Surface LLM provider/model/last-error on /health for diagnostics

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01WN4QRr6dTE2W7hQ2SDnLmY

backend/app/generate.py

@@ -53,11 +53,25 @@ _SYSTEM = (
 )
 
 
+# Last generation error (for diagnostics via /health). Trimmed, no secrets.
+last_error: str | None = None
+
+
 def llm_available() -> bool:
     """True when an LLM API key is configured."""
     return bool(os.getenv("LLM_API_KEY"))
 
 
+def status() -> dict[str, object]:
+    """Diagnostic snapshot surfaced on /health."""
+    return {
+        "llm_enabled": llm_available(),
+        "llm_provider": _provider,
+        "llm_model": _MODEL,
+        "llm_error": last_error,
+    }
+
+
 def generate_answer(question: str, passages: list[str]) -> str | None:
     """Return a grounded answer from the passages, or None to fall back.
 
@@ -87,8 +101,11 @@ def generate_answer(question: str, passages: list[str]) -> str | None:
             ],
         )
     except Exception as exc:  # never let generation break /ask
+        global last_error
+        last_error = f"{type(exc).__name__}: {exc}"[:400]
         logger.warning("LLM generation failed, using extractive answer: %s", exc)
         return None
 
+    last_error = None
     text = (response.choices[0].message.content or "").strip()
     return text or None

backend/app/main.py

@@ -15,7 +15,7 @@ from fastapi import FastAPI, File, Form, HTTPException, UploadFile
 from fastapi.middleware.cors import CORSMiddleware
 from pydantic import BaseModel
 
-from . import __version__, db
+from . import __version__, db, generate
 from .generate import generate_answer, llm_available
 from .parsing import DocumentError, chunk_text, extract_pdf_text
 from .retrieval import DocumentIndex, best_sentence
@@ -59,7 +59,7 @@ app.add_middleware(
 def health() -> dict[str, object]:
     """Liveness probe. Also reports the running version and whether LLM answer
     generation is configured, which makes deploys easy to verify."""
-    return {"status": "ok", "version": __version__, "llm_enabled": llm_available()}
+    return {"status": "ok", "version": __version__, **generate.status()}
 
 
 def _looks_like_pdf(file: UploadFile) -> bool: