hermes-agent/agent/secret_sources/bitwarden.py
Taylor H. Perkins db495b0fba refactor(secrets): extract shared cache/result substrate for secret sources
Pull the disk-cache + FetchResult substrate out of bitwarden.py into a new
agent/secret_sources/_cache.py: FetchResult, CachedFetch, is_valid_env_name,
and a generic DiskCache (atomic mkstemp -> chmod 0600 -> os.replace write,
0700 cache dir, TTL-gated read AND write). Bitwarden now consumes it via a
module-level DiskCache instance and thin wrappers, so the security-sensitive
atomic-write/0600/TTL logic lives in exactly one place instead of being
copy-pasted per backend (and drifting). Behavior is unchanged — the full
Bitwarden suite passes untouched.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
2026-07-06 04:58:07 -07:00

729 lines
27 KiB
Python

"""Bitwarden Secrets Manager (`bws` CLI) integration.
Hermes pulls API keys from Bitwarden Secrets Manager at process startup
so they don't have to live in plaintext in ``~/.hermes/.env``.
Design summary
--------------
* The ``bws`` binary is auto-installed into ``<hermes_home>/bin/bws`` on
first use. Hermes pins one version (``_BWS_VERSION``) and downloads
the matching asset from the official GitHub Releases page, verifying
the SHA-256 against the release's published checksum file.
* The access token is stored in ``~/.hermes/.env`` as
``BWS_ACCESS_TOKEN`` (or whatever name the user picked in
``secrets.bitwarden.access_token_env``). This is the one
bootstrap secret — every other provider key can live in Bitwarden.
* Pulling secrets is a single ``bws secret list <project_id>
--output json`` call. We cache the result in-process for
``cache_ttl_seconds`` so back-to-back ``hermes`` invocations don't
hammer the API.
* Failures NEVER block Hermes startup. Missing binary, no network,
expired token, etc. all emit a one-line warning and continue with
whatever credentials ``.env`` already had.
The module is intentionally subprocess-driven rather than going through
the ``bitwarden-sdk-secrets`` Python package: one cross-platform binary
is easier to lazy-install than a wheels-with-Rust-extension dependency.
"""
from __future__ import annotations
import hashlib
import json
import logging
import os
import platform
import shutil
import stat
import subprocess
import tempfile
import time
import urllib.error
import urllib.request
import zipfile
from pathlib import Path
from typing import Dict, List, Optional, Tuple
from agent.secret_sources._cache import (
CachedFetch as _CachedFetch,
DiskCache,
FetchResult,
is_valid_env_name as _is_valid_env_name,
)
from agent.secret_sources.base import ErrorKind, SecretSource
logger = logging.getLogger(__name__)
# ---------------------------------------------------------------------------
# Configuration constants
# ---------------------------------------------------------------------------
# Pinned upstream version. Bump in a follow-up PR — never auto-resolve
# "latest" because upstream release shape (asset names, CLI flags) is
# allowed to change between majors and we want updates to be deliberate.
_BWS_VERSION = "2.0.0"
_BWS_RELEASE_BASE = (
f"https://github.com/bitwarden/sdk-sm/releases/download/bws-v{_BWS_VERSION}"
)
_BWS_CHECKSUM_NAME = f"bws-sha256-checksums-{_BWS_VERSION}.txt"
# How long to wait for bws subprocesses and HTTP downloads, in seconds.
_BWS_DOWNLOAD_TIMEOUT = 60
_BWS_RUN_TIMEOUT = 30
# In-process cache so repeated load_hermes_dotenv() calls (CLI startup,
# gateway hot-reload, test suites) don't re-fetch from BSM.
_CacheKey = Tuple[str, str, str] # (access_token_fingerprint, project_id, server_url)
_CACHE: Dict[_CacheKey, _CachedFetch] = {}
# Disk-persisted cache so back-to-back CLI invocations (e.g. `hermes chat -q ...`
# called from scripts, cron, the gateway forking new agents) don't each pay the
# ~380ms `bws secret list` tax. The in-process _CACHE above only saves repeated
# fetches WITHIN one process; this saves repeated fetches ACROSS processes.
#
# Layout: one JSON object per cache key, written atomically with mode 0600 in
# <hermes_home>/cache/bws_cache.json. The file holds only the secret VALUES,
# never the access token. It's plaintext-equivalent to ~/.hermes/.env (which
# we already accept) but kept out of the .env file so users editing it won't
# accidentally commit BSM-sourced secrets. The atomic-write/0600/TTL mechanics
# live in agent.secret_sources._cache.DiskCache, shared with the other backends.
_DISK_CACHE_BASENAME = "bws_cache.json"
def _cache_key_str(cache_key: _CacheKey) -> str:
"""Serialize a cache key to a stable string for JSON storage."""
token_fp, project_id, server_url = cache_key
return f"{token_fp}|{project_id}|{server_url}"
_DISK_CACHE: DiskCache = DiskCache(
_DISK_CACHE_BASENAME, key_serializer=_cache_key_str
)
def _disk_cache_path(home_path: Optional[Path] = None) -> Path:
"""Return the disk cache path under hermes_home/cache/.
Thin wrapper over the shared DiskCache, kept for tests and any direct
callers; falls back to `$HERMES_HOME` / `~/.hermes` when home is None.
"""
return _DISK_CACHE.path(home_path)
# ---------------------------------------------------------------------------
# Binary discovery + lazy install
# ---------------------------------------------------------------------------
def _hermes_bin_dir() -> Path:
"""Where Hermes stores its managed binaries. Profile-aware."""
from hermes_constants import get_hermes_home
return get_hermes_home() / "bin"
def find_bws(*, install_if_missing: bool = False) -> Optional[Path]:
"""Return a path to a usable ``bws`` binary, or None.
Resolution order:
1. ``<hermes_home>/bin/bws`` (our managed copy — preferred)
2. ``shutil.which("bws")`` (system PATH)
When ``install_if_missing`` is True and neither resolves, this calls
:func:`install_bws` to download and verify the pinned version.
"""
managed = _hermes_bin_dir() / _platform_binary_name()
if managed.exists() and os.access(managed, os.X_OK):
return managed
system = shutil.which("bws")
if system:
return Path(system)
if install_if_missing:
try:
return install_bws()
except Exception as exc: # noqa: BLE001 — never block startup
logger.warning("bws auto-install failed: %s", exc)
return None
return None
def _platform_binary_name() -> str:
return "bws.exe" if platform.system() == "Windows" else "bws"
def _platform_asset_name() -> str:
"""Map (uname, arch, libc) → the upstream asset filename.
Asset names follow Rust's target triple convention. Linux defaults
to gnu (glibc); we switch to musl only if ldd --version says so.
"""
system = platform.system()
machine = platform.machine().lower()
if system == "Darwin":
# Universal binary works on both Intel and Apple Silicon — no
# need to pick a per-arch asset.
return f"bws-macos-universal-{_BWS_VERSION}.zip"
if system == "Windows":
arch = "aarch64" if machine in ("arm64", "aarch64") else "x86_64"
return f"bws-{arch}-pc-windows-msvc-{_BWS_VERSION}.zip"
if system == "Linux":
arch = "aarch64" if machine in ("arm64", "aarch64") else "x86_64"
libc = "gnu"
# ldd --version writes to stderr on glibc, stdout on musl. We
# don't need bullet-proof detection — getting it wrong falls
# back to a clear error from the binary loader, which we catch.
try:
res = subprocess.run(
["ldd", "--version"],
capture_output=True,
text=True,
timeout=2,
stdin=subprocess.DEVNULL,
)
if "musl" in (res.stdout + res.stderr).lower():
libc = "musl"
except (OSError, subprocess.TimeoutExpired):
pass
return f"bws-{arch}-unknown-linux-{libc}-{_BWS_VERSION}.zip"
raise RuntimeError(
f"Unsupported platform for bws auto-install: {system} {machine}"
)
def install_bws(*, force: bool = False) -> Path:
"""Download, verify, and install the pinned ``bws`` binary.
Returns the path to the installed executable. Raises on any
failure (network, checksum, extraction) — callers in the auto-install
path catch these; the user-facing ``hermes secrets bitwarden setup``
surface lets them propagate so the wizard can show a clear error.
"""
bin_dir = _hermes_bin_dir()
bin_dir.mkdir(parents=True, exist_ok=True)
target = bin_dir / _platform_binary_name()
if target.exists() and not force:
return target
asset_name = _platform_asset_name()
asset_url = f"{_BWS_RELEASE_BASE}/{asset_name}"
checksum_url = f"{_BWS_RELEASE_BASE}/{_BWS_CHECKSUM_NAME}"
with tempfile.TemporaryDirectory(prefix="hermes-bws-") as tmpdir:
tmp = Path(tmpdir)
zip_path = tmp / asset_name
checksum_path = tmp / _BWS_CHECKSUM_NAME
logger.info("Downloading %s", asset_url)
_http_download(asset_url, zip_path)
_http_download(checksum_url, checksum_path)
expected = _expected_sha256(checksum_path, asset_name)
actual = _sha256_file(zip_path)
if expected.lower() != actual.lower():
raise RuntimeError(
f"Checksum mismatch for {asset_name}: "
f"expected {expected}, got {actual}"
)
with zipfile.ZipFile(zip_path) as zf:
member = _pick_zip_member(zf, _platform_binary_name())
# Zip-slip guard: a malicious archive can carry member names like
# ``../../etc/cron.d/x`` or absolute paths. ``ZipFile.extract``
# joins the member onto ``tmp`` without verifying the result stays
# inside it, so validate containment before touching the disk.
extracted = _safe_extract_member(zf, member, tmp)
# Move into place atomically. We write to a sibling tempfile in
# the final directory so the rename can't cross filesystems.
fd, staged = tempfile.mkstemp(dir=str(bin_dir), prefix=".bws_")
os.close(fd)
shutil.copy2(extracted, staged)
os.chmod(
staged,
stat.S_IRUSR | stat.S_IWUSR | stat.S_IXUSR
| stat.S_IRGRP | stat.S_IXGRP
| stat.S_IROTH | stat.S_IXOTH,
)
os.replace(staged, target)
logger.info("Installed bws %s at %s", _BWS_VERSION, target)
return target
def _http_download(url: str, dest: Path) -> None:
req = urllib.request.Request(url, headers={"User-Agent": "hermes-agent"})
try:
with urllib.request.urlopen(req, timeout=_BWS_DOWNLOAD_TIMEOUT) as resp: # noqa: S310
with open(dest, "wb") as f:
shutil.copyfileobj(resp, f)
except urllib.error.URLError as exc:
raise RuntimeError(f"Failed to download {url}: {exc}") from exc
def _expected_sha256(checksum_file: Path, asset_name: str) -> str:
"""Parse the upstream ``bws-sha256-checksums-X.Y.Z.txt`` file.
Format is the standard ``sha256sum`` output: ``<hex> <filename>``,
one per line.
"""
text = checksum_file.read_text(encoding="utf-8", errors="replace")
for line in text.splitlines():
parts = line.strip().split()
if len(parts) >= 2 and parts[-1] == asset_name:
return parts[0]
raise RuntimeError(
f"No checksum entry for {asset_name} in {checksum_file.name}"
)
def _sha256_file(path: Path) -> str:
h = hashlib.sha256()
with open(path, "rb") as f:
for chunk in iter(lambda: f.read(65536), b""):
h.update(chunk)
return h.hexdigest()
def _pick_zip_member(zf: zipfile.ZipFile, binary_name: str) -> str:
"""Find the binary inside the upstream zip.
Historically the archive has been flat (``bws`` at the root) but we
tolerate a top-level directory just in case upstream changes.
"""
candidates = [n for n in zf.namelist() if n.split("/")[-1] == binary_name]
if not candidates:
raise RuntimeError(
f"Could not find {binary_name} inside downloaded archive "
f"(members: {zf.namelist()[:5]}...)"
)
# Prefer the shortest path (i.e. root over nested) for determinism.
candidates.sort(key=len)
return candidates[0]
def _safe_extract_member(
zf: zipfile.ZipFile, member: str, dest_dir: Path
) -> Path:
"""Extract a single archive member, refusing path traversal.
``ZipFile.extract`` will happily honour member names containing
``../`` or absolute paths, letting a malicious archive write outside
``dest_dir`` (a "zip-slip"). We resolve the would-be target and
confirm it stays within ``dest_dir`` before extracting.
"""
dest_root = os.path.realpath(dest_dir)
target = os.path.realpath(os.path.join(dest_root, member))
# ``commonpath`` raises ValueError for e.g. different drives on
# Windows; treat that as an escape too.
try:
contained = os.path.commonpath([dest_root, target]) == dest_root
except ValueError:
contained = False
if not contained or target == dest_root:
raise RuntimeError(
f"Refusing to extract unsafe archive member {member!r}: "
f"it escapes the extraction directory"
)
zf.extract(member, dest_root)
return Path(target)
# ---------------------------------------------------------------------------
# Secret fetch + apply
# ---------------------------------------------------------------------------
def _token_fingerprint(token: str) -> str:
"""SHA-256 prefix used as a cache key — never logged, never displayed."""
return hashlib.sha256(token.encode("utf-8")).hexdigest()[:16]
def fetch_bitwarden_secrets(
*,
access_token: str,
project_id: str,
binary: Optional[Path] = None,
cache_ttl_seconds: float = 300,
use_cache: bool = True,
server_url: str = "",
home_path: Optional[Path] = None,
) -> Tuple[Dict[str, str], List[str]]:
"""Pull the secrets for ``project_id`` from Bitwarden Secrets Manager.
Returns ``(secrets_dict, warnings_list)``.
Set ``server_url`` to point at a non-default Bitwarden region or a
self-hosted instance — e.g. ``https://vault.bitwarden.eu`` for EU
Cloud accounts. When empty, ``bws`` uses its built-in default
(``https://vault.bitwarden.com``, US Cloud). This is plumbed into
the subprocess as ``BWS_SERVER_URL``.
Caching is a two-layer LRU: an in-process dict (for hot-reload paths
inside one process) and a disk-persisted JSON file under
``<hermes_home>/cache/bws_cache.json`` (for back-to-back CLI invocations).
Both share the same TTL. Pass ``home_path`` so disk cache lookups find
the right directory in tests / non-standard installs; otherwise we fall
back to ``$HERMES_HOME`` / ``~/.hermes``.
Raises :class:`RuntimeError` for fatal conditions (missing binary,
auth failure, unparseable output). Callers in the env_loader path
catch this and emit a single warning; callers in the user-facing
setup wizard let it propagate.
"""
if not access_token:
raise RuntimeError("Bitwarden access token is empty")
if not project_id:
raise RuntimeError("Bitwarden project_id is empty")
cache_key = (_token_fingerprint(access_token), project_id, server_url or "")
if use_cache:
cached = _CACHE.get(cache_key)
if cached and cached.is_fresh(cache_ttl_seconds):
return cached.secrets, []
# L2: disk cache. ~5ms on cache hit vs ~380ms for `bws secret list`.
disk_cached = _DISK_CACHE.read(cache_key, cache_ttl_seconds, home_path)
if disk_cached is not None:
# Promote into in-process cache so subsequent fetches in the
# same process skip the disk read too.
_CACHE[cache_key] = disk_cached
return disk_cached.secrets, []
bws = binary or find_bws(install_if_missing=True)
if bws is None:
raise RuntimeError(
"bws binary not available — auto-install failed and `bws` is "
"not on PATH. Install manually from "
"https://github.com/bitwarden/sdk-sm/releases or re-run "
"`hermes secrets bitwarden setup`."
)
secrets, warnings = _run_bws_list(bws, access_token, project_id, server_url)
entry = _CachedFetch(secrets=secrets, fetched_at=time.time())
_CACHE[cache_key] = entry
if use_cache:
_DISK_CACHE.write(cache_key, entry, cache_ttl_seconds, home_path)
return secrets, warnings
def _run_bws_list(
bws: Path, access_token: str, project_id: str, server_url: str = ""
) -> Tuple[Dict[str, str], List[str]]:
cmd = [str(bws), "secret", "list", project_id, "--output", "json"]
env = os.environ.copy()
env["BWS_ACCESS_TOKEN"] = access_token
# Make sure we're not echoing telemetry / colour codes into json.
env.setdefault("NO_COLOR", "1")
# Region / self-hosted support. bws defaults to https://vault.bitwarden.com
# (US Cloud); EU Cloud users need https://vault.bitwarden.eu, and
# self-hosted users need their own URL. When unset, fall back to whatever
# BWS_SERVER_URL the caller already had in their shell env (preserved by
# the copy above) so manual overrides keep working too.
if server_url:
env["BWS_SERVER_URL"] = server_url
try:
proc = subprocess.run( # noqa: S603 — bws path is trusted
cmd,
env=env,
capture_output=True,
text=True,
timeout=_BWS_RUN_TIMEOUT,
stdin=subprocess.DEVNULL,
)
except subprocess.TimeoutExpired as exc:
raise RuntimeError(
f"bws timed out after {_BWS_RUN_TIMEOUT}s fetching secrets"
) from exc
except OSError as exc:
raise RuntimeError(f"failed to invoke bws: {exc}") from exc
if proc.returncode != 0:
# bws writes auth/network errors to stderr in plain English.
# Strip ANSI just in case and surface the first 200 chars.
err = (proc.stderr or proc.stdout or "").strip().replace("\x1b", "")
raise RuntimeError(
f"bws exited {proc.returncode}: {err[:200]}"
)
raw = proc.stdout.strip()
if not raw:
return {}, ["bws returned no output (empty project?)"]
try:
payload = json.loads(raw)
except json.JSONDecodeError as exc:
raise RuntimeError(f"bws returned non-JSON output: {exc}") from exc
if not isinstance(payload, list):
raise RuntimeError(
f"bws returned unexpected shape: {type(payload).__name__}"
)
secrets: Dict[str, str] = {}
warnings: List[str] = []
for item in payload:
if not isinstance(item, dict):
continue
key = item.get("key")
value = item.get("value")
if not isinstance(key, str) or not isinstance(value, str):
continue
if not _is_valid_env_name(key):
warnings.append(
f"Skipping secret {key!r}: not a valid env-var name"
)
continue
secrets[key] = value
return secrets, warnings
# ---------------------------------------------------------------------------
# Public entry point — called from hermes_cli.env_loader
# ---------------------------------------------------------------------------
def apply_bitwarden_secrets(
*,
enabled: bool,
access_token_env: str = "BWS_ACCESS_TOKEN",
project_id: str = "",
override_existing: bool = False,
cache_ttl_seconds: float = 300,
auto_install: bool = True,
server_url: str = "",
home_path: Optional[Path] = None,
) -> FetchResult:
"""Pull secrets from BSM and set them on ``os.environ``.
This is the function ``load_hermes_dotenv()`` calls after the .env
files have loaded. It is intentionally defensive — any failure
returns a :class:`FetchResult` with ``error`` set; it never raises.
``server_url`` selects the Bitwarden region or self-hosted endpoint
(e.g. ``https://vault.bitwarden.eu`` for EU Cloud). Empty string
means use ``bws``'s default (US Cloud).
Parameters mirror the ``secrets.bitwarden.*`` config keys so the
caller can just splat the dict in.
"""
result = FetchResult()
if not enabled:
return result
access_token = os.environ.get(access_token_env, "").strip()
if not access_token:
result.error = (
f"secrets.bitwarden.enabled is true but {access_token_env} is "
"not set. Run `hermes secrets bitwarden setup`."
)
return result
if not project_id:
result.error = (
"secrets.bitwarden.project_id is empty. "
"Run `hermes secrets bitwarden setup`."
)
return result
binary = find_bws(install_if_missing=auto_install)
result.binary_path = binary
if binary is None:
result.error = (
"bws binary not available and auto-install is disabled. "
"Run `hermes secrets bitwarden setup` to install."
)
return result
try:
secrets, warnings = fetch_bitwarden_secrets(
access_token=access_token,
project_id=project_id,
binary=binary,
cache_ttl_seconds=cache_ttl_seconds,
server_url=server_url,
home_path=home_path,
)
except RuntimeError as exc:
result.error = str(exc)
return result
result.secrets = secrets
result.warnings.extend(warnings)
for key, value in secrets.items():
if key == access_token_env:
# Don't let BSM clobber the very token we used to fetch
# itself — that would be a footgun if someone stored the
# token as a BSM secret too.
result.skipped.append(key)
continue
if not override_existing and os.environ.get(key):
result.skipped.append(key)
continue
os.environ[key] = value
result.applied.append(key)
return result
# ---------------------------------------------------------------------------
# SecretSource adapter — the registry-facing wrapper around this module.
# ---------------------------------------------------------------------------
class BitwardenSource(SecretSource):
"""Bitwarden Secrets Manager as a registered secret source.
Thin adapter over the module's fetch machinery. ``fetch()`` only
*fetches* — precedence, override semantics, conflict warnings, and
the ``os.environ`` writes are the orchestrator's job
(see ``agent.secret_sources.registry.apply_all``).
Bitwarden is a **bulk** source: it injects every secret in the
configured BSM project, so explicit per-var bindings from mapped
sources (e.g. the 1Password ``env:`` map) outrank it.
"""
name = "bitwarden"
label = "Bitwarden Secrets Manager"
shape = "bulk"
scheme = "bws"
def override_existing(self, cfg: dict) -> bool:
# Default True (matches DEFAULT_CONFIG): the point of BSM is
# centralized rotation — if .env had the final say, rotating a
# key in Bitwarden wouldn't take effect until the stale .env
# line was also deleted.
return bool(isinstance(cfg, dict) and cfg.get("override_existing", True))
def protected_env_vars(self, cfg: dict):
token_env = "BWS_ACCESS_TOKEN"
if isinstance(cfg, dict):
token_env = str(cfg.get("access_token_env") or token_env)
return frozenset({token_env})
def config_schema(self) -> dict:
return {
"enabled": {"description": "Master switch", "default": False},
"access_token_env": {
"description": "Env var holding the machine-account access token",
"default": "BWS_ACCESS_TOKEN",
},
"project_id": {"description": "BSM project UUID", "default": ""},
"cache_ttl_seconds": {
"description": "Disk+memory cache TTL; 0 disables",
"default": 300,
},
"override_existing": {
"description": "BSM values overwrite .env/shell values",
"default": True,
},
"auto_install": {
"description": "Auto-download the pinned bws binary",
"default": True,
},
"server_url": {
"description": "Region / self-hosted endpoint (empty = US Cloud)",
"default": "",
},
}
def fetch(self, cfg: dict, home_path: Path) -> FetchResult:
cfg = cfg if isinstance(cfg, dict) else {}
result = FetchResult()
access_token_env = str(cfg.get("access_token_env") or "BWS_ACCESS_TOKEN")
access_token = os.environ.get(access_token_env, "").strip()
if not access_token:
result.error = (
f"secrets.bitwarden.enabled is true but {access_token_env} is "
"not set. Run `hermes secrets bitwarden setup`."
)
result.error_kind = ErrorKind.NOT_CONFIGURED
return result
project_id = str(cfg.get("project_id") or "")
if not project_id:
result.error = (
"secrets.bitwarden.project_id is empty. "
"Run `hermes secrets bitwarden setup`."
)
result.error_kind = ErrorKind.NOT_CONFIGURED
return result
auto_install = bool(cfg.get("auto_install", True))
binary = find_bws(install_if_missing=auto_install)
result.binary_path = binary
if binary is None:
result.error = (
"bws binary not available and auto-install is disabled. "
"Run `hermes secrets bitwarden setup` to install."
)
result.error_kind = ErrorKind.BINARY_MISSING
return result
try:
ttl = float(cfg.get("cache_ttl_seconds", 300))
except (TypeError, ValueError):
ttl = 300.0
try:
secrets, warnings = fetch_bitwarden_secrets(
access_token=access_token,
project_id=project_id,
binary=binary,
cache_ttl_seconds=ttl,
server_url=str(cfg.get("server_url", "") or "").strip(),
home_path=home_path,
)
except RuntimeError as exc:
result.error = str(exc)
result.error_kind = _classify_bws_error(str(exc))
return result
result.secrets = secrets
result.warnings.extend(warnings)
return result
def _classify_bws_error(message: str) -> ErrorKind:
"""Best-effort mapping of bws failure text onto the shared taxonomy."""
lowered = message.lower()
if "timed out" in lowered:
return ErrorKind.TIMEOUT
if "binary not available" in lowered or "failed to invoke" in lowered:
return ErrorKind.BINARY_MISSING
if any(tok in lowered for tok in ("unauthorized", "invalid token",
"access token", "401", "403")):
return ErrorKind.AUTH_FAILED
if any(tok in lowered for tok in ("network", "connection", "resolve",
"download", "dns")):
return ErrorKind.NETWORK
return ErrorKind.INTERNAL
# ---------------------------------------------------------------------------
# Test hook — used by hermetic tests to flush the cache between cases.
# ---------------------------------------------------------------------------
def _reset_cache_for_tests(home_path: Optional[Path] = None) -> None:
"""Clear in-process AND disk caches.
Tests can pass ``home_path`` to scope the disk cleanup to a tmpdir.
Without it we fall back to the same default resolution as the cache
writer itself.
"""
_CACHE.clear()
_DISK_CACHE.clear(home_path)