Fix tool loop handling and count tokens endpoint

internal/httpapi/server.go

@@ -117,6 +117,7 @@ func NewServer(addr string, svc *service.Service) *Server {
 	mux.HandleFunc("/v1/props", s.handleModelProps)
 	mux.HandleFunc("/props", s.handleModelProps)
 	mux.HandleFunc("/version", s.handleVersion)
+	mux.HandleFunc("/v1/messages/count_tokens", s.handleAnthropicCountTokens)
 	mux.HandleFunc("/v1/messages", s.handleAnthropicMessages)
 	mux.HandleFunc("/v1/chat/completions", s.handleOpenAIChatCompletions)
 	mux.HandleFunc("/api/v1/chat/completions", s.handleOpenAIChatCompletions)
@@ -446,6 +447,27 @@ func (s *Server) handleVersion(w http.ResponseWriter, r *http.Request) {
 	})
 }
 
+func (s *Server) handleAnthropicCountTokens(w http.ResponseWriter, r *http.Request) {
+	if r.Method == http.MethodOptions {
+		w.WriteHeader(http.StatusNoContent)
+		return
+	}
+	if r.Method != http.MethodPost {
+		writeAnthropicError(w, http.StatusMethodNotAllowed, "invalid_request_error", "method not allowed")
+		return
+	}
+
+	var req anthropicRequest
+	if err := decodeJSON(r, &req); err != nil {
+		writeAnthropicError(w, http.StatusBadRequest, "invalid_request_error", err.Error())
+		return
+	}
+
+	writeJSON(w, http.StatusOK, map[string]any{
+		"input_tokens": estimateAnthropicInputTokens(req),
+	})
+}
+
 func (s *Server) handleAnthropicMessages(w http.ResponseWriter, r *http.Request) {
 	if r.Method == http.MethodOptions {
 		w.WriteHeader(http.StatusNoContent)
@@ -1292,6 +1314,9 @@ func anthropicHostedWebSearchCall(req anthropicRequest) (toolemulation.ToolCall,
 	if !hasAnthropicHostedWebSearchTool(req.Tools) {
 		return toolemulation.ToolCall{}, false
 	}
+	if hasAnthropicToolResult(req.Messages) {
+		return toolemulation.ToolCall{}, false
+	}
 	if !anthropicHostedWebSearchRequested(req.Tools, req.ToolChoice) {
 		return toolemulation.ToolCall{}, false
 	}
@@ -1307,6 +1332,46 @@ func anthropicHostedWebSearchCall(req anthropicRequest) (toolemulation.ToolCall,
 	}, true
 }
 
+func hasAnthropicToolResult(messages []rawMessage) bool {
+	for _, message := range messages {
+		items, ok := message.Content.([]any)
+		if !ok {
+			continue
+		}
+		for _, item := range items {
+			m, ok := item.(map[string]any)
+			if ok && stringFromAny(m["type"]) == "tool_result" {
+				return true
+			}
+		}
+	}
+	return false
+}
+
+func estimateAnthropicInputTokens(req anthropicRequest) int {
+	payload := map[string]any{
+		"model":       req.Model,
+		"system":      req.System,
+		"messages":    req.Messages,
+		"tools":       req.Tools,
+		"tool_choice": req.ToolChoice,
+		"thinking":    req.Thinking,
+	}
+	raw, err := json.Marshal(payload)
+	if err != nil {
+		return 1
+	}
+	runes := len([]rune(string(raw)))
+	if runes == 0 {
+		return 1
+	}
+	tokens := (runes + 2) / 3
+	if tokens < 1 {
+		return 1
+	}
+	return tokens
+}
+
 func hasAnthropicHostedWebSearchTool(raw any) bool {
 	items, ok := raw.([]any)
 	if !ok {

internal/httpapi/server_test.go

@@ -218,6 +218,64 @@ func TestAnthropicHostedWebSearchCallIgnoresRegularClientWebSearch(t *testing.T)
 	}
 }
 
+func TestAnthropicHostedWebSearchCallIgnoresToolResultFollowup(t *testing.T) {
+	req := anthropicRequest{
+		Tools: []any{
+			map[string]any{
+				"name": "web_search",
+				"type": "web_search_20250305",
+			},
+		},
+		ToolChoice: map[string]any{
+			"type": "tool",
+			"name": "web_search",
+		},
+		Messages: []rawMessage{{
+			Role: "user",
+			Content: []any{
+				map[string]any{
+					"type":        "tool_result",
+					"tool_use_id": "toolu_123",
+					"content":     "result",
+				},
+			},
+		}},
+	}
+
+	if _, ok := anthropicHostedWebSearchCall(req); ok {
+		t.Fatal("hosted web_search should not short-circuit after a tool_result")
+	}
+}
+
+func TestAnthropicCountTokensEndpoint(t *testing.T) {
+	server := NewServer("", service.New(service.Config{
+		Model:   "Qwen3-Coder",
+		Timeout: time.Second,
+	}))
+
+	req := httptest.NewRequest(http.MethodPost, "/v1/messages/count_tokens", strings.NewReader(`{
+		"model":"kmodel",
+		"max_tokens":128,
+		"system":"You are concise.",
+		"messages":[{"role":"user","content":"hello"}],
+		"tools":[{"name":"read_file","input_schema":{"type":"object","properties":{"file_path":{"type":"string"}},"required":["file_path"]}}]
+	}`))
+	req.Header.Set("Content-Type", "application/json")
+	rec := httptest.NewRecorder()
+	server.http.Handler.ServeHTTP(rec, req)
+
+	if rec.Code != http.StatusOK {
+		t.Fatalf("status = %d body = %s", rec.Code, rec.Body.String())
+	}
+	var body map[string]any
+	if err := json.Unmarshal(rec.Body.Bytes(), &body); err != nil {
+		t.Fatal(err)
+	}
+	if body["input_tokens"].(float64) <= 0 {
+		t.Fatalf("input_tokens = %#v", body["input_tokens"])
+	}
+}
+
 func TestDiscoveryCompatibilityEndpoints(t *testing.T) {
 	server := NewServer("", service.New(service.Config{
 		Model:   "Qwen3-Coder",