"ubuntu-slim" incorrectly dowloads latest on node-version "24" or "24.x"

[mikeharder]

Description:
On ubuntu-slim, using node-version of 24 or 24.x downloads 24.13.1, instead of using 24.13.0 from the cache. On ubuntu-latest, both 24 and 24.x use the cached version. On both images, leaving version empty "" used the cached 24.13.0.

Action version:
v6

Platform:

• Ubuntu
• macOS
• Windows

Runner type:

• Hosted
• Self-hosted

Tools version:
24

Repro steps:

name: setup-node

on:
  pull_request:
  workflow_dispatch:

permissions:
  contents: read

jobs:
  test:
    runs-on: ${{ matrix.os }}

    strategy:
      matrix:
        node-version: ['24.x', '24', '']
        os: [ubuntu-slim, ubuntu-latest]

    steps:
      - uses: actions/setup-node@v6
        with:
          node-version: ${{ matrix.node-version }}
      
      - run: node -v

https://github.com/mikeharder/test-setup-node/blob/192c349bd754b02fcb70057fa5ebe9b6315c73a0/.github/workflows/setup-node.yaml

https://github.com/mikeharder/test-setup-node/actions/runs/21978003995

Expected behavior:
ubuntu-latest:

Run actions/setup-node@v6
  with:
    node-version: 24.x
    check-latest: false
    token: ***
    package-manager-cache: true
##[debug]isExplicit: 
##[debug]explicit? false
##[debug]isExplicit: 20.20.0
##[debug]explicit? true
##[debug]isExplicit: 22.22.0
##[debug]explicit? true
##[debug]isExplicit: 24.13.0
##[debug]explicit? true
##[debug]evaluating 3 versions
##[debug]matched: 24.13.0
##[debug]checking cache: /opt/hostedtoolcache/node/24.13.0/x64
##[debug]Found tool in cache node 24.13.0 x64
Found in cache @ /opt/hostedtoolcache/node/24.13.0/x64

Actual behavior:
ubuntu-slim:

Run actions/setup-node@v6
  with:
    node-version: 24.x
    check-latest: false
    token: ***
    package-manager-cache: true
##[debug]isExplicit: 
##[debug]explicit? false
##[debug]evaluating 0 versions
##[debug]match not found
Attempting to download 24.x...
Acquiring 24.13.1 - x64 from https://github.com/actions/node-versions/releases/download/24.13.1-21889660756/node-24.13.1-linux-x64.tar.gz
Extracting ...
/usr/bin/tar xz --strip 1 --warning=no-unknown-keyword --overwrite -C /home/runner/work/_temp/59cebe8b-4470-41c9-973c-af5e8e15f687 -f /home/runner/work/_temp/693643e2-4471-4597-b383-bb315dcd6f5e
Adding to the cache ...

[priya-kinthali]

Hello @mikeharder👋,
Thank you for reporting this issue. We will investigate it and get back to you as soon as we have some feedback.