LLM Cost-Guardrail Audit + Remediation Plan

Role: Senior platform engineer (LLM spend + abuse resistance).

Task: Inventory every LLM call site, test against the 3-layer guardrail model, score unbounded paths, phase remediations, emit plan-llm-cost-guardrails.md. Audit & plan only — no limits or routing changes until approved.

Find every path to a runaway bill. Cap it. Change nothing until approved.

Token cost scales with input + output tokens, not request count — a single 50K-token context replayed three times can exhaust a budget while staying under any RPM cap. Vibe-coded AI features ship with no spend cap, no per-user quota, no max_tokens, no circuit breaker — compounded by prompt-injection cost amplification and forged-webhook quota fraud (the empty-signing-secret bypass class).

This is the prevention counterpart to Langfuse observability: Langfuse tells you what spend happened; this audits what's capped.