Spotify cut Claude Code tokens 90% with a 350-line routing rule, not a model breakthrough

krishnan · x · 2026-09-08

krishnan breaks down how Spotify achieved 90% token savings in Claude Code via routing, not modeling: its Shunt plugin acts as a pre-tool hook that intercepts tool calls—untargeted reads over 350 lines are blocked and rerouted to a cheaper worker model via Portal, while targeted reads still reach Claude and predictable code generation writes straight to disk without consuming context.

The key insight: asking a model to route itself is a suggestion, but a pre-tool hook is an enforced economic policy—reserving expensive reasoning for debugging, architecture, and other judgment-heavy work.

Caveat: the reported 90% is mean bulk-read token savings across four scenarios in a Java monorepo, not a 90% cut in total engineering cost, and delegation adds 10–30 seconds of latency.

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Spotify cut Claude Code tokens 90% with a 350-line routing rule, not a model breakthrough

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