Single-test flake amplifier recompiles the entire workspace under the constrained JVM flags.

Reported (UTC): 2026-07-15 04:31

What was being attempted: Run scripts/constrained-test.bash scratchPreFixWatchdogAdmissionExpiryDiscrimination 10 for BuildTestEmbedded, pinning the selected test plus a same-core spinner and setting JAVA_TOOL_OPTIONS=-XX:TieredStopAtLevel=1 as required for timeout-tail reproduction.

What went wrong: scripts/test.bash --test <one-name> compiled all 537 test scripts before executing the one selected test. Under one-core contention and C1, the first iteration produced no test output and did not complete after five minutes; the unconstrained equivalent took about 28 seconds and its output showed compilation diagnostics from the entire workspace.

Impact: The standard requested 10/10 or 5/5 constrained single-test verification multiplies whole-workspace compilation cost and can take hours, while the flags intended for the child test also penalize the compiler/launcher JVM. This blocks practical exhaustive flake amplification and encourages ad-hoc alternatives.

Workaround used: Use the normal selector for compile validation and inspect whether kompile-cli exposes a child-JVM-only flag; no sound compile-once constrained workaround was available in this repository.

Suggested durable fix: kompile-cli/test.bash should cache compiled tests independently of selection and provide a supported way to pass JVM flags and CPU affinity only to selected forked test JVMs, or expose a compile-once/run-selected-many command.

Production verification — 2026-07-17

Status: STILL EXISTS. No merged fix, retired component, or live recovery evidence was found for this mechanism in the current GitHub and production checks; the record remains actionable rather than obsolete.

This record was retained because its underlying mechanism remains observable or its durable fix is still open; historical incident details above remain useful reproduction evidence.