diff --git a/src/PSProxmoxVE/Cmdlets/Connection/ConnectPveServerCmdlet.cs b/src/PSProxmoxVE/Cmdlets/Connection/ConnectPveServerCmdlet.cs
index 83b6210..f60af2c 100644
--- a/src/PSProxmoxVE/Cmdlets/Connection/ConnectPveServerCmdlet.cs
+++ b/src/PSProxmoxVE/Cmdlets/Connection/ConnectPveServerCmdlet.cs
@@ -137,7 +137,7 @@ namespace PSProxmoxVE.Cmdlets.Connection
                     return;
             }
 
-            ModuleState.ActiveSession = session;
+            ModuleState.SetActiveSession(this, session);
 
             if (SkipCertificateCheck.IsPresent)
                 WriteWarning("TLS certificate validation is disabled for this session. Connections are susceptible to man-in-the-middle attacks. Use only in trusted networks or test environments.");
diff --git a/src/PSProxmoxVE/Cmdlets/Connection/DisconnectPveServerCmdlet.cs b/src/PSProxmoxVE/Cmdlets/Connection/DisconnectPveServerCmdlet.cs
index 1b9185b..40cf9fe 100644
--- a/src/PSProxmoxVE/Cmdlets/Connection/DisconnectPveServerCmdlet.cs
+++ b/src/PSProxmoxVE/Cmdlets/Connection/DisconnectPveServerCmdlet.cs
@@ -19,7 +19,8 @@ namespace PSProxmoxVE.Cmdlets.Connection
         protected override void ProcessPveRecord()
         {
             bool explicitSessionSupplied = MyInvocation.BoundParameters.ContainsKey(nameof(Session));
-            var sessionToDisconnect = explicitSessionSupplied ? Session : ModuleState.ActiveSession;
+            var moduleSession = ModuleState.GetActiveSession(this);
+            var sessionToDisconnect = explicitSessionSupplied ? Session : moduleSession;
 
             if (sessionToDisconnect is null)
             {
@@ -27,7 +28,7 @@ namespace PSProxmoxVE.Cmdlets.Connection
                 return;
             }
 
-            if (!ReferenceEquals(sessionToDisconnect, ModuleState.ActiveSession))
+            if (!ReferenceEquals(sessionToDisconnect, moduleSession))
             {
                 var lifecycle = sessionToDisconnect.AuthMode == PveAuthMode.ApiToken
                     ? "API tokens do not expire; revoke it with Remove-PveApiToken if it is no longer needed."
@@ -39,7 +40,7 @@ namespace PSProxmoxVE.Cmdlets.Connection
             if (!ShouldProcess($"{sessionToDisconnect.Hostname}:{sessionToDisconnect.Port}", "Disconnect"))
                 return;
 
-            ModuleState.ActiveSession = null;
+            ModuleState.SetActiveSession(this, null);
             WriteVerbose($"Disconnected from {sessionToDisconnect.Hostname}:{sessionToDisconnect.Port}.");
         }
     }
diff --git a/src/PSProxmoxVE/Cmdlets/Connection/TestPveConnectionCmdlet.cs b/src/PSProxmoxVE/Cmdlets/Connection/TestPveConnectionCmdlet.cs
index 7f50a18..cd3baf1 100644
--- a/src/PSProxmoxVE/Cmdlets/Connection/TestPveConnectionCmdlet.cs
+++ b/src/PSProxmoxVE/Cmdlets/Connection/TestPveConnectionCmdlet.cs
@@ -24,7 +24,7 @@ namespace PSProxmoxVE.Cmdlets.Connection
 
         protected override void ProcessRecord()
         {
-            var session = ModuleState.ActiveSession;
+            var session = ModuleState.GetActiveSession(this);
             var isConnected = session is not null && !session.IsExpired;
 
             if (Detailed.IsPresent)
diff --git a/src/PSProxmoxVE/Cmdlets/PveCmdletBase.cs b/src/PSProxmoxVE/Cmdlets/PveCmdletBase.cs
index ec14290..4df1870 100644
--- a/src/PSProxmoxVE/Cmdlets/PveCmdletBase.cs
+++ b/src/PSProxmoxVE/Cmdlets/PveCmdletBase.cs
@@ -80,13 +80,13 @@ namespace PSProxmoxVE.Cmdlets
 
         /// <summary>
         /// Returns the session to use for this cmdlet.
-        /// Resolution order: -Session parameter → ModuleState.ActiveSession.
+        /// Resolution order: -Session parameter → the runspace's module session.
         /// Throws <see cref="PveNotConnectedException"/> if no session is available,
         /// or <see cref="PveSessionExpiredException"/> if the session ticket has expired.
         /// </summary>
         protected PveSession GetSession()
         {
-            var session = Session ?? ModuleState.ActiveSession;
+            var session = Session ?? ModuleState.GetActiveSession(this);
 
             if (session is null)
                 throw new PveNotConnectedException();
diff --git a/src/PSProxmoxVE/ModuleState.cs b/src/PSProxmoxVE/ModuleState.cs
index 6c5700d..9885fe2 100644
--- a/src/PSProxmoxVE/ModuleState.cs
+++ b/src/PSProxmoxVE/ModuleState.cs
@@ -1,10 +1,46 @@
+using System.Management.Automation;
 using PSProxmoxVE.Core.Authentication;
 
 namespace PSProxmoxVE
 {
-    /// <summary>Module-scoped state container for the active PVE session</summary>
+    /// <summary>
+    /// Per-runspace storage for the session established by Connect-PveServer.
+    /// The value lives in the module's own session state, which PowerShell creates
+    /// once per runspace, so runspaces cannot see or overwrite each other's session.
+    /// </summary>
     internal static class ModuleState
     {
-        internal static PveSession? ActiveSession { get; set; }
+        internal const string ActiveSessionVariable = "PSProxmoxVE.ActiveSession";
+
+        // Qualified so a nested scope in the module's session state (InModuleScope, a
+        // module-scoped scriptblock) neither writes a copy that dies with the scope nor reads
+        // through to a same-named global.
+        private const string ModuleActiveSessionVariable = "script:" + ActiveSessionVariable;
+
+        // Importing the assembly directly rather than through the manifest yields a module
+        // with no session state; the global scope is then the only per-runspace slot left.
+        private const string GlobalActiveSessionVariable = "global:" + ActiveSessionVariable;
+
+        internal static PveSession? GetActiveSession(PSCmdlet cmdlet)
+        {
+            var moduleState = ModuleSessionState(cmdlet);
+            return moduleState is null
+                ? cmdlet.SessionState.PSVariable.GetValue(GlobalActiveSessionVariable) as PveSession
+                : moduleState.PSVariable.GetValue(ModuleActiveSessionVariable) as PveSession;
+        }
+
+        internal static void SetActiveSession(PSCmdlet cmdlet, PveSession? session)
+        {
+            var moduleState = ModuleSessionState(cmdlet);
+            if (moduleState is null)
+                cmdlet.SessionState.PSVariable.Set(GlobalActiveSessionVariable, session);
+            else
+                moduleState.PSVariable.Set(ModuleActiveSessionVariable, session);
+        }
+
+        // PSCmdlet.SessionState resolves in the caller's scope, so it would store the session
+        // wherever the cmdlet happened to be invoked from.
+        private static SessionState? ModuleSessionState(PSCmdlet cmdlet) =>
+            cmdlet.MyInvocation?.MyCommand?.Module?.SessionState;
     }
 }
diff --git a/tests/PSProxmoxVE.Tests/Connection/Disconnect-PveServer.Tests.ps1 b/tests/PSProxmoxVE.Tests/Connection/Disconnect-PveServer.Tests.ps1
index e628f11..68a4063 100644
--- a/tests/PSProxmoxVE.Tests/Connection/Disconnect-PveServer.Tests.ps1
+++ b/tests/PSProxmoxVE.Tests/Connection/Disconnect-PveServer.Tests.ps1
@@ -44,19 +44,18 @@ Describe 'Disconnect-PveServer' {
 
     Context 'Active session lifecycle' {
         BeforeAll {
-            $script:PveSessionType = [PSProxmoxVE.Core.Authentication.PveSession]
-            $script:ModuleStateType = [System.AppDomain]::CurrentDomain.GetAssemblies() |
-                Where-Object { $_.GetName().Name -eq 'PSProxmoxVE' } |
-                ForEach-Object { $_.GetType('PSProxmoxVE.ModuleState') } |
-                Select-Object -First 1
-            $script:ModuleStateType | Should -Not -BeNullOrEmpty
+            $script:Module = Get-Module PSProxmoxVE
+            $script:Module | Should -Not -BeNullOrEmpty
 
-            $script:ActiveSessionProperty = $script:ModuleStateType.GetProperty(
-                'ActiveSession',
-                [System.Reflection.BindingFlags]'NonPublic, Static')
-            $script:ActiveSessionProperty | Should -Not -BeNullOrEmpty
+            $script:SetActiveSession = {
+                param($Value)
+                $script:Module.SessionState.PSVariable.Set('PSProxmoxVE.ActiveSession', $Value)
+            }
+            $script:GetActiveSession = {
+                $script:Module.SessionState.PSVariable.GetValue('PSProxmoxVE.ActiveSession')
+            }
 
-            $script:SessionCtor = $script:PveSessionType.GetConstructor(
+            $script:SessionCtor = [PSProxmoxVE.Core.Authentication.PveSession].GetConstructor(
                 [System.Reflection.BindingFlags]'NonPublic, Instance',
                 $null,
                 [type[]]@([string], [int], [bool], [string]),
@@ -65,7 +64,7 @@ Describe 'Disconnect-PveServer' {
         }
 
         AfterEach {
-            $script:ActiveSessionProperty.SetValue($null, $null)
+            & $script:SetActiveSession $null
         }
 
         It 'Should report "no session" when nothing is active' {
@@ -75,11 +74,11 @@ Describe 'Disconnect-PveServer' {
 
         It 'Should clear the active session and warn on a second disconnect' {
             $activeSession = $script:SessionCtor.Invoke(@('active.example', 8006, $false, 'activetoken'))
-            $script:ActiveSessionProperty.SetValue($null, $activeSession)
+            & $script:SetActiveSession $activeSession
 
             Disconnect-PveServer -Confirm:$false -WarningVariable w -WarningAction SilentlyContinue
             $w | Should -BeNullOrEmpty
-            $script:ActiveSessionProperty.GetValue($null) | Should -BeNullOrEmpty
+            & $script:GetActiveSession | Should -BeNullOrEmpty
 
             Disconnect-PveServer -Confirm:$false -WarningVariable w2 -WarningAction SilentlyContinue
             $w2[0] | Should -Match 'No active Proxmox VE session'
@@ -87,33 +86,41 @@ Describe 'Disconnect-PveServer' {
 
         It 'Should warn when disconnecting an explicit non-active session, and leave the active session untouched' {
             $activeSession = $script:SessionCtor.Invoke(@('active.example', 8006, $false, 'activetoken'))
-            $script:ActiveSessionProperty.SetValue($null, $activeSession)
+            & $script:SetActiveSession $activeSession
             $mismatchedSession = $script:SessionCtor.Invoke(@('other.example', 8006, $false, 'othertoken'))
 
             Disconnect-PveServer -Session $mismatchedSession -Confirm:$false -WarningVariable w -WarningAction SilentlyContinue
 
             $w[0] | Should -Match 'not the module-level session'
             $w[0] | Should -Match 'Remove-PveApiToken'
-            [object]::ReferenceEquals($script:ActiveSessionProperty.GetValue($null), $activeSession) | Should -BeTrue
+            [object]::ReferenceEquals((& $script:GetActiveSession), $activeSession) | Should -BeTrue
         }
 
         It 'Should disconnect when -Session matches the active session' {
             $activeSession = $script:SessionCtor.Invoke(@('active.example', 8006, $false, 'activetoken'))
-            $script:ActiveSessionProperty.SetValue($null, $activeSession)
+            & $script:SetActiveSession $activeSession
 
             Disconnect-PveServer -Session $activeSession -Confirm:$false -WarningVariable w -WarningAction SilentlyContinue
 
             $w | Should -BeNullOrEmpty
-            $script:ActiveSessionProperty.GetValue($null) | Should -BeNullOrEmpty
+            & $script:GetActiveSession | Should -BeNullOrEmpty
         }
 
         It 'Should not clear the active session under -WhatIf' {
             $activeSession = $script:SessionCtor.Invoke(@('active.example', 8006, $false, 'activetoken'))
-            $script:ActiveSessionProperty.SetValue($null, $activeSession)
+            & $script:SetActiveSession $activeSession
 
             Disconnect-PveServer -WhatIf -ErrorAction Stop
 
-            [object]::ReferenceEquals($script:ActiveSessionProperty.GetValue($null), $activeSession) | Should -BeTrue
+            [object]::ReferenceEquals((& $script:GetActiveSession), $activeSession) | Should -BeTrue
+        }
+
+        It 'Should see the session Test-PveConnection sees' {
+            $activeSession = $script:SessionCtor.Invoke(@('active.example', 8006, $false, 'activetoken'))
+            & $script:SetActiveSession $activeSession
+
+            Test-PveConnection | Should -BeTrue
+            [object]::ReferenceEquals((Test-PveConnection -Detailed), $activeSession) | Should -BeTrue
         }
     }
 }
diff --git a/tests/PSProxmoxVE.Tests/Connection/SessionIsolation.Tests.ps1 b/tests/PSProxmoxVE.Tests/Connection/SessionIsolation.Tests.ps1
new file mode 100644
index 0000000..4a430e9
--- /dev/null
+++ b/tests/PSProxmoxVE.Tests/Connection/SessionIsolation.Tests.ps1
@@ -0,0 +1,111 @@
+#Requires -Module Pester
+<#
+.SYNOPSIS
+    Pester 5 tests proving the active PVE session is per-runspace state, not a
+    process-wide static shared by every runspace in the host.
+    Fully offline — no live Proxmox VE target is required.
+#>
+
+BeforeAll {
+    . $PSScriptRoot/../_TestHelper.ps1
+
+    # A dll import produces a module with no session state, so the runspaces import the
+    # manifest that sits beside it.
+    $script:ModulePath = Join-Path (Split-Path (Get-Module PSProxmoxVE).Path) 'PSProxmoxVE.psd1'
+
+    function New-PveTestRunspace {
+        param([string]$Path)
+
+        $ps = [powershell]::Create()
+        $null = $ps.AddScript({
+            param($p)
+            Import-Module $p -Force -ErrorAction Stop
+        }).AddArgument($Path)
+        $null = $ps.Invoke()
+        if ($ps.Streams.Error.Count -gt 0) {
+            $err = $ps.Streams.Error[0]
+            $ps.Dispose()
+            throw "Runspace module import failed: $err"
+        }
+        $ps.Commands.Clear()
+        $ps.Streams.Error.Clear()
+        $ps
+    }
+
+    function Invoke-InRunspace {
+        param([System.Management.Automation.PowerShell]$Runspace, [scriptblock]$Script, $Argument)
+
+        $Runspace.Commands.Clear()
+        $Runspace.Streams.Error.Clear()
+        $null = $Runspace.AddScript($Script)
+        if ($PSBoundParameters.ContainsKey('Argument')) { $null = $Runspace.AddArgument($Argument) }
+        $out = $Runspace.Invoke()
+        if ($Runspace.Streams.Error.Count -gt 0) {
+            throw "Runspace script failed: $($Runspace.Streams.Error[0])"
+        }
+        , $out
+    }
+}
+
+Describe 'Active session isolation between runspaces' {
+    BeforeAll {
+        $script:SetSession = {
+            param($hostname)
+            $ctor = [PSProxmoxVE.Core.Authentication.PveSession].GetConstructor(
+                [System.Reflection.BindingFlags]'NonPublic, Instance',
+                $null,
+                [type[]]@([string], [int], [bool], [string]),
+                $null)
+            $session = $ctor.Invoke(@($hostname, 8006, $false, 'token'))
+            (Get-Module PSProxmoxVE).SessionState.PSVariable.Set('PSProxmoxVE.ActiveSession', $session)
+        }
+
+        $script:ClearSession = {
+            (Get-Module PSProxmoxVE).SessionState.PSVariable.Set('PSProxmoxVE.ActiveSession', $null)
+        }
+
+        $script:GetHostname = {
+            $detailed = Test-PveConnection -Detailed
+            if ($null -eq $detailed) { '<none>' } else { $detailed.Hostname }
+        }
+
+        $script:RunspaceA = New-PveTestRunspace -Path $script:ModulePath
+        $script:RunspaceB = New-PveTestRunspace -Path $script:ModulePath
+    }
+
+    AfterAll {
+        if ($script:RunspaceA) { $script:RunspaceA.Dispose() }
+        if ($script:RunspaceB) { $script:RunspaceB.Dispose() }
+    }
+
+    It 'Should not expose one runspace''s session to another' {
+        Invoke-InRunspace -Runspace $script:RunspaceB -Script $script:ClearSession
+        Invoke-InRunspace -Runspace $script:RunspaceA -Script $script:SetSession -Argument 'runspace-a.example'
+
+        $connectedInB = Invoke-InRunspace -Runspace $script:RunspaceB -Script { Test-PveConnection }
+        $connectedInB[0] | Should -BeFalse
+    }
+
+    It 'Should keep each runspace on its own server after both connect' {
+        Invoke-InRunspace -Runspace $script:RunspaceA -Script $script:SetSession -Argument 'runspace-a.example'
+        Invoke-InRunspace -Runspace $script:RunspaceB -Script $script:SetSession -Argument 'runspace-b.example'
+
+        $inA = Invoke-InRunspace -Runspace $script:RunspaceA -Script $script:GetHostname
+        $inB = Invoke-InRunspace -Runspace $script:RunspaceB -Script $script:GetHostname
+
+        $inA[0] | Should -Be 'runspace-a.example'
+        $inB[0] | Should -Be 'runspace-b.example'
+    }
+
+    It 'Should not let one runspace''s disconnect clear another''s session' {
+        Invoke-InRunspace -Runspace $script:RunspaceA -Script $script:SetSession -Argument 'runspace-a.example'
+        Invoke-InRunspace -Runspace $script:RunspaceB -Script $script:SetSession -Argument 'runspace-b.example'
+
+        Invoke-InRunspace -Runspace $script:RunspaceB -Script { Disconnect-PveServer -Confirm:$false }
+
+        $inA = Invoke-InRunspace -Runspace $script:RunspaceA -Script $script:GetHostname
+        $inB = Invoke-InRunspace -Runspace $script:RunspaceB -Script $script:GetHostname
+        $inA[0] | Should -Be 'runspace-a.example'
+        $inB[0] | Should -Be '<none>'
+    }
+}