diff --git a/docs/WINDOWS-COLLECTOR-RELIABILITY.md b/docs/WINDOWS-COLLECTOR-RELIABILITY.md
new file mode 100644
index 0000000..99c448f
--- /dev/null
+++ b/docs/WINDOWS-COLLECTOR-RELIABILITY.md
@@ -0,0 +1,123 @@
+# Windows collector reliability validation — 2026-10-30
+
+## Root causes
+
+The supplied Server 2025 assessment reported tasks failed and 16 certificate
+errors, but its generic errors did not retain exception types. Read-only native
+reproduction established two defects:
+
+* Tasks: one action executable made .NET Framework `Path.GetFileName` throw a
+  `MethodInvocationException` wrapping `ArgumentException`. The projection was
+  inside a single assignment/query catch, so that one value discarded all tasks.
+* Certificates: the Windows certificate provider returned store `PSPath` values
+  such as `Microsoft.PowerShell.Security\Certificate::My`, without LocalMachine.
+  Using those paths produced `ItemNotFoundException` / `ObjectNotFound` for each
+  store. Store-list success alone incorrectly gave partial credit when every
+  store query failed.
+
+The original code already enumerated stores separately; recursion was not the
+cause. Missing modules and JSON conversion were checked as failure paths, but
+were not the reproduced causes on this host.
+
+## Changes
+
+Executable basenames now use string operations and the existing strict allowlist,
+avoiding filesystem path validation. Malformed values become an omission marker;
+task records remain visible. Each task is projected and JSON-checked separately.
+Principal group accounts are used when UserId is absent. Arguments, XML, inline
+scripts, event queries and credentials are never projected.
+
+Certificates use explicit `Cert:\LocalMachine\<store>` paths. Each store query
+and certificate projection is isolated; empty successful stores receive credit,
+inaccessible stores produce errors, and listing names alone does not give credit
+when all listed stores fail. Only subject, issuer, thumbprint, expiration and
+store are collected. No private key or certificate export APIs are used.
+
+Read helpers promote nonterminating errors to terminating errors. Per-record JSON
+checks reject unrepresentable records. Final JSON failures exit with code 3 and
+Python records `serialization_failed`, never a successful empty collection.
+Existing subprocess timeout, UTF-8, output limits and schema validation remain.
+
+Optional `-Diagnostic` / Python `--diagnostic` adds exception class and category to
+existing sanitized error messages. Fixed command stages appear in error scope.
+No raw messages, task names, arguments, store names, targets, stack traces or
+error identifiers are included in diagnostics. Inventory remains sensitive and
+should be stored privately. Task/certificate UI detail pages display these error
+scopes, codes and messages; Collection checks and reports retain their contract.
+
+The production Python backend deliberately continues to use trusted Windows
+PowerShell 5.1. Direct PowerShell 7 invocation also includes the inbox Windows
+module directory, without opening module lookup to user directories. Commands
+autoload from those inbox module paths; missing commands are explicit failures.
+No scoring policy, Linux collector or other inventory module was changed.
+
+## Results
+
+On the local Windows Server 2025 host, native 5.1 collection returned:
+
+| Collector | Status | Records | Errors |
+| --- | --- | ---: | ---: |
+| Tasks | complete | 192 (46 disabled) | 0 |
+| Certificates | complete | 49 across 7 populated stores | 0 |
+
+Full Python subprocess collection passed schema validation, returned the same
+record counts, and completed all nine checks. Evidence coverage rose from the
+supplied assessment's 81% to 100%. Confidence remained moderate under the existing
+classification policy; complete collection does not establish retirement safety.
+
+`python -m unittest discover -s tests -v`: **64 tests, 62 passed, 2 skipped**.
+Skips: the Linux-only subprocess test on Windows and PowerShell 7 (not installed).
+UI navigation/history/export tests, Linux parsing tests, scoring regressions,
+Windows subprocess limits and schema tests passed. Native PowerShell AST and
+synthetic tests passed under 5.1. Added cases cover normal/disabled/empty tasks,
+malformed actions, per-task failures, nonterminating query denial, multiple and
+empty stores, partial/all-store denial, redacted diagnostics and serialization
+failures. A dedicated regression checks lower coverage/confidence without risk
+inflation for failed tasks and partial certificates.
+
+## Exact validation commands
+
+Run from the repository root in an authorized elevated Windows PowerShell console.
+These commands only read inventory; they do not change Server configuration or
+execution policy. Choose a new output path for each saved inventory.
+
+```powershell
+$PSVersionTable.PSVersion
+powershell.exe -NoLogo -NoProfile -NonInteractive -File .\tests\powershell\Test-Collectors.ps1
+python -m unittest discover -s tests -v
+
+foreach ($section in @('tasks', 'certificates')) {
+    $raw = & powershell.exe -NoLogo -NoProfile -NonInteractive -File .\powershell\Get-ServerInventory.ps1 -Section $section -Diagnostic
+    if ($LASTEXITCODE -ne 0) { throw 'Collector process failed' }
+    $r = $raw | ConvertFrom-Json
+    [pscustomobject]@{
+        Section = $section
+        Status = $r.status
+        Records = @($r.data).Count
+        Errors = $r.errors
+    } | ConvertTo-Json -Depth 5
+    if ($r.status -ne 'complete') { throw 'Review incomplete collection' }
+    if (@($r.data).Count -eq 0) { throw 'No records: verify actual host contents independently' }
+}
+
+python -m samsara.collectors.windows --diagnostic --output .\windows-validation-new.json
+python .\tools\validate_windows_host.py --output-dir .\windows-validation-new
+
+# When PowerShell 7 is already installed:
+pwsh.exe -NoLogo -NoProfile -NonInteractive -File .\tests\powershell\Test-Collectors.ps1
+pwsh.exe -NoLogo -NoProfile -NonInteractive -File .\powershell\Get-ServerInventory.ps1 -Section tasks -Diagnostic
+pwsh.exe -NoLogo -NoProfile -NonInteractive -File .\powershell\Get-ServerInventory.ps1 -Section certificates -Diagnostic
+```
+
+The nonempty assertion above is a validation expectation for this host, not a
+collector rule: legitimately empty successful queries remain complete.
+
+## Remaining limitations
+
+PowerShell 7 runtime execution and other Server releases were not available for
+live validation. Tests run under each runtime when installed; 5.1 syntax and
+Server 2016/2019/2022/2025 identity fixtures pass. Access restrictions may hide
+objects even when an API reports success. A terminating failure of the initial
+task enumeration cannot recover task registrations the API never returned, and
+is reported failed. Inventory is a current observation, not historical activity.
+No Windows Server configuration was modified.
diff --git a/powershell/Get-ServerCertificates.ps1 b/powershell/Get-ServerCertificates.ps1
index 1b1883f..d2ac87e 100644
--- a/powershell/Get-ServerCertificates.ps1
+++ b/powershell/Get-ServerCertificates.ps1
@@ -4,12 +4,23 @@ function Get-SamsaraCertificates {
     Invoke-SamsaraRead $Result 'Local machine certificate store list' {
         $collection.stores = @(Get-ChildItem -LiteralPath 'Cert:\LocalMachine' -ErrorAction Stop)
     }
+    # Listing store names is not evidence that any listed store was readable.
+    if ($collection.stores.Count -gt 0) { $Result.successful_subchecks-- }
     foreach ($store in $collection.stores) {
-        Invoke-SamsaraRead $Result 'Local machine public certificate metadata' {
-            Get-ChildItem -LiteralPath $store.PSPath -ErrorAction Stop | ForEach-Object {
-                $Result.data += [pscustomobject]@{ subject = [string]$_.Subject; issuer = [string]$_.Issuer
-                    expires = $_.NotAfter.ToUniversalTime().ToString('o'); thumbprint = [string]$_.Thumbprint
-                    store = [string]$store.PSChildName }
+        # Certificate provider PSPath may omit LocalMachine (including on 5.1).
+        # Construct an explicit provider path from the enumerated store name.
+        $storeName = [string]$store.PSChildName
+        Invoke-SamsaraRead $Result 'Certificate store query' {
+            if ($storeName -notmatch '^[A-Za-z0-9_. -]+$') { throw 'Invalid store name' }
+            $certificates = @(Get-ChildItem -LiteralPath ('Cert:\LocalMachine\' + $storeName) -ErrorAction Stop)
+            foreach ($certificate in $certificates) {
+                Invoke-SamsaraRead $Result 'Certificate metadata projection' {
+                $row = [pscustomobject]@{ subject = [string]$certificate.Subject; issuer = [string]$certificate.Issuer
+                    expires = $certificate.NotAfter.ToUniversalTime().ToString('o'); thumbprint = [string]$certificate.Thumbprint
+                    store = $storeName }
+                $null = ConvertTo-Json -InputObject $row -Depth 4 -ErrorAction Stop
+                $Result.data += $row
+                }
             }
         }
     }
diff --git a/powershell/Get-ServerInventory.ps1 b/powershell/Get-ServerInventory.ps1
index e0fe25f..e7aefed 100644
--- a/powershell/Get-ServerInventory.ps1
+++ b/powershell/Get-ServerInventory.ps1
@@ -1,12 +1,17 @@
 #requires -Version 5.1
 [CmdletBinding()]
-param([ValidateSet('all','system','roles','services','network','tasks','software','storage','shares','certificates')][string]$Section = 'all')
+param([ValidateSet('all','system','roles','services','network','tasks','software','storage','shares','certificates')][string]$Section = 'all', [switch]$Diagnostic)
 
 $ErrorActionPreference = 'Stop'
 $ProgressPreference = 'SilentlyContinue'
 $WarningPreference = 'SilentlyContinue'
 $InformationPreference = 'SilentlyContinue'
 $env:PSModulePath = Join-Path $PSHOME 'Modules'
+if ($PSVersionTable.PSEdition -eq 'Core') {
+    # Inbox Windows modules remain under WindowsPowerShell when invoked from PS7.
+    $env:PSModulePath += ';' + (Join-Path ([Environment]::SystemDirectory) 'WindowsPowerShell\v1.0\Modules')
+}
+$script:SamsaraDiagnostic = $Diagnostic.IsPresent
 [Console]::OutputEncoding = New-Object System.Text.UTF8Encoding($false)
 if ([Environment]::OSVersion.Platform -ne [PlatformID]::Win32NT) {
     [Console]::Error.WriteLine('This collector requires a local Windows Server execution host.')
@@ -30,7 +35,7 @@ $collectors = [ordered]@{
 }
 if ($Section -ne 'all') {
     $result = Invoke-SamsaraSection $Section $collectors[$Section]
-    ConvertTo-Json -InputObject $result -Depth 12 -Compress
+    ConvertTo-SamsaraJson $result 12
     exit 0
 }
 # Direct PowerShell use emits the same complete inventory envelope as the Python backend.
@@ -50,7 +55,7 @@ foreach ($name in $collectors.Keys) {
     } elseif ($name -eq 'shares') { $inventory.storage += @($result.data) }
     else { $inventory[$name] = @($result.data) }
 }
-ConvertTo-Json -InputObject ([ordered]@{ schema_version='1.0'; synthetic=$false; collected_at=$collectedAt
-    server=$server; checks=$checks; inventory=$inventory }) -Depth 14 -Compress
+ConvertTo-SamsaraJson ([ordered]@{ schema_version='1.0'; synthetic=$false; collected_at=$collectedAt
+    server=$server; checks=$checks; inventory=$inventory }) 14
 
 exit 0
diff --git a/powershell/Get-ServerTasks.ps1 b/powershell/Get-ServerTasks.ps1
index 796576d..733fc6b 100644
--- a/powershell/Get-ServerTasks.ps1
+++ b/powershell/Get-ServerTasks.ps1
@@ -1,8 +1,10 @@
 function Get-SamsaraTasks {
     param($Result)
     Invoke-SamsaraRead $Result 'Scheduled tasks' {
-        $Result.data = @(Get-ScheduledTask -ErrorAction Stop | ForEach-Object {
-            $task = $_
+        $tasks = @(Get-ScheduledTask -ErrorAction Stop)
+        foreach ($task in $tasks) {
+          Invoke-SamsaraRead $Result 'Scheduled task metadata projection' {
+            if ($null -eq $task -or [string]::IsNullOrEmpty([string]$task.TaskName)) { throw 'Missing task identity' }
             $triggers = @($task.Triggers | ForEach-Object {
                 $type = if ($_.CimClass) { [string]$_.CimClass.CimClassName } else { 'Unknown trigger' }
                 # Select only known scheduler metadata; never serialize entire CIM objects.
@@ -10,11 +12,14 @@ function Get-SamsaraTasks {
                 '{0}; start={1}; enabled={2}; daysInterval={3}; weeksInterval={4}; daysOfWeek={5}; repeat={6}' -f $type, $_.StartBoundary, $_.Enabled, $_.DaysInterval, $_.WeeksInterval, $_.DaysOfWeek, $repetition
             })
             $executables = @($task.Actions | ForEach-Object { Get-SamsaraSafeExecutable ([string]$_.Execute) })
-            [pscustomobject]@{ name = [string]$task.TaskName; path = [string]$task.TaskPath
+            $row = [pscustomobject]@{ name = [string]$task.TaskName; path = [string]$task.TaskPath
                 enabled = [bool]$task.Settings.Enabled; state = [string]$task.State
-                account = [string]$task.Principal.UserId; executables = ($executables -join '; ')
+                account = if ($task.Principal.UserId) { [string]$task.Principal.UserId } else { [string]$task.Principal.GroupId }; executables = ($executables -join '; ')
                 triggers = if ($triggers.Count) { $triggers -join ' | ' } else { 'No trigger metadata visible; manual or external invocation remains possible' } }
-        })
+            $null = ConvertTo-Json -InputObject $row -Depth 4 -ErrorAction Stop
+            $Result.data += $row
+          }
+        }
     }
     $Result.limitations += 'Visible Task Scheduler registrations only. Arguments, inline scripts, task XML, event queries and execution history are omitted. Non-executable actions may lack an executable name. Trigger fields are descriptive, not a prediction of execution.'
 }
diff --git a/powershell/Inventory.Common.ps1 b/powershell/Inventory.Common.ps1
index 765bb02..8bab72e 100644
--- a/powershell/Inventory.Common.ps1
+++ b/powershell/Inventory.Common.ps1
@@ -13,6 +13,13 @@ function Add-SamsaraError {
         'command_unavailable' { 'Required local inventory command is unavailable.' }
         default { 'Local query could not complete; raw diagnostics are excluded.' }
     }
+    if ($script:SamsaraDiagnostic) {
+        # Fixed stages only; never include messages, identifiers, targets or stacks.
+        $type = $Record.Exception.GetType().Name
+        if ($type -notmatch '^[A-Za-z0-9]+Exception$') { $type = 'Exception' }
+        $category = [string]$Record.CategoryInfo.Category
+        $message += ' Exception type: ' + $type + '; category: ' + $category + '.'
+    }
     $Result.errors += [pscustomobject]@{ code = $code; scope = $Scope; message = $message }
     if ($code -eq 'access_denied') { $Result.permission_limitations += $Scope + ': read access denied.' }
 }
@@ -21,15 +28,28 @@ function Invoke-SamsaraRead {
     param($Result, [string]$Scope, [scriptblock]$Query)
     $Result.attempted_subchecks++
     try {
+        $ErrorActionPreference = 'Stop'
         & $Query
         $Result.successful_subchecks++
     } catch { Add-SamsaraError $Result $_ $Scope }
 }
 
+function ConvertTo-SamsaraJson {
+    param($Value, [int]$Depth = 14)
+    try { ConvertTo-Json -InputObject $Value -Depth $Depth -Compress -ErrorAction Stop }
+    catch {
+        # A serialization failure must not emit a complete empty inventory.
+        [Console]::Error.WriteLine('Inventory JSON serialization failed; raw diagnostics are excluded.')
+        exit 3
+    }
+}
+
 function Get-SamsaraSafeExecutable {
     param([string]$Value)
     # Task action arguments, scripts and environment values are deliberately omitted.
-    $name = [IO.Path]::GetFileName(($Value -replace '\\', '/'))
+    # Scheduler action values need not be valid filesystem paths. Path.GetFileName
+    # throws on malformed/quoted values in .NET Framework (PowerShell 5.1).
+    $name = (($Value -replace '\\', '/') -split '/')[-1]
     if ($name -match '^[A-Za-z0-9_. -]+\.(exe|com|cmd|bat|ps1|vbs|js|wsf|msc)$') { return $name }
     return '[executable name omitted]'
 }
diff --git a/samsara/collectors/windows.py b/samsara/collectors/windows.py
index 8915bad..e22fa5b 100644
--- a/samsara/collectors/windows.py
+++ b/samsara/collectors/windows.py
@@ -48,12 +48,14 @@ def powershell_executable():
     return executable
 
 
-def run_section(section, executable, cancelled=lambda: False, timeout=45):
+def run_section(section, executable, cancelled=lambda: False, timeout=45, diagnostic=False):
     if section not in SECTIONS:
         raise ValueError('Unknown Windows inventory section.')
     if cancelled():
         raise CollectionCancelled()
     args = [str(executable), '-NoLogo', '-NoProfile', '-NonInteractive', '-File', str(SCRIPT), '-Section', section]
+    if diagnostic:
+        args.append('-Diagnostic')
     environment = os.environ.copy()
     # Only inbox modules are needed. Do not autoload user-supplied modules or profiles.
     environment['PSModulePath'] = str(Path(executable).parent / 'Modules')
@@ -77,6 +79,8 @@ def run_section(section, executable, cancelled=lambda: False, timeout=45):
             if cancelled():
                 raise CollectionCancelled()
             if process.returncode:
+                if process.returncode == 3:
+                    raise WindowsCollectionError('serialization_failed', 'PowerShell could not serialize inventory metadata; no successful evidence was substituted.')
                 raise WindowsCollectionError('powershell_failed', 'The trusted script could not run. Check script signing policy, module availability and read permissions; raw diagnostics are excluded.')
             output.seek(0)
             raw = output.read(MAX_OUTPUT + 1)
@@ -127,7 +131,7 @@ def failure_check(code, message, section, start, status='failed'):
 
 
 def collect_local_windows(stage=lambda message: None, cancelled=lambda: False, profile='auto',
-                          section_timeout=45, total_timeout=300, runner=None):
+                          section_timeout=45, total_timeout=300, runner=None, diagnostic=False):
     if platform.system() != 'Windows':
         raise ValueError('Local Windows collection requires an authorized Windows Server execution host.')
     if profile != 'auto' and not profile.startswith('windows:'):
@@ -150,7 +154,10 @@ def collect_local_windows(stage=lambda message: None, cancelled=lambda: False, p
                 raise ValueError('The Windows identity check could not run within the time limit.')
             continue
         try:
-            record = validate_section(runner(section, executable, cancelled=cancelled, timeout=min(section_timeout, remaining)), section)
+            options = {'cancelled': cancelled, 'timeout': min(section_timeout, remaining)}
+            if diagnostic:
+                options['diagnostic'] = True
+            record = validate_section(runner(section, executable, **options), section)
             total_bytes += len(json.dumps(record).encode('utf-8'))
             if total_bytes > MAX_OUTPUT:
                 raise WindowsCollectionError('output_limit', 'Total inventory exceeded the 10 MiB limit; this section was omitted.')
@@ -178,10 +185,11 @@ def collect_local_windows(stage=lambda message: None, cancelled=lambda: False, p
 def main():
     parser = argparse.ArgumentParser(description='Read-only local Windows Server inventory. No remoting is used.')
     parser.add_argument('--output', required=True, help='New local JSON file to create')
+    parser.add_argument('--diagnostic', action='store_true', help='Include sanitized exception types and categories')
     parser.add_argument('--profile', choices=['auto','windows:2016','windows:2019','windows:2022','windows:2025'], default='auto')
     args = parser.parse_args()
     try:
-        data = collect_local_windows(profile=args.profile)
+        data = collect_local_windows(profile=args.profile, diagnostic=args.diagnostic)
         with open(args.output, 'x', encoding='utf-8') as output:
             json.dump(data, output, indent=2)
         print('Windows inventory saved. Review all failed/partial checks and permission limitations before retirement decisions.')
diff --git a/samsara/ui/window.py b/samsara/ui/window.py
index 29d8193..11c7cb1 100644
--- a/samsara/ui/window.py
+++ b/samsara/ui/window.py
@@ -476,6 +476,8 @@ class MainWindow(QMainWindow):
         if key in self.data['checks']:
             check = self.data['checks'][key]
             area.addWidget(self.label(f"{check['status'].replace('_', ' ').title()}: {check['message']}", muted=True))
+            for error in check.get('errors', []):
+                area.addWidget(self.label(f"{error['scope']} [{error['code']}]: {error['message']}", muted=True))
         area.addWidget(SearchTable(rows))
 
     def job_finished(self):
diff --git a/tests/powershell/Test-Collectors.ps1 b/tests/powershell/Test-Collectors.ps1
index 1291bef..598dbc3 100644
--- a/tests/powershell/Test-Collectors.ps1
+++ b/tests/powershell/Test-Collectors.ps1
@@ -82,3 +82,63 @@ $script:SamsaraIsElevated=$false
 $section=Invoke-SamsaraSection 'services' {param($r) Get-SamsaraServices $r}
 Assert-True ($section.status -eq 'partial' -and $section.permission_limitations.Count -gt 0) 'Non-elevated scope not marked partial'
 Write-Output 'PowerShell AST and synthetic collector tests passed. No real Windows inventory was collected.'
+# Reliability cases: mocks never access real tasks, certificates or private keys.
+$script:SamsaraIsElevated=$true
+$script:SamsaraDiagnostic=$true
+function New-TestTask {
+    param([bool]$Enabled=$true)
+    [pscustomobject]@{TaskName='Example';TaskPath='\';State='Ready';Settings=[pscustomobject]@{Enabled=$Enabled};Principal=[pscustomobject]@{UserId='SYSTEM'};Actions=@([pscustomobject]@{Execute='"C:\Tools\bad.exe"';Arguments='SECRET'});Triggers=@()}
+}
+function Get-ScheduledTask { [CmdletBinding()]param() New-TestTask $true; New-TestTask $false }
+$r=Invoke-SamsaraSection tasks {param($r) Get-SamsaraTasks $r}
+Assert-True ($r.status -eq 'complete' -and $r.data.Count -eq 2 -and -not $r.data[1].enabled) 'Normal/disabled tasks lost'
+Assert-True ($r.data[0].executables -eq '[executable name omitted]') 'Malformed executable not sanitized'
+function Get-ScheduledTask { [CmdletBinding()]param() }
+$r=Invoke-SamsaraSection tasks {param($r) Get-SamsaraTasks $r}
+Assert-True ($r.status -eq 'complete' -and $r.data.Count -eq 0) 'Successful empty task query failed'
+function Get-ScheduledTask { [CmdletBinding()]param() Write-Error 'SECRET' -Category PermissionDenied }
+$r=Invoke-SamsaraSection tasks {param($r) Get-SamsaraTasks $r}
+Assert-True ($r.status -eq 'failed' -and $r.data.Count -eq 0) 'Failed task query treated as empty success'
+function Get-ScheduledTask {
+    [CmdletBinding()]param()
+    New-TestTask
+    $bad=New-TestTask
+    $bad | Add-Member ScriptProperty TaskName { throw [UnauthorizedAccessException]::new('SECRET') } -Force
+    # Throw from ToString to reliably exercise projection failures on both runtimes.
+    $value=New-Object PSObject
+    $value | Add-Member ScriptMethod ToString { throw [UnauthorizedAccessException]::new('SECRET') } -Force
+    $bad.TaskPath=$value
+    $bad
+}
+$r=Invoke-SamsaraSection tasks {param($r) Get-SamsaraTasks $r}
+Assert-True ($r.status -eq 'partial' -and $r.data.Count -eq 1 -and $r.errors.Count -gt 0) 'Individual task failure discarded healthy records'
+Assert-True (($r | ConvertTo-Json -Depth 12) -notmatch 'SECRET') 'Diagnostic leaked secret'
+$script:StoreMode='normal'
+function Get-ChildItem {
+    [CmdletBinding()]param($LiteralPath)
+    if ($LiteralPath -eq 'Cert:\LocalMachine') {
+        foreach ($n in @('My','Root','Empty')) { [pscustomobject]@{PSChildName=$n;PSPath=('Microsoft.PowerShell.Security\Certificate::'+$n)} }
+    } elseif ($LiteralPath -eq 'Cert:\LocalMachine\Empty') { return }
+    elseif ($LiteralPath -in @('Cert:\LocalMachine\My','Cert:\LocalMachine\Root')) {
+        if ($script:StoreMode -eq 'denied' -or ($script:StoreMode -eq 'partial' -and $LiteralPath -like '*Root')) { throw [UnauthorizedAccessException]::new('SECRET') }
+        [pscustomobject]@{Subject='CN=Example';Issuer='CN=CA';Thumbprint='00';NotAfter=[datetime]::UtcNow;PrivateKey='SECRET'}
+    } else { throw 'Incorrect certificate provider path' }
+}
+$r=Invoke-SamsaraSection certificates {param($r) Get-SamsaraCertificates $r}
+Assert-True ($r.status -eq 'complete' -and $r.data.Count -eq 2 -and @($r.data.store | Select-Object -Unique).Count -eq 2) 'Multiple stores/empty store failed'
+$script:StoreMode='partial'
+$r=Invoke-SamsaraSection certificates {param($r) Get-SamsaraCertificates $r}
+Assert-True ($r.status -eq 'partial' -and $r.data.Count -eq 1 -and $r.errors[0].code -eq 'access_denied') 'Partial store failure lost records'
+Assert-True (($r | ConvertTo-Json -Depth 12) -notmatch 'SECRET') 'Certificate diagnostics leaked secret'
+function Get-ChildItem { [CmdletBinding()]param($LiteralPath) if ($LiteralPath -eq 'Cert:\LocalMachine') { [pscustomobject]@{PSChildName='My'} } else { throw [UnauthorizedAccessException]::new('SECRET') } }
+$r=Invoke-SamsaraSection certificates {param($r) Get-SamsaraCertificates $r}
+Assert-True ($r.status -eq 'failed' -and $r.data.Count -eq 0) 'Inaccessible stores treated as empty success'
+function Get-ChildItem { [CmdletBinding()]param($LiteralPath) }
+$r=Invoke-SamsaraSection certificates {param($r) Get-SamsaraCertificates $r}
+Assert-True ($r.status -eq 'complete' -and $r.data.Count -eq 0) 'Empty store list failed'
+function Get-ScheduledTask { [CmdletBinding()]param() New-TestTask }
+function ConvertTo-Json { [CmdletBinding()]param($InputObject,$Depth,[switch]$Compress) throw [InvalidOperationException]::new('SECRET serialization') }
+$r=Invoke-SamsaraSection tasks {param($r) Get-SamsaraTasks $r}
+Assert-True ($r.status -ne 'complete' -and $r.data.Count -eq 0 -and $r.errors.Count -eq 1) 'Serialization failure accepted as evidence'
+Remove-Item Function:\ConvertTo-Json
+Write-Output 'Reliability collector tests passed.'
diff --git a/tests/test_powershell.py b/tests/test_powershell.py
index c2a5c67..2f1d9b9 100644
--- a/tests/test_powershell.py
+++ b/tests/test_powershell.py
@@ -8,6 +8,12 @@ import unittest
 class PowerShellTests(unittest.TestCase):
     def test_native_ast_and_synthetic_collectors(self):
         executable = shutil.which('powershell.exe') if os.name == 'nt' else shutil.which('pwsh')
+        self.run_collectors(executable)
+
+    def test_powershell_7_collectors(self):
+        self.run_collectors(shutil.which('pwsh'))
+
+    def run_collectors(self, executable):
         if not executable:
             self.skipTest('No PowerShell runtime available; native AST/collector tests require Windows PowerShell 5.1 or pwsh.')
         script=Path('tests/powershell/Test-Collectors.ps1').resolve()
diff --git a/tests/test_scoring.py b/tests/test_scoring.py
index b4941c4..2e17297 100644
--- a/tests/test_scoring.py
+++ b/tests/test_scoring.py
@@ -20,6 +20,17 @@ def scored(result):
 
 
 class ScoringRegressionTests(unittest.TestCase):
+    def test_task_and_certificate_failures_reduce_coverage_without_risk(self):
+        data = fixture('clean_windows')
+        baseline = assess(data)
+        for name, status in [('tasks', 'failed'), ('certificates', 'partial')]:
+            data['checks'][name]['status'] = status
+            data['checks'][name]['errors'] = [{'code': 'collection_failed', 'scope': name, 'message': 'Sanitized failure'}]
+        result = assess(data)
+        self.assertEqual(result['score'], baseline['score'])
+        self.assertLess(result['coverage']['percent'], baseline['coverage']['percent'])
+        self.assertEqual(result['confidence']['level'], 'moderate')
+
     def test_required_scenarios(self):
         expected = {'clean_windows':0,'inactive_game_server':0,'active_sql_server':70,
                     'active_iis_server':70,'domain_controller':95,'active_file_server':80,
diff --git a/tests/test_windows.py b/tests/test_windows.py
index 8836471..f4b0caa 100644
--- a/tests/test_windows.py
+++ b/tests/test_windows.py
@@ -155,6 +155,19 @@ class FakeProcess:
 
 
 class ProcessTests(unittest.TestCase):
+    def test_serialization_exit_and_diagnostic_switch(self):
+        def create(args, **kwargs):
+            self.assertIn('-Diagnostic', args)
+            process = FakeProcess(args, **kwargs)
+            process.returncode = 3
+            kwargs['stdout'].write(b'SECRET')
+            return process
+        with patch('samsara.collectors.windows.subprocess.Popen', side_effect=create):
+            with self.assertRaises(WindowsCollectionError) as error:
+                run_section('tasks', 'powershell.exe', diagnostic=True)
+            self.assertEqual(error.exception.code, 'serialization_failed')
+            self.assertNotIn('SECRET', str(error.exception))
+
     def test_timeout_and_cancel_kill_and_reap_without_shell(self):
         for cancel in [False,True]:
             processes=[]