diff --git a/.gitattributes b/.gitattributes
index ca7d31a..fa67ffa 100644
--- a/.gitattributes
+++ b/.gitattributes
@@ -5,3 +5,8 @@
 *.docx binary
 *.png  binary
 *.md   text eol=lf
+
+# The hook runs in a POSIX shell and the workflow on a Linux runner. CRLF
+# would leave the hook with a bad interpreter line and unrunnable there.
+.githooks/* text eol=lf
+*.yml       text eol=lf
diff --git a/.githooks/pre-push b/.githooks/pre-push
new file mode 100755
index 0000000..d9f92ff
--- /dev/null
+++ b/.githooks/pre-push
@@ -0,0 +1,37 @@
+#!/bin/sh
+#
+# Run the JFA conformance suite before anything reaches the remote.
+#
+# Install once, in your clone:
+#
+#     git config core.hooksPath .githooks
+#
+# This is a convenience, not a gate. Hooks live outside the repository's
+# history unless you run that command, and `git push --no-verify` skips them.
+# The gate is the Conformance check on the pull request.
+
+set -u
+
+for py in python3 python py; do
+    if command -v "$py" >/dev/null 2>&1; then
+        PY="$py"
+        break
+    fi
+done
+
+if [ -z "${PY:-}" ]; then
+    echo "pre-push: no python interpreter found; skipping conformance suite" >&2
+    exit 0
+fi
+
+if ! "$PY" jfa-conformance-suite.py; then
+    echo "" >&2
+    echo "Push blocked: the conformance suite failed." >&2
+    echo "" >&2
+    echo "The document has drifted from the invariant registry. Fix it, or run" >&2
+    echo "  git push --no-verify" >&2
+    echo "to push anyway — the pull request will fail the same check." >&2
+    exit 1
+fi
+
+exit 0
diff --git a/.github/workflows/conformance.yml b/.github/workflows/conformance.yml
new file mode 100644
index 0000000..11a19df
--- /dev/null
+++ b/.github/workflows/conformance.yml
@@ -0,0 +1,27 @@
+name: Conformance
+
+# No paths filter, deliberately. This check is a required status check on main,
+# and a required check that never runs leaves a pull request blocked forever.
+# The suite takes well under a second, so running it on every pull request
+# costs nothing and always reports.
+on:
+  pull_request:
+  push:
+    branches: [main]
+
+permissions:
+  contents: read
+
+jobs:
+  conformance:
+    name: conformance
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+
+      - uses: actions/setup-python@v5
+        with:
+          python-version: '3.x'
+
+      - name: Run the JFA conformance suite
+        run: python jfa-conformance-suite.py
diff --git a/CONTRIBUTING.md b/CONTRIBUTING.md
new file mode 100644
index 0000000..6e37016
--- /dev/null
+++ b/CONTRIBUTING.md
@@ -0,0 +1,80 @@
+# Contributing
+
+This repository carries the official JFA document, its translations, and the
+conformance suite that binds the prose to the invariant registry. Two rules
+govern every change: **sign your commits off**, and **keep the suite green**.
+
+## Amendments go into the document
+
+Propose a change by editing the document and opening a pull request. The diff
+is the proposal, and the board approves or rejects it in review. Do not add
+proposal files or version-documentation alongside the standard — git history is
+the version record, and a parallel proposal document starts drifting from the
+text it describes the moment it is merged.
+
+Text that is settled goes into the document. Anything still unsettled goes into
+[OPEN-QUESTIONS.md](OPEN-QUESTIONS.md) as a numbered entry carrying a
+`**Status:**` line and an `**Inherits:**` line, in the style of the entries
+already there. Update the count in that file's opening paragraph when you add
+one. This split is not cosmetic: merging a document edit makes the text
+normative, so a question that is still open cannot ride in on it.
+
+## Sign-off (DCO)
+
+Every commit needs a `Signed-off-by` trailer. The DCO check requires the name
+and email in that trailer to match the commit author exactly, so let git add it
+rather than typing it by hand:
+
+```
+git commit -s
+```
+
+If the check fails on an existing branch, add the trailer to every commit and
+force-push:
+
+```
+git rebase HEAD~<n> --signoff
+git push --force-with-lease
+```
+
+## The conformance suite
+
+```
+python jfa-conformance-suite.py                 # check the document
+python jfa-conformance-suite.py --list          # print the invariant registry
+```
+
+Exit code 0 when every executed check passes, 1 otherwise. It runs on every
+pull request as the **Conformance** check and takes well under a second.
+
+To catch failures before you push, install the hook once in your clone:
+
+```
+git config core.hooksPath .githooks
+```
+
+That is a convenience, not a gate — hooks are not distributed with the
+repository, and `git push --no-verify` skips them. The pull request check is
+what actually holds.
+
+### What the suite constrains
+
+Edits to the document fail the suite if they:
+
+- drop or reorder the nine `##` sections. Additional `##` sections are fine.
+- add a `###` heading inside one of the five layer sections. Each must carry
+  exactly Protocol Tier, Orchestrator Tier and Frontend Tier, in that order.
+  Put new prose in the body of an existing tier.
+- leave *The Lines That Cannot Be Crossed* with any count but twelve.
+- remove or reword a registered anchor phrase. Twenty-five invariants are
+  anchored to the sections that carry them; run `--list` to see them, and
+  prefer appending to rewriting.
+- name a product. The document is product-agnostic.
+- introduce an email address other than the organizational footer's.
+
+## Translations
+
+The English document is authoritative; translations are for reach, not
+interpretation. The suite checks the English document only. If you amend it,
+say in the pull request whether the translations should be updated before the
+change is adopted or after.