modelfiles: fix /save command and add shortname for safetensors based models (#15413)

This change fixes two issues with Modelfiles:

  1. If a user uses `ollama show --modelfile` to show a safetensors based
     model, the Model would leave the "FROM" field blank which won't allow
     a user to recreate the model. This change adds the model's current
     canonical short name to the FROM field.
  2. If a user uses the `/save` command in the CLI any messages which were
     saved in a previous model wouldn't get saved (only the set of messages
     from the current session).

server/routes.go

@@ -1308,9 +1308,17 @@ func GetModelInfo(req api.ShowRequest) (*api.ShowResponse, error) {
 
 	var sb strings.Builder
 	fmt.Fprintln(&sb, "# Modelfile generated by \"ollama show\"")
-	fmt.Fprintln(&sb, "# To build a new Modelfile based on this, replace FROM with:")
-	fmt.Fprintf(&sb, "# FROM %s\n\n", m.ShortName)
-	fmt.Fprint(&sb, m.String())
+	modelfile := m.String()
+	if m.IsMLX() {
+		fmt.Fprintf(&sb, "FROM %s\n", m.ShortName)
+		if _, rest, ok := strings.Cut(modelfile, "\n"); ok {
+			fmt.Fprint(&sb, rest)
+		}
+	} else {
+		fmt.Fprintln(&sb, "# To build a new Modelfile based on this, replace FROM with:")
+		fmt.Fprintf(&sb, "# FROM %s\n\n", m.ShortName)
+		fmt.Fprint(&sb, modelfile)
+	}
 	resp.Modelfile = sb.String()
 
 	// skip loading tensor information if this is a remote model

server/routes_test.go

@@ -580,6 +580,41 @@ func TestGetModelInfo_SafetensorsUsesStoredFileType(t *testing.T) {
 	}
 }
 
+func TestGetModelInfo_SafetensorsModelfileUsesShortName(t *testing.T) {
+	t.Setenv("OLLAMA_MODELS", t.TempDir())
+
+	cfgData, err := json.Marshal(model.ConfigV2{
+		ModelFormat:  "safetensors",
+		Capabilities: []string{"completion"},
+	})
+	if err != nil {
+		t.Fatalf("failed to marshal config: %v", err)
+	}
+
+	configLayer, err := manifest.NewLayer(bytes.NewReader(cfgData), "application/vnd.docker.container.image.v1+json")
+	if err != nil {
+		t.Fatalf("failed to create config layer: %v", err)
+	}
+
+	name := model.ParseName("show-safetensors")
+	if err := manifest.WriteManifest(name, configLayer, nil); err != nil {
+		t.Fatalf("failed to write manifest: %v", err)
+	}
+
+	resp, err := GetModelInfo(api.ShowRequest{Model: name.String()})
+	if err != nil {
+		t.Fatalf("GetModelInfo() error = %v", err)
+	}
+
+	if !strings.Contains(resp.Modelfile, "FROM show-safetensors:latest\n") {
+		t.Fatalf("Modelfile = %q, want FROM show-safetensors:latest", resp.Modelfile)
+	}
+
+	if strings.Contains(resp.Modelfile, "# To build a new Modelfile based on this, replace FROM with:") {
+		t.Fatalf("Modelfile should not include replacement hint: %q", resp.Modelfile)
+	}
+}
+
 func casingShuffle(s string) string {
 	rr := []rune(s)
 	for i := range rr {