Summary
Codex Desktop can start the PowerShell.MCP server from PowerShell.MCP 1.12.0 and can run non-expression tools such as console startup and current-location discovery, but expression execution fails at the MCP tool dispatch layer before any PowerShell pipeline runs.
Environment
- OS: Windows 11, Microsoft Windows NT 10.0.26200.0
- Host: PAYTON-LEGION2
- PowerShell: 7.6.3 from Microsoft Store WindowsApps package
- PowerShell.MCP installed versions: 1.12.0, 1.11.0, 1.8.0
- Active Codex MCP server command: C:\Users\kingd\OneDrive\Documents\PowerShell\Modules\PowerShell.MCP\1.12.0\bin\win-x64\PowerShell.MCP.Proxy.exe
- 1.12.0 proxy product version: 1.12.0.0+edec71c29d58e183c13912e7ec58e6dac84e3c2a
Observed behavior
Codex tool calls:
- mcp__powershell.start_console succeeds and reports PowerShell.MCP module imported.
- mcp__powershell.get_current_location succeeds.
- mcp__powershell.invoke_expression fails before the PowerShell script executes.
Exact returned error:
unsupported call: mcp__powershellinvoke_expression
The error also occurs for a minimal expression:
probe
Expected behavior
mcp__powershell.invoke_expression should execute the provided PowerShell pipeline in the persistent PowerShell console, or return a structured MCP error that includes enough information to distinguish proxy dispatch failure from PowerShell runtime failure.
Diagnostics performed
- Verified Codex config points to the 1.12.0 proxy executable.
- Verified PowerShell.MCP 1.12.0 is installed and proxy exists.
- Checked Windows Event Viewer logs around the failure window. No PowerShell stack trace or application crash was recorded for the unsupported call failure. PowerShell Operational logs only showed normal console startup and ready events.
- The failure appears to occur before a PowerShell pipeline reaches the runtime.
Impact
This blocks Codex from using PowerShell.MCP for required shell execution because the main command execution tool cannot run expressions.
Summary
Codex Desktop can start the PowerShell.MCP server from PowerShell.MCP 1.12.0 and can run non-expression tools such as console startup and current-location discovery, but expression execution fails at the MCP tool dispatch layer before any PowerShell pipeline runs.
Environment
Observed behavior
Codex tool calls:
Exact returned error:
unsupported call: mcp__powershellinvoke_expression
The error also occurs for a minimal expression:
probe
Expected behavior
mcp__powershell.invoke_expression should execute the provided PowerShell pipeline in the persistent PowerShell console, or return a structured MCP error that includes enough information to distinguish proxy dispatch failure from PowerShell runtime failure.
Diagnostics performed
Impact
This blocks Codex from using PowerShell.MCP for required shell execution because the main command execution tool cannot run expressions.