“Insights into Claude Opus 4.5 from Pokémon” by Julian Bradshaw

Dec 10, 2025

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Credit: Nano Banana, with some text provided.

You may be surprised to learn that ClaudePlaysPokemon is still running today, and that Claude still hasn't beaten Pokémon Red, more than half a year after Google proudly announced that Gemini 2.5 Pro beat Pokémon Blue. Indeed, since then, Google and OpenAI models have gone on to beat the longer and more complex Pokémon Crystal, yet Claude has made no real progress on Red since Claude 3.7 Sonnet![1]

This is because ClaudePlaysPokemon is a purer test of LLM ability, thanks to its consistently simple agent harness and the relatively hands-off approach of its creator, David Hershey of Anthropic.[2] When Claudes repeatedly hit brick walls in the form of the Team Rocket Hideout and Erika's Gym for months on end, nothing substantial was done to give Claude a leg up.

But Claude Opus 4.5 has finally broken through those walls, in a way that perhaps validates the chatter that Opus 4.5 is a substantial advancement.

Though, hardly AGI-heralding, as will become clear. What follows are notes on how Claude has improved—or failed to improve—in Opus 4.5, written by a friend of mine who has watched quite a lot of ClaudePlaysPokemon over the past year.[3]

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Outline:

(01:28) Improvements

(01:31) Much Better Vision, Somewhat Better Seeing

(03:05) Attention is All You Need

(04:29) The Object of His Desire

(06:05) A Note

(06:34) Mildly Better Spatial Awareness

(07:27) Better Use of Context Window and Note-keeping to Simulate Memory

(09:00) Self-Correction; Breaks Out of Loops Faster

(10:01) Not Improvements