Improve VLM client lifecycle, retries, metrics, and cache keys

- Adds abstract aclose() and shared load_prompt() helper to BaseVLMClient.

- OllamaClient now logs latency, tokens, and prompt hash per call.

- Retries cover HTTP 429 and 5xx in addition to network/timeout errors.

- Cache key now includes response_format and max_tokens.

- Warns when JSON schema generation falls back to plain 'json' format.

- Adds FakeVLMClient.aclose() and cache unit tests.

src/odoo_ocr/clients/base.py

@@ -35,6 +35,11 @@ class BaseVLMClient(ABC):
         """Send a chat request with optional images and return parsed text."""
         ...
 
+    @abstractmethod
+    async def aclose(self) -> None:
+        """Release client resources (connections, file handles, ...)."""
+        ...
+
     @staticmethod
     def parse_json(content: str, model: type[T]) -> T:
         """Strip markdown fences and parse/validate JSON against a Pydantic model."""
@@ -54,7 +59,24 @@ class BaseVLMClient(ABC):
 
     @staticmethod
     def _load_prompt_file(path: Path | str) -> str:
-        """Load a plain-text prompt from the prompts directory."""
+        """Load a plain-text prompt file."""
         path = Path(path)
         with path.open("r", encoding="utf-8") as f:
             return f.read()
+
+
+def load_prompt(name: str) -> str:
+    """Load a plain-text system prompt from the project's ``prompts/`` directory.
+
+    Tries the current working directory first (running from the repo root),
+    then falls back to the repository root derived from this package's
+    location, so the CLI keeps working from any working directory.
+    """
+    candidates = [
+        Path("prompts") / name,
+        Path(__file__).resolve().parents[3] / "prompts" / name,
+    ]
+    for candidate in candidates:
+        if candidate.is_file():
+            return candidate.read_text(encoding="utf-8")
+    raise FileNotFoundError(f"Prompt file not found: {name!r} (tried: {candidates})")

src/odoo_ocr/clients/ollama.py

@@ -3,6 +3,7 @@
 from __future__ import annotations
 
 import base64
+import hashlib
 import io
 import logging
 import time
@@ -13,7 +14,7 @@ from PIL import Image
 from pydantic import BaseModel
 from tenacity import (
     retry,
-    retry_if_exception_type,
+    retry_if_exception,
     stop_after_attempt,
     wait_exponential,
 )
@@ -26,6 +27,16 @@ from odoo_ocr.utils import cache
 logger = logging.getLogger(__name__)
 
 
+def _is_transient_retryable(exc: BaseException) -> bool:
+    """Retry network errors, timeouts, HTTP 429, and server errors (5xx)."""
+    if isinstance(exc, (httpx.NetworkError, httpx.TimeoutException)):
+        return True
+    if isinstance(exc, httpx.HTTPStatusError):
+        status = exc.response.status_code
+        return status == 429 or status >= 500
+    return False
+
+
 class OllamaClient(BaseVLMClient):
     """Client for Ollama's /api/chat endpoint with vision support."""
 
@@ -35,6 +46,10 @@ class OllamaClient(BaseVLMClient):
         self.timeout = httpx.Timeout(120.0, connect=10.0)
         self.http = httpx.AsyncClient(timeout=self.timeout)
 
+    async def aclose(self) -> None:
+        """Release the underlying HTTP client."""
+        await self.http.aclose()
+
     @staticmethod
     def _encode_image(image: Image.Image, quality: int = 85) -> str:
         """Convert a PIL image to a base64-encoded PNG or JPEG string."""
@@ -62,6 +77,7 @@ class OllamaClient(BaseVLMClient):
         model_name = model or self.settings.models.ocr
         encoded_images = [self._encode_image(img) for img in images]
         image_blobs = [base64.b64decode(enc) for enc in encoded_images]
+        format_key = response_format.__name__ if response_format is not None else "text"
 
         cached = cache.get_cached(
             system_prompt,
@@ -69,7 +85,9 @@ class OllamaClient(BaseVLMClient):
             image_blobs,
             model_name,
             temperature,
+            max_tokens,
             self.settings,
+            format_key=format_key,
         )
         if cached:
             return VLMResponse.model_validate(cached)
@@ -93,7 +111,12 @@ class OllamaClient(BaseVLMClient):
         if response_format is not None:
             try:
                 body["format"] = response_format.model_json_schema()
-            except Exception:
+            except Exception as exc:
+                logger.warning(
+                    "Could not build JSON schema for %s, falling back to 'json' format: %s",
+                    response_format.__name__,
+                    exc,
+                )
                 body["format"] = "json"
 
         start = time.perf_counter()
@@ -118,15 +141,25 @@ class OllamaClient(BaseVLMClient):
             image_blobs,
             model_name,
             temperature,
+            max_tokens,
             vlm_response.model_dump(mode="json"),
             self.settings,
+            format_key=format_key,
+        )
+        logger.info(
+            "Ollama %s: %d ms, prompt_tokens=%s, completion_tokens=%s, prompt_hash=%s",
+            model_name,
+            duration_ms,
+            vlm_response.prompt_tokens,
+            vlm_response.completion_tokens,
+            hashlib.sha256((system_prompt + user_prompt).encode("utf-8")).hexdigest(),
         )
         return vlm_response
 
     @retry(
         stop=stop_after_attempt(3),
         wait=wait_exponential(multiplier=1, min=1, max=10),
-        retry=retry_if_exception_type((httpx.NetworkError, httpx.TimeoutException)),
+        retry=retry_if_exception(_is_transient_retryable),
     )
     async def _post_chat(self, body: dict[str, Any]) -> dict[str, Any]:
         """Send the chat request and validate the response."""

src/odoo_ocr/utils/cache.py

@@ -26,21 +26,37 @@ def _cache_path(settings: Settings, key: str) -> Path:
     return cache_dir / f"{key}.json"
 
 
+def _cache_key_parts(
+    system_prompt: str,
+    user_prompt: str,
+    image_blobs: list[bytes],
+    model: str,
+    temperature: float,
+    max_tokens: int,
+    format_key: str,
+) -> list[str]:
+    parts = [system_prompt, user_prompt, model, str(temperature), str(max_tokens), format_key]
+    for blob in image_blobs:
+        parts.append(hashlib.sha256(blob).hexdigest())
+    return parts
+
+
 def get_cached(
     system_prompt: str,
     user_prompt: str,
     image_blobs: list[bytes],
     model: str,
     temperature: float,
+    max_tokens: int,
     settings: Settings,
+    format_key: str = "text",
 ) -> dict[str, Any] | None:
     """Return cached response dict if it exists, otherwise None."""
     if not settings.cache.enabled:
         return None
-    parts = [system_prompt, user_prompt, model, str(temperature)]
-    for blob in image_blobs:
-        parts.append(hashlib.sha256(blob).hexdigest())
-    key = _make_key(parts)
+    key = _make_key(
+        _cache_key_parts(system_prompt, user_prompt, image_blobs, model, temperature, max_tokens, format_key)
+    )
     path = _cache_path(settings, key)
     if path.exists():
         logger.debug("Cache hit: %s", key)
@@ -55,16 +71,17 @@ def set_cached(
     image_blobs: list[bytes],
     model: str,
     temperature: float,
+    max_tokens: int,
     response: dict[str, Any],
     settings: Settings,
+    format_key: str = "text",
 ) -> None:
     """Store a response in the file cache."""
     if not settings.cache.enabled:
         return
-    parts = [system_prompt, user_prompt, model, str(temperature)]
-    for blob in image_blobs:
-        parts.append(hashlib.sha256(blob).hexdigest())
-    key = _make_key(parts)
+    key = _make_key(
+        _cache_key_parts(system_prompt, user_prompt, image_blobs, model, temperature, max_tokens, format_key)
+    )
     path = _cache_path(settings, key)
     with path.open("w", encoding="utf-8") as f:
         json.dump(response, f, ensure_ascii=False, indent=2)

tests/conftest.py

@@ -52,3 +52,7 @@ class FakeVLMClient(BaseVLMClient):
             if key in system_prompt or key in user_prompt:
                 return VLMResponse(content=json.dumps(value), model="fake")
         return VLMResponse(content=json.dumps({}), model="fake")
+
+    async def aclose(self) -> None:
+        """The fake client holds no resources."""
+        return None

tests/test_cache.py

@@ -0,0 +1,44 @@
+"""Tests for the LLM response cache."""
+
+from __future__ import annotations
+
+import pytest
+
+from odoo_ocr.config import Settings
+from odoo_ocr.utils import cache
+
+
+@pytest.fixture
+def cache_settings(tmp_path) -> Settings:
+    return Settings(cache={"enabled": True, "dir": tmp_path / "llm_cache"})
+
+
+def test_cache_roundtrip(cache_settings: Settings) -> None:
+    response = {"content": "hello", "model": "m", "prompt_tokens": 1}
+    cache.set_cached("sys", "user", [b"img"], "model", 0.1, 4096, response, cache_settings)
+    assert cache.get_cached("sys", "user", [b"img"], "model", 0.1, 4096, cache_settings) == response
+
+
+def test_cache_miss(cache_settings: Settings) -> None:
+    assert cache.get_cached("a", "b", [], "m", 0.1, 4096, cache_settings) is None
+
+
+def test_cache_disabled(tmp_path) -> None:
+    settings = Settings(cache={"enabled": False, "dir": tmp_path / "llm_cache"})
+    cache.set_cached("sys", "user", [], "m", 0.1, 4096, {"content": "x"}, settings)
+    assert cache.get_cached("sys", "user", [], "m", 0.1, 4096, settings) is None
+    assert not (tmp_path / "llm_cache").exists()
+
+
+def test_cache_key_includes_temperature_format_and_max_tokens(cache_settings: Settings) -> None:
+    response = {"content": "x"}
+    cache.set_cached("sys", "user", [], "m", 0.1, 4096, response, cache_settings, format_key="text")
+    # Different temperature must not hit the same entry.
+    assert cache.get_cached("sys", "user", [], "m", 0.2, 4096, cache_settings) is None
+    # Different response_format must not hit the same entry.
+    assert (
+        cache.get_cached("sys", "user", [], "m", 0.1, 4096, cache_settings, format_key="ExtractedInvoice")
+        is None
+    )
+    # Different max_tokens must not hit the same entry.
+    assert cache.get_cached("sys", "user", [], "m", 0.1, 2048, cache_settings) is None