hooks: harden timeout kill and add platform split

- Move runHook into build-tagged implementations (unix/windows) to keep unix syscalls off Windows builds.
- In unix implementation, guard nil Process, return wrapped kill errors except ESRCH, and document linkage to TestRunSync_KillsDescendants.
- On Windows, best-effort kill on timeout retains prior behavior.
- In tests, move testing.Short earlier and keep descendant-kill coverage on Linux.

internal/hooks/hooks.go

@@ -3,13 +3,8 @@
 package hooks
 
 import (
-	"bytes"
-	"context"
-	"encoding/json"
 	"os"
-	"os/exec"
 	"path/filepath"
-	"syscall"
 	"time"
 
 	"github.com/steveyegge/beads/internal/types"
@@ -99,62 +94,6 @@ func (r *Runner) RunSync(event string, issue *types.Issue) error {
 	return r.runHook(hookPath, event, issue)
 }
 
-func (r *Runner) runHook(hookPath, event string, issue *types.Issue) error {
-	ctx, cancel := context.WithTimeout(context.Background(), r.timeout)
-	defer cancel()
-
-	// Prepare JSON data for stdin
-	issueJSON, err := json.Marshal(issue)
-	if err != nil {
-		return err
-	}
-
-	// Create command: hook_script <issue_id> <event_type>
-	// #nosec G204 -- hookPath is from controlled .beads/hooks directory
-	cmd := exec.CommandContext(ctx, hookPath, issue.ID, event)
-	cmd.Stdin = bytes.NewReader(issueJSON)
-
-	// Capture output for debugging (but don't block on it)
-	var stdout, stderr bytes.Buffer
-	cmd.Stdout = &stdout
-	cmd.Stderr = &stderr
-
-	// Start the hook so we can manage its process group and kill children on timeout.
-	//
-	// Rationale: scripts may spawn child processes (backgrounded or otherwise).
-	// If we only kill the immediate process, descendants may survive and keep
-	// the test (or caller) blocked — see TestRunSync_Timeout which previously
-	// observed a `sleep 60` still running after the parent process was killed.
-	// Creating a process group (Setpgid) and sending a negative PID to
-	// `syscall.Kill` ensures the entire group (parent + children) are killed
-	// reliably on timeout.
-	cmd.SysProcAttr = &syscall.SysProcAttr{Setpgid: true}
-
-	if err := cmd.Start(); err != nil {
-		return err
-	}
-
-	done := make(chan error, 1)
-	go func() {
-		done <- cmd.Wait()
-	}()
-
-	select {
-	case <-ctx.Done():
-		// Kill the whole process group to ensure any children (e.g., sleep)
-		// are also terminated.
-		_ = syscall.Kill(-cmd.Process.Pid, syscall.SIGKILL)
-		// Wait for process to exit
-		<-done
-		return ctx.Err()
-	case err := <-done:
-		if err != nil {
-			return err
-		}
-		return nil
-	}
-}
-
 // HookExists checks if a hook exists for an event
 func (r *Runner) HookExists(event string) bool {
 	hookName := eventToHook(event)

internal/hooks/hooks_test.go

@@ -260,6 +260,10 @@ func TestRunSync_KillsDescendants(t *testing.T) {
 		t.Skip("TestRunSync_KillsDescendants requires Linux /proc")
 	}
 
+	if testing.Short() {
+		t.Skip("Skipping long-running descendant kill test in short mode")
+	}
+
 	tmpDir := t.TempDir()
 	hookPath := filepath.Join(tmpDir, HookOnCreate)
 	pidFile := filepath.Join(tmpDir, "child.pid")
@@ -279,10 +283,6 @@ func TestRunSync_KillsDescendants(t *testing.T) {
 	}
 	issue := &types.Issue{ID: "bd-test", Title: "Test"}
 
-	if testing.Short() {
-		t.Skip("Skipping long-running descendant kill test in short mode")
-	}
-
 	err := runner.RunSync(EventCreate, issue)
 	if err == nil {
 		t.Fatal("Expected RunSync to return an error on timeout")

internal/hooks/hooks_unix.go

@@ -0,0 +1,74 @@
+//go:build unix
+
+package hooks
+
+import (
+	"bytes"
+	"context"
+	"encoding/json"
+	"errors"
+	"fmt"
+	"os/exec"
+	"syscall"
+
+	"github.com/steveyegge/beads/internal/types"
+)
+
+// runHook executes the hook and enforces a timeout, killing the process group
+// on expiration to ensure descendant processes are terminated.
+func (r *Runner) runHook(hookPath, event string, issue *types.Issue) error {
+	ctx, cancel := context.WithTimeout(context.Background(), r.timeout)
+	defer cancel()
+
+	// Prepare JSON data for stdin
+	issueJSON, err := json.Marshal(issue)
+	if err != nil {
+		return err
+	}
+
+	// Create command: hook_script <issue_id> <event_type>
+	// #nosec G204 -- hookPath is from controlled .beads/hooks directory
+	cmd := exec.CommandContext(ctx, hookPath, issue.ID, event)
+	cmd.Stdin = bytes.NewReader(issueJSON)
+
+	// Capture output for debugging (but don't block on it)
+	var stdout, stderr bytes.Buffer
+	cmd.Stdout = &stdout
+	cmd.Stderr = &stderr
+
+	// Start the hook so we can manage its process group and kill children on timeout.
+	//
+	// Rationale: scripts may spawn child processes (backgrounded or otherwise).
+	// If we only kill the immediate process, descendants may survive and keep
+	// the test (or caller) blocked — this was exposed by TestRunSync_Timeout and
+	// validated by TestRunSync_KillsDescendants. Creating a process group (Setpgid)
+	// and sending a negative PID to syscall.Kill ensures the entire group
+	// (parent + children) are killed reliably on timeout.
+	cmd.SysProcAttr = &syscall.SysProcAttr{Setpgid: true}
+
+	if err := cmd.Start(); err != nil {
+		return err
+	}
+
+	done := make(chan error, 1)
+	go func() {
+		done <- cmd.Wait()
+	}()
+
+	select {
+	case <-ctx.Done():
+		if cmd.Process != nil {
+			if err := syscall.Kill(-cmd.Process.Pid, syscall.SIGKILL); err != nil && !errors.Is(err, syscall.ESRCH) {
+				return fmt.Errorf("kill process group: %w", err)
+			}
+		}
+		// Wait for process to exit after the kill attempt
+		<-done
+		return ctx.Err()
+	case err := <-done:
+		if err != nil {
+			return err
+		}
+		return nil
+	}
+}

internal/hooks/hooks_windows.go

@@ -0,0 +1,53 @@
+//go:build windows
+
+package hooks
+
+import (
+	"bytes"
+	"context"
+	"encoding/json"
+	"os/exec"
+
+	"github.com/steveyegge/beads/internal/types"
+)
+
+// runHook executes the hook and enforces a timeout on Windows.
+// Windows lacks Unix-style process groups; on timeout we best-effort kill
+// the started process. Descendant processes may survive if they detach,
+// but this preserves previous behavior while keeping tests green on Windows.
+func (r *Runner) runHook(hookPath, event string, issue *types.Issue) error {
+	ctx, cancel := context.WithTimeout(context.Background(), r.timeout)
+	defer cancel()
+
+	issueJSON, err := json.Marshal(issue)
+	if err != nil {
+		return err
+	}
+
+	cmd := exec.CommandContext(ctx, hookPath, issue.ID, event)
+	cmd.Stdin = bytes.NewReader(issueJSON)
+
+	var stdout, stderr bytes.Buffer
+	cmd.Stdout = &stdout
+	cmd.Stderr = &stderr
+
+	if err := cmd.Start(); err != nil {
+		return err
+	}
+
+	done := make(chan error, 1)
+	go func() {
+		done <- cmd.Wait()
+	}()
+
+	select {
+	case <-ctx.Done():
+		if cmd.Process != nil {
+			_ = cmd.Process.Kill()
+		}
+		<-done
+		return ctx.Err()
+	case err := <-done:
+		return err
+	}
+}