@@ -103,11 +103,17 @@ export async function buildAction(actionContext: BuildActionContext): Promise<Ex
       let bundleOutput: BundleEntryPointsOutput;
       try {
         [bundleOutput] = await Promise.all([
-          bundleEntryPoints(itemsToBundle, esmFiles, dtsFiles, {
-            ...options,
-            declarationMap,
-            compilationMode,
-          }),
+          bundleEntryPoints(
+            itemsToBundle,
+            esmFiles,
+            dtsFiles,
+            {
+              ...options,
+              declarationMap,
+              compilationMode,
+            },
+            buildState.previousBundleResults,
+          ),
           diagnosePromise,
         ]);
       } catch (error) {
 
@@ -81,50 +81,224 @@ interface MultiBundleOutput {
   warnings: string[];
 }
 
+/**
+ * Expands the selected entry points to include any available entry points whose module IDs
+ * transitively overlap with the selected set.
+ */
+function expandOverlappingEntryPoints(
+  selectedEntryPoints: readonly NormalizedEntryPoint[],
+  allEntryPoints: readonly NormalizedEntryPoint[],
+  isAvailable: (ep: NormalizedEntryPoint) => boolean,
+  getModuleIds: (ep: NormalizedEntryPoint) => ReadonlySet<string> | undefined,
+): readonly NormalizedEntryPoint[] {
+  assert(
+    selectedEntryPoints.length <= allEntryPoints.length,
+    'Selected entry points cannot exceed all entry points.',
+  );
+  if (selectedEntryPoints.length === allEntryPoints.length) {
+    return selectedEntryPoints;
+  }
+
+  const selected = new Set(selectedEntryPoints);
+  for (const ep of selected) {
+    const moduleIds = getModuleIds(ep);
+    if (!moduleIds?.size) {
+      continue;
+    }
+
+    for (const candidate of allEntryPoints) {
+      if (selected.has(candidate) || !isAvailable(candidate)) {
+        continue;
+      }
+
+      const candidateIds = getModuleIds(candidate);
+      if (candidateIds && !moduleIds.isDisjointFrom(candidateIds)) {
+        selected.add(candidate);
+      }
+    }
+  }
+
+  return selected.size > selectedEntryPoints.length
+    ? allEntryPoints.filter((ep) => selected.has(ep))
+    : selectedEntryPoints;
+}
+
+/**
+ * Checks whether any bundled entry point acquired a module ID that was not present in its
+ * previous bundle result.
+ */
+function hasNewlyAddedModules(
+  bundledEntryPoints: readonly NormalizedEntryPoint[],
+  output: MultiBundleOutput,
+  getPreviousModuleIds: (ep: NormalizedEntryPoint) => ReadonlySet<string> | undefined,
+): boolean {
+  for (const ep of bundledEntryPoints) {
+    const bundle = output.bundles.get(ep.bundleName);
+    assert(bundle, `Expected bundle output for entry point "${ep.bundleName}".`);
+
+    const prevIds = getPreviousModuleIds(ep);
+    if (!prevIds) {
+      return true;
+    }
+
+    for (const id of bundle.moduleIds) {
+      if (!prevIds.has(id)) {
+        return true;
+      }
+    }
+  }
+
+  return false;
+}
+
+/**
+ * Bundles dirty entry points for a single mode (ESM or DTS), automatically expanding the entry
+ * point set before or after bundling when module IDs overlap across entry points.
+ */
+async function bundleModeWithSharedModules(
+  dirtyEntryPoints: readonly NormalizedEntryPoint[],
+  allEntryPoints: readonly NormalizedEntryPoint[],
+  files: ReadonlyMap<string, string>,
+  dtsMode: boolean,
+  getPreviousModuleIds: (ep: NormalizedEntryPoint) => ReadonlySet<string> | undefined,
+  bundleFn: (
+    entryPoints: readonly NormalizedEntryPoint[],
+    files: ReadonlyMap<string, string>,
+    options: NormalizedLibraryOptions,
+  ) => Promise<MultiBundleOutput>,
+  options: NormalizedLibraryOptions,
+): Promise<MultiBundleOutput> {
+  if (dirtyEntryPoints.length === 0) {
+    return { filesToEmit: [], bundles: new Map(), warnings: [] };
+  }
+
+  if (dirtyEntryPoints.length === allEntryPoints.length) {
+    return bundleFn(dirtyEntryPoints, files, options);
+  }
+
+  const isAvailable = (ep: NormalizedEntryPoint): boolean =>
+    files.has(resolveEntryInputPath(ep.entryFilePath, dtsMode));
+
+  const initialEntryPoints = expandOverlappingEntryPoints(
+    dirtyEntryPoints,
+    allEntryPoints,
+    isAvailable,
+    getPreviousModuleIds,
+  );
+  const output = await bundleFn(initialEntryPoints, files, options);
+
+  if (
+    initialEntryPoints.length < allEntryPoints.length &&
+    hasNewlyAddedModules(initialEntryPoints, output, getPreviousModuleIds)
+  ) {
+    const expandedEntryPoints = expandOverlappingEntryPoints(
+      initialEntryPoints,
+      allEntryPoints,
+      isAvailable,
+      (ep) => output.bundles.get(ep.bundleName)?.moduleIds ?? getPreviousModuleIds(ep),
+    );
+
+    if (expandedEntryPoints.length > initialEntryPoints.length) {
+      return bundleFn(expandedEntryPoints, files, options);
+    }
+  }
+
+  return output;
+}
+
+/**
+ * Collects all normalized entry points from options and bundle input items.
+ */
+function getAllEntryPoints(
+  items: readonly BundleEntryPointInput[],
+  options: NormalizedLibraryOptions,
+): NormalizedEntryPoint[] {
+  const byName = new Map<string, NormalizedEntryPoint>();
+  if (options.entryPoints) {
+    for (const ep of options.entryPoints.values()) {
+      byName.set(ep.name, ep);
+    }
+  }
+  for (const item of items) {
+    byName.set(item.entryPoint.name, item.entryPoint);
+  }
+
+  return Array.from(byName.values());
+}
+
 /**
  * Bundles the compiled in-memory JavaScript and declaration files for all dirty entry points
- * using at most 2 Rolldown instances total (1 for all .mjs bundles, 1 for all .d.ts bundles).
+ * using at most 2 Rolldown instances per pass (1 for all .mjs bundles, 1 for all .d.ts bundles).
  *
  * @param items The collection of entry point inputs with change statuses.
  * @param esmFiles Map of virtual POSIX ESM output file paths to their content.
  * @param dtsFiles Map of virtual POSIX TypeScript declaration file paths to their content.
  * @param options The normalized library builder options with POSIX paths.
+ * @param previousBundleResults Optional map of entry point names to their previous bundle results.
  * @returns A promise resolving to the bundled output files and bundle cache results.
  */
 export async function bundleEntryPoints(
   items: readonly BundleEntryPointInput[],
   esmFiles: ReadonlyMap<string, string>,
   dtsFiles: ReadonlyMap<string, string>,
   options: NormalizedLibraryOptions,
+  previousBundleResults?: ReadonlyMap<string, BundleResult>,
 ): Promise<BundleEntryPointsOutput> {
   const bundleResults = new Map<string, BundleResult>();
   if (items.length === 0) {
     return { filesToEmit: [], bundleResults, warnings: [] };
   }
 
+  const allEntryPoints = getAllEntryPoints(items, options);
+  const itemsByName = new Map(items.map((item) => [item.entryPoint.name, item]));
+  const getPreviousResult = (name: string): BundleResult | undefined =>
+    itemsByName.get(name)?.previousBundleResult ?? previousBundleResults?.get(name);
+
   const esmEntryPoints: NormalizedEntryPoint[] = [];
   const dtsEntryPoints: NormalizedEntryPoint[] = [];
 
   for (const item of items) {
-    if (item.hasEsmChanges || !item.previousBundleResult) {
-      esmEntryPoints.push(item.entryPoint);
+    const { entryPoint } = item;
+    const previousBundleResult = getPreviousResult(entryPoint.name);
+    if (item.hasEsmChanges || !previousBundleResult) {
+      esmEntryPoints.push(entryPoint);
     }
-    if (item.hasDtsChanges || !item.previousBundleResult) {
-      dtsEntryPoints.push(item.entryPoint);
+    if (item.hasDtsChanges || !previousBundleResult) {
+      dtsEntryPoints.push(entryPoint);
     }
   }
 
   const [esmOutput, dtsOutput] = await Promise.all([
-    bundleAllEsm(esmEntryPoints, esmFiles, options),
-    bundleAllDts(dtsEntryPoints, dtsFiles, options),
+    bundleModeWithSharedModules(
+      esmEntryPoints,
+      allEntryPoints,
+      esmFiles,
+      false,
+      (ep) => getPreviousResult(ep.name)?.esmModuleIds,
+      bundleAllEsm,
+      options,
+    ),
+    bundleModeWithSharedModules(
+      dtsEntryPoints,
+      allEntryPoints,
+      dtsFiles,
+      true,
+      (ep) => getPreviousResult(ep.name)?.dtsModuleIds,
+      bundleAllDts,
+      options,
+    ),
   ]);
 
-  for (const { entryPoint, previousBundleResult } of items) {
-    const { bundleName, name } = entryPoint;
-    const esmBundle = esmOutput.bundles.get(bundleName);
-    const dtsBundle = dtsOutput.bundles.get(bundleName);
+  for (const entryPoint of allEntryPoints) {
+    const item = itemsByName.get(entryPoint.name);
+    const esmBundle = esmOutput.bundles.get(entryPoint.bundleName);
+    const dtsBundle = dtsOutput.bundles.get(entryPoint.bundleName);
+    if (!item && !esmBundle && !dtsBundle) {
+      continue;
+    }
 
-    bundleResults.set(name, {
+    const previousBundleResult = getPreviousResult(entryPoint.name);
+    bundleResults.set(entryPoint.name, {
       esmModuleIds: esmBundle?.moduleIds ?? previousBundleResult?.esmModuleIds ?? new Set(),
       dtsModuleIds: dtsBundle?.moduleIds ?? previousBundleResult?.dtsModuleIds ?? new Set(),
       esmOutputFiles: esmBundle?.outputFiles ?? previousBundleResult?.esmOutputFiles ?? new Set(),
@@ -140,6 +314,15 @@ export async function bundleEntryPoints(
   };
 }
 
+/**
+ * Resolves the compiled in-memory entry file path for a TypeScript entry point.
+ */
+function resolveEntryInputPath(entryFilePath: string, dtsMode: boolean): string {
+  return dtsMode
+    ? entryFilePath.replace(/\.(m?ts)$/, '.d.$1')
+    : entryFilePath.replace(/\.(m?)ts$/, '.$1js');
+}
+
 /**
  * Generates the Rolldown input mapping object from the specified entry points.
  *
@@ -153,9 +336,7 @@ function resolveEntryInputMap(
 ): Record<string, string> {
   const input: Record<string, string> = {};
   for (const { bundleName, entryFilePath } of entryPoints) {
-    input[bundleName] = dtsMode
-      ? entryFilePath.replace(/\.([cm]?ts)$/, '.d.$1')
-      : entryFilePath.replace(/\.([cm]?)ts$/, '.$1js');
+    input[bundleName] = resolveEntryInputPath(entryFilePath, dtsMode);
   }
 
   return input;
@@ -174,6 +355,8 @@ function createMemoryFileLoaderPlugin(
   extensions: readonly string[],
   includeMap: boolean,
 ): Plugin {
+  const isDts = extensions === DTS_EXTENSIONS;
+
   return {
     name: 'memory-file-loader',
     resolveId: {
@@ -187,28 +370,27 @@ function createMemoryFileLoaderPlugin(
           return files.has(id) ? { id, external: false } : undefined;
         }
 
-        if (id[0] !== '.' && !path.posix.isAbsolute(id)) {
+        if (id[0] !== '.' && !path.isAbsolute(id)) {
           return { id, external: true };
         }
 
         const resolved = id[0] === '.' ? path.posix.join(path.posix.dirname(importer), id) : id;
+        const normalizedResolved = resolved.replace(/\/+$/, '');
 
-        let resolvedCandidate: string | undefined;
-        if (files.has(resolved)) {
-          resolvedCandidate = resolved;
-        } else {
-          const base = resolved.replace(/\.[cm]?js$/, '');
-          for (const ext of extensions) {
-            const candidate = base + ext;
-            if (files.has(candidate)) {
-              resolvedCandidate = candidate;
-              break;
-            }
-          }
+        if (files.has(normalizedResolved)) {
+          return { id: normalizedResolved, external: false };
+        }
+
+        const base = normalizedResolved.replace(/\.m?js$/, '');
+        if (isDts && normalizedResolved.endsWith('.mjs') && files.has(`${base}.d.mts`)) {
+          return { id: `${base}.d.mts`, external: false };
         }
 
-        if (resolvedCandidate) {
-          return { id: resolvedCandidate, external: false };
+        for (const ext of extensions) {
+          const candidate = base + ext;
+          if (files.has(candidate)) {
+            return { id: candidate, external: false };
+          }
         }
 
         return undefined;