#116713 parsed HERMES_LANGFUSE_MAX_DEPTH inside `_safe_value`, i.e. once per
captured prompt, response, tool input and tool output. With an invalid value
(`abc`) every captured field logged the same "Invalid ... Falling back to 4"
WARNING for the life of the process — one multi-tool turn fills agent.log.
Resolve the depth in `_resolve_max_depth`, an lru_cache keyed on the raw env
string: the warning fires once per distinct bad value, a changed env var is
still picked up by a long-lived process (mirrors `_capture_mode`, which also
reads per call and warns once), and valid values skip the int() parse after
the first call.
Follow-up to #116713 (independent review finding).
34b475e2ce