trailMETR's 2025 AI slowdown finding generalizes to experienced open-source developers beyond its 16 participants.
Using AI tools caused experienced open-source developers to complete tasks about 20% slower in early 2025.
Statistical robustness of the trial design· for
Issue-level randomization made METR's 246 completed issues, not its 16 developers, the effective sample for estimating the AI slowdown.
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METR's measured AI slowdown remained statistically significant when accounting for developer-level clustering.
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METR's measured AI slowdown is robust across alternative statistical estimators and empirical strategies
METR's measured AI slowdown estimate was similar across alternative outcome estimators, including a naive ratio estimator
Differential issue dropout and attrition do not explain METR's measured AI slowdown
In METR's 2025 randomized controlled trial, using AI tools increased developers' task completion time by 19%
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Setting-specificity of the participants and mechanisms· against
METR's study participants were more deeply familiar with the repositories they worked on than typical experienced open-source developers.
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High repository familiarity and repository size and maturity contributed to the slowdown METR measured.
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AI coding tools speed up less experienced developers or developers working in unfamiliar codebases.
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claim · empirical · derivedA factual claim that rests on inference from other evidence rather than direct observation.constitution →claim page ↗︎
METR's 2025 AI slowdown finding generalizes to experienced open-source developers beyond its 16 participants.
⇄ContestedCredible evidence or argument exists on multiple sides.constitution →credence 0.50Credence, from 0 to 1: the Steward's probability that the claim, as stated, is true. Stated only where a single number is an honest summary; normative and evaluative claims usually carry none.constitution →
1depended on by
this rests on ↓
claimA box is a claim: a single proposition the graph assesses, with its own page and map. Click any claim to centre the map on it.constitution →argumentA pill is an argument: one line of reasoning stating how the claims beneath it combine to bear on the claim above it, for or against. Arguments are not destinations; click their claims to explore.constitution →✓verifiedThe claim traces to reliable primary sources through a clear chain of evidence.constitution →↑supportedEvidence favors the claim, but the chain is incomplete or the sources are secondary.constitution →⇄contestedCredible evidence or argument exists on multiple sides.constitution →○unsupportedNo credible evidence found, though the claim is not contradicted.constitution →✕contradictedAvailable evidence weighs against the claim.constitution →?unknownInsufficient information to assess.constitution →◌unassessedNo current assessment. Attention goes where its expected value is highest and someone funds it; nothing has funded an assessment of this claim yet, and anyone can.constitution →verified factopen questionvalue premisetheoremprizeA double ring marks a claim with a live prize: an amount in owls offered for a machine-checked proof or disproof of its published formal statement. The amount is in the preview and on the claim page; a prize changes nothing about how the claim is assessed or how important it is judged to be.prize rules →⊢machine-checked⊢ marks a claim whose published formal statement has a machine-checked proof or disproof. The checker confirms the proof; the verdict beside it is still the steward's judgment of the claim as worded.prize rules →supportsthis provides evidence for the parentsteward instructions →contradictsthis argues against the parentsteward instructions →assumesbackground the parent's framing takes as givensteward instructions →requiresa load-bearing premise: the parent is false without itsteward instructions →Fig. Detail falls off with distance; every claim is an address.