diff --git a/internal/check-studio-rail.mjs b/internal/check-studio-rail.mjs
index d3637a4c3..d87aa0c37 100644
--- a/internal/check-studio-rail.mjs
+++ b/internal/check-studio-rail.mjs
@@ -25,8 +25,17 @@ import { TREE_NAME } from './_tree-name.mjs'
 function undeclaredLabels(manifest) {
   const out = []
   for (const b of manifest.bundles || []) {
-    if (b.stage !== 'production') continue
     for (const p of b.profiles || []) {
+      // ⚠ PROFILE STAGE, NOT BUNDLE STAGE — the same trap, a third time. A BUNDLE reads
+      // `stage: production` when ANY ONE of its profiles is production, so scoping the loop by
+      // b.stage drags every experimental sibling in with it. Measured: cities-internet is a
+      // production bundle whose connectivity-list and data-tables are EXPERIMENTAL, and
+      // gospel-resources likewise for charts / data-tables / resources-list. That was 5 false
+      // violations out of 7 (regions-plugin caught it, 2026-09-28).
+      // I had already moved off stageOf (bundle-keyed) once; moving to b.stage was the SAME
+      // mistake wearing a different field name. The profile's own stage is the only one that
+      // answers "is this row production".
+      if (p.stage !== 'production') continue
       const declared = p.label
       if (declared === null || declared === undefined || !String(declared).trim()) {
         out.push(`${b.bundle}/${p.profile} is PRODUCTION but declares no "label" in its <profile>.meta.json — the rail falls back to a humanized id, which names nothing`)
@@ -42,11 +51,20 @@ function undeclaredLabels(manifest) {
 // fails everything is as useless as one that fails nothing.
 if (process.argv.includes('--self-test')) {
   const fixture = { bundles: [
-    { bundle: 'planted-prod', stage: 'production',   profiles: [{ profile: 'nameless', label: null }] },
-    { bundle: 'planted-exp',  stage: 'experimental', profiles: [{ profile: 'nameless', label: null }] },
-    { bundle: 'planted-ok',   stage: 'production',   profiles: [{ profile: 'named', label: 'A Real Name' }] },
+    { bundle: 'planted-prod', stage: 'production',   profiles: [{ profile: 'nameless', stage: 'production', label: null }] },
+    { bundle: 'planted-exp',  stage: 'experimental', profiles: [{ profile: 'nameless', stage: 'experimental', label: null }] },
+    { bundle: 'planted-ok',   stage: 'production',   profiles: [{ profile: 'named', stage: 'production', label: 'A Real Name' }] },
     // An EMPTY STRING is nameless too — `label: ""` would satisfy a null check and render blank.
-    { bundle: 'planted-blank', stage: 'production',  profiles: [{ profile: 'blank', label: '   ' }] },
+    { bundle: 'planted-blank', stage: 'production',  profiles: [{ profile: 'blank', stage: 'production', label: '   ' }] },
+    // ★ THE CASE THE FIRST SELF-TEST MISSED, and the bug it would have caught. A BUNDLE reads
+    // production when ANY profile is, so a mixed bundle must flag ONLY its production profile.
+    // The earlier fixture gave every bundle one profile, so bundle-stage and profile-stage agreed
+    // and scoping by the wrong one was invisible. A fixture where the two CANNOT disagree cannot
+    // test which one you read.
+    { bundle: 'planted-mixed', stage: 'production', profiles: [
+      { profile: 'prod-nameless', stage: 'production',   label: null },
+      { profile: 'exp-nameless',  stage: 'experimental', label: null },
+    ] },
   ] }
   const hits = undeclaredLabels(fixture)
   const cases = [
@@ -54,6 +72,8 @@ if (process.argv.includes('--self-test')) {
     ['experimental + no label PASSES',    !hits.some((h) => h.startsWith('planted-exp/'))],
     ['production + a real label PASSES',  !hits.some((h) => h.startsWith('planted-ok/'))],
     ['production + whitespace-only FAILS', hits.some((h) => h.startsWith('planted-blank/'))],
+    ['mixed bundle: its PRODUCTION profile FAILS',      hits.some((h) => h.startsWith('planted-mixed/prod-nameless'))],
+    ['mixed bundle: its EXPERIMENTAL profile PASSES',  !hits.some((h) => h.startsWith('planted-mixed/exp-nameless'))],
   ]
   let ok = 0
   for (const [name, pass] of cases) { console.log(`  ${pass ? '✓' : '✗'} ${name}`); if (pass) ok++ }