fix: include runner image in cache key to prevent cross-provider collisions

The cache key included only os and arch (`mise-v1-macos-arm64-<hash>`),
so any repo running CI on multiple runner providers with the same
os/arch — github-hosted, namespace.so, BuildJet, self-hosted M-series
macs — would clobber each other's caches. The first run on a new
provider would restore tool installs built for the previous provider's
image, leading to "does not have an executable named X" errors or
SIGILL crashes on cached binaries built against a different glibc.

Append the GitHub Actions hosted-runner ImageOS env var (e.g.
"macos15", "ubuntu24") to the cache key's platform segment. Other
runners pool under "self-hosted"; users running multiple self-hosted
profiles can scope further with cache_key_prefix.

Implementation note: `getTarget()` is also used to construct the mise
binary download URL (must match the release-asset filename, e.g.
`mise-v2026.4.0-macos-arm64.tar.gz`). Adding the image suffix there
would 404 the download. So `getTarget()` keeps its current shape and
a new `getRunnerImageId()` helper composes the image discriminator
into the cache-key platform segment only.

This is a one-time cache miss for existing users; the cache rebuilds
on the next run and stays scoped per-image after that.

README.md

@@ -68,7 +68,7 @@ When using `cache_key`, you can use template variables to reference internal val
 Available template variables:
 - `{{version}}` - The mise version (from the `version` input)
 - `{{cache_key_prefix}}` - The cache key prefix (from `cache_key_prefix` input or default)
-- `{{platform}}` - The target platform (e.g., "linux-x64", "macos-arm64")
+- `{{platform}}` - The target platform, including the runner image (e.g., "linux-x64-ubuntu24", "macos-arm64-macos15", "linux-x64-self-hosted"). The trailing segment is `process.env.ImageOS` on github-hosted runners and falls back to `"self-hosted"` elsewhere — preventing cache collisions when the same repo runs on different runner providers (github-hosted, namespace.so, self-hosted).
 - `{{file_hash}}` - Hash of all mise configuration files
 - `{{mise_env}}` - The MISE_ENV environment variable value
 - `{{install_args_hash}}` - SHA256 hash of the sorted tools from install args

dist/index.js

@@ -86042,10 +86042,7 @@ async function saveCache(cacheKey) {
     });
 }
 async function getTarget() {
-    let { arch } = process;
-    // quick overwrite to abide by release format
-    if (arch === 'arm')
-        arch = 'armv7';
+    const arch = process.arch === 'arm' ? 'armv7' : process.arch;
     switch (process.platform) {
         case 'darwin':
             return `macos-${arch}`;
@@ -86057,13 +86054,24 @@ async function getTarget() {
             throw new Error(`Unsupported platform ${process.platform}`);
     }
 }
+/**
+ * Identifies the runner image so cached binaries from one provider
+ * (github-hosted, namespace.so, BuildJet, self-hosted) aren't restored
+ * onto another provider's image where their compiled-in paths and libc
+ * versions don't match. GitHub-hosted images export `ImageOS`
+ * (e.g. "macos15", "ubuntu24"); other runners leave it unset and pool
+ * under "self-hosted".
+ */
+function getRunnerImageId() {
+    return process.env.ImageOS || 'self-hosted';
+}
 async function processCacheKeyTemplate(template) {
     // Get all available variables
     const version = getInput('version');
     const installArgs = getInput('install_args');
     const cacheKeyPrefix = getInput('cache_key_prefix') || 'mise-v1';
     const miseEnv = process.env.MISE_ENV?.replace(/,/g, '-');
-    const platform = await getTarget();
+    const platform = `${await getTarget()}-${getRunnerImageId()}`;
     // Calculate file hash
     const fileHash = await hashFiles(MISE_CONFIG_FILE_PATTERNS.join('\n'));
     // Calculate install args hash

src/index.ts

@@ -483,11 +483,7 @@ async function saveCache(cacheKey: string): Promise<void> {
 }
 
 async function getTarget(): Promise<string> {
-  let { arch } = process
-
-  // quick overwrite to abide by release format
-  if (arch === 'arm') arch = 'armv7' as NodeJS.Architecture
-
+  const arch = process.arch === 'arm' ? 'armv7' : process.arch
   switch (process.platform) {
     case 'darwin':
       return `macos-${arch}`
@@ -500,13 +496,25 @@ async function getTarget(): Promise<string> {
   }
 }
 
+/**
+ * Identifies the runner image so cached binaries from one provider
+ * (github-hosted, namespace.so, BuildJet, self-hosted) aren't restored
+ * onto another provider's image where their compiled-in paths and libc
+ * versions don't match. GitHub-hosted images export `ImageOS`
+ * (e.g. "macos15", "ubuntu24"); other runners leave it unset and pool
+ * under "self-hosted".
+ */
+function getRunnerImageId(): string {
+  return process.env.ImageOS || 'self-hosted'
+}
+
 async function processCacheKeyTemplate(template: string): Promise<string> {
   // Get all available variables
   const version = core.getInput('version')
   const installArgs = core.getInput('install_args')
   const cacheKeyPrefix = core.getInput('cache_key_prefix') || 'mise-v1'
   const miseEnv = process.env.MISE_ENV?.replace(/,/g, '-')
-  const platform = await getTarget()
+  const platform = `${await getTarget()}-${getRunnerImageId()}`
 
   // Calculate file hash
   const fileHash = await glob.hashFiles(MISE_CONFIG_FILE_PATTERNS.join('\n'))