pin-r8-version

name	pin-r8-version
description	Pin R8 to a specific published dev release or to a particular commit on R8's `main` branch.

When to use this skill

Use this skill when overriding the R8 version bundled with AGP is necessary.

Check the current R8 version

To check the current R8 version bundled by AGP:

1. Run the minify task:

   ./gradlew :app:minifyProdReleaseWithR8 --rerun-tasks
   

2. Inspect the mapping header:

   head -5 android/app/build/outputs/mapping/prodRelease/mapping.txt
   

   Look at compiler_version (e.g. 9.4.6-dev, or main) and compiler_hash (a git commit SHA on R8's repo).

Locating an R8 version

Published dev releases (on a release branch)

R8 maintains release branches named 9.0, 9.1, …, 9.4, etc. Each release branch has commits like Version 9.4.6-dev, Version 9.4.7-dev, … Every such tagged version is published to Maven at https://storage.googleapis.com/r8-releases/raw under the coordinate com.android.tools:r8:<version>-dev.

List available branches:

curl -s "https://r8.googlesource.com/r8/+refs/heads?format=JSON" \
  | tail -c +6 \
  | jq -r 'keys[] | select(test("^[0-9]"))'

List recent commits on a specific release branch (replace 9.4):

curl -s "https://r8.googlesource.com/r8/+log/refs/heads/9.4?n=30&format=JSON" \
  | tail -c +6 \
  | jq -r '.log[] | "\(.commit[:12]) \(.message | split("\n")[0])"'

The Version X.Y.Z-dev commits mark released dev versions. Verify a specific one is actually published (should return HTTP 200):

curl -sI "https://storage.googleapis.com/r8-releases/raw/com/android/tools/r8/9.4.7-dev/r8-9.4.7-dev.pom" | head -1

Specific commits on main

R8 publishes every merged commit on main as a raw jar keyed by the full 40-character commit SHA. There is no maven POM — only the raw jar file.

List recent commits on main:

curl -s "https://r8.googlesource.com/r8/+log/refs/heads/main?n=30&format=JSON" \
  | tail -c +6 \
  | jq -r '.log[] | "\(.commit) \(.message | split("\n")[0])"'

Verify a specific commit's jar is published (should return HTTP 200):

curl -sI "https://storage.googleapis.com/r8-releases/raw/main/<FULL_40_CHAR_SHA>/r8.jar" | head -1

Applying the pin

Add a buildscript block after the dependencyResolutionManagement block in the root settings.gradle.kts.

Option A — published dev release (Maven layout)

buildscript {
    repositories {
        maven("https://storage.googleapis.com/r8-releases/raw") {
            content { includeModule("com.android.tools", "r8") }
        }
    }
    dependencies {
        classpath("com.android.tools:r8:9.4.7-dev")
    }
}

Option B — specific commit on main (raw jar via ivy)

Main-branch builds don't publish a POM, so an ivy repository with a custom pattern is required. [revision] here is the full 40-character SHA.

buildscript {
    repositories {
        ivy("https://storage.googleapis.com/r8-releases/raw/main") {
            patternLayout {
                artifact("[revision]/[artifact].[ext]")
            }
            metadataSources { artifact() }
            content { includeModule("com.android.tools", "r8") }
        }
    }
    dependencies {
        classpath("com.android.tools:r8:297e591e1842089b281de5d5286760eca4f5c944")
    }
}

Verifying the pin took effect

1. Re-run the minify task:

   ./gradlew :app:minifyProdReleaseWithR8 --rerun-tasks
   

2. Inspect the mapping header:

   head -5 android/app/build/outputs/mapping/prodRelease/mapping.txt
   

   Confirm both:

   • compiler_version — will be X.Y.Z-dev for Option A, or literally main for Option B.
   • compiler_hash — matches the release commit (Option A) or the exact SHA you pinned (Option B).

Reference URLs

• R8 git browser: https://r8.googlesource.com/r8/
• R8 raw storage bucket root: https://storage.googleapis.com/r8-releases/raw/