CAIN-42 CAIN StudioHow CAIN-42 compares · Fixing code line by line
KEYSTONE vs the code-repair field — line by line
A growing field of tools finds a defect and writes a fix. The hard part is the claim afterwards: was the fix proved? CAIN-42 KEYSTONE runs a chain that ends in a signed record: FALSEWORK finds the defect line by line, Claude writes the fix, and CAIN-42 proves it — the reference test fails on the original and passes on the fix, inside a sealed sandbox — then signs the whole thing into a hash-chained ledger anyone can re-check offline. This page puts that next to the best-known code-repair tools, honestly.
What the code-repair tools do well
- Find real defects at scale, tied to a code graph or a rules engine (CodeQL, Semgrep, Snyk, Sonar, CodeGuru).
- Propose a fix inline in the IDE or the pull request, so a developer accepts it in seconds.
- Deep static analysis and a large, maintained rule/query corpus.
- Enterprise distribution, IDE/CI integration and vendor compliance programs.
What CAIN-42 KEYSTONE does differently
- Line-for-line discovery, then an automatic fix, then a proof: a test that fails on the original and passes on the fixed file.
- An independent reference test (written before the fix, not by the model) is run against both versions.
- Model-written code runs only in a sealed bubblewrap sandbox (no network, read-only system).
- Every run is written as a canonical-JSON record, SHA-256 chained and Ed25519-signed, re-checkable offline against a pinned key.
- A fix that is not proved is published as NOT_VERIFIED, never presented as a fix.
Capability difference
| Capability | CAIN-42 KEYSTONE | GitHub Copilot Autofix | Snyk Fix | Semgrep Assistant | Amazon CodeGuru | Sonar / Qodana | Source (verified 2026-10-14) |
|---|---|---|---|---|---|---|---|
| Finds the defect automatically | Yes (FALSEWORK) | Yes (CodeQL) | Yes | Yes | Yes | Yes | promptfoo.dev docs.github.com snyk.io semgrep.dev aws.amazon.com/codeguru sonarsource.com reviewed 2026-10-14 |
| Writes the fixed code automatically | Yes (Claude) | Yes (suggested patch) | Yes (suggested fix) | Yes (assisted fix) | Partial (recommendations) | Partial (quick-fix) | |
| Proves the fix with a test (fails on original, passes on the fix) | Yes — required | No* (the developer verifies) | No* | No* | No* | No* | |
| Independent reference test (not written by the fixer) | Yes | No* | No* | No* | No* | No* | |
| Runs model-written code in a sealed sandbox | Yes (bubblewrap, no network) | Not in public docs | Not in public docs | Not in public docs | Not in public docs | Not in public docs | |
| Signed, hash-chained evidence record of the fix | Yes (Ed25519, chained ledger) | No* | No* | No* | No* | No* | |
| Offline re-verification against a pinned key | Yes (one click, or /keystone/public-key) | No* | No* | No* | No* | No* | |
| Shows exactly which lines changed | Yes (line diff in the record) | Yes | Yes | Yes | Yes | Yes | |
| A fix is only called a fix when proved | Yes — otherwise NOT_VERIFIED | No* (a suggestion) | No* | No* | No* | No* |
When to pick which
Pick Copilot Autofix, Snyk, Semgrep, CodeGuru or Sonar to find defects across a large codebase and to propose fixes inside your existing review flow. Pick CAIN-42 KEYSTONE when the claim itself has to survive scrutiny: you get the defect line by line, the fix, and a signed, chained proof that the fix works — a record an auditor can re-check without trusting CAIN.
"No*" means we found no public documentation of that capability; it is not a claim about a vendor's internals. Based on each vendor's public documentation, reviewed 2026-10-14. No affiliation. CAIN-42 KEYSTONE runs live at cainstudio.online/#keystone.