fix(gemini): set IncludeServerSideToolInvocations when using built-in tools with function calling

components/model/gemini/gemini.go

@@ -569,6 +569,27 @@ func (cm *ChatModel) genInputAndConf(input []*schema.Message, opts ...model.Opti
 		return "", nil, nil, nil, err
 	}
 
+	// When using built-in tools (e.g. GoogleSearch, URLContext) alongside function calling,
+	// the Gemini API requires IncludeServerSideToolInvocations to be enabled.
+	hasBuiltInTools := cm.enableGoogleSearch != nil || cm.enableGoogleSearchRetrieval != nil ||
+		cm.enableCodeExecution || cm.enableComputerUse != nil || cm.enableURLContext != nil ||
+		cm.enableFileSearch != nil || cm.enableGoogleMaps != nil
+	if hasBuiltInTools && len(tools) > 0 {
+		if cm.cli.ClientConfig().Backend == genai.BackendVertexAI {
+			return "", nil, nil, nil, fmt.Errorf("combining built-in tools with function calling requires IncludeServerSideToolInvocations, which is not supported by the Vertex AI backend")
+		}
+		if m.ToolConfig == nil {
+			m.ToolConfig = &genai.ToolConfig{}
+		}
+		m.ToolConfig.IncludeServerSideToolInvocations = genai.Ptr(true)
+		// AUTO mode is not supported when IncludeServerSideToolInvocations is enabled; default to VALIDATED.
+		if m.ToolConfig.FunctionCallingConfig == nil {
+			m.ToolConfig.FunctionCallingConfig = &genai.FunctionCallingConfig{Mode: genai.FunctionCallingConfigModeValidated}
+		} else if mode := m.ToolConfig.FunctionCallingConfig.Mode; mode == genai.FunctionCallingConfigModeAuto || mode == genai.FunctionCallingConfigModeUnspecified || mode == "" {
+			m.ToolConfig.FunctionCallingConfig.Mode = genai.FunctionCallingConfigModeValidated
+		}
+	}
+
 	if geminiOptions.ResponseJSONSchema != nil {
 		m.ResponseMIMEType = "application/json"
 		m.ResponseJsonSchema = geminiOptions.ResponseJSONSchema

components/model/gemini/gemini_test.go

@@ -1249,6 +1249,92 @@ func TestPopulateToolChoice(t *testing.T) {
 	}
 }
 
+func TestIncludeServerSideToolInvocations(t *testing.T) {
+	ctx := context.Background()
+	funcTools := []*genai.FunctionDeclaration{{Name: "tool1"}}
+	user := []*schema.Message{{Role: schema.User, Content: "hi"}}
+
+	geminiClient := &genai.Client{Models: &genai.Models{}}
+	vertexClient, err := genai.NewClient(ctx, &genai.ClientConfig{
+		Backend: genai.BackendVertexAI,
+		APIKey:  "fake-key",
+	})
+	assert.NoError(t, err)
+	assert.Equal(t, genai.BackendVertexAI, vertexClient.ClientConfig().Backend)
+
+	t.Run("built-in tool with function calling defaults to VALIDATED", func(t *testing.T) {
+		cm := &ChatModel{
+			cli:                geminiClient,
+			model:              "gemini-x",
+			tools:              funcTools,
+			enableGoogleSearch: &genai.GoogleSearch{},
+		}
+		_, _, m, _, err := cm.genInputAndConf(user)
+		assert.NoError(t, err)
+		assert.NotNil(t, m.ToolConfig)
+		assert.NotNil(t, m.ToolConfig.IncludeServerSideToolInvocations)
+		assert.True(t, *m.ToolConfig.IncludeServerSideToolInvocations)
+		assert.NotNil(t, m.ToolConfig.FunctionCallingConfig)
+		assert.Equal(t, genai.FunctionCallingConfigModeValidated, m.ToolConfig.FunctionCallingConfig.Mode)
+	})
+
+	t.Run("AUTO mode is switched to VALIDATED", func(t *testing.T) {
+		toolChoiceAllowed := schema.ToolChoiceAllowed
+		cm := &ChatModel{
+			cli:                geminiClient,
+			model:              "gemini-x",
+			tools:              funcTools,
+			toolChoice:         &toolChoiceAllowed,
+			enableGoogleSearch: &genai.GoogleSearch{},
+		}
+		_, _, m, _, err := cm.genInputAndConf(user)
+		assert.NoError(t, err)
+		assert.NotNil(t, m.ToolConfig.IncludeServerSideToolInvocations)
+		assert.True(t, *m.ToolConfig.IncludeServerSideToolInvocations)
+		assert.Equal(t, genai.FunctionCallingConfigModeValidated, m.ToolConfig.FunctionCallingConfig.Mode)
+	})
+
+	t.Run("forced (ANY) mode is preserved", func(t *testing.T) {
+		toolChoiceForced := schema.ToolChoiceForced
+		cm := &ChatModel{
+			cli:                geminiClient,
+			model:              "gemini-x",
+			tools:              funcTools,
+			toolChoice:         &toolChoiceForced,
+			enableGoogleSearch: &genai.GoogleSearch{},
+		}
+		_, _, m, _, err := cm.genInputAndConf(user)
+		assert.NoError(t, err)
+		assert.True(t, *m.ToolConfig.IncludeServerSideToolInvocations)
+		assert.Equal(t, genai.FunctionCallingConfigModeAny, m.ToolConfig.FunctionCallingConfig.Mode)
+	})
+
+	t.Run("no built-in tools leaves flag unset", func(t *testing.T) {
+		cm := &ChatModel{
+			cli:   geminiClient,
+			model: "gemini-x",
+			tools: funcTools,
+		}
+		_, _, m, _, err := cm.genInputAndConf(user)
+		assert.NoError(t, err)
+		if m.ToolConfig != nil {
+			assert.Nil(t, m.ToolConfig.IncludeServerSideToolInvocations)
+		}
+	})
+
+	t.Run("vertex backend returns unsupported error", func(t *testing.T) {
+		cm := &ChatModel{
+			cli:                vertexClient,
+			model:              "gemini-x",
+			tools:              funcTools,
+			enableGoogleSearch: &genai.GoogleSearch{},
+		}
+		_, _, _, _, err := cm.genInputAndConf(user)
+		assert.Error(t, err)
+		assert.Contains(t, err.Error(), "Vertex AI")
+	})
+}
+
 // isValidUUID checks if a string is a valid UUID format
 func isValidUUID(u string) bool {
 	_, err := uuid.Parse(u)

components/model/gemini/go.mod

@@ -7,9 +7,10 @@ require (
 	github.com/bytedance/sonic v1.14.1
 	github.com/cloudwego/eino v0.7.13
 	github.com/eino-contrib/jsonschema v1.0.3
+	github.com/google/uuid v1.6.0
 	github.com/stretchr/testify v1.10.0
 	github.com/wk8/go-ordered-map/v2 v2.1.8
-	google.golang.org/genai v1.36.0
+	google.golang.org/genai v1.52.1
 )
 
 require (
@@ -26,7 +27,6 @@ require (
 	github.com/golang/groupcache v0.0.0-20210331224755-41bb18bfe9da // indirect
 	github.com/google/go-cmp v0.6.0 // indirect
 	github.com/google/s2a-go v0.1.8 // indirect
-	github.com/google/uuid v1.6.0 // indirect
 	github.com/googleapis/enterprise-certificate-proxy v0.3.4 // indirect
 	github.com/goph/emperror v0.17.2 // indirect
 	github.com/gopherjs/gopherjs v1.17.2 // indirect

components/model/gemini/go.sum

@@ -218,8 +218,8 @@ golang.org/x/tools v0.0.0-20190524140312-2c0ae7006135/go.mod h1:RgjU9mgBXZiqYHBn
 golang.org/x/xerrors v0.0.0-20191204190536-9bdfabe68543/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=
 google.golang.org/appengine v1.1.0/go.mod h1:EbEs0AVv82hx2wNQdGPgUI5lhzA/G0D9YwlJXL52JkM=
 google.golang.org/appengine v1.4.0/go.mod h1:xpcJRLb0r/rnEns0DIKYYv+WjYCduHsrkT7/EB5XEv4=
-google.golang.org/genai v1.36.0 h1:sJCIjqTAmwrtAIaemtTiKkg2TO1RxnYEusTmEQ3nGxM=
-google.golang.org/genai v1.36.0/go.mod h1:A3kkl0nyBjyFlNjgxIwKq70julKbIxpSxqKO5gw/gmk=
+google.golang.org/genai v1.52.1 h1:dYoljKtLDXMiBdVaClSJ/ZPwZ7j1N0lGjMhwOKOQUlk=
+google.golang.org/genai v1.52.1/go.mod h1:A3kkl0nyBjyFlNjgxIwKq70julKbIxpSxqKO5gw/gmk=
 google.golang.org/genproto v0.0.0-20180817151627-c66870c02cf8/go.mod h1:JiN7NxoALGmiZfu7CAH4rXhgtRTLTxftemlI0sWmxmc=
 google.golang.org/genproto v0.0.0-20190819201941-24fa4b261c55/go.mod h1:DMBHOl98Agz4BDEuKkezgsaosCRResVns1a3J2ZsMNc=
 google.golang.org/genproto v0.0.0-20200526211855-cb27e3aa2013/go.mod h1:NbSheEEYHJ7i3ixzK3sjbqSGDJWnxyFXZblF3eUsNvo=