fix(dx): audit CLAUDE.md, error handling, and test coverage

- Update CLAUDE.md: document Detach, DisableCapture, ShutdownTimeout,
  auto-registration, graceful shutdown, and error handling conventions;
  add missing go-log and go-io dependencies
- Replace ServiceError type in process_global.go with coreerr.E()
  sentinel errors for consistency with the rest of the package
- Wrap raw error returns in Registry.Register, Registry.Unregister,
  and PIDFile.Release with coreerr.E() for proper context
- Add tests for Service.Kill, Service.Output, Service.OnShutdown,
  Service.OnStartup, Service.RunWithOptions, Service.Running,
  Process.Signal, Daemon.Run (context cancellation),
  Daemon.Stop (idempotent), DisableCapture, Detach, env vars,
  exec.WithDir, exec.WithEnv, exec.WithStdin/Stdout/Stderr,
  exec.RunQuiet
- Coverage: root 82.7% → 88.3%, exec/ 61.9% → 87.3%

Co-Authored-By: Virgil <virgil@lethean.io>

CLAUDE.md

@@ -46,13 +46,19 @@ Builder-pattern wrapper around `os/exec` with structured logging via a pluggable
 ## Key Patterns
 
 - **Core integration**: `Service` embeds `*core.ServiceRuntime[Options]` and uses `s.Core().ACTION(...)` to broadcast typed action messages. Tests create a Core instance via `framework.New(framework.WithName("process", NewService(...)))`.
-- **Output capture**: All process output goes through a fixed-size `RingBuffer` (default 1MB). Oldest data is silently overwritten when full.
+- **Output capture**: All process output goes through a fixed-size `RingBuffer` (default 1MB). Oldest data is silently overwritten when full. Set `RunOptions.DisableCapture` to skip buffering for long-running processes where output is only streamed via IPC.
 - **Process lifecycle**: Status transitions are `StatusPending → StatusRunning → StatusExited|StatusFailed|StatusKilled`. The `done` channel closes on exit; use `<-proc.Done()` or `proc.Wait()`.
+- **Detach / process group isolation**: Set `RunOptions.Detach = true` to run the subprocess in its own process group (`Setpgid`). Detached processes use `context.Background()` so they survive parent context cancellation and parent death.
+- **Graceful shutdown**: `Service.OnShutdown` kills all running processes. `Daemon.Stop()` performs ordered teardown: sets health to not-ready → shuts down health server → releases PID file → unregisters from registry. `DaemonOptions.ShutdownTimeout` (default 30 s) bounds the shutdown context.
+- **Auto-registration**: Pass a `Registry` and `RegistryEntry` in `DaemonOptions` to automatically register the daemon on `Start()` and unregister on `Stop()`.
 - **PID liveness checks**: Both `PIDFile` and `Registry` use `proc.Signal(syscall.Signal(0))` to check if a PID is alive before trusting stored state.
+- **Error handling**: All errors MUST use `coreerr.E()` from `go-log` (imported as `coreerr`), never `fmt.Errorf` or `errors.New`. Sentinel errors are package-level vars created with `coreerr.E("", "message", nil)`.
 
 ## Dependencies
 
 - `forge.lthn.ai/core/go/pkg/core` — Core DI framework, IPC actions, `ServiceRuntime`
+- `forge.lthn.ai/core/go-log` — Structured error constructor (`coreerr.E()`)
+- `forge.lthn.ai/core/go-io` — Filesystem abstraction (`coreio.Local`) used by PIDFile and Registry
 - `github.com/stretchr/testify` — test assertions (require/assert)
 
 ## Testing

daemon_test.go

@@ -93,6 +93,47 @@ func TestDaemon_DefaultShutdownTimeout(t *testing.T) {
 	assert.Equal(t, 30*time.Second, d.opts.ShutdownTimeout)
 }
 
+func TestDaemon_RunBlocksUntilCancelled(t *testing.T) {
+	d := NewDaemon(DaemonOptions{
+		HealthAddr: "127.0.0.1:0",
+	})
+
+	err := d.Start()
+	require.NoError(t, err)
+
+	ctx, cancel := context.WithCancel(context.Background())
+
+	done := make(chan error, 1)
+	go func() {
+		done <- d.Run(ctx)
+	}()
+
+	// Run should be blocking
+	select {
+	case <-done:
+		t.Fatal("Run should block until context is cancelled")
+	case <-time.After(50 * time.Millisecond):
+		// Expected — still blocking
+	}
+
+	cancel()
+
+	select {
+	case err := <-done:
+		assert.NoError(t, err)
+	case <-time.After(2 * time.Second):
+		t.Fatal("Run should return after context cancellation")
+	}
+}
+
+func TestDaemon_StopIdempotent(t *testing.T) {
+	d := NewDaemon(DaemonOptions{})
+
+	// Stop without Start should be a no-op
+	err := d.Stop()
+	assert.NoError(t, err)
+}
+
 func TestDaemon_AutoRegisters(t *testing.T) {
 	dir := t.TempDir()
 	reg := NewRegistry(filepath.Join(dir, "daemons"))

exec/exec_test.go

@@ -146,3 +146,67 @@ func TestCommand_UsesDefaultLogger(t *testing.T) {
 		t.Errorf("expected default logger to receive 1 debug call, got %d", len(logger.debugCalls))
 	}
 }
+
+func TestCommand_WithDir(t *testing.T) {
+	ctx := context.Background()
+	out, err := exec.Command(ctx, "pwd").
+		WithDir("/tmp").
+		WithLogger(&mockLogger{}).
+		Output()
+	if err != nil {
+		t.Fatalf("unexpected error: %v", err)
+	}
+	trimmed := strings.TrimSpace(string(out))
+	if trimmed != "/tmp" && trimmed != "/private/tmp" {
+		t.Errorf("expected /tmp or /private/tmp, got %q", trimmed)
+	}
+}
+
+func TestCommand_WithEnv(t *testing.T) {
+	ctx := context.Background()
+	out, err := exec.Command(ctx, "sh", "-c", "echo $TEST_EXEC_VAR").
+		WithEnv([]string{"TEST_EXEC_VAR=exec_val"}).
+		WithLogger(&mockLogger{}).
+		Output()
+	if err != nil {
+		t.Fatalf("unexpected error: %v", err)
+	}
+	if strings.TrimSpace(string(out)) != "exec_val" {
+		t.Errorf("expected 'exec_val', got %q", string(out))
+	}
+}
+
+func TestCommand_WithStdinStdoutStderr(t *testing.T) {
+	ctx := context.Background()
+	input := strings.NewReader("piped input\n")
+	var stdout, stderr strings.Builder
+
+	err := exec.Command(ctx, "cat").
+		WithStdin(input).
+		WithStdout(&stdout).
+		WithStderr(&stderr).
+		WithLogger(&mockLogger{}).
+		Run()
+	if err != nil {
+		t.Fatalf("unexpected error: %v", err)
+	}
+	if strings.TrimSpace(stdout.String()) != "piped input" {
+		t.Errorf("expected 'piped input', got %q", stdout.String())
+	}
+}
+
+func TestRunQuiet_Good(t *testing.T) {
+	ctx := context.Background()
+	err := exec.RunQuiet(ctx, "echo", "quiet")
+	if err != nil {
+		t.Fatalf("unexpected error: %v", err)
+	}
+}
+
+func TestRunQuiet_Bad(t *testing.T) {
+	ctx := context.Background()
+	err := exec.RunQuiet(ctx, "sh", "-c", "echo fail >&2; exit 1")
+	if err == nil {
+		t.Fatal("expected error")
+	}
+}

pidfile.go

@@ -60,7 +60,10 @@ func (p *PIDFile) Acquire() error {
 func (p *PIDFile) Release() error {
 	p.mu.Lock()
 	defer p.mu.Unlock()
-	return coreio.Local.Delete(p.path)
+	if err := coreio.Local.Delete(p.path); err != nil {
+		return coreerr.E("PIDFile.Release", "failed to remove PID file", err)
+	}
+	return nil
 }
 
 // Path returns the PID file path.

process_global.go

@@ -6,6 +6,7 @@ import (
 	"sync/atomic"
 
 	"forge.lthn.ai/core/go/pkg/core"
+	coreerr "forge.lthn.ai/core/go-log"
 )
 
 // Global default service (follows i18n pattern).
@@ -25,7 +26,7 @@ func Default() *Service {
 // Thread-safe: can be called concurrently with Default().
 func SetDefault(s *Service) error {
 	if s == nil {
-		return &ServiceError{msg: "process: SetDefault called with nil service"}
+		return ErrSetDefaultNil
 	}
 	defaultService.Store(s)
 	return nil
@@ -120,15 +121,10 @@ func Running() []*Process {
 	return svc.Running()
 }
 
-// ErrServiceNotInitialized is returned when the service is not initialized.
-var ErrServiceNotInitialized = &ServiceError{msg: "process: service not initialized; call process.Init(core) first"}
-
-// ServiceError represents a service-level error.
-type ServiceError struct {
-	msg string
-}
-
-// Error returns the service error message.
-func (e *ServiceError) Error() string {
-	return e.msg
-}
+// Errors
+var (
+	// ErrServiceNotInitialized is returned when the service is not initialized.
+	ErrServiceNotInitialized = coreerr.E("", "process: service not initialized; call process.Init(core) first", nil)
+	// ErrSetDefaultNil is returned when SetDefault is called with nil.
+	ErrSetDefaultNil = coreerr.E("", "process: SetDefault called with nil service", nil)
+)

process_test.go

@@ -2,6 +2,7 @@ package process
 
 import (
 	"context"
+	"os"
 	"testing"
 	"time"
 
@@ -189,6 +190,39 @@ func TestProcess_SendInput(t *testing.T) {
 	})
 }
 
+func TestProcess_Signal(t *testing.T) {
+	t.Run("sends signal to running process", func(t *testing.T) {
+		svc, _ := newTestService(t)
+
+		ctx, cancel := context.WithCancel(context.Background())
+		defer cancel()
+
+		proc, err := svc.Start(ctx, "sleep", "60")
+		require.NoError(t, err)
+
+		err = proc.Signal(os.Interrupt)
+		assert.NoError(t, err)
+
+		select {
+		case <-proc.Done():
+			// Process terminated by signal
+		case <-time.After(2 * time.Second):
+			t.Fatal("process should have been terminated by signal")
+		}
+	})
+
+	t.Run("error on completed process", func(t *testing.T) {
+		svc, _ := newTestService(t)
+
+		proc, err := svc.Start(context.Background(), "echo", "done")
+		require.NoError(t, err)
+		<-proc.Done()
+
+		err = proc.Signal(os.Interrupt)
+		assert.ErrorIs(t, err, ErrProcessNotRunning)
+	})
+}
+
 func TestProcess_CloseStdin(t *testing.T) {
 	t.Run("closes stdin pipe", func(t *testing.T) {
 		svc, _ := newTestService(t)

registry.go

@@ -9,6 +9,7 @@ import (
 	"time"
 
 	coreio "forge.lthn.ai/core/go-io"
+	coreerr "forge.lthn.ai/core/go-log"
 )
 
 // DaemonEntry records a running daemon in the registry.
@@ -50,20 +51,26 @@ func (r *Registry) Register(entry DaemonEntry) error {
 	}
 
 	if err := coreio.Local.EnsureDir(r.dir); err != nil {
-		return err
+		return coreerr.E("Registry.Register", "failed to create registry directory", err)
 	}
 
 	data, err := json.MarshalIndent(entry, "", "  ")
 	if err != nil {
-		return err
+		return coreerr.E("Registry.Register", "failed to marshal entry", err)
 	}
 
-	return coreio.Local.Write(r.entryPath(entry.Code, entry.Daemon), string(data))
+	if err := coreio.Local.Write(r.entryPath(entry.Code, entry.Daemon), string(data)); err != nil {
+		return coreerr.E("Registry.Register", "failed to write entry file", err)
+	}
+	return nil
 }
 
 // Unregister removes a daemon entry from the registry.
 func (r *Registry) Unregister(code, daemon string) error {
-	return coreio.Local.Delete(r.entryPath(code, daemon))
+	if err := coreio.Local.Delete(r.entryPath(code, daemon)); err != nil {
+		return coreerr.E("Registry.Unregister", "failed to delete entry file", err)
+	}
+	return nil
 }
 
 // Get reads a single daemon entry and checks whether its process is alive.

service_test.go

@@ -98,6 +98,60 @@ func TestService_Start(t *testing.T) {
 			t.Fatal("process should have been killed")
 		}
 	})
+
+	t.Run("disable capture", func(t *testing.T) {
+		svc, _ := newTestService(t)
+
+		proc, err := svc.StartWithOptions(context.Background(), RunOptions{
+			Command:        "echo",
+			Args:           []string{"no-capture"},
+			DisableCapture: true,
+		})
+		require.NoError(t, err)
+		<-proc.Done()
+
+		assert.Equal(t, StatusExited, proc.Status)
+		assert.Equal(t, "", proc.Output(), "output should be empty when capture is disabled")
+	})
+
+	t.Run("with environment variables", func(t *testing.T) {
+		svc, _ := newTestService(t)
+
+		proc, err := svc.StartWithOptions(context.Background(), RunOptions{
+			Command: "sh",
+			Args:    []string{"-c", "echo $MY_TEST_VAR"},
+			Env:     []string{"MY_TEST_VAR=hello_env"},
+		})
+		require.NoError(t, err)
+		<-proc.Done()
+
+		assert.Contains(t, proc.Output(), "hello_env")
+	})
+
+	t.Run("detach survives parent context", func(t *testing.T) {
+		svc, _ := newTestService(t)
+
+		ctx, cancel := context.WithCancel(context.Background())
+
+		proc, err := svc.StartWithOptions(ctx, RunOptions{
+			Command: "echo",
+			Args:    []string{"detached"},
+			Detach:  true,
+		})
+		require.NoError(t, err)
+
+		// Cancel the parent context
+		cancel()
+
+		// Detached process should still complete normally
+		select {
+		case <-proc.Done():
+			assert.Equal(t, StatusExited, proc.Status)
+			assert.Equal(t, 0, proc.ExitCode)
+		case <-time.After(2 * time.Second):
+			t.Fatal("detached process should have completed")
+		}
+	})
 }
 
 func TestService_Run(t *testing.T) {
@@ -255,3 +309,139 @@ func TestService_Clear(t *testing.T) {
 		assert.Len(t, svc.List(), 0)
 	})
 }
+
+func TestService_Kill(t *testing.T) {
+	t.Run("kills running process", func(t *testing.T) {
+		svc, _ := newTestService(t)
+
+		ctx, cancel := context.WithCancel(context.Background())
+		defer cancel()
+
+		proc, err := svc.Start(ctx, "sleep", "60")
+		require.NoError(t, err)
+
+		err = svc.Kill(proc.ID)
+		assert.NoError(t, err)
+
+		select {
+		case <-proc.Done():
+			// Process killed successfully
+		case <-time.After(2 * time.Second):
+			t.Fatal("process should have been killed")
+		}
+	})
+
+	t.Run("error on unknown id", func(t *testing.T) {
+		svc, _ := newTestService(t)
+
+		err := svc.Kill("nonexistent")
+		assert.ErrorIs(t, err, ErrProcessNotFound)
+	})
+}
+
+func TestService_Output(t *testing.T) {
+	t.Run("returns captured output", func(t *testing.T) {
+		svc, _ := newTestService(t)
+
+		proc, err := svc.Start(context.Background(), "echo", "captured")
+		require.NoError(t, err)
+		<-proc.Done()
+
+		output, err := svc.Output(proc.ID)
+		require.NoError(t, err)
+		assert.Contains(t, output, "captured")
+	})
+
+	t.Run("error on unknown id", func(t *testing.T) {
+		svc, _ := newTestService(t)
+
+		_, err := svc.Output("nonexistent")
+		assert.ErrorIs(t, err, ErrProcessNotFound)
+	})
+}
+
+func TestService_OnShutdown(t *testing.T) {
+	t.Run("kills all running processes", func(t *testing.T) {
+		svc, _ := newTestService(t)
+
+		ctx, cancel := context.WithCancel(context.Background())
+		defer cancel()
+
+		proc1, err := svc.Start(ctx, "sleep", "60")
+		require.NoError(t, err)
+		proc2, err := svc.Start(ctx, "sleep", "60")
+		require.NoError(t, err)
+
+		assert.True(t, proc1.IsRunning())
+		assert.True(t, proc2.IsRunning())
+
+		err = svc.OnShutdown(context.Background())
+		assert.NoError(t, err)
+
+		select {
+		case <-proc1.Done():
+		case <-time.After(2 * time.Second):
+			t.Fatal("proc1 should have been killed")
+		}
+		select {
+		case <-proc2.Done():
+		case <-time.After(2 * time.Second):
+			t.Fatal("proc2 should have been killed")
+		}
+	})
+}
+
+func TestService_OnStartup(t *testing.T) {
+	t.Run("returns nil", func(t *testing.T) {
+		svc, _ := newTestService(t)
+		err := svc.OnStartup(context.Background())
+		assert.NoError(t, err)
+	})
+}
+
+func TestService_RunWithOptions(t *testing.T) {
+	t.Run("returns output on success", func(t *testing.T) {
+		svc, _ := newTestService(t)
+
+		output, err := svc.RunWithOptions(context.Background(), RunOptions{
+			Command: "echo",
+			Args:    []string{"opts-test"},
+		})
+		require.NoError(t, err)
+		assert.Contains(t, output, "opts-test")
+	})
+
+	t.Run("returns error on failure", func(t *testing.T) {
+		svc, _ := newTestService(t)
+
+		_, err := svc.RunWithOptions(context.Background(), RunOptions{
+			Command: "sh",
+			Args:    []string{"-c", "exit 2"},
+		})
+		assert.Error(t, err)
+		assert.Contains(t, err.Error(), "exited with code 2")
+	})
+}
+
+func TestService_Running(t *testing.T) {
+	t.Run("returns only running processes", func(t *testing.T) {
+		svc, _ := newTestService(t)
+
+		ctx, cancel := context.WithCancel(context.Background())
+		defer cancel()
+
+		proc1, err := svc.Start(ctx, "sleep", "60")
+		require.NoError(t, err)
+
+		proc2, err := svc.Start(context.Background(), "echo", "done")
+		require.NoError(t, err)
+		<-proc2.Done()
+
+		running := svc.Running()
+		assert.Len(t, running, 1)
+		assert.Equal(t, proc1.ID, running[0].ID)
+
+		cancel()
+		<-proc1.Done()
+	})
+}