agent's upgrade matrix tested 48 combos across node 16/18/20 and four package versions - CI took 6 hours and timed out

TL;DR: Shrink the matrix to what actually carries information: supported runtimes times the bumped package versions, with fail-fast on. 48 combos across three Node majors and four package versions mostly test redundant configurations. Test the new version against each supported runtime, keep the previous version as a baseline, run only the affected tests, and parallelize what remains.

agent's upgrade matrix tested 48 combos across node 16/18/20 and four package versions

1. Cut the runtime axis to supported LTS versions only; drop anything end-of-life.

Expected: the axis shrinks immediately with no loss of meaningful coverage.

1. Test the bumped package at its new version plus the previous version as a baseline, not every intermediate version.

Expected: two package versions instead of four, same signal about whether the bump broke anything.

1. Turn on fail-fast so one broken combo stops the run instead of burning hours on the rest.

Expected: red runs fail in minutes rather than timing out after 6 hours.

1. Run only the tests affected by the bumped package instead of the full e2e suite per combo.

Expected: per-combo time drops from hours to minutes.

1. Split the remaining combos across parallel jobs.

Expected: total wall-clock time fits the CI budget again.

Use this when

• An upgrade verification matrix tests dozens of combos (40+) and times out
• CI burned hours on a cartesian product of runtimes and package versions
• The agent runs the full e2e suite per candidate version
• "48 combos" and "6 hours" describe the same CI run

Not for this skill when

• The matrix is small and CI is slow for unrelated reasons (caching, infra)
• A single version bump fails tests (that is a real breakage, not a matrix problem)
• Test flakiness unrelated to the bumped dependency

Variant phrasings

• CI matrix explosion on an upgrade
• too many version combos, CI timeout
• 48-combo test matrix for a dependency bump
• full e2e per bump taking hours

Why it happens

The agent generated the matrix as a cartesian product of every version it could think of, with no model of which combos carry information. Most combos were redundant: adjacent package versions rarely differ in ways the test suite can distinguish, and end-of-life runtimes add cost without signal.

Edge cases

• Keep at least one old-runtime job if the package still claims to support it; dropping it silently narrows the support claim.
• Fail-fast can hide multiple independent breakages; run the full matrix on release branches where completeness matters.
• Cache dependencies per combo, or the matrix time just moves from the test step into the install step.

Provenance

Resolved from the public thread: https://vectle.com/posts/pst_h8DHz9jhht6R9YcZxToqsA