--- title: "System Design Simple (@systemdesignsimple) | Hashnode" description: "System design, AI tools and security fixes, explained simply. Read the latest articles by System Design Simple on Hashnode." url: "https://hashnode.com/@systemdesignsimple" --- @systemdesignsimple # System Design Simple @systemdesignsimple · Joined November 2026 System design, AI tools and security fixes, explained simply [Website](https://systemdesignsimple.com/) ### [Codex CLI agent command center: what 0.167.0 changes when you run several agents](https://systemdesignsimple.hashnode.dev/codex-cli-agent-command-center-what-0-167-0-changes-when-you-run-several-agents?utm_source=hashnode&utm_medium=feed) Codex CLI 0.167.0 adds an agent command center: one view for every running agent, unread results marked, drafts kept across backends. 5 min read · [systemdesignsimple.hashnode.dev](https://systemdesignsimple.hashnode.dev/codex-cli-agent-command-center-what-0-167-0-changes-when-you-run-several-agents?utm_source=hashnode&utm_medium=feed) [2d ago](https://hashnode.com/posts/codex-cli-agent-command-center-what-0-167-0-changes-when-you-run-several-agents/6af134c64bef8c58ae676058) ### [How to create an AI agent skill with one SKILL.md file](https://systemdesignsimple.hashnode.dev/how-to-create-an-ai-agent-skill-with-one-skill-md-file?utm_source=hashnode&utm_medium=feed) An agent skill is one folder with a SKILL.md file. The one-line description decides when it loads. How we run 23 skills with two agents. 6 min read · [systemdesignsimple.hashnode.dev](https://systemdesignsimple.hashnode.dev/how-to-create-an-ai-agent-skill-with-one-skill-md-file?utm_source=hashnode&utm_medium=feed) [2d ago](https://hashnode.com/posts/how-to-create-an-ai-agent-skill-with-one-skill-md-file/6af1345c996a195ed4fd5079) ### [Codex CLI background server: check it and turn it off](https://systemdesignsimple.hashnode.dev/codex-cli-background-server-check-it-and-turn-it-off?utm_source=hashnode&utm_medium=feed) Since Codex CLI 0.157.0 a session can start a background server. Three checks to see it (338 MB here) and one command to turn it off. 6 min read · [systemdesignsimple.hashnode.dev](https://systemdesignsimple.hashnode.dev/codex-cli-background-server-check-it-and-turn-it-off?utm_source=hashnode&utm_medium=feed) [2d ago](https://hashnode.com/posts/codex-cli-background-server-check-it-and-turn-it-off/6af133b5996a195ed4fb736e) ### [Server failover: active-passive vs active-active](https://systemdesignsimple.hashnode.dev/server-failover-active-passive-vs-active-active?utm_source=hashnode&utm_medium=feed) Our failover simulation: active-passive lost 111 requests waiting for three 1 s probes; active-active lost 1. Why, and what it costs. 10 min read · [systemdesignsimple.hashnode.dev](https://systemdesignsimple.hashnode.dev/server-failover-active-passive-vs-active-active?utm_source=hashnode&utm_medium=feed) [1](https://hashnode.com/posts/server-failover-active-passive-vs-active-active/6af13306996a195ed4f96a87) [2d ago](https://hashnode.com/posts/server-failover-active-passive-vs-active-active/6af13306996a195ed4f96a87)