motoko (moc)

• feat: with --stable-baseline and --enhanced-migration, the migration
  directory is now validated against the migration history the baseline
  records as already applied: a deployed migration that was deleted (unless
  all older ones are deleted too), edited in place, or a local migration
  backdated to sort before the deployed head reports the new M0268
  diagnostic, a warning treated as an error by default (demote with
  -W=M0268, silence with -A=M0268) (#6325).

• bugfix: with --stable-baseline and --enhanced-migration, the M0254/M0267
  check now honors the migrations the baseline records as already applied:
  requirements are computed at the chain's resume point instead of replaying
  the whole chain, and fields the baseline explains no longer warn M0254;
  a field missing from the baseline errors with M0267 naming the resume
  point, while an incompatible one keeps the detailed M0170/M0216
  compatibility errors. Each problem is reported once, and the
  write-a-migration hint is only offered when adding a migration file can
  actually fix the field (#6318).

• bugfix: fixes compilation error on -enabled mixin (#6328).

motoko (moc)

• improvement: RTS weak reference interaction with the incremental GC: weak
  reference reads now go through a load barrier (#6296).

• bugfix: when decoding a Candid blob or text, bound the claimed length (#6311).

motoko (moc)

• feat: Structural implicit derivation now supports variants via the __variant combiner ((Text, () -> E) -> R).
  The synthesized wrapper switches on the active case and applies the combiner to its (tag, payload thunk),
  deriving operations like serialization for any variant whose case payloads have instances (#6192).

• feat: the default maximum for stable memory (--max-stable-pages) is now 100 GiB
  (was 4 GiB), raising the default ceiling for the Region library.
  Override with --max-stable-pages <n> as before (#6279).

• bugfix: implement the new Candid subtyping rule service <actortype> <: principal
  (dfinity/candid#748): service references now decode at type Principal, both when
  decoded directly and in deferred subtype checks on function references (#6275).

• bugfix: a class in expression position lowered to unit instead of its
  constructor (#6291).

• bugfix: a self tail call whose argument is a tuple-returning expression
  crashed the compiler (or miscompiled, with the IR check off) (#6292).

motoko (moc)

• feat: import a local Candid file as a types-only Motoko module via the idl: URI scheme —
  import S "idl:foo.did" exposes S.Self (the service actor type) and named
  Candid types, PascalCased when unambiguous (e.g. user_id → S.UserId). No principal or
  --actor-idl flags required (#6263).

• chore: multi-value Wasm codegen is now always on;
  --(no-)experimental-multi-value are kept for CLI compatibility but have
  no effect (#6266).

motoko (moc)

• feat: the excess-precision warning (M0266) now also covers Float (F64) literals, not just
  Float32, suggesting the shortest round-trip equivalent (#6261).

• feat: --stable-baseline <file.most> with --enhanced-migration escalates unexplained
  "initial actor requires field" cases to error M0267; fields whose baseline type is a
  stable subtype of the required type keep warning M0254 (prototype for legacy→EM
  conversions) (#6249).

• feat: --stable-baseline also runs the same upgrade check as --stable-compatible during
  --check, so tools can typecheck and verify upgrade safety in one moc invocation (#6253).

• fix: refresh the broken docs links in compatibility and stable-memory diagnostics (#6255).

motoko (moc)

• bugfix: --implicit-package=<pkg> was incorrectly using all transitively loaded modules for implicit argument and contextual dot resolution instead of restricting to the given package (#6242).

motoko (moc)

• refactor: simplifies bounds checks for candid decoding in the RTS (#6240).
• fix: fix codegen for nested mixins (#6223).
• deprecation: removed the legacy -multi-value/-no-multi-value flags; --experimental-multi-value and
  --no-experimental-multi-value now warn as deprecated — multi-value Wasm codegen is the default (#6206).

motoko (moc)

• feat: moc now emits the standardized target_features Wasm custom section, so binaryen-based tools (wasm-opt, ic-wasm optimize, dfx's optimize) accept and optimize Motoko output without per-tool feature flags. Previously these tools defaulted to MVP and rejected the multivalue/bulk-memory/memory64 features moc relies on (#6214).

• feat: a Float32 literal written with more precision than the type can hold now warns (M0266), suggesting the shortest equivalent — e.g. 0.123456789 : Float32 → 0.12345679. The surplus digits were already silently discarded by rounding; the warning fires only on genuine excess (minimal literals like 0.1/3.14 stay quiet) (#6198).

• feat: allow requiring system capability for mixin definitions (#6211).
  This makes the capability available in initializers and the mixin body.
  <system> then needs to appear on the corresponding include.

• feat: allow effectful code in transient lets and in actor/mixin bodies with --enhanced-migration (#6191).

• bugfix: --enhanced-migration now also applies to mixins and considers their stable fields when checking migrations (#6183).