A research lab for off-policy evaluation, exploration, and policy-generated bias in contextual-bandit recommendation systems.
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Updated
Sep 9, 2026 - Python
A research lab for off-policy evaluation, exploration, and policy-generated bias in contextual-bandit recommendation systems.
Closed-loop recommender lab: a model retrains on its own exposure while an exact simulated answer key watches. Logged CTR rose 145.1% while 15 of 16 segments stayed locked on the wrong item; the naive offline reading of a challenger overstated it by 688%, IPS rested on an ESS of 2 of 20000, and the tool's LOW_ESS exit code refuses both.
Off policy evaluation audit for logged bandits: measures how much of a target policy's probability mass sits outside what the log could have produced, shows that a 95 percent interval around the standard estimator covers 0.26 of the time, and returns exit 2 rather than a number when the estimate would be about a different quantity.
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