sbt "Extracting structure failed" in CI

A build-server or import step ran sbt to extract the project structure and sbt failed while loading the build. The underlying cause is a build.sbt or plugin error printed above the "Extracting structure failed" summary.

What this error means

A CI step that exports the build (bloopInstall, an IDE or build-server import) ends with "Extracting structure failed" after sbt printed a load error.

sbt

[error] Extracting structure failed: Build status: Error, see details below
[error] sbt.compiler.EvalException: Type error in expression
[error] Extract structure aborted

Common causes

build.sbt fails to evaluate

A type error, a missing setting, or a plugin that does not load makes sbt fail during build loading, and the extractor reports it as a structure failure.

A plugin version incompatible with the sbt version

A plugin in project/plugins.sbt that does not support the installed sbt version breaks build loading during extraction.

How to fix it

Fix the underlying build load error

Run sbt compile (or sbt reload) directly to see the real load error above the summary.
Correct the type error, missing setting, or bad import in build.sbt.
Re-run the extraction once the build loads cleanly.

Terminal

sbt reload

Align plugin and sbt versions

Pin plugin versions that are compatible with the sbt version in project/build.properties.

project/build.properties

// project/build.properties
sbt.version=1.9.9

How to prevent it

Run sbt reload locally after build.sbt changes to catch load errors.
Keep plugin versions compatible with the pinned sbt version.
Validate the build loads before running IDE/build-server imports in CI.