🐛 fix(ai): 修正 Anthropic 兼容供应商问答失败

- 为 AnthropicProvider.Chat 与 ChatStream 补充工具调用降级回退
- 首次携带 tools 请求在 400/422/404 时自动去掉 tools 重试一次
- 补充兼容供应商问答回归测试并更新 backlog 记录

Fixes #333

internal/ai/provider/anthropic.go

@@ -283,7 +283,15 @@ func (p *AnthropicProvider) Chat(ctx context.Context, req ai.ChatRequest) (*ai.C
 
 	respBody, err := p.doRequest(ctx, body)
 	if err != nil {
-		return nil, err
+		if len(req.Tools) > 0 && isHTTP400Error(err) {
+			body.Tools = nil
+			respBody, err = p.doRequest(ctx, body)
+			if err != nil {
+				return nil, err
+			}
+		} else {
+			return nil, err
+		}
 	}
 	defer respBody.Close()
 
@@ -366,7 +374,15 @@ func (p *AnthropicProvider) ChatStream(ctx context.Context, req ai.ChatRequest,
 
 	respBody, err := p.doRequest(ctx, body)
 	if err != nil {
-		return err
+		if len(req.Tools) > 0 && isHTTP400Error(err) {
+			body.Tools = nil
+			respBody, err = p.doRequest(ctx, body)
+			if err != nil {
+				return err
+			}
+		} else {
+			return err
+		}
 	}
 	defer respBody.Close()
 

internal/ai/provider/anthropic_test.go

@@ -1,8 +1,15 @@
 package provider
 
 import (
+	"context"
+	"encoding/json"
+	"io"
 	"net/http"
+	"net/http/httptest"
+	"strings"
 	"testing"
+
+	"GoNavi-Wails/internal/ai"
 )
 
 func TestNormalizeAnthropicMessagesURL_AppendsMessagesSuffix(t *testing.T) {
@@ -55,3 +62,147 @@ func TestApplyAnthropicAuthHeaders_UsesBearerForDashScopeCompatibleAnthropic(t *
 		t.Fatalf("expected no anthropic-version header for DashScope, got %q", got)
 	}
 }
+
+func TestAnthropicProviderChatRetriesWithoutToolsOnHTTP400(t *testing.T) {
+	requestCount := 0
+	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		requestCount++
+		if r.URL.Path != "/v1/messages" {
+			t.Fatalf("unexpected request path: %s", r.URL.Path)
+		}
+		body, err := io.ReadAll(r.Body)
+		if err != nil {
+			t.Fatalf("read request body failed: %v", err)
+		}
+		defer r.Body.Close()
+
+		var payload map[string]interface{}
+		if err := json.Unmarshal(body, &payload); err != nil {
+			t.Fatalf("unmarshal request body failed: %v", err)
+		}
+
+		if _, hasTools := payload["tools"]; hasTools {
+			http.Error(w, `{"error":{"message":"tools unsupported"}}`, http.StatusBadRequest)
+			return
+		}
+
+		w.Header().Set("Content-Type", "application/json")
+		_, _ = w.Write([]byte(`{"content":[{"type":"text","text":"pong"}],"usage":{"input_tokens":1,"output_tokens":1}}`))
+	}))
+	defer server.Close()
+
+	providerInstance, err := NewAnthropicProvider(ai.ProviderConfig{
+		Type:        "anthropic",
+		Name:        "test-anthropic",
+		APIKey:      "sk-test",
+		BaseURL:     server.URL,
+		Model:       "claude-test",
+		MaxTokens:   64,
+		Temperature: 0.1,
+	})
+	if err != nil {
+		t.Fatalf("create provider failed: %v", err)
+	}
+
+	resp, err := providerInstance.Chat(context.Background(), ai.ChatRequest{
+		Messages: []ai.Message{{Role: "user", Content: "ping"}},
+		Tools: []ai.Tool{{
+			Type: "function",
+			Function: ai.ToolFunction{
+				Name:        "get_tables",
+				Description: "test tool",
+				Parameters: map[string]interface{}{
+					"type": "object",
+				},
+			},
+		}},
+	})
+	if err != nil {
+		t.Fatalf("expected chat fallback to succeed, got %v", err)
+	}
+	if resp.Content != "pong" {
+		t.Fatalf("expected fallback content %q, got %q", "pong", resp.Content)
+	}
+	if requestCount != 2 {
+		t.Fatalf("expected 2 requests (with tools then fallback), got %d", requestCount)
+	}
+}
+
+func TestAnthropicProviderChatStreamRetriesWithoutToolsOnHTTP400(t *testing.T) {
+	requestCount := 0
+	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		requestCount++
+		if r.URL.Path != "/v1/messages" {
+			t.Fatalf("unexpected request path: %s", r.URL.Path)
+		}
+		body, err := io.ReadAll(r.Body)
+		if err != nil {
+			t.Fatalf("read request body failed: %v", err)
+		}
+		defer r.Body.Close()
+
+		var payload map[string]interface{}
+		if err := json.Unmarshal(body, &payload); err != nil {
+			t.Fatalf("unmarshal request body failed: %v", err)
+		}
+
+		if _, hasTools := payload["tools"]; hasTools {
+			http.Error(w, `{"error":{"message":"tools unsupported"}}`, http.StatusBadRequest)
+			return
+		}
+
+		w.Header().Set("Content-Type", "text/event-stream")
+		_, _ = w.Write([]byte(strings.Join([]string{
+			`data: {"type":"content_block_delta","delta":{"type":"text_delta","text":"pong"}}`,
+			``,
+			`data: {"type":"message_stop"}`,
+			``,
+		}, "\n")))
+	}))
+	defer server.Close()
+
+	providerInstance, err := NewAnthropicProvider(ai.ProviderConfig{
+		Type:        "anthropic",
+		Name:        "test-anthropic",
+		APIKey:      "sk-test",
+		BaseURL:     server.URL,
+		Model:       "claude-test",
+		MaxTokens:   64,
+		Temperature: 0.1,
+	})
+	if err != nil {
+		t.Fatalf("create provider failed: %v", err)
+	}
+
+	var chunks []ai.StreamChunk
+	err = providerInstance.ChatStream(context.Background(), ai.ChatRequest{
+		Messages: []ai.Message{{Role: "user", Content: "ping"}},
+		Tools: []ai.Tool{{
+			Type: "function",
+			Function: ai.ToolFunction{
+				Name:        "get_tables",
+				Description: "test tool",
+				Parameters: map[string]interface{}{
+					"type": "object",
+				},
+			},
+		}},
+	}, func(chunk ai.StreamChunk) {
+		chunks = append(chunks, chunk)
+	})
+	if err != nil {
+		t.Fatalf("expected stream fallback to succeed, got %v", err)
+	}
+	if requestCount != 2 {
+		t.Fatalf("expected 2 requests (with tools then fallback), got %d", requestCount)
+	}
+	if len(chunks) < 2 {
+		t.Fatalf("expected content and done chunks, got %#v", chunks)
+	}
+	if chunks[0].Content != "pong" {
+		t.Fatalf("expected first chunk content %q, got %#v", "pong", chunks[0])
+	}
+	if !chunks[len(chunks)-1].Done {
+		t.Fatalf("expected final done chunk, got %#v", chunks[len(chunks)-1])
+	}
+}