fix: correctly set disable_parallel_tool_use

bridge_integration_test.go

@@ -22,6 +22,7 @@ import (
 	"cdr.dev/slog/sloggers/slogtest"
 	"github.com/anthropics/anthropic-sdk-go"
 	"github.com/anthropics/anthropic-sdk-go/packages/ssestream"
+	"github.com/anthropics/anthropic-sdk-go/shared/constant"
 	"github.com/coder/aibridge"
 	"github.com/coder/aibridge/mcp"
 	"github.com/google/uuid"
@@ -1352,6 +1353,152 @@ func TestStableRequestEncoding(t *testing.T) {
 	}
 }
 
+// TestAnthropicToolChoiceParallelDisabled verifies that parallel tool use is
+// correctly disabled based on the tool_choice parameter in the request.
+// See https://github.com/coder/aibridge/issues/2
+func TestAnthropicToolChoiceParallelDisabled(t *testing.T) {
+	t.Parallel()
+
+	var (
+		toolChoiceAuto = string(constant.ValueOf[constant.Auto]())
+		toolChoiceAny  = string(constant.ValueOf[constant.Any]())
+		toolChoiceNone = string(constant.ValueOf[constant.None]())
+		toolChoiceTool = string(constant.ValueOf[constant.Tool]())
+	)
+
+	cases := []struct {
+		name                          string
+		toolChoice                    any // nil, or map with "type" key.
+		expectDisableParallel         bool
+		expectToolChoiceTypeInRequest string
+	}{
+		{
+			name:                          "no tool_choice defined defaults to auto",
+			toolChoice:                    nil,
+			expectDisableParallel:         true,
+			expectToolChoiceTypeInRequest: toolChoiceAuto,
+		},
+		{
+			name:                          "tool_choice auto",
+			toolChoice:                    map[string]any{"type": toolChoiceAuto},
+			expectDisableParallel:         true,
+			expectToolChoiceTypeInRequest: toolChoiceAuto,
+		},
+		{
+			name:                          "tool_choice any",
+			toolChoice:                    map[string]any{"type": toolChoiceAny},
+			expectDisableParallel:         true,
+			expectToolChoiceTypeInRequest: toolChoiceAny,
+		},
+		{
+			name:                          "tool_choice tool",
+			toolChoice:                    map[string]any{"type": toolChoiceTool, "name": "some_tool"},
+			expectDisableParallel:         true,
+			expectToolChoiceTypeInRequest: toolChoiceTool,
+		},
+		{
+			name:                          "tool_choice none",
+			toolChoice:                    map[string]any{"type": toolChoiceNone},
+			expectDisableParallel:         false,
+			expectToolChoiceTypeInRequest: toolChoiceNone,
+		},
+	}
+
+	for _, tc := range cases {
+		t.Run(tc.name, func(t *testing.T) {
+			t.Parallel()
+
+			ctx, cancel := context.WithTimeout(t.Context(), time.Second*30)
+			t.Cleanup(cancel)
+
+			// Configure the bridge.
+			mcpMgr := mcp.NewServerProxyManager(nil, testTracer)
+			require.NoError(t, mcpMgr.Init(ctx))
+
+			arc := txtar.Parse(antSimple)
+			files := filesMap(arc)
+			require.Contains(t, files, fixtureRequest)
+			require.Contains(t, files, fixtureNonStreamingResponse)
+
+			// Prepare request body with tool_choice set.
+			var reqJSON map[string]any
+			require.NoError(t, json.Unmarshal(files[fixtureRequest], &reqJSON))
+			if tc.toolChoice != nil {
+				reqJSON["tool_choice"] = tc.toolChoice
+			}
+			reqBody, err := json.Marshal(reqJSON)
+			require.NoError(t, err)
+
+			var receivedRequest map[string]any
+
+			// Create a mock server that captures the request body sent upstream.
+			mockSrv := httptest.NewUnstartedServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+				// Capture the raw request body.
+				raw, err := io.ReadAll(r.Body)
+				defer r.Body.Close()
+				require.NoError(t, err)
+
+				require.NoError(t, json.Unmarshal(raw, &receivedRequest))
+
+				// Return a valid API response.
+				w.Header().Set("Content-Type", "application/json")
+				w.WriteHeader(http.StatusOK)
+				_, _ = w.Write(files[fixtureNonStreamingResponse])
+			}))
+			mockSrv.Config.BaseContext = func(_ net.Listener) context.Context {
+				return ctx
+			}
+			mockSrv.Start()
+			t.Cleanup(mockSrv.Close)
+
+			recorder := &mockRecorderClient{}
+			logger := slogtest.Make(t, &slogtest.Options{IgnoreErrors: false}).Leveled(slog.LevelDebug)
+			providers := []aibridge.Provider{aibridge.NewAnthropicProvider(anthropicCfg(mockSrv.URL, apiKey), nil)}
+			bridge, err := aibridge.NewRequestBridge(ctx, providers, recorder, mcpMgr, logger, nil, testTracer)
+			require.NoError(t, err)
+
+			// Invoke request to mocked API via aibridge.
+			bridgeSrv := httptest.NewUnstartedServer(bridge)
+			bridgeSrv.Config.BaseContext = func(_ net.Listener) context.Context {
+				return aibridge.AsActor(ctx, userID, nil)
+			}
+			bridgeSrv.Start()
+			t.Cleanup(bridgeSrv.Close)
+
+			req := createAnthropicMessagesReq(t, bridgeSrv.URL, reqBody)
+			client := &http.Client{}
+			resp, err := client.Do(req)
+			require.NoError(t, err)
+			require.Equal(t, http.StatusOK, resp.StatusCode)
+			_ = resp.Body.Close()
+
+			// Verify tool_choice in the upstream request.
+			require.NotNil(t, receivedRequest)
+			toolChoice, ok := receivedRequest["tool_choice"].(map[string]any)
+			require.True(t, ok, "expected tool_choice in upstream request")
+
+			// Verify the type matches expectation.
+			assert.Equal(t, tc.expectToolChoiceTypeInRequest, toolChoice["type"])
+
+			// Verify name is preserved for tool_choice=tool.
+			if tc.expectToolChoiceTypeInRequest == toolChoiceTool {
+				assert.Equal(t, "some_tool", toolChoice["name"])
+			}
+
+			// Verify disable_parallel_tool_use based on expectations.
+			// See https://platform.claude.com/docs/en/agents-and-tools/tool-use/implement-tool-use#parallel-tool-use
+			disableParallel, hasDisableParallel := toolChoice["disable_parallel_tool_use"].(bool)
+
+			if tc.expectDisableParallel {
+				require.True(t, hasDisableParallel, "expected disable_parallel_tool_use in tool_choice")
+				assert.True(t, disableParallel, "expected disable_parallel_tool_use to be true")
+			} else {
+				assert.False(t, hasDisableParallel, "expected disable_parallel_tool_use to not be set")
+			}
+		})
+	}
+}
+
 func TestEnvironmentDoNotLeak(t *testing.T) {
 	// NOTE: Cannot use t.Parallel() here because subtests use t.Setenv which requires sequential execution.
 

intercept_anthropic_messages_base.go

@@ -12,6 +12,7 @@ import (
 	"github.com/anthropics/anthropic-sdk-go"
 	"github.com/anthropics/anthropic-sdk-go/bedrock"
 	"github.com/anthropics/anthropic-sdk-go/option"
+	"github.com/anthropics/anthropic-sdk-go/shared/constant"
 	"github.com/aws/aws-sdk-go-v2/config"
 	"github.com/aws/aws-sdk-go-v2/credentials"
 	"github.com/coder/aibridge/mcp"
@@ -96,11 +97,29 @@ func (i *AnthropicMessagesInterceptionBase) injectTools() {
 	}
 
 	// Note: Parallel tool calls are disabled to avoid tool_use/tool_result block mismatches.
-	i.req.ToolChoice = anthropic.ToolChoiceUnionParam{
-		OfAny: &anthropic.ToolChoiceAnyParam{
-			Type:                   "auto",
-			DisableParallelToolUse: anthropic.Bool(true),
-		},
+	// https://github.com/coder/aibridge/issues/2
+	toolChoiceType := i.req.ToolChoice.GetType()
+	var toolChoiceTypeStr string
+	if toolChoiceType != nil {
+		toolChoiceTypeStr = *toolChoiceType
+	}
+
+	switch toolChoiceTypeStr {
+	// If no tool_choice was defined, assume auto.
+	// See https://platform.claude.com/docs/en/agents-and-tools/tool-use/implement-tool-use#parallel-tool-use.
+	case "", string(constant.ValueOf[constant.Auto]()):
+		// We only set OfAuto if no tool_choice was provided (the default).
+		// "auto" is the default when a zero value is provided, so we can safely disable parallel checks on it.
+		if i.req.ToolChoice.OfAuto == nil {
+			i.req.ToolChoice.OfAuto = &anthropic.ToolChoiceAutoParam{}
+		}
+		i.req.ToolChoice.OfAuto.DisableParallelToolUse = anthropic.Bool(true)
+	case string(constant.ValueOf[constant.Any]()):
+		i.req.ToolChoice.OfAny.DisableParallelToolUse = anthropic.Bool(true)
+	case string(constant.ValueOf[constant.Tool]()):
+		i.req.ToolChoice.OfTool.DisableParallelToolUse = anthropic.Bool(true)
+	case string(constant.ValueOf[constant.None]()):
+		// No-op; if tool_choice=none then tools are not used at all.
 	}
 }