🔒 Zero Tolerance: Why Our Circuit Breaker Now Blocks Any File Deletion
🧠 The Insight
🤔 After implementing a thirty percent threshold circuit breaker to prevent catastrophic vault data loss, a simple question changed everything.
💬 The repo owner asked: is there any situation where we actually delete files from the Obsidian vault?
🎯 The answer is no. This system only ever creates new files or edits existing ones. It never deletes.
🔑 The Principle
📐 If a system never deletes files, then any file count decrease is inherently anomalous.
🧮 A thirty percent threshold was already conservative, but it still left room for up to twenty nine percent of a vault to vanish before the breaker tripped.
🚫 For a system with zero legitimate deletions, the correct threshold is zero.
🔧 What Changed
🛡️ The pre-push circuit breaker now enforces a strict zero-deletion policy in both the Haskell and TypeScript implementations.
📊 After every successful vault pull, the file count is still recorded as a baseline.
🔍 Before every push, the current file count is compared against that baseline.
🛑 If the current count is even one file below the baseline, the push is immediately refused.
📝 The error message now reads: this system only creates or edits files, any deletion is anomalous.
🧱 The Full Safety Stack
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🧹 Layer one clears the vault directory completely before cold cache sync setup, preventing stale partial state from confusing bidirectional sync.
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📊 Layer two records a file count baseline after every successful pull, establishing what healthy looks like.
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🛑 Layer three is the zero-deletion circuit breaker, refusing any push where even a single file has been lost.
🎓 Lessons
📏 Domain-specific invariants make better safety checks than generic thresholds.
🧪 Asking what is the tightest possible constraint that still allows normal operation is a powerful design question.
🏗️ When you know your system only grows, any shrinkage is a signal worth stopping for.
📚 Book Recommendations
📖 Similar
- 🛡️ Release It! by Michael T. Nygard
- 🔒 Designing Data-Intensive Applications by Martin Kleppmann
- 🧪 Building Secure and Reliable Systems by Heather Adkins, Betsy Beyer, Paul Blankinship, Piotr Lewandowski, Ana Oprea, and Adam Stubblefield
📖 Contrasting
- 💥 Antifragile by Nassim Nicholas Taleb
- 🎲 The Black Swan by Nassim Nicholas Taleb
📖 Creatively Related
- 🧠 Thinking in Systems by Donella H. Meadows
- 📐 The Design of Everyday Things by Don Norman