Bug 1: detect copilot.cmd/.bat on Windows and invoke the sibling .ps1 directly via powershell -File, bypassing cmd.exe %* re-tokenisation that mangled the multi-line -p prompt. Shared rewriteCmdToPS1() now serves cursor, pi, and copilot.
Bug 2: filterCustomArgs (shared by all agent backends) strips one outer layer of shell quotes via unshellQuoteArg() before processing, so shell-style custom args like --deny-tool='write' no longer reach the CLI with literal quotes.
Pi is installed on Windows via npm, which lays down `pi.cmd` → `pi.ps1`
→ `node_modules/@mariozechner/pi-coding-agent/dist/cli.js`. The daemon
spawns Pi with `exec.Command("pi", ...)`; PATHEXT resolves that to
`pi.cmd`, and cmd.exe expands `%*` in the shim by re-tokenising the
original command line, which truncates any argv containing newlines.
buildPiArgs passes the full prompt as the last positional argv, so the
multi-line system+user prompt is silently cut at the first newline
before it reaches the JS entrypoint. The session JSONL then records
only the first line ("You are running as a chat assistant for a Multica
workspace.") and Pi replies as if the user message were missing
(GitHub multica-ai/multica#3306).
Mirror the existing cursor-agent fix: when LookPath resolves Pi to a
.cmd/.bat launcher and a sibling pi.ps1 exists, invoke PowerShell with
`-File <ps1>` directly and forward each arg as a discrete token. This
keeps us on the official launch path while skipping the cmd.exe %*
re-expansion. Falls back to the original launcher when pi.ps1 or
PowerShell can't be located.
The Windows test asserts the rewrite produces the expected argv and
that the multi-line positional prompt survives unchanged.
Co-authored-by: J <j@multica.ai>
Co-authored-by: multica-agent <github@multica.ai>
