diff --git a/ParallelKit.Harness.ps1 b/ParallelKit.Harness.ps1
index c1859d6..e4cc5a4 100644
--- a/ParallelKit.Harness.ps1
+++ b/ParallelKit.Harness.ps1
@@ -1813,6 +1813,87 @@ foreach ($s in $scenarios) {
 }
 Write-Host ""
 
+# ==============================================================================
+Write-Host "=== W: relative paths and the current location ===" -ForegroundColor Cyan
+# Programs start in the caller's current location, which cd/Set-Location
+# change but the process's working directory doesn't follow.
+Reset-Harness
+$here = Join-Path $env:TEMP ("pk-harness-wd-" + $PID)
+$null = New-Item -ItemType Directory -Force -Path (Join-Path $here 'sub')
+[System.IO.File]::WriteAllText((Join-Path $here 'pk-wd.cmd'), "@echo pk-wd ran in %CD%`r`n")
+$gone = Join-Path $env:TEMP ("pk-harness-wd-gone-" + $PID)
+$null = New-Item -ItemType Directory -Force -Path $gone
+function Get-HarnessCd {
+    # Where a program started by each entry point runs, via "cmd /c cd".
+    $wd = @{}
+    $wd.Batch = (Invoke-PkProcessBatch -Commands @(@{ FilePath = $cmdExe; Arguments = '/c cd' })).Results[0].Stdout.Trim()
+    $wd.WithTimeout = (Invoke-PkProcessWithTimeout -FilePath $cmdExe -Arguments '/c cd').Stdout.Trim()
+    $started = Start-PkProcess -FilePath $cmdExe -Arguments '/c cd'
+    $null = Wait-PkProcess -Process $started['Proc'] -TimeoutMs 10000
+    $wd.StartProcess = (Complete-PkProcess -Job $started -Dispose $true).Stdout.Trim()
+    $out = @{ Text = $null }
+    $feed = @{ Given = $false }
+    $null = Invoke-PkProcessDispatch -MaxConcurrent 1 `
+        -GroupProvider { if ($feed.Given) { return $null }; $feed.Given = $true; return 'g' }.GetNewClosure() `
+        -JobBuilder { param($g) return @(@{ FilePath = $cmdExe; Arguments = '/c cd' }) }.GetNewClosure() `
+        -JobFinalize { param($job, $pending) $out.Text = (Complete-PkProcess -Job $job).Stdout.Trim() }.GetNewClosure()
+    $wd.Dispatch = $out.Text
+    return $wd
+}
+Push-Location -LiteralPath $here
+# %TEMP% can be an 8.3 short path (C:\Users\RUNNER~1\... on GitHub's
+# runners); compare against the folder as PowerShell reports it.
+$here = (Get-Location).ProviderPath
+try {
+    Test-Assert ([Environment]::CurrentDirectory -ne $here) ("precondition: the process's working directory isn't the test folder (" + [Environment]::CurrentDirectory + ")")
+    $wd = Get-HarnessCd
+    $wrong = @($wd.Keys | Where-Object { $wd[$_] -ine $here })
+    Test-Assert ($wrong.Count -eq 0) ("every entry point starts programs in the current location by default (wrong: " + (@($wrong | ForEach-Object { $_ + '=' + $wd[$_] }) -join ', ') + ")")
+
+    $relText = $null
+    try { $relText = (Invoke-PkProcessWithTimeout -FilePath '.\pk-wd.cmd').Stdout.Trim() } catch { $relText = [string]$_ }
+    $missingText = ''
+    try { $null = Invoke-PkProcessWithTimeout -FilePath '.\no-such-tool.exe' } catch { $missingText = [string]$_ }
+    Test-Assert ($missingText -like ("*'.\no-such-tool.exe' (" + (Join-Path $here 'no-such-tool.exe') + ")*")) ("a program that can't be started is named with the full path that was tried (" + $missingText + ")")
+    $relBatch = (Invoke-PkProcessBatch -Commands @(@{ FilePath = '.\pk-wd.cmd' })).Results[0]
+    Test-Assert ($relText -ieq ("pk-wd ran in " + $here) -and $null -eq $relBatch.StartError -and $relBatch.Stdout.Trim() -ieq ("pk-wd ran in " + $here)) ("a FilePath with a folder in it (.\pk-wd.cmd) is found relative to the current location (" + $relText + ")")
+
+    $subText = $null
+    try { $subText = (Invoke-PkProcessWithTimeout -FilePath $cmdExe -Arguments '/c cd' -WorkingDirectory 'sub').Stdout.Trim() } catch { $subText = [string]$_ }
+    Test-Assert ($subText -ieq (Join-Path $here 'sub')) ("a relative WorkingDirectory is relative to the current location (" + $subText + ")")
+
+    $null = New-PSDrive -Name PkHarnessWd -PSProvider FileSystem -Root $here -Scope Script
+    try {
+        Push-Location -LiteralPath 'PkHarnessWd:\'
+        try { $onDrive = (Invoke-PkProcessWithTimeout -FilePath $cmdExe -Arguments '/c cd').Stdout.Trim() } finally { Pop-Location }
+        $driveText = $null
+        try { $driveText = (Invoke-PkProcessWithTimeout -FilePath 'PkHarnessWd:\pk-wd.cmd' -WorkingDirectory 'PkHarnessWd:\sub').Stdout.Trim() } catch { $driveText = [string]$_ }
+    } finally { Remove-PSDrive -Name PkHarnessWd -Scope Script }
+    Test-Assert ($onDrive -ieq $here) ("on a drive made with New-PSDrive, the program runs in the real folder behind it (" + $onDrive + ")")
+    Test-Assert ($driveText -ieq ("pk-wd ran in " + (Join-Path $here 'sub'))) ("a FilePath and WorkingDirectory on a New-PSDrive drive are translated to the real folders (" + $driveText + ")")
+    $homeText = $null
+    try { $homeText = (Invoke-PkProcessWithTimeout -FilePath $cmdExe -Arguments '/c cd' -WorkingDirectory '~').Stdout.Trim() } catch { $homeText = [string]$_ }
+    Test-Assert ($homeText -ieq (Resolve-Path -LiteralPath '~').ProviderPath) ("a WorkingDirectory of ~ is your home folder (" + $homeText + ")")
+
+    Push-Location -LiteralPath 'HKLM:\'
+    try { $fromReg = (Invoke-PkProcessWithTimeout -FilePath $cmdExe -Arguments '/c cd').Stdout.Trim() } finally { Pop-Location }
+    Test-Assert ($fromReg -ieq $here) ("from a registry location, the program runs in the last file-system location (" + $fromReg + ")")
+
+    Push-Location -LiteralPath $gone
+    try {
+        [System.IO.Directory]::Delete($gone, $true)   # Remove-Item refuses to delete the current location
+        $fromGone = Invoke-PkProcessWithTimeout -FilePath $cmdExe -Arguments '/c cd'
+        Test-Assert ($fromGone.ExitCode -eq 0 -and $fromGone.Stdout.Trim().TrimEnd('\') -ieq [Environment]::CurrentDirectory.TrimEnd('\')) ("if the current folder has been deleted, the program runs in the process's working directory instead (" + $fromGone.Stdout.Trim() + ")")
+    } finally { Pop-Location }
+
+    $explicit = Invoke-PkProcessWithTimeout -FilePath $cmdExe -Arguments '/c cd' -WorkingDirectory $env:SystemRoot
+    Test-Assert ($explicit.Stdout.Trim() -ieq $env:SystemRoot) "an explicit WorkingDirectory still wins over the current location"
+} finally {
+    Pop-Location
+    Remove-Item -LiteralPath $here, $gone -Recurse -Force -ErrorAction SilentlyContinue
+}
+Write-Host ""
+
 Set-PkMessageHandler -Handler $null
 Reset-PkAbortState
 
diff --git a/ParallelKit.ps1 b/ParallelKit.ps1
index c7365fd..b3ac6c6 100644
--- a/ParallelKit.ps1
+++ b/ParallelKit.ps1
@@ -756,6 +756,23 @@ function Resolve-PkEncoding {
     }
 }
 
+function Resolve-PkFileSystemPath {
+    # A path the way PowerShell reads it, turned into one Windows can use:
+    # relative to the current location, or on a drive like Data:\ or ~.
+    # Anything that isn't a file-system path to PowerShell (relative while
+    # the current location is HKLM:, say) is taken relative to $Here, the
+    # last file-system location.
+    param([string]$Path, [string]$Here)
+    if ([System.IO.Path]::IsPathRooted($Path)) { return $Path }
+    try {
+        $provider = $null
+        $drive = $null
+        $resolved = $ExecutionContext.SessionState.Path.GetUnresolvedProviderPathFromPSPath($Path, [ref]$provider, [ref]$drive)
+        if ($provider.Name -eq 'FileSystem') { return $resolved }
+    } catch { }   # not a path PowerShell can read (an unknown drive, say): the folder below is the best guess
+    return [System.IO.Path]::Combine($Here, $Path)
+}
+
 function Start-PkProcess {
     # .SYNOPSIS
     # Starts one program hidden, with its output captured in the background.
@@ -765,12 +782,16 @@ function Start-PkProcess {
     # Pass what this returns to Wait-PkProcess and Complete-PkProcess. Throws if the
     # program can't be started.
     # .PARAMETER FilePath
-    # The program to run.
+    # The program to run. A path with a folder in it is read as PowerShell reads
+    # paths: .\tool.exe and bin\tool.exe are relative to your current location, and
+    # drives like Data:\ or ~ work. A bare name (tool.exe) is found the way Windows
+    # finds programs, mostly on PATH.
     # .PARAMETER Arguments
     # Its command line as one string (see ConvertTo-PkArgumentString).
     # .PARAMETER WorkingDirectory
-    # Where to run it. Default: the PowerShell process's working directory, which
-    # isn't always your current location.
+    # Where to run it. Default: your current location. Read as PowerShell reads
+    # paths, so a relative path is relative to your current location, and drives
+    # like Data:\ or ~ work.
     # .PARAMETER OutputEncoding
     # How to decode its output: a name like 'utf-8', a code page number, or a
     # [System.Text.Encoding]. Default: the console's code page.
@@ -801,15 +822,36 @@ function Start-PkProcess {
     $psi.RedirectStandardOutput = $true
     $psi.RedirectStandardError  = $true
     $psi.CreateNoWindow         = $true
-    if ($WorkingDirectory) { $psi.WorkingDirectory = $WorkingDirectory }
+
+    # Relative paths mean your current location, as everywhere else in
+    # PowerShell, not the process's working directory (which cd and
+    # Set-Location never change). From a location that isn't on disk (HKLM:,
+    # say) that's the last file-system one. If that folder is gone, fall back
+    # to the process's working directory, as before.
+    $here = $ExecutionContext.SessionState.Path.CurrentFileSystemLocation.ProviderPath
+    if (-not [System.IO.Directory]::Exists($here)) { $here = $null }
 
     # In a try/catch on purpose: a bare .NET call that throws does not
     # reliably stop a PowerShell script, and a $null process left behind
-    # would be polled forever.
+    # would be polled forever. The path handling is in here too: it throws
+    # on a path with characters Windows doesn't allow.
     try {
+        if ($WorkingDirectory) {
+            if ($null -ne $here) { $WorkingDirectory = Resolve-PkFileSystemPath -Path $WorkingDirectory -Here $here }
+            $psi.WorkingDirectory = $WorkingDirectory
+        } elseif ($null -ne $here) {
+            $psi.WorkingDirectory = $here
+        }
+        # Only a path with a folder in it: a bare name is left to Windows'
+        # own search, which looks on PATH.
+        if ($null -ne $here -and ($FilePath.Contains('\') -or $FilePath.Contains('/'))) {
+            $psi.FileName = Resolve-PkFileSystemPath -Path $FilePath -Here $here
+        }
         $proc = [System.Diagnostics.Process]::Start($psi)
     } catch {
-        throw ("Start-PkProcess: could not start '" + $FilePath + "': " + $_)
+        $tried = ""
+        if ($psi.FileName -ne $FilePath) { $tried = " (" + $psi.FileName + ")" }
+        throw ("Start-PkProcess: could not start '" + $FilePath + "'" + $tried + ": " + $_)
     }
     $null = [PkChildProcessJob]::Assign($proc)
     return @{
@@ -965,7 +1007,7 @@ function Invoke-PkProcessWithTimeout {
     # .PARAMETER StreamTimeoutMs
     # How long to wait for the output after the program exits (default 15000).
     # .PARAMETER WorkingDirectory
-    # Where to run it, as for Start-PkProcess.
+    # Where to run it, as for Start-PkProcess. Default: your current location.
     # .PARAMETER OutputEncoding
     # How to decode its output, as for Start-PkProcess.
     # .PARAMETER IgnoreAbort
@@ -1685,7 +1727,7 @@ function Get-PkWorkerSafeFunctionNames {
     return @('Write-PkMessage', 'Test-PkAbortSignal', 'Test-PkCancelRequested', 'Initialize-PkThreadPool', 'Stop-PkProcessTree', 'Stop-PkJobProcesses', 'Resolve-PkEncoding',
              'Start-PkProcess', 'Wait-PkProcess', 'Complete-PkProcess', 'Invoke-PkProcessWithTimeout',
              'Invoke-PkProcessDispatch', 'Invoke-PkProcessDispatchCore', 'Invoke-PkProcessBatch',
-             'Register-PkCancellationSource', 'Unregister-PkCancellationSource', 'New-PkBatchResult', 'ConvertTo-PkArgumentString', 'Get-PkForceStopReason')
+             'Register-PkCancellationSource', 'Unregister-PkCancellationSource', 'New-PkBatchResult', 'ConvertTo-PkArgumentString', 'Get-PkForceStopReason', 'Resolve-PkFileSystemPath')
 }
 
 function Receive-PkCompletedHandles {
diff --git a/README.md b/README.md
index 5a90e1c..0726f97 100644
--- a/README.md
+++ b/README.md
@@ -125,6 +125,8 @@ Long parameter lists in these examples use splatting (`@batchParams`) instead of
 
 Each command is a hashtable with `FilePath`, `Arguments` and optionally `WorkingDirectory`, plus any keys of your own. `Arguments` is passed to the program as one string, exactly as written. `ConvertTo-PkArgumentString @(...)` builds that string from a list, quoting each argument so the program gets exactly that list back, spaces, quotes and trailing backslashes included. It follows the rules most Windows programs use; `cmd.exe /c` parses its own way. Programs run hidden, with their output captured.
 
+Programs run in your current location (`Get-Location`) unless a command says otherwise, and a relative `WorkingDirectory`, or a `FilePath` with a folder in it like `.\tools\cjxl.exe`, is relative to that location too. Drives PowerShell knows, like `~` or one made with `New-PSDrive`, work in both. A bare name like `cjxl.exe` is found the way Windows finds programs, mostly on `PATH`. A `.bat` or `.cmd` program can't run in a network-share (`\\server\share`) folder: `cmd.exe` falls back to `C:\Windows` there, so give such commands a local `WorkingDirectory`.
+
 `Invoke-PkProcessBatch` returns an object with `Results`, `Aborted` and `ForceKilledCount`. Each result is an object with `Command`, `ExitCode`, `Stdout`, `Stderr`, `StreamTimedOut`, `StreamError`, `StartError`, `Aborted` and `TimedOut`, every field always present, so `$batch.Results | Format-Table` reads well:
 
 - `Command` is your original command hashtable, so extra keys like `Source` above come back with it.