Regression of #3977 / #4054: adk create accepts hyphens in agent names, agent then fails to load #8002

🔴 Required Information

Describe the Bug:
adk create accepts an agent name containing a hyphen (e.g. adk-local) and creates the agent folder, but the agent cannot be loaded afterwards. In adk web the app is listed by /list-apps, but every message fails (POST /run_sse returns 404) and the request never reaches the model. Renaming the folder to use an underscore (adk_local) fixes it.

Steps to Reproduce:

1. pip install google-adk litellm
2. adk create my-agent
3. Replace my-agent/agent.py with the minimal code below
4. adk web --host 0.0.0.0 --port 8000 --log_level DEBUG
5. Open the Web UI, select my-agent, send any message
6. Observe POST /run_sse -> 404 Not Found in the server log

Expected Behavior:
adk create should reject names that cannot be loaded as an agent package (same rule as the agent loader), e.g. with a clear error suggesting my_agent.

Observed Behavior:
The folder is created without any warning. The app is listed in the Web UI, but every message fails with POST /run_sse 404, so the agent is unusable until the folder is renamed.

Environment Details:

• ADK Library Version (pip show google-adk): 2.13.0
• Desktop OS: Linux (Debian)
• Python Version (python -V): 3.13.5

Model Information:

• Are you using LiteLLM: Yes
• Which model is being used: qwen3:8b via Ollama (ollama_chat/qwen3:8b). The issue is not model-specific.

🟡 Optional Information

Regression:
Yes, this looks like a regression of #3977 and #4054, which were closed as completed in January 2026. Still reproducible in 2.13.0.

Logs:

INFO:     <client-ip> - "POST /run_sse HTTP/1.1" 404 Not Found
INFO:     <client-ip> - "GET /dev/apps/adk-local/debug/trace/session/<session-id> HTTP/1.1" 200 OK

Screenshots / Video:
N/A

Additional Context:
Root cause (from reading the source of google-adk 2.13.0):

• cli/cli_create.py validates the folder name with validate_app_name() from apps/app.py, whose regex allows hyphens: ^[a-zA-Z][a-zA-Z0-9_-]*$.
• cli/utils/_nested_agent_loader.py requires every part of the agent name to pass str.isidentifier(), so my-agent is rejected at load time.

Suggested fix: keep validate_app_name() as is (hyphens are fine for App.name), but in cli_create.py additionally require app_name.isidentifier() for the folder name, since the folder is imported as a Python package.

Minimal Reproduction Code:

# my-agent/agent.py
from google.adk.agents import Agent
from google.adk.models.lite_llm import LiteLlm

root_agent = Agent(
    name="my_agent",
    model=LiteLlm(model="ollama_chat/qwen3:8b"),
    instruction="Answer briefly.",
)

How often has this issue occurred?:

• Always (100%)