From 8ad6c0cc73fa0a5578b518e516046988f14ef3d0 Mon Sep 17 00:00:00 2001
From: bigcat88 <bigcat88@icloud.com>
Date: Fri, 20 Feb 2026 16:07:09 +0200
Subject: [PATCH] Add minLength/maxLength validation for String inputs

---
 comfy_api/latest/_io.py |  5 +++++
 execution.py            | 28 ++++++++++++++++++++++++++++
 2 files changed, 33 insertions(+)

diff --git a/comfy_api/latest/_io.py b/comfy_api/latest/_io.py
index 189d7d9bc..a4a85569b 100644
--- a/comfy_api/latest/_io.py
+++ b/comfy_api/latest/_io.py
@@ -326,11 +326,14 @@ class String(ComfyTypeIO):
         '''String input.'''
         def __init__(self, id: str, display_name: str=None, optional=False, tooltip: str=None, lazy: bool=None,
                     multiline=False, placeholder: str=None, default: str=None, dynamic_prompts: bool=None,
+                    min_length: int=None, max_length: int=None,
                     socketless: bool=None, force_input: bool=None, extra_dict=None, raw_link: bool=None, advanced: bool=None):
             super().__init__(id, display_name, optional, tooltip, lazy, default, socketless, None, force_input, extra_dict, raw_link, advanced)
             self.multiline = multiline
             self.placeholder = placeholder
             self.dynamic_prompts = dynamic_prompts
+            self.min_length = min_length
+            self.max_length = max_length
             self.default: str
 
         def as_dict(self):
@@ -338,6 +341,8 @@ class String(ComfyTypeIO):
                 "multiline": self.multiline,
                 "placeholder": self.placeholder,
                 "dynamicPrompts": self.dynamic_prompts,
+                "minLength": self.min_length,
+                "maxLength": self.max_length,
             })
 
 @comfytype(io_type="COMBO")
diff --git a/execution.py b/execution.py
index 75b021892..c0839be3d 100644
--- a/execution.py
+++ b/execution.py
@@ -938,6 +938,34 @@ async def validate_inputs(prompt_id, prompt, item, validated):
                     errors.append(error)
                     continue
 
+                if input_type == "STRING":
+                    if "minLength" in extra_info and len(val.strip()) < extra_info["minLength"]:
+                        error = {
+                            "type": "value_shorter_than_min_length",
+                            "message": "Value length {} shorter than min length of {}".format(len(val.strip()), extra_info["minLength"]),
+                            "details": f"{x}",
+                            "extra_info": {
+                                "input_name": x,
+                                "input_config": info,
+                                "received_value": val,
+                            }
+                        }
+                        errors.append(error)
+                        continue
+                    if "maxLength" in extra_info and len(val) > extra_info["maxLength"]:
+                        error = {
+                            "type": "value_longer_than_max_length",
+                            "message": "Value length {} longer than max length of {}".format(len(val), extra_info["maxLength"]),
+                            "details": f"{x}",
+                            "extra_info": {
+                                "input_name": x,
+                                "input_config": info,
+                                "received_value": val,
+                            }
+                        }
+                        errors.append(error)
+                        continue
+
                 if isinstance(input_type, list) or input_type == io.Combo.io_type:
                     if input_type == io.Combo.io_type:
                         combo_options = extra_info.get("options", [])