diff --git a/apps/desktop/src/main.ts b/apps/desktop/src/main.ts
index fed7d5d..e86665e 100644
--- a/apps/desktop/src/main.ts
+++ b/apps/desktop/src/main.ts
@@ -631,11 +631,18 @@ async function handleRegister(profile: MachineProfile, form: HTMLFormElement) {
     })
 
     if (!response.ok) {
-      let message = `Falha ao registrar máquina (${response.status})`
+      const status = response.status
+      let message = `Falha ao registrar máquina (${status})`
       try {
-        const errorBody = await response.json()
-        if (errorBody?.error) {
-          message = errorBody.error
+        // tenta JSON
+        const ct = response.headers.get("content-type") || ""
+        if (ct.includes("application/json")) {
+          const errorBody = await response.json()
+          if (errorBody?.error) message = `${message}: ${String(errorBody.error)}`
+          if (errorBody?.details) message += ` — ${String(errorBody.details)}`
+        } else {
+          const text = await response.text()
+          if (text && text.length < 500) message += ` — ${text}`
         }
       } catch {
         // ignore