Location
crates/librefang-kernel/src/scheduler.rs:140-216crates/librefang-kernel/src/kernel/mod.rs:4737-4780
Problem
check_quota (line 4737) reads tracker, compares to limit, returns OK. The LLM call then takes seconds. record_usage (line 4780) increments the tracker after success. With N concurrent agent sessions (or trigger fires) that all enter send_message_full between check and record, all N pass the check (tracker still at pre-check value), all N spend tokens, then all N record — total spend can be Nx the burst cap.
Impact
Hourly token budget is a soft suggestion under concurrency. burst_cap = token_limit / 5 rate fence is bypassable similarly. Final billing is correct but the preventive circuit-breaker doesn't fire.
Fix
Add a reserve(estimated_max_tokens) step that atomically charges a conservative upper bound at check-time, then record_usage reconciles with the real number (refunding unused). Or merge the two into a pre_charge + settle API.
Filed via automated multi-perspective audit (security / concurrency / architecture / error-handling / frontend / performance subagents). Curated against #3359–#3409 to avoid duplicates.
Location
crates/librefang-kernel/src/scheduler.rs:140-216crates/librefang-kernel/src/kernel/mod.rs:4737-4780Problem
check_quota(line 4737) reads tracker, compares to limit, returns OK. The LLM call then takes seconds.record_usage(line 4780) increments the tracker after success. With N concurrent agent sessions (or trigger fires) that all entersend_message_fullbetween check and record, all N pass the check (tracker still at pre-check value), all N spend tokens, then all N record — total spend can be Nx the burst cap.Impact
Hourly token budget is a soft suggestion under concurrency.
burst_cap = token_limit / 5rate fence is bypassable similarly. Final billing is correct but the preventive circuit-breaker doesn't fire.Fix
Add a
reserve(estimated_max_tokens)step that atomically charges a conservative upper bound at check-time, thenrecord_usagereconciles with the real number (refunding unused). Or merge the two into apre_charge+settleAPI.Filed via automated multi-perspective audit (security / concurrency / architecture / error-handling / frontend / performance subagents). Curated against #3359–#3409 to avoid duplicates.