From edfd5e3736128b05f65108a5c2c83271b9a1f891 Mon Sep 17 00:00:00 2001
From: wucm667 <stevenwucongmin@gmail.com>
Date: Fri, 12 Jun 2026 15:01:58 +0800
Subject: [PATCH] fix(apicompat): default tool strict to false

---
 .../chatcompletions_responses_test.go         | 85 +++++++++++++++++++
 .../apicompat/chatcompletions_to_responses.go | 12 ++-
 2 files changed, 95 insertions(+), 2 deletions(-)

diff --git a/backend/internal/pkg/apicompat/chatcompletions_responses_test.go b/backend/internal/pkg/apicompat/chatcompletions_responses_test.go
index c12715e112..795a73938e 100644
--- a/backend/internal/pkg/apicompat/chatcompletions_responses_test.go
+++ b/backend/internal/pkg/apicompat/chatcompletions_responses_test.go
@@ -113,6 +113,91 @@ func TestChatCompletionsToResponses_ToolCalls(t *testing.T) {
 	assert.Equal(t, "ping", resp.Tools[0].Name)
 }
 
+func TestChatCompletionsToResponses_ToolStrict(t *testing.T) {
+	strictTrue := true
+	strictFalse := false
+	tests := []struct {
+		name   string
+		strict *bool
+		want   bool
+	}{
+		{name: "defaults omitted strict to false", want: false},
+		{name: "preserves explicit true", strict: &strictTrue, want: true},
+		{name: "preserves explicit false", strict: &strictFalse, want: false},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			req := &ChatCompletionsRequest{
+				Model:    "gpt-4o",
+				Messages: []ChatMessage{{Role: "user", Content: json.RawMessage(`"Hi"`)}},
+				Tools: []ChatTool{{
+					Type: "function",
+					Function: &ChatFunction{
+						Name:   "lookup",
+						Strict: tt.strict,
+					},
+				}},
+			}
+
+			resp, err := ChatCompletionsToResponses(req)
+			require.NoError(t, err)
+			require.Len(t, resp.Tools, 1)
+			require.NotNil(t, resp.Tools[0].Strict)
+			assert.Equal(t, tt.want, *resp.Tools[0].Strict)
+
+			payload, err := json.Marshal(resp)
+			require.NoError(t, err)
+
+			var serialized struct {
+				Tools []map[string]json.RawMessage `json:"tools"`
+			}
+			require.NoError(t, json.Unmarshal(payload, &serialized))
+			require.Len(t, serialized.Tools, 1)
+			strictJSON, ok := serialized.Tools[0]["strict"]
+			require.True(t, ok, "strict must be present in the Responses payload")
+			assert.JSONEq(t, string(mustMarshalJSON(t, tt.want)), string(strictJSON))
+		})
+	}
+}
+
+func TestChatCompletionsToResponses_LegacyFunctionDefaultsStrictFalse(t *testing.T) {
+	req := &ChatCompletionsRequest{
+		Model:    "gpt-4o",
+		Messages: []ChatMessage{{Role: "user", Content: json.RawMessage(`"Hi"`)}},
+		Functions: []ChatFunction{{
+			Name: "lookup",
+		}},
+	}
+
+	resp, err := ChatCompletionsToResponses(req)
+	require.NoError(t, err)
+	require.Len(t, resp.Tools, 1)
+	require.NotNil(t, resp.Tools[0].Strict)
+	assert.False(t, *resp.Tools[0].Strict)
+
+	payload, err := json.Marshal(resp)
+	require.NoError(t, err)
+	assert.Contains(t, string(payload), `"strict":false`)
+}
+
+func TestResponsesTool_StrictFalseIsSerialized(t *testing.T) {
+	strict := false
+	payload, err := json.Marshal(ResponsesTool{
+		Type:   "function",
+		Strict: &strict,
+	})
+	require.NoError(t, err)
+	assert.JSONEq(t, `{"type":"function","strict":false}`, string(payload))
+}
+
+func mustMarshalJSON(t *testing.T, value any) []byte {
+	t.Helper()
+	data, err := json.Marshal(value)
+	require.NoError(t, err)
+	return data
+}
+
 func TestChatCompletionsToResponses_MaxTokens(t *testing.T) {
 	t.Run("max_tokens", func(t *testing.T) {
 		maxTokens := 100
diff --git a/backend/internal/pkg/apicompat/chatcompletions_to_responses.go b/backend/internal/pkg/apicompat/chatcompletions_to_responses.go
index 463bdd0d15..7cbb4f5f20 100644
--- a/backend/internal/pkg/apicompat/chatcompletions_to_responses.go
+++ b/backend/internal/pkg/apicompat/chatcompletions_to_responses.go
@@ -419,7 +419,7 @@ func convertChatToolsToResponses(tools []ChatTool, functions []ChatFunction) []R
 			Name:        t.Function.Name,
 			Description: t.Function.Description,
 			Parameters:  t.Function.Parameters,
-			Strict:      t.Function.Strict,
+			Strict:      defaultStrictFalse(t.Function.Strict),
 		}
 		out = append(out, rt)
 	}
@@ -431,7 +431,7 @@ func convertChatToolsToResponses(tools []ChatTool, functions []ChatFunction) []R
 			Name:        f.Name,
 			Description: f.Description,
 			Parameters:  f.Parameters,
-			Strict:      f.Strict,
+			Strict:      defaultStrictFalse(f.Strict),
 		}
 		out = append(out, rt)
 	}
@@ -439,6 +439,14 @@ func convertChatToolsToResponses(tools []ChatTool, functions []ChatFunction) []R
 	return out
 }
 
+func defaultStrictFalse(src *bool) *bool {
+	if src == nil {
+		value := false
+		return &value
+	}
+	return src
+}
+
 // convertChatFunctionCallToToolChoice maps the legacy function_call field to a
 // Responses API tool_choice value.
 //