Issues

• LEAN_SCALAR_PTR_LITERAL truncates static scalar fields on 32-bit targets other than Emscripten

  leanprover/lean4#15814 · Filter by author basvandijk opened on Oct 20, 2026

• Lake: dynamically constructed build cycle is not detected and hangs

  bug
  leanprover/lean4#15810 · Filter by author dranov opened on Oct 20, 2026

• Lake: concurrent fetch from running jobs builds the same target more than once

  bug
  leanprover/lean4#15809 · Filter by author dranov opened on Oct 20, 2026

• Lake: collectArray, mixArray, collectVector, collectList, and mixList are quadratic

  bug
  leanprover/lean4#15808 · Filter by author dranov opened on Oct 20, 2026

• Windows: intermittent stack-cookie failure (0xC0000409) in uv__tcp_connect with Std.Async.TCP connect

  leanprover/lean4#15807 · Filter by author gijzelaerr opened on Oct 20, 2026

• RFC: evaluator-owned accepted statements for conditional Comparator matches

  leanprover/lean4#15800 · Filter by author kimihiro64 opened on Oct 19, 2026
  3

• Internal grind error: mkEqProof invoked with terms of different types

  bug
  leanprover/lean4#15799 · Filter by author BrunoDutertre opened on Oct 19, 2026

• Lake: transDeps misses a transitive dependency (and its extern_lib) depending on the order of requires

  bug
  leanprover/lean4#15798 · Filter by author kmrasmussen opened on Oct 19, 2026

• grind? drops a premise it used in calculating its premise list

  leanprover/lean4#15778 · Filter by author jessealama opened on Oct 19, 2026

• Partial fixpoints do not generalize arguments properly in a module

  bug
  leanprover/lean4#15777 · Filter by author hgoldstein95 opened on Oct 19, 2026
  1

• Instance search: pruning an instance-typed mvar under a binder is rejected (regression from #14624)

  bug
  leanprover/lean4#15776 · Filter by author lzy0505 opened on Oct 19, 2026

• Constructor reuse regression due to JpCases change

  bug
  leanprover/lean4#15771 · Filter by author szch79 opened on Oct 19, 2026
  1

• RFC: Wait on a C library's socket in Std.Async

  leanprover/lean4#15769 · Filter by author ChristianMurphy opened on Oct 19, 2026

• initialize of a function-typed constant: initialiser is skipped in compiled code and every call reaches unreachable (or an undefined symbol)

  bug
  leanprover/lean4#15768 · Filter by author chrisdwalton opened on Oct 18, 2026

• lake update --keep-toolchain lets a dependency's manifest override the root package's own require

  bug
  leanprover/lean4#15761 · Filter by author paulbutcher opened on Oct 18, 2026

• Sym rewrite proofs re-evaluate match discriminants when preprocessing changes the rule statement

  bug
  leanprover/lean4#15759 · Filter by author Kha opened on Oct 18, 2026

• set_option trace.Elab.info true on some antiquotation leads to Error pretty printing syntax: Unknown constant ident.antiquot.

  bug
  leanprover/lean4#15757 · Filter by author user202729 opened on Oct 18, 2026

• RFC: native Windows support for lake check sandboxing

  leanprover/lean4#15756 · Filter by author Puthranps opened on Oct 18, 2026
  1

• simp generates and tries every match equation on a stuck match, which is quadratic and bloats .olean files

  leanprover/lean4#15754 · Filter by author kevaundray opened on Oct 18, 2026

• "Cannot derive functional induction principle … still depends on" when a match is wrapped in an applied lambda and recurses under >>=

  bug
  leanprover/lean4#15749 · Filter by author josevalim opened on Oct 17, 2026
  1

• Boxed scalar closed terms are initialized eagerly at module initialization, so code in branches that are never taken runs before main

  bug
  leanprover/lean4#15746 · Filter by author hexdrift-ctrl opened on Oct 17, 2026

• segfault @[try_suggestion] accepts a suggester whose type gained section variables in a mutual block

  bug
  leanprover/lean4#15744 · Filter by author YuanchengJiang opened on Oct 16, 2026

• mkValueTypeClosure type-checks closed terms when the local context has a let

  bug
  leanprover/lean4#15742 · Filter by author Kha opened on Oct 16, 2026

• building 4.35 now requires git checkout for lean4lean

  leanprover/lean4#15741 · Filter by author juhp opened on Oct 16, 2026
  4

• Equation lemmas fail to generate for structural recursion through match on the decreasing argument and a value bound by a monadic bind

  leanprover/lean4#15735 · Filter by author nomeata opened on Oct 16, 2026