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+# Strict Qt5-to-Qt6 Migration and Regression Verification
+
+This is an implementation and validation task. Work autonomously, keep changes minimal, and do not modify unrelated files.
+
+## Fixed scope
+
+Work only on branch:
+
+`feature/regression-arcgis300-symbology-migration`
+
+Compare these exact directories recursively:
+
+- Qt5 reference, read-only:
+  `./qt-migration-legatus/qt5-before/qt5-legatus-legacy/`
+- Qt6 target, writable:
+  `./qt-migration-legatus/qt6-after/qt6-migrated-legatus/`
+
+Do not swap, reinterpret, or invent paths. Never modify the Qt5 reference tree.
+
+## Mandatory Docker and build rules
+
+All analysis, comparison, source changes, builds, and tests must run inside Docker. Do not run compilers, CMake, Make, Ninja, CTest, Python tests, or application tests directly on the host.
+
+Use only this authoritative build and test script:
+
+`./qt6-migration-pipeline/qt-migration-legatus/qt6-after/qt6-migrated-legatus/new_docker_build.sh`
+
+Do not use another script or invent an alternative build procedure.
+
+Before doing any project analysis or modification:
+
+1. Read the complete script.
+2. Verify its actual options, defaults, environment variables, Docker mounts, build groups, targets, test commands, logs, and failure behavior.
+3. Build the script's prebuilt Docker image.
+4. Use that same freshly built image for all subsequent work.
+
+Only use options that actually exist in the script. In particular, verify the real behavior of:
+
+- `--build-prebuilt-image`
+- `--use-prebuilt-image`
+- `--docker-image`
+- `--tests-only`
+- `--integration-test`
+- `--no-ctest`
+- `--group1` through `--group12`
+- `--build-viewer-only`
+- `--arcgis`
+- `--grantlee`
+- `--codification`
+- `--cmake_build_flags`
+
+If the image cannot be built, stop and report the exact command, exit code, error, and blocker.
+
+## Tests
+
+Existing tests are located at:
+
+`./qt6-migration-pipeline/qt-migration-legatus/qt6-after/qt6-migrated-legatus/tests`
+
+Before adding tests, inspect and follow the existing directory structure, naming convention, CMake registration, and execution pattern.
+
+Every new regression test must be placed in that same `tests` tree and registered through the existing test mechanism. Do not create tests elsewhere unless the repository convention demonstrably requires it.
+
+## Verification procedure
+
+1. Compare the Qt5 and Qt6 trees recursively and functionally, not only by filename.
+2. Classify every relevant difference as:
+   - correctly migrated
+   - missing migration
+   - regression or behavioral difference
+   - intentionally changed
+   - intentionally removed
+   - build/packaging-only
+   - generated or obsolete
+   - test-related
+   - unclear or blocked
+3. Check source files, headers, APIs, CMake targets, dependencies, resources, UI files, plugins, configuration, code generation, tests, and active Qt5 references.
+4. Check ArcGIS 300 Symbology with the appropriate `--arcgis` configuration.
+5. Run the relevant build and test groups through the authoritative script. Prefer grouped execution when supported by the script.
+6. Record every command, option, group, target, test, exit code, and log path.
+
+## Regression handling
+
+For every reproducible regression or missing migration:
+
+1. Reproduce it inside Docker.
+2. Identify the root cause using the Qt5/Qt6 comparison and build/test logs.
+3. Apply the smallest valid fix in the Qt6 tree or required test/build files.
+4. Add a deterministic regression test under the required `tests` directory.
+5. Register it using the existing CMake/test convention.
+6. Re-run the affected build group and test through the authoritative script.
+7. Re-run all other relevant tests affected by the change.
+
+Do not disable tests or targets, hide failures with `--no-ctest`, use dummy implementations, or replace generated outputs manually.
+
+## Success criteria
+
+The task succeeds only if:
+
+- the prebuilt Docker image was built before project work began;
+- all project analysis, changes, builds, and tests ran inside Docker;
+- every build and regression test used the authoritative script;
+- all relevant build groups and tests were executed and passed;
+- the Qt5/Qt6 comparison was complete and every relevant difference was classified;
+- required Qt5 functionality exists in Qt6 or has a documented, justified replacement;
+- ArcGIS 300 Symbology was validated, or the exact blocker and unvalidated scope are reported;
+- every fixed regression has a deterministic regression test in the required test tree;
+- the Qt5 tree is unchanged;
+- no tests, targets, or functionality were disabled to claim success.
+
+A skipped, failed, or unavailable relevant check means the result cannot be reported as fully validated.
+
+## Final report
+
+Provide a factual report containing:
+
+- status: `VALIDATED`, `PARTIALLY VALIDATED`, or `BLOCKED`;
+- branch and exact directories checked;
+- Docker image name, image-build command, exit code, and result;
+- authoritative script path and verified options;
+- commands, groups, targets, tests, exit codes, and log paths;
+- classified Qt5/Qt6 differences;
+- regressions, root causes, fixes, and added tests;
+- ArcGIS 300 Symbology result;
+- changed files;
+- skipped or failed checks with exact blockers;
+- remaining risks.
+
+Do not claim complete migration or regression-free behavior without concrete, reproducible evidence.
diff --git a/qt-migration-legatus b/qt-migration-legatus
index c39dbec31..bec2a14ce 160000
--- a/qt-migration-legatus
+++ b/qt-migration-legatus
@@ -1 +1 @@
-Subproject commit c39dbec31ff5c59712669bb765485e2412337dc8
+Subproject commit bec2a14ce26cf3c0dc73fc90a83315f086bcce70