feat(metadata): add stripThinkingBlocks function and related tests

internal/ai/compat/client.go

@@ -189,6 +189,7 @@ func (c *Client) extractMetadataWithModel(ctx context.Context, input, model stri
 	}
 
 	metadataText := strings.TrimSpace(resp.Choices[0].Message.Content)
+	metadataText = stripThinkingBlocks(metadataText)
 	metadataText = stripCodeFence(metadataText)
 	metadataText = extractJSONObject(metadataText)
 	if metadataText == "" {
@@ -320,6 +321,30 @@ func extractJSONObject(s string) string {
 	return s[start : end+1]
 }
 
+// stripThinkingBlocks removes <think>...</think> and <thinking>...</thinking>
+// blocks produced by reasoning models (DeepSeek R1, QwQ, etc.) so that the
+// remaining text can be parsed as JSON without interference from thinking content
+// that may itself contain braces.
+func stripThinkingBlocks(s string) string {
+	for _, tag := range []string{"think", "thinking"} {
+		open := "<" + tag + ">"
+		close := "</" + tag + ">"
+		for {
+			start := strings.Index(s, open)
+			if start == -1 {
+				break
+			}
+			end := strings.Index(s[start:], close)
+			if end == -1 {
+				s = s[:start]
+				break
+			}
+			s = s[:start] + s[start+end+len(close):]
+		}
+	}
+	return strings.TrimSpace(s)
+}
+
 func stripCodeFence(value string) string {
 	value = strings.TrimSpace(value)
 	if !strings.HasPrefix(value, "```") {

internal/ai/compat/client_test.go

@@ -54,6 +54,95 @@ func TestEmbedRetriesTransientFailures(t *testing.T) {
 	}
 }
 
+func TestExtractMetadataStripsThinkingBlocks(t *testing.T) {
+	cases := []struct {
+		name    string
+		content string
+	}{
+		{
+			name:    "think tag with braces inside",
+			content: "<think>\nLet me map {this} to the schema carefully.\n</think>\n{\"people\":[],\"action_items\":[],\"dates_mentioned\":[],\"topics\":[\"test\"],\"type\":\"idea\",\"source\":\"\"}",
+		},
+		{
+			name:    "thinking tag",
+			content: "<thinking>reasoning {here}</thinking>{\"people\":[],\"action_items\":[],\"dates_mentioned\":[],\"topics\":[\"test\"],\"type\":\"idea\",\"source\":\"\"}",
+		},
+	}
+
+	for _, tc := range cases {
+		t.Run(tc.name, func(t *testing.T) {
+			content := tc.content
+			server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+				_ = json.NewEncoder(w).Encode(map[string]any{
+					"choices": []map[string]any{
+						{"message": map[string]any{"content": content}},
+					},
+				})
+			}))
+			defer server.Close()
+
+			client := New(Config{
+				Name:          "test",
+				BaseURL:       server.URL,
+				APIKey:        "secret",
+				MetadataModel: "meta-model",
+				HTTPClient:    server.Client(),
+				Log:           discardLogger(),
+			})
+
+			metadata, err := client.ExtractMetadata(context.Background(), "hello")
+			if err != nil {
+				t.Fatalf("ExtractMetadata() error = %v", err)
+			}
+			if metadata.Type != "idea" {
+				t.Fatalf("metadata type = %q, want idea", metadata.Type)
+			}
+		})
+	}
+}
+
+func TestExtractMetadataFallbackModel(t *testing.T) {
+	var calls atomic.Int32
+
+	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		var req chatCompletionsRequest
+		_ = json.NewDecoder(r.Body).Decode(&req)
+
+		if req.Model == "primary-model" {
+			calls.Add(1)
+			http.Error(w, "model unavailable", http.StatusServiceUnavailable)
+			return
+		}
+		_ = json.NewEncoder(w).Encode(map[string]any{
+			"choices": []map[string]any{
+				{"message": map[string]any{"content": "{\"people\":[],\"action_items\":[],\"dates_mentioned\":[],\"topics\":[\"test\"],\"type\":\"task\",\"source\":\"\"}"}},
+			},
+		})
+	}))
+	defer server.Close()
+
+	client := New(Config{
+		Name:                  "test",
+		BaseURL:               server.URL,
+		APIKey:                "secret",
+		MetadataModel:         "primary-model",
+		FallbackMetadataModel: "fallback-model",
+		HTTPClient:            server.Client(),
+		Log:                   discardLogger(),
+	})
+
+	metadata, err := client.ExtractMetadata(context.Background(), "hello")
+	if err != nil {
+		t.Fatalf("ExtractMetadata() error = %v", err)
+	}
+	if metadata.Type != "task" {
+		t.Fatalf("metadata type = %q, want task", metadata.Type)
+	}
+	if calls.Load() == 0 {
+		t.Fatal("primary model was never called")
+	}
+}
+
 func TestExtractMetadataParsesCodeFencedJSON(t *testing.T) {
 	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 		_ = json.NewEncoder(w).Encode(map[string]any{