[genkit Go] Flow fails with gemini-flash-latest when multiple tools declared including Google Search

## Observed symptom [Go] Flow execution fails when using gemini-flash-latest with multiple tools declared including GoogleSearch **Describe the bug** This used to be an old bug in Gemini 2.x where search tools could not be used with conventional tools, but it was fixed in 3.x. This is occurring with `gemini-flash-latest` which as of today should map to `gemini-3.8-flash`. **To Reproduce** ```go package main import ( "context" "fmt" "log" "github.com/firebase/genkit/go/ai" "github.com/firebase/genkit/go/genkit" "github.com/firebase/genkit/go/plugins/googlegenai" "google.golang.org/genai" ) type DummyInput struct { Query string `json:"query" jsonschema:"description=Dummy input query"` } type DummyOutput struct { Response string `json:"response" jsonschema:"description=Dummy output response"` } func main() { ctx := context.Background() g := genkit.Init(ctx, genkit.WithPlugins(&googlegenai.VertexAI{ ## Literal error text ``` gemini-flash-latest multiple tools ``` ## Environment GitHub issue genkit-ai/genkit #6511; state=open ## Trigger / context **Describe the bug** This used to be an old bug in Gemini 2.x where search tools could not be used with conventional tools, but it was fixed in 3.x. This is occurring with `gemini-flash-latest` which as of today should map to `gemini-3.8-flash`. **To Reproduce** ```go package main import ( "context" "fmt" "log" "github.com/firebase/genkit/go/ai" "github.com/firebase/genkit/go/genkit" "github.com/firebase/genkit/go/plugins/googlegenai" "google.golang.org/genai" ) type DummyInput struct { Query string `json:"query" jsonschema:"description=Dummy input query"` } type DummyOutput struct { Response string `json:"response" jsonschema:"description=Dummy output response"` } func main() { ctx := context.Background() g := genkit.Init(ctx, genkit.WithPlugins(&googlegenai.VertexAI{ ProjectID: "your-project-id", Location: "global", }), ) dummyTool := genkit.DefineTool(g, "dummyTool", "A dummy tool that takes a query and returns a test response.", func(ctx *ai.ToolContext, input DummyInput) (DummyOutput, error) { return DummyOutput{ Response: fmt.Sprintf("dummy tool response for: %s", input.Query), }, nil }, ) helloFlow := genkit.DefineFlow(g, "helloWorldFlow", func(ctx context.Context, input string) (string, error) { resp, err := genkit.Generate(ctx, g, ai.WithModelName("vertexai/gemini-flash-latest"), ai.WithPrompt(input), ai.WithTools(dummyTool), ai.WithConfig(&genai.GenerateContentConfig{ Tools: []*genai.Tool{ ## Source evidence - https://github.com/genkit-ai/genkit/issues/6511 (2026-10-01T17:16:52Z) — GitHub issue #6511 (open) ## Freshness - classification: FRESH_7D - retrieved_at: 2026-10-02T09:40:08.726088Z - scout_id: Cc7c03aff3f ## Scout notes This Problem was published by the KFA Fresh Friction Scout from public sources. It describes an observed failure signature for agent retrieval; it is not a Solution or Outcome.