@@ -0,0 +1,14 @@
+---
+'@objectstack/core': patch
+---
+
+fix(core): one declaration serves both module formats, so the export map hands each condition its own `types`
+
+Clause-②: no
+Metadata-protocol: none
+
+`@objectstack/core` used to emit two separate declarations of every class, `dist/index.d.ts` and `dist/index.d.cts`, and its export map served the ESM-kind `index.d.ts` to both conditions, so a TypeScript consumer resolving `require` was told the package is ESM (attw `FalseESM` on `.` and `./logger`). Serving the `.d.cts` to `require` was not possible while the two files declared `ObjectKernel` twice: its `private plugins` member makes the two copies incompatible types for any program that reaches core through both resolution modes.
+
+Core's declaration build now runs once, for the ESM format. `dist/index.d.ts` and `dist/logger.d.ts` carry the declarations, as before, and `dist/index.d.cts` and `dist/logger.d.cts` are one-line re-exports of them, so both conditions hand out the same classes. `exports` now gives types per condition, `{ import: { types, default }, require: { types, default } }`, on both subpaths. No subpath is added or removed, no JavaScript file changes, and the `dist` file names are unchanged.
+
+A CommonJS consumer compiling with `module: node16` (or, measured on TypeScript 5.6, under `nodenext` too) used to get TS1479 at its own `import ... from '@objectstack/core'`. That diagnostic now sits inside core's `.d.cts`, where `skipLibCheck` silences it. Nothing else for a consumer to do.
@@ -9,14 +9,24 @@
   "sideEffects": false,
   "exports": {
     ".": {
-      "types": "./dist/index.d.ts",
-      "import": "./dist/index.js",
-      "require": "./dist/index.cjs"
+      "import": {
+        "types": "./dist/index.d.ts",
+        "default": "./dist/index.js"
+      },
+      "require": {
+        "types": "./dist/index.d.cts",
+        "default": "./dist/index.cjs"
+      }
     },
     "./logger": {
-      "types": "./dist/logger.d.ts",
-      "import": "./dist/logger.js",
-      "require": "./dist/logger.cjs"
+      "import": {
+        "types": "./dist/logger.d.ts",
+        "default": "./dist/logger.js"
+      },
+      "require": {
+        "types": "./dist/logger.d.cts",
+        "default": "./dist/logger.cjs"
+      }
     }
   },
   "scripts": {
 
@@ -1,4 +1,6 @@
-import { defineConfig } from 'tsup';
+import { writeFile } from 'node:fs/promises';
+
+import { defineConfig, type Options } from 'tsup';
 
 import { dropSourcesContent } from '../../scripts/tsup-drop-sources-content.mjs';
 
@@ -10,13 +12,65 @@ import { dropSourcesContent } from '../../scripts/tsup-drop-sources-content.mjs'
  *   so importing the client SDK in a browser bundle does NOT drag in
  *   Node-only kernel internals (e.g. `process.cpuUsage()`).
  */
-export default defineConfig({
-  entry: ['src/index.ts', 'src/logger.ts'],
+const ENTRY_NAMES = ['index', 'logger'] as const;
+const emitDts = !process.env.OS_SKIP_DTS;
+
+const shared: Options = {
+  entry: ENTRY_NAMES.map((name) => `src/${name}.ts`),
   splitting: false,
   sourcemap: true,
-  clean: true,
-  dts: !process.env.OS_SKIP_DTS,
-  format: ['esm', 'cjs'],
   target: 'es2020',
   esbuildOptions: dropSourcesContent,
-});
+};
+
+/**
+ * ONE declaration per entry, shared by both formats.
+ *
+ * tsup's own `dts` emits a declaration per FORMAT — `index.d.ts` beside the ESM
+ * build and `index.d.cts` beside the CJS one — and those are two separate
+ * declarations of every class. TypeScript compares a class with a `private`
+ * member nominally, so `ObjectKernel` (which carries `private plugins` and
+ * reaches every plugin through `PluginContext.getKernel()`) becomes two
+ * incompatible types for any compilation that reaches core through both
+ * resolution modes, the moment the export map serves each format its own
+ * declaration. Measured: per-condition `types` over the twin declarations
+ * fail `pnpm --filter @objectstack/plugin-dev build` with TS2345 in
+ * `src/dev-plugin.ts` (its CommonJS build `await import()`s
+ * `@objectstack/objectql`, which reaches core the other way).
+ *
+ * So the declaration pass runs once, for ESM only, and the CommonJS
+ * `index.d.cts` is a one-line re-export of `index.d.ts`: each condition is
+ * still handed a declaration of its own module kind (attw: no `FalseESM`), but
+ * every class in both IS the `.d.ts` one, and what that declaration imports
+ * from `@objectstack/spec` resolves exactly as it did when both conditions
+ * read the `.d.ts`. ⛔ Not the other way round: with the declarations in the
+ * `.d.cts` and the `.d.ts` re-exporting it, core's own imports of spec resolve
+ * through spec's `require` condition, and spec's twin declarations then fail
+ * `@objectstack/driver-memory`'s build (TS2345, `ComposedReadableIds` against
+ * itself). The `.d.cts` → `.d.ts` re-export is TS1479 inside this package's
+ * file for a consumer on `module: node16` (or on TypeScript 5.6 under
+ * `nodenext`), which `skipLibCheck` silences; the single `types` entry this
+ * replaces raised that same TS1479 at the consumer's own import, where no
+ * option silences it.
+ *
+ * The JS half's `onSuccess` writes the `.d.cts` files and the declaration half
+ * never emits one, so the two halves (which tsup runs concurrently) never
+ * write the same file. `clean` lives on the JS half only: tsup's clean keeps
+ * declaration files, so it cannot delete what the declaration half writes.
+ */
+export default defineConfig([
+  {
+    ...shared,
+    clean: true,
+    dts: false,
+    format: ['esm', 'cjs'],
+    onSuccess: emitDts
+      ? async () => {
+          await Promise.all(
+            ENTRY_NAMES.map((name) => writeFile(`dist/${name}.d.cts`, `export * from './${name}.js';\n`)),
+          );
+        }
+      : undefined,
+  },
+  ...(emitDts ? [{ ...shared, clean: false, dts: { only: true }, format: ['esm'] } satisfies Options] : []),
+]);
@@ -440,23 +440,15 @@ const DUAL_FORMAT_BEHAVIOUR_PROBES = [
  * the type axis, and it is a property of the DEPENDENCY, never of the consumer
  * that trips over it.
  *
- * `@objectstack/core` is where the repo actually meets it. `ObjectKernel`
- * carries `private plugins` and travels through `PluginContext.getKernel()`
- * into every plugin's `init`, so the moment core ships two declarations, any
- * compilation that reaches core through BOTH resolution modes sees two
- * `ObjectKernel`s. Measured on this branch, whole-repo `pnpm build`:
- *
- *   28 packages split (core included)      RED — @objectstack/verify, 5 × TS2345
- *   27 packages split (core held back)     GREEN — 71/71 tasks
- *   28 + the 37-package ESM mirror         RED — @objectstack/plugin-dev, TS2345
- *
- * The mirror round is the informative one: it moves the failure rather than
- * removing it. Splitting `@objectstack/objectql` is what fixes `verify` and
- * what breaks `plugin-dev`, because a split dependency resolves core one way
- * from its `.d.mts` and the other from its `.d.ts`. So the exemption is not
- * "core is hard", it is: **core cannot be split until `ObjectKernel`'s
- * identity stops being nominal**, and that is a decision about core's public
- * types, not about an exports map.
+ * `@objectstack/core` is where the repo met it: `ObjectKernel` carries
+ * `private plugins` and travels through `PluginContext.getKernel()` into every
+ * plugin's `init`, so twin declarations of core broke any compilation that
+ * reaches core through BOTH resolution modes (`@objectstack/plugin-dev`'s
+ * CommonJS build, TS2345). The cure is at the dependency, not in this table:
+ * core's declaration pass runs once and its other-format declaration is a
+ * one-line re-export of it (`packages/core/tsup.config.ts`), so both
+ * conditions hand out the SAME classes. A package that meets the hazard again
+ * takes that cure first; a row here is for an entry that cannot.
  *
  * ⛔ An exemption here is NOT a quieter red. It is a declaration that the
  * entry's `.d.cts` ships unreachable ON PURPOSE, with the measurement that
@@ -466,14 +458,7 @@ const DUAL_FORMAT_BEHAVIOUR_PROBES = [
  *
  * @type {Record<string, {reason: string}>}
  */
-const TYPED_EXEMPTIONS = Object.freeze({
-  '@objectstack/core#.': {
-    reason: 'Splitting core\'s declarations gives `ObjectKernel` (which carries `private plugins`) two nominal identities, and it crosses every plugin boundary via `PluginContext.getKernel()`. Measured: with core split, `pnpm build` fails in @objectstack/verify with 5 × TS2345; with core held back and the other 27 packages split, 71/71 tasks pass. Blocked on a decision about core\'s public types, not on this exports map (#13112).',
-  },
-  '@objectstack/core#./logger': {
-    reason: 'Same declaration set as `@objectstack/core#.` — the subpath is emitted from the same tsup pass and splits the same identities. Held back with its sibling so core has one resolution story rather than two (#13112).',
-  },
-});
+const TYPED_EXEMPTIONS = Object.freeze({});
 
 const EXIT_OK = 0;
 const EXIT_FINDINGS = 1;