DOM.getDocument{depth:-1} (the standard full-tree call from Puppeteer/
Playwright/browser-use) arrived as u32::MAX and drove serialize_node to
recurse once per DOM nesting level. A page can nest nodes tens of thousands
deep (trivially scriptable; html5ever caps no generic nesting), so the
recursion overflowed the stack — a SIGABRT that catch_unwind cannot recover,
crashing the whole worker (AGENTS.md: "one page must never crash a worker").
Deriving the builder alone is not enough: the response is inherently nested
JSON, and serde_json's own serialization and the Value's Drop recurse over
that nesting too, overflowing the ~2 MiB tokio worker stack. So this both
rewrites serialize_node as an explicit heap worklist and clamps the effective
depth to MAX_SERIALIZE_DEPTH (256), mirroring DOMSnapshot's MAX_NODES guard.
Real DOMs are far shallower; clients wanting a deeper subtree re-request it
with DOM.requestChildNodes / describeNode.
Adds a regression test that builds a 50k-deep tree and serializes with
depth:-1; it SIGABRTs before this change and passes after (run on nextest's
2 MiB test thread, mirroring production).
Andrey Mnatsakanov
d8e9fc2196