# Stacker: tool to bump snapshots in \`stack\*.yaml\` files

**URL:** <https://discourse.haskell.org/t/stacker-tool-to-bump-snapshots-in-stack-yaml-files/13907>\
**Category:** Announcements\
**Created:** [April 8, 2026, 5:31pm UTC](https://discourse.haskell.org/t/stacker-tool-to-bump-snapshots-in-stack-yaml-files/13907 "2026-04-08T17:31:24Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![andreasabel](https://sea2.discourse-cdn.com/flex002/user_avatar/discourse.haskell.org/andreasabel/32/1764_2.png) [@andreasabel](https://discourse.haskell.org/u/andreasabel)\
**Post date:** [April 8, 2026, 5:31pm UTC](https://discourse.haskell.org/t/stacker-tool-to-bump-snapshots-in-stack-yaml-files/13907/1 "2026-04-08T17:31:24Z")

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When I learned last Fall that coding agents can now do a decent job I wondered what productivity tool I always wanted for maintaining Haskell project and found a little job that I could mechanize: bump the value of the `snapshot` (or `resolver`) field in `stack*.yaml` files to the latest in the respective LTS or nightly series. So I vibe-coded last December a little command-line tool that does that routine job for me, using Github Copilot.  
Release of the resulting tool, `stacker`, was delayed by the unfortunate state of Stackage (Jan-Mar 2026) that had bumped nightly to a compiler (9.12.3) that never went live on ghcup. Now with GHC 9.12.4 the latest nightly is usable again, so that is a good time to ship it!

> **[stacker](https://hackage.haskell.org/package/stacker)**
>
> Bump snapshots in stack.yaml files

Example run:

```haskell
$ stacker

stack-9.0.yaml lts-19.33 ✓ up to date
stack-9.10.yaml lts-24.28 → bump to lts-24.36
stack-9.12.yaml nightly-2025-10-14 → bump to nightly-2026-04-01
stack-9.2.yaml lts-20.26 ✓ up to date
stack-9.4.yaml lts-21.25 ✓ up to date
stack-9.6.yaml lts-22.44 ✓ up to date
stack-9.8.yaml lts-23.28 ✓ up to date
stack.yaml nightly-2025-10-14 = symlink to stack-9.12.yaml

```

```haskell
$ stacker bump

Updating stack-9.10.yaml
Updating stack-9.12.yaml

```

Recommendation: use in version-controlled directories so you can undo changes.

Genesis: I started by writing a specification including examples (what is now the README) and then asked Copilot to implement it. The first version was buggy but the behavior could be corrected quickly. The testsuite wasn’t done properly at first because the agent replicated some code in the testsuite—of course, that does not adequately test the product, that just fakes it! Most annoying was getting the Windows part of the CI to work since Copilot does not run CI and learn from it. Since the golden values contain file paths and unicode characters, there were several iterations needed to get the test suite run correctly under Windows. The coding style isn’t to my standards but for a little productivity tool I can make compromises. Giving clear style instructions could potentially help, I have not tried this.

My verdict on agentic Haskell programming for now is: I can see myself vibe-coding more small tools, but I don’t have a feeling yet whether I could use agents for more demanding coding or for working on real code bases.

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**Author:** ![janus](https://sea2.discourse-cdn.com/flex002/user_avatar/discourse.haskell.org/janus/32/1060_2.png) [@janus](https://discourse.haskell.org/u/janus)\
**Post date:** [April 9, 2026, 7:53pm UTC](https://discourse.haskell.org/t/stacker-tool-to-bump-snapshots-in-stack-yaml-files/13907/2 "2026-04-09T19:53:15Z")

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I was thinking of implementing resolver bumping in Renovate, but I didn’t since it seemed like a lot of work to implement everything [stack-lint-extra-deps](https://github.com/freckle/stack-lint-extra-deps) does.

I am curious, did you try using stack-lint-extra-deps to bump the resolver, and did you have any issues with it?

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<div class="post-metadata">

**Author:** ![andreasabel](https://sea2.discourse-cdn.com/flex002/user_avatar/discourse.haskell.org/andreasabel/32/1764_2.png) [@andreasabel](https://discourse.haskell.org/u/andreasabel)\
**Post date:** [April 11, 2026, 8:17am UTC](https://discourse.haskell.org/t/stacker-tool-to-bump-snapshots-in-stack-yaml-files/13907/3 "2026-04-11T08:17:52Z")

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Thanks, @janus, for the pointer. I installed `stack-lint-extra-deps` and it seems very useful. Also, it seems to be implemented in a better way than my tool, as it queries `stackage.org` for the list of resolvers (fast), whereas my tool clones the `stackage-snapshots` repo and constructs the information from there (slow).

However, `stack-lint-extra-deps` does not fit my purpose because it has only two snapshot categories, `lts` or `nightly`, so I will bump any `lts` constraint to the _absolutely_ latest `lts`, whereas I want the latest `lts` for the respective GHC major version.

So this is not good if you want to maintain build with older GHCs.

Also, it appears not to be released on Hackage so it might just disappear at any time.