GLFW.ThreadAssertionError when using GLMakie or KiteViewers or CImGui.jl

[ufechner7]

Pre-submission checklist

• I have searched existing issues and confirmed this is not a duplicate.

Client

VSCode with JETLS client 0.3.4

Julia versioninfo()

Julia Version 1.12.5
Commit 5fe89b8ddc1 (2026-02-09 16:05 UTC)
Build Info:
  Official https://julialang.org release
Platform Info:
  OS: Linux (x86_64-linux-gnu)
  CPU: 32 × AMD Ryzen 9 7950X 16-Core Processor
  WORD_SIZE: 64
  LLVM: libLLVM-18.1.7 (ORCJIT, znver4)
  GC: Built with stock GC
Threads: 1 default, 1 interactive, 1 GC (on 32 virtual cores)
Environment:
  LD_LIBRARY_PATH = /lib:/usr/lib:/usr/local/lib

JETLS version

JETLS version 2026-02-16

Reproduction with the VSCode reference client

• I have confirmed this issue also reproduces with the VSCode reference client.
• This issue does NOT reproduce with the VSCode reference client, but I believe JETLS-side changes are needed.

Description

The error shown below appears under problems, along with many other error messages about unknown symbols. This is sporadic. The error occurs only if JETLS analyses the file from a thread other than the main thread.

Steps to reproduce

1. Install the package KiteViewers (using Pkg; Pkg.add("KiteViewers"))

2. Open the following Julia file:

using KiteViewers

println("Hello!")

3. Wait until JETLS has analysed the file
4. You will get the following error:

InitError: GLFW.ThreadAssertionError(1, 3)
Stacktrace:
  [1] require_main_thread
    @ ~/.julia/packages/GLFW/wA4ue/src/GLFW.jl:26 [inlined]
  [2] SetErrorCallback
    @ ~/.julia/packages/GLFW/wA4ue/src/callback.jl:50 [inlined]
  [3] __init__
    @ ~/.julia/packages/GLFW/wA4ue/src/GLFW.jl:53
  [4] run_module_init(mod::Module, i::Int64)
    @ Base ./loading.jl:1443
  [5] register_restored_modules(sv::Core.SimpleVector, pkg::Base.PkgId, path::String)
    @ Base ./loading.jl:1431
  [6] _include_from_serialized(pkg::Base.PkgId, path::String, ocachepath::String, depmods::Vector{Any}; register::Bool)
    @ Base ./loading.jl:1319
  [7] _include_from_serialized
    @ ./loading.jl:1274 [inlined]
  [8] _require_search_from_serialized(pkg::Base.PkgId, sourcepath::String, build_id::UInt128, stalecheck::Bool; reasons::Dict{String, Int64}, DEPOT_PATH::Vector{String})
    @ Base ./loading.jl:2102
  [9] _require_search_from_serialized
    @ ./loading.jl:2009 [inlined]
 [10] __require_prelocked(pkg::Base.PkgId, env::String)
    @ Base ./loading.jl:2627
 [11] _require_prelocked(uuidkey::Base.PkgId, env::String)
    @ Base ./loading.jl:2493
 [12] macro expansion
    @ ./loading.jl:2421 [inlined]
 [13] macro expansion
    @ ./lock.jl:376 [inlined]
 [14] __require(into::Module, mod::Symbol)
    @ Base ./loading.jl:2386
 [15] require(into::Module, mod::Symbol)
    @ Base ./loading.jl:2362
 [16] eval(m::Module, e::Any)
    @ Core ./boot.jl:489
 [17] #usemodule_with_err_handling##4
    @ ~/.julia/packages/JET/wAXN9/src/toplevel/virtualprocess.jl:1613
 [18] #with_err_handling#75
    @ ~/.julia/packages/JET/wAXN9/src/toplevel/virtualprocess.jl:1861
 [19] usemodule_with_err_handling
    @ ~/.julia/packages/JET/wAXN9/src/toplevel/virtualprocess.jl:1541
 [20] step_expr!
    @ ~/.julia/packages/JET/wAXN9/src/toplevel/virtualprocess.jl:1623
 [21] step_expr!
    @ ~/.julia/packages/JETLS/ClF3M/src/analysis/Interpreter.jl:302
 [22] step_expr!
    @ ~/.julia/packages/JuliaInterpreter/Okk3o/src/interpret.jl:620
 [23] step_expr!
    @ ~/.julia/packages/LoweredCodeUtils/7mcWs/src/codeedges.jl:1055
 [24] finish!
    @ ~/.julia/packages/JuliaInterpreter/Okk3o/src/commands.jl:14
 [25] finish_and_return!
    @ ~/.julia/packages/JuliaInterpreter/Okk3o/src/commands.jl:30
 [26] selective_eval!
    @ ~/.julia/packages/LoweredCodeUtils/7mcWs/src/codeedges.jl:1090
 [27] selective_eval_fromstart!
    @ ~/.julia/packages/LoweredCodeUtils/7mcWs/src/codeedges.jl:1103
 [28] partially_interpret!
    @ ~/.julia/packages/JET/wAXN9/src/toplevel/virtualprocess.jl:1292
 [29] #_virtual_process!#61
    @ ~/.julia/packages/JET/wAXN9/src/toplevel/virtualprocess.jl:1080
 [30] _virtual_process!
    @ ~/.julia/packages/JET/wAXN9/src/toplevel/virtualprocess.jl:908 [inlined]
 [31] virtual_process!
    @ ~/.julia/packages/JET/wAXN9/src/toplevel/virtualprocess.jl:673 [inlined]
 [32] virtual_process!(interp::JETLS.Interpreter.LSInterpreter{JETLS.Server{Returns{Nothing}}}, x::JuliaSyntax.SyntaxNode, overrideex::Nothing)
    @ JETLS.Interpreter ~/.julia/packages/JETLS/ClF3M/src/analysis/Interpreter.jl:252
 [33] virtual_process(interp::JETLS.Interpreter.LSInterpreter{JETLS.Server{Returns{Nothing}}}, x::JuliaSyntax.SyntaxNode, filename::String, config::JET.ToplevelConfig; overrideex::Nothing)
    @ JET ~/.julia/packages/JET/wAXN9/src/toplevel/virtualprocess.jl:653
 [34] virtual_process
    @ ~/.julia/packages/JET/wAXN9/src/toplevel/virtualprocess.jl:606 [inlined]
 [35] #analyze_and_report_expr!#137
    @ ~/.julia/packages/JET/wAXN9/src/JETBase.jl:1041 [inlined]
 [36] analyze_and_report_expr!
    @ ~/.julia/packages/JET/wAXN9/src/JETBase.jl:1024 [inlined]
 [37] analyze_parsed_if_exist(::JETLS.Server{Returns{Nothing}}, ::JETLS.AnalysisRequest; activation_done::Base.Event)
    @ JETLS ~/.julia/packages/JETLS/ClF3M/src/analysis/full-analysis.jl:585
 [38] (::JETLS.var"#activate_with_early_release##0#activate_with_early_release##1"{JETLS.var"#execute_analysis_request##2#execute_analysis_request##3"{JETLS.Server{Returns{Nothing}}, JETLS.AnalysisRequest}, Base.Event})()
    @ JETLS ~/.julia/packages/JETLS/ClF3M/src/utils/pkg.jl:147
during initialization of module GLFW

JETLS configuration (if applicable)

No response

Additional context (optional)

No response

[ufechner7]

Using the following settings.json file:

{
  "jetls-client.executable": {
      "path": "jetls",
      "threads": "1,0"
  }
}

In the .vscode folder, this solves the issue.

[ufechner7]

Possibly better solution: https://discourse.julialang.org/t/ann-kaimon-jl-opening-the-gate-between-ai-agents-and-julia/135880/68

ex() runs evals on worker threads, but GLMakie needs thread 1. Agents should pass mt=true to route through the REPL backend’s main thread.

So a similar issue was encountered by Kaimon.jl, and they found a better solution to force some operations to use thread one.

[ufechner7]

The workaround above does not always help. So this really needs JETLS's support.

[AwesomeQuest]

This also happens when using CImGui.jl