Our new open-source book on the Principles and Practice of Deep Representation Learning (A Mathematical Theory of Memory) is now posted on the arXiv: https://t.co/EGURnwZr6H I will offer a new graduate course this fall at the University of Hong Kong. Everything will be open sourced!
Most people training agentic LLMs with RL right now have a silently broken training loop and have no idea.
Here's the trap: single-turn RL works beautifully. Clean curves, sane rewards, everything converges. Then you add tools so the model can act mid-rollout, and things get weird. Loss spikes for no reason. Eventually a shape-mismatch error.
The culprit: every time you parse the model's output to detect a tool call, then re-tokenize the updated conversation for the next turn, you're rolling the dice. Usually the round-trip gives back the same tokens. Sometimes it doesn't and your gradient lands on a sequence the model never actually sampled. No crash. Just quietly wrong math and a useless gradient signal.
The fix is one rule: never re-encode tokens you've decoded. Keep the sampled tokens in one buffer, never re-render them, and both failure modes disappear. That's Token-In, Token-Out done right.
Our team just published a beautiful deep-dive on exactly this, including an audit across the major open-weights model families showing most chat templates already support it. Required reading if you're doing multi-turn RL 🤗🔥
https://t.co/zmx0EQl3jM
To learn more about temporal difference learning, you could read the original paper (https://t.co/0cGg3YD4Ws) or watch this video (https://t.co/dOa3rfOPhn).
> be apple
> richest company in the world, every advantage imaginable
> go all in on AI, make countless promises
> get immediately lapped by everyone
> 2 years into the race, nothing to show for it
> give up, write a paper about how it's all fake and gay and doesn't matter anyway
#Earthquake (#sismo) possibly felt 51 sec ago in #California. Felt it? Tell us via:
📱https://t.co/IbUfG7TFOL
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⚠ Automatic crowdsourced detection, not seismically verified yet. More info soon!