diff --git a/src/IdLE.Provider.ExchangeOnline/Private/New-IdleExchangeOnlineAdapter.ps1 b/src/IdLE.Provider.ExchangeOnline/Private/New-IdleExchangeOnlineAdapter.ps1
index 7013d6c2..470d579e 100644
--- a/src/IdLE.Provider.ExchangeOnline/Private/New-IdleExchangeOnlineAdapter.ps1
+++ b/src/IdLE.Provider.ExchangeOnline/Private/New-IdleExchangeOnlineAdapter.ps1
@@ -18,10 +18,6 @@ function New-IdleExchangeOnlineAdapter {
         [switch] $UseRestApi
     )
 
-    # Regex patterns for sanitizing error messages (captured by scriptblock closure)
-    $bearerTokenPattern = 'Bearer\s+[^\s]+'
-    $tokenAssignmentPattern = 'token[^\s]*\s*=\s*[^\s,;]+'
-
     $adapter = [pscustomobject]@{
         PSTypeName = 'IdLE.ExchangeOnlineAdapter'
         UseRestApi = [bool]$UseRestApi
@@ -37,6 +33,10 @@ function New-IdleExchangeOnlineAdapter {
             [hashtable] $Parameters = @{}
         )
 
+        # Regex patterns for sanitizing error messages (defined inside scriptblock for reliable scoping)
+        $bearerTokenPattern = 'Bearer\s+[^\s]+'
+        $tokenAssignmentPattern = 'token[^\s]*\s*=\s*[^\s,;]+'
+
         try {
             $result = & $CommandName @Parameters
             return $result
diff --git a/tests/Providers/ExchangeOnlineProvider.Tests.ps1 b/tests/Providers/ExchangeOnlineProvider.Tests.ps1
index a033492c..24447515 100644
--- a/tests/Providers/ExchangeOnlineProvider.Tests.ps1
+++ b/tests/Providers/ExchangeOnlineProvider.Tests.ps1
@@ -445,6 +445,46 @@ Describe 'ExchangeOnline provider - Unit tests' {
         }
     }
 
+    Context 'New-IdleExchangeOnlineAdapter - InvokeSafely scoping regression' {
+        BeforeAll {
+            # Import private adapter function directly for unit testing
+            $repoRoot = Split-Path -Path (Split-Path -Path $PSScriptRoot -Parent) -Parent
+            $adapterPath = Join-Path -Path $repoRoot -ChildPath 'src\IdLE.Provider.ExchangeOnline\Private\New-IdleExchangeOnlineAdapter.ps1'
+
+            if (-not (Test-Path -LiteralPath $adapterPath)) {
+                throw "Private adapter function file not found at path: $adapterPath"
+            }
+            . $adapterPath
+
+            # Dot-source provider test helpers so Invoke-IdleTestBearerTokenError is available at run time
+            . (Join-Path -Path $PSScriptRoot -ChildPath '_testHelpers.Providers.ps1')
+        }
+
+        It 'InvokeSafely can be called from another ScriptMethod without variable-not-set error' {
+            # Regression test: $bearerTokenPattern and $tokenAssignmentPattern must be in scope
+            # when InvokeSafely is invoked via $this.InvokeSafely() from another ScriptMethod.
+            $adapter = New-IdleExchangeOnlineAdapter
+
+            # Wrap the real adapter with a ScriptMethod that calls $this.InvokeSafely() to
+            # simulate the same execution path as GetMailbox -> InvokeSafely.
+            $adapter | Add-Member -MemberType ScriptMethod -Name TestViaMethod -Value {
+                $this.InvokeSafely('Write-Output', @{ InputObject = 'ok' })
+            } -Force
+
+            { $adapter.TestViaMethod() } | Should -Not -Throw
+        }
+
+        It 'InvokeSafely sanitizes bearer tokens in error messages without variable-not-set error' {
+            $adapter = New-IdleExchangeOnlineAdapter
+
+            $adapter | Add-Member -MemberType ScriptMethod -Name TestErrorSanitization -Value {
+                $this.InvokeSafely('Invoke-IdleTestBearerTokenError', @{})
+            } -Force
+
+            { $adapter.TestErrorSanitization() } | Should -Throw -ExpectedMessage "*Bearer <REDACTED>*"
+        }
+    }
+
     Context 'Normalize-IdleExchangeOnlineAutoReplyMessage' {
         BeforeAll {
             # Import the private normalization function for direct testing
diff --git a/tests/Providers/_testHelpers.Providers.ps1 b/tests/Providers/_testHelpers.Providers.ps1
index 58fe7df3..c99077a9 100644
--- a/tests/Providers/_testHelpers.Providers.ps1
+++ b/tests/Providers/_testHelpers.Providers.ps1
@@ -13,5 +13,18 @@ directly by test files.
 #>
 
 # Provider-specific helpers will be added here as needed.
-# This file is currently empty but provides a clear extension point for
-# provider-related test infrastructure.
+
+function Invoke-IdleTestBearerTokenError {
+    <#
+    .SYNOPSIS
+    Test helper: throws an exception whose message contains a bearer token.
+
+    .DESCRIPTION
+    Used by adapter unit tests to verify that InvokeSafely correctly sanitizes
+    bearer tokens from error messages without leaking sensitive data.
+    #>
+    [CmdletBinding()]
+    param()
+
+    throw 'Authentication failed: Bearer eyJhbGciOiJSUzI1NiJ9.payload.sig'
+}