/simplify-code pass on the salvage stack. The hand-rolled module-global
probe cache ignored its binary argument (stale verdict survives a binary
swap) and logged per launch; switch to the repo's established
functools.lru_cache capability-probe pattern (cua_backend, browser_tool),
probe stdout+stderr, share the --http-cache-dir literal via a module
constant, tighten the probe timeout to 3s, and cover the probe's
except branch in tests. Mutation-checked: gate tests fail with the
gate removed and with the probe hardcoded True.
Salvage follow-up for PR #100269. The flag landed upstream in 0.3.x;
binaries before it (e.g. 0.2.8, verified locally) fatally reject the
flag with 'unknown argument', breaking every Browser Use launch.
Probe 'lightpanda help' once per process and omit the flag when the
binary predates it. Also soften the unverified concurrency claim in
the _http_cache_dir docstring and tell docs readers to stop sessions
before deleting the live sqlite cache.
Lightpanda's HTTP cache is opt-in (`--http-cache-dir`, off by default), and
the launcher never passed it, so every Browser Use navigation re-fetched
every asset.
Point all Hermes-spawned instances at one shared cache under
$HERMES_HOME/cache/browser-use/lightpanda/http-cache. Sharing it across
sessions keeps assets warm through session churn; Lightpanda stores it in
sqlite (WAL), so a write that loses a race degrades to a cache miss rather
than a failed load, and --http-cache-entry-limit (default 1000) bounds the
directory without Hermes managing eviction.
Measured over 25 navigations across 5 sites, median warm navigation drops
from 0.40s to 0.18s on news.ycombinator.com and 0.14s to 0.10s on
wikipedia; total navigation time 7.0s -> 5.9s.
The flag has existed since Lightpanda 0.3.x (April 2026), so this needs no
minimum-version bump.
- lightpanda_engine_status: check use_real_profile before the cloud
provider, matching browser_exec's actual resolution order (real-profile
resolution runs before backend resolution), so /browser status and
hermes doctor name the right shadowing setting when both are set.
- launch_lightpanda: drop the unreachable Windows popen_kwargs branch
(find_lightpanda_binary returns None on nt, launch errors out earlier).
- doctor: drop the over-defensive try/except around the cached
_using_lightpanda_engine() config read.
- Docstring: 'no-I/O gates' -> 'no network I/O (config reads only)'.
- New test pinning real-profile-over-cloud-provider reason precedence.
Browser Use mode never read browser.engine: _resolve_backend_cdp() went
BU_CDP_* env -> CDP override -> cloud provider -> local Chrome, so
`engine: lightpanda` was a silent no-op on the default backend, and on
the built-in path it was skipped whenever a cloud provider, Camofox or a
CDP override was active without anyone saying so.
- browser_use_cli: when the engine is lightpanda and nothing with higher
precedence claimed the session, get a session from _get_session_info()
and export its endpoint as BU_CDP_URL; the browser is private to the
session key, so the own-tab preamble is skipped. The browser_exec
description gains a Lightpanda header (text-first, new_tab once then
goto_url — lightpanda-io/browser#1962).
- browser_tool: _create_local_session() spawns `lightpanda serve
--host 127.0.0.1 --port <free>` per session key (new
tools/browser_lightpanda.py), reusing the session cache, inactivity
reaper and atexit cleanup; a dead process is respawned on the next call;
orphans from a crashed Hermes are reaped through per-process records in
$HERMES_HOME/cache/browser-use/lightpanda/. New lightpanda_engine_status()
reports whether the engine is in effect or what shadows it.
- tools_config: "Lightpanda" row in the Browser Automation picker
(cloud_provider: local + engine: lightpanda; "Local Browser" resets the
engine to auto) with a binary-check post-setup.
- /browser status and hermes doctor print the engine state and, when it
is shadowed, the reason.
