diff --git a/scripts/dev/webpack-config-light.test.cjs b/scripts/dev/webpack-config-light.test.cjs
index 38301c192..eab250329 100644
--- a/scripts/dev/webpack-config-light.test.cjs
+++ b/scripts/dev/webpack-config-light.test.cjs
@@ -49,6 +49,41 @@ test("light dev disables webpack dev-server browser client", () => {
   assert.equal(htmlPlugin?.userOptions?.retryMainScriptLoad, false);
 });
 
+test("development cache stays memory-only and bounded to one generation", () => {
+  for (const lightDev of [false, true]) {
+    const config = withEnv(
+      {
+        ORGII_LIGHT_DEV: lightDev ? "true" : null,
+        FAST_DEV: lightDev ? "true" : null,
+        DEV_SOURCEMAPS: lightDev ? "false" : null,
+      },
+      () => createWebpackConfig({}, { mode: "development" })
+    );
+
+    assert.deepEqual(config.cache, {
+      type: "memory",
+      maxGenerations: 1,
+    });
+  }
+});
+
+test("production keeps its isolated filesystem cache", () => {
+  for (const fastProd of [false, true]) {
+    const config = withEnv(
+      {
+        FAST_PROD: fastProd ? "true" : null,
+      },
+      () => createWebpackConfig({}, { mode: "production" })
+    );
+
+    assert.equal(config.cache.type, "filesystem");
+    assert.equal(
+      config.cache.version,
+      `${fastProd ? "prod-fast" : "prod"}-11`
+    );
+  }
+});
+
 test("retrying main script loader disables static HTML injection in dev", () => {
   const config = withEnv(
     {
diff --git a/webpack.config.js b/webpack.config.js
index 0ad0e91df..989233200 100644
--- a/webpack.config.js
+++ b/webpack.config.js
@@ -62,24 +62,32 @@ module.exports = (env, argv) => {
       chunkFilename: isProduction ? "[name].[contenthash].js" : "[name].js",
       clean: true,
     },
-    cache: {
-      type: "filesystem",
-      // FAST_PROD swaps both the transpiler and minimizer. Keep it in a
-      // separate filesystem-cache namespace so webpack cannot reuse cached
-      // runtime-condition code generated by the regular production pipeline.
-      // Mixing those caches can leave async chunks guarded by a stale runtime
-      // id (for example `__webpack_require__.j == 9121` while the emitted
-      // runtime id is `49121`), which turns otherwise valid imports into
-      // `undefined` only in the packaged app.
-      version: `${
-        isProduction ? (useFastProd ? "prod-fast" : "prod") : "dev"
-      }-11`,
-      buildDependencies: {
-        config: [__filename],
-      },
-      // Don't compress - avoids sass serialization issues
-      compression: false,
-    },
+    cache: isProduction
+      ? {
+          type: "filesystem",
+          // FAST_PROD swaps both the transpiler and minimizer. Keep it in a
+          // separate filesystem-cache namespace so webpack cannot reuse cached
+          // runtime-condition code generated by the regular production pipeline.
+          // Mixing those caches can leave async chunks guarded by a stale runtime
+          // id (for example `__webpack_require__.j == 9121` while the emitted
+          // runtime id is `49121`), which turns otherwise valid imports into
+          // `undefined` only in the packaged app.
+          version: `${useFastProd ? "prod-fast" : "prod"}-11`,
+          buildDependencies: {
+            config: [__filename],
+          },
+          // Don't compress - avoids sass serialization issues
+          compression: false,
+        }
+      : {
+          // Webpack's filesystem cache serialized 1–4+ GB pack files for this
+          // app and deserializing them pushed the long-lived dev server to a
+          // 7–9 GB physical footprint. Dev mode already keeps the active
+          // compilation graph in memory, so retain only one unused generation
+          // for rebuilds and never persist that graph across process restarts.
+          type: "memory",
+          maxGenerations: 1,
+        },
     // Snapshot: use timestamps for node_modules instead of content hashing.
     // node_modules rarely change during a dev session; timestamp checks are much faster.
     snapshot: {