fix: thought signature handling in gemini chat completion tool call

core/providers/gemini/chat.go

@@ -118,15 +118,6 @@ func (response *GenerateContentResponse) ToBifrostChatResponse() *schemas.Bifros
 						Function: function,
 					}
 
-					if part.ThoughtSignature != nil {
-						thoughtSig := base64.StdEncoding.EncodeToString(part.ThoughtSignature)
-						toolCall.ExtraContent = map[string]interface{}{
-							"google": map[string]interface{}{
-								"thought_signature": thoughtSig,
-							},
-						}
-					}
-
 					toolCalls = append(toolCalls, toolCall)
 				}
 
@@ -144,11 +135,22 @@ func (response *GenerateContentResponse) ToBifrostChatResponse() *schemas.Bifros
 				}
 				if part.ThoughtSignature != nil {
 					thoughtSig := base64.StdEncoding.EncodeToString(part.ThoughtSignature)
-					reasoningDetails = append(reasoningDetails, schemas.ChatReasoningDetails{
+					reasoningDetail := schemas.ChatReasoningDetails{
 						Index:     len(reasoningDetails),
 						Type:      schemas.BifrostReasoningDetailsTypeEncrypted,
 						Signature: &thoughtSig,
-					})
+					}
+
+					// check if part is tool call
+					if part.FunctionCall != nil {
+						callID := part.FunctionCall.Name
+						if part.FunctionCall.ID != "" {
+							callID = part.FunctionCall.ID
+						}
+						reasoningDetail.ID = schemas.Ptr(fmt.Sprintf("tool_call_%s", callID))
+					}
+
+					reasoningDetails = append(reasoningDetails, reasoningDetail)
 				}
 			}
 

core/providers/gemini/utils.go

@@ -2,6 +2,7 @@ package gemini
 
 import (
 	"encoding/base64"
+	"fmt"
 	"strings"
 
 	"github.com/bytedance/sonic"
@@ -607,15 +608,19 @@ func convertBifrostMessagesToGemini(messages []schemas.ChatMessage) []Content {
 						},
 					}
 
-					// Preserve thought signature from extra_content (required for Gemini 3 Pro)
-					if toolCall.ExtraContent != nil {
-						if googleData, ok := toolCall.ExtraContent["google"].(map[string]interface{}); ok {
-							if thoughtSig, ok := googleData["thought_signature"].(string); ok {
+					// check in reasoning details array for thought signature with id tool_call_<callID>
+					if len(message.ChatAssistantMessage.ReasoningDetails) > 0 {
+						lookupID := fmt.Sprintf("tool_call_%s", callID)
+						for _, reasoningDetail := range message.ChatAssistantMessage.ReasoningDetails {
+							if reasoningDetail.ID != nil && *reasoningDetail.ID == lookupID &&
+								reasoningDetail.Type == schemas.BifrostReasoningDetailsTypeEncrypted &&
+								reasoningDetail.Signature != nil {
 								// Decode the base64 string to raw bytes
-								decoded, err := base64.StdEncoding.DecodeString(thoughtSig)
+								decoded, err := base64.StdEncoding.DecodeString(*reasoningDetail.Signature)
 								if err == nil {
 									part.ThoughtSignature = decoded
 								}
+								break
 							}
 						}
 					}

core/schemas/chatcompletions.go

@@ -717,11 +717,10 @@ type ChatAssistantMessageAnnotationCitation struct {
 
 // ChatAssistantMessageToolCall represents a tool call in a message
 type ChatAssistantMessageToolCall struct {
-	Index        uint16                               `json:"index"`
-	Type         *string                              `json:"type,omitempty"`
-	ID           *string                              `json:"id,omitempty"`
-	Function     ChatAssistantMessageToolCallFunction `json:"function"`
-	ExtraContent map[string]interface{}               `json:"extra_content,omitempty"` // Provider-specific fields (e.g., thought_signature for Gemini)
+	Index    uint16                               `json:"index"`
+	Type     *string                              `json:"type,omitempty"`
+	ID       *string                              `json:"id,omitempty"`
+	Function ChatAssistantMessageToolCallFunction `json:"function"`
 }
 
 // ChatAssistantMessageToolCallFunction represents a call to a function.
@@ -762,6 +761,7 @@ const (
 
 // Not in OpenAI's spec, but needed to support inter provider reasoning capabilities.
 type ChatReasoningDetails struct {
+	ID        *string                     `json:"id,omitempty"`
 	Index     int                         `json:"index"`
 	Type      BifrostReasoningDetailsType `json:"type"`
 	Summary   *string                     `json:"summary,omitempty"`