diff --git a/src/backend/shared/utils/cpp/__tests__/generateCBlocksCode.test.ts b/src/backend/shared/utils/cpp/__tests__/generateCBlocksCode.test.ts
index 0c7d24fed..326977bec 100644
--- a/src/backend/shared/utils/cpp/__tests__/generateCBlocksCode.test.ts
+++ b/src/backend/shared/utils/cpp/__tests__/generateCBlocksCode.test.ts
@@ -1,7 +1,7 @@
 import type { PLCVariable } from '../../../../../middleware/shared/ports/types'
 import { generateCBlocksCode } from '../generateCBlocksCode'
 
-const makeScalarVar = (name: string, cls: 'input' | 'output', baseType: string): PLCVariable => ({
+const makeScalarVar = (name: string, cls: 'input' | 'output' | 'local', baseType: string): PLCVariable => ({
   name,
   class: cls,
   type: { definition: 'base-type', value: baseType },
@@ -10,7 +10,7 @@ const makeScalarVar = (name: string, cls: 'input' | 'output', baseType: string):
   debug: false,
 })
 
-const makeArrayVar = (name: string, cls: 'input' | 'output', baseType: string, dimension: string): PLCVariable => ({
+const makeArrayVar = (name: string, cls: 'input' | 'output' | 'local', baseType: string, dimension: string): PLCVariable => ({
   name,
   class: cls,
   type: {
@@ -120,17 +120,12 @@ describe('generateCBlocksCode', () => {
     expect(result).toContain('// comment about setup')
   })
 
-  it('filters variables by class (only input and output)', () => {
+  it('includes user local variables and excludes runtime-only locals', () => {
     const variables: PLCVariable[] = [
       makeScalarVar('inVar', 'input', 'INT'),
-      {
-        name: 'localVar',
-        class: 'local',
-        type: { definition: 'base-type', value: 'INT' },
-        location: '',
-        documentation: '',
-        debug: false,
-      },
+      makeScalarVar('localVar', 'local', 'INT'),
+      makeArrayVar('history', 'local', 'INT', '0..2'),
+      makeScalarVar('hasBeenInitialized', 'local', 'BOOL'),
       makeScalarVar('outVar', 'output', 'INT'),
     ]
     const code = 'void setup() { }\nvoid loop() { }'
@@ -138,10 +133,14 @@ describe('generateCBlocksCode', () => {
     const result = generateCBlocksCode([{ name: 'test', code, variables }])
 
     expect(result).toContain('#define inVar')
+    expect(result).toContain('#define localVar')
+    expect(result).toContain('#define history (vars->HISTORY)')
     expect(result).toContain('#define outVar')
-    expect(result).not.toContain('#define localVar')
+    expect(result).not.toContain('#define hasBeenInitialized')
     expect(result).toContain('#undef inVar')
+    expect(result).toContain('#undef localVar')
+    expect(result).toContain('#undef history')
     expect(result).toContain('#undef outVar')
-    expect(result).not.toContain('#undef localVar')
+    expect(result).not.toContain('#undef hasBeenInitialized')
   })
 })
diff --git a/src/backend/shared/utils/cpp/__tests__/generateCBlocksHeader.test.ts b/src/backend/shared/utils/cpp/__tests__/generateCBlocksHeader.test.ts
index 4f66166f9..40b555c0b 100644
--- a/src/backend/shared/utils/cpp/__tests__/generateCBlocksHeader.test.ts
+++ b/src/backend/shared/utils/cpp/__tests__/generateCBlocksHeader.test.ts
@@ -1,7 +1,7 @@
 import type { PLCVariable } from '../../../../../middleware/shared/ports/types'
 import { generateCBlocksHeader } from '../generateCBlocksHeader'
 
-const makeScalarVar = (name: string, cls: 'input' | 'output', baseType: string): PLCVariable => ({
+const makeScalarVar = (name: string, cls: 'input' | 'output' | 'local', baseType: string): PLCVariable => ({
   name,
   class: cls,
   type: { definition: 'base-type', value: baseType },
@@ -10,7 +10,7 @@ const makeScalarVar = (name: string, cls: 'input' | 'output', baseType: string):
   debug: false,
 })
 
-const makeArrayVar = (name: string, cls: 'input' | 'output', baseType: string, dimension: string): PLCVariable => ({
+const makeArrayVar = (name: string, cls: 'input' | 'output' | 'local', baseType: string, dimension: string): PLCVariable => ({
   name,
   class: cls,
   type: {
@@ -48,25 +48,22 @@ describe('generateCBlocksHeader', () => {
     expect(result).toContain('void myblock_loop(MYBLOCK_VARS *vars);')
   })
 
-  it('includes only input and output variables in the struct', () => {
+  it('includes user local variables and excludes runtime-only locals in the struct', () => {
     const variables: PLCVariable[] = [
       makeScalarVar('inVar', 'input', 'INT'),
-      {
-        name: 'localVar',
-        class: 'local',
-        type: { definition: 'base-type', value: 'BOOL' },
-        location: '',
-        documentation: '',
-        debug: false,
-      },
+      makeScalarVar('localVar', 'local', 'BOOL'),
+      makeArrayVar('history', 'local', 'INT', '0..2'),
+      makeScalarVar('hasBeenInitialized', 'local', 'BOOL'),
       makeScalarVar('outVar', 'output', 'BOOL'),
     ]
 
     const result = generateCBlocksHeader([{ name: 'test', variables }])
 
     expect(result).toContain('IEC_INT *INVAR;')
+    expect(result).toContain('IEC_BOOL *LOCALVAR;')
+    expect(result).toContain('IEC_INT *HISTORY;')
     expect(result).toContain('IEC_BOOL *OUTVAR;')
-    expect(result).not.toContain('LOCALVAR')
+    expect(result).not.toContain('HASBEENINITIALIZED')
   })
 
   it('generates declarations for multiple pous', () => {
diff --git a/src/backend/shared/utils/cpp/generateCBlocksCode.ts b/src/backend/shared/utils/cpp/generateCBlocksCode.ts
index 85bab8b31..8db31daa8 100644
--- a/src/backend/shared/utils/cpp/generateCBlocksCode.ts
+++ b/src/backend/shared/utils/cpp/generateCBlocksCode.ts
@@ -1,6 +1,8 @@
 import { generateStructMember, isArrayVariable } from '../../../../frontend/utils/PLC/array-codegen-helpers'
 import type { PLCVariable } from '../../../../middleware/shared/ports/types'
 
+import { getExposedCppVariables } from './shared'
+
 type CppPouData = {
   name: string
   code: string
@@ -26,17 +28,12 @@ const processUserCode = (pou: CppPouData): string => {
   const setupFunctionName = `${pou.name.toLowerCase()}_setup`
   const loopFunctionName = `${pou.name.toLowerCase()}_loop`
 
-  const inputVariables = pou.variables.filter((v) => v.class === 'input')
-  const outputVariables = pou.variables.filter((v) => v.class === 'output')
+  const exposedVariables = getExposedCppVariables(pou.variables)
 
   let processedCode = `//definition of external blocks - ${pou.name.toUpperCase()}\n`
   processedCode += `typedef struct {\n`
 
-  inputVariables.forEach((variable) => {
-    processedCode += generateStructMember(variable)
-  })
-
-  outputVariables.forEach((variable) => {
+  exposedVariables.forEach((variable) => {
     processedCode += generateStructMember(variable)
   })
 
@@ -45,11 +42,7 @@ const processUserCode = (pou: CppPouData): string => {
   processedCode += `extern "C" void ${setupFunctionName}(${structName} *vars);\n`
   processedCode += `extern "C" void ${loopFunctionName}(${structName} *vars);\n\n`
 
-  inputVariables.forEach((variable) => {
-    processedCode += generateDefine(variable)
-  })
-
-  outputVariables.forEach((variable) => {
+  exposedVariables.forEach((variable) => {
     processedCode += generateDefine(variable)
   })
 
@@ -67,10 +60,7 @@ const processUserCode = (pou: CppPouData): string => {
   processedCode += modifiedUserCode
   processedCode += '\n'
 
-  inputVariables.forEach((variable) => {
-    processedCode += generateUndef(variable)
-  })
-  outputVariables.forEach((variable) => {
+  exposedVariables.forEach((variable) => {
     processedCode += generateUndef(variable)
   })
   processedCode += '\n'
diff --git a/src/backend/shared/utils/cpp/generateCBlocksHeader.ts b/src/backend/shared/utils/cpp/generateCBlocksHeader.ts
index 0822ffce7..75f1c59c6 100644
--- a/src/backend/shared/utils/cpp/generateCBlocksHeader.ts
+++ b/src/backend/shared/utils/cpp/generateCBlocksHeader.ts
@@ -1,6 +1,8 @@
 import { generateStructMember } from '../../../../frontend/utils/PLC/array-codegen-helpers'
 import type { PLCVariable } from '../../../../middleware/shared/ports/types'
 
+import { getExposedCppVariables } from './shared'
+
 type CppPouData = {
   name: string
   variables: PLCVariable[]
@@ -17,17 +19,12 @@ const generateCBlocksHeader = (cppPous: CppPouData[]): string => {
     const setupFunctionName = `${pou.name.toLowerCase()}_setup`
     const loopFunctionName = `${pou.name.toLowerCase()}_loop`
 
-    const inputVariables = pou.variables.filter((v) => v.class === 'input')
-    const outputVariables = pou.variables.filter((v) => v.class === 'output')
+    const exposedVariables = getExposedCppVariables(pou.variables)
 
     headerContent += `//definition of external blocks - ${pou.name.toUpperCase()}\n`
     headerContent += `typedef struct {\n`
 
-    inputVariables.forEach((variable) => {
-      headerContent += generateStructMember(variable)
-    })
-
-    outputVariables.forEach((variable) => {
+    exposedVariables.forEach((variable) => {
       headerContent += generateStructMember(variable)
     })
 
diff --git a/src/frontend/components/_molecules/variables-table/selectable-cell.tsx b/src/frontend/components/_molecules/variables-table/selectable-cell.tsx
index 7af575a2f..5cfe83d5e 100644
--- a/src/frontend/components/_molecules/variables-table/selectable-cell.tsx
+++ b/src/frontend/components/_molecules/variables-table/selectable-cell.tsx
@@ -439,9 +439,12 @@ const SelectableClassCell = ({
 
   const language = 'language' in editor.meta ? editor.meta.language : null
   const getVariableClasses = () => {
-    if (language === 'python' || language === 'cpp') {
+    if (language === 'python') {
       return ['input', 'output']
     }
+    if (language === 'cpp') {
+      return ['input', 'output', 'local']
+    }
     return ['input', 'output', 'inOut', 'external', 'local', 'temp']
   }
 
diff --git a/src/frontend/components/_organisms/variables-editor/index.tsx b/src/frontend/components/_organisms/variables-editor/index.tsx
index 71835f551..e1543c338 100644
--- a/src/frontend/components/_organisms/variables-editor/index.tsx
+++ b/src/frontend/components/_organisms/variables-editor/index.tsx
@@ -334,7 +334,7 @@ const VariablesEditor = () => {
     const selectedRow = parseInt(editorVariables.selectedRow)
 
     const language = 'language' in editor.meta ? editor.meta.language : null
-    const defaultClass: PLCVariable['class'] = language === 'python' || language === 'cpp' ? 'input' : 'local'
+    const defaultClass: PLCVariable['class'] = language === 'python' ? 'input' : 'local'
 
     if (variables.length === 0) {
       createVariable({
diff --git a/src/frontend/utils/cpp/__tests__/generateSTCode.test.ts b/src/frontend/utils/cpp/__tests__/generateSTCode.test.ts
index b8678dc70..f50362316 100644
--- a/src/frontend/utils/cpp/__tests__/generateSTCode.test.ts
+++ b/src/frontend/utils/cpp/__tests__/generateSTCode.test.ts
@@ -1,7 +1,7 @@
 import type { PLCVariable } from '../../../../middleware/shared/ports/types'
 import { generateSTCode } from '../generateSTCode'
 
-const makeScalarVar = (name: string, cls: 'input' | 'output', baseType: string): PLCVariable => ({
+const makeScalarVar = (name: string, cls: 'input' | 'output' | 'local', baseType: string): PLCVariable => ({
   name,
   class: cls,
   type: { definition: 'base-type', value: baseType },
@@ -10,7 +10,7 @@ const makeScalarVar = (name: string, cls: 'input' | 'output', baseType: string):
   debug: false,
 })
 
-const makeArrayVar = (name: string, cls: 'input' | 'output', baseType: string, dimension: string): PLCVariable => ({
+const makeArrayVar = (name: string, cls: 'input' | 'output' | 'local', baseType: string, dimension: string): PLCVariable => ({
   name,
   class: cls,
   type: {
@@ -128,22 +128,18 @@ describe('generateSTCode', () => {
     expect(result).not.toContain('data__->B.value.table[__i].value = __flat_B[__i]')
   })
 
-  it('filters out local variables', () => {
-    const localVar: PLCVariable = {
-      name: 'localVal',
-      class: 'local',
-      type: { definition: 'base-type', value: 'INT' },
-      location: '',
-      documentation: '',
-      debug: false,
-    }
-
+  it('includes user local variables and excludes runtime-only locals', () => {
     const result = generateSTCode({
       pouName: 'test',
-      allVariables: [makeScalarVar('x', 'input', 'INT'), localVar],
+      allVariables: [
+        makeScalarVar('x', 'input', 'INT'),
+        makeScalarVar('localVal', 'local', 'INT'),
+        makeScalarVar('hasBeenInitialized', 'local', 'BOOL'),
+      ],
     })
 
-    expect(result).not.toContain('LOCALVAL')
+    expect(result).toContain('vars.LOCALVAL = &data__->LOCALVAL.value;')
+    expect(result).not.toContain('vars.HASBEENINITIALIZED')
   })
 
   it('generates correct start index offset for non-zero-based arrays', () => {
@@ -155,4 +151,22 @@ describe('generateSTCode', () => {
     expect(result).toContain('vars.ARR = __flat_ARR - 5;')
     expect(result).toContain('IEC_INT __flat_ARR[6];')
   })
+
+  it('preserves local arrays through the flat staging path', () => {
+    const result = generateSTCode({
+      pouName: 'CounterBlock',
+      allVariables: [
+        makeScalarVar('counter', 'local', 'INT'),
+        makeArrayVar('history', 'local', 'INT', '0..2'),
+        makeScalarVar('hasBeenInitialized', 'local', 'BOOL'),
+        makeScalarVar('out', 'output', 'INT'),
+      ],
+    })
+
+    expect(result).toContain('IEC_INT __flat_HISTORY[3];')
+    expect(result).toContain('__flat_HISTORY[__i] = data__->HISTORY.value.table[__i].value;')
+    expect(result).toContain('vars.HISTORY = __flat_HISTORY - 0;')
+    expect(result).toContain('data__->HISTORY.value.table[__i].value = __flat_HISTORY[__i];')
+    expect(result).not.toContain('vars.HASBEENINITIALIZED')
+  })
 })
diff --git a/src/frontend/utils/cpp/generateSTCode.ts b/src/frontend/utils/cpp/generateSTCode.ts
index 109513bc5..afcf2d63e 100644
--- a/src/frontend/utils/cpp/generateSTCode.ts
+++ b/src/frontend/utils/cpp/generateSTCode.ts
@@ -6,6 +6,8 @@ import {
   isArrayVariable,
 } from '../PLC/array-codegen-helpers'
 
+import { getExposedCppVariables } from './shared'
+
 type STCodeGenerationParams = {
   pouName: string
   allVariables: PLCVariable[]
@@ -72,14 +74,16 @@ const generateOutputArrayCopyBack = (outputVariables: PLCVariable[]): string =>
 const generateSTCode = (params: STCodeGenerationParams): string => {
   const { pouName, allVariables } = params
 
-  const inputVariables = allVariables.filter((v) => v.class === 'input')
-  const outputVariables = allVariables.filter((v) => v.class === 'output')
+  const exposedVariables = getExposedCppVariables(allVariables)
+  const inputVariables = exposedVariables.filter((v) => v.class === 'input')
+  const outputVariables = exposedVariables.filter((v) => v.class === 'output')
+  const localVariables = exposedVariables.filter((v) => v.class === 'local')
 
   const structName = `${pouName.toUpperCase()}_VARS`
   const setupFunctionName = `${pouName.toLowerCase()}_setup`
   const loopFunctionName = `${pouName.toLowerCase()}_loop`
 
-  const allArrayVariables = [...inputVariables, ...outputVariables].filter(isArrayVariable)
+  const allArrayVariables = exposedVariables.filter(isArrayVariable)
 
   const flatArrayDecl = generateFlatArrayDeclarations(allArrayVariables)
   const flatArrayCopiesIn = generateFlatArrayCopiesIn(allArrayVariables)
@@ -91,8 +95,11 @@ const generateSTCode = (params: STCodeGenerationParams): string => {
   outputVariables.forEach((variable) => {
     variableAssignments += generateVariableAssignment(variable)
   })
+  localVariables.forEach((variable) => {
+    variableAssignments += generateVariableAssignment(variable)
+  })
 
-  const outputCopyBack = generateOutputArrayCopyBack(outputVariables)
+  const outputCopyBack = generateOutputArrayCopyBack([...outputVariables, ...localVariables])
 
   let stCode = `{{
 ${structName} vars;
diff --git a/src/frontend/utils/cpp/shared.ts b/src/frontend/utils/cpp/shared.ts
new file mode 100644
index 000000000..488fbf627
--- /dev/null
+++ b/src/frontend/utils/cpp/shared.ts
@@ -0,0 +1,19 @@
+import type { PLCVariable } from '../../../middleware/shared/ports/types'
+
+const CPP_RUNTIME_LOCAL_VARIABLES = new Set(['hasBeenInitialized'])
+
+const getExposedCppVariables = (variables: PLCVariable[]): PLCVariable[] => {
+  return variables.filter((variable) => {
+    if (variable.class === 'input' || variable.class === 'output') {
+      return true
+    }
+
+    if (variable.class === 'local') {
+      return !CPP_RUNTIME_LOCAL_VARIABLES.has(variable.name)
+    }
+
+    return false
+  })
+}
+
+export { getExposedCppVariables }