Tsolmondorj Natsagdorj — security & systems
I'm Tsolmondorj Natsagdorj (0xSoftBoi). I work on cross-chain infrastructure, smart-contract security, and the machine learning pointed at both — and I'm partial to the one accounting bug that lets a bridge print money.
Writing
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Who audits the auditor?
I built a Solidity static-analysis tool with an agent fleet. The phase that mattered wasn't writing the detectors — it was pointing a separate model at them and saying: lie detector, prove you lie.
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An arbitrage bot with no slippage is a sandwich
I rebuilt a 2021 flash-loan hackathon contract into a real Aave v3 arbitrage. The contract got the hard security right — and left the door open on the thing arb bots exist to exploit.
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Running an OP Stack L2 with reth
An OP Stack rollup is four processes and a shared secret. I finalized an old deployment of mine into something reproducible — and the part that actually caught bugs wasn't me, it was CI.
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Rebuilding a perps DEX from its docs
An old repo of mine had a perps-DEX frontend and nothing else — the protocol was gone. So I rebuilt it from the documentation of what it became. The interesting part is what the docs gave away: who the house is.
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A social-good protocol, built by an agent fleet
I had an empty repo and pointed a multi-agent workflow at it. The result was a tested rewards protocol — but the part worth writing down is which model sat in which seat, and the bug the auditor caught that the builde...
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The index fund that held the wrong asset
A Sui Move 'crypto index fund' lets you deposit SUI for exposure to a BTC/ETH/XRP/ADA/MATIC basket. The problem: it never buys any of them. It holds SUI and pays out basket gains it doesn't have — insolvent by constru...
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Anatomy of a memecoin honeypot
A token contract I found trades perfectly and looks like every other ERC-20. It also lets the deployer freeze your bag with one call. Here's the line that does it, proven against the real contract — and what an un-rug...
23 posts in all — browse the archive or by series.
Selected work
- alloymerged — fixed EIP-712 canonicalization to allow self-referential struct types in
dyn-abi. alloy is the Ethereum Rust library behind Foundry and Reth. - uutils/coreutilsmerged — corrected
datetimezone re-zoning in the Rust rewrite of GNU coreutils. - Suwappu — an agent-native cross-chain DEX with a post-quantum bridge (ML-DSA-65). I designed the custody layer and audited it end-to-end with Foundry invariants, Slither and Halmos.
- BRIDGE-bench (anthropic-fellowship)research — measuring LLM reasoning against real DeFi exploits: static analysis scores ~0% F1 on compositional bridge hacks; a static-pre-filtered LLM reaches ~40%. Also a TransformerLens mech-interp replication suite.
- gnome-materials — GNoME-style active learning for materials discovery on a pretrained CHGNet potential: 95% top-100 recall on a 20% labeling budget.
- sensorforge — a robotics monorepo: iPhone/ARKit sensor capture, a Jetson Orin voice assistant, and an active-inference engine.
- quantgroup — a constant-product AMM annotated for auditors: attack simulations and stateful invariant tests.
More open-source work — candle, polars, mlx-lm — and projects on github. Background on the about page.