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Rails Drops 6.1 Marshal Format, Modernizes Rack Guide
By RepoJournal · Filed · About Rails · Composed from the cited sources · methodology
2 people shipped this
Rails is removing support for the 6.1 Active Record Marshal format to unlock faster evolution of internal object representation without compatibility constraints.
The Rails core team merged the decision to stop deserializing Rails 6.1 serialized records [2], a breaking change that simplifies the codebase and removes a maintenance burden that was blocking architectural improvements to Active Record's Attribute and AttributeSet internals [3]. This won't affect most applications since serialized records from that era are rare in production, but if you're still passing Marshal data between process boundaries, plan a migration away from that pattern before upgrading to the next major release. On the documentation front, Rails shipped a comprehensive overhaul of the Rack guide [1], adding sections on custom middleware integration and advanced Rack API usage alongside clarifications on the default middleware stack. The guide restructure aligns Rails documentation with the Configuration guide format, making it easier to navigate. A separate fix ensures Active Record attachment changes survive STI class conversions [4], addressing a longstanding bug where metadata would be silently lost during polymorphic record transformations.
Action items
- → Audit your application for Rails 6.1 Marshal serialized records before the next major upgrade rails/rails [plan]
- → Review the updated Rack guide if you use custom middleware or Rack API directly rails/rails [monitor]
- → Verify STI record attachment changes are now persisted correctly in your test suite rails/rails [monitor]
References
- [1] [RF-Docs] [ci-skip] Update the Rails on Rack guide ↗ rails/rails
- [2] Remove support for Rails 6.1 Active Record Marshal format rails/rails ↗
- [3] Merge pull request #57382 from byroot/remove-ar-marshal-6.1 rails/rails ↗
- [4] Preserve attachment changes when converting record to another class using STI ↗ rails/rails
