diff --git a/CHANGELOG.md b/CHANGELOG.md
index e6ff9c4..44c0604 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -8,6 +8,11 @@ project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html). E
 
 ## [Unreleased]
 
+### Fixed
+
+- A passphrase-protected `TLS_KEY_FILE` now stops startup with a message that the key must be
+  unencrypted. Before, the app could wait at a password prompt on a host with a terminal.
+
 ## [0.7.2] - 2026-10-27
 
 ### Added
diff --git a/INSTALL.md b/INSTALL.md
index 9de0d7a..42937a8 100644
--- a/INSTALL.md
+++ b/INSTALL.md
@@ -234,11 +234,11 @@ The API serves HTTPS itself when `TLS_CERT_FILE` and `TLS_KEY_FILE` both point a
    chmod 644 tls/cert.pem && chmod 640 tls/key.pem && sudo chgrp 44 tls/key.pem
    ```
 
-   The app runs as user 1000, group 44 (`video`) in the container, so the key must be readable by one of them.
+   The app runs as user 1000, group 44 (`video`) in the container, so the key must be readable by one of them. The key must be unencrypted (`-nodes` above): the app does not ask for a passphrase.
 
 1. Uncomment the `./tls:/app/tls:ro` volume under `app` in `compose.yml`.
 
-1. Set the files and the HTTPS base URL in `.env`, then run `docker compose up -d`:
+1. Set the files and the HTTPS base URL in the `.env` next to `compose.yml` (Compose passes it to the container, so the healthcheck sees it too), then run `docker compose up -d`:
 
    ```sh
    TLS_CERT_FILE=/app/tls/cert.pem
diff --git a/app/core/settings.py b/app/core/settings.py
index 2cdf2df..b5df1ad 100644
--- a/app/core/settings.py
+++ b/app/core/settings.py
@@ -120,9 +120,10 @@ def validate_tls_files(cert_file: str, key_file: str) -> None:
     if not cert_file:
         return
     try:
-        ssl.create_default_context(ssl.Purpose.CLIENT_AUTH).load_cert_chain(cert_file, key_file)
+        # An empty password makes an encrypted key fail here instead of OpenSSL prompting for one.
+        ssl.create_default_context(ssl.Purpose.CLIENT_AUTH).load_cert_chain(cert_file, key_file, password=b"")
     except (OSError, ssl.SSLError) as exc:
-        msg = f"TLS_CERT_FILE and TLS_KEY_FILE could not be loaded: {exc}"
+        msg = f"TLS_CERT_FILE and TLS_KEY_FILE could not be loaded (the key must be unencrypted): {exc}"
         raise ValueError(msg) from exc
 
 
diff --git a/pyproject.toml b/pyproject.toml
index 26bc176..5073a93 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -27,7 +27,7 @@
   # Dependencies and version constraints
   dependencies = [
     "fastapi>=0.115.8",
-    "fastapi-cli>=0.0.32",                      # NOTE: the Dockerfile CMD and `just dev` use `fastapi run|dev`
+    "fastapi-cli>=0.0.32",                      # NOTE: `just dev` runs `fastapi dev`; the image runs app/serve.py
     "httpx>=0.28,<1",
     "jinja2>=3.1.5",                            # NOTE: Jinja2Templates
     "opentelemetry-exporter-otlp-proto-http>=1.38.0",
@@ -40,7 +40,7 @@
     "pyjwt[crypto]>=2.12.1",
     "python-multipart>=0.0.18",                 # NOTE: Form() fields in app/auth/router.py
     "r9cam-models>=0.6.1,<0.7",                 # NOTE: Keep this aligned with the published contract package
-    "uvicorn[standard]>=0.12.0",                # NOTE: the server behind `fastapi run`; [standard] adds uvloop and httptools
+    "uvicorn[standard]>=0.12.0",                # NOTE: app/serve.py runs it; [standard] adds uvloop and httptools
     "websockets>=16.0",
   ]
 
diff --git a/tests/unit/core/test_config.py b/tests/unit/core/test_config.py
index f0eea1c..6c2b340 100644
--- a/tests/unit/core/test_config.py
+++ b/tests/unit/core/test_config.py
@@ -4,6 +4,7 @@
 from pathlib import Path
 
 import pytest
+from cryptography.hazmat.primitives import serialization
 from pydantic import HttpUrl
 
 import app.core.bootstrap as config_mod
@@ -361,6 +362,20 @@ def test_key_that_does_not_match_is_rejected(self, tmp_path: Path) -> None:
         with pytest.raises(ValueError, match="could not be loaded"):
             Settings(tls_cert_file=str(cert), tls_key_file=str(other_key))
 
+    def test_encrypted_key_fails_instead_of_prompting(self, tmp_path: Path) -> None:
+        """A passphrase-protected key stops startup at once; OpenSSL must not wait for a password."""
+        cert, key = write_self_signed_cert(tmp_path)
+        loaded = serialization.load_pem_private_key(key.read_bytes(), password=None)
+        key.write_bytes(
+            loaded.private_bytes(
+                serialization.Encoding.PEM,
+                serialization.PrivateFormat.PKCS8,
+                serialization.BestAvailableEncryption(b"secret"),
+            )
+        )
+        with pytest.raises(ValueError, match="unencrypted"):
+            Settings(tls_cert_file=str(cert), tls_key_file=str(key))
+
     def test_valid_pair_turns_tls_on(self, tmp_path: Path) -> None:
         """A readable certificate and matching key enable TLS."""
         cert, key = write_self_signed_cert(tmp_path)