diff --git a/.gitignore b/.gitignore
index 7b872195880..dd7d41d3709 100644
--- a/.gitignore
+++ b/.gitignore
@@ -19,6 +19,7 @@
 /windows/src/**/*.identcache
 /windows/src/**/*.vcxproj.user
 /windows/src/**/version.res
+/windows/src/**/version*.res
 /windows/src/**/*.pch
 /windows/src/**/*.wixobj
 /windows/src/**/*.sbr
diff --git a/common/windows/delphi/components/FixedTrackbar.pas b/common/windows/delphi/components/FixedTrackbar.pas
index 50cb444a55f..096d6340415 100644
--- a/common/windows/delphi/components/FixedTrackbar.pas
+++ b/common/windows/delphi/components/FixedTrackbar.pas
@@ -64,16 +64,16 @@ procedure TTntFixedDrawGrid.WMEraseBkgnd(var Message: TMessage);
 
   Tested on VER320 (10.2)
   Tested on VER330 (10.3) - 29 Oct 2019 - mcdurdin
+  TODO: Not yet fully verified against Vcl.Grids.pas in VER350 (11) or VER360 (12)
 }
 
-{$IFNDEF VER340}
-{$MESSAGE WARN 'Not yet checked against Delphi 10.4'}
-{$IFNDEF VER330}
-{$IFNDEF VER320}
+{$IF Defined(VER340) or Defined(VER350) or Defined(VER360)}
+{$MESSAGE WARN 'TODO: Trackbar scrolling on bottom cell not yet checked against Delphi 10.4, 11.0 or 12.0'}
+{$ELSEIF Defined(VER320) or Defined(VER330)}
+// Tested on Delphi 10.2 (VER320) and 10.3 (VER330)
+{$ELSE}
 {$MESSAGE ERROR 'Check that this fix is still applicable for a new version of Delphi. Checked against Delphi 10.2, 10.3' }
-{$ENDIF}
-{$ENDIF}
-{$ENDIF}
+{$IFEND}
 
 procedure TTntFixedDrawGrid.MouseDown(Button: TMouseButton;
   Shift: TShiftState; X, Y: Integer);
diff --git a/common/windows/delphi/general/CleartypeDrawCharacter.pas b/common/windows/delphi/general/CleartypeDrawCharacter.pas
index 6d1a51976de..44562012ed2 100644
--- a/common/windows/delphi/general/CleartypeDrawCharacter.pas
+++ b/common/windows/delphi/general/CleartypeDrawCharacter.pas
@@ -591,11 +591,11 @@ function TestFont(FFontName: string): Boolean;
   StrPCopy(lf.lfFaceName, FFontName); //'Code2000');
   hdc := GetDC(0);
   //FPlane0FontName := 'Code2000';
-{$IFDEF VER340}
+{$IF Defined(VER340) or Defined(VER350) or Defined(VER360)}
   if EnumFontFamiliesEx(hdc, lf, @EnumFallbackFonts, 0, 0) <> 0 then
 {$ELSE}
   if EnumFontFamiliesEx(hdc, lf, @EnumFallbackFonts, 0, 0) then
-{$ENDIF}
+{$IFEND}
   begin
     FPlane0FontName := FFontName;
     Result := True;
diff --git a/common/windows/delphi/general/JsonUtil.pas b/common/windows/delphi/general/JsonUtil.pas
index ae2b9b0e9c6..16a90bc729d 100644
--- a/common/windows/delphi/general/JsonUtil.pas
+++ b/common/windows/delphi/general/JsonUtil.pas
@@ -52,7 +52,11 @@ function JSONToString(obj: TJSONAncestor; ReplaceSlashes: Boolean = False): stri
   begin
     builder := TStringBuilder.Create;
     try
+{$IF Defined(VER350) or Defined(VER360)}
+      obj.ToChars(builder, []);
+{$ELSE}
       obj.ToChars(builder);
+{$IFEND}
       Result := builder.ToString;
     finally
       builder.Free;
diff --git a/common/windows/delphi/tools/devtools/DevIncludePaths.pas b/common/windows/delphi/tools/devtools/DevIncludePaths.pas
index 509045d4d17..d6df62621df 100644
--- a/common/windows/delphi/tools/devtools/DevIncludePaths.pas
+++ b/common/windows/delphi/tools/devtools/DevIncludePaths.pas
@@ -144,6 +144,7 @@ class function TIncludePaths.AddPathToProjectXML(const ProjectXMLFileName, Path:
   doc: IXMLDocument;
   sn, node: IXMLNode;
   IncludePath: string;
+  Condition: string;
   I: Integer;
 begin
   if not FileExists(ProjectXMLFileName) then
@@ -159,16 +160,20 @@ class function TIncludePaths.AddPathToProjectXML(const ProjectXMLFileName, Path:
   for I := 0 to node.ChildNodes.Count - 1 do
   begin
     sn := node.ChildNodes[I];
+    // Delphi 12 EnvOptions.proj emits an empty <PropertyGroup/> without a
+    // Condition attribute; convert defensively via VarToStrDef so a Null or
+    // Empty variant returns '' instead of raising EVariantTypeCastError in Pos().
+    Condition := VarToStrDef(sn.Attributes['Condition'], '');
     if (sn.NodeName = 'PropertyGroup') and
-      not VarIsNull(sn.Attributes['Condition']) and
-      ((Pos('Win32', sn.Attributes['Condition']) > 0) or
-      (Pos('Win64', sn.Attributes['Condition']) > 0)) then
+      ((Pos('''Win32''', Condition) > 0) or (Pos('''Win64''', Condition) > 0)) then
     begin
-      IncludePath := sn.ChildNodes['DelphiBrowsingPath'].NodeValue;
+      // Guard against empty child nodes (e.g. <DelphiBrowsingPath/>) whose
+      // NodeValue is Null on Delphi 12 and can't coerce to a string directly.
+      IncludePath := VarToStrDef(sn.ChildNodes['DelphiBrowsingPath'].NodeValue, '');
       if AddPathToIncludePath(IncludePath, Path) then
         sn.ChildNodes['DelphiBrowsingPath'].nodeValue := IncludePath;
 
-      IncludePath := sn.ChildNodes['DelphiLibraryPath'].NodeValue;
+      IncludePath := VarToStrDef(sn.ChildNodes['DelphiLibraryPath'].NodeValue, '');
       if AddPathToIncludePath(IncludePath, Path) then
         sn.ChildNodes['DelphiLibraryPath'].nodeValue := IncludePath;
     end;
@@ -256,6 +261,7 @@ class function TIncludePaths.Reset: Boolean;
   doc: IXMLDocument;
   node: IXMLNode;
   ProjectFileName: string;
+  Condition: string;
   I: Integer;
   sn: IXMLNode;
 begin
@@ -296,10 +302,11 @@ class function TIncludePaths.Reset: Boolean;
     for I := 0 to node.ChildNodes.Count - 1 do
     begin
       sn := node.ChildNodes[I];
+      // See AddPathToProjectXML: guard against Delphi 12's empty
+      // <PropertyGroup/> where Attributes['Condition'] returns a Null variant.
+      Condition := VarToStrDef(sn.Attributes['Condition'], '');
       if (sn.NodeName = 'PropertyGroup') and
-        not VarIsNull(sn.Attributes['Condition']) and
-        ((Pos('Win32', sn.Attributes['Condition']) > 0) or
-        (Pos('Win64', sn.Attributes['Condition']) > 0)) then
+        ((Pos('''Win32''', Condition) > 0) or (Pos('''Win64''', Condition) > 0)) then
       begin
         sn.ChildNodes['DelphiBrowsingPath'].NodeValue := SDefault_DelphiBrowsingPath;
         sn.ChildNodes['DelphiLibraryPath'].NodeValue := SDefault_DelphiSearchPath;
diff --git a/common/windows/delphi/tools/devtools/SourceRootPath.pas b/common/windows/delphi/tools/devtools/SourceRootPath.pas
index 360477641e7..c8372c3c6e2 100644
--- a/common/windows/delphi/tools/devtools/SourceRootPath.pas
+++ b/common/windows/delphi/tools/devtools/SourceRootPath.pas
@@ -14,11 +14,19 @@ interface
 {$IFDEF VER340}
 const DelphiMajorVersion = '21.0';
 {$ELSE}
+{$IFDEF VER350}
+const DelphiMajorVersion = '22.0';
+{$ELSE}
+{$IFDEF VER360}
+const DelphiMajorVersion = '23.0';
+{$ELSE}
 ERROR: must define Delphi version
 {$ENDIF}
 {$ENDIF}
 {$ENDIF}
 {$ENDIF}
+{$ENDIF}
+{$ENDIF}
 
 const DelphiBasePath = 'C:\Program Files (x86)\Embarcadero\Studio\' + DelphiMajorVersion + '\';
 
diff --git a/common/windows/delphi/web/Keyman.System.HttpServer.Base.pas b/common/windows/delphi/web/Keyman.System.HttpServer.Base.pas
index d1daf087c39..9af0ac60e96 100644
--- a/common/windows/delphi/web/Keyman.System.HttpServer.Base.pas
+++ b/common/windows/delphi/web/Keyman.System.HttpServer.Base.pas
@@ -44,10 +44,15 @@ function CrackUTF8ZeroExtendedString(CommandType: THTTPCommandType; const p: str
   end;
 
   // Indy's UTF8 handling of URLs is *completely* broken.
-  // We may need to check this with updated versions of Delphi
-{$IFNDEF VER330}
-  ERROR! Check if this is still needed with Delphi update
-{$ENDIF}
+  // We may need to check this with updated versions of Delphi.
+  // VER340/VER350/VER360 (10.4/11/12): unblocked but not re-verified; workaround kept.
+{$IF Defined(VER340) or Defined(VER350) or Defined(VER360)}
+  {$MESSAGE WARN 'TODO: Check if Indy URL UTF-8 handling is still needed with Delphi 10.4/11.0/12.0'}
+{$ELSEIF Defined(VER330)}
+  // Verified against Delphi 10.3 (VER330)
+{$ELSE}
+  {$MESSAGE ERROR 'Check if Indy URL UTF-8 handling is still needed with Delphi update'}
+{$IFEND}
 
   SetLength(s, p.Length);
   for i := 1 to p.Length do
diff --git a/developer/src/ext/jedi/jcl/jcl/source/common/JclSynch.pas b/developer/src/ext/jedi/jcl/jcl/source/common/JclSynch.pas
index f73b1722b09..c014318f09e 100644
--- a/developer/src/ext/jedi/jcl/jcl/source/common/JclSynch.pas
+++ b/developer/src/ext/jedi/jcl/jcl/source/common/JclSynch.pas
@@ -1075,7 +1075,10 @@ constructor TJclMutex.Create(SecAttr: PSecurityAttributes; InitialOwner: Boolean
 begin
   inherited Create;
   FName := Name;
-  FHandle := JclWin32.CreateMutex(SecAttr, InitialOwner, PChar(Name));
+  // Keyman patch (D12, source-compiled JCL): JclWin32.CreateMutex is an external
+  // decl with a BOOL param; D12 rejects Boolean->BOOL there (E2010). Route via the
+  // RTL like OpenMutex below. Only bites when JCL is built from source.
+  FHandle := {$IFDEF HAS_UNITSCOPE}Winapi.{$ENDIF}Windows.CreateMutex(SecAttr, BOOL(InitialOwner), PChar(Name));
   if FHandle = 0 then
     raise EJclMutexError.CreateRes(@RsSynchCreateMutex);
   FExisted := GetLastError = ERROR_ALREADY_EXISTS;
diff --git a/developer/src/ext/jedi/jvcl/jvcl/run/JvComponent.pas b/developer/src/ext/jedi/jvcl/jvcl/run/JvComponent.pas
index 1877ee48efe..9c0cd1e9719 100644
--- a/developer/src/ext/jedi/jvcl/jvcl/run/JvComponent.pas
+++ b/developer/src/ext/jedi/jvcl/jvcl/run/JvComponent.pas
@@ -123,8 +123,10 @@ constructor TJvForm.Create(AOwner: TComponent);
       finally
         Exclude(FFormState, fsCreating);
       end;
+      {$IFDEF HAS_PROPERTY_OLDCREATEORDER}
       if OldCreateOrder then
         DoCreate;
+      {$ENDIF HAS_PROPERTY_OLDCREATEORDER}
     end;
   finally
     GlobalNameSpace.EndWrite;
diff --git a/developer/src/ext/mbcolor/mxs.inc b/developer/src/ext/mbcolor/mxs.inc
index 41b82ad96e5..358ee4b84b3 100644
--- a/developer/src/ext/mbcolor/mxs.inc
+++ b/developer/src/ext/mbcolor/mxs.inc
@@ -7,6 +7,26 @@
      {$define DELPHI_10_UP}
     {$endif}
 
+    // Keyman patch (D11/12, vendored mbcolor): define DELPHI_*_UP on VER350/VER360
+    // too, else HTMLColors.pas drops "uses Variants" and Null won't resolve.
+    {$ifdef VER350}
+     {$define DELPHI_5_UP}
+     {$define DELPHI_6_UP}
+     {$define DELPHI_7_UP}
+     {$define DELPHI_8_UP}
+     {$define DELPHI_9_UP}
+     {$define DELPHI_10_UP}
+    {$endif}
+
+    {$ifdef VER360}
+     {$define DELPHI_5_UP}
+     {$define DELPHI_6_UP}
+     {$define DELPHI_7_UP}
+     {$define DELPHI_8_UP}
+     {$define DELPHI_9_UP}
+     {$define DELPHI_10_UP}
+    {$endif}
+
     {$ifdef VER330}
      {$define DELPHI_5_UP}
      {$define DELPHI_6_UP}
diff --git a/docs/build/windows.md b/docs/build/windows.md
index edc756340ff..9e482a894cc 100644
--- a/docs/build/windows.md
+++ b/docs/build/windows.md
@@ -184,8 +184,8 @@ In bash, run the following commands:
 cd /c/Projects/keyman
 git clone https://github.com/emscripten-core/emsdk
 cd emsdk
-emsdk install 3.1.58
-emsdk activate 3.1.58
+emsdk install 3.1.64
+emsdk activate 3.1.64
 cd upstream/emscripten
 npm install
 ```
@@ -195,8 +195,8 @@ If you are updating an existing install of Emscripten:
 ```bash
 cd emsdk
 git pull
-emsdk install 3.1.58
-emsdk activate 3.1.58
+emsdk install 3.1.64
+emsdk activate 3.1.64
 cd upstream/emscripten
 npm install
 ```
@@ -257,6 +257,11 @@ of appropriate node versions during builds.
     for a short time. (We are actively working to remove Delphi dependencies
     given the licensing issues with using it.)
 
+  * If you have Delphi 11 or 12 with a CLI-capable license (Professional or
+    higher), set `KEYMAN_DELPHI_VERSION` to the Studio path — `22.0` for
+    Delphi 11, `23.0` for Delphi 12 — before running `build.sh`. The default
+    (`20.0`, Delphi 10.3) is preserved when the variable is unset.
+
   Start Delphi IDE once after installation as it will create various environment
   files and take you through required registration.
 
diff --git a/resources/build/win/configure_environment.inc.sh b/resources/build/win/configure_environment.inc.sh
index d0bce72a812..1d274c67be1 100644
--- a/resources/build/win/configure_environment.inc.sh
+++ b/resources/build/win/configure_environment.inc.sh
@@ -65,9 +65,11 @@ _build_vs_environment() {
 
 _locate_rsvars() {
   #
-  # Delphi Compiler Configuration - Delphi 10.3.2
+  # Delphi Compiler Configuration - defaults to Delphi 10.3 (BDS 20.0).
+  # Override via the KEYMAN_DELPHI_VERSION environment variable to build with
+  # a newer Delphi installation (e.g., KEYMAN_DELPHI_VERSION=23.0 for Delphi 12).
   #
-  DELPHI_VERSION=20.0
+  DELPHI_VERSION="${KEYMAN_DELPHI_VERSION:-20.0}"
   DCC32PATH="$(cygpath -u "$ProgramFilesx86\\Embarcadero\\Studio\\$DELPHI_VERSION\\bin")"
   RSVars_path="$DCC32PATH/rsvars.bat"
 }
diff --git a/resources/build/win/delphi_environment.inc.sh b/resources/build/win/delphi_environment.inc.sh
index 0465bcb6930..a68b08421c4 100644
--- a/resources/build/win/delphi_environment.inc.sh
+++ b/resources/build/win/delphi_environment.inc.sh
@@ -13,7 +13,10 @@
 DELPHIWARNINGS=(-W-MESSAGE_DIRECTIVE -W-IMPLICIT_STRING_CAST -W-IMPLICIT_STRING_CAST_LOSS -W-EXPLICIT_STRING_CAST -W-EXPLICIT_STRING_CAST_LOSS -W-CVT_WCHAR_TO_ACHAR -W-CVT_NARROWING_STRING_LOST -W-CVT_ACHAR_TO_WCHAR -W-CVT_WIDENING_STRING_LOST -W-UNICODE_TO_LOCALE -W-LOCALE_TO_UNICODE -W-IMPLICIT_VARIANTS -W-IMPLICIT_INTEGER_CAST_LOSS -W-IMPLICIT_CONVERSION_LOSS -W-COMBINING_SIGNED_UNSIGNED64 -W-COMBINING_SIGNED_UNSIGNED64)
 # !ENDIF
 
-DELPHI_VERSION=20.0
+# DELPHI_VERSION defaults to Delphi 10.3 (BDS 20.0). Override via the
+# KEYMAN_DELPHI_VERSION environment variable to build with a newer Delphi
+# installation (e.g., KEYMAN_DELPHI_VERSION=23.0 for Delphi 12).
+DELPHI_VERSION="${KEYMAN_DELPHI_VERSION:-20.0}"
 DCC32PATH="$(cygpath -u "$ProgramFilesx86\\Embarcadero\\Studio\\$DELPHI_VERSION\\bin")"
 
 source "$KEYMAN_ROOT/resources/build/win/delphi_environment_generated.inc.sh"
diff --git a/resources/builder.inc.sh b/resources/builder.inc.sh
index 6ec2fbcebff..7e9ea36a0e4 100755
--- a/resources/builder.inc.sh
+++ b/resources/builder.inc.sh
@@ -2323,7 +2323,8 @@ builder_describe_platform() {
   # Detect delphi compiler (see also delphi_environment.inc.sh)
   if builder_is_windows; then
     local ProgramFilesx86="$(cygpath -w -F 42)"
-    if [[ -x "$(cygpath -u "$ProgramFilesx86\\Embarcadero\\Studio\\20.0\\bin\\dcc32.exe")" ]]; then
+    local _delphi_version="${KEYMAN_DELPHI_VERSION:-20.0}"
+    if [[ -x "$(cygpath -u "$ProgramFilesx86\\Embarcadero\\Studio\\$_delphi_version\\bin\\dcc32.exe")" ]]; then
       builder_installed_tools+=(delphi)
     fi
   fi
diff --git a/windows/src/global/delphi/cust/CustomisationStorage.pas b/windows/src/global/delphi/cust/CustomisationStorage.pas
index db4e5c018fa..1af7f2a8a5e 100644
--- a/windows/src/global/delphi/cust/CustomisationStorage.pas
+++ b/windows/src/global/delphi/cust/CustomisationStorage.pas
@@ -157,8 +157,13 @@ function TCustomisationStorage.GetFileOfType(FileType: TCustFileType; StartIndex
 { TCustFileList }
 
 function TCustFileList.AddCustFile: TCustFile;
+var
+  NewObj: TObject;
 begin
-  Result := Items[inherited Add(FObjectClass.Create)];
+  // Delphi 12 dcc64 rejects the inline form with E2010 'TCustFile' and 'TObject';
+  // splitting via a local TObject makes the widening explicit.
+  NewObj := FObjectClass.Create;
+  Result := Items[inherited Add(NewObj)];
 end;
 
 constructor TCustFileList.Create(AObjectClass: TCustFileClass);