fix: use command.process_group(0) for CLI providers, not just MCP

[codefromthecrypt]

Summary

Ctrl+C cannot cancel CLI provider responses — the user must wait for the full response. The subprocess shares the parent's process group and receives SIGINT directly, racing with goose's cancel_token and preventing the cancel branch from firing.

MCP servers already had process_group(0) in extension_manager.rs. This PR centralizes it into configure_command_no_window() in subprocess.rs, isolating all subprocesses. With the fix, the subprocess never receives SIGINT and the cancel token wins cleanly.

I could not reproduce the "Broken pipe" from #7070 — the claude CLI (2.1.37) survives SIGINT. Other CLI providers may not. The fix eliminates this variable.

Type of Change

• Bug fix

AI Assistance

• This PR was created or reviewed with AI assistance

Testing

Before (goose v1.23.2, no process_group(0) on CLI providers): Ctrl+C has no effect. The response completes in full and cannot be interrupted.

$ goose --version                                                                                                                                                                 
 1.23.2
$ claude --version
2.1.37 (Claude Code)
$ goose
starting session | provider: claude-code model: claude-sonnet-4-20250514
    session id: 20260209_22
    working directory: /Users/codefromthecrypt/oss/goose

goose is running! Enter your instructions, or try asking what goose can do.

Context: ○○○○○○○○○○ 0% (0/200000 tokens)
( O)> write a poem
Here's a poem for you:

---

**The Goose That Codes**

A goose once wandered through the wire,
Through circuits humming, climbing higher,
Not feathered wings but Rust and steel,
With tools and agents at its heel.

It parsed the prompts, it read the files,
It traversed directories for miles,
Through crates and modules, line by line,
It made the tangled code align.

"Honk!" it said, or so we'd dream,
As tokens flowed in endless stream,
No pond, no bread, no grassy lawn—
Just terminals from dusk to dawn.

So raise a cup to goose, our friend,
Who'll debug with you until the end,
An agent born of open source,
A most magnificent digital goose. 🪿

---

⏱️  Elapsed time: 9.87s
Context: ○○○○○○○○○○ 0% (4/200000 tokens)
( O)> write a poem again
Here's another one for you:
--snip--

After (dev build with process_group(0) in subprocess.rs): Ctrl+C cancels immediately. Retry works.

$ cargo build -p goose-cli
--snip--
$ target/debug/goose
starting session | provider: claude-code model: claude-sonnet-4-20250514
    session id: 20260209_19
    working directory: /Users/codefromthecrypt/oss/goose

goose is running! Enter your instructions, or try asking what goose can do.

Context: ○○○○○○○○○○ 0% (0/200000 tokens)
( O)> write a poem
◒  Unifying understanding units...                                                                                                                                                                               ^CInterrupted before the model replied and removed the last message.

⏱️  Elapsed time: 0.59s
Context: ○○○○○○○○○○ 0% (0/200000 tokens)
( O)> write a poem again
◓  Exploring solution space...                                                                                                                                                                                   ◓  Exploring solution space...                                                                                                                                                                                   ◒  Exploring solution space...                                                                                                                                                                                   Interrupted before the model replied and removed the last message.

⏱️  Elapsed time: 1.48s
Context: ○○○○○○○○○○ 0% (0/200000 tokens)

Related Issues

Relates to #7070 once this change is in, the original "ctrl-c" test should be retried with the latest version of claude-code.

Related claude-code issues: #16135, #17466

Follow-up: The surviving subprocess may continue writing stale output after Ctrl+C. A follow-up PR will drain or cancel this before the next turn.

[Copilot]

Pull request overview

This PR fixes Ctrl+C cancellation for CLI-based providers by ensuring spawned subprocesses are isolated into their own process group on Unix, preventing them from receiving SIGINT intended for goose.

Changes:

• Centralize Unix process_group(0) configuration into configure_command_no_window() so it applies consistently to CLI provider subprocesses.
• Remove the now-redundant process_group(0) call from the MCP extension manager path.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 2 comments.

File	Description
crates/goose/src/subprocess.rs	Extends the shared subprocess configuration helper to also isolate Unix subprocesses into their own process group.
crates/goose/src/agents/extension_manager.rs	Removes the local process_group(0) call in favor of the centralized helper.

[Copilot]

Pull request overview

Copilot reviewed 6 out of 6 changed files in this pull request and generated 2 comments.

[michaelneale]

this looks nice.