Notes on autonomous agents, runaway cost, and the security of systems that act on their own.https://fathomforge.dev/en-us© fathomforgecarlos@fathomforge.dev (Carlos M.)https://fathomforge.dev/writing/three-shapes-of-a-runaway/https://fathomforge.dev/writing/three-shapes-of-a-runaway/Five months of production agent logs, and almost every expensive incident is one of three patterns. None of them look like failures while they're happening.Thu, 10 Sep 2026 00:00:00 GMTagentscostincidentshttps://fathomforge.dev/writing/prompt-injection-is-a-blast-radius-problem/https://fathomforge.dev/writing/prompt-injection-is-a-blast-radius-problem/You cannot reliably detect the attack. So stop making detection the control, and start bounding what a successful one costs you — including being honest about which bounds you actually have.Sun, 06 Sep 2026 00:00:00 GMTprompt-injectionagentssecurityhttps://fathomforge.dev/writing/reading-usage-without-reading-prompts/https://fathomforge.dev/writing/reading-usage-without-reading-prompts/A guardrail sees everything an agent says. Here's how to build one that enforces a spend cap without ever being able to reconstruct a conversation.Wed, 02 Sep 2026 00:00:00 GMTprivacydesignagents