diff --git a/.github/scripts/dry-run-oidc-publish.sh b/.github/scripts/dry-run-oidc-publish.sh
new file mode 100755
index 0000000..8066cf9
--- /dev/null
+++ b/.github/scripts/dry-run-oidc-publish.sh
@@ -0,0 +1,54 @@
+#!/usr/bin/env bash
+#
+# OIDC dry-run — exercise npm publish auth without uploading to the registry.
+# For throwaway branch testing only. Do not merge to master.
+#
+# Uses a unique prerelease version so npm does not reject the dry-run when the
+# current release version (e.g. 7.4.0) already exists on the registry.
+#
+# Expects actions/setup-node to have configured the npm registry (.npmrc).
+# setup-node may set NODE_AUTH_TOKEN for OIDC — do not override it with NPM_TOKEN.
+
+set -euo pipefail
+
+BASE_VERSION=$(node -p "require('./lerna.json').version")
+DRY_RUN_VERSION="${BASE_VERSION}-oidc-dry-run.${GITHUB_RUN_NUMBER:?GITHUB_RUN_NUMBER is required}"
+
+echo "OIDC dry-run version: ${DRY_RUN_VERSION} (not committed, not published)"
+
+for dir in packages/*; do
+  node -e "
+    const fs = require('fs');
+    const path = './${dir#./}/package.json';
+    const pkg = JSON.parse(fs.readFileSync(path, 'utf8'));
+    pkg.version = '${DRY_RUN_VERSION}';
+    if (pkg.dependencies?.['@smartlyio/yavl']) {
+      pkg.dependencies['@smartlyio/yavl'] = '${DRY_RUN_VERSION}';
+    }
+    fs.writeFileSync(path, JSON.stringify(pkg, null, 2) + '\n');
+  "
+done
+
+FAILED=0
+for dir in packages/*; do
+  NAME=$(node -p "require('./$dir/package.json').name")
+  VERSION=$(node -p "require('./$dir/package.json').version")
+
+  echo "Dry-run publish ${NAME}@${VERSION} (tag: oidc-dry-run)..."
+  if npm publish "./$dir" --access public --tag oidc-dry-run --dry-run --userconfig "$GITHUB_WORKSPACE/.npmrc"; then
+    echo "Dry-run passed: ${NAME}@${VERSION}"
+  else
+    echo "::error::Dry-run failed for ${NAME}@${VERSION}"
+    FAILED=1
+  fi
+done
+
+if [ "$FAILED" -eq 1 ]; then
+  echo "::error::One or more dry-runs failed."
+  echo "If the error mentions trusted publishing, workflow filename, or 401/403/404 auth, check OIDC config on npmjs.com."
+  echo "If the error mentions an existing version, re-run the workflow (run number changes the prerelease suffix)."
+  exit 1
+fi
+
+echo ""
+echo "OIDC dry-run passed for all packages. Nothing was published to npm."
diff --git a/.github/workflows/publish.yml b/.github/workflows/publish.yml
index fc1aa97..3d353ac 100644
--- a/.github/workflows/publish.yml
+++ b/.github/workflows/publish.yml
@@ -27,6 +27,12 @@ name: Publish
 on:
   push:
     branches: [master]
+  workflow_dispatch:
+    inputs:
+      oidc_dry_run:
+        description: OIDC dry-run only (no npm upload, throwaway branch testing)
+        type: boolean
+        default: true
 
 # Prevent concurrent runs. If multiple PRs are merged in quick succession,
 # each triggered run will queue and execute in order, ensuring version bumps
@@ -35,6 +41,7 @@ concurrency: ${{ github.workflow }}-${{ github.ref }}
 
 jobs:
   publish:
+    if: github.event_name == 'push'
     runs-on: ubuntu-latest
 
     # contents:write is needed for the default GITHUB_TOKEN (used by gh CLI).
@@ -141,3 +148,35 @@ jobs:
         env:
           GITHUB_WORKSPACE: ${{ github.workspace }}
         run: ./.github/scripts/publish-packages.sh
+
+  # Throwaway branch only — do not merge to master.
+  # Reuses publish.yml so existing npm trusted publisher config applies.
+  oidc-dry-run:
+    if: github.event_name == 'workflow_dispatch' && inputs.oidc_dry_run
+    runs-on: ubuntu-latest
+    permissions:
+      contents: read
+      id-token: write
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Setup Node.js
+        uses: actions/setup-node@v6
+        with:
+          node-version: 24.x
+          registry-url: https://registry.npmjs.org
+
+      - name: Install yarn
+        run: npm install -g yarn
+
+      - name: Install dependencies
+        run: yarn install --frozen-lockfile
+
+      - name: Build
+        run: yarn build
+
+      - name: OIDC dry-run publish
+        env:
+          GITHUB_WORKSPACE: ${{ github.workspace }}
+          GITHUB_RUN_NUMBER: ${{ github.run_number }}
+        run: ./.github/scripts/dry-run-oidc-publish.sh