Show HN: 'behaviour-preserving' AI refactors were not
When they disagree it hands you the exact input that separates them. The seven channels Return value · exception raised · warnings · stdout · stderr · argument mutation · object state. A narrow definition of behaviour does not under-report, it lies, because whatever sits outside the definition comes back as no_change.
- ▪When they disagree it hands you the exact input that separates them.
- ▪The seven channels Return value · exception raised · warnings · stdout · stderr · argument mutation · object state.
- ▪A narrow definition of behaviour does not under-report, it lies, because whatever sits outside the definition comes back as no_change.
Hacker News (AI / LLM) files mainly under ai. We currently carry 4,683 of its stories.
Story provenance
Source · retrieval · rights · ranking — open for full record
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Story provenance
Attribution is not the same as permission. This drawer separates discovery metadata, excerpts, WeSearch-generated summaries, reuse status, and whether the publisher receives the visit. Nothing here claims a legal grant the publisher has not made.
Record
| Original publisher | GitHub |
| Canonical URL | https://github.com/runboth/runboth |
| Publication time | Sun, 13 Sep 2026 17:40:16 +0000 |
| Retrieval time | 2026-09-13T17:46:50.681Z |
| Last seen | 2026-09-13T17:46:50.681Z |
| Headline source | Publisher (no WeSearch rewrite) |
| Excerpt source | publisher body |
| Excerpt method | First ~120 words (~800 chars) of extracted publisher body, fair-use limited. |
| Summary | WeSearch · cerebras-chat (WeSearch summarizer) |
| Summary source text | contentText |
| Citation coverage | Summary is a WeSearch-generated derivative; primary citation is the original publisher URL. |
| Cluster | v8Sj8j496Y_g · 1 stories |
| Cluster logic | Grouped by semantic title/content similarity across sources within a rolling window. Same-publisher template collisions are excluded from coverage comparison. |
| Ranking reason | Story pages are not engagement-ranked. Hub feeds use recency, with optional source-diversified chronological ordering (cap consecutive stories per source). No personalized ranking. |
| Publisher visit | Yes — open original |
| Substitutes article? | No — link-out required for full text |
Rights status (four layers)
WeSearch handling by dimension
| Indexing | May the item be indexed (stored, ranked, made findable)? | Allowed |
| Snippet | May a short excerpt of the publisher's text be shown? | Allowed |
| AI summary | May WeSearch generate its own short summary of the article? | Limited |
| Retrieval / RAG | May the content be exposed for third-party retrieval-augmented generation? | Not asserted |
| Model training | May the content be used to train AI models? | Not asserted |
| Commercial reuse | May the content be reused commercially? | Not permitted |
Basis: Derived from the published RSS/Atom feed. Contact: [email protected]. Reviewed: 2026-07-24.
Opening excerpt (first ~120 words) tap to expand
RunBoth An AI changed your code. RunBoth runs both versions and tells you what actually behaves differently, including the functions nobody touched. runboth.dev · How it works · Red team results $ git commit -m "refactor: tidy up the rates module" BLOCKED: the behaviour changed and your message does not say so. rate(100) used to: return 0.1 now: return 0.0 AND 1 function you did NOT touch now behaves differently, because it calls what you changed: total(2.5, 100) pkg/invoice.py used to: return 225.0 now: return 250.0 What it does It checks out both versions of your code, generates inputs for every changed function from its signature and from the constants mined out of its own bytecode, runs both versions in separate sandboxed subprocesses, and compares seven observation channels.
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Excerpt limited to ~120 words for fair-use compliance. The full article is at GitHub.