Most agent frameworks are optimized for the demo. KEVLAR is a set of patterns — deduplication, budget guards, silent-auth recovery, self-healing supervision — extracted from a voice assistant that has run continuously in production, not a weekend prototype.
Now shipped as a library → pip install kevlar-agent
Every pattern below exists because something failed first in a live system, with a live user on the other end. Here's what actually holds an always-on agent together.
OAuth flows that try to open a browser and wait for a human click will hang forever when called from an unattended background thread. Every credentialed call gets a silent mode that fails fast and reports instead of blocking.
A model can emit the same tool call twice in one turn — once from an eager first pass, once from a retry. A short time-windowed dedupe key (tool + args) absorbs the echo without touching the real side effect twice.
Every paid API call sits behind a monthly spend ceiling tracked independently per feature, not per account. A runaway loop in one capability can't drain the budget of every other capability sharing the same key.
Irreversible actions require an explicit confirmed=true flag enforced in the dispatch layer — not a polite instruction in the system prompt. A model misreading intent once is not an acceptable failure mode for money or publishing.
Every tool invocation — args, result, error, latency, and calling channel — is appended to a structured log. Not for compliance theater: it's the dataset that reveals which capabilities are actually used, and which ones quietly fail.
A lightweight external process checks that every core service is alive on a fixed interval and restarts what isn't — independent of the services it watches, so one crash can't take down its own recovery mechanism.
These six patterns aren't just documented on this page — they're shipped as kevlar-agent, a tested, zero-dependency Python library. Drop them into your own agent today.
dedupe, budget_guard, require_confirmation, silent, AuditLog, WatchdogA scheduled health pass exercises the real code paths — not just "did it import" — and only speaks up when something is actually wrong.
Voice, chat, and messaging channels all route through the same audited, budget-guarded dispatch layer — so a capability built once is trustworthy everywhere it's exposed, and every channel inherits the same safety rails automatically.