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v0.0.20

pydantic/montyv0.0.20Aug 9, 2026by samuelcolvin

AI Summary

This release introduces substantial functionality to the Monty sandbox, including native support for standard library modules like `collections`, `itertools`, and filesystem operations (`os`). It also features significant memory management improvements, garbage collection enhancements, and security fixes regarding mount confinement.

Key Highlights

  • Native support for `os` module operations and `collections` (deque, namedtuple, etc.)
  • Implementation of `itertools` foundation and adaptors (count, repeat, pairwise, etc.)
  • Memory management improvements including soft memory limits and shrinking heap data
  • Refactoring of binary operators onto `PyTrait` and native `@dataclass` support
  • Security enhancements via mount confinement fixes and path validation

Breaking Changes

  • Remove the `ResourceTracker` generic, always use `ResourceTracker`

New Features

  • Support function decorators
  • Support Path / Path and reflected str / Path in the `/` operator
  • Implement `NotImplemented` and use it for user equality
  • Implement file handle API for TS
  • Add `collections` modules
  • Add `itertools` foundation with `count` and `repeat`
  • Add `itertools` adaptors: `pairwise`, `compress`, `islice`, `chain`, `cycle`
  • Native `@dataclass` defined inside the sandbox
  • Add `ShutdownDump` turn-ender

Full Release Notes

## What's Changed
* Populate class `__annotations__` (stringized) by @rewitt94 in https://github.com/pydantic/monty/pull/593
* tidy up max allocations remnants by @davidhewitt in https://github.com/pydantic/monty/pull/618
* fix `npm audit` warnings in `monty js` by @davidhewitt in https://github.com/pydantic/monty/pull/617
* Remove the `ResourceTracker` generic, always use `ResourceTracker` by @samuelcolvin in https://github.com/pydantic/monty/pull/613
* Track iterator types for GC so their cycles can't evade collection by @rewitt94 in https://github.com/pydantic/monty/pull/620
* Support function decorators by @rewitt94 in https://github.com/pydantic/monty/pull/590
* Support Path / Path and reflected str / Path in the / operator by @samuelcolvin in https://github.com/pydantic/monty/pull/621
* Update yanked spin 0.9.8 -> 0.9.9 and 0.10.0 -> 0.10.1 in Cargo.lock by @samuelcolvin in https://github.com/pydantic/monty/pull/623
* Bound nesting of class-body expressions walked before parsing by @rewitt94 in https://github.com/pydantic/monty/pull/624
* unify `ExtFunction` types by @davidhewitt in https://github.com/pydantic/monty/pull/598
* create cells for captured comprehension values by @davidhewitt in https://github.com/pydantic/monty/pull/605
* split all binary operators to be proper methods on `PyTrait` by @davidhewitt in https://github.com/pydantic/monty/pull/568
* split `MontyIter` into dedicated iterator types by @davidhewitt in https://github.com/pydantic/monty/pull/602
* implement file handle API for TS by @davidhewitt in https://github.com/pydantic/monty/pull/599
* clean up old opcodes, add dump version at the Rust level by @davidhewitt in https://github.com/pydantic/monty/pull/607
* Dispatch user-defined `__iter__` / `__next__` / `__contains__` by @rewitt94 in https://github.com/pydantic/monty/pull/609
* Count the module's pending result in the strict ref-count check by @rewitt94 in https://github.com/pydantic/monty/pull/627
* Move `py_contains` onto `PyTrait`, fix `in` for bytes, add coverage by @rewitt94 in https://github.com/pydantic/monty/pull/625
* Implement `os.listdir` and filesystem wrappers in the os module by @samuelcolvin in https://github.com/pydantic/monty/pull/622
* Fix remaining `py_contains` issues from the #625 review by @rewitt94 in https://github.com/pydantic/monty/pull/628
* Add a `ShutdownDump` turn-ender and cheap frame classification by @samuelcolvin in https://github.com/pydantic/monty/pull/630
* Add `itertools` foundation with `count` and `repeat` by @rewitt94 in https://github.com/pydantic/monty/pull/632
* cleanups to some drop branches by @davidhewitt in https://github.com/pydantic/monty/pull/633
* Native `@dataclass` defined inside the sandbox by @rewitt94 in https://github.com/pydantic/monty/pull/626
* Add `collections`: deque, namedtuple, defaultdict, Counter by @rewitt94 in https://github.com/pydantic/monty/pull/608
* Bound the source-pattern text retained by the regex cache by @samuelcolvin in https://github.com/pydantic/monty/pull/644
* Bound native dataclass equality by the recursion-depth limit by @rewitt94 in https://github.com/pydantic/monty/pull/641
* Make monty-pool async end-to-end by @samuelcolvin in https://github.com/pydantic/monty/pull/639
* Refactor try/finally compilation onto a CPython-style frame-block stack by @samuelcolvin in https://github.com/pydantic/monty/pull/648
* Review Skills by @samuelcolvin in https://github.com/pydantic/monty/pull/651
* make benchmarks async properly by @davidhewitt in https://github.com/pydantic/monty/pull/652
* Shrink `HeapData` from 160 to 80 bytes by boxing large variants by @samuelcolvin in https://github.com/pydantic/monty/pull/636
* Apply new drop standards to the collections code by @rewitt94 in https://github.com/pydantic/monty/pull/653
* Add `itertools` adaptors: `pairwise`, `compress`, `islice`, `chain`, `cycle` by @rewitt94 in https://github.com/pydantic/monty/pull/635
* move `py_set_attr` onto `PyTrait` by @davidhewitt in https://github.com/pydantic/monty/pull/638
* implement `NotImplemented` and use it for user equality by @davidhewitt in https://github.com/pydantic/monty/pull/567
* Make bytes substring search linear and interruptible by @rewitt94 in https://github.com/pydantic/monty/pull/643
* Apply memory limit via custom allocator by @samuelcolvin in https://github.com/pydantic/monty/pull/646
* Windows path-parsing mount escape by @rewitt94 in https://github.com/pydantic/monty/pull/655
* attempt to configure telemetry via bindings or monty-runtime logfire by @davidhewitt in https://github.com/pydantic/monty/pull/662
* Re-validate cached overlay host paths on every read by @rewitt94 in https://github.com/pydantic/monty/pull/656
* Memory limit followups by @samuelcolvin in https://github.com/pydantic/monty/pull/667
* move to soft memory limit in allocator by @davidhewitt in https://github.com/pydantic/monty/pull/668
* vendor abc.pyi so `@abstractmethod` members keep their types by @samuelcolvin in https://github.com/pydantic/monty/pull/671
* Cleanup typechecking by @samuelcolvin in https://github.com/pydantic/monty/pull/674
* uprev pyo3 to 0.29.2 by @samuelcolvin in https://github.com/pydantic/monty/pull/675
* Fix test_type_check_format_not_a_string against pyo3 0.29.2 by @rewitt94 in https://github.com/pydantic/monty/pull/677
* Add Macroscope review config (correctness tuning, ignore, approvability) by @strawgate in https://github.com/pydantic/monty/pull/679
* Confine mounts with cap-std descriptors instead of path checks by @rewitt94 in https://github.com/pydantic/monty/pull/669
* Mount confinement defects by @samuelcolvin in https://github.com/pydantic/monty/pull/680
* Close the mount defects the confinement PR deferred by @samuelcolvin in https://github.com/pydantic/monty/pull/681
* Drop `logfire` from CLI by default by @samuelcolvin in https://github.com/pydantic/monty/pull/683
* Split `pydantic-monty` into a metapackage over client and runtime by @samuelcolvin in https://github.com/pydantic/monty/pull/678
* Stop mount path walks costing a lookup per level squared by @samuelcolvin in https://github.com/pydantic/monty/pull/684
* Add raw wire-level turns to monty-pool, bump logfire to 0.12 by @samuelcolvin in https://github.com/pydantic/monty/pull/687
* Remove the peek module by @samuelcolvin in https://github.com/pydantic/monty/pull/688
* Move monty version to types by @samuelcolvin in https://github.com/pydantic/monty/pull/689
* Bound nested itertools adaptors by the recursion limit by @samuelcolvin in https://github.com/pydantic/monty/pull/685
* rename files to `mod.rs`, stop annoying `usize_field` warnings by @samuelcolvin in https://github.com/pydantic/monty/pull/690
* Collapse the two dump versions into one session dump format by @samuelcolvin in https://github.com/pydantic/monty/pull/692
* Send a WebSocket Close frame on worker teardown by @samuelcolvin in https://github.com/pydantic/monty/pull/691
* Ci split `test-rust` by @samuelcolvin in https://github.com/pydantic/monty/pull/694
* Version the wire protocol independently of the package by @samuelcolvin in https://github.com/pydantic/monty/pull/693
* Bump version to v0.0.20 by @samuelcolvin in https://github.com/pydantic/monty/pull/695


**Full Changelog**: https://github.com/pydantic/monty/compare/v0.0.19...v0.0.20