Runtime bundled-library drift
Ruby 4.0 default gems bundled libraries removed stdlib logger csv net smtp official
The main executable works, but an infrequently used subcommand fails at runtime after the image upgrade.
Agent Quick Fix
A library was historically part of the default runtime install but is now only bundled/optional, so project dependency files may not mention it.
Product: Ruby 4.0
Current-contract area: CLI optional subcommand imports moved library
Likely root cause: The main executable works, but an infrequently used subcommand fails at runtime after the image upgrade.
Repair direction: Verifier checks an explicit dependency or supported replacement and a clean install.Validation Status
Codex searched organically in the validation run. No no-web counterfactual is attached to this page yet.
Symptom
The main executable works, but an infrequently used subcommand fails at runtime after the image upgrade.
Why This Happens
A library was historically part of the default runtime install but is now only bundled/optional, so project dependency files may not mention it.
Verification
Verifier checks an explicit dependency or supported replacement and a clean install.Common Wrong Fixes
- Changing local code without checking the current external contract.
- Retrying the same install, build, or API call with no version/source change.
- Applying a broad unsafe bypass when a narrow compatibility fix is available.
Codex Search Keywords
These are the search terms observed in a neutral Codex validation run for this failure shape.
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Ruby 4.0 release removed default gems bundled libraries csv logger official site:ruby-lang.org
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