docs: add abstract nest engine implementation plan

9 tasks across 4 chunks: NestEngineBase + DefaultNestEngine,
NestEngineRegistry + NestEngineInfo, callsite migration (16 sites),
verification and docs update.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
This commit is contained in:
2026-03-15 20:59:51 -04:00
parent 068de63e83
commit 9bd262dec0

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# Abstract Nest Engine Implementation Plan
> **For agentic workers:** REQUIRED: Use superpowers:subagent-driven-development (if subagents available) or superpowers:executing-plans to implement this plan. Steps use checkbox (`- [ ]`) syntax for tracking.
**Goal:** Refactor the concrete `NestEngine` into an abstract `NestEngineBase` with pluggable implementations, a registry for engine discovery/selection, and plugin loading from DLLs.
**Architecture:** Extract shared state and utilities into `NestEngineBase` (abstract). Current logic becomes `DefaultNestEngine`. `NestEngineRegistry` provides factory creation, built-in registration, and DLL plugin discovery. All callsites migrate from `new NestEngine(plate)` to `NestEngineRegistry.Create(plate)`.
**Tech Stack:** C# / .NET 8, OpenNest.Engine, OpenNest (WinForms), OpenNest.Mcp, OpenNest.Console
**Spec:** `docs/superpowers/specs/2026-03-15-abstract-nest-engine-design.md`
**Deferred:** `StripNester.cs``StripNestEngine.cs` conversion is deferred to the strip nester implementation plan (`docs/superpowers/plans/2026-03-15-strip-nester.md`). That plan should be updated to create `StripNestEngine` as a `NestEngineBase` subclass and register it in `NestEngineRegistry`. The UI engine selector combobox is also deferred — it can be added once there are multiple engines to choose from.
---
## Chunk 1: NestEngineBase and DefaultNestEngine
### Task 1: Create NestEngineBase abstract class
**Files:**
- Create: `OpenNest.Engine/NestEngineBase.cs`
This is the abstract base class. It holds shared properties, abstract `Name`/`Description`, virtual methods that return empty lists by default, convenience overloads that mutate the plate, `FillExact` (non-virtual), and protected utility methods extracted from the current `NestEngine`.
- [ ] **Step 1: Create NestEngineBase.cs**
```csharp
using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.Linq;
using System.Threading;
using OpenNest.Geometry;
namespace OpenNest
{
public abstract class NestEngineBase
{
protected NestEngineBase(Plate plate)
{
Plate = plate;
}
public Plate Plate { get; set; }
public int PlateNumber { get; set; }
public NestDirection NestDirection { get; set; }
public NestPhase WinnerPhase { get; protected set; }
public List<PhaseResult> PhaseResults { get; } = new();
public List<AngleResult> AngleResults { get; } = new();
public abstract string Name { get; }
public abstract string Description { get; }
// --- Virtual methods (side-effect-free, return parts) ---
public virtual List<Part> Fill(NestItem item, Box workArea,
IProgress<NestProgress> progress, CancellationToken token)
{
return new List<Part>();
}
public virtual List<Part> Fill(List<Part> groupParts, Box workArea,
IProgress<NestProgress> progress, CancellationToken token)
{
return new List<Part>();
}
public virtual List<Part> PackArea(Box box, List<NestItem> items,
IProgress<NestProgress> progress, CancellationToken token)
{
return new List<Part>();
}
// --- FillExact (non-virtual, delegates to virtual Fill) ---
public List<Part> FillExact(NestItem item, Box workArea,
IProgress<NestProgress> progress, CancellationToken token)
{
return Fill(item, workArea, progress, token);
}
// --- Convenience overloads (mutate plate, return bool) ---
public bool Fill(NestItem item)
{
return Fill(item, Plate.WorkArea());
}
public bool Fill(NestItem item, Box workArea)
{
var parts = Fill(item, workArea, null, CancellationToken.None);
if (parts == null || parts.Count == 0)
return false;
Plate.Parts.AddRange(parts);
return true;
}
public bool Fill(List<Part> groupParts)
{
return Fill(groupParts, Plate.WorkArea());
}
public bool Fill(List<Part> groupParts, Box workArea)
{
var parts = Fill(groupParts, workArea, null, CancellationToken.None);
if (parts == null || parts.Count == 0)
return false;
Plate.Parts.AddRange(parts);
return true;
}
public bool Pack(List<NestItem> items)
{
var workArea = Plate.WorkArea();
var parts = PackArea(workArea, items, null, CancellationToken.None);
if (parts == null || parts.Count == 0)
return false;
Plate.Parts.AddRange(parts);
return true;
}
// --- Protected utilities ---
protected static void ReportProgress(
IProgress<NestProgress> progress,
NestPhase phase,
int plateNumber,
List<Part> best,
Box workArea,
string description)
{
if (progress == null || best == null || best.Count == 0)
return;
var score = FillScore.Compute(best, workArea);
var clonedParts = new List<Part>(best.Count);
var totalPartArea = 0.0;
foreach (var part in best)
{
clonedParts.Add((Part)part.Clone());
totalPartArea += part.BaseDrawing.Area;
}
var bounds = best.GetBoundingBox();
var msg = $"[Progress] Phase={phase}, Plate={plateNumber}, Parts={score.Count}, " +
$"Density={score.Density:P1}, Nested={bounds.Width:F1}x{bounds.Length:F1}, " +
$"PartArea={totalPartArea:F0}, Remnant={workArea.Area() - totalPartArea:F0}, " +
$"WorkArea={workArea.Width:F1}x{workArea.Length:F1} | {description}";
Debug.WriteLine(msg);
try { System.IO.File.AppendAllText(
System.IO.Path.Combine(Environment.GetFolderPath(Environment.SpecialFolder.Desktop), "nest-debug.log"),
$"{DateTime.Now:HH:mm:ss.fff} {msg}\n"); } catch { }
progress.Report(new NestProgress
{
Phase = phase,
PlateNumber = plateNumber,
BestPartCount = score.Count,
BestDensity = score.Density,
NestedWidth = bounds.Width,
NestedLength = bounds.Length,
NestedArea = totalPartArea,
UsableRemnantArea = workArea.Area() - totalPartArea,
BestParts = clonedParts,
Description = description
});
}
protected string BuildProgressSummary()
{
if (PhaseResults.Count == 0)
return null;
var parts = new List<string>(PhaseResults.Count);
foreach (var r in PhaseResults)
parts.Add($"{FormatPhaseName(r.Phase)}: {r.PartCount}");
return string.Join(" | ", parts);
}
protected bool IsBetterFill(List<Part> candidate, List<Part> current, Box workArea)
{
if (candidate == null || candidate.Count == 0)
return false;
if (current == null || current.Count == 0)
return true;
return FillScore.Compute(candidate, workArea) > FillScore.Compute(current, workArea);
}
protected bool IsBetterValidFill(List<Part> candidate, List<Part> current, Box workArea)
{
if (candidate != null && candidate.Count > 0 && HasOverlaps(candidate, Plate.PartSpacing))
{
Debug.WriteLine($"[IsBetterValidFill] REJECTED {candidate.Count} parts due to overlaps (current best: {current?.Count ?? 0})");
return false;
}
return IsBetterFill(candidate, current, workArea);
}
protected static bool HasOverlaps(List<Part> parts, double spacing)
{
if (parts == null || parts.Count <= 1)
return false;
for (var i = 0; i < parts.Count; i++)
{
var box1 = parts[i].BoundingBox;
for (var j = i + 1; j < parts.Count; j++)
{
var box2 = parts[j].BoundingBox;
if (box1.Right < box2.Left || box2.Right < box1.Left ||
box1.Top < box2.Bottom || box2.Top < box1.Bottom)
continue;
List<Vector> pts;
if (parts[i].Intersects(parts[j], out pts))
{
var b1 = parts[i].BoundingBox;
var b2 = parts[j].BoundingBox;
Debug.WriteLine($"[HasOverlaps] Overlap: part[{i}] ({parts[i].BaseDrawing?.Name}) @ ({b1.Left:F2},{b1.Bottom:F2})-({b1.Right:F2},{b1.Top:F2}) rot={parts[i].Rotation:F2}" +
$" vs part[{j}] ({parts[j].BaseDrawing?.Name}) @ ({b2.Left:F2},{b2.Bottom:F2})-({b2.Right:F2},{b2.Top:F2}) rot={parts[j].Rotation:F2}" +
$" intersections={pts?.Count ?? 0}");
return true;
}
}
}
return false;
}
protected static string FormatPhaseName(NestPhase phase)
{
switch (phase)
{
case NestPhase.Pairs: return "Pairs";
case NestPhase.Linear: return "Linear";
case NestPhase.RectBestFit: return "BestFit";
case NestPhase.Remainder: return "Remainder";
default: return phase.ToString();
}
}
}
}
```
- [ ] **Step 2: Build to verify**
Run: `dotnet build OpenNest.Engine/OpenNest.Engine.csproj`
Expected: Build succeeded
- [ ] **Step 3: Commit**
```bash
git add OpenNest.Engine/NestEngineBase.cs
git commit -m "feat: add NestEngineBase abstract class"
```
---
### Task 2: Convert NestEngine to DefaultNestEngine
**Files:**
- Rename: `OpenNest.Engine/NestEngine.cs``OpenNest.Engine/DefaultNestEngine.cs`
Rename the class, make it inherit `NestEngineBase`, add `Name`/`Description`, change the virtual methods to `override`, and remove methods that now live in the base class (convenience overloads, `ReportProgress`, `BuildProgressSummary`, `IsBetterFill`, `IsBetterValidFill`, `HasOverlaps`, `FormatPhaseName`, `FillExact`).
- [ ] **Step 1: Rename the file**
```bash
git mv OpenNest.Engine/NestEngine.cs OpenNest.Engine/DefaultNestEngine.cs
```
- [ ] **Step 2: Update class declaration and add inheritance**
In `DefaultNestEngine.cs`, change the class declaration from:
```csharp
public class NestEngine
{
public NestEngine(Plate plate)
{
Plate = plate;
}
public Plate Plate { get; set; }
public NestDirection NestDirection { get; set; }
public int PlateNumber { get; set; }
public NestPhase WinnerPhase { get; private set; }
public List<PhaseResult> PhaseResults { get; } = new();
public bool ForceFullAngleSweep { get; set; }
public List<AngleResult> AngleResults { get; } = new();
```
To:
```csharp
public class DefaultNestEngine : NestEngineBase
{
public DefaultNestEngine(Plate plate) : base(plate)
{
}
public override string Name => "Default";
public override string Description => "Multi-phase nesting (Linear, Pairs, RectBestFit, Remainder)";
public bool ForceFullAngleSweep { get; set; }
```
This removes properties that now come from the base class (`Plate`, `PlateNumber`, `NestDirection`, `WinnerPhase`, `PhaseResults`, `AngleResults`).
- [ ] **Step 3: Convert the convenience Fill overloads to override the virtual methods**
Remove the non-progress `Fill` convenience overloads (they are now in the base class). The two remaining `Fill` methods that take `IProgress<NestProgress>` and `CancellationToken` become overrides.
Change:
```csharp
public List<Part> Fill(NestItem item, Box workArea,
IProgress<NestProgress> progress, CancellationToken token)
```
To:
```csharp
public override List<Part> Fill(NestItem item, Box workArea,
IProgress<NestProgress> progress, CancellationToken token)
```
Change:
```csharp
public List<Part> Fill(List<Part> groupParts, Box workArea,
IProgress<NestProgress> progress, CancellationToken token)
```
To:
```csharp
public override List<Part> Fill(List<Part> groupParts, Box workArea,
IProgress<NestProgress> progress, CancellationToken token)
```
Remove these methods entirely (now in base class):
- `bool Fill(NestItem item)` (2-arg convenience)
- `bool Fill(NestItem item, Box workArea)` (convenience that calls the 4-arg)
- `bool Fill(List<Part> groupParts)` (convenience)
- `bool Fill(List<Part> groupParts, Box workArea)` (convenience that calls the 4-arg)
- `FillExact` (now in base class)
- `ReportProgress` (now in base class)
- `BuildProgressSummary` (now in base class)
- `IsBetterFill` (now in base class)
- `IsBetterValidFill` (now in base class)
- `HasOverlaps` (now in base class)
- `FormatPhaseName` (now in base class)
- [ ] **Step 4: Convert Pack/PackArea to override**
Remove `Pack(List<NestItem>)` (now in base class).
Convert `PackArea` to override with the new signature. Replace:
```csharp
public bool Pack(List<NestItem> items)
{
var workArea = Plate.WorkArea();
return PackArea(workArea, items);
}
public bool PackArea(Box box, List<NestItem> items)
{
var binItems = BinConverter.ToItems(items, Plate.PartSpacing, Plate.Area());
var bin = BinConverter.CreateBin(box, Plate.PartSpacing);
var engine = new PackBottomLeft(bin);
engine.Pack(binItems);
var parts = BinConverter.ToParts(bin, items);
Plate.Parts.AddRange(parts);
return parts.Count > 0;
}
```
With:
```csharp
public override List<Part> PackArea(Box box, List<NestItem> items,
IProgress<NestProgress> progress, CancellationToken token)
{
var binItems = BinConverter.ToItems(items, Plate.PartSpacing, Plate.Area());
var bin = BinConverter.CreateBin(box, Plate.PartSpacing);
var engine = new PackBottomLeft(bin);
engine.Pack(binItems);
return BinConverter.ToParts(bin, items);
}
```
Note: the `progress` and `token` parameters are not used yet in the default rectangle packing — the contract is there for engines that need them.
- [ ] **Step 5: Update BruteForceRunner to use DefaultNestEngine**
`BruteForceRunner.cs` is in the same project and still references `NestEngine`. It must be updated before the Engine project can compile. This is the one callsite that stays as a direct `DefaultNestEngine` reference (not via registry) because training data must come from the known algorithm.
In `OpenNest.Engine/ML/BruteForceRunner.cs`, change line 30:
```csharp
var engine = new NestEngine(plate);
```
To:
```csharp
var engine = new DefaultNestEngine(plate);
```
- [ ] **Step 6: Build to verify**
Run: `dotnet build OpenNest.Engine/OpenNest.Engine.csproj`
Expected: Build succeeded (other projects will have errors since their callsites still reference `NestEngine` — fixed in Chunk 3)
- [ ] **Step 7: Commit**
```bash
git add OpenNest.Engine/DefaultNestEngine.cs OpenNest.Engine/ML/BruteForceRunner.cs
git commit -m "refactor: rename NestEngine to DefaultNestEngine, inherit NestEngineBase"
```
---
## Chunk 2: NestEngineRegistry and NestEngineInfo
### Task 3: Create NestEngineInfo
**Files:**
- Create: `OpenNest.Engine/NestEngineInfo.cs`
- [ ] **Step 1: Create NestEngineInfo.cs**
```csharp
using System;
namespace OpenNest
{
public class NestEngineInfo
{
public NestEngineInfo(string name, string description, Func<Plate, NestEngineBase> factory)
{
Name = name;
Description = description;
Factory = factory;
}
public string Name { get; }
public string Description { get; }
public Func<Plate, NestEngineBase> Factory { get; }
}
}
```
- [ ] **Step 2: Build to verify**
Run: `dotnet build OpenNest.Engine/OpenNest.Engine.csproj`
Expected: Build succeeded
- [ ] **Step 3: Commit**
```bash
git add OpenNest.Engine/NestEngineInfo.cs
git commit -m "feat: add NestEngineInfo metadata class"
```
---
### Task 4: Create NestEngineRegistry
**Files:**
- Create: `OpenNest.Engine/NestEngineRegistry.cs`
Static class with built-in registration, plugin loading, active engine selection, and factory creation.
- [ ] **Step 1: Create NestEngineRegistry.cs**
```csharp
using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.IO;
using System.Linq;
using System.Reflection;
namespace OpenNest
{
public static class NestEngineRegistry
{
private static readonly List<NestEngineInfo> engines = new();
static NestEngineRegistry()
{
Register("Default",
"Multi-phase nesting (Linear, Pairs, RectBestFit, Remainder)",
plate => new DefaultNestEngine(plate));
}
public static IReadOnlyList<NestEngineInfo> AvailableEngines => engines;
public static string ActiveEngineName { get; set; } = "Default";
public static NestEngineBase Create(Plate plate)
{
var info = engines.FirstOrDefault(e =>
e.Name.Equals(ActiveEngineName, StringComparison.OrdinalIgnoreCase));
if (info == null)
{
Debug.WriteLine($"[NestEngineRegistry] Engine '{ActiveEngineName}' not found, falling back to Default");
info = engines[0];
}
return info.Factory(plate);
}
public static void Register(string name, string description, Func<Plate, NestEngineBase> factory)
{
if (engines.Any(e => e.Name.Equals(name, StringComparison.OrdinalIgnoreCase)))
{
Debug.WriteLine($"[NestEngineRegistry] Duplicate engine '{name}' skipped");
return;
}
engines.Add(new NestEngineInfo(name, description, factory));
}
public static void LoadPlugins(string directory)
{
if (!Directory.Exists(directory))
return;
foreach (var dll in Directory.GetFiles(directory, "*.dll"))
{
try
{
var assembly = Assembly.LoadFrom(dll);
foreach (var type in assembly.GetTypes())
{
if (type.IsAbstract || !typeof(NestEngineBase).IsAssignableFrom(type))
continue;
var ctor = type.GetConstructor(new[] { typeof(Plate) });
if (ctor == null)
{
Debug.WriteLine($"[NestEngineRegistry] Skipping {type.Name}: no Plate constructor");
continue;
}
// Create a temporary instance to read Name and Description.
try
{
var tempPlate = new Plate();
var instance = (NestEngineBase)ctor.Invoke(new object[] { tempPlate });
Register(instance.Name, instance.Description,
plate => (NestEngineBase)ctor.Invoke(new object[] { plate }));
Debug.WriteLine($"[NestEngineRegistry] Loaded plugin engine: {instance.Name}");
}
catch (Exception ex)
{
Debug.WriteLine($"[NestEngineRegistry] Failed to instantiate {type.Name}: {ex.Message}");
}
}
}
catch (Exception ex)
{
Debug.WriteLine($"[NestEngineRegistry] Failed to load assembly {Path.GetFileName(dll)}: {ex.Message}");
}
}
}
}
}
```
- [ ] **Step 2: Build to verify**
Run: `dotnet build OpenNest.Engine/OpenNest.Engine.csproj`
Expected: Build succeeded
- [ ] **Step 3: Commit**
```bash
git add OpenNest.Engine/NestEngineRegistry.cs
git commit -m "feat: add NestEngineRegistry with built-in registration and plugin loading"
```
---
## Chunk 3: Callsite Migration
### Task 5: Migrate OpenNest.Mcp callsites
**Files:**
- Modify: `OpenNest.Mcp/Tools/NestingTools.cs`
Six `new NestEngine(plate)` calls become `NestEngineRegistry.Create(plate)`. The `PackArea` call on line 276 changes signature since `PackArea` now returns `List<Part>` instead of mutating the plate.
- [ ] **Step 1: Replace all NestEngine instantiations**
In `NestingTools.cs`, replace all six occurrences of `new NestEngine(plate)` with `NestEngineRegistry.Create(plate)`.
Lines to change:
- Line 37: `var engine = new NestEngine(plate);``var engine = NestEngineRegistry.Create(plate);`
- Line 73: `var engine = new NestEngine(plate);``var engine = NestEngineRegistry.Create(plate);`
- Line 114: `var engine = new NestEngine(plate);``var engine = NestEngineRegistry.Create(plate);`
- Line 176: `var engine = new NestEngine(plate);``var engine = NestEngineRegistry.Create(plate);`
- Line 255: `var engine = new NestEngine(plate);``var engine = NestEngineRegistry.Create(plate);`
- Line 275: `var engine = new NestEngine(plate);``var engine = NestEngineRegistry.Create(plate);`
- [ ] **Step 2: Fix PackArea call in AutoNestPlate**
The old code on line 276 was:
```csharp
engine.PackArea(workArea, packItems);
```
This used the old `bool PackArea(Box, List<NestItem>)` which mutated the plate. The new virtual method returns `List<Part>`. Use the convenience `Pack`-like pattern instead. Replace lines 274-277:
```csharp
var before = plate.Parts.Count;
var engine = new NestEngine(plate);
engine.PackArea(workArea, packItems);
totalPlaced += plate.Parts.Count - before;
```
With:
```csharp
var engine = NestEngineRegistry.Create(plate);
var packParts = engine.PackArea(workArea, packItems, null, CancellationToken.None);
if (packParts.Count > 0)
{
plate.Parts.AddRange(packParts);
totalPlaced += packParts.Count;
}
```
- [ ] **Step 3: Build OpenNest.Mcp**
Run: `dotnet build OpenNest.Mcp/OpenNest.Mcp.csproj`
Expected: Build succeeded
- [ ] **Step 4: Commit**
```bash
git add OpenNest.Mcp/Tools/NestingTools.cs
git commit -m "refactor: migrate NestingTools to NestEngineRegistry"
```
---
### Task 6: Migrate OpenNest.Console callsites
**Files:**
- Modify: `OpenNest.Console/Program.cs`
Three `new NestEngine(plate)` calls. The `PackArea` call also needs the same signature update.
- [ ] **Step 1: Replace NestEngine instantiations**
In `Program.cs`, replace:
- Line 351: `var engine = new NestEngine(plate);``var engine = NestEngineRegistry.Create(plate);`
- Line 380: `var engine = new NestEngine(plate);``var engine = NestEngineRegistry.Create(plate);`
- [ ] **Step 2: Fix PackArea call**
Replace lines 370-372:
```csharp
var engine = new NestEngine(plate);
var before = plate.Parts.Count;
engine.PackArea(workArea, packItems);
```
With:
```csharp
var engine = NestEngineRegistry.Create(plate);
var packParts = engine.PackArea(workArea, packItems, null, CancellationToken.None);
plate.Parts.AddRange(packParts);
```
And update line 374-375 from:
```csharp
if (plate.Parts.Count > before)
success = true;
```
To:
```csharp
if (packParts.Count > 0)
success = true;
```
- [ ] **Step 3: Build OpenNest.Console**
Run: `dotnet build OpenNest.Console/OpenNest.Console.csproj`
Expected: Build succeeded
- [ ] **Step 4: Commit**
```bash
git add OpenNest.Console/Program.cs
git commit -m "refactor: migrate Console Program to NestEngineRegistry"
```
---
### Task 7: Migrate OpenNest WinForms callsites
**Files:**
- Modify: `OpenNest/Actions/ActionFillArea.cs`
- Modify: `OpenNest/Controls/PlateView.cs`
- Modify: `OpenNest/Forms/MainForm.cs`
- [ ] **Step 1: Migrate ActionFillArea.cs**
In `ActionFillArea.cs`, replace both `new NestEngine(plateView.Plate)` calls:
- Line 50: `var engine = new NestEngine(plateView.Plate);``var engine = NestEngineRegistry.Create(plateView.Plate);`
- Line 64: `var engine = new NestEngine(plateView.Plate);``var engine = NestEngineRegistry.Create(plateView.Plate);`
- [ ] **Step 2: Migrate PlateView.cs**
In `PlateView.cs`, replace:
- Line 836: `var engine = new NestEngine(Plate);``var engine = NestEngineRegistry.Create(Plate);`
- [ ] **Step 3: Migrate MainForm.cs**
In `MainForm.cs`, replace all three `new NestEngine(plate)` calls:
- Line 797: `var engine = new NestEngine(plate) { PlateNumber = plateCount };``var engine = NestEngineRegistry.Create(plate); engine.PlateNumber = plateCount;`
- Line 829: `var engine = new NestEngine(plate);``var engine = NestEngineRegistry.Create(plate);`
- Line 965: `var engine = new NestEngine(plate);``var engine = NestEngineRegistry.Create(plate);`
- [ ] **Step 4: Fix MainForm PackArea call**
In `MainForm.cs`, the auto-nest pack phase (around line 829-832) uses the old `PackArea` signature. Replace:
```csharp
var engine = new NestEngine(plate);
var partsBefore = plate.Parts.Count;
engine.PackArea(workArea, packItems);
var packed = plate.Parts.Count - partsBefore;
```
With:
```csharp
var engine = NestEngineRegistry.Create(plate);
var packParts = engine.PackArea(workArea, packItems, null, CancellationToken.None);
plate.Parts.AddRange(packParts);
var packed = packParts.Count;
```
- [ ] **Step 5: Add plugin loading at startup**
In `MainForm.cs`, find where post-processors are loaded at startup (look for `Posts` directory loading) and add engine plugin loading nearby. Add after the existing plugin loading:
```csharp
var enginesDir = Path.Combine(Application.StartupPath, "Engines");
NestEngineRegistry.LoadPlugins(enginesDir);
```
If there is no explicit post-processor loading call visible, add this to the `MainForm` constructor or `Load` event.
- [ ] **Step 6: Build the full solution**
Run: `dotnet build OpenNest.sln`
Expected: Build succeeded with no errors
- [ ] **Step 7: Commit**
```bash
git add OpenNest/Actions/ActionFillArea.cs OpenNest/Controls/PlateView.cs OpenNest/Forms/MainForm.cs
git commit -m "refactor: migrate WinForms callsites to NestEngineRegistry"
```
---
## Chunk 4: Verification and Cleanup
### Task 8: Verify no remaining NestEngine references
**Files:**
- No changes expected — verification only
- [ ] **Step 1: Search for stale references**
Run: `grep -rn "new NestEngine(" --include="*.cs" .`
Expected: Only `BruteForceRunner.cs` should have `new DefaultNestEngine(`. No `new NestEngine(` references should remain.
Also run: `grep -rn "class NestEngine[^B]" --include="*.cs" .`
Expected: No matches (the old `class NestEngine` no longer exists).
- [ ] **Step 2: Build and run smoke test**
Run: `dotnet build OpenNest.sln`
Expected: Build succeeded, 0 errors, 0 warnings related to NestEngine
- [ ] **Step 3: Publish MCP server**
Run: `dotnet publish OpenNest.Mcp/OpenNest.Mcp.csproj -c Release -o "$USERPROFILE/.claude/mcp/OpenNest.Mcp"`
Expected: Publish succeeded
- [ ] **Step 4: Commit if any fixes were needed**
If any issues were found and fixed in previous steps, commit them now.
---
### Task 9: Update CLAUDE.md architecture documentation
**Files:**
- Modify: `CLAUDE.md`
- [ ] **Step 1: Update architecture section**
Update the `### OpenNest.Engine` section in `CLAUDE.md` to document the new engine hierarchy:
- `NestEngineBase` is the abstract base class
- `DefaultNestEngine` is the current multi-phase engine (formerly `NestEngine`)
- `NestEngineRegistry` manages available engines and the active selection
- `NestEngineInfo` holds engine metadata
- Plugin engines loaded from `Engines/` directory
Also update any references to `NestEngine` that should now say `DefaultNestEngine` or `NestEngineBase`.
- [ ] **Step 2: Build to verify no docs broke anything**
Run: `dotnet build OpenNest.sln`
Expected: Build succeeded
- [ ] **Step 3: Commit**
```bash
git add CLAUDE.md
git commit -m "docs: update CLAUDE.md for abstract nest engine architecture"
```