fix(translators): handle string system instructions in Claude translators

Updated Antigravity, Gemini, and Gemini-CLI translators to process `systemResult` of type `string` for system instructions. Ensures properly formatted JSON with dynamic content assignment.

internal/translator/antigravity/claude/antigravity_claude_request.go

@@ -86,6 +86,10 @@ func ConvertClaudeRequestToAntigravity(modelName string, inputRawJSON []byte, _
 				hasSystemInstruction = true
 			}
 		}
+	} else if systemResult.Type == gjson.String {
+		systemInstructionJSON = `{"role":"user","parts":[{"text":""}]}`
+		systemInstructionJSON, _ = sjson.Set(systemInstructionJSON, "parts.0.text", systemResult.String())
+		hasSystemInstruction = true
 	}
 
 	// contents
@@ -147,7 +151,6 @@ func ConvertClaudeRequestToAntigravity(modelName string, inputRawJSON []byte, _
 							currentMessageThinkingSignature = signature
 						}
 
-
 						// Skip trailing unsigned thinking blocks on last assistant message
 						isUnsigned := !cache.HasValidSignature(signature)
 
@@ -321,6 +324,7 @@ func ConvertClaudeRequestToAntigravity(modelName string, inputRawJSON []byte, _
 	// tools
 	toolsJSON := ""
 	toolDeclCount := 0
+	allowedToolKeys := []string{"name", "description", "behavior", "parameters", "parametersJsonSchema", "response", "responseJsonSchema"}
 	toolsResult := gjson.GetBytes(rawJSON, "tools")
 	if toolsResult.IsArray() {
 		toolsJSON = `[{"functionDeclarations":[]}]`
@@ -333,10 +337,12 @@ func ConvertClaudeRequestToAntigravity(modelName string, inputRawJSON []byte, _
 				inputSchema := util.CleanJSONSchemaForAntigravity(inputSchemaResult.Raw)
 				tool, _ := sjson.Delete(toolResult.Raw, "input_schema")
 				tool, _ = sjson.SetRaw(tool, "parametersJsonSchema", inputSchema)
-				tool, _ = sjson.Delete(tool, "strict")
-				tool, _ = sjson.Delete(tool, "input_examples")
-				tool, _ = sjson.Delete(tool, "type")
-				tool, _ = sjson.Delete(tool, "cache_control")
+				for toolKey := range gjson.Parse(tool).Map() {
+					if util.InArray(allowedToolKeys, toolKey) {
+						continue
+					}
+					tool, _ = sjson.Delete(tool, toolKey)
+				}
 				toolsJSON, _ = sjson.SetRaw(toolsJSON, "0.functionDeclarations.-1", tool)
 				toolDeclCount++
 			}

internal/translator/antigravity/openai/chat-completions/antigravity_openai_request.go

@@ -266,7 +266,11 @@ func ConvertOpenAIRequestToAntigravity(modelName string, inputRawJSON []byte, _
 						fargs := tc.Get("function.arguments").String()
 						node, _ = sjson.SetBytes(node, "parts."+itoa(p)+".functionCall.id", fid)
 						node, _ = sjson.SetBytes(node, "parts."+itoa(p)+".functionCall.name", fname)
+						if gjson.Valid(fargs) {
 							node, _ = sjson.SetRawBytes(node, "parts."+itoa(p)+".functionCall.args", []byte(fargs))
+						} else {
+							node, _ = sjson.SetBytes(node, "parts."+itoa(p)+".functionCall.args.params", []byte(fargs))
+						}
 						node, _ = sjson.SetBytes(node, "parts."+itoa(p)+".thoughtSignature", geminiCLIFunctionThoughtSignature)
 						p++
 						if fid != "" {

internal/translator/gemini-cli/claude/gemini-cli_claude_request.go

@@ -62,6 +62,8 @@ func ConvertClaudeRequestToCLI(modelName string, inputRawJSON []byte, _ bool) []
 		if hasSystemParts {
 			out, _ = sjson.SetRaw(out, "request.systemInstruction", systemInstruction)
 		}
+	} else if systemResult.Type == gjson.String {
+		out, _ = sjson.Set(out, "request.systemInstruction.parts.-1.text", systemResult.String())
 	}
 
 	// contents

internal/translator/gemini/claude/gemini_claude_request.go

@@ -55,6 +55,8 @@ func ConvertClaudeRequestToGemini(modelName string, inputRawJSON []byte, _ bool)
 		if hasSystemParts {
 			out, _ = sjson.SetRaw(out, "system_instruction", systemInstruction)
 		}
+	} else if systemResult.Type == gjson.String {
+		out, _ = sjson.Set(out, "request.system_instruction.parts.-1.text", systemResult.String())
 	}
 
 	// contents