diff --git a/winnow/cache.py b/winnow/cache.py
index d554401..8d1bbdb 100644
--- a/winnow/cache.py
+++ b/winnow/cache.py
@@ -7,43 +7,62 @@ recomputing on reruns. Uses numpy binary format for fast I/O.
 import hashlib
 import logging
 import os
+from pathlib import Path
 
 import numpy as np
 
 logger = logging.getLogger(__name__)
 
-# Model versions — bump these when the upstream model changes.
-# LIMITATION — no automatic invalidation: if the user replaces the buffalo_l
-# model files on disk (e.g. custom weights, InsightFace update) without
-# changing INSIGHTFACE_HOME, the version string here stays "buffalo_l_v1" and
-# stale embeddings from the old model are served from cache indefinitely.
-# TODO: derive the version from a checksum of the model files, or expose a
-# --clear-cache / CLEAR_EMBEDDING_CACHE flag so users can force invalidation.
 MODEL_VERSIONS = {
-    "insightface": "buffalo_l_v1",
     "immich": "immich_buffalo_l_v1",
 }
 
 
+def _insightface_model_fingerprint() -> str:
+    """Derive a version string from buffalo_l .onnx file sizes and mtimes.
+
+    Changes automatically when model files are replaced or updated, preventing
+    stale embeddings from a previous model being served from cache.
+    Falls back to a static string before the model is downloaded (first run).
+    """
+    insightface_home = os.environ.get("INSIGHTFACE_HOME", os.path.expanduser("~/.insightface"))
+    model_dir = Path(insightface_home) / "models" / "buffalo_l"
+    if not model_dir.exists():
+        return "buffalo_l_v1"
+    onnx_files = sorted(model_dir.glob("*.onnx"))
+    if not onnx_files:
+        return "buffalo_l_v1"
+    fingerprint = "|".join(
+        f"{f.name}:{f.stat().st_size}:{int(f.stat().st_mtime)}"
+        for f in onnx_files
+    )
+    return hashlib.sha256(fingerprint.encode()).hexdigest()[:12]
+
+
 class EmbeddingCache:
     """Simple disk-based embedding cache.
 
     Embeddings are stored as .npy files in a flat directory,
-    keyed by a hash of (asset_id, model_version).
+    keyed by a hash of (asset_id, model_version). The InsightFace version
+    is derived from buffalo_l model file metadata so the cache auto-invalidates
+    when model files are replaced or updated.
     """
 
     def __init__(self, cache_dir: str = ".if_cache") -> None:
         self.cache_dir = cache_dir
         self._ensured = False
+        self._model_versions = {
+            **MODEL_VERSIONS,
+            "insightface": _insightface_model_fingerprint(),
+        }
 
     def _ensure_dir(self) -> None:
         if not self._ensured:
             os.makedirs(self.cache_dir, exist_ok=True)
             self._ensured = True
 
-    @staticmethod
-    def _key(asset_id: str, model: str) -> str:
-        version = MODEL_VERSIONS.get(model, model)
+    def _key(self, asset_id: str, model: str) -> str:
+        version = self._model_versions.get(model, model)
         raw = f"{asset_id}:{version}"
         return hashlib.sha256(raw.encode()).hexdigest()[:16]
 
@@ -96,4 +115,3 @@ def get_cache(cache_dir: str = ".if_cache") -> EmbeddingCache:
     if _cache is None:
         _cache = EmbeddingCache(cache_dir)
     return _cache
-
diff --git a/winnow/cli.py b/winnow/cli.py
index a88ee4e..52f2f73 100644
--- a/winnow/cli.py
+++ b/winnow/cli.py
@@ -9,7 +9,7 @@ from rich.prompt import Confirm
 
 from .config import Config, ConfigManager
 from .executor import execute_jobs, upload_to_frigate
-from .immich_api import get_people, merge_people
+from .immich_api import get_immich_version, get_people, merge_people
 from .jobs import _show_preview, auto_configure, interactive_configure
 from .log_config import console, setup_logging
 from .upload_tracker import find_by_crop_dimension, get_person_summary, reset_person
@@ -216,6 +216,13 @@ def main() -> None:
                     f" {counts['rejected']} rejected{frigate_part}[/dim]"
                 )
 
+        _immich_version = get_immich_version()
+        if _immich_version is not None and _immich_version < (1, 106, 0):
+            rprint(
+                f"  [yellow]⚠  Immich {'.'.join(str(x) for x in _immich_version)} detected — "
+                "winnow requires v1.106+. Some features may not work.[/yellow]"
+            )
+
         people = get_people()
         if not people:
             rprint("[bold red]Could not fetch people from Immich. Check URL/Key.[/bold red]")
diff --git a/winnow/executor.py b/winnow/executor.py
index bd56342..35248a8 100644
--- a/winnow/executor.py
+++ b/winnow/executor.py
@@ -17,6 +17,7 @@ from .frigate_api import (
     delete_frigate_person_files,
     get_all_frigate_person_files,
     get_frigate_person_files,
+    get_frigate_version,
     recognize_face,
 )
 from .image_processing import process_face_mode
@@ -311,10 +312,17 @@ def upload_to_frigate(jobs: list[dict]) -> None:
         rprint("[yellow]⚠️  FRIGATE_URL not set, skipping upload.[/yellow]")
         return
 
-    # TODO: verify Frigate version at startup (GET /api/version) and warn if
-    # below v0.16. The face training API (/api/faces/{name}/register,
-    # /api/faces/{name}/delete, /api/faces/recognize) was introduced in v0.16;
-    # older versions return 404s that surface as opaque upload failures.
+    _frigate_version = get_frigate_version()
+    if _frigate_version is not None:
+        try:
+            parts = [int(x) for x in _frigate_version.split("-")[0].split(".") if x.isdigit()]
+            if len(parts) >= 2 and (parts[0], parts[1]) < (0, 16):
+                rprint(
+                    f"  [yellow]⚠  Frigate {_frigate_version} detected — "
+                    "face training API requires v0.16+. Uploads may fail.[/yellow]"
+                )
+        except Exception:
+            pass
 
     rprint("\n[bold cyan]📤 Uploading to Frigate[/bold cyan]")
     rprint(f"  Target: [dim]{frigate_url}[/dim]")
diff --git a/winnow/frigate_api.py b/winnow/frigate_api.py
index 38ce3f5..0cfdd7d 100644
--- a/winnow/frigate_api.py
+++ b/winnow/frigate_api.py
@@ -8,6 +8,24 @@ import requests
 logger = logging.getLogger(__name__)
 
 
+def get_frigate_version() -> str | None:
+    """Fetch Frigate's version string from GET /api/version.
+
+    Returns the version string (e.g. "0.16.0-beta4") or None if FRIGATE_URL
+    is unset, the endpoint is unreachable, or the response is not parseable.
+    """
+    frigate_url = os.environ.get("FRIGATE_URL", "").rstrip("/")
+    if not frigate_url:
+        return None
+    try:
+        resp = requests.get(f"{frigate_url}/api/version", timeout=5)
+        if resp.ok:
+            return resp.text.strip().strip('"')
+        return None
+    except Exception:
+        return None
+
+
 def _get_faces_data() -> dict | None:
     """Fetch raw GET /api/faces response. Returns None if unavailable."""
     frigate_url = os.environ.get("FRIGATE_URL", "").rstrip("/")
diff --git a/winnow/immich_api.py b/winnow/immich_api.py
index d3332be..32dd05f 100644
--- a/winnow/immich_api.py
+++ b/winnow/immich_api.py
@@ -26,6 +26,25 @@ class FaceData:
     image_height: int
 
 
+def get_immich_version() -> tuple[int, int, int] | None:
+    """Fetch Immich server version from GET /api/server/version.
+
+    Returns (major, minor, patch) or None if unreachable or unparseable.
+    """
+    try:
+        resp = requests.get(
+            f"{Config.IMMICH_URL}/api/server/version",
+            headers=get_headers(),
+            timeout=5,
+        )
+        if resp.ok:
+            data = resp.json()
+            return (int(data["major"]), int(data["minor"]), int(data["patch"]))
+        return None
+    except Exception:
+        return None
+
+
 def get_people() -> list[dict]:
     """Fetch all people from Immich."""
     try: