diff --git a/STYLEGUIDE.md b/STYLEGUIDE.md
index 2b2b946e..75993c1d 100644
--- a/STYLEGUIDE.md
+++ b/STYLEGUIDE.md
@@ -81,6 +81,18 @@ Steps must:
 - not perform authentication
 - write only declared `State.*` outputs
 
+### ScriptBlock Validation in Steps
+
+**All step implementations must validate their inputs using the centralized helper:**
+
+```powershell
+Assert-IdleNoScriptBlock -InputObject $config -Path 'With.Config'
+```
+
+- Do not implement custom ScriptBlock checks
+- Use `Assert-IdleNoScriptBlock` from `IdLE.Core` for consistent enforcement
+- The helper recursively validates hashtables, arrays, and PSCustomObjects
+
 ---
 
 ## Providers
diff --git a/docs/extend/steps.md b/docs/extend/steps.md
index 3576f63b..fd63ff72 100644
--- a/docs/extend/steps.md
+++ b/docs/extend/steps.md
@@ -140,7 +140,19 @@ Steps receive inputs from the workflow under `Inputs` and may reference:
 - `State.*`
 - `Policy.*` (optional root, host-defined)
 
-Avoid executing code from configuration. Keep inputs data-only.
+### Security: Data-only constraint
+
+**All step inputs must be data-only and must not contain ScriptBlocks.**
+
+Step implementations MUST validate their inputs using the centralized helper:
+
+```powershell
+Assert-IdleNoScriptBlock -InputObject $config -Path 'With.Config'
+```
+
+The `Assert-IdleNoScriptBlock` function is exported from `IdLE.Core` and recursively validates hashtables, arrays, and PSCustomObjects.
+
+**Do not implement custom ScriptBlock validation.** Use the centralized helper to ensure consistent enforcement across all steps.
 
 ---
 
diff --git a/src/IdLE.Core/IdLE.Core.psd1 b/src/IdLE.Core/IdLE.Core.psd1
index 40a22754..f9b98cf7 100644
--- a/src/IdLE.Core/IdLE.Core.psd1
+++ b/src/IdLE.Core/IdLE.Core.psd1
@@ -9,14 +9,15 @@
     HelpInfoUri       = 'https://blindzero.github.io/IdentityLifecycleEngine/'
 
     FunctionsToExport = @(
-        'New-IdleLifecycleRequestObject',
-        'Test-IdleWorkflowDefinitionObject',
-        'New-IdlePlanObject',
-        'Invoke-IdlePlanObject',
+        'Assert-IdleNoScriptBlock',
         'Export-IdlePlanObject',
-        'New-IdleAuthSessionBroker',
+        'Invoke-IdlePlanObject',
         'Invoke-IdleProviderMethod',
-        'Test-IdleProviderMethodParameter'
+        'New-IdleAuthSessionBroker',
+        'New-IdleLifecycleRequestObject',
+        'New-IdlePlanObject',
+        'Test-IdleProviderMethodParameter',
+        'Test-IdleWorkflowDefinitionObject'
     )
     CmdletsToExport   = @()
     AliasesToExport   = @()
diff --git a/src/IdLE.Core/IdLE.Core.psm1 b/src/IdLE.Core/IdLE.Core.psm1
index 06956a7b..831c7ce5 100644
--- a/src/IdLE.Core/IdLE.Core.psm1
+++ b/src/IdLE.Core/IdLE.Core.psm1
@@ -40,12 +40,13 @@ foreach ($path in @($PrivatePath, $PublicPath)) {
 
 # Core exports selected factory functions. The meta module (IdLE) exposes the public API.
 Export-ModuleMember -Function @(
-    'New-IdleLifecycleRequestObject',
-    'Test-IdleWorkflowDefinitionObject',
-    'New-IdlePlanObject',
-    'Invoke-IdlePlanObject',
+    'Assert-IdleNoScriptBlock',
     'Export-IdlePlanObject',
-    'New-IdleAuthSessionBroker',
+    'Invoke-IdlePlanObject',
     'Invoke-IdleProviderMethod',
-    'Test-IdleProviderMethodParameter'
+    'New-IdleAuthSessionBroker',
+    'New-IdleLifecycleRequestObject',
+    'New-IdlePlanObject',
+    'Test-IdleProviderMethodParameter',
+    'Test-IdleWorkflowDefinitionObject'
 ) -Alias @()
diff --git a/src/IdLE.Core/Private/Assert-IdleNoScriptBlock.ps1 b/src/IdLE.Core/Public/Assert-IdleNoScriptBlock.ps1
similarity index 53%
rename from src/IdLE.Core/Private/Assert-IdleNoScriptBlock.ps1
rename to src/IdLE.Core/Public/Assert-IdleNoScriptBlock.ps1
index d5737679..34a2fca7 100644
--- a/src/IdLE.Core/Private/Assert-IdleNoScriptBlock.ps1
+++ b/src/IdLE.Core/Public/Assert-IdleNoScriptBlock.ps1
@@ -1,7 +1,49 @@
-# Asserts that the provided InputObject does not contain any ScriptBlock objects.
-# Recursively walks hashtables, enumerables, and PSCustomObjects.
-
 function Assert-IdleNoScriptBlock {
+    <#
+    .SYNOPSIS
+    Asserts that the provided object does not contain any ScriptBlock objects.
+
+    .DESCRIPTION
+    This is a security-critical helper that validates data-only constraints.
+    It recursively walks hashtables, enumerables, and PSCustomObjects to ensure
+    no ScriptBlock objects are present.
+
+    This helper enforces IdLE's security boundary: workflow configuration and step inputs
+    must not contain executable code.
+
+    Step implementations should use this helper to validate their inputs rather than
+    implementing custom ScriptBlock checks.
+
+    .PARAMETER InputObject
+    The object to validate. Can be null, a scalar value, or a complex nested structure.
+
+    .PARAMETER Path
+    The logical path describing the current position in the data structure.
+    Used in error messages to pinpoint where a ScriptBlock was found.
+
+    .OUTPUTS
+    None. Throws an ArgumentException if a ScriptBlock is found.
+
+    .EXAMPLE
+    # Validate a hashtable
+    $config = @{
+        Mode = 'Enabled'
+        Message = 'Out of office'
+    }
+    Assert-IdleNoScriptBlock -InputObject $config -Path 'With.Config'
+
+    .EXAMPLE
+    # Detect ScriptBlock in nested structure
+    $data = @{
+        Setting = { Write-Host "bad" }
+    }
+    Assert-IdleNoScriptBlock -InputObject $data -Path 'Input'
+    # Throws: ScriptBlocks are not allowed in request data. Found at: Input.Setting
+
+    .NOTES
+    The function includes an exemption for IdLE.AuthSessionBroker objects,
+    which contain internal ScriptBlocks as part of their implementation.
+    #>
     [CmdletBinding()]
     param(
         [Parameter(Mandatory)]
diff --git a/src/IdLE.Steps.Mailbox/Public/Invoke-IdleStepMailboxOutOfOfficeEnsure.ps1 b/src/IdLE.Steps.Mailbox/Public/Invoke-IdleStepMailboxOutOfOfficeEnsure.ps1
index 22f3f577..7c8da290 100644
--- a/src/IdLE.Steps.Mailbox/Public/Invoke-IdleStepMailboxOutOfOfficeEnsure.ps1
+++ b/src/IdLE.Steps.Mailbox/Public/Invoke-IdleStepMailboxOutOfOfficeEnsure.ps1
@@ -207,11 +207,7 @@ function Invoke-IdleStepMailboxOutOfOfficeEnsure {
     }
 
     # Security: reject ScriptBlocks in Config (data-only constraint)
-    foreach ($key in $config.Keys) {
-        if ($config[$key] -is [ScriptBlock]) {
-            throw "Mailbox.OutOfOffice.Ensure With.Config must not contain ScriptBlocks. Found ScriptBlock in key '$key'."
-        }
-    }
+    Assert-IdleNoScriptBlock -InputObject $config -Path 'With.Config'
 
     # Validate MessageFormat if provided
     if ($config.ContainsKey('MessageFormat')) {
diff --git a/tests/Core/Assert-IdleNoScriptBlock.Tests.ps1 b/tests/Core/Assert-IdleNoScriptBlock.Tests.ps1
new file mode 100644
index 00000000..94214954
--- /dev/null
+++ b/tests/Core/Assert-IdleNoScriptBlock.Tests.ps1
@@ -0,0 +1,195 @@
+Set-StrictMode -Version Latest
+
+BeforeAll {
+    . (Join-Path (Split-Path -Path $PSScriptRoot -Parent) '_testHelpers.ps1')
+    Import-IdleTestModule
+}
+
+Describe 'Assert-IdleNoScriptBlock' {
+    Context 'Valid data-only inputs' {
+        It 'accepts null input' {
+            { Assert-IdleNoScriptBlock -InputObject $null -Path 'Test' } | Should -Not -Throw
+        }
+
+        It 'accepts scalar values' {
+            { Assert-IdleNoScriptBlock -InputObject 'text' -Path 'Test' } | Should -Not -Throw
+            { Assert-IdleNoScriptBlock -InputObject 42 -Path 'Test' } | Should -Not -Throw
+            { Assert-IdleNoScriptBlock -InputObject $true -Path 'Test' } | Should -Not -Throw
+        }
+
+        It 'accepts simple hashtable' {
+            $data = @{
+                Mode = 'Enabled'
+                Message = 'Out of office'
+                Count = 5
+            }
+            { Assert-IdleNoScriptBlock -InputObject $data -Path 'Config' } | Should -Not -Throw
+        }
+
+        It 'accepts nested hashtable' {
+            $data = @{
+                Level1 = @{
+                    Level2 = @{
+                        Value = 'deep'
+                    }
+                }
+            }
+            { Assert-IdleNoScriptBlock -InputObject $data -Path 'Nested' } | Should -Not -Throw
+        }
+
+        It 'accepts arrays' {
+            $data = @('one', 'two', 'three')
+            { Assert-IdleNoScriptBlock -InputObject $data -Path 'Array' } | Should -Not -Throw
+        }
+
+        It 'accepts arrays of hashtables' {
+            $data = @(
+                @{ Name = 'First'; Value = 1 }
+                @{ Name = 'Second'; Value = 2 }
+            )
+            { Assert-IdleNoScriptBlock -InputObject $data -Path 'Items' } | Should -Not -Throw
+        }
+
+        It 'accepts PSCustomObject' {
+            $data = [pscustomobject]@{
+                Property1 = 'value1'
+                Property2 = 42
+            }
+            { Assert-IdleNoScriptBlock -InputObject $data -Path 'Object' } | Should -Not -Throw
+        }
+
+        It 'accepts nested PSCustomObject' {
+            $data = [pscustomobject]@{
+                Outer = [pscustomobject]@{
+                    Inner = 'value'
+                }
+            }
+            { Assert-IdleNoScriptBlock -InputObject $data -Path 'Object' } | Should -Not -Throw
+        }
+    }
+
+    Context 'ScriptBlock detection' {
+        It 'rejects direct ScriptBlock' {
+            $block = { Write-Host "bad" }
+            { Assert-IdleNoScriptBlock -InputObject $block -Path 'Direct' } |
+                Should -Throw -ExceptionType ([System.ArgumentException]) -ExpectedMessage '*ScriptBlocks are not allowed*Direct*'
+        }
+
+        It 'rejects ScriptBlock in hashtable' {
+            $data = @{
+                Good = 'value'
+                Bad = { Write-Host "malicious" }
+            }
+            { Assert-IdleNoScriptBlock -InputObject $data -Path 'Config' } |
+                Should -Throw -ExceptionType ([System.ArgumentException]) -ExpectedMessage '*ScriptBlocks are not allowed*Config.Bad*'
+        }
+
+        It 'rejects ScriptBlock in nested hashtable' {
+            $data = @{
+                Level1 = @{
+                    Level2 = @{
+                        Code = { Get-Process }
+                    }
+                }
+            }
+            { Assert-IdleNoScriptBlock -InputObject $data -Path 'Nested' } |
+                Should -Throw -ExceptionType ([System.ArgumentException]) -ExpectedMessage '*ScriptBlocks are not allowed*Nested.Level1.Level2.Code*'
+        }
+
+        It 'rejects ScriptBlock in array' {
+            $data = @(
+                'normal',
+                { Write-Host "bad" },
+                'another'
+            )
+            { Assert-IdleNoScriptBlock -InputObject $data -Path 'Array' } |
+                Should -Throw -ExceptionType ([System.ArgumentException])
+            
+            try {
+                Assert-IdleNoScriptBlock -InputObject $data -Path 'Array'
+            }
+            catch {
+                $_.Exception.Message | Should -Match 'Array\[1\]'
+            }
+        }
+
+        It 'rejects ScriptBlock in PSCustomObject' {
+            $data = [pscustomobject]@{
+                SafeProperty = 'value'
+                UnsafeProperty = { Write-Host "code" }
+            }
+            { Assert-IdleNoScriptBlock -InputObject $data -Path 'Object' } |
+                Should -Throw -ExceptionType ([System.ArgumentException]) -ExpectedMessage '*ScriptBlocks are not allowed*Object.UnsafeProperty*'
+        }
+
+        It 'rejects ScriptBlock deeply nested in complex structure' {
+            $data = @{
+                Items = @(
+                    @{
+                        Name = 'Item1'
+                        Properties = [pscustomobject]@{
+                            Setting = 'safe'
+                        }
+                    }
+                    @{
+                        Name = 'Item2'
+                        Properties = [pscustomobject]@{
+                            Action = { Invoke-Command }
+                        }
+                    }
+                )
+            }
+            { Assert-IdleNoScriptBlock -InputObject $data -Path 'Data' } |
+                Should -Throw -ExceptionType ([System.ArgumentException])
+            
+            try {
+                Assert-IdleNoScriptBlock -InputObject $data -Path 'Data'
+            }
+            catch {
+                $_.Exception.Message | Should -Match 'Data\.Items\[1\]\.Properties\.Action'
+            }
+        }
+    }
+
+    Context 'Trusted type exemptions' {
+        It 'allows IdLE.AuthSessionBroker with internal ScriptBlock' {
+            $broker = [pscustomobject]@{
+                PSTypeName = 'IdLE.AuthSessionBroker'
+                ValidateAuthSession = { param($s) return $true }
+            }
+            $broker.PSObject.TypeNames.Insert(0, 'IdLE.AuthSessionBroker')
+
+            { Assert-IdleNoScriptBlock -InputObject $broker -Path 'Broker' } | Should -Not -Throw
+        }
+    }
+
+    Context 'Path reporting' {
+        It 'includes correct path in error message for top-level ScriptBlock' {
+            $block = { Write-Host "test" }
+            try {
+                Assert-IdleNoScriptBlock -InputObject $block -Path 'TopLevel'
+                throw "Should have thrown"
+            }
+            catch {
+                $_.Exception.Message | Should -BeLike '*TopLevel*'
+            }
+        }
+
+        It 'includes correct path in error message for nested ScriptBlock' {
+            $data = @{
+                Outer = @{
+                    Middle = @{
+                        Inner = { Write-Host "nested" }
+                    }
+                }
+            }
+            try {
+                Assert-IdleNoScriptBlock -InputObject $data -Path 'Root'
+                throw "Should have thrown"
+            }
+            catch {
+                $_.Exception.Message | Should -BeLike '*Root.Outer.Middle.Inner*'
+            }
+        }
+    }
+}
diff --git a/tests/Steps/Invoke-IdleStepMailboxOutOfOfficeEnsure.Tests.ps1 b/tests/Steps/Invoke-IdleStepMailboxOutOfOfficeEnsure.Tests.ps1
index e2a4cdae..09e21710 100644
--- a/tests/Steps/Invoke-IdleStepMailboxOutOfOfficeEnsure.Tests.ps1
+++ b/tests/Steps/Invoke-IdleStepMailboxOutOfOfficeEnsure.Tests.ps1
@@ -197,7 +197,7 @@ Describe 'Invoke-IdleStepMailboxOutOfOfficeEnsure' {
         
         $handler = 'IdLE.Steps.Mailbox\Invoke-IdleStepMailboxOutOfOfficeEnsure'
         { & $handler -Context $script:Context -Step $step } |
-            Should -Throw "*must not contain ScriptBlocks*"
+            Should -Throw "*ScriptBlocks are not allowed*"
     }
     
     It 'throws when provider is missing' {