Fix macOS/Linux blocking: replace Console.ReadLine with polling PSConsoleHostReadLine

On macOS/Linux without PSReadLine, the built-in PSConsoleHostReadLine calls
Console.ReadLine() which blocks the main runspace, preventing the MCP timer
action block from firing until the user presses Enter in Terminal.app.

Fix: define a custom global:PSConsoleHostReadLine in the psm1 that polls
Console.KeyAvailable + Start-Sleep 50ms in a loop. PowerShell processes
the event queue between pipeline statements, so the MCP timer action block
(Register-ObjectEvent) fires during each Sleep without requiring user input.

CI: add two new test steps to cross-platform-test.yml:
- PSConsoleHostReadLine is defined on non-Windows after module import
- Timer event fires during Start-Sleep polling (core mechanism validation)
Also remove the macOS invoke_expression skip from Named Pipe test.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: yotsuda

.github/workflows/cross-platform-test.yml

@@ -177,8 +177,54 @@ jobs:
           }
         }
 
+        Write-Host "`n=== PSConsoleHostReadLine fix (non-Windows) ===" -ForegroundColor Cyan
+        if (-not $IsWindows) {
+          # PSReadLine defines PSConsoleHostReadLine when loaded.
+          # After Remove-Module PSReadLine, our psm1 defines a custom polling version.
+          $fn = Get-Command PSConsoleHostReadLine -ErrorAction SilentlyContinue
+          if (-not $fn) {
+            throw "PSConsoleHostReadLine not defined - fix not applied"
+          }
+          Write-Host "PSConsoleHostReadLine: DEFINED (custom polling implementation)" -ForegroundColor Green
+          Write-Host "  CommandType : $($fn.CommandType)"
+          Write-Host "  Definition  : $($fn.Definition.Substring(0, [Math]::Min(80, $fn.Definition.Length)))..."
+        }
+
         Write-Host "`n=== All tests passed ===" -ForegroundColor Green
 
+    - name: Test timer event polling mechanism (non-Windows)
+      if: runner.os != 'Windows'
+      shell: pwsh
+      run: |
+        $ErrorActionPreference = "Stop"
+        Import-Module PowerShell.MCP
+
+        # Verify that Register-ObjectEvent action blocks fire during Start-Sleep polling.
+        # This is the core mechanism of the PSConsoleHostReadLine fix:
+        # the custom ReadLine polls Console.KeyAvailable + Start-Sleep 50ms in a loop,
+        # and Start-Sleep must yield the runspace long enough for the timer action to run.
+        Write-Host "=== Timer event fires during Start-Sleep polling ===" -ForegroundColor Cyan
+
+        $global:timerFired = $false
+        $timer = New-Object System.Timers.Timer 150
+        $timer.AutoReset = $false
+        Register-ObjectEvent -InputObject $timer -EventName Elapsed -Action {
+          $global:timerFired = $true
+        } | Out-Null
+        $timer.Start()
+
+        # Simulate PSConsoleHostReadLine's inner loop: poll every 50ms for up to 2s
+        $deadline = [DateTime]::UtcNow.AddMilliseconds(2000)
+        while (-not $global:timerFired -and [DateTime]::UtcNow -lt $deadline) {
+          Start-Sleep -Milliseconds 50
+        }
+
+        if (-not $global:timerFired) {
+          throw "FAIL: Timer event did NOT fire during Start-Sleep polling. The PSConsoleHostReadLine fix will not work on this platform."
+        }
+        Write-Host "PASS: Timer event fired during Start-Sleep polling." -ForegroundColor Green
+        Write-Host "The PSConsoleHostReadLine fix is effective on this platform." -ForegroundColor Green
+
     - name: Test Proxy JSON-RPC communication
       shell: pwsh
       timeout-minutes: 2
@@ -402,43 +448,39 @@ jobs:
           $process.StandardInput.Flush()
           Start-Sleep -Milliseconds 200
 
-          # invoke_expression test requires timer event processing (Register-ObjectEvent -Action).
-          # On macOS, timer events don't fire in non-interactive mode (redirected stdin),
-          # even with Start-Sleep or Wait-Event pumping. This is a CI-specific limitation;
-          # production macOS usage launches Terminal.app (interactive) where events work normally.
-          if ($IsMacOS) {
-            Write-Host "`n=== Skipping invoke_expression test on macOS (timer events require interactive session) ===" -ForegroundColor Yellow
-            Write-Host "Named Pipe server detection and Proxy JSON-RPC communication verified successfully."
-            Write-Host "`n=== Named Pipe tests passed (macOS: basic connectivity) ===" -ForegroundColor Green
+          # invoke_expression: PSConsoleHostReadLine fix enables timer event processing
+          # via Start-Sleep polling. This is verified by the preceding
+          # "Test timer event polling mechanism" step. Both CI (via the stdin event-pump
+          # loop already sent above) and interactive (via PSConsoleHostReadLine) use the
+          # same Start-Sleep yield mechanism.
+
+          # Test: invoke_expression with Get-Date (first call - should return get_current_location)
+          Write-Host "`n=== Test: invoke_expression (Get-Date) - First call ===" -ForegroundColor Yellow
+          $invokeRequest = '{"jsonrpc":"2.0","id":10,"method":"tools/call","params":{"name":"invoke_expression","arguments":{"pipeline":"Get-Date -Format yyyy-MM-dd"}}}'
+          $response = Send-JsonRpc $invokeRequest 60000
+          Write-Host "Response (truncated): $($response.Substring(0, [Math]::Min(200, $response.Length)))..."
+
+          if ($response -match "Switched to console" -and $response -match "Pipeline NOT executed") {
+            Write-Host "First invoke_expression: PASSED (expected behavior - command not executed)" -ForegroundColor Green
           } else {
-            # Test: invoke_expression with Get-Date (first call - should return get_current_location)
-            Write-Host "`n=== Test: invoke_expression (Get-Date) - First call ===" -ForegroundColor Yellow
-            $invokeRequest = '{"jsonrpc":"2.0","id":10,"method":"tools/call","params":{"name":"invoke_expression","arguments":{"pipeline":"Get-Date -Format yyyy-MM-dd"}}}'
-            $response = Send-JsonRpc $invokeRequest 60000
-            Write-Host "Response (truncated): $($response.Substring(0, [Math]::Min(200, $response.Length)))..."
-
-            if ($response -match "Switched to console" -and $response -match "Pipeline NOT executed") {
-              Write-Host "First invoke_expression: PASSED (expected behavior - command not executed)" -ForegroundColor Green
-            } else {
-              throw "First invoke_expression did not return expected ''Switched to console'' message"
-            }
+            throw "First invoke_expression did not return expected ''Switched to console'' message"
+          }
 
-            # Test: invoke_expression with Get-Date (second call - should execute)
-            Write-Host "`n=== Test: invoke_expression (Get-Date) - Second call ===" -ForegroundColor Yellow
-            $invokeRequest = '{"jsonrpc":"2.0","id":11,"method":"tools/call","params":{"name":"invoke_expression","arguments":{"pipeline":"Get-Date -Format yyyy-MM-dd"}}}'
-            $response = Send-JsonRpc $invokeRequest 60000
-            Write-Host "Response: $response"
-
-            $today = Get-Date -Format "yyyy-MM-dd"
-            if ($response -match $today) {
-              Write-Host "Second invoke_expression (Get-Date): PASSED" -ForegroundColor Green
-            } else {
-              throw "Second invoke_expression failed - expected date $today not found"
-            }
+          # Test: invoke_expression with Get-Date (second call - should execute)
+          Write-Host "`n=== Test: invoke_expression (Get-Date) - Second call ===" -ForegroundColor Yellow
+          $invokeRequest = '{"jsonrpc":"2.0","id":11,"method":"tools/call","params":{"name":"invoke_expression","arguments":{"pipeline":"Get-Date -Format yyyy-MM-dd"}}}'
+          $response = Send-JsonRpc $invokeRequest 60000
+          Write-Host "Response: $response"
 
-            Write-Host "`n=== All Named Pipe tests passed ===" -ForegroundColor Green
+          $today = Get-Date -Format "yyyy-MM-dd"
+          if ($response -match $today) {
+            Write-Host "Second invoke_expression (Get-Date): PASSED" -ForegroundColor Green
+          } else {
+            throw "Second invoke_expression failed - expected date $today not found"
           }
 
+          Write-Host "`n=== All Named Pipe tests passed ===" -ForegroundColor Green
+
         } finally {
           if (-not $process.HasExited) { $process.Kill() }
           $process.Dispose()

Staging/PowerShell.MCP.psm1

@@ -2,10 +2,49 @@
 # Provides automatic cleanup when Remove-Module is executed
 
 
-# On Linux/macOS, PSReadLine interferes with timer events
-# Remove it to ensure MCP polling works correctly
+# On Linux/macOS, PSReadLine interferes with timer events.
+# Remove it and replace with a custom PSConsoleHostReadLine that polls
+# Console.KeyAvailable instead of blocking on Console.ReadLine().
+# This allows the MCP timer event action block to run between input polls.
 if (-not $IsWindows) {
     Remove-Module PSReadLine -ErrorAction SilentlyContinue
+
+    function global:PSConsoleHostReadLine {
+        $line = [System.Text.StringBuilder]::new()
+        while ($true) {
+            if ([Console]::KeyAvailable) {
+                $key = [Console]::ReadKey($true)
+                switch ($key.Key) {
+                    'Enter' {
+                        [Console]::WriteLine()
+                        return $line.ToString()
+                    }
+                    'Backspace' {
+                        if ($line.Length -gt 0) {
+                            $line.Length--
+                            [Console]::Write("`b `b")
+                        }
+                    }
+                    default {
+                        # Ctrl+C: cancel current line
+                        if ($key.Key -eq 'C' -and ($key.Modifiers -band [ConsoleModifiers]::Control)) {
+                            [Console]::WriteLine("^C")
+                            return ""
+                        }
+                        if ($key.KeyChar -ge ' ') {
+                            $line.Append($key.KeyChar) | Out-Null
+                            [Console]::Write($key.KeyChar)
+                        }
+                    }
+                }
+            } else {
+                # No input available - sleep briefly.
+                # PowerShell processes the event queue between pipeline statements,
+                # so the MCP timer action block can run during this Sleep.
+                Start-Sleep -Milliseconds 50
+            }
+        }
+    }
 }
 
 # Set OnRemove script block to execute cleanup automatically