fix(iOS): stamp the React Native version in the composed prebuilt headers

The prebuilt iOS core artifacts shipped ReactNativeVersion.h with the
1000.0.0 dev sentinel: the compose-xcframework job re-derives the shipped
headers from its own fresh (unstamped) checkout, while only build-rn-slice
runs set-rn-artifacts-version.js. Since the header-facades change,
libraries resolve the prebuilt header instead of the stamped npm copy, so
any library gating on REACT_NATIVE_VERSION_MAJOR/MINOR compiles the wrong
branch (react-native-unistyles in nightly-tests).

Rather than re-stamp (and then revert) the compose checkout, source just
that one build-stamped header's CONTENT from the built header tree the
compose job already downloads (.build/headers): stageEntries now takes an
overlay dir and, for ReactNativeVersion.h only, prefers the built copy
(stamped in the slice job) over the source sentinel. Header LAYOUT is
still spec-derived from source, and every other header still copies from
source, so a stale build tree can never ship wrong header content. Bump
the compose cache key so pre-fix unstamped composed artifacts are not
served.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

Author: chrfalch

.github/workflows/prebuild-ios-core.yml

@@ -133,7 +133,7 @@ jobs:
         uses: actions/cache/restore@v5
         with:
           path: packages/react-native/.build/output/xcframeworks
-          key: v3-ios-core-xcframework-${{ matrix.flavor }}-${{ hashFiles('packages/react-native/Package.swift', 'packages/react-native/scripts/ios-prebuild/*.js', 'packages/react-native/scripts/ios-prebuild.js', 'packages/react-native/React/**/*', 'packages/react-native/ReactCommon/**/*', 'packages/react-native/Libraries/**/*') }}
+          key: v4-ios-core-xcframework-${{ matrix.flavor }}-${{ hashFiles('packages/react-native/Package.swift', 'packages/react-native/scripts/ios-prebuild/*.js', 'packages/react-native/scripts/ios-prebuild.js', 'packages/react-native/React/**/*', 'packages/react-native/ReactCommon/**/*', 'packages/react-native/Libraries/**/*') }}
       - name: Setup node.js
         if: steps.restore-ios-xcframework.outputs.cache-hit != 'true'
         uses: ./.github/actions/setup-node
@@ -246,4 +246,4 @@ jobs:
             packages/react-native/.build/output/xcframeworks/ReactCore${{matrix.flavor}}.xcframework.tar.gz
             packages/react-native/.build/output/xcframeworks/ReactCore${{matrix.flavor}}.framework.dSYM.tar.gz
             packages/react-native/.build/output/xcframeworks/ReactNativeHeaders${{matrix.flavor}}.xcframework.tar.gz
-          key: v3-ios-core-xcframework-${{ matrix.flavor }}-${{ hashFiles('packages/react-native/Package.swift', 'packages/react-native/scripts/ios-prebuild/*.js', 'packages/react-native/scripts/ios-prebuild.js', 'packages/react-native/React/**/*', 'packages/react-native/ReactCommon/**/*', 'packages/react-native/Libraries/**/*') }}
+          key: v4-ios-core-xcframework-${{ matrix.flavor }}-${{ hashFiles('packages/react-native/Package.swift', 'packages/react-native/scripts/ios-prebuild/*.js', 'packages/react-native/scripts/ios-prebuild.js', 'packages/react-native/React/**/*', 'packages/react-native/ReactCommon/**/*', 'packages/react-native/Libraries/**/*') }}

packages/react-native/scripts/ios-prebuild/headers-compose.js

@@ -114,6 +114,7 @@ function stageEntries(
   stage /*: string */,
   entries /*: Array<SpecEntry> */,
   rnRoot /*: string */,
+  overlayDir /*: ?string */ = null,
 ) /*: void */ {
   for (const e of entries) {
     const dest = path.join(stage, e.relPath);
@@ -129,7 +130,24 @@ function stageEntries(
           `#import <${e.redirectTo}>\n`,
       );
     } else {
-      fs.copyFileSync(path.join(rnRoot, e.source), dest);
+      // ReactNativeVersion.h is the one shipped header STAMPED at build time:
+      // the slice job runs set-rn-artifacts-version before building, while the
+      // source tree keeps the 1000.0.0 dev sentinel. Take just this file's
+      // content from the built header tree (`overlayDir`, i.e. `.build/headers`)
+      // when present, so the compose ships the real version without re-stamping
+      // its own checkout. Every OTHER header is authoritative in the source
+      // tree (only the layout is spec-derived), so it always copies from
+      // source — never from a build tree that could be stale relative to it.
+      const isStamped = path.basename(e.source) === 'ReactNativeVersion.h';
+      const overlaySource =
+        isStamped && overlayDir != null
+          ? path.join(overlayDir, e.source)
+          : null;
+      const src =
+        overlaySource != null && fs.existsSync(overlaySource)
+          ? overlaySource
+          : path.join(rnRoot, e.source);
+      fs.copyFileSync(src, dest);
     }
   }
 }
@@ -145,11 +163,12 @@ function emitReactFrameworkHeaders(
   xcfwPath /*: string */,
   plan /*: HeadersSpecPlan */,
   rnRoot /*: string */,
+  overlayDir /*: ?string */ = null,
 ) /*: void */ {
   const stage = fs.mkdtempSync(
     path.join(path.dirname(xcfwPath), '.react-stage-'),
   );
-  stageEntries(stage, plan.react, rnRoot);
+  stageEntries(stage, plan.react, rnRoot, overlayDir);
   fs.writeFileSync(
     path.join(stage, 'React-umbrella.h'),
     renderUmbrellaHeader(plan.umbrella),
@@ -239,10 +258,11 @@ function buildReactNativeHeadersXcframework(
   // namespace so `<hermes/...>` resolves without per-library wiring. null
   // when unstaged — then `<hermes/...>` stays unavailable.
   hermesHeaders /*: ?string */ = null,
+  overlayDir /*: ?string */ = null,
 ) /*: string */ {
   // ---- stage headers ----
   const stage = fs.mkdtempSync(path.join(outDir, '.rnh-stage-'));
-  stageEntries(stage, plan.reactNativeHeaders, rnRoot);
+  stageEntries(stage, plan.reactNativeHeaders, rnRoot, overlayDir);
   // Hermes public headers (separate source from the deps namespaces — they
   // come from the hermes-ios tarball, not ReactNativeDependencies). Vend only
   // the `hermes/` namespace; `jsi/` is already provided elsewhere, so copying

packages/react-native/scripts/ios-prebuild/xcframework.js

@@ -87,7 +87,14 @@ function buildXCFrameworks(
     emitReactFrameworkHeaders,
   } = require('./headers-compose');
   const plan = computeSpecPlan(rootFolder);
-  emitReactFrameworkHeaders(outputPath, plan, rootFolder);
+  // Built header tree from the slice jobs (downloaded to `.build/headers`).
+  // When present, the compose sources header CONTENT from here (see
+  // stageEntries) so build-time generated/stamped headers — notably the
+  // version-stamped ReactNativeVersion.h — ship without re-stamping this
+  // checkout. Absent (e.g. a local compose with no prior build) → source tree.
+  const builtHeadersDir = path.join(buildFolder, 'headers');
+  const overlayDir = fs.existsSync(builtHeadersDir) ? builtHeadersDir : null;
+  emitReactFrameworkHeaders(outputPath, plan, rootFolder, overlayDir);
   // ReactNativeHeaders is PURE-RN — the third-party deps namespaces ship in
   // the ReactNativeDependenciesHeaders sidecar built by the deps prebuild
   // (scripts/releases/ios-prebuild), so the core compose no longer needs the
@@ -115,6 +122,7 @@ function buildXCFrameworks(
     rootFolder,
     true, // include the mac-catalyst slice in the real compose
     hermesHeaders,
+    overlayDir,
   );
 
   if (identity) {