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Equation 2 · Part 6 · What Actually Happens Inside a Very Long Claude Context Window

=

Cattn(n)=O(n2⋅d),C_{\mathrm{attn}}(n) = O(n^2 \cdot d),
=

What this part means

The expressions on both sides represent the same quantity under the stated assumptions.

Its job in the formula

The equals sign connects the complete expression on the left with the complete expression on the right. Both sides must have compatible units.

The passage around this formula

Anthropic’s own engineering guidance, published in September 2025 as advice for developers building long-running agents, gives the clearest available first-party account of why context rot happens architecturally rather than treating it as an unexplained empirical curiosity [ 4 ] . The explanation rests on the transformer’s core mechanism: every token attends to every other token in the context through self-attention, so the number of pairwise relationships the model must represent grows with the square of the sequence length. For a context of n tokens, the compute spent by self-attention within a single layer scales as Cattn(n)=O(n2⋅d)C_{\mathrm{attn}}(n) = O(n^2 \cdot d). where d is the model’s hidden dimension. Doubling…

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Learn the underlying idea

An equals sign says that the expression on its left and the expression on its right have the same value under the stated definitions and assumptions.

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Sources cited in the surrounding passage

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