diff --git a/packages/addon-shim/package.json b/packages/addon-shim/package.json
index f80863a59..23cab53e8 100644
--- a/packages/addon-shim/package.json
+++ b/packages/addon-shim/package.json
@@ -19,9 +19,11 @@
   "dependencies": {
     "@embroider/shared-internals": "workspace:^",
     "broccoli-funnel": "^3.0.8",
+    "common-ancestor-path": "^1.0.1",
     "semver": "^7.3.8"
   },
   "devDependencies": {
+    "@types/common-ancestor-path": "^1.0.2",
     "@types/semver": "^7.3.6",
     "broccoli-node-api": "^1.7.0",
     "typescript": "^5.1.6",
diff --git a/packages/addon-shim/src/index.ts b/packages/addon-shim/src/index.ts
index 05038a4fe..663285729 100644
--- a/packages/addon-shim/src/index.ts
+++ b/packages/addon-shim/src/index.ts
@@ -1,13 +1,13 @@
-import { resolve, relative, isAbsolute } from 'path';
-import { readFileSync } from 'fs';
 import {
-  AddonMeta,
   AddonInstance,
-  isDeepAddonInstance,
+  AddonMeta,
   PackageInfo,
+  isDeepAddonInstance,
 } from '@embroider/shared-internals';
 import buildFunnel from 'broccoli-funnel';
-import type { Node } from 'broccoli-node-api';
+import commonAncestorPath from 'common-ancestor-path';
+import { readFileSync } from 'fs';
+import { dirname, isAbsolute, join, normalize, relative, resolve } from 'path';
 import { satisfies } from 'semver';
 
 export interface ShimOptions {
@@ -29,15 +29,46 @@ export function addonV1Shim(directory: string, options: ShimOptions = {}) {
 
   let meta = addonMeta(pkg);
   let disabled = false;
-  const rootTrees = new WeakMap<AddonInstance, Node>();
 
-  function rootTree(addonInstance: AddonInstance): Node {
-    let tree = rootTrees.get(addonInstance);
-    if (!tree) {
-      tree = addonInstance.treeGenerator(directory);
-      rootTrees.set(addonInstance, tree);
+  function treeFor(
+    addonInstance: AddonInstance,
+    resourceMap: Record<string, string>,
+    // default expectation is for resourceMap to map from interior to exterior, swap if needed
+    swapInteriorExterior = false
+  ) {
+    const absoluteInteriorPaths = Object[
+      swapInteriorExterior ? 'values' : 'keys'
+    ](resourceMap).map((internalPath) => join(directory, internalPath));
+
+    if (absoluteInteriorPaths.length === 0) {
+      return;
     }
-    return tree;
+
+    const ancestorPath =
+      commonAncestorPath(...absoluteInteriorPaths.map(dirname)) ?? directory;
+    const ancestorPathRel = relative(directory, ancestorPath);
+    const ancestorTree = addonInstance.treeGenerator(ancestorPath);
+    const relativeInteriorPaths = absoluteInteriorPaths.map((absPath) =>
+      relative(ancestorPath, absPath)
+    );
+
+    return buildFunnel(ancestorTree, {
+      files: relativeInteriorPaths,
+      getDestinationPath(relativePath: string): string {
+        for (let [a, b] of Object.entries(resourceMap)) {
+          const interiorName = swapInteriorExterior ? b : a;
+          const exteriorName = swapInteriorExterior ? a : b;
+          if (join(ancestorPathRel, relativePath) === normalize(interiorName)) {
+            return exteriorName;
+          }
+        }
+        throw new Error(
+          `bug in addonV1Shim, no match for ${relativePath} in ${JSON.stringify(
+            resourceMap
+          )}`
+        );
+      },
+    });
   }
 
   return {
@@ -72,22 +103,7 @@ export function addonV1Shim(directory: string, options: ShimOptions = {}) {
       }
       let maybeAppJS = meta['app-js'];
       if (maybeAppJS) {
-        const appJS = maybeAppJS;
-        return buildFunnel(rootTree(this), {
-          files: Object.values(appJS),
-          getDestinationPath(relativePath: string): string {
-            for (let [exteriorName, interiorName] of Object.entries(appJS)) {
-              if (relativePath === interiorName) {
-                return exteriorName;
-              }
-            }
-            throw new Error(
-              `bug in addonV1Shim, no match for ${relativePath} in ${JSON.stringify(
-                appJS
-              )}`
-            );
-          },
-        });
+        return treeFor(this, maybeAppJS, true);
       }
     },
 
@@ -104,22 +120,7 @@ export function addonV1Shim(directory: string, options: ShimOptions = {}) {
       }
       let maybeAssets = meta['public-assets'];
       if (maybeAssets) {
-        const assets = maybeAssets;
-        return buildFunnel(rootTree(this), {
-          files: Object.keys(assets),
-          getDestinationPath(relativePath: string): string {
-            for (let [interiorName, exteriorName] of Object.entries(assets)) {
-              if (relativePath === interiorName) {
-                return exteriorName;
-              }
-            }
-            throw new Error(
-              `bug in addonV1Shim, no match for ${relativePath} in ${JSON.stringify(
-                assets
-              )}`
-            );
-          },
-        });
+        return treeFor(this, maybeAssets);
       }
     },
 
diff --git a/pnpm-lock.yaml b/pnpm-lock.yaml
index 5c86c0356..b318e6e06 100644
--- a/pnpm-lock.yaml
+++ b/pnpm-lock.yaml
@@ -117,10 +117,16 @@ importers:
       broccoli-funnel:
         specifier: ^3.0.8
         version: 3.0.8
+      common-ancestor-path:
+        specifier: ^1.0.1
+        version: 1.0.1
       semver:
         specifier: ^7.3.8
         version: 7.6.1
     devDependencies:
+      '@types/common-ancestor-path':
+        specifier: ^1.0.2
+        version: 1.0.2
       '@types/semver':
         specifier: ^7.3.6
         version: 7.5.8
@@ -6499,6 +6505,10 @@ packages:
   /@types/chai@4.3.16:
     resolution: {integrity: sha512-PatH4iOdyh3MyWtmHVFXLWCCIhUbopaltqddG9BzB+gMIzee2MJrvd+jouii9Z3wzQJruGWAm7WOMjgfG8hQlQ==}
 
+  /@types/common-ancestor-path@1.0.2:
+    resolution: {integrity: sha512-8llyULydTb7nM9yfiW78n6id3cet+qnATPV3R44yIywxgBaa8QXFSM9QTMf4OH64QOB45BlgZ3/oL4mmFLztQw==}
+    dev: true
+
   /@types/connect@3.4.38:
     resolution: {integrity: sha512-K6uROf1LD88uDQqJCktA4yzL1YYAK6NgfsI0v/mTgyPKWsX1CnJ0XPSDhViejru1GcRkLWb8RlzFYJRqGUbaug==}
     dependencies:
@@ -9764,6 +9774,10 @@ packages:
     engines: {node: '>= 12'}
     dev: true
 
+  /common-ancestor-path@1.0.1:
+    resolution: {integrity: sha512-L3sHRo1pXXEqX8VU28kfgUY+YGsk09hPqZiZmLacNib6XNTCM8ubYeT7ryXQw8asB1sKgcU5lkB7ONug08aB8w==}
+    dev: false
+
   /common-path-prefix@3.0.0:
     resolution: {integrity: sha512-QE33hToZseCH3jS0qN96O/bSh3kaw/h+Tq7ngyY9eWDUnTlTNUyqfqvCXioLe5Na5jFsL78ra/wuBU4iuEgd4w==}
     dev: false