diff --git a/CI/cleanupIssues.graphql b/CI/cleanupIssues.graphql
new file mode 100644
index 0000000..020c77a
--- /dev/null
+++ b/CI/cleanupIssues.graphql
@@ -0,0 +1,41 @@
+query(
+  $owner: String!
+  $repo: String!
+  $author: String
+  $first: Int = 100 # GitHub limit
+  $after: String = null
+) {
+  repository(owner: $owner, name: $repo) {
+    issues(
+      states: CLOSED
+      orderBy: {field: CREATED_AT, direction: ASC}
+      filterBy: {createdBy: $author}
+      first: $first
+      after: $after
+    ) {
+      totalCount
+      pageInfo { hasNextPage, endCursor }
+      edges {
+        node {
+          id
+          number
+          title
+          state
+          stateReason
+          author { login, __typename }
+          timelineItems(first: 20) {
+            totalCount
+            edges {
+              node {
+                __typename
+                ... on ClosedEvent {
+                  closer { __typename }
+                }
+              }
+            }
+          }
+        }
+      }
+    }
+  }
+}
diff --git a/CI/cleanupIssues.ps1 b/CI/cleanupIssues.ps1
new file mode 100644
index 0000000..559ecb1
--- /dev/null
+++ b/CI/cleanupIssues.ps1
@@ -0,0 +1,239 @@
+# Copyright (c) 2024 Matthias Wolf, Mawosoft.
+
+<#
+.SYNOPSIS
+    Delete obsolete bot-created issues.
+.DESCRIPTION
+    Deletes obsolete issues created by a specified author or any bot.
+.OUTPUTS
+    A single result object with properties Issues, Errors, and RateLimit.
+.NOTES
+    An issue is considered obsolete and therefore deletable if:
+    - The issue has been created by the specified author, or by any bot if no author is specified.
+    - The issue has been closed as 'not planned', or -AnyClosed has been specified.
+    - The issue doesn't have any comments and is not referenced anywhere.
+#>
+
+#Requires -Version 7.4
+
+using namespace System
+using namespace System.Collections
+using namespace System.Collections.Generic
+using namespace System.Text
+
+[CmdletBinding(PositionalBinding = $false, SupportsShouldProcess = $true)]
+param(
+
+    # The name of the repository to process.
+    [Parameter(Mandatory, Position = 0)]
+    [ValidateNotNullOrEmpty()]
+    [string]$Repo,
+
+    # The owner of the repository to process (default: 'mawosoft').
+    [ValidateNotNullOrEmpty()]
+    [string]$Owner = 'mawosoft',
+
+    # Pre-filter for issues created by the specified author (default: 'github-actions[bot]').
+    # If set to null or empty, any issue created by a bot is a candidate (post-filter).
+    [string]$Author = 'github-actions[bot]',
+
+    # Any closed issue is a candidate, not just those closed as 'not planned'.
+    [switch]$AnyClosed,
+
+    # The GitHub token to use for authentication.
+    [Parameter(Mandatory)]
+    [ValidateNotNullOrEmpty()]
+    [securestring]$Token
+)
+
+$query = Get-Content -LiteralPath "$PSScriptRoot/cleanupIssues.graphql" -Raw
+$requestBody = [PSCustomObject]@{
+    operationName = $null
+    query         = $query
+    variables     = @{
+        owner  = $Owner
+        repo   = $Repo
+        author = $Author ? $Author : $null
+        first  = 100 # GitHub limit
+        after  = $null
+    }
+}
+
+$params = @{
+    Uri            = 'https://api.github.com/graphql'
+    Authentication = 'Bearer'
+    Token          = $Token
+    Method         = 'Post'
+    Body           = $null
+    ContentType    = 'application/json'
+}
+
+[HashSet[string]]$nonDeletableEvents = @(
+    'ReferencedEvent'
+    'CrossReferencedEvent'
+    'IssueComment'
+)
+
+$resultObject = [PSCustomObject]@{
+    Issues    = [ArrayList]::new()
+    Errors    = [ArrayList]::new()
+    RateLimit = [PSCustomObject]@{
+        Remaining = $null
+        Reset     = $null
+    }
+}
+
+function InvokeWebRequest {
+    param([hashtable]$params)
+    $response = $null
+    $result = $null
+    try {
+        if ($resultObject.RateLimit.Remaining -eq 0) {
+            throw 'Rate limit reached.'
+        }
+        $response = Invoke-WebRequest @params -SkipHttpErrorCheck -ProgressAction SilentlyContinue
+        try {
+            $remaining = $response.Headers['X-RateLimit-Remaining']?[0]
+            if ($null -ne $remaining) {
+                $resultObject.RateLimit.Remaining = [int]$remaining
+            }
+            $reset = $response.Headers['X-RateLimit-Reset']?[0]
+            if ($null -ne $reset) {
+                $resultObject.RateLimit.Reset = [datetime]::new(
+                    [long]$reset * [timespan]::TicksPerSecond + [datetime]::UnixEpoch.Ticks,
+                    [DateTimeKind]::Utc).ToLocalTime()
+            }
+        }
+        catch {}
+        $result = $response.Content | ConvertFrom-Json -Depth 64 -AsHashtable -NoEnumerate
+    }
+    catch {
+        $result = @{
+            errors = @(@{
+                    message            = "$_"
+                    ResponseRawContent = ${response}?.RawContent
+                })
+        }
+    }
+    return $result
+}
+
+try {
+    $pageInfo = @{
+        hasNextPage = $true
+        endCursor   = $null
+    }
+
+    while ($pageInfo.hasNextPage) {
+        $requestBody.variables.after = $pageInfo.endCursor
+        $params.Body = $requestBody | ConvertTo-Json -Compress -EscapeHandling EscapeNonAscii
+        $result = InvokeWebRequest $params
+        if (${result}?['errors']) {
+            $resultObject.Errors.AddRange($result['errors'])
+        }
+        if (-not ${result}?['data']) {
+            break
+        }
+        $issues = $result['data']?['repository']?['issues']
+        $pageInfo = $issues['pageInfo']
+        foreach ($node in $issues['edges']) {
+            $issue = $node['node']
+            [bool]$canDelete = $true
+            if (-not $Author -and $issue['author']['__typename'] -cne 'Bot') {
+                $canDelete = $false
+            }
+            elseif (-not $AnyClosed -and $issue['stateReason'] -cne 'NOT_PLANNED') {
+                $canDelete = $false
+            }
+            elseif ($issue['timelineItems']['totalCount'] -gt $issue['timelineItems']['edges'].Length) {
+                $canDelete = $false
+            }
+            else {
+                foreach ($item in $issue['timelineItems']['edges']) {
+                    $typeName = $item['node']['__typename']
+                    if ($typeName -ceq 'ClosedEvent') {
+                        if ($null -ne $item['node']['closer']) {
+                            # Closed by a commit or PR.
+                            $canDelete = $false
+                            break
+                        }
+                    }
+                    elseif ($nonDeletableEvents.Contains($typeName)) {
+                        $canDelete = $false
+                        break
+                    }
+                }
+            }
+            if ($canDelete) {
+                $null = $resultObject.Issues.Add([PSCustomObject]@{
+                        Id           = $issue['id']
+                        Number       = $issue['number']
+                        Title        = $issue['title']
+                        State        = $issue['state'] + ':' + $issue['stateReason']
+                        Author       = $issue['author']['login']
+                        Timeline     = $issue['timelineItems']['edges'].ForEach({ $_['node']['__typename'] }) -join ','
+                        DeleteStatus = 'pending'
+                    })
+            }
+        }
+    }
+
+    if ($resultObject.Errors.Count -eq 0 -and $resultObject.Issues.Count -ne 0 -and
+        $PSCmdlet.ShouldProcess("$Owner/$Repo", "Delete $($resultObject.Issues.Count) issues")) {
+        # deleteIssue mutation may time out if there are too many in a single request.
+        [int]$chunkSize = 10
+        $sb = [StringBuilder]::new()
+        $nodeVariables = [ArrayList]::new($chunkSize)
+        for ([int]$issueIndex = 0; $issueIndex -lt $resultObject.Issues.Count; $issueIndex += $chunkSize) {
+            [int]$chunkEnd = $resultObject.Issues.Count
+            if (($chunkEnd - $issueIndex) -gt $chunkSize) { $chunkEnd = $issueIndex + $chunkSize }
+            $nodeVariables.Clear()
+            $null = $sb.Clear().AppendLine('mutation {')
+            for ([int]$i = $issueIndex; $i -lt $chunkEnd; $i++) {
+                $issue = $resultObject.Issues[$i]
+                $issue.DeleteStatus = 'sent'
+                $null = $sb.Append('  d').Append($i).Append(': deleteIssue(input: {issueId: "')
+                $null = $sb.Append($issue.Id).AppendLine('"}) { clientMutationId }')
+                $null = $nodeVariables.Add($issue.Id)
+            }
+            $null = $sb.AppendLine('}')
+            $requestBody.variables = $null
+            $requestBody.query = $sb.ToString()
+            $params.Body = $requestBody | ConvertTo-Json -Compress -EscapeHandling EscapeNonAscii
+            $result = InvokeWebRequest $params
+            if (${result}?['errors']) {
+                $resultObject.Errors.AddRange($result['errors'])
+            }
+            # GitHub may silently fail to delete issues (even via the Web interface).
+            # Verify deletion by querying the issue nodes by id.
+            $requestBody.variables = @{ ids = $nodeVariables }
+            $requestBody.query = @'
+query ($ids: [ID!]!) {
+    nodes(ids: $ids) { id, __typename }
+}
+'@
+            $params.Body = $requestBody | ConvertTo-Json -Compress -EscapeHandling EscapeNonAscii
+            $result = InvokeWebRequest $params
+            $nodes = ${result}?['data']?['nodes']
+            if (${nodes}?.Count -ne $nodeVariables.Count) {
+                if (${result}?['errors']) {
+                    $resultObject.Errors.AddRange($result['errors'])
+                }
+                $null = $resultObject.Errors.Add(@{
+                        message      = 'Querying deleted nodes: ' + $nodeVariables -join ','
+                        ResponseData = ${result}?['data']
+                    })
+            }
+            for ([int]$i = 0; $i -lt $nodeVariables.Count; $i++) {
+                if ($null -eq $nodes[$i]) {
+                    $resultObject.Issues[$i + $issueIndex].DeleteStatus = 'deleted'
+                }
+            }
+        }
+    }
+}
+catch {
+    $null = $resultObject.Errors.Add(@{message = "$_" })
+}
+
+$resultObject