diff --git a/.gitignore b/.gitignore
index f8c5b95..73d7e7e 100644
--- a/.gitignore
+++ b/.gitignore
@@ -6,6 +6,7 @@ __pycache__/
 router.log
 .venv/
 venv/
+.hf-cache/
 .omo/
 config.yaml.bak.*
 config/config.local.yaml
diff --git a/deploy/README.md b/deploy/README.md
index 0ac26c1..42b470d 100644
--- a/deploy/README.md
+++ b/deploy/README.md
@@ -109,6 +109,15 @@ your allowance. `ProtectHome=read-only` plus a `ReadWritePaths` exception for
 the repo limits the blast radius on the filesystem, but nothing limits spend.
 Putting this on a LAN address needs an auth layer first.
 
+If you enable `classifier.mode: local_encoder`, note `HF_HOME` is redirected
+into the repo (`%h/llm-router/.hf-cache`) for the same reason — Hugging
+Face's default cache lives outside `ReadWritePaths` and the service will
+crash-loop trying to download a model into a read-only home directory
+otherwise. Run `pip install -r requirements-encoder.txt` before switching to
+this mode; the startup check refuses to boot with a clear message if it's
+missing, rather than failing opaquely on the first request, but a missing
+model still needs the dependency installed first.
+
 ## Using an Ollama on another machine
 
 The local LLM does the classifying; it does not have to be on the machine you
diff --git a/deploy/llm-router.service b/deploy/llm-router.service
index 8d76add..e7182fa 100644
--- a/deploy/llm-router.service
+++ b/deploy/llm-router.service
@@ -19,6 +19,13 @@ Environment=PYTHONPATH=%h/llm-router/src
 # Holds NEURALWATT_API_KEY. Create it with:
 #   echo "NEURALWATT_API_KEY=$NEURALWATT_API_KEY" > .env && chmod 600 .env
 EnvironmentFile=%h/llm-router/.env
+# HuggingFace's default cache (~/.cache/huggingface) falls outside
+# ReadWritePaths below; redirect it into the repo instead of widening the
+# sandbox to a new home-directory path. Only classifier.mode: local_encoder
+# ever touches this. Caught live 2026-09-06: without this, the service
+# crash-loops with "OSError: Read-only file system" the moment
+# local_encoder needs to download a model.
+Environment=HF_HOME=%h/llm-router/.hf-cache
 ExecStart=%h/llm-router/.venv/bin/uvicorn dispatcher:app --host 127.0.0.1 --port 8080 --timeout-graceful-shutdown 5
 
 Restart=always