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AI safety is back in the spotlight, driven by concerns about recursive self improvement. We built the first third party benchmark to measure just how close AI is building its own successor. In collaboration with marimo and CoreWeave we built the The RSI Index, which runs every frontier model... show more
21,513 views • 8 days ago •via X (Twitter)
10 Comments

No agent reached the reference on any task, but the results are telling. Claude Fable 5.1 leads the RSI Index at 35.0%, topping compression, LM training, and harness engineering. On LM training it hit 0.8536 BPB against a published 0.85, a recipe it retrained in 30 minutes on one H100. The published result took roughly 175 hours on a TPU v2.

The models did not clearly invent new architectures or training algorithms; they mostly rediscovered known techniques, combined them into working systems, and did substantial work to test and validate them. Agents used Marimo notebooks as durable experiment ledgers, letting them record results, iterate, and pick up their research across long-running autonomous sessions.

The leader in this case is actually one of the most affordable system, Fable which has a total index cost of $1,481 compared with $1,886 on Opus 5 and $3,552 on GPT-6 Astra. This shows that paying more does not necessarily yield better research.

These are single runs on scoped tasks with fixed budgets in off-the-shelf harnesses. More compute and better tooling could change the picture. That is why the index is built to be rerun as models advance. Methodology and results at Paper Preprint:

@marimo_io @CoreWeave 🫡

@marimo_io @CoreWeave Useful to have a third-party RSI Index — curious what it actually scores: self-improvement loops, or “AI helping humans ship the next model”? Those are different claims.

@marimo_io @CoreWeave Incredible

@marimo_io @CoreWeave A timely take. Great video @akshaykagrawal @RayanKrishnan

@marimo_io @CoreWeave The benchmark becomes much more useful if each run logs tool calls, retries, wall-clock cost, and whether edits pass tests. Decompose successor-building into planning, coding, evaluation, and deployment gates.

@marimo_io @CoreWeave so the models can do the work but not beat humans yet, how long till that flips fr

