diff --git a/README.md b/README.md
index 58ba78c..ae2d145 100644
--- a/README.md
+++ b/README.md
@@ -218,7 +218,8 @@ development workflow, and the Makefile targets are thin shims that call them. We
 provide:
 
 - `script/bootstrap` — install all dependencies (pinned node via nvm if needed,
-  yarn via corepack, `yarn install --frozen-lockfile`)
+  yarn via corepack, `yarn install --frozen-lockfile`), then fail, naming the
+  module, if node cannot find `jest`, `playwright-core` or `ethers`
 - `script/setup` — make a fresh clone ready for development: bootstrap plus the
   git pre-commit hook
 - `script/projectname` — print the project name (used for the Docker image tag)
diff --git a/TODO.md b/TODO.md
index 225c833..f0f7c4f 100644
--- a/TODO.md
+++ b/TODO.md
@@ -45,6 +45,15 @@ but the review is broader than any of them.
 
 # Completed Steps
 
+- 2026-10-06: `script/bootstrap` no longer reports success while node cannot
+  find a module the tests load
+  ([#263](https://git.eeqj.de/sneak/AutistMask/issues/263)). After the install
+  it asks node for `jest`, `playwright-core` and `ethers`, and fails naming the
+  missing one and the fix. yarn skips the install whenever
+  `node_modules/.yarn-integrity` matches `yarn.lock`, so a package deleted from
+  `node_modules` stayed deleted while bootstrap said it was complete. The
+  fresh-clone failure the issue reports did not reproduce.
+
 - 2026-10-06: A token symbol or name read off a contract is no longer stored cut
   between the two halves of an emoji
   ([#458](https://git.eeqj.de/sneak/AutistMask/issues/458)). `lookupTokenInfo()`
diff --git a/script/bootstrap b/script/bootstrap
index 4df1d8c..779b28e 100755
--- a/script/bootstrap
+++ b/script/bootstrap
@@ -127,6 +127,30 @@ install_js_deps() {
     fi
 }
 
+# resolvable <module>: true when node, run from the repo root, finds it
+resolvable() {
+    if missing node && [ -s "$HOME/.nvm/nvm.sh" ]; then
+        nvm_sh "nvm use $NODE_VERSION >/dev/null && cd \"$ROOT\" && \
+            node -e \"require.resolve('$1')\"" 2>/dev/null
+    else
+        node -e "require.resolve('$1')" 2>/dev/null
+    fi
+}
+
+# yarn install exits 0 without touching node_modules once
+# node_modules/.yarn-integrity matches yarn.lock, so a package deleted from
+# node_modules stays deleted. Fail unless node finds the modules the tests
+# load: jest for make test, playwright-core and ethers for tests/e2e/.
+check_js_deps() {
+    for module in jest playwright-core ethers; do
+        if ! resolvable "$module"; then
+            echo "bootstrap: node cannot find $module after yarn install" >&2
+            echo "  fix: rm -rf node_modules && make bootstrap" >&2
+            exit 1
+        fi
+    done
+}
+
 main() {
     cd "$ROOT"
 
@@ -136,6 +160,7 @@ main() {
     ensure_node
     ensure_yarn
     install_js_deps
+    check_js_deps
 
     echo "bootstrap complete"
 }