diff --git a/.github/workflows/generate-index.yml b/.github/workflows/generate-index.yml
index 2f2d24a..167566f 100644
--- a/.github/workflows/generate-index.yml
+++ b/.github/workflows/generate-index.yml
@@ -1,6 +1,10 @@
 name: Generate Protocol Index
 
 on:
+  # Tracking the generator at @main means the next run uses it — but a generator change upstream
+  # raises no event here, so nothing regenerates until a local change does. Run this by hand after a
+  # generator change that alters the output.
+  workflow_dispatch:
   push:
     branches: [main]
     # The index is a function of the protocols *and* of the generator version pinned below, so a
@@ -9,16 +13,72 @@ on:
       - 'protocols/**'
       - '.github/workflows/generate-index.yml'
 
+# The push uses the App installation token, not GITHUB_TOKEN, so GITHUB_TOKEN needs no write
+# access. Granting it would hand every step a second write-capable credential for nothing.
 permissions:
-  contents: write
+  contents: read
+
+# Two merges in quick succession would otherwise run concurrently, and the second push would be
+# rejected as non-fast-forward: its checkout predates the first run's index commit. Queue instead of
+# cancelling — a cancelled run leaves the index describing the previous commit.
+concurrency:
+  group: generate-index
+  cancel-in-progress: false
 
 jobs:
   generate-index:
     runs-on: ubuntu-latest
+    # The App credentials live in this environment, whose deployment branch policy allows only
+    # `main`. A pull request from a branch in this repository could otherwise read them — same-repo
+    # PRs do receive secrets — and they mint a token that bypasses branch protection.
+    environment: index-generation
     steps:
+      # The require-pr-review ruleset blocks github-actions[bot], and GitHub Actions itself cannot be
+      # granted a bypass: bypass actors of type Integration must be GitHub Apps installed on the
+      # organisation, and Actions is not one. A purpose-built App is — this one holds `contents:
+      # write` and nothing else, and its token expires after an hour.
+      - uses: actions/create-github-app-token@v1
+        id: app-token
+        with:
+          app-id: ${{ secrets.INDEX_APP_ID }}
+          private-key: ${{ secrets.INDEX_APP_PRIVATE_KEY }}
+          # Request the scope explicitly rather than inheriting whatever the installation holds, so
+          # granting the App another permission later cannot silently widen this token.
+          permission-contents: write
+
       - uses: actions/checkout@v4
-      # @v0 is a moving tag, so this repository tracks the standard without a PR per release —
-      # which is the point: an index generated by a stale generator is an index that disagrees with
-      # the standard it claims to follow. Pin @v0.3.0 or a commit SHA instead if you need the action
-      # to be immutable, and accept updating it by hand.
-      - uses: waldronlab/agent-protocol-standard/actions/generate-index@v0
+        with:
+          token: ${{ steps.app-token.outputs.token }}
+          # The branch tip, not the event SHA. Serialising runs is not enough on its own: a queued
+          # run would still check out the commit that triggered it and push a non-fast-forward once
+          # `main` had moved. It also means the index describes `main` as it is, not as it was.
+          ref: main
+      # The email prefix below is the bot's user id, which is NOT the App registration id held in
+      # INDEX_APP_ID. Getting it wrong still pushes, but GitHub does not link the commit to the bot.
+      - name: Resolve the App's bot user id
+        id: bot
+        env:
+          GH_TOKEN: ${{ github.token }}
+          SLUG: ${{ steps.app-token.outputs.app-slug }}
+        run: |
+          # Assigned separately, not interpolated into echo: `echo "id=$(gh api ...)"` exits 0 even
+          # when the lookup fails, writing an empty id, and attribution is then silently wrong.
+          set -euo pipefail
+          id="$(gh api "/users/${SLUG}[bot]" --jq .id)"
+          [ -n "$id" ] || { echo "::error::could not resolve the bot user id for ${SLUG}[bot]"; exit 1; }
+          echo "id=$id" >> "$GITHUB_OUTPUT"
+
+      # @main, not a release tag. @v0 resolved to a commit from before the Python rewrite, so this
+      # workflow was silently running the old R generator while CI stayed green. A generator that
+      # has fallen behind produces an index that disagrees with the standard it claims to follow.
+      - uses: waldronlab/agent-protocol-standard/actions/generate-index@main
+        with:
+          # The checkout above is pinned to `main`, so the generator must build `protocol_url`
+          # values from `main` too, or a workflow_dispatch from another branch would index main's
+          # content under that ref's URLs. Passed as an input because GITHUB_REF_NAME is
+          # runner-provided and a workflow cannot reliably override it.
+          ref: main
+          # Attribute the commit to the App that pushes it, rather than to github-actions[bot],
+          # which no longer has anything to do with this push.
+          committer-name: ${{ steps.app-token.outputs.app-slug }}[bot]
+          committer-email: ${{ steps.bot.outputs.id }}+${{ steps.app-token.outputs.app-slug }}[bot]@users.noreply.github.com
diff --git a/.github/workflows/validate.yml b/.github/workflows/validate.yml
index 34acf45..b6572e6 100644
--- a/.github/workflows/validate.yml
+++ b/.github/workflows/validate.yml
@@ -10,4 +10,6 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v4
-      - uses: waldronlab/agent-protocol-standard/actions/validate-protocols@v0
+      # @main, not a release tag. @v0 predated the Python rewrite, so every pull request here was
+      # being checked by the old R validator — the Pydantic rules were enforcing nothing, silently.
+      - uses: waldronlab/agent-protocol-standard/actions/validate-protocols@main
diff --git a/CONTRIBUTING.md b/CONTRIBUTING.md
index 862792a..629f897 100644
--- a/CONTRIBUTING.md
+++ b/CONTRIBUTING.md
@@ -23,7 +23,7 @@ End the file with a `## History & Reviews` section as demonstrated in the templa
 ## Step 4: Validate and Submit
 Open a pull request. **You can rely on CI for validation.** The repository's automated testing infrastructure will check your syntax and tell you precisely what is wrong. Focus on getting the scientific correctness right.
 
-*(To run the validator locally before pushing, clone `waldronlab/agent-protocol-standard` beside this repository and, from here, run `Rscript ../agent-protocol-standard/scripts/validate-protocol.R protocols`. It takes the protocols directory, not a single file, and validates every protocol in it.)*
+*(To run the validator locally before pushing, clone `waldronlab/agent-protocol-standard` beside this repository, install its dependencies with `pip install 'pydantic>=2.0.0' pyyaml`, and from here run `python3 ../agent-protocol-standard/scripts/validate_protocol.py protocols`. It takes the protocols directory, not a single file, and validates every protocol in it.)*
 
 ---