Gradle Toolchain "No compatible toolchains found" (Detection) - Fix in CI

Gradle could not find an installed JDK matching a Java toolchain request, and auto-download is off (or could not run), so it failed. Unlike a download failure, this is purely about detection - the matching JDK is not installed where Gradle looks, and Gradle was told not to fetch one.

What this error means

The build fails with No compatible toolchains found for request specification: {languageVersion=21, ...} (auto-detect false, auto-download false). A JDK 21 may even be installed, but Gradle is not detecting it.

gradle output

> No compatible toolchains found for request specification:
  {languageVersion=21, vendor=any, implementation=vendor-specific}
  (auto-detect false, auto-download false).

Common causes

Requested JDK not installed where Gradle detects

The toolchain languageVersion has no matching JDK in Gradle’s detected installations, so there is nothing to select.

Auto-detect/auto-download disabled

With org.gradle.java.installations.auto-detect=false (or auto-download off) Gradle will neither scan standard locations nor fetch a JDK, so an uninstalled toolchain simply fails.

How to fix it

Install the JDK and point Gradle at it

Provision the requested JDK and pass its path via the installations property.

.github/workflows/ci.yml

- uses: actions/setup-java@v4
  with:
    distribution: temurin
    java-version: '21'
- run: ./gradlew build \
    -Dorg.gradle.java.installations.paths=$JAVA_HOME

Re-enable detection (or auto-download)

Let Gradle scan standard install locations, or allow it to download a matching JDK.

gradle.properties

# gradle.properties
org.gradle.java.installations.auto-detect=true
# optionally allow download (needs a resolver plugin):
org.gradle.java.installations.auto-download=true

How to prevent it

Install the toolchain JDK in CI and pass org.gradle.java.installations.paths.
Keep auto-detect on, or configure a download resolver, so toolchains can resolve.
Assert the toolchain resolves early (e.g. ./gradlew javaToolchains).