# Unsolvable environment with julia-downgrade-compat due to libblastrampoline\_jll on julia v1.9

**URL:** <https://discourse.julialang.org/t/unsolvable-environment-with-julia-downgrade-compat-due-to-libblastrampoline-jll-on-julia-v1-9/136094>\
**Category:** Package Management\
**Created:** [March 8, 2026, 4:30pm UTC](https://discourse.julialang.org/t/unsolvable-environment-with-julia-downgrade-compat-due-to-libblastrampoline-jll-on-julia-v1-9/136094 "2026-03-08T16:30:02Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![jmert](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/jmert/32/3161_2.png) [@jmert](https://discourse.julialang.org/u/jmert)\
**Post date:** [March 8, 2026, 4:30pm UTC](https://discourse.julialang.org/t/unsolvable-environment-with-julia-downgrade-compat-due-to-libblastrampoline-jll-on-julia-v1-9/136094/1 "2026-03-08T16:30:03Z")

</div>

I’m trying to use the [julia-downgrade-compat](https://github.com/julia-actions/julia-downgrade-compat) (v2) Github Action in a project, and I’ve run into problems with unresolvable environments for julia v1.9.

I’ve tracked down the (apparent) problem to any package chain that leads to requiring libblastrampoline\_jll. With some minor edits to a local clone of [Resolver.jl](https://github.com/StefanKarpinski/Resolver.jl/) to print more information, the following sequence fails:

```bash
$ mkdir mwe
$ cd mwe
$ touch Project.toml
$ julia --project --startup-file=no -e 'using Pkg; pkg"add libblastrampoline_jll"; pkg"compat libblastrampoline_jll"'
...
$ julia ~/ext/Resolver.jl/bin/resolve.jl --julia=1.9 .
ERROR: LoadError: Unsatisfiable:
        1222c4b2-2114-5bfd-aeef-88e4692bbb3e julia => 1.9.4
        8e850b90-86db-534c-a0d3-1478176c7d93 libblastrampoline_jll => nothing

Stacktrace:
...

```

I’ve spent some time trying to understand why there is no valid version identified, and this is what I’ve noticed:

1. Reading the [libblastrampoline\_jll Compat.toml](https://github.com/JuliaRegistries/General/blob/master/jll/L/libblastrampoline_jll/Compat.toml) file, I think we expect as installable versions:
  - julia v1.6 — lbt\_jll v1.\*, v2.\*, v3.\*
  - julia v1.7 — lbt\_jll v1.\*, v2.\*, v3.\*
  - julia v1.8 — lbt\_jll v4.\*, v5.0–v5.2
  - julia v1.9 — lbt\_jll v4.\*, v5.0–v5.4
  - julia v1.10 — lbt\_jll v5.5–v5.12
  - julia v1.11 — lbt\_jll v5.5–v5.12
  - julia v1.12 — lbt\_jll v5.13+ && \<v6

2. When I use Pkg to resolve a manifest on julia v1.9, it installs libblastrampoline\_jll v5.8, newer than what I’d expect is possible

```julia-auto
$ julia +1.9 -q --startup-file=no --project -e 'using Pkg; Pkg.resolve()'
    Updating `/tmp/mwe/Project.toml`
  [8e850b90] ~ libblastrampoline_jll ⇒ v5.8.0+0
    Updating `/tmp/mwe/Manifest.toml`
  [56f22d72] + Artifacts
  [8f399da3] + Libdl
  [8e850b90] + libblastrampoline_jll v5.8.0+0

```

3. If I try to force adding libblastrampoline\_jll v5.4, the restriction is seemingly ignored:

```julia-auto
$ julia +1.9 -q --startup-file=no --project -e 'using Pkg; pkg"compat libblastrampoline_jll =5.4.0"'
      Compat entry set:
  libblastrampoline_jll = "=5.4.0"
     Resolve checking for compliance with the new compat rules...
    Updating `/tmp/mwe/Project.toml`
  [8e850b90] ~ libblastrampoline_jll ⇒ v5.8.0+0
    Updating `/tmp/mwe/Manifest.toml`
  [56f22d72] + Artifacts
  [8f399da3] + Libdl
  [8e850b90] + libblastrampoline_jll v5.8.0+0

```

Is there something I’m misunderstanding about the compatibility format so I’m interpreting everything incorrectly? Or is this a problem with Resolver.jl and there being “unknown” special-case rules for some of the stdlib-related dependencies on older versions of Julia?

---

<div class="post-metadata">

**Author:** ![jmert](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/jmert/32/3161_2.png) [@jmert](https://discourse.julialang.org/u/jmert)\
**Post date:** [March 8, 2026, 5:30pm UTC](https://discourse.julialang.org/t/unsolvable-environment-with-julia-downgrade-compat-due-to-libblastrampoline-jll-on-julia-v1-9/136094/2 "2026-03-08T17:30:43Z")

</div>

Adding more breadcrumbs to the problem, julia v1.9.0 includes [libblastrampoline\_jll v5.7.0](https://github.com/JuliaLang/julia/blob/v1.9.0/deps/blastrampoline.version) and julia v1.9.1–1.9.4 include [libblastrampoline\_jll v5.8.0](https://github.com/JuliaLang/julia/blob/v1.9.4/deps/blastrampoline.version) (via backporting of the juliv v1.10-era JuliaLang/julia#49658), so that presumably explains why/how Pkg chooses v5.8.0 despite what I think the registry is saying.

_Edit:_  
Is the registry missing an update to match the backport? I found [this comment](https://github.com/JuliaLang/julia/pull/49281#discussion_r1160797775) asking about preparing for the bump to libblastrampoline\_jll v5.7 to be backported to the julia v1.9 branch.

---

<div class="post-metadata">

**Author:** ![jmert](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/jmert/32/3161_2.png) [@jmert](https://discourse.julialang.org/u/jmert)\
**Post date:** [March 8, 2026, 6:20pm UTC](https://discourse.julialang.org/t/unsolvable-environment-with-julia-downgrade-compat-due-to-libblastrampoline-jll-on-julia-v1-9/136094/3 "2026-03-08T18:20:09Z")

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Hacking a local git clone of the General repository with the following diff:

```diff
diff --git a/jll/L/libblastrampoline_jll/Compat.toml b/jll/L/libblastrampoline_jll/Compat.toml
index 739a135e000..f8cb42dcdca 100644
--- a/jll/L/libblastrampoline_jll/Compat.toml
+++ b/jll/L/libblastrampoline_jll/Compat.toml
@@ -10,13 +10,13 @@ julia = "1.8.0-1"
 ["5.13-5"]
 julia = "1.12.0-1"
 
-["5.4"]
-julia = "1.9.0-1"
-
 ["5.4-5"]
 Artifacts = ["0.0.0", "1"]
 JLLWrappers = "1.7.0-1"
 Libdl = ["0.0.0", "1"]
 
-["5.5-5.12"]
-julia = "1.10.0-1"
+["5.4-5.7"]
+julia = "1.9.0-1"
+
+["5.8-5.12"]
+julia = "1.9.1-1"

```

Resolver.jl then solves the MWE in the top post:

```bash
$ julia ~/ext/Resolver.jl/bin/resolve.jl --julia=1.9.4 --min=@alldeps --print-versions .
1222c4b2-2114-5bfd-aeef-88e4692bbb3e julia 1.9.4
8e850b90-86db-534c-a0d3-1478176c7d93 libblastrampoline_jll 5.8.0+0
21216c6a-2e73-6563-6e65-726566657250 Preferences 1.5.2
4ec0a83e-493e-50e2-b9ac-8f72acf5a8f5 Unicode 1.9.4
56f22d72-fd6d-98f1-02f0-08ddc0907c33 Artifacts 1.9.4
692b3bcd-3c85-4b1f-b108-f13ce0eb3210 JLLWrappers 1.7.1
8f399da3-3557-5675-b5ff-fb832c97cbdb Libdl 1.9.4
ade2ca70-3891-5945-98fb-dc099432e06a Dates 1.9.4
de0858da-6303-5e67-8744-51eddeeeb8d7 Printf 1.9.4
fa267f1f-6049-4f14-aa54-33bafae1ed76 TOML 1.0.3

```

I can create a PR in General to make this change if this is something like the right thing to do. Other opinions/recommendations?

---

<div class="post-metadata">

**Author:** ![jmert](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/jmert/32/3161_2.png) [@jmert](https://discourse.julialang.org/u/jmert)\
**Post date:** [March 15, 2026, 5:02pm UTC](https://discourse.julialang.org/t/unsolvable-environment-with-julia-downgrade-compat-due-to-libblastrampoline-jll-on-julia-v1-9/136094/4 "2026-03-15T17:02:30Z")

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Fixed by [libblastrampoline\_jll: Reflect backporting in Julia v1.9 versions by jmert · Pull Request #150216 · JuliaRegistries/General · GitHub](https://github.com/JuliaRegistries/General/pull/150216)