n6-slice1-*.md`.
+  Baseline numbers + next-phase recommendation at
+  [docs/plans/2026-05-11-phase-n6-perf-baseline.md](2026-05-11-phase-n6-perf-baseline.md).
+- **N.6 slice 2 — Perf polish cleanup.** **Planned — deferred until after C.1.5
+  (PES emitter wiring) per the baseline doc's recommendation.** Builds on
+  slice 1's measurement. Scope: retire the legacy `Texture2D`/`sampler2D` path
+  in `TextureCache` (currently kept for Sky + Debug + particle paths now that
+  Terrain has migrated); delete orphan `mesh.frag` (verify zero callers post-N.5
+  amendment); decide bindless-everywhere vs legacy-island for the remaining
+  `sampler2D` consumers; conditionally adopt WB atlas if the slice-1 histogram
+  shows a real opportunity; conditionally adopt persistent-mapped buffers if
+  the slice-1 baseline shows `BufferSubData` as a hot spot; GPU compute culling
+  remains out-of-scope (that's Tier 3 of the perf-tiers roadmap, gated on
+  Tier 2 first). Plan + spec written when work begins. **Estimate: 1-2 weeks
+  once C.1.5 lands.**
+```
+
+- [ ] **Step 4.4: Build (sanity check — only docs touched, but be safe)**
+
+```powershell
+dotnet build
+```
+
+Expected: build succeeds. (No code touched in Task 4; this just confirms nothing was accidentally edited in src/.)
+
+- [ ] **Step 4.5: Commit 2**
+
+```powershell
+git add src/AcDream.App/Rendering/TextureCache.cs `
+        src/AcDream.App/Rendering/GameWindow.cs `
+        docs/plans/2026-05-11-phase-n6-perf-baseline.md `
+        docs/plans/2026-04-11-roadmap.md
+git commit -m @'
+docs(perf): Phase N.6 slice 1 — radius=12 baseline + surface dump path
+
+Capture authoritative CPU+GPU dispatch numbers at Holtburg with the
+gpu_us diagnostic now working (commit <prev SHA from Task 1.10>). Three
+radii (4/8/12) × two motion modes (standstill/walking) + a surface-format
+histogram from ACDREAM_DUMP_SURFACES=1.
+
+Adds env-gated one-shot dump path (TextureCache.TickSurfaceHistogramDumpIfEnabled,
+called from GameWindow.OnRender) that fires once at frame 600 of the
+session — zero cost when off, writes to %LOCALAPPDATA%\acdream\n6-surfaces.txt.
+
+Baseline document at docs/plans/2026-05-11-phase-n6-perf-baseline.md
+closes with a recommendation paragraph for the next phase. Roadmap entry
+amended to reflect the slice 1 / slice 2 split.
+
+Spec: docs/superpowers/specs/2026-05-11-phase-n6-slice1-design.md (§5, §6).
+
+Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
+'@
+git status
+```
+
+Expected: clean working tree.
+
+- [ ] **Step 4.6: Final sanity sweep**
+
+```powershell
+git log -3 --oneline
+```
+
+Expected: two new commits from this slice (the GPU timing fix from Task 1.10, then this docs/perf commit), under the spec commit `05d590c`.
+
+Also confirm the scratch baseline-r*.log and baseline-surfaces.* files are still NOT in the commit (they were not staged):
+
+```powershell
+git status
+```
+
+Expected: clean working tree. If the scratch logs show as untracked but uncommitted, that's fine — they can be deleted manually:
+
+```powershell
+Remove-Item baseline-r*.log, baseline-surfaces.log, baseline-surfaces.txt, task1-verify.log, task2-verify.log -ErrorAction SilentlyContinue
+```
+
+---
+
+## Acceptance check (spec §9)
+
+After Task 4 commits, walk through the spec's acceptance criteria and confirm each one. This is a paper-walk, not a re-run — the steps above produce the conditions.
+
+- [ ] **A1: `[WB-DIAG]` reports non-zero `gpu_us` at radius=12.**
+  Verified in Task 1.9 (initial check) and Task 3.5-3.6 (full baseline run). Confirm by re-grepping `baseline-r12-stand.log`:
+  ```powershell
+  Select-String -Path baseline-r12-stand.log -Pattern "gpu_us=[1-9]"
+  ```
+  Should return at least one line.
+
+- [ ] **A2: Vendor-neutral.** No `GL_*_NV` or `GL_*_AMD` or `GL_*_INTEL` extension references in the change. Re-grep:
+  ```powershell
+  Select-String -Path src/AcDream.App/Rendering/Wb/WbDrawDispatcher.cs -Pattern "NV_|AMD_|INTEL_|GL_NV|GL_AMD|GL_INTEL"
+  ```
+  Expected: no matches in the new code (matches elsewhere in the file from unrelated existing code don't count).
+
+- [ ] **A3: Baseline doc has real numbers + conclusion.**
+  Open `docs/plans/2026-05-11-phase-n6-perf-baseline.md` and visually confirm no `<n>`, `<pct>`, `TBD`, or empty conclusion section.
+
+- [ ] **A4: Roadmap split shipped.**
+  ```powershell
+  Select-String -Path docs/plans/2026-04-11-roadmap.md -Pattern "N\.6 slice"
+  ```
+  Expected: two matches (slice 1 + slice 2 bullets).
+
+- [ ] **A5: `dotnet build` green, no new warnings.**
+  ```powershell
+  dotnet build
+  ```
+  Expected: succeeds. Note any new warnings vs the build output before the slice started.
+
+- [ ] **A6: `dotnet test` green at baseline (~1688 passing, ~8 pre-existing failures).**
+  ```powershell
+  dotnet test --no-build
+  ```
+  Expected: pass count unchanged from before the slice started; failure list unchanged.
+
+- [ ] **A7: No visible regression.**
+  Confirmed during Task 1.9 and Task 3 measurements — the user was in-world repeatedly and didn't observe any rendering issue. If anything looked off during measurement, file it as an issue and decide whether it blocks slice 1 acceptance.
+
+If any acceptance criterion fails, return to the relevant task and re-do it. Do not declare slice 1 complete with failing acceptance.
+
+---
+
+## After slice 1 lands
+
+The baseline document's conclusion paragraph (§4) determines the next phase:
+
+- **If conclusion recommends C.1.5:** brainstorm C.1.5 spec next, using [docs/plans/2026-04-27-phase-c1-pes-particles.md:285-295](../../plans/2026-04-27-phase-c1-pes-particles.md) as the starting scope.
+- **If conclusion recommends N.6 slice 2:** brainstorm slice 2 spec next, addressing legacy `TextureCache` cleanup + atlas + persistent-mapped buffers based on the histogram data.
+- **If conclusion recommends Tier 2:** consult [docs/plans/2026-05-10-perf-tiers-2-3-roadmap.md](../../plans/2026-05-10-perf-tiers-2-3-roadmap.md) and brainstorm a Tier 2 spec.
+
+The choice is data-driven; the recommendation paragraph is the contract. Don't re-litigate the decision once the numbers are in.