[Copilot]

Generate virtual-field helpers when an instrumentation module first transforms a matching class, rather than eagerly during agent startup. Libraries that never load avoid this work; libraries loaded later pay the one-time cost then.

In the Spring/JDK 25 bare-metal benchmark, median startup fell from about 4.96 s to 4.32 s in the first run and an independent confirmation, about 640 ms or 13% overall. HTTP readiness also improved by about 650 ms. These results are specific to this workload and configuration.

[opentelemetry-pr-dashboard]

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Waiting on the author · refreshed 2026-10-26 04:50 UTC

Move out of draft to request review.

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[Copilot]

🔵 Needs a closer look

Concurrent class-loading and bootstrap-injection behavior needs human validation beyond the publication-focused unit tests.

1 open issue

• Test that concurrent transformations share the published bundle · New

What changed in this PR

Defers virtual-field helper generation until an instrumentation module first transforms a matching class, avoiding generation for unused libraries.

Changes:

• Lazily generates and atomically publishes a reusable helper bundle.
• Preserves accessor-before-implementation injection order.
• Adds laziness and concurrency tests with a dedicated unit-test runtime configuration.

File	Description
javaagent-tooling/​src/​unitTests/​java/​io/​opentelemetry/​javaagent/​tooling/​field/​FieldBackedImplementationInstallerTest.java	Adds deferred-generation and concurrent-publication tests.
javaagent-tooling/​src/​main/​java/​io/​opentelemetry/​javaagent/​tooling/​field/​FieldBackedImplementationInstaller.java	Moves helper generation into transformation-time initialization.
javaagent-tooling/​build.gradle.kts	Registers the unit-test suite and excludes conflicting runtime dependencies.

_{Review effort: Balanced}

[Copilot]

🔵 Needs a closer look

Moving bootstrap helper generation into concurrent class transformation changes class-loading behavior and warrants final human review.

No open issues 🎉

1 resolved since last review

• Test that concurrent transformations share the published bundle

_{Review effort: Balanced}

[Copilot]

🔵 Needs a closer look

Moving shared helper generation into concurrent class-loading callbacks warrants human review of bootstrap initialization, despite no identified blocking defects.

No open issues 🎉

_{Review effort: Balanced}

[Copilot]

🔵 Needs a closer look

Moving shared helper initialization into live class transformations warrants human review of class-loading and concurrency behavior, although no concrete defect was identified.

No open issues 🎉

_{Review effort: Balanced}