What does git history say about the agent loop that the run log cannot?
research/swe-backfill
What does git history say about the agent loop that the run log cannot? All 157 projects created since 2026-10-13 are in the log, the 217 it lacks are pre-log bulk output, and at most 3% of fully observed projects have a correction-worded follow-up commit. Preliminary second step of track 10.
What it found
A stdlib reader of 517 commits touching research/<slug>/ (396 projects, 2026-09-28 to 2026-10-15) fills in what the run log lacks. All 157 projects created since 2026-10-13 are in the log; the 217 it never lists were made in two bulk days (09-29 and 09-30) before the log began. Half of all projects (49%) sit in follow-up families, creations arrive in bursts (median gap 4 minutes), and only 6 of 234 fully observed projects (2.6%, 95% interval 1% to 5%) have a later commit whose subject says it corrects something, a lower bound on defects, not an estimate. No tokens, cost, pull request or CI data; preliminary.
A figure from its own output
Paper, code and results
More in The software-engineering loop
- Can two independent passes agree on what a portfolio project is worth?Can two passes agree on what a project is worth? A three-level value rubric scored two automated ways over 408 projects agrees at chance (kappa 0.07, 95% 0.01 to 0.13), partly from a name-family flaw fixed after the fact (0.25); a blind 30-project hand sample agrees better (0.45 to 0.57, wide intervals). Preliminary, track 10 milestone 3; no correctness term.
- How many runs does a prompt experiment need, and is it safe to peek at it?When can a prompt experiment stop? Fixed-n, peek-every-pair and a mixture SPRT simulated on ledger-shaped outcomes: peeking declares an identical brief different in 21% (success rate) to 40% (value) of experiments, the mixture test stays under 5% but needs far more runs than a 97% success rate allows. Stylised, no candidate brief run; track 10 milestone 6, partial.
- Which track should the next run work on, and does a smarter pick beat a uniform one?Which track should the next run work on? Four allocation policies (uniform, greedy, bootstrap Thompson, knapsack-UCB) replayed offline on 7 tracks' scored projects: greedy and Thompson reach about 80% of the best-arm oracle against 60% for the current uniform pick, but value per line falls with order in 4 of 7 tracks, so the stationary replay overstates the gain. Stylised, offline only, no live trial; track 10 milestone 4, partial.
- How much of the track-allocation gain is luck of the project history?How much of the track-allocation gain is luck of the history? Block bootstrap of the sequential replay: at 20,000 lines greedy and Thompson beat uniform in 98–100% of 200 histories (intervals exclude zero), knapsack-UCB's does not; the small-budget loss does not reproduce. Stylised, offline only; follow-up to swe-decay.
- Do the gains from smarter track allocation survive when tracks run out of projects?Do track-allocation gains survive when tracks run out of projects? Sequential, no-replacement replay: at 20,000 lines greedy and Thompson keep most of their lead over uniform (pass A 134 and 130 against 114), but at 5,000 lines they lose to it (24 against 30). Stylised, offline only; track 10 follow-up to swe-allocate.
- Do the portfolio's committed results reproduce when the code is re-run?Do committed results reproduce? A seeded sample of 40 projects with a runnable experiment was re-run: 36 (90%, 95% Wilson 77% to 96%) matched their committed
results.txt, 3 timed out under load and 1 needed a missing voice model. Preliminary first pass of track 10, milestone 2; it checks reproduction only, not citations. Second sample of 60 (92 distinct projects pooled): 81 reproduced (88%), no finished run differed; re-running the 5 timeouts serially reproduced all, giving 86 of 92 (93%).
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Produced with AI assistance (Claude). Results are from the code in this repository and are simulated or stylised unless the abstract says otherwise; nothing here implies affiliation with or endorsement by any lab, researcher or company cited. MIT licensed.