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fix(renderer): keep the HTTP shell from resurrecting a refused wall #497

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us merged 1 commit into from
Sep 3, 2026
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fix(renderer): keep the HTTP shell from resurrecting a refused wall #497

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67 changes: 63 additions & 4 deletions crates/crw-renderer/src/lib.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -1690,7 +1690,22 @@ impl FallbackRenderer {
// pixels), and an explicit renderer pin is a caller
// contract that forbids silent substitution. Both fail
// closed, matching the no-renderer arm directly above.
Err(e) if screenshot_requested() || is_hard_pinned => Err(e),
// The HTTP shell substitutes for a failed ladder so the
// caller gets content instead of nothing. But when that
// shell IS the wall the ladder just refused to clear,
// returning it hands back exactly what every tier
// rejected, as a billed success. Fail instead; a shell
// that is not a wall still substitutes as before.
Err(e)
if screenshot_requested()
|| is_hard_pinned
|| detector::looks_like_generic_bot_wall(
&http_result.html,
http_result.truncated,
) =>
{
Err(e)
}
Err(e) => {
if is_auth_blocked {
tracing::error!(
Expand Down Expand Up @@ -1911,9 +1926,16 @@ impl FallbackRenderer {
.await
{
Ok(js_result) => Ok(js_result),
Err(e) if is_hard_pinned => {
// User explicitly pinned a renderer — surface the error
// instead of silently returning the (likely useless) HTTP body.
Err(e)
if is_hard_pinned
|| detector::looks_like_generic_bot_wall(
&result.html,
result.truncated,
) =>
{
// Pinned: the caller's contract forbids substitution.
// Wall: see the sibling arm — the shell is the very
// thing the ladder rejected, so it is not a fallback.
Err(e)
}
Err(e) => {
Expand Down Expand Up @@ -4883,6 +4905,43 @@ mod tests {
));
}

/// The ladder correctly refuses a wall, and then the HTTP-shell fallback
/// hands the same wall back anyway. Prod log, 2026-09-03: "JS escalation
/// failed for soft-block status; surfacing HTTP shell with warning: ...
/// blocked by an anti-bot wall that none of the 3 renderer tier(s)
/// attempted could clear". The ladder's verdict has to survive that
/// substitution, or rejecting the wall upstream buys nothing.
#[tokio::test]
async fn http_shell_fallback_does_not_resurrect_a_wall() {
let wall = "<html><body><h1>Security Check</h1>\
<p>Checking your browser before accessing the site</p></body></html>";
let lp = Arc::new(MockFetcher {
name: "lightpanda",
behavior: MockBehavior::Ok(wall.to_string()),
}) as Arc<dyn PageFetcher>;
let mut r = make_renderer_with_mocks(vec![lp]);
r.http = Arc::new(MockFetcher {
name: "http",
behavior: MockBehavior::Ok(wall.to_string()),
});

let out = r
.fetch(
"https://example.com",
&HashMap::new(),
Some(true),
None,
None,
tdl(),
)
.await;
assert!(
out.is_err(),
"the wall must not come back through the HTTP shell: {:?}",
out.ok().map(|r| (r.rendered_with, r.html.len()))
);
}

/// Prod shipped an anti-bot interstitial to a paying customer as
/// `success: true` with `creditCost: 1`, because the ladder tail returned
/// the best thin result without re-reading the verdict every tier had
Expand Down
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