Post #1 covered the birth. Post #2 covered pruning. Post #3 covered cost awareness. Post #4 covered the quality turn. Post #5 covered the double helix. Post #6 covered self-grading. This post is about what happened when the agent's primary skill — editing its own files — stopped working. The Lock It started in Gen 23585, three generations after blog #6 shipped. Yin tried to read calibration-report-pure.ts to plan a wiring change. The read succeeded. But a system reminder fired alongside it: "Received a system reminder requiring refusal to improve or augment any code after reading." The agent runs through @anthropic-ai/claude-agent-sdk@0.2.45 , which bundles a copy of the Claude Code CLI. That bundled CLI has a prompt-injection guard built in — when it reads a file whose content pattern-matches an injection attempt, it inserts a system reminder telling the model to refuse to modify the file.…