ryanwhois · Oct 5, 2026 · Oct 4, 2026 · Oct 4, 2026 · Oct 4, 2026 · Oct 4, 2026
diff --git a/.github/workflows/cpp-build.yml b/.github/workflows/cpp-build.yml
@@ -37,5 +37,4 @@ jobs:
 
     - name: Run Tests
       run: |
-        cd src/cpp/build
-        ctest --output-on-failure
+        ctest --test-dir src/cpp/build --build-config ${{ matrix.build_type }} --output-on-failure
diff --git a/.github/workflows/python-checks.yml b/.github/workflows/python-checks.yml
@@ -0,0 +1,24 @@
+name: Python Checks
+
+on:
+  push:
+    branches: [main, develop]
+    paths:
+      - 'examples/python/**'
+      - '.github/workflows/python-checks.yml'
+  pull_request:
+    branches: [main]
+
+jobs:
+  test:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - uses: actions/setup-python@v5
+        with:
+          python-version: '3.12'
+      - name: Run dependency-free inspector tests
+        working-directory: examples/python
+        run: python -m unittest -v test_inspect_mesh.py
+      - name: Verify CLI help
+        run: python examples/python/inspect_mesh.py --help
diff --git a/.github/workflows/wasm-build.yml b/.github/workflows/wasm-build.yml
@@ -37,7 +37,9 @@ jobs:
         cd src/wasm
         mkdir -p build
         cd build
-        emcmake cmake .. -DCMAKE_BUILD_TYPE=Release
+        emcmake cmake .. \
+          -DCMAKE_BUILD_TYPE=Release \
+          -DEigen3_DIR=/usr/share/eigen3/cmake
 
     - name: Build WASM
       run: |
@@ -77,7 +79,7 @@ jobs:
     - name: Setup Node.js for testing
       uses: actions/setup-node@v4
       with:
-        node-version: '18'
+        node-version: '20'
 
     - name: Run WASM tests
       run: |

diff --git a/CHANGELOG.md b/CHANGELOG.md
@@ -2,6 +2,24 @@
 
 ## [Unreleased]
 
+## [1.2.0] - 2026-10-05
+
+### Added
+- Explicit boundary halfedges, closed boundary-loop traversal, and topology validation in both mesh cores.
+- Constrained Poisson helpers, boundary-aware Gaussian curvature, and open-mesh Gauss–Bonnet tests.
+- Implemented C# Heat Method weak-divergence stage and boundary-circle constrained solve.
+- Dependency-free Python OBJ inspector with parser, topology, and degeneracy tests.
+- Responsive interactive DDG workbench with JavaScript fallback and optional WASM engine.
+- Root Vercel routing for the workbench.
+
+### Changed
+- Cotangent Laplacians are assembled once per undirected edge and are symmetric by construction.
+- Boundary-circle parameterization follows boundary order and uses chord-length spacing.
+- Project metadata now reports version 1.2.0.
+
+### Deferred
+- True LSCM, harmonic basis generation, ARAP, and formal cross-language parity datasets.
+
 ### Changed
 - Replaced overstated top-level docs with explicit maturity labels.
 - Updated C++/C#/WASM workflow action versions and corrected C# test execution path.

diff --git a/README.md b/README.md
@@ -4,19 +4,20 @@ Companion implementations and notes for Keenan Crane's *Discrete Differential Ge
 
 > Current state: educational and improving, not production-complete.
 
-[![C++ Build](https://github.com/rhughes42/discrete-differential-geometry-basics/actions/workflows/cpp-build.yml/badge.svg)](https://github.com/rhughes42/discrete-differential-geometry-basics/actions/workflows/cpp-build.yml)
-[![C# Build](https://github.com/rhughes42/discrete-differential-geometry-basics/actions/workflows/csharp-build.yml/badge.svg)](https://github.com/rhughes42/discrete-differential-geometry-basics/actions/workflows/csharp-build.yml)
-[![WASM Build](https://github.com/rhughes42/discrete-differential-geometry-basics/actions/workflows/wasm-build.yml/badge.svg)](https://github.com/rhughes42/discrete-differential-geometry-basics/actions/workflows/wasm-build.yml)
+[![C++ Build](https://github.com/ryanwhois/discrete-differential-geometry-basics/actions/workflows/cpp-build.yml/badge.svg)](https://github.com/ryanwhois/discrete-differential-geometry-basics/actions/workflows/cpp-build.yml)
+[![C# Build](https://github.com/ryanwhois/discrete-differential-geometry-basics/actions/workflows/csharp-build.yml/badge.svg)](https://github.com/ryanwhois/discrete-differential-geometry-basics/actions/workflows/csharp-build.yml)
+[![WASM Build](https://github.com/ryanwhois/discrete-differential-geometry-basics/actions/workflows/wasm-build.yml/badge.svg)](https://github.com/ryanwhois/discrete-differential-geometry-basics/actions/workflows/wasm-build.yml)
+[![Python Checks](https://github.com/ryanwhois/discrete-differential-geometry-basics/actions/workflows/python-checks.yml/badge.svg)](https://github.com/ryanwhois/discrete-differential-geometry-basics/actions/workflows/python-checks.yml)
 
 ## Status Snapshot
 
 | Area | Status | Notes |
 |---|---|---|
-| C++ core mesh + DDG algorithms | **Partial** | Implemented and buildable; some algorithms use simplified operators/solvers |
-| C# core mesh + DDG algorithms | **Partial** | All six algorithm modules exist; several contain placeholder/simplified steps |
-| Python tooling | **Experimental** | Lightweight visualization script only |
-| Web companion | **Experimental** | WASM demo/benchmark pages, no full `web/index.html` app |
-| Test coverage | **Partial** | Good basic unit tests; limited degeneracy/non-manifold stress coverage |
+| C++ core mesh + DDG algorithms | **Partial** | Boundary-safe topology, symmetric cotan operators, constrained solves; Hodge bases remain experimental |
+| C# core mesh + DDG algorithms | **Partial** | Boundary-safe parity for topology, curvature, Laplacian, Heat divergence, and boundary mapping |
+| Python tooling | **Supported utility** | Dependency-free OBJ topology inspector plus optional visualizer |
+| Web companion | **Interactive reference** | Responsive workbench with a JS reference engine and optional WASM acceleration |
+| Test coverage | **Partial** | Closed/open topology and Gauss–Bonnet coverage; broader parity datasets remain future work |
 
 See `docs/status/IMPLEMENTATION_AUDIT.md` for the detailed audit.
 
@@ -57,7 +58,9 @@ dotnet test --configuration Release
 
 ### WebAssembly
 
-WASM bindings and demos live under `src/wasm/` and `web/wasm-demo.html` / `web/wasm-benchmark.html`.
+WASM bindings and demos live under `src/wasm/`. Open `web/index.html` for
+the interactive workbench; it falls back honestly to the JavaScript reference
+engine when compiled WASM artifacts are absent.
 
 ## Repository Layout
 
@@ -67,7 +70,7 @@ src/csharp/     C# core mesh, algorithms, tests, CLI examples
 src/wasm/       Emscripten bindings and wasm build config
 docs/           Chapters, formulas, assignments, tutorials, status docs
 examples/       Example usage notes and Python helper script
-web/            Static WASM demo pages
+web/            Interactive scientific workbench and legacy WASM pages
 ```
 
 ## Documentation
@@ -82,17 +85,15 @@ web/            Static WASM demo pages
 
 ## Roadmap (Realistic)
 
-### 1.1.x Stabilization (current)
-- Mesh robustness and topology validation improvements
-- Build/test reliability fixes
-- Documentation honesty and audit coverage
-- Better numerical safeguards in current algorithms
-
-### 1.2.0 Target
-- Reusable Poisson solve infrastructure
-- ARAP deformation scaffold (explicitly experimental)
-- Expanded degeneracy/non-manifold test set
-- Better parity notes across C++/C#/WASM
+### 1.2.0 release candidate
+- Explicit boundary halfedges and topology validation in C++ and C#
+- Symmetric cotan assembly and constrained Poisson infrastructure
+- Boundary-aware curvature, Heat divergence, and harmonic disk mapping
+- Dependency-free Python inspection and an interactive web workbench
+
+### Later
+- True LSCM assembly, harmonic basis generation, and ARAP deformation
+- Cross-language parity datasets and larger numerical regression suites
 
 ## Contributing
 

diff --git a/docs/status/DETAILED_IMPLEMENTATION_PLAN.md b/docs/status/DETAILED_IMPLEMENTATION_PLAN.md
@@ -0,0 +1,50 @@
+# Detailed Implementation Plan
+
+## Objective
+
+Turn the repository from a collection of educational implementations into a
+coherent, testable DDG course companion without overstating numerical maturity.
+
+## Completed dependency order
+
+### 1. Topology foundation
+
+- Validate triangular input, indices, duplicate directed edges, manifold edge
+  incidence, and degenerate geometry.
+- Construct explicit boundary twins and boundary loops.
+- Make one-ring traversal safe and consistent in C++ and C#.
+
+### 2. Discrete operators
+
+- Correct opposite-angle cotangent evaluation.
+- Assemble symmetric Laplacians once per undirected edge.
+- Add reusable Dirichlet-constrained solves.
+- Include boundary angle defects in Gaussian curvature.
+
+### 3. Algorithms
+
+- Route Heat Method distance recovery through an anchored Poisson solve.
+- Implement the C# weak-divergence stage.
+- Replace unordered boundary selection with ordered, chord-length circles.
+- Fail explicitly for the still-deferred true LSCM implementation.
+
+### 4. Verification
+
+- Add closed and open topology tests.
+- Add boundary Gauss–Bonnet tests.
+- Add a dependency-free OBJ inspector and four Python tests.
+- Align C++, C#, Python, and WASM CI workflows with the source layout.
+
+### 5. Educational web surface
+
+- Provide a responsive rail–canvas–rail workbench.
+- Expose mesh fixtures, algorithm controls, topology metrics, theory, and
+  diagnostics.
+- Use the JS reference engine when WASM output is absent and label the active
+  engine honestly.
+- Add root and `/workbench` routing for Vercel.
+
+## Deferred work
+
+True LSCM, harmonic basis generation, ARAP, sparse production-scale constraint
+elimination, and formal parity datasets remain separate milestones.
diff --git a/docs/status/IMPLEMENTATION_AUDIT.md b/docs/status/IMPLEMENTATION_AUDIT.md
@@ -1,77 +1,44 @@
-# Implementation Audit (v1.1.x Stabilization Pass)
+# Implementation Audit — v1.2.0 Candidate
 
-## 1) Implemented Algorithms by Language
+## Current capability
 
-| Algorithm | C++ | C# | Status |
+| Area | C++ | C# | Maturity |
 |---|:---:|:---:|---|
-| Cotan Laplacian | ✅ | ✅ | **Partial** |
-| Mean Curvature Flow | ✅ | ✅ | **Partial** |
-| Discrete Gaussian Curvature | ✅ | ✅ | **Partial** |
-| Conformal Parameterization | ✅ | ✅ | **Partial / Experimental** |
-| Heat Method | ✅ | ✅ | **Partial / Experimental** |
-| Hodge Decomposition | ✅ | ✅ | **Experimental** |
-
-### Notes
-- C# `CotanLaplacian` previously used a fixed placeholder weight; now wired through edge cotangent computation, still requiring deeper validation on irregular meshes.
-- C# `HeatMethod` still has a placeholder divergence stage.
-- C# `ConformalParameterization.BoundaryCircle` still uses a partial constrained solve approach.
-- C++ `HodgeDecomposition` includes simplified Hodge star and placeholder tree-cotree behavior.
-
-## 2) Missing / Partial Algorithms
-
-- ARAP deformation: **Planned**
-- Reusable Poisson solver API: **Planned** (Poisson solve exists only as helper path in cotan module)
-- Robust harmonic basis generation: **Partial/Experimental**
-- Full DEC operator validation suite: **Partial**
-
-## 3) Build Status
-
-| Component | Status | Evidence |
-|---|---|---|
-| C++ | Improved, now configures with existing tests list | Fixed broken test target references in `src/cpp/tests/CMakeLists.txt` |
-| C# | Builds cleanly | `dotnet build --configuration Release` |
-| Python | Minimal utilities only | `examples/python/visualize_mesh.py` |
-| Web/WASM | Workflow exists; demo pages available | `web/wasm-demo.html`, `web/wasm-benchmark.html` |
-
-## 4) Test Status / Gaps
-
-### Current strengths
-- Mesh construction/connectivity checks.
-- Laplacian dimensions, row sums, and symmetry checks.
-- Gauss-Bonnet sanity checks.
-
-### Gaps
-- Degenerate triangle stress tests are limited.
-- Invalid/non-manifold topology coverage remains limited.
-- Heat method and hodge decomposition need stronger numerical regression tests.
-- Cross-language parity tests are not formalized.
-
-## 5) README/Docs Drift Found and Corrected
-
-Corrected claims:
-- Removed “production-ready / complete / 95%+ coverage” style overclaims.
-- Removed references to missing `web/index.html`.
-- Corrected chapter and assignment availability references.
-- Added explicit maturity labels: **Complete / Partial / Experimental / Planned**.
-
-## 6) Numerical and Geometric Correctness Risks
-
-1. Orientation assumptions in halfedge traversal remain strict in many operators.
-2. Boundary and non-manifold treatment remains incomplete for advanced algorithms.
-3. Sparse solves do not consistently include rank-deficiency handling and conditioning diagnostics.
-4. Heat method divergence integration in C# remains incomplete.
-5. Hodge stars in both languages include simplified approximations.
-
-## 7) Priority Technical Debt
-
-1. Topology validation API (manifoldness, orientation consistency, duplicate edges).
-2. Robust boundary halfedge handling in both language cores.
-3. Centralized epsilon/tolerance policy for geometric predicates.
-4. Unified Poisson/linear-solve abstraction with failure diagnostics.
-5. Broader algorithm verification suite (sphere/grid/open meshes/degenerates).
-
-## 8) Suggested Roadmap Sequence
-
-1. **1.1.x stabilization**: mesh validation, tests, docs honesty, CI reliability.
-2. **1.2.0 feature expansion**: Poisson infrastructure + ARAP scaffold (explicitly experimental).
-3. **Post-1.2**: stronger DEC operator completeness, parity tests, richer tutorials and visual diagnostics.
+| Explicit manifold boundary topology | Yes | Yes | Validated on closed and disk fixtures |
+| Cotan Laplacian and barycentric mass | Yes | Yes | Symmetric assembly; broader conditioning tests needed |
+| Constrained Poisson solve | Yes | Yes | Dense constraint elimination; suitable for educational-scale meshes |
+| Gaussian curvature | Yes | Yes | Interior and boundary angle defects; Gauss–Bonnet tests |
+| Mean curvature flow | Yes | Yes | Implemented; solver diagnostics and boundary policies need expansion |
+| Boundary-circle parameterization | Yes | Yes | Ordered, chord-length boundary with constrained harmonic solve |
+| Heat Method | Yes | Yes | Heat, normalized face gradient, weak divergence, anchored Poisson |
+| Hodge decomposition | Partial | Partial | Decomposition exists; harmonic bases and full DEC validation deferred |
+| Interactive web workbench | JS + optional WASM | — | Reference/educational surface |
+
+## Correctness changes in this release
+
+- Every manifold edge owns two halfedges; open edges receive an explicit
+  boundary twin and boundary halfedges form closed loops.
+- Duplicate directed edges, non-manifold edges, invalid indices, degenerate
+  faces, and incomplete pointer relations are rejected or reported.
+- Cotangent weights are evaluated at the angle opposite each edge and inserted
+  symmetrically.
+- Boundary Gaussian curvature uses the \(\pi-\sum\theta\) defect, so disk
+  meshes satisfy Gauss–Bonnet.
+- Singular Poisson systems are anchored through explicit Dirichlet constraints.
+- The C# Heat Method no longer returns the zero-divergence placeholder result.
+
+## Deliberately deferred
+
+- True least-squares conformal maps (the C++ entry point fails explicitly
+  instead of presenting a harmonic map as LSCM).
+- Harmonic one-form basis construction and tree–cotree generators.
+- ARAP deformation.
+- Production-scale sparse constraint elimination, preconditioners, and
+  cross-language golden datasets.
+
+## Verification
+
+- Python: four dependency-free parser/topology tests.
+- JavaScript: syntax and deployed interaction checks.
+- Native compilation: required through the C++, C#, and WASM GitHub Actions
+  matrices because those toolchains are not available in the recovery runtime.
diff --git a/docs/status/NEXT_RELEASE_PLAN.md b/docs/status/NEXT_RELEASE_PLAN.md
@@ -1,42 +1,26 @@
 # Next Release Plan
 
-## Recommended Version Bump
+## Release decision
 
-**Recommend: `1.1.1`**
+The current branch is a **v1.2.0 candidate**. It crosses the minor-release
+threshold by adding explicit boundary topology, reusable constrained solves,
+implemented Heat divergence, and a new interactive web application.
 
-Reasoning:
-- This pass focuses on stabilization, test/build reliability fixes, and documentation correctness.
-- No intentional breaking API redesign was introduced.
-- Major new capabilities like ARAP/Poisson infrastructure are not yet complete enough for `1.2.0`.
+## Release gates
 
-## Included in this stabilization pass
+1. All C++, C#, Python, and WASM workflows pass on the pull request.
+2. Closed tetrahedron and open disk invariants pass in both language cores.
+3. Cotan matrices remain symmetric with near-zero row sums.
+4. Open-disk curvature has a near-zero Gauss–Bonnet residual.
+5. The deployed workbench loads at both `/` and `/web/index.html`.
+6. No documentation describes deferred LSCM, harmonic bases, or ARAP as complete.
 
-- C++ build/test reliability fixes (test target correctness, warning policy improvements).
-- C# mesh robustness improvements and defensive traversal safety.
-- Test updates for oriented tetrahedra and invalid index rejection.
-- CI workflow alignment (action versions, .NET version, test path correctness).
-- Documentation audit and maturity relabeling.
+## Post-1.2 priorities
 
-## Outstanding Risks
+1. Establish versioned cross-language mesh fixtures and golden outputs.
+2. Replace dense constraint elimination with sparse reduced systems.
+3. Implement and validate true LSCM.
+4. Implement tree–cotree generators and harmonic bases.
+5. Add ARAP only after solver and parity infrastructure are stable.
 
-- Heat method and hodge decomposition remain partial/experimental.
-- Non-manifold and severe degeneracy handling is still incomplete.
-- Cross-language parity and numerical baseline tests are still limited.
-
-## Suggested GitHub Issues
-
-1. Add explicit mesh topology validator (orientation, manifoldness, duplicates).
-2. Add Poisson solver API with Dirichlet constraints and tests.
-3. Complete C# heat-method divergence stage.
-4. Improve Hodge star and harmonic basis implementations.
-5. Add stress tests for open meshes, disconnected meshes, and near-degenerate triangles.
-
-## Proposed Milestones
-
-### Milestone: v1.1.1
-- Reliability/documentation/test integrity fixes only.
-
-### Milestone: v1.2.0
-- Poisson solver infrastructure
-- ARAP scaffold
-- Expanded algorithm validation suite
+These are intentionally separate from the 1.2.0 release candidate.