build_run_config() copied every top-level request key (except
configurable/context) verbatim into the LangGraph RunnableConfig, including
recursion_limit. The server default of 100 was fully overridable by the caller
with no upper bound, so a request like {"config": {"recursion_limit": 100000000}}
could make a single run execute effectively unbounded LangGraph super-steps
(each >= 1 LLM call), enabling runaway API cost / DoS.
Validate the client value server-side and clamp it into a safe range:
- valid positive ints are capped at a configurable ceiling
(AppConfig.max_recursion_limit, default 1000 to match the existing
frontend/public-skill default so legitimate deep runs are unaffected)
- invalid/non-positive/bool/None values fall back to the 100 server default
- applied on both the configurable and the LangGraph >= 0.6.0 context paths
- WARNING logged on clamp for observability
Add unit tests (including a configurable-ceiling case), expose
max_recursion_limit in config.example.yaml (config_version 16), and document
the ceiling/fallback in backend/docs/API.md.
Co-authored-by: DengY11 <DengY11@users.noreply.github.com>
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