diff --git a/.gitignore b/.gitignore
index 2eb4f17..3ac9816 100644
--- a/.gitignore
+++ b/.gitignore
@@ -13,6 +13,7 @@ tools.db
 .mytools_db
 .idea/MyManagingTools.iml
 .idea/misc.xml
+.idea_bak
 **/*.prof
 
 # Created by .ignore support plugin (hsz.mobi)
diff --git a/.idea/.gitignore b/.idea/.gitignore
deleted file mode 100644
index 26d3352..0000000
--- a/.idea/.gitignore
+++ /dev/null
@@ -1,3 +0,0 @@
-# Default ignored files
-/shelf/
-/workspace.xml
diff --git a/src/components/jsonviewer/Readme.md b/src/components/jsonviewer/Readme.md
index 720fcc6..91642a0 100644
--- a/src/components/jsonviewer/Readme.md
+++ b/src/components/jsonviewer/Readme.md
@@ -224,7 +224,13 @@ editable_hook = (HookBuilder()
 ```
 
 ### `when_custom(condition)`
-Use custom condition objects for complex logic.
+Use custom condition objects or callable predicates for complex logic.
+
+The `when_custom()` method accepts either:
+- **Condition instances**: Objects that inherit from the `Condition` base class
+- **Callable predicates**: Functions that take a `HookContext` parameter and return a boolean
+
+When a callable is provided, it's automatically wrapped in a `PredicateCondition` class internally.
 
 ```python
 class BusinessLogicCondition(Condition):
diff --git a/tests/test_hooks.py b/tests/test_hooks.py
index 3936085..83d0ce6 100644
--- a/tests/test_hooks.py
+++ b/tests/test_hooks.py
@@ -1,7 +1,7 @@
 import pytest
 
 from components.jsonviewer.hooks import (
-  HookContext, EventType, Hook, HookManager,
+  HookContext, EventType, Hook, HookManager, HookBuilder,
   WhenLongText, WhenEditable, WhenType, WhenKey, WhenPath, WhenValue,
   CompositeCondition
 )
@@ -157,3 +157,72 @@ def test_i_can_clear_hooks_in_manager():
   
   hook_manager.clear_hooks()
   assert len(hook_manager.hooks) == 0
+
+
+# ================
+# Test HookBuilder with Callable Conditions
+# ================
+
+def test_i_can_use_callable_with_when_custom():
+  """Test that when_custom() accepts callable predicates"""
+  
+  # Define a simple callable condition
+  def custom_condition(context):
+    return isinstance(context.get_value(), str) and context.get_value().startswith("CUSTOM_")
+  
+  # Create hook using callable condition
+  hook = (HookBuilder()
+          .on_render()
+          .when_custom(custom_condition)
+          .execute(lambda ctx: "Custom hook executed"))
+  
+  # Test with matching context
+  matching_context = create_mock_context(value="CUSTOM_test_value")
+  assert hook.matches(EventType.RENDER, matching_context) == True
+  assert hook.execute(matching_context) == "Custom hook executed"
+  
+  # Test with non-matching context
+  non_matching_context = create_mock_context(value="regular_value")
+  assert hook.matches(EventType.RENDER, non_matching_context) == False
+
+
+def test_i_can_use_lambda_with_when_custom():
+  """Test that when_custom() accepts lambda expressions"""
+  
+  # Create hook using lambda condition
+  hook = (HookBuilder()
+          .on_render()
+          .when_custom(lambda ctx: ctx.key == "special" and isinstance(ctx.get_value(), int) and ctx.get_value() > 100)
+          .execute(lambda ctx: f"Special value: {ctx.get_value()}"))
+  
+  # Test with matching context
+  matching_context = create_mock_context(value=150, key="special")
+  assert hook.matches(EventType.RENDER, matching_context) == True
+  assert hook.execute(matching_context) == "Special value: 150"
+  
+  # Test with non-matching contexts
+  wrong_key_context = create_mock_context(value=150, key="normal")
+  assert hook.matches(EventType.RENDER, wrong_key_context) == False
+  
+  wrong_value_context = create_mock_context(value=50, key="special")
+  assert hook.matches(EventType.RENDER, wrong_value_context) == False
+
+
+@pytest.mark.parametrize("value, key, json_path, expected", [
+    ("CUSTOM_hook_test", "test_key", "root.test", True),  # Matches callable condition
+    ("regular_text", "test_key", "root.test", False),     # Doesn't match callable condition
+    (123, "test_key", "root.test", False),                # Wrong type
+])
+def test_callable_condition_evaluation(value, key, json_path, expected):
+  """Test callable condition evaluation with different inputs"""
+  
+  def custom_callable_condition(context):
+    return isinstance(context.get_value(), str) and context.get_value().startswith("CUSTOM_")
+  
+  hook = (HookBuilder()
+          .on_render()
+          .when_custom(custom_callable_condition)
+          .execute(lambda ctx: "Executed"))
+  
+  context = create_mock_context(value=value, key=key, json_path=json_path)
+  assert hook.matches(EventType.RENDER, context) == expected