diff --git a/internal/translator/gemini-cli/claude/gemini-cli_claude_request.go b/internal/translator/gemini-cli/claude/gemini-cli_claude_request.go
index 93dbf1e8..29814cf0 100644
--- a/internal/translator/gemini-cli/claude/gemini-cli_claude_request.go
+++ b/internal/translator/gemini-cli/claude/gemini-cli_claude_request.go
@@ -136,8 +136,14 @@ func ConvertClaudeRequestToCLI(modelName string, inputRawJSON []byte, _ bool) []
 			inputSchemaResult := toolResult.Get("input_schema")
 			if inputSchemaResult.Exists() && inputSchemaResult.IsObject() {
 				inputSchema := inputSchemaResult.Raw
-				inputSchema, _ = sjson.Delete(inputSchema, "additionalProperties")
-				inputSchema, _ = sjson.Delete(inputSchema, "$schema")
+				// Use comprehensive schema sanitization for Gemini API compatibility
+				if sanitizedSchema, sanitizeErr := util.SanitizeSchemaForGemini(inputSchema); sanitizeErr == nil {
+					inputSchema = sanitizedSchema
+				} else {
+					// Fallback to basic cleanup if sanitization fails
+					inputSchema, _ = sjson.Delete(inputSchema, "additionalProperties")
+					inputSchema, _ = sjson.Delete(inputSchema, "$schema")
+				}
 				tool, _ := sjson.Delete(toolResult.Raw, "input_schema")
 				tool, _ = sjson.SetRaw(tool, "parameters", inputSchema)
 				var toolDeclaration any
diff --git a/internal/translator/gemini/claude/gemini_claude_request.go b/internal/translator/gemini/claude/gemini_claude_request.go
index 45ab0bef..43e01b1f 100644
--- a/internal/translator/gemini/claude/gemini_claude_request.go
+++ b/internal/translator/gemini/claude/gemini_claude_request.go
@@ -129,8 +129,14 @@ func ConvertClaudeRequestToGemini(modelName string, inputRawJSON []byte, _ bool)
 			inputSchemaResult := toolResult.Get("input_schema")
 			if inputSchemaResult.Exists() && inputSchemaResult.IsObject() {
 				inputSchema := inputSchemaResult.Raw
-				inputSchema, _ = sjson.Delete(inputSchema, "additionalProperties")
-				inputSchema, _ = sjson.Delete(inputSchema, "$schema")
+				// Use comprehensive schema sanitization for Gemini API compatibility
+				if sanitizedSchema, sanitizeErr := util.SanitizeSchemaForGemini(inputSchema); sanitizeErr == nil {
+					inputSchema = sanitizedSchema
+				} else {
+					// Fallback to basic cleanup if sanitization fails
+					inputSchema, _ = sjson.Delete(inputSchema, "additionalProperties")
+					inputSchema, _ = sjson.Delete(inputSchema, "$schema")
+				}
 				tool, _ := sjson.Delete(toolResult.Raw, "input_schema")
 				tool, _ = sjson.SetRaw(tool, "parameters", inputSchema)
 				var toolDeclaration any
diff --git a/internal/util/translator.go b/internal/util/translator.go
index 40274aca..6744eab0 100644
--- a/internal/util/translator.go
+++ b/internal/util/translator.go
@@ -212,3 +212,160 @@ func FixJSON(input string) string {
 
 	return out.String()
 }
+
+// SanitizeSchemaForGemini removes JSON Schema fields that are incompatible with Gemini API
+// to prevent "Proto field is not repeating, cannot start list" errors.
+//
+// Parameters:
+//   - schemaJSON: The JSON schema string to sanitize
+//
+// Returns:
+//   - string: The sanitized schema string
+//   - error: An error if the operation fails
+//
+// This function removes the following incompatible fields:
+// - additionalProperties: Not supported in Gemini function declarations
+// - $schema: JSON Schema meta-schema identifier, not needed for API
+// - allOf/anyOf/oneOf: Union type constructs not supported
+// - exclusiveMinimum/exclusiveMaximum: Advanced validation constraints
+// - patternProperties: Advanced property pattern matching
+// - dependencies: Property dependencies not supported
+// - type arrays: Converts ["string", "null"] to just "string"
+func SanitizeSchemaForGemini(schemaJSON string) (string, error) {
+	// Remove top-level incompatible fields
+	fieldsToRemove := []string{
+		"additionalProperties",
+		"$schema",
+		"allOf",
+		"anyOf",
+		"oneOf",
+		"exclusiveMinimum",
+		"exclusiveMaximum",
+		"patternProperties",
+		"dependencies",
+	}
+
+	result := schemaJSON
+	var err error
+
+	for _, field := range fieldsToRemove {
+		result, err = sjson.Delete(result, field)
+		if err != nil {
+			continue // Continue even if deletion fails
+		}
+	}
+
+	// Handle type arrays by converting them to single types
+	result = sanitizeTypeFields(result)
+
+	// Recursively clean nested objects
+	result = cleanNestedSchemas(result)
+
+	return result, nil
+}
+
+// sanitizeTypeFields converts type arrays to single types for Gemini compatibility
+func sanitizeTypeFields(jsonStr string) string {
+	// Parse the JSON to find all "type" fields
+	parsed := gjson.Parse(jsonStr)
+	result := jsonStr
+
+	// Walk through all paths to find type fields
+	var typeFields []string
+	walkForTypeFields(parsed, "", &typeFields)
+
+	// Process each type field
+	for _, path := range typeFields {
+		typeValue := gjson.Get(result, path)
+		if typeValue.IsArray() {
+			// Convert array to single type (prioritize string, then others)
+			arr := typeValue.Array()
+			if len(arr) > 0 {
+				var preferredType string
+				for _, t := range arr {
+					typeStr := t.String()
+					if typeStr == "string" {
+						preferredType = "string"
+						break
+					} else if typeStr == "number" || typeStr == "integer" {
+						preferredType = typeStr
+						if preferredType == "" {
+							preferredType = typeStr
+						}
+					} else if preferredType == "" {
+						preferredType = typeStr
+					}
+				}
+				if preferredType != "" {
+					result, _ = sjson.Set(result, path, preferredType)
+				}
+			}
+		}
+	}
+
+	return result
+}
+
+// walkForTypeFields recursively finds all "type" field paths in the JSON
+func walkForTypeFields(value gjson.Result, path string, paths *[]string) {
+	switch value.Type {
+	case gjson.JSON:
+		value.ForEach(func(key, val gjson.Result) bool {
+			var childPath string
+			if path == "" {
+				childPath = key.String()
+			} else {
+				childPath = path + "." + key.String()
+			}
+			if key.String() == "type" {
+				*paths = append(*paths, childPath)
+			}
+			walkForTypeFields(val, childPath, paths)
+			return true
+		})
+	}
+}
+
+// cleanNestedSchemas recursively removes incompatible fields from nested schema objects
+func cleanNestedSchemas(jsonStr string) string {
+	fieldsToRemove := []string{"allOf", "anyOf", "oneOf", "exclusiveMinimum", "exclusiveMaximum"}
+
+	// Find all nested paths that might contain these fields
+	var pathsToClean []string
+	parsed := gjson.Parse(jsonStr)
+	findNestedSchemaPaths(parsed, "", fieldsToRemove, &pathsToClean)
+
+	result := jsonStr
+	// Remove fields from all found paths
+	for _, path := range pathsToClean {
+		result, _ = sjson.Delete(result, path)
+	}
+
+	return result
+}
+
+// findNestedSchemaPaths recursively finds paths containing incompatible schema fields
+func findNestedSchemaPaths(value gjson.Result, path string, fieldsToFind []string, paths *[]string) {
+	switch value.Type {
+	case gjson.JSON:
+		value.ForEach(func(key, val gjson.Result) bool {
+			var childPath string
+			if path == "" {
+				childPath = key.String()
+			} else {
+				childPath = path + "." + key.String()
+			}
+
+			// Check if this key is one we want to remove
+			for _, field := range fieldsToFind {
+				if key.String() == field {
+					*paths = append(*paths, childPath)
+					break
+				}
+			}
+
+			findNestedSchemaPaths(val, childPath, fieldsToFind, paths)
+			return true
+		})
+	}
+}