diff --git a/.github/workflows/verify-dist.yml b/.github/workflows/verify-dist.yml
new file mode 100644
index 0000000..0146a06
--- /dev/null
+++ b/.github/workflows/verify-dist.yml
@@ -0,0 +1,69 @@
+name: Verify dists are up to date
+description: >
+  Verify that the checked-in `dist/` of every bundled JS action is up to date with its source.
+
+on:
+  pull_request:
+    types:
+      - opened
+      - reopened
+      - synchronize
+
+concurrency:
+  group: check-dist-${{ github.workflow }}-${{ github.ref }}
+  cancel-in-progress: true
+
+permissions:
+  contents: read
+
+jobs:
+  # Discover every directory whose package.json defines a `bundle` script, so
+  # each bundled action is verified individually and new ones are picked up
+  # automatically without editing this workflow.
+  discover-actions:
+    name: Discover actions
+    runs-on: ubuntu-arm64
+    outputs:
+      dirs: ${{ steps.find.outputs.dirs }}
+    steps:
+      - name: Checkout
+        uses: actions/checkout@df4cb1c069e1874edd31b4311f1884172cec0e10 # v6.0.3
+        with:
+          persist-credentials: false
+
+      - name: Find actions with a bundle script
+        id: find
+        run: |
+          dirs=$(find . -name package.json -not -path '*/node_modules/*' -print0 \
+            | xargs -0 -I{} sh -c 'jq -e ".scripts.bundle" "{}" >/dev/null 2>&1 && dirname "{}"' \
+            | sed 's|^\./||' \
+            | jq -R -s -c 'split("\n") | map(select(length > 0))')
+          echo "Bundled actions found: $dirs"
+          echo "dirs=$dirs" >> "$GITHUB_OUTPUT"
+
+  verify-dist:
+    name: Verify dist
+    needs:
+      - discover-actions
+    if: needs.discover-actions.outputs.dirs != '[]'
+    runs-on: ubuntu-arm64
+    strategy:
+      fail-fast: false
+      matrix:
+        dir: ${{ fromJSON(needs.discover-actions.outputs.dirs) }}
+    steps:
+      - name: Checkout
+        uses: actions/checkout@df4cb1c069e1874edd31b4311f1884172cec0e10 # v6.0.3
+        with:
+          persist-credentials: false
+
+      - name: Setup Node.js
+        uses: actions/setup-node@48b55a011bda9f5d6aeb4c2d9c7362e8dae4041e # v6.4.0
+        with:
+          node-version-file: ${{ matrix.dir }}/.nvmrc
+          cache-dependency-path: ${{ matrix.dir }}/package-lock.json
+
+      - name: Verify dist is up to date
+        run: make check-drift ACTION="$ACTION_DIR"
+        env:
+          ACTION_DIR: ${{ matrix.dir }}
diff --git a/Makefile b/Makefile
new file mode 100644
index 0000000..0b0723d
--- /dev/null
+++ b/Makefile
@@ -0,0 +1,87 @@
+# Helper for building and checking the bundled dist/ of a GitHub Action
+# Run `make help` for usage instructions.
+
+# nvm requires bash; the default /bin/sh (dash on some Linux) cannot source it.
+SHELL := bash
+
+NVM_DIR ?= $(HOME)/.nvm
+
+# The action directory is passed as a variable, e.g. `make check-setup ACTION=e2e-version`.
+ACTION ?=
+
+.DEFAULT_GOAL := help
+
+.PHONY: help check-setup bundle check-drift
+
+help:
+	@echo "Usage:"
+	@echo "  make check-setup ACTION=<action>   Validate the action is set up for reproducible bundling"
+	@echo "  make bundle      ACTION=<action>   Validate, then rebuild <action>/dist"
+	@echo "  make check-drift ACTION=<action>   Rebuild and fail if <action>/dist is out of date (used in CI)"
+	@echo ""
+	@echo "Example:"
+	@echo "  make bundle ACTION=e2e-version"
+
+# Validate that the action is set up for reproducible bundling BEFORE building.
+# Each check is its own line, so make stops at the first one that fails.
+check-setup:
+	@test -n "$(ACTION)" || { echo "Error: ACTION is required, e.g. 'make check-setup ACTION=e2e-version'" >&2; exit 1; }
+	@test -d "$(ACTION)" || { echo "Error: directory '$(ACTION)' not found" >&2; exit 1; }
+	@test -f "$(ACTION)/package.json" || { echo "Error: '$(ACTION)/package.json' not found - '$(ACTION)' is not a bundled JS action" >&2; exit 1; }
+	@command -v jq >/dev/null || { echo "Error: 'jq' is required for config checks (brew install jq)" >&2; exit 1; }
+	@test -f "$(ACTION)/.nvmrc" || { echo "Error: '$(ACTION)/.nvmrc' is missing. Pin an exact Node version, e.g.: echo 24.11.0 > $(ACTION)/.nvmrc" >&2; exit 1; }
+	@test -f "$(ACTION)/package-lock.json" || { echo "Error: '$(ACTION)/package-lock.json' is missing. Run 'npm install' once in '$(ACTION)' and commit it." >&2; exit 1; }
+	@jq -e '.scripts.bundle' "$(ACTION)/package.json" >/dev/null || { echo "Error: '$(ACTION)/package.json' has no 'bundle' script (expected something like: ncc build ... -o dist)" >&2; exit 1; }
+	@unpinned=$$(jq -r '((.dependencies // {}) + ((.devDependencies // {}) | with_entries(select(.key == "@vercel/ncc")))) | to_entries[] | select(.value | test("^[0-9]+[.][0-9]+[.][0-9]+([-+].+)?$$") | not) | "\(.key)@\(.value)"' "$(ACTION)/package.json"); \
+	if [ -n "$$unpinned" ]; then \
+		echo "Error: the following dependencies must be pinned to EXACT versions (no '^' or '~')," >&2; \
+		echo "       because ncc inlines them into dist/ and a range lets the output drift:" >&2; \
+		echo "$$unpinned" | sed 's/^/  - /' >&2; \
+		echo "Fix: set exact versions in '$(ACTION)/package.json', then run 'npm install' in '$(ACTION)' to refresh the lockfile." >&2; \
+		exit 1; \
+	fi
+	@echo "OK: '$(ACTION)' is configured for reproducible bundling (.nvmrc, lockfile, bundle script, pinned deps)."
+
+# Rebuild dist/. Depends on `check-setup`, so config is validated first.
+bundle: check-setup
+	@echo ">> $(ACTION): rebuilding dist/ ..."
+	@if [ -s "$(NVM_DIR)/nvm.sh" ]; then \
+		. "$(NVM_DIR)/nvm.sh" >/dev/null && cd "$(ACTION)" && nvm install >/dev/null && npm ci && npm run bundle; \
+	else \
+		want=$$(sed 's/^v//; s/[[:space:]]//g' "$(ACTION)/.nvmrc"); \
+		have=$$(node -v 2>/dev/null | sed 's/^v//'); \
+		if [ -z "$$have" ]; then echo "Error: Node.js not found on PATH and nvm not available at '$(NVM_DIR)/nvm.sh'." >&2; exit 1; fi; \
+		case "$$have" in "$$want"*) : ;; *) echo "Error: active Node '$$have' does not match '$(ACTION)/.nvmrc' ('$$want'). Switch to the matching version (nvm / asdf / setup-node)." >&2; exit 1 ;; esac; \
+		cd "$(ACTION)" && npm ci && npm run bundle; \
+	fi
+	@echo ">> $(ACTION): dist/ regenerated. Review 'git diff -- $(ACTION)/dist' and commit it."
+
+# Rebuild and fail if the committed dist/ drifted from source. Used by CI.
+check-drift: bundle
+	@if [ -n "$$(git status --porcelain -- "$(ACTION)")" ]; then \
+		{ \
+		echo ""; \
+		echo "================================================================"; \
+		echo "'$(ACTION)/dist' is out of date with its source."; \
+		echo ""; \
+		echo "To regenerate it locally:"; \
+		echo "    make bundle ACTION=$(ACTION)"; \
+		echo "then commit the updated dist/ together with your change."; \
+		echo ""; \
+		echo "dist/ is produced by 'ncc', which inlines every dependency and minifies"; \
+		echo "the result, so it drifts unless Node, the bundler and every inlined"; \
+		echo "dependency are pinned identically everywhere."; \
+		echo ""; \
+		echo "Setting up a NEW bundled action? It must have:"; \
+		echo "  - a .nvmrc pinning an exact Node version (e.g. 24.11.0)"; \
+		echo "  - exact, caret-free versions for the inlined runtime deps and @vercel/ncc"; \
+		echo "    in package.json (e.g. \"@actions/core\": \"3.0.1\", not \"^3.0.1\")"; \
+		echo "  - a committed package-lock.json, always installed with 'npm ci'"; \
+		echo "  - a 'bundle' script in package.json that writes to dist/"; \
+		echo "'make check-setup ACTION=$(ACTION)' validates all of the above."; \
+		echo "================================================================"; \
+		} >&2; \
+		if [ -n "$$CI" ]; then echo "::error::'$(ACTION)/dist' is out of date. Run 'make bundle ACTION=$(ACTION)' and commit dist/. See the log above."; fi; \
+		exit 1; \
+	fi
+	@echo "OK: '$(ACTION)/dist' is up to date."
diff --git a/e2e-version/.nvmrc b/e2e-version/.nvmrc
new file mode 100644
index 0000000..0a49261
--- /dev/null
+++ b/e2e-version/.nvmrc
@@ -0,0 +1 @@
+24.11.0
diff --git a/e2e-version/package.json b/e2e-version/package.json
index 2f39b99..3234dfa 100644
--- a/e2e-version/package.json
+++ b/e2e-version/package.json
@@ -10,11 +10,11 @@
   "author": "",
   "license": "ISC",
   "dependencies": {
-    "@actions/core": "^3.0.1",
-    "semver": "^7.5.4"
+    "@actions/core": "3.0.1",
+    "semver": "7.7.3"
   },
   "devDependencies": {
-    "@vercel/ncc": "^0.44.0",
+    "@vercel/ncc": "0.44.0",
     "jest": "^30.0.0"
   }
 }