The logging conversion itself is correct (good use of %s/%d lazy formatting instead of f-strings). But there are two bugs introduced:

1. Missing return in exception handler (critical)
Same issue as PR #92 — return f"Error: {e}" is removed with no replacement:

except Exception as e:
    logger.error("Error in handle_chat: %s", e)
    logger.exception("Exception occurred in handle_chat")
    # ← no return — handle_chat returns None on exception

Please add: return "I encountered an error. Please try again."

2. Removes try/except around call_gemini_for_final_synthesis (regression)
The original had a fallback for Gemini failures:

# Original (safe):
try:
    response = await call_gemini_for_final_synthesis(...)
except Exception:
    response = "Unable to process your request. Please try again."

# PR #85 (unsafe):
response = await call_gemini_for_final_synthesis(...)  # unguarded

If Gemini returns an error, the exception now bubbles up unhandled. Please restore the try/except.

3. Indentation on multi-line logger calls (minor)

# Wrong:
logger.info(
"Results summary: KS=%d, Vector=%d, Combined=%d",
len(ks_results),
)

# Correct:
logger.info(
    "Results summary: KS=%d, Vector=%d, Combined=%d",
    len(ks_results),
)

Fix these three and this PR is good to merge.