diff --git a/src/google/adk/cli/cli.py b/src/google/adk/cli/cli.py
index 941f1c28c7..d4673459f7 100644
--- a/src/google/adk/cli/cli.py
+++ b/src/google/adk/cli/cli.py
@@ -15,13 +15,18 @@
 from __future__ import annotations
 
 from datetime import datetime
+import os
 from pathlib import Path
+import threading
 from typing import Optional
 from typing import Union
 
 import click
 from google.genai import types
 from pydantic import BaseModel
+from watchdog.events import FileSystemEvent
+from watchdog.events import FileSystemEventHandler
+from watchdog.observers import Observer
 
 from ..agents.llm_agent import LlmAgent
 from ..apps.app import App
@@ -45,6 +50,35 @@ class InputFile(BaseModel):
   queries: list[str]
 
 
+class DevModeChangeHandler(FileSystemEventHandler):
+  """Handles file system events for development mode auto-reload."""
+
+  def __init__(self):
+    self.reload_needed = threading.Event()
+    self.last_modified_file = None
+
+  def _handle_event(self, event: FileSystemEvent):
+    """Handle file system events for .py and .yaml files."""
+    if event.is_directory:
+      return
+    if event.src_path.endswith(('.py', '.yaml')):
+      self.last_modified_file = event.src_path
+      self.reload_needed.set()
+
+  def on_modified(self, event: FileSystemEvent):
+    self._handle_event(event)
+
+  def on_created(self, event: FileSystemEvent):
+    self._handle_event(event)
+
+  def check_and_reset(self) -> tuple[bool, Optional[str]]:
+    """Check if reload is needed and reset the flag."""
+    if self.reload_needed.is_set():
+      self.reload_needed.clear()
+      return True, self.last_modified_file
+    return False, None
+
+
 async def run_input_file(
     app_name: str,
     user_id: str,
@@ -93,6 +127,9 @@ async def run_interactively(
     session: Session,
     session_service: BaseSessionService,
     credential_service: BaseCredentialService,
+    agent_loader: Optional[AgentLoader] = None,
+    agent_folder_name: Optional[str] = None,
+    change_handler: Optional[DevModeChangeHandler] = None,
 ) -> None:
   app = (
       root_agent_or_app
@@ -105,7 +142,44 @@ async def run_interactively(
       session_service=session_service,
       credential_service=credential_service,
   )
+
+  current_agent_or_app = root_agent_or_app
+
   while True:
+    # Check if we need to reload the agent in dev mode
+    if change_handler and agent_loader and agent_folder_name:
+      needs_reload, changed_file = change_handler.check_and_reset()
+      if needs_reload:
+        try:
+          click.secho(
+              f'\nDetected change in {changed_file}',
+              fg='yellow',
+          )
+          click.secho('Reloading agent...', fg='yellow')
+          # Remove from cache and reload
+          agent_loader.remove_agent_from_cache(agent_folder_name)
+          current_agent_or_app = agent_loader.load_agent(agent_folder_name)
+
+          # Update the app and runner with the new agent
+          app = (
+              current_agent_or_app
+              if isinstance(current_agent_or_app, App)
+              else App(name=session.app_name, root_agent=current_agent_or_app)
+          )
+          await runner.close()
+          runner = Runner(
+              app=app,
+              artifact_service=artifact_service,
+              session_service=session_service,
+              credential_service=credential_service,
+          )
+          click.secho('Agent reloaded successfully!\n', fg='green')
+        except Exception as e:
+          click.secho(
+              f'Error reloading agent: {e}\n',
+              fg='red',
+          )
+
     query = input('[user]: ')
     if not query or not query.strip():
       continue
@@ -135,6 +209,7 @@ async def run_cli(
     saved_session_file: Optional[str] = None,
     save_session: bool,
     session_id: Optional[str] = None,
+    dev_mode: bool = False,
     session_service_uri: Optional[str] = None,
     artifact_service_uri: Optional[str] = None,
 ) -> None:
@@ -151,6 +226,7 @@ async def run_cli(
       contains a previously saved session, exclusive with input_file.
     save_session: bool, whether to save the session on exit.
     session_id: Optional[str], the session ID to save the session to on exit.
+    dev_mode: bool, whether to enable development mode with auto-reload.
     session_service_uri: Optional[str], custom session service URI.
     artifact_service_uri: Optional[str], custom artifact service URI.
   """
@@ -183,6 +259,13 @@ async def run_cli(
   )
 
   credential_service = InMemoryCredentialService()
+  agents_dir = str(agent_parent_path)
+  agent_loader = AgentLoader(agents_dir=agents_dir)
+  agent_or_app = agent_loader.load_agent(agent_folder_name)
+
+  session_app_name = (
+      agent_or_app.name if isinstance(agent_or_app, App) else agent_folder_name
+  )
   if not is_env_enabled('ADK_DISABLE_LOAD_DOTENV'):
     envs.load_dotenv_for_agent(agent_folder_name, agents_dir)
 
@@ -197,53 +280,79 @@ def _print_event(event) -> None:
     author = event.author or 'system'
     click.echo(f'[{author}]: {"".join(text_parts)}')
 
-  if input_file:
-    session = await run_input_file(
-        app_name=session_app_name,
-        user_id=user_id,
-        agent_or_app=agent_or_app,
-        artifact_service=artifact_service,
-        session_service=session_service,
-        credential_service=credential_service,
-        input_path=input_file,
-    )
-  elif saved_session_file:
-    # Load the saved session from file
-    with open(saved_session_file, 'r', encoding='utf-8') as f:
-      loaded_session = Session.model_validate_json(f.read())
-
-    # Create a new session in the service, copying state from the file
-    session = await session_service.create_session(
-        app_name=session_app_name,
-        user_id=user_id,
-        state=loaded_session.state if loaded_session else None,
+  # Set up watchdog observer for dev mode
+  observer: Optional[Observer] = None
+  change_handler: Optional[DevModeChangeHandler] = None
+  if dev_mode:
+    agent_path = os.path.join(agent_parent_dir, agent_folder_name)
+    change_handler = DevModeChangeHandler()
+    observer = Observer()
+    observer.schedule(change_handler, agent_path, recursive=True)
+    observer.start()
+    click.secho(
+        'Auto-reload enabled - watching for file changes...',
+        fg='green',
     )
 
-    # Append events from the file to the new session and display them
-    if loaded_session:
-      for event in loaded_session.events:
-        await session_service.append_event(session, event)
-        _print_event(event)
-
-    await run_interactively(
-        agent_or_app,
-        artifact_service,
-        session,
-        session_service,
-        credential_service,
-    )
-  else:
-    session = await session_service.create_session(
-        app_name=session_app_name, user_id=user_id
-    )
-    click.echo(f'Running agent {agent_or_app.name}, type exit to exit.')
-    await run_interactively(
-        agent_or_app,
-        artifact_service,
-        session,
-        session_service,
-        credential_service,
-    )
+  try:
+    if input_file:
+      session = await run_input_file(
+          app_name=session_app_name,
+          user_id=user_id,
+          agent_or_app=agent_or_app,
+          artifact_service=artifact_service,
+          session_service=session_service,
+          credential_service=credential_service,
+          input_path=input_file,
+      )
+    elif saved_session_file:
+      # Load the saved session from file
+      with open(saved_session_file, 'r', encoding='utf-8') as f:
+        loaded_session = Session.model_validate_json(f.read())
+
+      # Create a new session in the service, copying state from the file
+      session = await session_service.create_session(
+          app_name=session_app_name,
+          user_id=user_id,
+          state=loaded_session.state if loaded_session else None,
+      )
+
+      # Append events from the file to the new session and display them
+      if loaded_session:
+        for event in loaded_session.events:
+          await session_service.append_event(session, event)
+          _print_event(event)
+
+      await run_interactively(
+          agent_or_app,
+          artifact_service,
+          session,
+          session_service,
+          credential_service,
+          agent_loader=agent_loader if dev_mode else None,
+          agent_folder_name=agent_folder_name if dev_mode else None,
+          change_handler=change_handler,
+      )
+    else:
+      session = await session_service.create_session(
+          app_name=session_app_name, user_id=user_id
+      )
+      click.echo(f'Running agent {agent_or_app.name}, type exit to exit.')
+      await run_interactively(
+          agent_or_app,
+          artifact_service,
+          session,
+          session_service,
+          credential_service,
+          agent_loader=agent_loader if dev_mode else None,
+          agent_folder_name=agent_folder_name if dev_mode else None,
+          change_handler=change_handler,
+      )
+  finally:
+    # Clean up observer
+    if observer:
+      observer.stop()
+      observer.join()
 
   if save_session:
     session_id = session_id or input('Session ID to save: ')
diff --git a/src/google/adk/cli/cli_eval.py b/src/google/adk/cli/cli_eval.py
index cce160ae36..bbcc89ad90 100644
--- a/src/google/adk/cli/cli_eval.py
+++ b/src/google/adk/cli/cli_eval.py
@@ -97,7 +97,15 @@ def parse_and_get_evals_to_run(
   eval_set_to_evals = {}
   for input_eval_set in evals_to_run_info:
     evals = []
-    if ":" not in input_eval_set:
+    # Check if the input is a file path that exists (e.g. C:\path\to\file.json)
+    if os.path.exists(input_eval_set):
+      eval_set = input_eval_set
+    # Check if it's a file path with cases (e.g. C:\path\to\file.json:case1,case2)
+    elif ":" in input_eval_set and os.path.exists(input_eval_set.rsplit(":", 1)[0]):
+      eval_set = input_eval_set.rsplit(":", 1)[0]
+      evals = input_eval_set.rsplit(":", 1)[1].split(",")
+      evals = [s for s in evals if s.strip()]
+    elif ":" not in input_eval_set:
       # We don't have any eval cases specified. This would be the case where the
       # the user wants to run all eval cases in the eval set.
       eval_set = input_eval_set
diff --git a/src/google/adk/cli/cli_tools_click.py b/src/google/adk/cli/cli_tools_click.py
index 66f4dbe455..8337bfd092 100644
--- a/src/google/adk/cli/cli_tools_click.py
+++ b/src/google/adk/cli/cli_tools_click.py
@@ -24,7 +24,6 @@
 import os
 from pathlib import Path
 import tempfile
-import textwrap
 from typing import Optional
 
 import click
@@ -367,62 +366,7 @@ def validate_exclusive(ctx, param, value):
   return value
 
 
-def adk_services_options():
-  """Decorator to add ADK services options to click commands."""
-
-  def decorator(func):
-    @click.option(
-        "--session_service_uri",
-        help=textwrap.dedent(
-            """\
-            Optional. The URI of the session service.
-            - Leave unset to use the in-memory session service (default).
-            - Use 'agentengine://<agent_engine>' to connect to Agent Engine
-              sessions. <agent_engine> can either be the full qualified resource
-              name 'projects/abc/locations/us-central1/reasoningEngines/123' or
-              the resource id '123'.
-            - Use 'memory://' to run with the in-memory session service.
-            - Use 'sqlite://<path_to_sqlite_file>' to connect to a SQLite DB.
-            - See https://docs.sqlalchemy.org/en/20/core/engines.html#backend-specific-urls for more details on supported database URIs."""
-        ),
-    )
-    @click.option(
-        "--artifact_service_uri",
-        type=str,
-        help=textwrap.dedent(
-            """\
-            Optional. The URI of the artifact service.
-            - Leave unset to store artifacts under '.adk/artifacts' locally.
-            - Use 'gs://<bucket_name>' to connect to the GCS artifact service.
-            - Use 'memory://' to force the in-memory artifact service.
-            - Use 'file://<path>' to store artifacts in a custom local directory."""
-        ),
-        default=None,
-    )
-    @click.option(
-        "--memory_service_uri",
-        type=str,
-        help=textwrap.dedent("""\
-            Optional. The URI of the memory service.
-            - Use 'rag://<rag_corpus_id>' to connect to Vertex AI Rag Memory Service.
-            - Use 'agentengine://<agent_engine>' to connect to Agent Engine
-              sessions. <agent_engine> can either be the full qualified resource
-              name 'projects/abc/locations/us-central1/reasoningEngines/123' or
-              the resource id '123'.
-            - Use 'memory://' to force the in-memory memory service."""),
-        default=None,
-    )
-    @functools.wraps(func)
-    def wrapper(*args, **kwargs):
-      return func(*args, **kwargs)
-
-    return wrapper
-
-  return decorator
-
-
 @main.command("run", cls=HelpfulCommand)
-@adk_services_options()
 @click.option(
     "--save_session",
     type=bool,
@@ -465,6 +409,16 @@ def wrapper(*args, **kwargs):
     ),
     callback=validate_exclusive,
 )
+@click.option(
+    "--dev",
+    is_flag=True,
+    show_default=True,
+    default=False,
+    help=(
+        "Optional. Enable development mode with automatic agent reloading when"
+        " source files change. Watches for changes in .py and .yaml files."
+    ),
+)
 @click.argument(
     "agent",
     type=click.Path(
@@ -477,9 +431,7 @@ def cli_run(
     session_id: Optional[str],
     replay: Optional[str],
     resume: Optional[str],
-    session_service_uri: Optional[str] = None,
-    artifact_service_uri: Optional[str] = None,
-    memory_service_uri: Optional[str] = None,
+    dev: bool,
 ):
   """Runs an interactive CLI for a certain agent.
 
@@ -488,17 +440,11 @@ def cli_run(
   Example:
 
     adk run path/to/my_agent
+
+    adk run --dev path/to/my_agent
   """
   logs.log_to_tmp_folder()
 
-  # Validation warning for memory_service_uri (not supported for adk run)
-  if memory_service_uri:
-    click.secho(
-        "WARNING: --memory_service_uri is not supported for adk run.",
-        fg="yellow",
-        err=True,
-    )
-
   agent_parent_folder = os.path.dirname(agent)
   agent_folder_name = os.path.basename(agent)
 
@@ -510,8 +456,7 @@ def cli_run(
           saved_session_file=resume,
           save_session=save_session,
           session_id=session_id,
-          session_service_uri=session_service_uri,
-          artifact_service_uri=artifact_service_uri,
+          dev_mode=dev,
       )
   )
 
@@ -946,6 +891,55 @@ def wrapper(*args, **kwargs):
   return decorator
 
 
+def adk_services_options():
+  """Decorator to add ADK services options to click commands."""
+
+  def decorator(func):
+    @click.option(
+        "--session_service_uri",
+        help=(
+            """Optional. The URI of the session service.
+          - Use 'agentengine://<agent_engine>' to connect to Agent Engine
+            sessions. <agent_engine> can either be the full qualified resource
+            name 'projects/abc/locations/us-central1/reasoningEngines/123' or
+            the resource id '123'.
+          - Use 'sqlite://<path_to_sqlite_file>' to connect to an aio-sqlite
+            based session service, which is good for local development.
+          - Use 'postgresql://<user>:<password>@<host>:<port>/<database_name>'
+            to connect to a PostgreSQL DB.
+          - See https://docs.sqlalchemy.org/en/20/core/engines.html#backend-specific-urls
+            for more details on other database URIs supported by SQLAlchemy."""
+        ),
+    )
+    @click.option(
+        "--artifact_service_uri",
+        type=str,
+        help=(
+            "Optional. The URI of the artifact service,"
+            " supported URIs: gs://<bucket name> for GCS artifact service."
+        ),
+        default=None,
+    )
+    @click.option(
+        "--memory_service_uri",
+        type=str,
+        help=("""Optional. The URI of the memory service.
+            - Use 'rag://<rag_corpus_id>' to connect to Vertex AI Rag Memory Service.
+            - Use 'agentengine://<agent_engine>' to connect to Agent Engine
+              sessions. <agent_engine> can either be the full qualified resource
+              name 'projects/abc/locations/us-central1/reasoningEngines/123' or
+              the resource id '123'."""),
+        default=None,
+    )
+    @functools.wraps(func)
+    def wrapper(*args, **kwargs):
+      return func(*args, **kwargs)
+
+    return wrapper
+
+  return decorator
+
+
 def deprecated_adk_services_options():
   """Deprecated ADK services options."""
 
@@ -953,7 +947,7 @@ def warn(alternative_param, ctx, param, value):
     if value:
       click.echo(
           click.style(
-              f"WARNING: Deprecated option --{param.name} is used. Please use"
+              f"WARNING: Deprecated option {param.name} is used. Please use"
               f" {alternative_param} instead.",
               fg="yellow",
           ),
@@ -1148,8 +1142,6 @@ def cli_web(
 
     adk web --session_service_uri=[uri] --port=[port] path/to/agents_dir
   """
-  session_service_uri = session_service_uri or session_db_url
-  artifact_service_uri = artifact_service_uri or artifact_storage_uri
   logs.setup_adk_logger(getattr(logging, log_level.upper()))
 
   @asynccontextmanager
@@ -1174,6 +1166,8 @@ async def _lifespan(app: FastAPI):
         fg="green",
     )
 
+  session_service_uri = session_service_uri or session_db_url
+  artifact_service_uri = artifact_service_uri or artifact_storage_uri
   app = get_fast_api_app(
       agents_dir=agents_dir,
       session_service_uri=session_service_uri,
@@ -1247,10 +1241,10 @@ def cli_api_server(
 
     adk api_server --session_service_uri=[uri] --port=[port] path/to/agents_dir
   """
-  session_service_uri = session_service_uri or session_db_url
-  artifact_service_uri = artifact_service_uri or artifact_storage_uri
   logs.setup_adk_logger(getattr(logging, log_level.upper()))
 
+  session_service_uri = session_service_uri or session_db_url
+  artifact_service_uri = artifact_service_uri or artifact_storage_uri
   config = uvicorn.Config(
       get_fast_api_app(
           agents_dir=agents_dir,
diff --git a/tests/unittests/cli/utils/test_cli_tools_click.py b/tests/unittests/cli/utils/test_cli_tools_click.py
index 95b561e57b..373eda1f1d 100644
--- a/tests/unittests/cli/utils/test_cli_tools_click.py
+++ b/tests/unittests/cli/utils/test_cli_tools_click.py
@@ -45,6 +45,23 @@ def __init__(self, name):
     super().__init__(name=name)
     self.sub_agents = []
 
+  async def run_async(self, invocation_context):
+    """Mock run_async method for evaluation compatibility."""
+    from google.adk.events.event import Event
+    from google.adk.events.event import EventActions
+    from google.genai import types as genai_types
+
+    # Create a simple response event
+    content = genai_types.Content(
+        parts=[genai_types.Part(text="Mock response from dummy agent")]
+    )
+    event = Event(
+        author=self.name,
+        content=content,
+        action=EventActions.MODEL_RESPONSE,
+    )
+    yield event
+
 
 root_agent = DummyAgent(name="dummy_agent")
 
@@ -894,3 +911,130 @@ def _mock_to_cloud_run(*_a, **kwargs):
       " command."
   )
   assert expected_msg in result.output
+
+
+# Dev Mode Tests
+
+def test_dev_mode_change_handler_py_file():
+  """Test DevModeChangeHandler detects .py file changes."""
+  from google.adk.cli.cli import DevModeChangeHandler
+  from watchdog.events import FileSystemEvent
+
+  handler = DevModeChangeHandler()
+
+  # Test .py file change
+  event = FileSystemEvent('test.py')
+  event.is_directory = False
+  handler.on_modified(event)
+
+  reload_needed, file_changed = handler.check_and_reset()
+  assert reload_needed is True
+  assert file_changed == 'test.py'
+
+  # Test reset works
+  reload_needed2, file_changed2 = handler.check_and_reset()
+  assert reload_needed2 is False
+  assert file_changed2 is None
+
+
+def test_dev_mode_change_handler_yaml_file():
+  """Test DevModeChangeHandler detects .yaml file changes."""
+  from google.adk.cli.cli import DevModeChangeHandler
+  from watchdog.events import FileSystemEvent
+
+  handler = DevModeChangeHandler()
+
+  # Test .yaml file change
+  event = FileSystemEvent('config.yaml')
+  event.is_directory = False
+  handler.on_modified(event)
+
+  reload_needed, file_changed = handler.check_and_reset()
+  assert reload_needed is True
+  assert file_changed == 'config.yaml'
+
+
+def test_dev_mode_change_handler_ignores_non_matching_files():
+  """Test DevModeChangeHandler ignores files that don't match .py or .yaml."""
+  from google.adk.cli.cli import DevModeChangeHandler
+  from watchdog.events import FileSystemEvent
+
+  handler = DevModeChangeHandler()
+
+  # Test .txt file (should be ignored)
+  event = FileSystemEvent('readme.txt')
+  event.is_directory = False
+  handler.on_modified(event)
+
+  reload_needed, file_changed = handler.check_and_reset()
+  assert reload_needed is False
+  assert file_changed is None
+
+
+def test_dev_mode_change_handler_ignores_directories():
+  """Test DevModeChangeHandler ignores directory events."""
+  from google.adk.cli.cli import DevModeChangeHandler
+  from watchdog.events import FileSystemEvent
+
+  handler = DevModeChangeHandler()
+
+  # Test directory event (should be ignored)
+  event = FileSystemEvent('subdir')
+  event.is_directory = True
+  handler.on_modified(event)
+
+  reload_needed, file_changed = handler.check_and_reset()
+  assert reload_needed is False
+  assert file_changed is None
+
+
+def test_dev_mode_change_handler_on_created():
+  """Test DevModeChangeHandler detects file creation."""
+  from google.adk.cli.cli import DevModeChangeHandler
+  from watchdog.events import FileSystemEvent
+
+  handler = DevModeChangeHandler()
+
+  # Test file creation
+  event = FileSystemEvent('new_agent.py')
+  event.is_directory = False
+  handler.on_created(event)
+
+  reload_needed, file_changed = handler.check_and_reset()
+  assert reload_needed is True
+  assert file_changed == 'new_agent.py'
+
+
+async def test_cli_run_with_dev_flag(
+    tmp_path: Path, monkeypatch: pytest.MonkeyPatch
+) -> None:
+  """`adk run --dev` should call run_cli with dev_mode=True."""
+  rec = _Recorder()
+  monkeypatch.setattr(cli_tools_click, "run_cli", lambda **kwargs: rec(kwargs))
+  monkeypatch.setattr(
+      cli_tools_click.asyncio, "run", lambda coro: coro
+  )  # pass-through
+
+  # create dummy agent directory
+  agent_dir = tmp_path / "agent"
+  agent_dir.mkdir()
+  (agent_dir / "__init__.py").touch()
+  (agent_dir / "agent.py").touch()
+
+  runner = CliRunner()
+  result = runner.invoke(cli_tools_click.main, ["run", "--dev", str(agent_dir)])
+  assert result.exit_code == 0
+  assert rec.calls and rec.calls[0][0][0]["dev_mode"] is True
+
+
+def test_cli_run_dev_flag_help_text():
+  """Test that --dev flag appears in help text."""
+  runner = CliRunner()
+  result = runner.invoke(cli_tools_click.main, ["run", "--help"])
+  assert result.exit_code == 0
+  assert "--dev" in result.output
+  assert "Enable development mode" in result.output
+  # Check for key terms to be resilient to line wrapping
+  assert "automatic" in result.output
+  assert "agent" in result.output
+  assert "reloading" in result.output