C#

"I've never seen anything scarier than an LLM with tool calls." — Erik Meijer aka @HeadinTheBox

Jul 13, 2026 · 21:13

Erik Meijer of Leibniz Labs argues that AI agents with tool calls are intrinsically dangerous and must be tamed through formal verification. He recounts how adding tool calls to LLMs turned harmless chatbots into agents capable of irreversible side effects, like deleting files or emptying bank accounts. His solution, implemented in Automind, uses proof-carrying code: the agent submits a plan as a program (Free Monad) together with a machine-checkable safety proof, and a small checker verifies the proof before allowing execution. This air-gaps the agent from its tools, ensuring policy compliance statically. Meijer demonstrates that elementary type systems and compiler techniques, such as taint analysis on program expressions, can provably prevent unsafe actions, turning agents from 'vibe-coding' risks into provably safe systems.

Teaching Coding Agents to do Spreadsheets - Nuno Campos, Witan Labs

Jul 8, 2026 · 19:09

Nuno Campos from Witan Labs explains how his team spent four months teaching coding agents to master spreadsheets, raising accuracy from 50% to 92% on a financial analysis benchmark. Key failures included a rigid three-agent architecture and standalone representations like SQL and XML. The breakthrough was replacing 15 separate tools with a single JavaScript repo tool offering persistent state and code-mode semantics, enabling agents to combine multiple operations in one call and drastically reduce timeouts. The team built high-fidelity formula and rendering engines to close the verification loop, and added domain knowledge prompts to focus the model. For evaluation, they moved from LLM-as-judge to deterministic comparisons using golden spreadsheets. Campos urges practitioners to replace many tool calls with real scripting languages, invest in feedback loops, and regularly revisit interfaces as model capabilities evolve.