diff --git a/.github/workflows/website-checks.yml b/.github/workflows/website-checks.yml
index 9e8f7a8dcc..e11f991218 100644
--- a/.github/workflows/website-checks.yml
+++ b/.github/workflows/website-checks.yml
@@ -131,6 +131,15 @@ jobs:
       - name: ARIA references resolve
         run: npm run check:aria
 
+      # A post's body module must live at bodies/<slug>.ts: the reader resolves
+      # it by file name while the static build resolves it through posts.ts, and
+      # the two disagreed once -- two posts (buses-and-peripherals,
+      # clocks-resets-and-cdc) rendered statically but died in the reader on
+      # every opening, because their modules were named course-*.ts. The gate
+      # runs its own negative control first.
+      - name: every post opens in the reader
+        run: npm run check:blog-bodies
+
       # Not a gate on the count, a gate on the DIRECTION, and per file: a scalar
       # total passes when one file is fixed and another breaks by the same
       # amount. --selftest first, so a gate nobody has watched fail is not
diff --git a/apps/website/package.json b/apps/website/package.json
index a64e93152d..9eca2a1efa 100644
--- a/apps/website/package.json
+++ b/apps/website/package.json
@@ -34,6 +34,7 @@
     "check:render": "node scripts/render-check.mjs",
     "check:deployed": "node scripts/deployed-check.mjs",
     "check:aria": "node scripts/aria-refs-check.mjs",
+    "check:blog-bodies": "node scripts/blog-bodies-check.mjs --self-test && node scripts/blog-bodies-check.mjs",
     "check:service-entry": "node scripts/service-entry-check.mjs",
     "typecheck:update": "node scripts/typecheck-ratchet.mjs --update",
     "audit:en": "node qa/lang_audit.mjs",
diff --git a/apps/website/scripts/blog-bodies-check.mjs b/apps/website/scripts/blog-bodies-check.mjs
new file mode 100644
index 0000000000..5d743c10f4
--- /dev/null
+++ b/apps/website/scripts/blog-bodies-check.mjs
@@ -0,0 +1,82 @@
+// The invariant: a post's interactive body is looked up BY SLUG, so the body
+// module must live at src/data/blog/bodies/<slug>.ts.
+//
+// Two components resolve bodies independently, and they once disagreed. The
+// static build goes through posts.ts, whose import table happily mapped the
+// slug 'buses-and-peripherals' to a file named course-buses-and-peripherals.ts
+// -- and the site rendered fine. The reader's SPA (Blog.tsx) resolves the same
+// body through import.meta.glob keyed by FILE NAME, found no
+// buses-and-peripherals.ts, and every opening of that post ended on
+// "Интерактивная версия не смогла загрузить этот пост". The build could not
+// see it: posts.ts was consistent. This gate holds the file name to the slug
+// so the two resolutions cannot drift apart again.
+
+import { mkdtempSync, readdirSync, rmSync, writeFileSync } from 'node:fs'
+import { tmpdir } from 'node:os'
+import { join } from 'node:path'
+import { loadPublishedPosts } from './update-blog-cover-versions.mjs'
+
+const ROOT = join(new URL('.', import.meta.url).pathname, '..')
+
+/**
+ * Pure half, so the failure mode is tested instead of trusted.
+ *
+ * missing  -- published slugs with no bodies/<slug>.ts (breaks the SPA reader)
+ * orphans  -- body modules no post loads; they still ship as dead chunks
+ */
+export function checkBlogBodies({ slugs, bodiesDir }) {
+  const files = new Set(
+    readdirSync(bodiesDir)
+      .filter((f) => f.endsWith('.ts'))
+      .map((f) => f.replace(/\.ts$/, '')),
+  )
+  const missing = slugs.filter((slug) => !files.has(slug))
+  const orphans = [...files].filter((f) => !slugs.includes(f)).sort()
+  return { missing, orphans }
+}
+
+function report({ slugs, missing, orphans }) {
+  for (const slug of missing) {
+    console.error(`::error::post "${slug}" has no src/data/blog/bodies/${slug}.ts -- the reader cannot open it`)
+  }
+  if (missing.length) {
+    console.error('Rename the body module to the slug (git mv), or rename the slug: posts.ts maps imports, the reader glob does not.')
+    process.exit(1)
+  }
+  if (orphans.length) {
+    console.log(`::warning::${orphans.length} body module(s) no post loads (they still ship as chunks):`)
+    for (const f of orphans) console.log(`  ${f}`)
+  }
+  console.log(`blog bodies: every published post of ${slugs.length} opens in the reader`)
+}
+
+// A gate nobody has watched fail is not a gate: plant a slug with no file and
+// require the detector to report it before trusting the real run.
+function selfTest() {
+  const dir = mkdtempSync(join(tmpdir(), 't27-blog-bodies-'))
+  try {
+    writeFileSync(join(dir, 'a-real-post.ts'), 'export const body = []\n')
+    writeFileSync(join(dir, 'an-orphan.ts'), 'export const body = []\n')
+    writeFileSync(join(dir, 'not-a-module.md'), 'not a body module\n')
+    const { missing, orphans } = checkBlogBodies({
+      slugs: ['a-real-post', 'a-post-with-no-file'],
+      bodiesDir: dir,
+    })
+    if (missing.length !== 1 || missing[0] !== 'a-post-with-no-file') {
+      throw new Error(`self-test: expected the fileless slug to be missing, got ${JSON.stringify(missing)}`)
+    }
+    if (orphans.length !== 1 || orphans[0] !== 'an-orphan') {
+      throw new Error(`self-test: expected exactly the orphan module, got ${JSON.stringify(orphans)}`)
+    }
+    console.log('self-test: a fileless slug is reported, an orphan is listed')
+  } finally {
+    rmSync(dir, { recursive: true, force: true })
+  }
+}
+
+if (process.argv[2] === '--self-test') {
+  selfTest()
+} else {
+  const slugs = loadPublishedPosts().map((p) => p.slug)
+  report({ slugs, ...checkBlogBodies({ slugs, bodiesDir: join(ROOT, 'src/data/blog/bodies') }) })
+}
diff --git a/apps/website/src/data/blog/bodies/course-buses-and-peripherals.ts b/apps/website/src/data/blog/bodies/buses-and-peripherals.ts
similarity index 100%
rename from apps/website/src/data/blog/bodies/course-buses-and-peripherals.ts
rename to apps/website/src/data/blog/bodies/buses-and-peripherals.ts
diff --git a/apps/website/src/data/blog/bodies/course-3-clocks-resets-and-cdc.ts b/apps/website/src/data/blog/bodies/clocks-resets-and-cdc.ts
similarity index 100%
rename from apps/website/src/data/blog/bodies/course-3-clocks-resets-and-cdc.ts
rename to apps/website/src/data/blog/bodies/clocks-resets-and-cdc.ts
diff --git a/apps/website/src/data/blog/posts.ts b/apps/website/src/data/blog/posts.ts
index b88647a9c6..f0cb43ab98 100644
--- a/apps/website/src/data/blog/posts.ts
+++ b/apps/website/src/data/blog/posts.ts
@@ -107,8 +107,8 @@ import { body as body_the_control_that_could_not_fail, ruBody as ruBody_the_cont
 import { body as body_the_scanner_scored_what_it_could_not_see, ruBody as ruBody_the_scanner_scored_what_it_could_not_see } from './bodies/the-scanner-scored-what-it-could-not-see'
 
 import { body as body_i_wrote_the_post_then_did_the_thing, ruBody as ruBody_i_wrote_the_post_then_did_the_thing } from './bodies/i-wrote-the-post-then-did-the-thing'
-import { body as body_course_buses_and_peripherals, ruBody as ruBody_course_buses_and_peripherals } from './bodies/course-buses-and-peripherals'
-import { body as body_clocks_resets_and_cdc, ruBody as ruBody_clocks_resets_and_cdc } from './bodies/course-3-clocks-resets-and-cdc'
+import { body as body_course_buses_and_peripherals, ruBody as ruBody_course_buses_and_peripherals } from './bodies/buses-and-peripherals'
+import { body as body_clocks_resets_and_cdc, ruBody as ruBody_clocks_resets_and_cdc } from './bodies/clocks-resets-and-cdc'
 import { body as body_real_value_in_integer_container, ruBody as ruBody_real_value_in_integer_container } from './bodies/real-value-in-integer-container'
 import { body as body_features_that_change_no_bits, ruBody as ruBody_features_that_change_no_bits } from './bodies/features-that-change-no-bits'
 import { body as body_one_commit_nine_workflow_outcomes, ruBody as ruBody_one_commit_nine_workflow_outcomes } from './bodies/one-commit-nine-workflow-outcomes'