fix(openai): strip internal metadata from OAuth input items

backend/internal/service/openai_gateway_request_body.go

@@ -1062,6 +1062,19 @@ func normalizeOpenAIOAuthResponsesCompatibilityFields(reqBody map[string]any) bo
 		delete(reqBody, "commands")
 		changed = true
 	}
+	// Codex can attach internal message metadata when a custom provider is
+	// named OpenAI. ChatGPT rejects this field on input items (#7066).
+	input, _ := reqBody["input"].([]any)
+	for _, value := range input {
+		item, ok := value.(map[string]any)
+		if !ok {
+			continue
+		}
+		if _, exists := item["internal_chat_message_metadata_passthrough"]; exists {
+			delete(item, "internal_chat_message_metadata_passthrough")
+			changed = true
+		}
+	}
 	return changed
 }
 
@@ -1096,6 +1109,22 @@ func normalizeOpenAIOAuthResponsesCompatibilityBody(body []byte) ([]byte, bool,
 		normalized = next
 		changed = true
 	}
+	// Only remove the input-item field, never same-named user content.
+	input := gjson.GetBytes(normalized, "input")
+	if !input.IsArray() {
+		return normalized, changed, nil
+	}
+	for i, item := range input.Array() {
+		if !item.IsObject() || !item.Get("internal_chat_message_metadata_passthrough").Exists() {
+			continue
+		}
+		next, err := sjson.DeleteBytes(normalized, fmt.Sprintf("input.%d.internal_chat_message_metadata_passthrough", i))
+		if err != nil {
+			return body, false, fmt.Errorf("normalize oauth input metadata: %w", err)
+		}
+		normalized = next
+		changed = true
+	}
 	return normalized, changed, nil
 }
 

backend/internal/service/openai_oauth_input_metadata_test.go

@@ -0,0 +1,82 @@
+package service
+
+import (
+	"encoding/json"
+	"testing"
+
+	"github.com/stretchr/testify/require"
+	"github.com/tidwall/gjson"
+)
+
+func TestOAuthInputInternalMetadata(t *testing.T) {
+	const field = "internal_chat_message_metadata_passthrough"
+	// The identically named field in user content must not be recursively stripped.
+	const body = `{"model":"gpt-5.5","input":[{"role":"user","content":[{"type":"input_text","text":"hello","internal_chat_message_metadata_passthrough":{"keep":true}}],"internal_chat_message_metadata_passthrough":{"content_item_kinds":["text"]}},{"type":"function_call","call_id":"fc_123","name":"echo","arguments":"{\"internal_chat_message_metadata_passthrough\":true}","internal_chat_message_metadata_passthrough":null},{"type":"function_call_output","call_id":"fc_123","output":"result"}],"internal_chat_message_metadata_passthrough":{"keep":true}}`
+	tests := []struct {
+		name      string
+		normalize func([]byte) ([]byte, bool, error)
+		strip     bool
+	}{
+		{"transformed OAuth", func(b []byte) ([]byte, bool, error) {
+			var req map[string]any
+			if err := json.Unmarshal(b, &req); err != nil {
+				return nil, false, err
+			}
+			result := applyCodexOAuthTransform(req, false, false)
+			out, err := json.Marshal(req)
+			return out, result.Modified, err
+		}, true},
+		{"OAuth passthrough", func(b []byte) ([]byte, bool, error) { return normalizeOpenAIPassthroughOAuthBody(b, false) }, true},
+		{"OAuth compact", func(b []byte) ([]byte, bool, error) { return normalizeOpenAIPassthroughOAuthBody(b, true) }, true},
+		{"OAuth websocket", func(b []byte) ([]byte, bool, error) {
+			return normalizeOpenAIResponsesWebSocketCompatibilityBody(b, &Account{Platform: PlatformOpenAI, Type: AccountTypeOAuth}, false)
+		}, true},
+		{"API key websocket", func(b []byte) ([]byte, bool, error) {
+			return normalizeOpenAIResponsesWebSocketCompatibilityBody(b, &Account{Platform: PlatformOpenAI, Type: AccountTypeAPIKey}, false)
+		}, false},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			out, _, err := tt.normalize([]byte(body))
+			require.NoError(t, err)
+			require.Equal(t, !tt.strip, gjson.GetBytes(out, "input.0."+field).Exists())
+			require.Equal(t, !tt.strip, gjson.GetBytes(out, "input.1."+field).Exists())
+			require.Equal(t, "hello", gjson.GetBytes(out, "input.0.content.0.text").String())
+			require.True(t, gjson.GetBytes(out, "input.0.content.0."+field+".keep").Bool())
+			require.True(t, gjson.GetBytes(out, field+".keep").Bool())
+			require.Equal(t, `{"internal_chat_message_metadata_passthrough":true}`, gjson.GetBytes(out, "input.1.arguments").String())
+			require.Equal(t, "fc_123", gjson.GetBytes(out, "input.1.call_id").String())
+			require.Equal(t, "result", gjson.GetBytes(out, "input.2.output").String())
+		})
+	}
+}
+
+func TestOAuthInputInternalMetadataCompatibility(t *testing.T) {
+	for _, body := range []string{
+		`{"input":"hello"}`,
+		`{"input":{"internal_chat_message_metadata_passthrough":true}}`,
+		`{"input":[null,"hello",{"role":"user","content":"hello"}]}`,
+		`{"input":[{"content":{"internal_chat_message_metadata_passthrough":true}}]}`,
+	} {
+		t.Run(body, func(t *testing.T) {
+			out, changed, err := normalizeOpenAIOAuthResponsesCompatibilityBody([]byte(body))
+			require.NoError(t, err)
+			require.False(t, changed)
+			require.Equal(t, body, string(out))
+			var req map[string]any
+			require.NoError(t, json.Unmarshal([]byte(body), &req))
+			require.False(t, normalizeOpenAIOAuthResponsesCompatibilityFields(req))
+		})
+	}
+	// Legacy prompt aliases and later-turn payloads use the same boundary.
+	body := []byte(`{"prompt":[{"role":"user","content":"hello","internal_chat_message_metadata_passthrough":{}}],"previous_response_id":"resp_123"}`)
+	out, changed, err := normalizeOpenAIOAuthResponsesCompatibilityBody(body)
+	require.NoError(t, err)
+	require.True(t, changed)
+	require.False(t, gjson.GetBytes(out, "input.0.internal_chat_message_metadata_passthrough").Exists())
+	require.Equal(t, "resp_123", gjson.GetBytes(out, "previous_response_id").String())
+	var req map[string]any
+	require.NoError(t, json.Unmarshal(body, &req))
+	require.True(t, normalizeOpenAIOAuthResponsesCompatibilityFields(req))
+	require.NotContains(t, req["input"].([]any)[0], "internal_chat_message_metadata_passthrough")
+}