diff --git a/.github/workflows/changelog-check.yml b/.github/workflows/changelog-check.yml
new file mode 100644
index 000000000..b4fae54b2
--- /dev/null
+++ b/.github/workflows/changelog-check.yml
@@ -0,0 +1,88 @@
+name: Changelog Check
+
+# Exploration 0197: require every PR to either describe its user-facing change in
+# a `## Changelog` section or carry the `skip-changelog` label. Runs on body and
+# label edits so the check clears as soon as the PR is fixed. Add the job name
+# `changelog-section` to the branch ruleset to make it block merges.
+on:
+  pull_request:
+    types: [opened, edited, reopened, synchronize, labeled, unlabeled]
+    branches: [main]
+
+permissions:
+  contents: read
+  pull-requests: write
+
+concurrency:
+  group: changelog-check-${{ github.event.pull_request.number }}
+  cancel-in-progress: true
+
+jobs:
+  changelog-section:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - uses: actions/setup-node@v4
+        with:
+          node-version: '24'
+
+      - name: Require a Changelog section (or skip-changelog label)
+        id: check
+        continue-on-error: true
+        env:
+          PR_BODY: ${{ github.event.pull_request.body }}
+          PR_LABELS: ${{ join(github.event.pull_request.labels.*.name, ',') }}
+        run: node scripts/changelog/check.mjs
+
+      - name: Post / resolve the helper comment
+        if: always()
+        continue-on-error: true
+        uses: actions/github-script@v7
+        with:
+          script: |
+            const passed = '${{ steps.check.outcome }}' === 'success'
+            const marker = '<!-- changelog-check -->'
+            const { owner, repo } = context.repo
+            const issue_number = context.payload.pull_request.number
+            const comments = await github.paginate(github.rest.issues.listComments, { owner, repo, issue_number })
+            const existing = comments.find(
+              (c) => c.user?.login === 'github-actions[bot]' && c.body?.includes(marker)
+            )
+            if (passed) {
+              if (existing) {
+                await github.rest.issues.updateComment({
+                  owner, repo, comment_id: existing.id,
+                  body: `${marker}\n✓ Changelog section found — thanks!`
+                })
+              }
+              return
+            }
+            const body = [
+              marker,
+              '**This PR needs a `## Changelog` section.**',
+              '',
+              'Add one to the PR description so the change reaches the public',
+              'changelog (CI publishes it automatically on merge):',
+              '',
+              '```markdown',
+              '## Changelog',
+              '',
+              'Short, benefit-first headline',
+              'One sentence on what the user can now do.',
+              '- A specific user-visible point',
+              'tags: app, ai',
+              '```',
+              '',
+              'No user-facing change? Add the **`skip-changelog`** label instead.'
+            ].join('\n')
+            if (existing) {
+              await github.rest.issues.updateComment({ owner, repo, comment_id: existing.id, body })
+            } else {
+              await github.rest.issues.createComment({ owner, repo, issue_number, body })
+            }
+
+      - name: Enforce the result
+        if: steps.check.outcome != 'success'
+        run: |
+          echo "Changelog section missing — see the PR comment above."
+          exit 1
diff --git a/AGENTS.md b/AGENTS.md
index 4f54bddc8..aac673f21 100644
--- a/AGENTS.md
+++ b/AGENTS.md
@@ -309,11 +309,13 @@ xNet keeps a user-facing changelog (explorations 0195–0197). It surfaces on th
 website (`/changelog`), as JSON/RSS feeds, and inside the app's "What's New"
 panel.
 
-**You don't edit the changelog data by hand.** When your change ships something
-a user will notice — a new feature, a fixed bug, a visible UX or performance
-improvement — fill the **`## Changelog` section of the PR description**. On merge,
-CI (`.github/workflows/changelog.yml`) turns that block into a fragment file and
-commits it, stamping the date, PR number, and author automatically:
+**Required — every PR must do one of two things, or it cannot merge.** A
+required CI check (`changelog-section`) fails the PR unless it either has a
+`## Changelog` section **or** carries the `skip-changelog` label. Don't edit the
+changelog data by hand — fill the **`## Changelog` section of the PR
+description**. On merge, CI (`.github/workflows/changelog.yml`) turns that block
+into a fragment file and commits it, stamping the date, PR number, and author
+automatically:
 
 ```markdown
 ## Changelog
@@ -327,8 +329,9 @@ tags: app, ai
 
 Write for end users, not engineers: "Deals now sync after import," not
 `fix(schema): correct relation validation`. For internal-only PRs (refactors,
-chores, CI), leave the block empty and add the **`skip-changelog`** label — a PR
-merged without either gets a `needs-changelog` label so it isn't lost.
+chores, CI), add the **`skip-changelog`** label instead — that satisfies the
+check. (If a PR is ever admin-merged past the check without either, it gets a
+`needs-changelog` label so it isn't lost.)
 
 To hand-author or correct an entry, drop/edit a `site/src/data/changelog/<id>.json`
 fragment directly; `pnpm --filter site validate:changelog` enforces the shape.
diff --git a/scripts/changelog/check.mjs b/scripts/changelog/check.mjs
new file mode 100644
index 000000000..ef20e3741
--- /dev/null
+++ b/scripts/changelog/check.mjs
@@ -0,0 +1,44 @@
+#!/usr/bin/env node
+/**
+ * PR gate (exploration 0197): fail unless the PR body has a `## Changelog`
+ * section with real content, or the PR carries the `skip-changelog` label.
+ * Wired as a required check (changelog-section) so a PR can't merge without
+ * either. Uses the same parsing as the on-merge writer (from-pr.mjs) via lib.mjs.
+ */
+import { hasChangelogContent } from './lib.mjs'
+
+const body = process.env.PR_BODY || ''
+const labels = (process.env.PR_LABELS || '')
+  .split(',')
+  .map((l) => l.trim())
+  .filter(Boolean)
+
+if (labels.includes('skip-changelog')) {
+  console.log('✓ skip-changelog label present — changelog not required for this PR.')
+  process.exit(0)
+}
+
+if (hasChangelogContent(body)) {
+  console.log('✓ This PR has a Changelog section.')
+  process.exit(0)
+}
+
+console.error(
+  [
+    '✗ This PR is missing a "## Changelog" section.',
+    '',
+    'Add one to the PR description so the change reaches the public changelog',
+    '(CI turns it into an entry automatically on merge):',
+    '',
+    '  ## Changelog',
+    '',
+    '  Short, benefit-first headline',
+    '  One sentence on what the user can now do.',
+    '  - A specific user-visible point',
+    '  tags: app, ai',
+    '',
+    'If this PR has no user-facing impact (internal refactor, chore, CI),',
+    'add the "skip-changelog" label instead.'
+  ].join('\n')
+)
+process.exit(1)
diff --git a/scripts/changelog/from-pr.mjs b/scripts/changelog/from-pr.mjs
index 3c222aea8..266b392f6 100644
--- a/scripts/changelog/from-pr.mjs
+++ b/scripts/changelog/from-pr.mjs
@@ -12,12 +12,9 @@
  */
 import { appendFileSync, existsSync, mkdirSync, writeFileSync } from 'node:fs'
 import { join } from 'node:path'
+import { KNOWN_TAGS, cleanTags, extractChangelogBlock, parseChangelogBlock } from './lib.mjs'
 
 const DIR = 'site/src/data/changelog'
-const KNOWN_TAGS = new Set([
-  'app', 'crm', 'finance', 'tasks', 'ai', 'plugins', 'editor',
-  'sync', 'identity', 'platform', 'performance', 'devtools', 'ci'
-])
 const MODEL = process.env.CHANGELOG_MODEL || 'claude-haiku-4-5'
 
 function out(key, value) {
@@ -30,43 +27,6 @@ function monthLabel(iso) {
   return d.toLocaleString('en-US', { month: 'long', year: 'numeric', timeZone: 'UTC' })
 }
 
-/** Pull the text under a `## Changelog` heading, up to the next heading. */
-function extractBlock(body) {
-  if (!body) return ''
-  const lines = body.split(/\r?\n/)
-  const start = lines.findIndex((l) => /^#{1,4}\s*changelog\s*$/i.test(l.trim()))
-  if (start === -1) return ''
-  const rest = []
-  for (let i = start + 1; i < lines.length; i++) {
-    if (/^#{1,4}\s+\S/.test(lines[i])) break
-    rest.push(lines[i])
-  }
-  return rest.join('\n').replace(/<!--[\s\S]*?-->/g, '').trim()
-}
-
-function cleanTags(raw) {
-  const tags = (raw || []).map((t) => String(t).trim().toLowerCase()).filter((t) => KNOWN_TAGS.has(t))
-  return tags.length ? [...new Set(tags)] : ['app']
-}
-
-/** Parse the block: first line = title, `-`/`*` lines = highlights, `tags:` line = tags, rest = summary. */
-function parseProse(block, fallbackTitle) {
-  const lines = block.split(/\r?\n/).map((l) => l.trim()).filter(Boolean)
-  let title = ''
-  const summary = []
-  const highlights = []
-  let tags = []
-  for (const line of lines) {
-    const tagsMatch = line.match(/^tags?:\s*(.+)$/i)
-    if (tagsMatch) { tags = tagsMatch[1].split(','); continue }
-    if (/^[-*]\s+/.test(line)) { highlights.push(line.replace(/^[-*]\s+/, '')); continue }
-    if (!title) { title = line; continue }
-    summary.push(line)
-  }
-  title = title || fallbackTitle || ''
-  return { title, summary: summary.join(' ') || title, highlights, tags: cleanTags(tags) }
-}
-
 /** Ask Claude for a structured entry. Fail-open: returns null on any error. */
 async function aiDraft(prTitle, prBody) {
   const key = process.env.ANTHROPIC_API_KEY
@@ -115,8 +75,8 @@ async function main() {
     return out('written', 'false')
   }
 
-  const block = extractBlock(process.env.PR_BODY)
-  let parsed = block ? parseProse(block, process.env.PR_TITLE) : null
+  const block = extractChangelogBlock(process.env.PR_BODY)
+  let parsed = block ? parseChangelogBlock(block, process.env.PR_TITLE) : null
   if (!parsed || !parsed.summary) parsed = await aiDraft(process.env.PR_TITLE, process.env.PR_BODY)
   if (!parsed || !parsed.title || !parsed.summary) {
     console.log('no changelog block and no AI draft — nothing written')
diff --git a/scripts/changelog/lib.mjs b/scripts/changelog/lib.mjs
new file mode 100644
index 000000000..55edb5b12
--- /dev/null
+++ b/scripts/changelog/lib.mjs
@@ -0,0 +1,62 @@
+/**
+ * Shared changelog-from-PR parsing (exploration 0197). Used by both the writer
+ * (from-pr.mjs, on merge) and the gate (check.mjs, on every PR) so "does this PR
+ * have a changelog?" is decided by exactly the same logic that produces the entry.
+ */
+
+export const KNOWN_TAGS = new Set([
+  'app', 'crm', 'finance', 'tasks', 'ai', 'plugins', 'editor',
+  'sync', 'identity', 'platform', 'performance', 'devtools', 'ci'
+])
+
+export function cleanTags(raw) {
+  const tags = (raw || []).map((t) => String(t).trim().toLowerCase()).filter((t) => KNOWN_TAGS.has(t))
+  return tags.length ? [...new Set(tags)] : ['app']
+}
+
+/** Pull the text under a `## Changelog` heading, up to the next heading, comments stripped. */
+export function extractChangelogBlock(body) {
+  if (!body) return ''
+  const lines = body.split(/\r?\n/)
+  const start = lines.findIndex((l) => /^#{1,4}\s*changelog\s*$/i.test(l.trim()))
+  if (start === -1) return ''
+  const rest = []
+  for (let i = start + 1; i < lines.length; i++) {
+    if (/^#{1,4}\s+\S/.test(lines[i])) break
+    rest.push(lines[i])
+  }
+  return rest.join('\n').replace(/<!--[\s\S]*?-->/g, '').trim()
+}
+
+/** Parse the block: first line = title, `-`/`*` lines = highlights, `tags:` line = tags, rest = summary. */
+export function parseChangelogBlock(block, fallbackTitle) {
+  const lines = block.split(/\r?\n/).map((l) => l.trim()).filter(Boolean)
+  let title = ''
+  const summary = []
+  const highlights = []
+  let tags = []
+  for (const line of lines) {
+    const tagsMatch = line.match(/^tags?:\s*(.+)$/i)
+    if (tagsMatch) { tags = tagsMatch[1].split(','); continue }
+    if (/^[-*]\s+/.test(line)) { highlights.push(line.replace(/^[-*]\s+/, '')); continue }
+    if (!title) { title = line; continue }
+    summary.push(line)
+  }
+  title = title || fallbackTitle || ''
+  return { title, summary: summary.join(' ') || title, highlights, tags: cleanTags(tags) }
+}
+
+/**
+ * True if the PR body has a `## Changelog` section with real, user-authored
+ * content (not just the template comment or a lone `tags:` line). This is the
+ * merge gate's pass condition.
+ */
+export function hasChangelogContent(body) {
+  const block = extractChangelogBlock(body)
+  const substantive = block
+    .split(/\r?\n/)
+    .map((l) => l.trim())
+    .filter((l) => l && !/^tags?:/i.test(l))
+    .join('')
+  return substantive.length >= 8
+}