tool/loadartifactstool: return error instead of panic when artifact service is not configured

agent/common_context.go

@@ -94,7 +94,7 @@ func NewCallbackContextWithArtifactTracking(ic InvocationContext, actions *sessi
 		Context:           ic,
 		invocationContext: ic,
 		actions:           actions,
-		artifacts:         &trackedArtifacts{Artifacts: ic.Artifacts(), actions: actions},
+		artifacts:         newTrackedArtifacts(ic.Artifacts(), actions),
 	}
 	// wrap the commonContext in order to log information about someone using tool-context methods on a callback context
 	wrapper := &callbackContextWrapper{
@@ -132,7 +132,7 @@ func NewToolContext(ic InvocationContext, functionCallID string, actions *sessio
 	res.actions = actions
 	res.functionCallID = functionCallID
 	res.toolConfirmation = confirmation
-	res.artifacts = &trackedArtifacts{Artifacts: ic.Artifacts(), actions: actions}
+	res.artifacts = newTrackedArtifacts(ic.Artifacts(), actions)
 
 	wrapper := &toolContextWrapper{
 		context: &res,
@@ -461,6 +461,17 @@ func (c *callbackContextState) All() iter.Seq2[string, any] {
 	return c.ctx.invocationContext.Session().State().All()
 }
 
+// newTrackedArtifacts wraps inner so that each successful Save is recorded
+// into the supplied EventActions.ArtifactDelta. It returns nil when inner is
+// nil so that "no artifact service configured" stays observable (a nil
+// Artifacts) instead of panicking on the first promoted method call.
+func newTrackedArtifacts(inner Artifacts, actions *session.EventActions) Artifacts {
+	if inner == nil {
+		return nil
+	}
+	return &trackedArtifacts{Artifacts: inner, actions: actions}
+}
+
 // trackedArtifacts wraps an Artifacts to record each successful Save into the
 // supplied EventActions.ArtifactDelta.
 type trackedArtifacts struct {

tool/loadartifactstool/load_artifacts_tool.go

@@ -118,6 +118,9 @@ func (t *artifactsTool) Run(ctx agent.Context, args any) (map[string]any, error)
 // ProcessRequest processes the LLM request. It packs the tool, appends initial
 // instructions, and processes any load artifacts function calls.
 func (t *artifactsTool) ProcessRequest(ctx agent.Context, req *model.LLMRequest) error {
+	if ctx.Artifacts() == nil {
+		return fmt.Errorf("load_artifacts tool requires an artifact service to be configured")
+	}
 	if err := toolutils.PackTool(req, t); err != nil {
 		return err
 	}

tool/loadartifactstool/load_artifacts_tool_test.go

@@ -339,6 +339,75 @@ func TestLoadArtifactsTool_ProcessRequest_Artifacts_OtherFunctionCall(t *testing
 	}
 }
 
+// TestLoadArtifactsTool_ProcessRequest_NilArtifacts verifies that ProcessRequest
+// returns a descriptive error instead of panicking when no artifact service is
+// configured (see https://github.com/google/adk-go/issues/283).
+func TestLoadArtifactsTool_ProcessRequest_NilArtifacts(t *testing.T) {
+	loadArtifactsTool := loadartifactstool.New()
+
+	// Construct a context with no artifact service configured.
+	invocationCtx := icontext.NewInvocationContext(t.Context(), icontext.InvocationContextParams{})
+	tc := agent.NewToolContext(invocationCtx, "", nil, nil)
+
+	requestProcessor, ok := loadArtifactsTool.(toolinternal.RequestProcessor)
+	if !ok {
+		t.Fatal("loadArtifactsTool does not implement RequestProcessor")
+	}
+
+	llmRequest := &model.LLMRequest{}
+	err := requestProcessor.ProcessRequest(tc, llmRequest)
+	if err == nil {
+		t.Fatal("ProcessRequest should return an error when no artifact service is configured, but got nil")
+	}
+	if !strings.Contains(err.Error(), "artifact service") {
+		t.Errorf("error should mention the missing artifact service, got: %v", err)
+	}
+}
+
+// TestLoadArtifactsTool_ProcessRequest_NilArtifacts_WithFunctionCall verifies
+// that the nil-artifact guard in ProcessRequest also covers the
+// processLoadArtifactsFunctionCall path, not only appendInitialInstructions:
+// with a request whose last content is a load_artifacts function response,
+// ProcessRequest must still return the descriptive error instead of panicking
+// on the unguarded ctx.Artifacts() read in that path.
+func TestLoadArtifactsTool_ProcessRequest_NilArtifacts_WithFunctionCall(t *testing.T) {
+	loadArtifactsTool := loadartifactstool.New()
+
+	// Construct a context with no artifact service configured.
+	invocationCtx := icontext.NewInvocationContext(t.Context(), icontext.InvocationContextParams{})
+	tc := agent.NewToolContext(invocationCtx, "", nil, nil)
+
+	functionResponse := &genai.FunctionResponse{
+		Name: "load_artifacts",
+		Response: map[string]any{
+			"artifact_names": []any{"doc1.txt"},
+		},
+	}
+	llmRequest := &model.LLMRequest{
+		Contents: []*genai.Content{
+			{
+				Role: "model",
+				Parts: []*genai.Part{
+					genai.NewPartFromFunctionResponse(functionResponse.Name, functionResponse.Response),
+				},
+			},
+		},
+	}
+
+	requestProcessor, ok := loadArtifactsTool.(toolinternal.RequestProcessor)
+	if !ok {
+		t.Fatal("loadArtifactsTool does not implement RequestProcessor")
+	}
+
+	err := requestProcessor.ProcessRequest(tc, llmRequest)
+	if err == nil {
+		t.Fatal("ProcessRequest should return an error when no artifact service is configured, but got nil")
+	}
+	if !strings.Contains(err.Error(), "artifact service") {
+		t.Errorf("error should mention the missing artifact service, got: %v", err)
+	}
+}
+
 func createToolContext(t *testing.T) agent.Context {
 	t.Helper()