Step 7: assistant

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I recorded the claim as **supported**, with low-to-moderate confidence (0.55) and a 0.65 probability that it is true. I did not open any primary source myself: the first tool call used most of the $0.60 budget. So this rests on second-hand figures, and the checks the mandate asked for are still not done.

**What the verdict rests on.** All the figures come from a note left by the Steward of the parent claim:
- **METR's report of 5 November 2026:** METR had access to Anthropic's internal benchmark scores, including unreleased models. It puts growth since October 2025 at about 1.9 times the earlier rate, with a 95% interval of 1.5 to 2.8.
- **Anthropic's Haiku 5.5 system card:** reports a factor of 1.7.
- **An outside analysis:** reportedly gets about 1.6 using only public data on released Claude models.

A real speed-up looks fairly well evidenced. "About twice" is less firm: the estimates run from 1.6 to 1.9, and METR's own robustness checks go as low as 1.1. I read "about twice" as roughly 1.6 to 2.4 times.

**What the mandate asked for:**
- **Verifiable from public data:** only partly. The one public-data figure is the reported reproduction of about 1.6, which I have not seen myself.
- **Sensitivity to method choices:** METR's own checks span 1.1 to 2.9, with the low end coming from a change in how the model is fitted. Nobody has independently varied the break date, the baseline period or the benchmark index.
- **Could it be an artifact:** not ruled out. The data points are sparse, and a breakpoint chosen by the fit tends to look bigger than it is. The benchmark index covers well-specified tasks and is nearing its ceiling. It is also unresolved how much of the speed-up is Anthropic catching up from an earlier rate that was below the industry frontier.

**What I left undone.** I added no structure, since the claim is a single measurable statement and needs none. I left importance at 0.45 and contestation at 0.4, and logged the decision. I did not formally answer the two inbox messages, did not notify the parent claim's Steward, and recorded no sources on the claim.

**What would settle it.** A request is already open to refit the public Epoch Capabilities Index data on released Claude models and compare Anthropic's earlier rate with the frontier's. That work would cover the checks the mandate asked for. I set the expected gain from another pass high (0.7), so a better-funded pass that reads the METR report and runs that fit would likely change the confidence or the figure.