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leanprover

32 indexed repositories · View on GitHub

lean4
Lean 4 programming language and theorem prover

Lean · 9227 stars
cslib
The Lean Computer Science Library (CSLib)

Lean · 709 stars
elan
The Lean version manager

Rust · 637 stars
verso
Lean documentation authoring tool

Lean · 384 stars
vscode-lean4
VS Code extension for the Lean 4 programming language and theorem prover

TypeScript · 313 stars
theorem_proving_in_lean4
Theorem Proving in Lean 4

Lean · 272 stars
comparator

Lean · 203 stars
fp-lean
Functional Programming in Lean

Lean · 192 stars
doc-gen4
Document Generator for Lean 4

Lean · 173 stars
reference-manual
The Lean reference manual

Lean · 129 stars
lean4-cli
A Lean 4 library for configuring Command Line Interfaces and parsing command line arguments.

Lean · 120 stars
SampCert
SampCert : Verified Differential Privacy

Lean · 105 stars
reservoir
Package registry for Lean/Lake.

Vue · 50 stars
TensorLib
A verified tensor library in Lean

Lean · 49 stars
lean-eval
Comparator-based Lean formal mathematics eval

Lean · 46 stars
lean-action
GitHub action for standard CI in Lean projects

Shell · 45 stars
lean4export
Plain-text declaration export for Lean 4

Lean · 40 stars
verso-templates
Templates for getting started with Verso

Lean · 38 stars
lean-beam
Claude/Codex skill and local workflow layer for efficient interaction with Lean 4 and Monte-Carlo Tree Search.

Lean · 31 stars
verso-blueprint
Build structured Proof Blueprints with Verso

Lean · 30 stars
12 more repositories live on View on GitHub

Beginner friendly Everything

Open All

RFC: safe withExclusive wrapper around isExclusiveUnsafe Open

RFC

Difficulty 5/5 Over a week Newbie friendliness 35/100

leanprover/lean4#15235 · Opened Sep 20, 2026
`#print axioms` / `collectAxioms` under-reports axioms of imported inductives (in-progress sentinel cached by `exportedAxiomsExt`) Open

bug

Difficulty 4/5 3-5 days Newbie friendliness 48/100

leanprover/lean4#15226 · Opened Sep 19, 2026
OAuth callback returns 503 state_unavailable after successful GitHub authorization (reproducible, 2026-09-18 ~04:05–04:25 UTC) Open

Difficulty 4/5 3-5 days Newbie friendliness 48/100

leanprover/lean-eval-submissions#1739 · 1 comment · Opened Sep 18, 2026
minus function in GettingToKnow/DatatypesPatterns.lean doesn't work Open

Difficulty 1/5 Under an hour Newbie friendliness 92/100

leanprover/fp-lean#301 · Opened Sep 17, 2026
`@[deprecated]` on a structure field projection does not warn when constructing the field Open

bug

Difficulty 4/5 3-5 days Newbie friendliness 48/100

leanprover/lean4#15203 · Opened Sep 17, 2026
Completion popup reopens after Esc in Lean files; caused by default quickSuggestionsDelay of 200 Open

bug

Difficulty 2/5 1-3 hours Newbie friendliness 72/100

leanprover/vscode-lean4#800 · 1 comment · Opened Sep 17, 2026
Tracking-issue option on statement directives (`issue := N`), alongside `pr_url` Open

Difficulty 4/5 3-5 days Newbie friendliness 68/100

leanprover/verso-blueprint#463 · Opened Sep 17, 2026
`simpDiscrCtor?` is broken in the presence of non-type parameters Open

bug

Difficulty 4/5 3-5 days Newbie friendliness 48/100

leanprover/lean4#15200 · Opened Sep 17, 2026
`simp [...]` with a left arrow (`←`) on a simproc should error Open

bug

Difficulty 2/5 1-3 hours Newbie friendliness 84/100

leanprover/lean4#15197 · Opened Sep 17, 2026
`#guard_msgs` hides error messages from commands outside of it Open

bug

Difficulty 4/5 3-5 days Newbie friendliness 45/100

leanprover/lean4#15196 · Opened Sep 17, 2026
`bv_decide` fails with `unknown free variable '_fvar.126'` under certain contexts Open

bug

Difficulty 4/5 3-5 days Newbie friendliness 48/100

leanprover/lean4#15195 · Opened Sep 17, 2026
`Nat.shiftLeft` by 2^32 or more crashes Lean in `rfl`, `decide`, `simp`, `cbv`, `grind` and the compiler Open

Difficulty 4/5 3-5 days Newbie friendliness 45/100

leanprover/lean4#15193 · Opened Sep 17, 2026
There's needs to be a way to submit with much higher memory limit Open

Difficulty 5/5 Over a week Newbie friendliness 35/100

leanprover/lean-eval#642 · Opened Sep 17, 2026
Emscripten build passes `-pthread` unconditionally, ignoring `MULTI_THREAD=OFF` Open

Difficulty 3/5 1-2 days Newbie friendliness 72/100

leanprover/lean4#15186 · Opened Sep 16, 2026
Unify treatment of temp directories. Open

Difficulty 3/5 1-2 days Newbie friendliness 68/100

leanprover/lean-workbench#142 · Opened Sep 16, 2026
Move `_file` to publications origin Open

Difficulty 4/5 3-5 days Newbie friendliness 35/100

leanprover/lean-workbench#140 · 1 comment · Opened Sep 16, 2026
grind explodes on a simple example with `Array.range` Open

bug

Difficulty 4/5 3-5 days Newbie friendliness 52/100

leanprover/lean4#15183 · Opened Sep 16, 2026
(kernel) application type mismatch in `cbv` with `ite_true` Open

bug

Difficulty 3/5 1-2 days Newbie friendliness 55/100

leanprover/lean4#15182 · Opened Sep 16, 2026
MULTI_THREAD=OFF build fails: std::adopt_lock_t used in thread.h without including <mutex> Open

Difficulty 2/5 1-3 hours Newbie friendliness 86/100

leanprover/lean4#15172 · 1 comment · Opened Sep 15, 2026
The "Rename Symbol" code action fails to account for constructor/destructor tags Open

bug

Difficulty 3/5 1-2 days Newbie friendliness 58/100

leanprover/vscode-lean4#799 · Opened Sep 15, 2026
perf: reduce Nat.powMod kernel replay cost Open

Difficulty 4/5 3-5 days Newbie friendliness 52/100

leanprover/lean4#15166 · Opened Sep 15, 2026
@[blueprint] behavior depends on imports Open

Difficulty 5/5 Over a week Newbie friendliness 45/100

leanprover/verso-blueprint#462 · Opened Sep 14, 2026
New submission page is broken Open

Difficulty 3/5 1-2 days Newbie friendliness 64/100

leanprover/lean-eval#637 · 1 reaction · Opened Sep 13, 2026
Should a checker reject a let type mismatch that disappears after substitution? Open

Difficulty 5/5 Over a week Newbie friendliness 35/100

leanprover/lean4export#48 · 1 comment · Opened Sep 13, 2026
Post-overhaul UX, performance, and cleanup triage Open

Difficulty 5/5 Over a week Newbie friendliness 20/100

leanprover/lean-eval#634 · Opened Sep 13, 2026
Axioms and Computation: is "virtual machine" still the right term? Open

Difficulty 2/5 1-3 hours Newbie friendliness 68/100

leanprover/theorem_proving_in_lean4#233 · Opened Sep 13, 2026
Follow up on transport, test setup, and documentation review Open

Difficulty 5/5 Over a week Newbie friendliness 25/100

leanprover/subverso#240 · Opened Sep 12, 2026
Docs: lean_sync runs setup-file and builds stale imports; the daemon pins the toolchain under .beam Open

Difficulty 2/5 1-3 hours Newbie friendliness 70/100

leanprover/lean-beam#257 · Opened Sep 12, 2026
An external Lake build never clears a dependency's needsSave; the sync barrier then refuses the importer and the recovery plan points at save Open

Difficulty 4/5 3-5 days Newbie friendliness 52/100

leanprover/lean-beam#256 · Opened Sep 12, 2026
lean_save hangs to the client idle timeout instead of returning saveUnsupportedSetup in a package with batch-only moreLeanArgs Open

Difficulty 4/5 3-5 days Newbie friendliness 52/100

leanprover/lean-beam#255 · Opened Sep 12, 2026
RFC: structured log entries in Lake, and a JSON log format for `lake build` Open

RFC

Difficulty 5/5 Over a week Newbie friendliness 35/100

leanprover/lean4#15139 · 2 comments · Opened Sep 12, 2026
RFC: Support dependency in Verso docstrings Open

RFC

Difficulty 5/5 Over a week Newbie friendliness 45/100

leanprover/lean4#15137 · 2 reactions · Opened Sep 11, 2026
custom semantic highlighting appears only when source file is first edited Open

bug

Difficulty 4/5 3-5 days Newbie friendliness 52/100

leanprover/lean4#15118 · 6 comments · Opened Sep 11, 2026
#guard_panic misclassifies ordinary errors as panics via a naive substring check, silently deleting the message log Open

bug

Difficulty 3/5 1-2 days Newbie friendliness 68/100

leanprover/lean4#15117 · Opened Sep 11, 2026
`#eval` of an `IO` action aborts `lean` (uncaught `lean::exception`, exit 134) when it reaches a non-`meta` import through a local definition Open

bug

Difficulty 4/5 3-5 days Newbie friendliness 52/100

leanprover/lean4#15113 · 2 comments · Opened Sep 10, 2026
Linux: libleanshared.so exports a partial _Unwind_* ABI, breaking C++ exceptions inside FFI libraries built against libstdc++ Open

Difficulty 4/5 3-5 days Newbie friendliness 45/100

leanprover/lean4#15112 · 1 reaction · Opened Sep 10, 2026
Missing goal state after `grind =>`, `sym =>` and `impossible by` Open

bug

Difficulty 3/5 1-2 days Newbie friendliness 70/100

leanprover/lean4#15108 · 1 comment · 2 reactions · Opened Sep 10, 2026
Is there an existing or planned HTML-to-Verso importer? Open

Difficulty 5/5 Over a week Newbie friendliness 30/100

leanprover/verso#980 · 1 comment · Opened Sep 10, 2026
Kernel-heavy submissions: 360-min job with single-threaded nanoda replay caps `decide +kernel` work at ~10 CPU-h — is a larger budget or parallel replay possible? Open

Difficulty 4/5 3-5 days Newbie friendliness 38/100

leanprover/lean-eval-submissions#1697 · 1 comment · Opened Sep 10, 2026
omega hits the recursion limit on a reflexive multiplication goal with an unused hypothesis Open

bug

Difficulty 3/5 1-2 days Newbie friendliness 64/100

leanprover/lean4#15102 · Opened Sep 9, 2026
`grind` failing to apply lemma if instance is not syntactically equal Open

bug

Difficulty 4/5 3-5 days Newbie friendliness 55/100

leanprover/lean4#15082 · 1 comment · Opened Sep 9, 2026
RFC: use `Std.Refl`/`Std.Symm` instances in `rfl`/`symm` Open

RFC

Difficulty 5/5 Over a week Newbie friendliness 39/100

leanprover/lean4#15081 · 2 reactions · Opened Sep 9, 2026
Deal with name collisions Open

Difficulty 4/5 3-5 days Newbie friendliness 38/100

leanprover/lean-workbench#132 · 1 comment · Opened Sep 8, 2026
`deriving instance CoeFun/CoeSort` generates opaque aux constant for reducible type synonyms Open

bug

Difficulty 4/5 3-5 days Newbie friendliness 55/100

leanprover/lean4#15065 · 1 comment · 3 reactions · Opened Sep 8, 2026
verso-literate attaches a declaration's docstring to a constant defined by one of its attributes Open

Difficulty 3/5 1-2 days Newbie friendliness 65/100

leanprover/verso#979 · Opened Sep 7, 2026
Std.Http minor cleanups Open

RFC

Difficulty 4/5 3-5 days Newbie friendliness 35/100

leanprover/lean4#15051 · 1 reaction · Opened Sep 7, 2026
Open projects into a reasonable state Open

Difficulty 3/5 1-2 days Newbie friendliness 64/100

leanprover/lean-workbench#130 · Opened Sep 6, 2026
elan-init --default-toolchain records the default but never installs it (exits 0 with no toolchain on disk) Open

Difficulty 3/5 1-2 days Newbie friendliness 72/100

leanprover/elan#210 · Opened Sep 6, 2026
No `goalsAccomplished` message is produced for theorems generated using `elab` Open

bug P-medium

Difficulty 3/5 1-2 days Newbie friendliness 72/100

leanprover/lean4#15044 · 1 comment · Opened Sep 6, 2026
Delaborator omits an instance binder's name when it is used only in a later binder's type Open

P-medium

Difficulty 2/5 1-3 hours Newbie friendliness 78/100

leanprover/lean4#15037 · Opened Sep 4, 2026

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