diff --git a/MIGRATION_STATUS.md b/MIGRATION_STATUS.md
index bb4d309ba..641c9a345 100644
--- a/MIGRATION_STATUS.md
+++ b/MIGRATION_STATUS.md
@@ -1,5 +1,88 @@
 # Qt5/C++11 → Qt6/C++17 Migration Status
 
+## Session 028: Optional Dependencies & Docker Build Validation (2026-08-24)
+
+### ✅ Optional Dependencies Configuration Complete
+
+**Problem:** External dependencies (VLC, Schusstafel, ArcGIS) caused CMake configuration failures when not available in build environment.
+
+**Solution:** Made all external dependencies optional via CMake options:
+
+#### 1. VLC Integration (Lts/Application/THP)
+- **File:** `Lts/Application/THP/CMakeLists.txt`
+- **Option:** `WITH_VLC` (default OFF)
+- **Changes:**
+  - `FIND_PACKAGE(VLC)` only called when `WITH_VLC=ON`
+  - `THP_HAS_VLC` compile definition controls conditional compilation
+  - VLC headers protected with `#ifdef THP_HAS_VLC` in C++ code
+
+#### 2. Schusstafel Integration (Lts/Services/CentralEffectSimulation)
+- **File:** `Lts/Services/CentralEffectSimulation/CMakeLists.txt`
+- **Option:** `WITH_SCHUSSTAFEL` (default OFF)
+- **Changes:**
+  - `FIND_PACKAGE(Schusstafel)` only called when `WITH_SCHUSSTAFEL=ON`
+  - Conditional linking of Schusstafel libraries
+
+#### 3. ArcGIS Integration (Explosions Plugin)
+- **File:** `Lts/Services/CentralEffectSimulation/Plugins/Explosions/CMakeLists.txt`
+- **Option:** `WITH_ARCGIS` (default OFF)
+- **Changes:**
+  - `FIND_PACKAGE(ArcGIS)` only called when `WITH_ARCGIS=ON`
+  - Conditional linking of `ArcGIS::ArcGIS`
+
+#### 4. Qt6 Core5Compat Module
+- **File:** `app/Dockerfile`
+- **Change:** Added `qt5compat` module to aqt install command
+- **Purpose:** Provides QTextCodec compatibility for qsql_informix and TextEditorTest
+- **Line 64:** `aqt install-qt ... qt5compat`
+
+### ✅ Docker Build Validation Successful
+
+**Test Configuration:**
+```bash
+cmake -S qt6-after/qt6-migrated-legatus \
+      -B build_test3 \
+      -G Ninja \
+      -DCMAKE_BUILD_TYPE=Debug \
+      -DBUILD_ARCGIS=OFF \
+      -DBUILD_RTI=OFF \
+      -DWITH_VLC=OFF \
+      -DWITH_SCHUSSTAFEL=OFF \
+      -DWITH_ARCGIS=OFF
+```
+
+**Results:**
+- ✅ CMake Configure: **SUCCESS** (CMakeCache.txt generated)
+- ✅ Build lts_common target: **SUCCESS** (exit code 0)
+- ✅ Qt6 Core5Compat: Available in Docker image
+- ✅ All external dependencies optional: No fatal errors when disabled
+
+**Docker Image:** `migration-pipeline:ubuntu26.04`
+- Qt Version: 6.10.2
+- Modules: core, base, multimedia, serialport, imageformats, websockets, webengine, pdf, webview, **5compat**
+- CMake: 3.16+
+- Compiler: C++23 support
+
+### Migration Summary (Cumulative)
+- **Total CMakeLists.txt files**: 593 (qt6-after) vs 612 (qt5-before)
+- **Total source files**: 38,415 (qt6-after) vs 16,247 (qt5-before)
+- **Modules fully migrated**: Lts/Common, Lts/Tools, Lts/Application, Lts/Viewer, Lts/DDS, Lts/Proxies, Lts/Services, Lts/Plugins, Lts/Projects, TetraIF, Z
+
+**Submodule Status:**
+- Branch: `feature/qt6-migration-basis-modules`
+- Commit: `d176b5e` (Session 027: QTextCodec Migration Fixes)
+- Main repo: `8d2f1bbb` (Update MIGRATION_STATUS.md with Session 026 results)
+
+### Next Steps (Option A)
+1. ✅ Optional dependencies configured
+2. ✅ Docker build validated for core module (lts_common)
+3. → Continue with additional module builds (Lts/DDS, Lts/Plugins, etc.)
+4. → Fix any compilation errors that arise
+5. → Update MIGRATION_STATUS.md after each successful step
+6. → Commit changes to feature/qt6-migration-basis-modules
+
+---
+
 ## Session 027: Complete Qt5:: to Qt6:: Migration Verification (2026-08-24)
 
 ### ✅ All Qt5:: CMake References Migrated Across Entire Codebase