fix(backgroundjobs): resolve status race condition and subprocess pipe hang

pkg/desktop/transport/transport_test.go

@@ -243,7 +243,7 @@ func TestFallbackTransport_NonSocketErrorDoesNotDisableProxy(t *testing.T) {
 	req, err := http.NewRequestWithContext(t.Context(), http.MethodGet, "http://example.invalid/", http.NoBody)
 	require.NoError(t, err)
 
-	resp, err := ft.RoundTrip(req) //nolint:bodyclose // resp is nil on error, checked below
+	resp, err := ft.RoundTrip(req) //nolint:bodyclose,nolintlint // resp is nil on error, checked below
 	require.Error(t, err)
 	require.Nil(t, resp)
 	assert.True(t, errors.Is(err, upstreamErr) || err.Error() == upstreamErr.Error())

pkg/selfupdate/exec_windows.go

@@ -3,6 +3,7 @@
 package selfupdate
 
 import (
+	"context"
 	"fmt"
 	"os"
 	"os/exec"
@@ -27,9 +28,9 @@ func swapBinary(dst, src string) error {
 		if cpErr := atomicWriteFromFile(dst, src); cpErr != nil {
 			// Roll back so we never leave the install without a binary.
 			if rbErr := os.Rename(old, dst); rbErr != nil {
-				return fmt.Errorf("installing new binary: %w (copy fallback failed: %v; rollback also failed: %v)", err, cpErr, rbErr)
+				return fmt.Errorf("installing new binary: %w (copy fallback failed: %w; rollback also failed: %w)", err, cpErr, rbErr)
 			}
-			return fmt.Errorf("installing new binary: %w (copy fallback failed: %v)", err, cpErr)
+			return fmt.Errorf("installing new binary: %w (copy fallback failed: %w)", err, cpErr)
 		}
 		_ = os.Remove(src)
 	}
@@ -48,7 +49,7 @@ func reExecProcess(path string, args, env []string) error {
 		childArgs = args[1:]
 	}
 
-	cmd := exec.Command(path, childArgs...) //nolint:gosec // path is our own freshly installed binary
+	cmd := exec.CommandContext(context.Background(), path, childArgs...)
 	cmd.Env = env
 	cmd.Stdin = os.Stdin
 	cmd.Stdout = os.Stdout

pkg/snapshot/snapshot.go

@@ -453,7 +453,7 @@ func (r *Repo) DiffFull(ctx context.Context, from, to string) ([]FileDiff, error
 }
 
 func (r *Repo) ensure(ctx context.Context) error {
-	if err := os.MkdirAll(r.gitdir, 0o755); err != nil { //nolint:gosec // 0o755 matches the layout `git init` itself creates
+	if err := os.MkdirAll(r.gitdir, 0o755); err != nil { //nolint:gosec,nolintlint // 0o755 matches the layout `git init` itself creates
 		return err
 	}
 	if _, err := os.Stat(filepath.Join(r.gitdir, "HEAD")); err == nil {
@@ -623,10 +623,10 @@ func (r *Repo) syncExcludes(ctx context.Context, list []string) error {
 		text += "\n"
 	}
 	target := filepath.Join(r.gitdir, "info", "exclude")
-	if err := os.MkdirAll(filepath.Dir(target), 0o755); err != nil { //nolint:gosec // mirrors what git writes into .git/info
+	if err := os.MkdirAll(filepath.Dir(target), 0o755); err != nil { //nolint:gosec,nolintlint // mirrors what git writes into .git/info
 		return err
 	}
-	return os.WriteFile(target, []byte(text), 0o644) //nolint:gosec // mirrors what git writes for .git/info/exclude
+	return os.WriteFile(target, []byte(text), 0o644) //nolint:gosec,nolintlint // mirrors what git writes for .git/info/exclude
 }
 
 func (r *Repo) args(cmd ...string) []string {

pkg/tools/builtin/backgroundjobs/backgroundjobs.go

@@ -37,6 +37,7 @@ const (
 	ToolNameWaitBackgroundJob = "wait_background_job"
 
 	maxBackgroundJobOutputBytes = 10 * 1024 * 1024
+	waitDelayAfterJobExit       = 1 * time.Second
 )
 
 // ToolSet manages long-running shell commands.
@@ -224,6 +225,7 @@ func (h *backgroundJobsHandler) runBackgroundJob(ctx context.Context, rt tools.R
 	cmd.Env = h.env
 	cmd.Dir = h.resolveWorkDir(params.Cwd)
 	cmd.SysProcAttr = platformSpecificSysProcAttr()
+	cmd.WaitDelay = waitDelayAfterJobExit
 
 	job := &backgroundJob{
 		id:        jobID,
@@ -278,17 +280,23 @@ func (h *backgroundJobsHandler) monitorJob(ctx context.Context, job *backgroundJ
 		return
 	}
 
+	var newStatus int32
 	if err != nil {
 		if exitErr, ok := errors.AsType[*exec.ExitError](err); ok {
 			job.exitCode = exitErr.ExitCode()
 		} else {
 			job.exitCode = -1
 		}
-		job.status.Store(statusFailed)
+		newStatus = statusFailed
 		job.err = err
 	} else {
 		job.exitCode = 0
-		job.status.Store(statusCompleted)
+		newStatus = statusCompleted
+	}
+
+	if !job.status.CompareAndSwap(statusRunning, newStatus) {
+		job.outputMu.Unlock()
+		return
 	}
 
 	status := job.status.Load()

pkg/tools/builtin/backgroundjobs/backgroundjobs_test.go

@@ -3,6 +3,7 @@ package backgroundjobs
 import (
 	"context"
 	"encoding/json"
+	"path/filepath"
 	"runtime"
 	"testing"
 	"time"
@@ -398,7 +399,12 @@ func TestBackgroundJobsTool_Instructions(t *testing.T) {
 func TestResolveWorkDir(t *testing.T) {
 	t.Parallel()
 
-	workingDir := "/configured/project"
+	workingDir := filepath.FromSlash("/configured/project")
+	absOther := filepath.FromSlash("/tmp/another")
+	if runtime.GOOS == "windows" {
+		workingDir = `C:\configured\project`
+		absOther = `C:\tmp\another`
+	}
 	h := &backgroundJobsHandler{workingDir: workingDir}
 
 	tests := []struct {
@@ -408,10 +414,10 @@ func TestResolveWorkDir(t *testing.T) {
 	}{
 		{name: "empty defaults to workingDir", cwd: "", expected: workingDir},
 		{name: "dot defaults to workingDir", cwd: ".", expected: workingDir},
-		{name: "absolute path unchanged", cwd: "/tmp/other", expected: "/tmp/other"},
-		{name: "relative path joined with workingDir", cwd: "src/pkg", expected: "/configured/project/src/pkg"},
-		{name: "relative with dot prefix", cwd: "./subdir", expected: "/configured/project/subdir"},
-		{name: "relative with parent traversal", cwd: "../sibling", expected: "/configured/sibling"},
+		{name: "absolute path unchanged", cwd: absOther, expected: absOther},
+		{name: "relative path joined with workingDir", cwd: "src/pkg", expected: filepath.Join(workingDir, "src", "pkg")},
+		{name: "relative with dot prefix", cwd: "./subdir", expected: filepath.Join(workingDir, "subdir")},
+		{name: "relative with parent traversal", cwd: "../sibling", expected: filepath.Clean(filepath.Join(workingDir, "..", "sibling"))},
 	}
 
 	for _, tt := range tests {

pkg/tools/builtin/backgroundjobs/cmd_windows.go

@@ -31,13 +31,13 @@ func createProcessGroup(proc *os.Process) (*processGroup, error) {
 	if _, err := windows.SetInformationJobObject(
 		job,
 		windows.JobObjectExtendedLimitInformation,
-		uintptr(unsafe.Pointer(&info)),
+		uintptr(unsafe.Pointer(&info)), //nolint:gosec // Windows syscall requires unsafe pointer
 		uint32(unsafe.Sizeof(info))); err != nil {
 		_ = windows.CloseHandle(job)
 		return nil, err
 	}
 
-	handle, err := windows.OpenProcess(windows.PROCESS_SET_QUOTA|windows.PROCESS_TERMINATE, false, uint32(proc.Pid))
+	handle, err := windows.OpenProcess(windows.PROCESS_SET_QUOTA|windows.PROCESS_TERMINATE, false, uint32(proc.Pid)) //nolint:gosec // Windows PID fits in uint32
 	if err != nil {
 		_ = windows.CloseHandle(job)
 		return nil, err

pkg/tools/builtin/shell/cmd_windows.go

@@ -31,13 +31,13 @@ func createProcessGroup(proc *os.Process) (*processGroup, error) {
 	if _, err := windows.SetInformationJobObject(
 		job,
 		windows.JobObjectExtendedLimitInformation,
-		uintptr(unsafe.Pointer(&info)),
+		uintptr(unsafe.Pointer(&info)), //nolint:gosec // Windows syscall requires unsafe pointer
 		uint32(unsafe.Sizeof(info))); err != nil {
 		_ = windows.CloseHandle(job)
 		return nil, err
 	}
 
-	handle, err := windows.OpenProcess(windows.PROCESS_SET_QUOTA|windows.PROCESS_TERMINATE, false, uint32(proc.Pid))
+	handle, err := windows.OpenProcess(windows.PROCESS_SET_QUOTA|windows.PROCESS_TERMINATE, false, uint32(proc.Pid)) //nolint:gosec // Windows PID fits in uint32
 	if err != nil {
 		_ = windows.CloseHandle(job)
 		return nil, err