Log LLM provider errors with stack traces to fix silent failures

[Copilot]

Users reported BLAST appearing to run but producing no output/tokens. Root cause: LLM provider errors (invalid API keys, connection failures) were caught but logged without stack traces, making debugging impossible.

Changes

• Core execution paths: Added exc_info=True to exception handlers in scheduler.py, executor.py, resource_factory.py
• API endpoints: Added exc_info=True to handlers in server_api_chat_completions.py, server_api_realtime.py
• Tests: Added test_error_logging.py to verify stack traces are logged

Example

Before:

except Exception as e:
    logger.error(f"Task {task_id} failed: {e}")  # No stack trace
    await self.complete_task(task_id, success=False)
    raise

After:

except Exception as e:
    logger.error(f"Task {task_id} failed: {e}", exc_info=True)  # Full stack trace logged
    await self.complete_task(task_id, success=False)
    raise

Now when authentication or connection issues occur, the engine log will contain full stack traces showing exactly what failed (e.g., AuthenticationError: Invalid API key with complete traceback).

Original prompt

Please debug this issue:

blast not returining any output
Image
EreQ

— 12/15/25, 10:33 PM
Are we moving on from blast?
Caleb Winston — 12/15/25, 11:21 PM
No, we're actively developing this and will get more active in the new year. We're working on a key improvement in the auto scheduler. (paper coming soon)

If you let us know your use case, we can better support it (and ensure it continues to function!)
EreQ

— 12/15/25, 11:57 PM
Right now its not even generating tokens
I thought it was a config issue but its not.
We're using it as a backend automation engine replacing the current front end
ronyw — 12/16/25, 12:55 AM
Curious why this happened, do you spot any issues in the engine log?
EreQ

— 12/16/25, 12:56 AM
There are no logs
all the metrics are at 0
The keys are working
ronyw — 12/16/25, 12:59 AM
When running blastai serve there is a log dir that gets displayed in the CLI. The engine log should contain helpful information for debugging.
❯ blastai serve
╭──────────────────────────────────────────────────────────────────────────────╮
│ Engine: http://127.0.0.1:8000 blast-logs/1eddb8f8.engine.log │
│ Web: http://localhost:3000 blast-logs/1eddb8f8.web.log │
╰──────────────────────────────────────────────────────────────────────────────╯

Are you using a different way to start the service?
EreQ

— 12/16/25, 1:00 AM
There are no errors
There are no tokens generated
ronyw — 12/16/25, 1:09 AM
Hmm, that sound suspiciously like an LLM provider/connection issue to me... although couldn't confirm without the logs. I also can't reproduce this locally on the latest commit and installing in a fresh environment
Also recommend checking if the backend service is up and running, i.e., not just the GUI is running
EreQ

— 12/16/25, 1:44 AM
So a provider error would show up?

Identify the potential root cause and things to try

---

💬 We'd love your input! Share your thoughts on Copilot coding agent in our 2 minute survey.