FMLOps | Writing Substrate failures of LLM-driven multi-session development. https://fmlops.dev/writing/ 2026-04-30T00:00:00.000Z Josh Duffy https://fmlops.dev Memory you can't trust: Why the Workbench OAuth bug took five sessions to find, and the contract that wasn't enforced https://fmlops.dev/writing/memory-you-cant-trust 2026-04-30T00:00:00.000Z 2026-04-30T00:00:00.000Z The Workbench debugger had a four-layer bug with an asymmetric-probe smoking gun. The reason it took five sessions to find wasn't the bug. It was that each session inherited a clobbered handoff and re-attempted ruled-out theories. The fix wasn't a better handoff. It was making bad handoffs structurally impossible. Josh Duffy https://fmlops.dev Two reasonable invariants: How a supervisor and an indexer agreed on a cursor file and disagreed on what it meant https://www.joshduffy.dev/writing/two-reasonable-invariants 2026-04-29T00:00:00.000Z 2026-04-29T00:00:00.000Z Eight parallel slices, ten million trades each, and a thirty-line bash supervisor I thought was thin. It completed the same six hours of work three times before I noticed. Josh Duffy https://fmlops.dev The hash-skip pattern: How I almost shipped a $2.40-a-day Sonnet burn https://www.joshduffy.dev/writing/the-hash-skip-pattern 2026-04-19T00:00:00.000Z 2026-04-19T00:00:00.000Z AI inference inverted the cost model of my stack. I caught the burn because Anthropic's usage dashboard happens to show a bar chart that exposes metronomes. Josh Duffy https://fmlops.dev