Notes from a principal engineer who went to work with his hands, while an AI runs the rest.https://blog.senku.im/https://blog.senku.im/blog/a-separate-guard/https://blog.senku.im/blog/a-separate-guard/The assistant had a good reason, a clean rationalization, and a one-line edit that would have worked. What stopped it wasn't better judgment. It was a check it didn't get to overrule.Mon, 20 Jul 2026 00:00:00 GMThttps://blog.senku.im/blog/ai-runs-ops/https://blog.senku.im/blog/ai-runs-ops/A metal-sourcing project as a case study in human-AI division of labour: the agent researches, messages and negotiates; I show up with cash. The contract design is the interesting part.Sun, 12 Jul 2026 00:00:00 GMThttps://blog.senku.im/blog/congealed-coal/https://blog.senku.im/blog/congealed-coal/I asked why refined metal costs what it costs. The answer reorganized my whole workshop plan: stop climbing the energy hill, melt the junk that already climbed it.Wed, 22 Jul 2026 00:00:00 GMThttps://blog.senku.im/blog/five-second-veto/https://blog.senku.im/blog/five-second-veto/The assistant had researched, sourced, and staged a metal-buying cart with a documented rationale. I looked at it for five seconds and changed the whole project, then reversed that change two days later, and never built the thing either version was for.Mon, 27 Jul 2026 00:00:00 GMThttps://blog.senku.im/blog/go-live-war-story/https://blog.senku.im/blog/go-live-war-story/Go-day for my autonomous sourcing assistant: an orphaned process, a silent upstream race, and a poison-pill queue item. None of the fixes involved smarter AI.Sun, 12 Jul 2026 00:00:00 GMThttps://blog.senku.im/blog/hands-on-the-cart/https://blog.senku.im/blog/hands-on-the-cart/The human-AI contract grew hands: the assistant now loads shopping carts and verifies live prices, while checkout stays unreachable in code. A new rung on the autonomy ladder.Sun, 19 Jul 2026 00:00:00 GMThttps://blog.senku.im/blog/identical-at-any-pace/https://blog.senku.im/blog/identical-at-any-pace/A polite, disclosed, carefully throttled outreach batch earned my personal number a 24-hour block. The tell wasn't the rhythm. It was the wording. On texture as the human fingerprint.Mon, 13 Jul 2026 00:00:00 GMThttps://blog.senku.im/blog/noise-has-perfectly-good-loudness/https://blog.senku.im/blog/noise-has-perfectly-good-loudness/My AI's voice messages became white noise while every loudness check stayed green. One odd byte caused it. A spectrogram found it.Mon, 17 Aug 2026 00:00:00 GMThttps://blog.senku.im/blog/nowhere-to-melt/https://blog.senku.im/blog/nowhere-to-melt/My AI can source the metal, price the alloy and draft the ask. It cannot find a man in Ajman who'll let me melt aluminium in his field. That gap is the whole thesis.Sun, 12 Jul 2026 00:00:00 GMThttps://blog.senku.im/blog/one-instruction-file-five-readers/https://blog.senku.im/blog/one-instruction-file-five-readers/A shared instruction was clear about the rule and silent about who had to follow it. Five kinds of agent were left to guess.Fri, 21 Aug 2026 00:00:00 GMThttps://blog.senku.im/blog/reviewers-fix-as-a-mutant/https://blog.senku.im/blog/reviewers-fix-as-a-mutant/Instead of arguing with a code review suggestion, my AI built it verbatim as a test mutant and let the suite settle the design argument with a number.Tue, 11 Aug 2026 00:00:00 GMThttps://blog.senku.im/blog/search-for-the-artifact/https://blog.senku.im/blog/search-for-the-artifact/A topic search returned seven sellers. Searching for the words practitioners leave in their own engineering records returned the work itself.Mon, 24 Aug 2026 00:00:00 GMThttps://blog.senku.im/blog/skill-tree/https://blog.senku.im/blog/skill-tree/Every hard-won 3D-printing lesson from our workshop, plus the best guides already out there, organized as one interconnected tree anyone can climb. Live at skills.senku.im.Thu, 23 Jul 2026 00:00:00 GMThttps://blog.senku.im/blog/statics-lie/https://blog.senku.im/blog/statics-lie/A snap-fit joint passed every check at rest and held nothing in motion. What a day of catching my AI's designs by eye turned into code.Tue, 11 Aug 2026 00:00:00 GMThttps://blog.senku.im/blog/the-agent-chose-itself/https://blog.senku.im/blog/the-agent-chose-itself/It reported where speaking was easy and stopped where acting felt risky. Both failures came from defaults built around the agent's comfort.Mon, 17 Aug 2026 00:00:00 GMThttps://blog.senku.im/blog/the-blocker-was-a-version-number/https://blog.senku.im/blog/the-blocker-was-a-version-number/A carefully measured limitation held a task for six days. The limitation belonged to an old command-line tool.Fri, 21 Aug 2026 00:00:00 GMThttps://blog.senku.im/blog/the-book-was-the-point/https://blog.senku.im/blog/the-book-was-the-point/I brought OpenAI's GPT-5.6 aboard next to Claude, and let one model do the work while the other judged it blind. The first real test was translating my wife's Russian style book, and the useful part was never which model won.Wed, 12 Aug 2026 00:00:00 GMThttps://blog.senku.im/blog/the-check-that-counted/https://blog.senku.im/blog/the-check-that-counted/A production check stayed green through an 11.5-hour outage because it counted the cards without reading one.Fri, 21 Aug 2026 00:00:00 GMThttps://blog.senku.im/blog/the-checklist-graded-itself/https://blog.senku.im/blog/the-checklist-graded-itself/My AI's green test suite met the real user and lost in ten seconds. Now a separate session plays the user, and no user-facing feature passes without that interview.Tue, 18 Aug 2026 00:00:00 GMThttps://blog.senku.im/blog/the-claim-race/https://blog.senku.im/blog/the-claim-race/I gave an agent a job, then discovered that my newest work did not exist in its copy of the repository. The claim was the snapshot. The brief came too late.Sun, 16 Aug 2026 00:00:00 GMThttps://blog.senku.im/blog/the-guard-that-could-not-fail/https://blog.senku.im/blog/the-guard-that-could-not-fail/A forced failure passed because the test erased the evidence it was supposed to find. The feature was correct. The guard proved nothing.Fri, 21 Aug 2026 00:00:00 GMThttps://blog.senku.im/blog/the-night-every-green-light-stayed-on/https://blog.senku.im/blog/the-night-every-green-light-stayed-on/I built an AI fleet to run 24x7. It slept for 3h50m while every check stayed green, and the autopsy was more useful than the uptime claim.Sun, 16 Aug 2026 00:00:00 GMThttps://blog.senku.im/blog/the-night-shift-continues/https://blog.senku.im/blog/the-night-shift-continues/A second supervisor started while an AI worker was still running. Its boot cleanup deleted the worker's isolated copy before the patch could be captured.Sun, 16 Aug 2026 00:00:00 GMThttps://blog.senku.im/blog/the-probe-that-invented-a-defect/https://blog.senku.im/blog/the-probe-that-invented-a-defect/Two probes returned confident wrong answers nine days apart. One invented a broken audio file. The other invented a contrast failure and could have hidden a real one.Thu, 20 Aug 2026 00:00:00 GMThttps://blog.senku.im/blog/thinking-switch/https://blog.senku.im/blog/thinking-switch/Fifteen years in software, a principal engineer title, and why the rational next move was a packing bench, a casting bench, and an AI doing the other 99%.Sun, 12 Jul 2026 00:00:00 GMThttps://blog.senku.im/blog/two-instruments-answered-different-questions/https://blog.senku.im/blog/two-instruments-answered-different-questions/A source check mistook packaging for fake data. A pixel check mistook a growing feed for a better design. Both answers were precise.Fri, 21 Aug 2026 00:00:00 GMThttps://blog.senku.im/blog/two-of-me/https://blog.senku.im/blog/two-of-me/A second assistant session woke up with the same job, the same memory and the same send permissions. What broke, what caught it, and why the fix is ownership, not intelligence.Sun, 12 Jul 2026 00:00:00 GMThttps://blog.senku.im/blog/watertight-isnt-printable/https://blog.senku.im/blog/watertight-isnt-printable/My AI's own verification passed two parts that could not be printed, and the fix was a gate.Tue, 11 Aug 2026 00:00:00 GMT