diff --git a/CHANGELOG.md b/CHANGELOG.md
index 0e1994b..78fa432 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -9,6 +9,23 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 
 ### Changed
 
+- [**#105**](https://github.com/psake/PowerShellBuild/issues/105)
+  **Breaking:** help generation moved from `platyPS` 0.14.x to
+  [`Microsoft.PowerShell.PlatyPS`](https://www.powershellgallery.com/packages/Microsoft.PowerShell.PlatyPS)
+  1.x. PlatyPS is also no longer a `RequiredModules` entry, so
+  `Install-Module PowerShellBuild` no longer installs it — the two PlatyPS
+  modules cannot be loaded into one process, so forcing the new one into every
+  session would break any consumer still holding the old one. Install it
+  yourself if you build help. `$PSBPreference.Docs.AlphabeticParamsOrder` is
+  removed, because PlatyPS 1.x always sorts parameters alphabetically and
+  offers no way back. Generated markdown carries the 1.x schema, though its
+  on-disk layout is unchanged. `Build-PSBuildUpdatableHelp` warns and returns
+  until the cabinet pipeline migrates in
+  [#152](https://github.com/psake/PowerShellBuild/issues/152); it could never
+  succeed in 0.8.x either, see
+  [#169](https://github.com/psake/PowerShellBuild/issues/169). See the
+  [v0.8 → v1.0 migration guide](docs/migration-v0.8-to-v1.0.md).
+
 - [**#144**](https://github.com/psake/PowerShellBuild/issues/144)
   **Breaking:** `Test-PSBuildScriptAnalysis` now counts PSScriptAnalyzer
   `ParseError` records alongside `Error`. A file that does not parse at all
diff --git a/PowerShellBuild/IB.tasks.ps1 b/PowerShellBuild/IB.tasks.ps1
index fe54942..fe50828 100644
--- a/PowerShellBuild/IB.tasks.ps1
+++ b/PowerShellBuild/IB.tasks.ps1
@@ -109,8 +109,8 @@ Task Pester -If (. $pesterPreReqs) Build, {
 
 $genMarkdownPreReqs = {
     $result = $true
-    if (-not (Get-Module platyPS -ListAvailable)) {
-        Write-Warning "platyPS module is not installed. Skipping [$($task.name)] task."
+    if (-not (Get-Module Microsoft.PowerShell.PlatyPS -ListAvailable)) {
+        Write-Warning "Microsoft.PowerShell.PlatyPS module is not installed. Skipping [$($task.name)] task."
         $result = $false
     }
     $result
@@ -124,7 +124,6 @@ Task GenerateMarkdown -if (. $genMarkdownPreReqs) StageFiles, {
         DocsPath              = $PSBPreference.Docs.RootDir
         Locale                = $PSBPreference.Help.DefaultLocale
         Overwrite             = $PSBPreference.Docs.Overwrite
-        AlphabeticParamsOrder = $PSBPreference.Docs.AlphabeticParamsOrder
         ExcludeDontShow       = $PSBPreference.Docs.ExcludeDontShow
         UseFullTypeName       = $PSBPreference.Docs.UseFullTypeName
     }
@@ -133,8 +132,8 @@ Task GenerateMarkdown -if (. $genMarkdownPreReqs) StageFiles, {
 
 $genHelpFilesPreReqs = {
     $result = $true
-    if (-not (Get-Module platyPS -ListAvailable)) {
-        Write-Warning "platyPS module is not installed. Skipping [$($task.name)] task."
+    if (-not (Get-Module Microsoft.PowerShell.PlatyPS -ListAvailable)) {
+        Write-Warning "Microsoft.PowerShell.PlatyPS module is not installed. Skipping [$($task.name)] task."
         $result = $false
     }
     $result
@@ -147,8 +146,8 @@ Task GenerateMAML -if (. $genHelpFilesPreReqs) GenerateMarkdown, {
 
 $genUpdatableHelpPreReqs = {
     $result = $true
-    if (-not (Get-Module platyPS -ListAvailable)) {
-        Write-Warning "platyPS module is not installed. Skipping [$($task.name)] task."
+    if (-not (Get-Module Microsoft.PowerShell.PlatyPS -ListAvailable)) {
+        Write-Warning "Microsoft.PowerShell.PlatyPS module is not installed. Skipping [$($task.name)] task."
         $result = $false
     }
     $result
diff --git a/PowerShellBuild/PowerShellBuild.psd1 b/PowerShellBuild/PowerShellBuild.psd1
index 16538fc..e87cd1b 100644
--- a/PowerShellBuild/PowerShellBuild.psd1
+++ b/PowerShellBuild/PowerShellBuild.psd1
@@ -11,7 +11,6 @@
     RequiredModules      = @(
         @{ModuleName = 'BuildHelpers'; ModuleVersion = '2.0.16' }
         @{ModuleName = 'Pester'; ModuleVersion = '5.6.1' }
-        @{ModuleName = 'platyPS'; ModuleVersion = '0.14.1' }
         @{ModuleName = 'psake'; ModuleVersion = '4.9.0' }
     )
     FunctionsToExport    = @(
diff --git a/PowerShellBuild/Public/Build-PSBuildMAMLHelp.ps1 b/PowerShellBuild/Public/Build-PSBuildMAMLHelp.ps1
index 20d42a6..79e754b 100644
--- a/PowerShellBuild/Public/Build-PSBuildMAMLHelp.ps1
+++ b/PowerShellBuild/Public/Build-PSBuildMAMLHelp.ps1
@@ -27,13 +27,49 @@ function Build-PSBuildMAMLHelp {
 
     # Generate the module's primary MAML help file
     foreach ($locale in $helpLocales) {
-        $externalHelpParams = @{
-            Path        = [IO.Path]::Combine($Path, $locale)
-            OutputPath  = [IO.Path]::Combine($DestinationPath, $locale)
-            Force       = $true
-            ErrorAction = 'SilentlyContinue'
-            Verbose     = $VerbosePreference
+        $localePath = [IO.Path]::Combine($Path, $locale)
+
+        # Only command documents can be exported. A module landing page imports without
+        # complaint but fails on export, and that failure aborts the whole batch and writes
+        # nothing, so it has to be filtered out rather than caught.
+        $commandMarkdownPath = @(
+            Measure-PlatyPSMarkdown -Path ([IO.Path]::Combine($localePath, '*.md')) |
+                Where-Object { $_.Filetype -match 'CommandHelp' } |
+                Select-Object -ExpandProperty 'FilePath'
+        )
+        if ($commandMarkdownPath.Count -eq 0) {
+            continue
+        }
+
+        # Export-MamlCommandHelp writes to <OutputFolder>/<ModuleName>/<external help file>,
+        # a level deeper than PowerShell looks and with the file name taken from the
+        # document's front matter. Export to a staging directory and move the results so the
+        # published layout stays <DestinationPath>/<locale>/<ModuleName>-help.xml, which is
+        # where every consumer's existing .ExternalHelp directive already points.
+        $stagingPath = [IO.Path]::Combine(
+            [IO.Path]::GetTempPath(),
+            [IO.Path]::GetRandomFileName()
+        )
+        try {
+            $mamlFile = @(
+                Import-MarkdownCommandHelp -Path $commandMarkdownPath |
+                    Export-MamlCommandHelp -OutputFolder $stagingPath -Force -Verbose:($VerbosePreference -eq 'Continue')
+            )
+
+            $localeDestinationPath = [IO.Path]::Combine($DestinationPath, $locale)
+            if (-not (Test-Path -LiteralPath $localeDestinationPath)) {
+                New-Item -Path $localeDestinationPath -ItemType Directory -Force > $null
+            }
+
+            foreach ($file in $mamlFile) {
+                # The file name is whatever the document's "external help file" front matter
+                # says, which Build-PSBuildMarkdown pins to the 0.14.x casing. Renaming here
+                # instead would leave the markdown and the MAML disagreeing about the name.
+                $destinationFilePath = Join-Path -Path $localeDestinationPath -ChildPath $file.Name
+                Move-Item -LiteralPath $file.FullName -Destination $destinationFilePath -Force
+            }
+        } finally {
+            Remove-Item -LiteralPath $stagingPath -Recurse -Force -ErrorAction SilentlyContinue
         }
-        New-ExternalHelp @externalHelpParams > $null
     }
 }
diff --git a/PowerShellBuild/Public/Build-PSBuildMarkdown.ps1 b/PowerShellBuild/Public/Build-PSBuildMarkdown.ps1
index 9010543..0f44807 100644
--- a/PowerShellBuild/Public/Build-PSBuildMarkdown.ps1
+++ b/PowerShellBuild/Public/Build-PSBuildMarkdown.ps1
@@ -4,6 +4,10 @@ function Build-PSBuildMarkdown {
         Creates PlatyPS markdown documents based on comment-based help of module.
     .DESCRIPTION
         Creates PlatyPS markdown documents based on comment-based help of module.
+
+        Existing command markdown is refreshed in place with Update-MarkdownCommandHelp so
+        hand-written prose survives, and markdown for commands that have no document yet is
+        generated with New-MarkdownCommandHelp.
     .PARAMETER ModulePath
         The path to the module
     .PARAMETER ModuleName
@@ -14,8 +18,6 @@ function Build-PSBuildMarkdown {
         The locale to save the markdown docs.
     .PARAMETER Overwrite
         Overwrite existing markdown files and use comment based help as the source of truth.
-    .PARAMETER AlphabeticParamsOrder
-        Order parameters alphabetically by name in PARAMETERS section. There are 5 exceptions: -Confirm, -WhatIf, -IncludeTotalCount, -Skip, and -First parameters will be the last.
     .PARAMETER ExcludeDontShow
         Exclude the parameters marked with `DontShow` in the parameter attribute from the help content.
     .PARAMETER UseFullTypeName
@@ -42,9 +44,6 @@ function Build-PSBuildMarkdown {
         [parameter(Mandatory)]
         [bool]$Overwrite,
 
-        [parameter(Mandatory)]
-        [bool]$AlphabeticParamsOrder,
-
         [parameter(Mandatory)]
         [bool]$ExcludeDontShow,
 
@@ -60,41 +59,83 @@ function Build-PSBuildMarkdown {
             return
         }
 
-        if (-not (Test-Path -LiteralPath $DocsPath)) {
-            New-Item -Path $DocsPath -ItemType Directory > $null
+        $localePath = [IO.Path]::Combine($DocsPath, $Locale)
+        if (-not (Test-Path -LiteralPath $localePath)) {
+            New-Item -Path $localePath -ItemType Directory -Force > $null
         }
 
-        if (Get-ChildItem -LiteralPath $DocsPath -Filter *.md -Recurse) {
-            $updateMDParams = @{
-                AlphabeticParamsOrder = $AlphabeticParamsOrder
-                ExcludeDontShow       = $ExcludeDontShow
-                UseFullTypeName       = $UseFullTypeName
-                Verbose               = $VerbosePreference
-            }
-            Get-ChildItem -LiteralPath $DocsPath -Directory | ForEach-Object {
-                Update-MarkdownHelp -Path $_.FullName @updateMDParams > $null
+        # Refresh first. Update-MarkdownCommandHelp merges the module's current surface into
+        # existing documents and preserves hand-written prose, where regenerating would
+        # discard it. -NoBackup keeps it from littering the docs tree with .md.bak files.
+        # Module landing pages are a different document type and are left alone.
+        $existingMarkdown = @(
+            Get-ChildItem -LiteralPath $localePath -Filter '*.md' -File -ErrorAction SilentlyContinue
+        )
+        if ($existingMarkdown.Count -gt 0) {
+            $existingCommandMarkdown = @(
+                $existingMarkdown.Where({
+                        (Measure-PlatyPSMarkdown -LiteralPath $_.FullName).Filetype -match 'CommandHelp'
+                    })
+            )
+            if ($existingCommandMarkdown.Count -gt 0) {
+                Update-MarkdownCommandHelp -LiteralPath $existingCommandMarkdown.FullName -NoBackup > $null
             }
         }
 
-        # ErrorAction set to SilentlyContinue so this command will not overwrite an existing MD file.
-        $newMDParams = @{
-            Module                = $ModuleName
-            Locale                = $Locale
-            OutputFolder          = [IO.Path]::Combine($DocsPath, $Locale)
-            AlphabeticParamsOrder = $AlphabeticParamsOrder
-            ExcludeDontShow       = $ExcludeDontShow
-            UseFullTypeName       = $UseFullTypeName
-            ErrorAction           = 'SilentlyContinue'
-            Verbose               = $VerbosePreference
-        }
-        if ($Overwrite) {
-            $newMDParams.Add('Force', $true)
-            $newMDParams.Remove('ErrorAction')
+        # New-MarkdownCommandHelp always writes to <OutputFolder>/<ModuleName>, and without
+        # -Force it skips existing files with a warning rather than an error. Generating into
+        # an empty staging directory and moving the results keeps the documented
+        # <DocsPath>/<Locale> layout and keeps Overwrite meaning what it did before.
+        $stagingPath = [IO.Path]::Combine(
+            [IO.Path]::GetTempPath(),
+            [IO.Path]::GetRandomFileName()
+        )
+        try {
+            $newMarkdownParams = @{
+                ModuleInfo   = $moduleInfo
+                OutputFolder = $stagingPath
+                Locale       = $Locale
+                # PlatyPS 1.x defaults this front matter key to "<Module>-Help.xml", where
+                # 0.14.x wrote "<Module>-help.xml". The key is what Export-MamlCommandHelp
+                # names the MAML file after, so pinning it here keeps the markdown, the MAML
+                # file name, and any existing .ExternalHelp directive in agreement -- and
+                # keeps help resolving on case-sensitive file systems. Renaming after export
+                # would fix the file name while leaving the front matter disagreeing with it.
+                Metadata     = @{ 'external help file' = "$ModuleName-help.xml" }
+                # Compared explicitly rather than passing $VerbosePreference through. The
+                # preference is an ActionPreference, and converting it to a switch uses the
+                # underlying number, so Stop and Inquire turn verbose output on even though
+                # neither asked for it.
+                Verbose      = ($VerbosePreference -eq 'Continue')
+            }
+            if ($ExcludeDontShow) {
+                $newMarkdownParams.ExcludeDontShow = $true
+            }
+            # The sense of this option inverted in PlatyPS 1.x: full type names are now the
+            # default and abbreviation is the switch, so the old setting maps to its absence.
+            if (-not $UseFullTypeName) {
+                $newMarkdownParams.AbbreviateParameterTypeName = $true
+            }
+            New-MarkdownCommandHelp @newMarkdownParams > $null
+
+            $generatedPath = [IO.Path]::Combine($stagingPath, $ModuleName)
+            $generatedMarkdown = @(
+                Get-ChildItem -LiteralPath $generatedPath -Filter '*.md' -File -ErrorAction SilentlyContinue
+            )
+            foreach ($markdownFile in $generatedMarkdown) {
+                $destinationPath = Join-Path -Path $localePath -ChildPath $markdownFile.Name
+                if ((Test-Path -LiteralPath $destinationPath) -and -not $Overwrite) {
+                    # Already refreshed above; regenerating would discard hand-written prose.
+                    continue
+                }
+                Move-Item -LiteralPath $markdownFile.FullName -Destination $destinationPath -Force
+            }
+        } finally {
+            Remove-Item -LiteralPath $stagingPath -Recurse -Force -ErrorAction SilentlyContinue
         }
-        New-MarkdownHelp @newMDParams > $null
     } catch {
         Write-Error ($LocalizedData.FailedToGenerateMarkdownHelp -f $_)
     } finally {
-        Remove-Module $moduleName
+        Remove-Module $ModuleName
     }
 }
diff --git a/PowerShellBuild/Public/Build-PSBuildUpdatableHelp.ps1 b/PowerShellBuild/Public/Build-PSBuildUpdatableHelp.ps1
index de784eb..986a22e 100644
--- a/PowerShellBuild/Public/Build-PSBuildUpdatableHelp.ps1
+++ b/PowerShellBuild/Public/Build-PSBuildUpdatableHelp.ps1
@@ -4,6 +4,11 @@ function Build-PSBuildUpdatableHelp {
         Create updatable help .cab file based on PlatyPS markdown help.
     .DESCRIPTION
         Create updatable help .cab file based on PlatyPS markdown help.
+
+        Not implemented against PlatyPS 1.x yet. The cabinet pipeline is migrated in
+        psake/PowerShellBuild#152 along with the three defects in #169 that prevented this
+        function from ever succeeding. Until then it reports that updatable help was skipped
+        and returns without writing anything.
     .PARAMETER DocsPath
         Path to PlatyPS markdown help files.
     .PARAMETER OutputPath
@@ -14,8 +19,11 @@ function Build-PSBuildUpdatableHelp {
     .EXAMPLE
         PS> Build-PSBuildUpdatableHelp -DocsPath ./docs -OutputPath ./Output/UpdatableHelp
 
-        Create help .cab file based on PlatyPS markdown help.
+        Reports that updatable help is not available and returns.
     #>
+    # The parameters are unused only because the body is stubbed. They stay so the public
+    # signature does not change twice -- once here and again when #152 restores the body.
+    [Diagnostics.CodeAnalysis.SuppressMessageAttribute('PSReviewUnusedParameter', '')]
     [CmdletBinding()]
     param(
         [parameter(Mandatory)]
@@ -27,44 +35,11 @@ function Build-PSBuildUpdatableHelp {
         [string]$Module = $ModuleName
     )
 
-    if ($null -ne $IsWindows -and -not $IsWindows) {
-        Write-Warning $LocalizedData.MakeCabNotAvailable
-        return
-    }
-
-    $helpLocales = (Get-ChildItem -Path $DocsPath -Directory).Name
-
-    # Create updatable help output directory
-    if (-not (Test-Path -LiteralPath $OutputPath)) {
-        $newItemSplat = @{
-            ItemType = 'Directory'
-            Verbose  = $VerbosePreference
-            Path     = $OutputPath
-        }
-        New-Item @newItemSplat > $null
-    } else {
-        Write-Verbose ($LocalizedData.DirectoryAlreadyExists -f $OutputPath)
-        $removeItemSplat = @{
-            Recurse = $true
-            Force   = $true
-            Verbose = $VerbosePreference
-        }
-        Get-ChildItem $OutputPath | Remove-Item @removeItemSplat
-    }
-
-    # Generate updatable help files. Note: this will currently update the
-    # version number in the module's MD file in the metadata.
-    foreach ($locale in $helpLocales) {
-        $cabParams = @{
-            CabFilesFolder  = [IO.Path]::Combine($moduleOutDir, $locale)
-            LandingPagePath = [IO.Path]::Combine(
-                $DocsPath,
-                $locale,
-                "$Module.md"
-            )
-            OutputFolder    = $OutputPath
-            Verbose         = $VerbosePreference
-        }
-        New-ExternalHelpCab @cabParams > $null
-    }
+    # Deliberately references no PlatyPS command. Naming New-ExternalHelpCab here is enough to
+    # make PowerShell autoload platyPS 0.14.2 on any session that resolves it, and once that
+    # module is loaded, Microsoft.PowerShell.PlatyPS can no longer be imported in the same
+    # process -- both ship their own YamlDotNet with different assembly identities. Leaving the
+    # old call in place would poison every session that still has 0.14.2 installed, which is
+    # every consumer part-way through the upgrade.
+    Write-Warning $LocalizedData.UpdatableHelpNotMigrated
 }
diff --git a/PowerShellBuild/build.properties.ps1 b/PowerShellBuild/build.properties.ps1
index 541cda9..2e8d24c 100644
--- a/PowerShellBuild/build.properties.ps1
+++ b/PowerShellBuild/build.properties.ps1
@@ -126,16 +126,13 @@ $moduleVersion = (Import-PowerShellDataFile -Path $env:BHPSModuleManifest).Modul
         # Whether to overwrite existing markdown files and use comment based help as the source of truth
         Overwrite             = $false
 
-        # Whether to order parameters alphabetically by name in PARAMETERS section.
-        # Value passed to New-MarkdownHelp and Update-MarkdownHelp.
-        AlphabeticParamsOrder = $false
-
         # Exclude the parameters marked with `DontShow` in the parameter attribute from the help content.
-        # Value passed to New-MarkdownHelp and Update-MarkdownHelp.
+        # Value passed to New-MarkdownCommandHelp.
         ExcludeDontShow       = $false
 
         # Indicates that the target document will use a full type name instead of a short name for parameters.
-        # Value passed to New-MarkdownHelp and Update-MarkdownHelp.
+        # PlatyPS 1.x writes full type names by default, so $false is passed through as
+        # New-MarkdownCommandHelp's -AbbreviateParameterTypeName switch.
         UseFullTypeName       = $false
     }
     Publish = @{
diff --git a/PowerShellBuild/en-US/Messages.psd1 b/PowerShellBuild/en-US/Messages.psd1
index 9149e18..fae187d 100644
--- a/PowerShellBuild/en-US/Messages.psd1
+++ b/PowerShellBuild/en-US/Messages.psd1
@@ -3,6 +3,7 @@ NoCommandsExported=No commands have been exported. Skipping markdown generation.
 FailedToGenerateMarkdownHelp=Failed to generate markdown help. : {0}
 AddingFileToPsm1=Adding [{0}] to PSM1
 MakeCabNotAvailable=MakeCab.exe is not available. Cannot create help cab.
+UpdatableHelpNotMigrated=Updatable help was skipped. The cabinet pipeline has not been migrated to Microsoft.PowerShell.PlatyPS 1.x yet; see psake/PowerShellBuild#152.
 DirectoryAlreadyExists=Directory already exists [{0}].
 PathLongerThan3Chars=Path [{0}] must be longer than 3 characters.
 BuildSystemDetails=Build System Details:
diff --git a/PowerShellBuild/psakeFile.ps1 b/PowerShellBuild/psakeFile.ps1
index cff79f9..2208e18 100644
--- a/PowerShellBuild/psakeFile.ps1
+++ b/PowerShellBuild/psakeFile.ps1
@@ -174,8 +174,8 @@ Task BuildHelp -Depends $PSBBuildHelpDependency {} -Description 'Builds help doc
 
 $genMarkdownPreReqs = {
     $result = $true
-    if (-not (Get-Module platyPS -ListAvailable)) {
-        Write-Warning "platyPS module is not installed. Skipping [$($psake.context.currentTaskName)] task."
+    if (-not (Get-Module Microsoft.PowerShell.PlatyPS -ListAvailable)) {
+        Write-Warning "Microsoft.PowerShell.PlatyPS module is not installed. Skipping [$($psake.context.currentTaskName)] task."
         $result = $false
     }
     $result
@@ -187,7 +187,6 @@ Task GenerateMarkdown -Depends $PSBGenerateMarkdownDependency -PreCondition $gen
         DocsPath              = $PSBPreference.Docs.RootDir
         Locale                = $PSBPreference.Help.DefaultLocale
         Overwrite             = $PSBPreference.Docs.Overwrite
-        AlphabeticParamsOrder = $PSBPreference.Docs.AlphabeticParamsOrder
         ExcludeDontShow       = $PSBPreference.Docs.ExcludeDontShow
         UseFullTypeName       = $PSBPreference.Docs.UseFullTypeName
         Verbose               = $VerbosePreference -eq 'Continue'
@@ -197,8 +196,8 @@ Task GenerateMarkdown -Depends $PSBGenerateMarkdownDependency -PreCondition $gen
 
 $genHelpFilesPreReqs = {
     $result = $true
-    if (-not (Get-Module platyPS -ListAvailable)) {
-        Write-Warning "platyPS module is not installed. Skipping [$($psake.context.currentTaskName)] task."
+    if (-not (Get-Module Microsoft.PowerShell.PlatyPS -ListAvailable)) {
+        Write-Warning "Microsoft.PowerShell.PlatyPS module is not installed. Skipping [$($psake.context.currentTaskName)] task."
         $result = $false
     }
     $result
@@ -209,8 +208,8 @@ Task GenerateMAML -Depends $PSBGenerateMAMLDependency -PreCondition $genHelpFile
 
 $genUpdatableHelpPreReqs = {
     $result = $true
-    if (-not (Get-Module platyPS -ListAvailable)) {
-        Write-Warning "platyPS module is not installed. Skipping [$($psake.context.currentTaskName)] task."
+    if (-not (Get-Module Microsoft.PowerShell.PlatyPS -ListAvailable)) {
+        Write-Warning "Microsoft.PowerShell.PlatyPS module is not installed. Skipping [$($psake.context.currentTaskName)] task."
         $result = $false
     }
     $result
diff --git a/docs/migration-v0.8-to-v1.0.md b/docs/migration-v0.8-to-v1.0.md
index 6268436..ee05ac1 100644
--- a/docs/migration-v0.8-to-v1.0.md
+++ b/docs/migration-v0.8-to-v1.0.md
@@ -28,9 +28,16 @@ One line per break; follow the link for details and migration steps.
 - [Unparsable files now fail the script analysis gate](#unparsable-files-now-fail-the-script-analysis-gate)
   — `ParseError` findings are counted with `Error`, so a file that does not
   parse fails every threshold except `None`.
+- [Help generation now uses Microsoft.PowerShell.PlatyPS 1.x, and installs it yourself](#help-generation-now-uses-microsoftpowershellplatyps-1x-and-installs-it-yourself)
+  — the PlatyPS dependency changed module, and is no longer installed for you.
+- [`$PSBPreference.Docs.AlphabeticParamsOrder` is removed](#psbpreferencedocsalphabeticparamsorder-is-removed)
+  — PlatyPS 1.x always sorts alphabetically, so the setting could no longer do anything.
+- [Generated markdown uses the PlatyPS 1.x schema](#generated-markdown-uses-the-platyps-1x-schema)
+  — expect a large diff in `docs/` on the first 1.0.0 build.
+- [Updatable help is temporarily unavailable](#updatable-help-is-temporarily-unavailable)
+  — the cabinet pipeline is migrated before 1.0.0 ships.
 
-> More entries will follow as the Phase 2 migrations to
-> Microsoft.PowerShell.PlatyPS 1.x and psake 5.x land.
+> More entries will follow as the remaining Phase 2 work lands.
 
 ## AI-assisted migration
 
@@ -200,6 +207,125 @@ This is additive — existing values behave as before.
 Tracked in issue
 [#144](https://github.com/psake/PowerShellBuild/issues/144).
 
+### Help generation now uses Microsoft.PowerShell.PlatyPS 1.x, and installs it yourself
+
+`Build-PSBuildMarkdown` and `Build-PSBuildMAMLHelp` are built on
+[`Microsoft.PowerShell.PlatyPS`](https://www.powershellgallery.com/packages/Microsoft.PowerShell.PlatyPS)
+1.x instead of `platyPS` 0.14.x. The `GenerateMarkdown` and `GenerateMAML`
+tasks now check for the new module and skip with a warning if it is
+missing, exactly as they did for the old one.
+
+PlatyPS is **no longer listed in `RequiredModules`**, so
+`Install-Module PowerShellBuild` no longer installs it for you. This is
+deliberate rather than an oversight. The two PlatyPS modules each ship
+their own `YamlDotNet.dll` with different assembly identities, and .NET
+refuses to load both into one process — whichever imports second fails
+with `Assembly with same name is already loaded`. A `RequiredModules`
+entry forces that load into **every** session that imports
+PowerShellBuild, including builds that never generate documentation, so
+any consumer still holding `platyPS` 0.14.x — which is every consumer
+part-way through this upgrade — would be unable to import PowerShellBuild
+at all. Making the dependency optional matches how the docs tasks have
+always behaved: they probe for the module and skip when it is absent.
+
+**Before (0.8.x):**
+
+```powershell
+# platyPS arrived with PowerShellBuild via RequiredModules
+Install-Module -Name PowerShellBuild
+```
+
+**After (1.0.0):**
+
+```powershell
+Install-Module -Name PowerShellBuild
+# Only if you build help; add it to your own requirements/bootstrap
+Install-Module -Name Microsoft.PowerShell.PlatyPS -MinimumVersion 1.0.3
+```
+
+**Detection:** the build prints
+`Microsoft.PowerShell.PlatyPS module is not installed. Skipping [GenerateMarkdown] task.`
+and produces no markdown or MAML.
+
+You can uninstall `platyPS` 0.14.x once nothing else on the machine needs
+it. Leaving it installed is safe — it is only a problem if something
+loads it into the same session that loads PlatyPS 1.x.
+
+Tracked in PRs [#150](https://github.com/psake/PowerShellBuild/issues/150)
+and [#151](https://github.com/psake/PowerShellBuild/issues/151); chain
+context in [#105](https://github.com/psake/PowerShellBuild/issues/105).
+
+### `$PSBPreference.Docs.AlphabeticParamsOrder` is removed
+
+PlatyPS 1.x always orders parameters alphabetically and offers no option
+to restore declaration order, so the setting could no longer do anything.
+Rather than keep a setting that silently lies, it is gone, along with the
+`AlphabeticParamsOrder` parameter on `Build-PSBuildMarkdown`.
+
+**Before (0.8.x):**
+
+```powershell
+$PSBPreference.Docs.AlphabeticParamsOrder = $true
+```
+
+**After (1.0.0):**
+
+```powershell
+# Remove the line. Alphabetical ordering is now the only behavior.
+```
+
+**Detection:** setting the property no longer fails (it is a plain
+hashtable), so this will not error — grep your build file for
+`AlphabeticParamsOrder` and delete the assignment. Calling
+`Build-PSBuildMarkdown` with `-AlphabeticParamsOrder` **does** fail, with
+`A parameter cannot be found that matches parameter name 'AlphabeticParamsOrder'`.
+
+`ExcludeDontShow` and `UseFullTypeName` are unchanged and keep their
+existing behavior.
+
+### Generated markdown uses the PlatyPS 1.x schema
+
+Markdown written into `$PSBPreference.Docs.RootDir` now carries
+`PlatyPS schema version: 2024-05-01` and a `document type:` key where
+0.14.x wrote `schema: 2.0.0`. Command documents also gain an `## ALIASES`
+section and per-parameter-set `### __AllParameterSets` headings inside
+`SYNTAX`.
+
+The on-disk layout is unchanged: documents stay at
+`<Docs.RootDir>/<locale>/<Command>.md`, and MAML still lands at
+`<ModuleOutDir>/<locale>/<ModuleName>-help.xml`. PlatyPS 1.x would
+otherwise nest both a level deeper under a `<ModuleName>` directory;
+PowerShellBuild flattens that back out so existing docs trees, static
+site configuration, and `.ExternalHelp` directives keep working.
+
+**Detection:** your first 1.0.0 build produces a large diff in `docs/`.
+
+If you **commit** your `docs/` tree, review that diff for lost prose
+before committing it. Existing documents are refreshed in place with
+`Update-MarkdownCommandHelp`, which preserves hand-written content, so
+this should be schema churn rather than content loss — but verify.
+Consumer guidance for converting a committed tree is
+[#154](https://github.com/psake/PowerShellBuild/issues/154).
+
+### Updatable help is temporarily unavailable
+
+`Build-PSBuildUpdatableHelp` and the `GenerateUpdatableHelp` task write a
+warning and return without producing a cabinet. The 1.x cabinet pipeline
+is migrated in [#152](https://github.com/psake/PowerShellBuild/issues/152)
+before 1.0.0 ships.
+
+This costs nothing in practice: the function could never succeed in
+0.8.x either. It required a module landing page that
+`Build-PSBuildMarkdown` never generated, and it passed an undefined
+variable as the cabinet source folder — three separate defects, recorded
+in [#169](https://github.com/psake/PowerShellBuild/issues/169). The task
+is opt-in and is not part of the default build, so most consumers never
+reached it.
+
+**Detection:** `Updatable help was skipped. The cabinet pipeline has not
+been migrated to Microsoft.PowerShell.PlatyPS 1.x yet` in the build
+output, where 0.8.x raised a parameter-binding error.
+
 ## Adding an entry (for PR contributors)
 
 Every breaking-change PR that lands in v1.0.0 must add an entry here for
diff --git a/instructions/repository-specific.instructions.md b/instructions/repository-specific.instructions.md
index c10d30f..ad048f7 100644
--- a/instructions/repository-specific.instructions.md
+++ b/instructions/repository-specific.instructions.md
@@ -232,7 +232,7 @@ versions — and installed via **PSDepend** when `./build.ps1 -Bootstrap` runs:
 | psake            | Task runner for this repo's own build                      |
 | PSScriptAnalyzer | Static analysis of the built module                        |
 | InvokeBuild      | Alternate task runner (consumer-facing `IB.tasks.ps1`)     |
-| platyPS          | Help and documentation generation                          |
+| Microsoft.PowerShell.PlatyPS | Help and documentation generation (optional; not a required module) |
 
 ## Testing
 
diff --git a/requirements.psd1 b/requirements.psd1
index 3f920f5..bc837ae 100755
--- a/requirements.psd1
+++ b/requirements.psd1
@@ -12,5 +12,8 @@
     psake            = '5.0.4'
     PSScriptAnalyzer = '1.25.0'
     InvokeBuild      = '5.14.23'
-    platyPS          = '0.14.2'
+    PlatyPS          = @{
+        Name    = 'Microsoft.PowerShell.PlatyPS'
+        Version = '1.0.3'
+    }
 }
diff --git a/tests/Build-PSBuildHelp.tests.ps1 b/tests/Build-PSBuildHelp.tests.ps1
index e10236c..1d38a2b 100644
--- a/tests/Build-PSBuildHelp.tests.ps1
+++ b/tests/Build-PSBuildHelp.tests.ps1
@@ -21,8 +21,8 @@
 
 BeforeDiscovery {
     # The psake PreConditions on the docs tasks gate on exactly this, so the tests behave the
-    # same way the shipped tasks do: absent platyPS means skipped, not failed.
-    $script:platyPSAvailable = [bool](Get-Module -Name 'platyPS' -ListAvailable)
+    # same way the shipped tasks do: an absent module means skipped, not failed.
+    $script:platyPSAvailable = [bool](Get-Module -Name 'Microsoft.PowerShell.PlatyPS' -ListAvailable)
 
     # Build-PSBuildUpdatableHelp returns early on non-Windows, and Windows PowerShell 5.1 has
     # no $IsWindows at all, so it takes the Windows path there. Resolved at discovery because
@@ -85,12 +85,23 @@ Describe 'Help building functions' -Skip:(-not $script:platyPSAvailable) {
                 Should -Not -Exist
         }
 
-        It 'produces markdown carrying the 0.14.x schema marker' {
-            # The 0.14.x front matter carries "external help file" and "schema: 2.0.0". The 1.x
-            # schema drops the latter, so this assertion is the tripwire that says the
-            # migration in #150 actually changed the output format.
+        It 'produces markdown carrying the 1.x schema marker' {
+            # 0.14.x front matter carried "schema: 2.0.0". 1.x replaces it with a dated schema
+            # version and a document type, so this pins the migration rather than just passing
+            # either way.
             $markdownPath = Join-Path -Path $script:markdownScenario.LocalePath -ChildPath 'Get-Widget.md'
-            Get-Content -Path $markdownPath -Raw | Should -Match 'schema:\s*2\.0\.0'
+            $markdown = Get-Content -Path $markdownPath -Raw
+            $markdown | Should -Match 'PlatyPS schema version:'
+            $markdown | Should -Match 'document type:\s*cmdlet'
+            $markdown | Should -Not -Match 'schema:\s*2\.0\.0'
+        }
+
+        It 'keeps the markdown directly under the locale directory' {
+            # New-MarkdownCommandHelp writes to <OutputFolder>/<ModuleName>. The function
+            # flattens that back out, so a nested module directory here means the flattening
+            # regressed and every downstream path assumption breaks with it.
+            Join-Path -Path $script:markdownScenario.LocalePath -ChildPath $script:markdownScenario.ModuleName |
+                Should -Not -Exist
         }
     }
 
@@ -136,23 +147,6 @@ Describe 'Help building functions' -Skip:(-not $script:platyPSAvailable) {
 
         BeforeAll {
             $script:cabScenario = New-PSBuildDocsScenario -Path $TestDrive -Name 'cab'
-            $cabMarkdownJobParameter = @{
-                ModulePath  = $script:builtModulePath
-                CommandName = 'Build-PSBuildMarkdown'
-                Parameter   = New-PSBuildMarkdownParameter -Scenario $script:cabScenario
-            }
-            $null = Invoke-PSBuildCommandInJob @cabMarkdownJobParameter
-
-            $cabMamlJobParameter = @{
-                ModulePath  = $script:builtModulePath
-                CommandName = 'Build-PSBuildMAMLHelp'
-                Parameter   = @{
-                    Path            = $script:cabScenario.DocsPath
-                    DestinationPath = $script:cabScenario.OutputPath
-                }
-            }
-            $null = Invoke-PSBuildCommandInJob @cabMamlJobParameter
-
             $cabJobParameter = @{
                 ModulePath  = $script:builtModulePath
                 CommandName = 'Build-PSBuildUpdatableHelp'
@@ -165,42 +159,18 @@ Describe 'Help building functions' -Skip:(-not $script:platyPSAvailable) {
             $script:cabResult = Invoke-PSBuildCommandInJob @cabJobParameter
         }
 
-        It 'declines to run on platforms without makecab' -Skip:$script:onWindows {
+        # Pins the documented intermediate state, not the destination. The cabinet pipeline
+        # migrates in #152 together with the three defects in #169 that stopped this function
+        # ever succeeding. Until then it must fail quietly rather than throw, and above all it
+        # must not name a platyPS 0.14.2 command: resolving one autoloads that module, and a
+        # session holding it can no longer import Microsoft.PowerShell.PlatyPS at all.
+        It 'returns without throwing' {
             $script:cabResult.Threw | Should -BeFalse
-            $script:cabScenario.UpdatableHelpPath | Should -Not -Exist
-        }
-
-        It 'creates the output directory' -Skip:(-not $script:onWindows) {
-            # This much works today: the directory is created before the cab step throws.
-            $script:cabScenario.UpdatableHelpPath | Should -Exist
+            $script:cabResult.ErrorMessage | Should -BeNullOrEmpty
         }
 
-        It 'fails parameter binding on the cab step' -Skip:(-not $script:onWindows) {
-            # Pins the CURRENT broken behavior so the baseline is honest about what happens,
-            # and so fixing psake/PowerShellBuild#169 forces this test to be revisited rather
-            # than leaving a silent pass. Delete this test when #169 is fixed; the two below
-            # replace it.
-            #
-            # Either of two independent defects can surface first, depending on the order
-            # PowerShell binds the splatted parameters: LandingPagePath points at a module page
-            # that is never generated, and CabFilesFolder is built from the undefined
-            # $moduleOutDir, which collapses to the bare locale name. Asserting on one of them
-            # specifically makes this test flaky, so it accepts either.
-            $script:cabResult.Threw | Should -BeTrue
-            $script:cabResult.ErrorMessage | Should -Match 'LandingPagePath|CabFilesFolder'
-        }
-
-        It 'produces a cabinet file' -Skip {
-            # Skipped pending psake/PowerShellBuild#169. This is the acceptance criterion for
-            # that fix and for the #152 migration, written now so it is not written twice.
-            Get-ChildItem -Path $script:cabScenario.UpdatableHelpPath -Filter '*.cab' |
-                Should -Not -BeNullOrEmpty
-        }
-
-        It 'produces the help info manifest' -Skip {
-            # Skipped pending psake/PowerShellBuild#169. See above.
-            Get-ChildItem -Path $script:cabScenario.UpdatableHelpPath -Filter '*HelpInfo.xml' |
-                Should -Not -BeNullOrEmpty
+        It 'writes nothing' {
+            $script:cabScenario.UpdatableHelpPath | Should -Not -Exist
         }
     }
 }
diff --git a/tests/fixtures/FixtureHelpers.psm1 b/tests/fixtures/FixtureHelpers.psm1
index 744a2ee..5e7bc7b 100644
--- a/tests/fixtures/FixtureHelpers.psm1
+++ b/tests/fixtures/FixtureHelpers.psm1
@@ -115,17 +115,14 @@ function New-PSBuildMarkdownParameter {
     .SYNOPSIS
         Build the Build-PSBuildMarkdown parameter set for a docs scenario.
     .DESCRIPTION
-        Build-PSBuildMarkdown takes four mandatory [bool] parameters that most tests do not care
-        about but cannot omit. This supplies them at their build.properties.ps1 defaults so a
+        Build-PSBuildMarkdown takes three mandatory [bool] parameters that most tests do not
+        care about but cannot omit. This supplies them at their build.properties.ps1 defaults so a
         test only has to name the ones it is actually exercising.
     .PARAMETER Scenario
         Scenario object from New-PSBuildDocsScenario.
     .PARAMETER Overwrite
         Whether comment-based help overwrites existing markdown. Defaults to $false, matching
         $PSBPreference.Docs.Overwrite.
-    .PARAMETER AlphabeticParamsOrder
-        Whether parameters are ordered alphabetically. Defaults to $false, matching
-        $PSBPreference.Docs.AlphabeticParamsOrder.
     .PARAMETER ExcludeDontShow
         Whether parameters marked DontShow are excluded. Defaults to $false, matching
         $PSBPreference.Docs.ExcludeDontShow.
@@ -153,9 +150,6 @@ function New-PSBuildMarkdownParameter {
         [bool]
         $Overwrite = $false,
 
-        [bool]
-        $AlphabeticParamsOrder = $false,
-
         [bool]
         $ExcludeDontShow = $false,
 
@@ -169,7 +163,6 @@ function New-PSBuildMarkdownParameter {
         DocsPath              = $Scenario.DocsPath
         Locale                = $Scenario.Locale
         Overwrite             = $Overwrite
-        AlphabeticParamsOrder = $AlphabeticParamsOrder
         ExcludeDontShow       = $ExcludeDontShow
         UseFullTypeName       = $UseFullTypeName
     }