diff --git a/MIGRATIONS.md b/MIGRATIONS.md
index c3e66de60..73f8ce733 100644
--- a/MIGRATIONS.md
+++ b/MIGRATIONS.md
@@ -4,6 +4,14 @@ Breaking changes and upgrade notes for downstream projects.
 
 ---
 
+## `test`/`test:unit` raise the heap ceiling to 8192 MB (2026-09-27)
+
+`--experimental-vm-modules` leaks ESM module registries between suites (upstream jest issue, present on jest 30); a large suite can hit Node's default ~4 GB old-space ceiling and OOM (not a test failure — the same suite passes clean at 8192). `NODE_OPTIONS` on every non-coverage test script (`test`, `test:unit`, `test:integration`, `test:e2e`, `test:all`, `test:watch`) now includes `--max-old-space-size=8192`; `:coverage` variants keep their own flags (#3948).
+
+**Action required:** `package.json` is project-owned (`--ours`, not part of the ISO merge) — if your suite is large enough to OOM under `--runInBand`, add the same flag to your project's `test`/`test:unit` scripts.
+
+---
+
 ## Removed unused APIs: `authorize()`, `requireFeatureFlag`, billing refund service (2026-09-26)
 
 Three APIs documented in earlier entries below had zero non-test callers in this repo. Removed as dead code (#3998).
diff --git a/package.json b/package.json
index fc32ed433..84141ec40 100644
--- a/package.json
+++ b/package.json
@@ -29,12 +29,12 @@
     "dev:env": "node --env-file-if-exists=.env --watch server.js",
     "debug": "nodemon --inspect server.js",
     "prod": "cross-env NODE_ENV=production node server.js --name=node",
-    "test": "cross-env NODE_ENV=test NODE_OPTIONS=--experimental-vm-modules jest --runInBand --testPathPatterns='unit'",
-    "test:all": "cross-env NODE_ENV=test NODE_OPTIONS=--experimental-vm-modules jest --runInBand",
-    "test:unit": "cross-env NODE_ENV=test NODE_OPTIONS=--experimental-vm-modules jest --runInBand --testPathPatterns='unit'",
-    "test:integration": "cross-env NODE_ENV=test NODE_OPTIONS=--experimental-vm-modules jest --runInBand --testPathPatterns='integration'",
-    "test:e2e": "cross-env NODE_ENV=test NODE_OPTIONS=--experimental-vm-modules jest --runInBand --testPathPatterns='e2e'",
-    "test:watch": "cross-env NODE_ENV=test NODE_OPTIONS=--experimental-vm-modules jest --watchAll",
+    "test": "cross-env NODE_ENV=test NODE_OPTIONS=\"--experimental-vm-modules --max-old-space-size=8192\" jest --runInBand --testPathPatterns='unit'",
+    "test:all": "cross-env NODE_ENV=test NODE_OPTIONS=\"--experimental-vm-modules --max-old-space-size=8192\" jest --runInBand",
+    "test:unit": "cross-env NODE_ENV=test NODE_OPTIONS=\"--experimental-vm-modules --max-old-space-size=8192\" jest --runInBand --testPathPatterns='unit'",
+    "test:integration": "cross-env NODE_ENV=test NODE_OPTIONS=\"--experimental-vm-modules --max-old-space-size=8192\" jest --runInBand --testPathPatterns='integration'",
+    "test:e2e": "cross-env NODE_ENV=test NODE_OPTIONS=\"--experimental-vm-modules --max-old-space-size=8192\" jest --runInBand --testPathPatterns='e2e'",
+    "test:watch": "cross-env NODE_ENV=test NODE_OPTIONS=\"--experimental-vm-modules --max-old-space-size=8192\" jest --watchAll",
     "test:coverage": "cross-env NODE_ENV=test NODE_OPTIONS=\"--experimental-vm-modules --max-old-space-size=6144 --expose-gc\" jest --coverage --maxWorkers=2",
     "test:unit:coverage": "cross-env NODE_ENV=test NODE_OPTIONS=\"--experimental-vm-modules --max-old-space-size=4096 --expose-gc\" jest --coverage --maxWorkers=2 --testPathPatterns='unit'",
     "test:integration:coverage": "cross-env NODE_ENV=test NODE_OPTIONS=\"--experimental-vm-modules --max-old-space-size=4096 --expose-gc\" jest --coverage --maxWorkers=2 --testPathPatterns='integration'",