diff --git a/agent/main.go b/agent/main.go
index 814168a..57e5af7 100644
--- a/agent/main.go
+++ b/agent/main.go
@@ -231,6 +231,14 @@ func cmdRun() error {
 	sup := engine.New(engine.Options{
 		Command: func(ctx context.Context) *exec.Cmd {
 			cmd := exec.CommandContext(ctx, exe, cfg.EngineArgs...)
+			// Run the engine FROM a known directory rather than from whatever
+			// happened to launch us. A double-clicked bundle hands its child
+			// "/", and an engine invoked as `-m behavision` then cannot find
+			// itself - measured on macOS, where it retried forever.
+			cmd.Dir = cfg.EngineDir
+			if cmd.Dir == "" {
+				cmd.Dir = paths.InstallRoot()
+			}
 			// How the engine learns where to send detections. The engine's
 			// config already reads `events.webhook_url: ${BEHAVISION_WEBHOOK_URL}`
 			// and python-dotenv does not override a variable the process
diff --git a/agent/pkg/config/config.go b/agent/pkg/config/config.go
index 52b01ee..92c0772 100644
--- a/agent/pkg/config/config.go
+++ b/agent/pkg/config/config.go
@@ -37,7 +37,18 @@ type Config struct {
 	BrokerCAFile string `json:"broker_ca_file"`
 
 	// Engine process.
-	EngineExe   string   `json:"engine_exe"`
+	EngineExe string `json:"engine_exe"`
+	// EngineDir is the working directory the engine is launched IN. Empty
+	// means the install root.
+	//
+	// It exists because nothing set it, so the engine inherited whatever
+	// launched the app - and for an app started by double-clicking its
+	// bundle that is "/", not anywhere useful. The symptom on macOS was
+	// `python: No module named behavision` repeating forever: the dev engine
+	// is `-m behavision`, which resolves against the working directory. The
+	// same app started from a terminal in the repo worked, which is exactly
+	// the shape of a bug that survives every test run by a developer.
+	EngineDir   string   `json:"engine_dir,omitempty"`
 	EngineArgs  []string `json:"engine_args"`
 	APIBase     string   `json:"api_base"`
 	APIUser     string   `json:"api_user"`
diff --git a/desktop/app.go b/desktop/app.go
index 8be79aa..8cfa1d8 100644
--- a/desktop/app.go
+++ b/desktop/app.go
@@ -105,6 +105,14 @@ func (a *App) startup(ctx context.Context) {
 	a.sup = agentengine.New(agentengine.Options{
 		Command: func(c context.Context) *exec.Cmd {
 			cmd := exec.CommandContext(c, exe, a.cfg.EngineArgs...)
+			// Run the engine FROM a known directory rather than from whatever
+			// happened to launch us. A double-clicked bundle hands its child
+			// "/", and an engine invoked as `-m behavision` then cannot find
+			// itself - measured on macOS, where it retried forever.
+			cmd.Dir = a.cfg.EngineDir
+			if cmd.Dir == "" {
+				cmd.Dir = agentpaths.InstallRoot()
+			}
 			// How the engine learns where to post its detections. Its config
 			// already reads `events.webhook_url: ${BEHAVISION_WEBHOOK_URL}`,
 			// and python-dotenv does not override a variable the process