What they did
The poster, u/This_Cell_1829, was reading NASA TESS telescope data with Claude Code when one star showed a repeating dip. They had Claude Code (on Opus 5.5 and Fable 5.1) download and parse the TESS data, write the transit search, fit the transits, check neighbouring stars, hunt for secondary eclipses and other false positives, make plots, and rerun work when a check failed. The poster set the questions, the tests and the pass or fail rules. Independent reviews came from Codex and from fresh Claude sessions given read-only access. Over about two weeks this became 74 separate analyses and more than 1,000 scripts. They also had the agent search 36 catalogues and 340,505 automatic TESS alerts to see whether the signal had already been reported.
How it went
The signal survived: a roughly 0.05 percent dip every 3.18 days, lasting about two hours, present in TESS observations from 2018, 2020 and late 2025, implying a body about 1.4 Earth radii if it is a planet. A hold-out test that hid one year of data and predicted its transits from the other two passed three times out of three. One audit caught a statistical claim that was overstated, so the poster withdrew it and redid that part. A weaker second candidate at 11.13 days is being treated separately. A TESS observing proposal for two-minute cadence was approved as program 100 for October 31 to November 26, and the poster preregistered the predicted transit times on Zenodo before that data exists.
Worth knowing
This is a candidate, not a confirmed planet, and no astronomer had vouched for it in the HN thread when it hit the front page. HN commenters complained the write-up read as AI-written; the poster admitted on Reddit that parts probably sound that way. The useful lesson the poster gives is to spend the agent's effort on ways to disprove the result, and to have fresh read-only sessions audit the analysis rather than asking the same session whether it is right.
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