diff --git a/docs_build/dev/ProjectInstructions/README.txt b/docs_build/dev/ProjectInstructions/README.txt
index 1276f0695..54e708e9c 100644
--- a/docs_build/dev/ProjectInstructions/README.txt
+++ b/docs_build/dev/ProjectInstructions/README.txt
@@ -44,3 +44,4 @@ READ THIS FIRST
 Addendum index:
 - Canonical Repository Structure: project-instructions/addendums/canonical-repository-structure.md
 - Test Structure Standardization: project-instructions/addendums/test-structure-standardization.md
+- Legacy Migration Policy: project-instructions/addendums/legacy-migration-policy.md
diff --git a/project-instructions/addendums/legacy-migration-policy.md b/project-instructions/addendums/legacy-migration-policy.md
new file mode 100644
index 000000000..5e43679f4
--- /dev/null
+++ b/project-instructions/addendums/legacy-migration-policy.md
@@ -0,0 +1,33 @@
+# Legacy Migration Policy
+
+## Purpose
+
+Reduce technical debt incrementally during normal development.
+
+## Migration Trigger
+
+Migration review is required when any of these actions touch legacy files:
+
+- File modified
+- File renamed
+- Bug fix
+- Enhancement
+- Test modification
+
+## Migration Process
+
+1. Review JS location.
+2. Review CSS location.
+3. Review test location.
+4. Move touched files into canonical structure.
+5. Update imports.
+6. Update tests.
+7. Remove legacy references.
+
+## Rules
+
+- Legacy files may only be deleted when no active references remain.
+- Temporary bridge code must contain `TEMPORARY_MIGRATION` and a removal plan.
+- No new scattered JS locations.
+- No new scattered CSS locations.
+- No new scattered test locations.