diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 70c0357..ede8849 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -103,6 +103,25 @@ jobs:
       - name: Test
         run: npm test
 
+      # Boundary-oracle mutation ratchet: a totality oracle only protects the system
+      # if it actually CATCHES a break at its chokepoint. This breaks each boundary's
+      # chokepoint with a compile-safe mutation and requires its oracle to fail
+      # (ANCHORED); an oracle that stays green under a broken floor (VACUOUS) — the
+      # rot that let the trust-split oracle pass a literal inversion before #14
+      # hardened it — fails the gate. PR runs only edges whose chokepoint/oracle
+      # changed (incremental); push to main runs the full backstop. (Full-mode in CI
+      # verified on this branch's diagnostic run.) python3 is preinstalled on
+      # ubuntu-latest; the harness reverts every mutation via git.
+      - name: Boundary oracle mutation ratchet
+        if: github.event_name == 'pull_request' || github.ref == 'refs/heads/main'
+        run: |
+          if [ "${{ github.event_name }}" = "pull_request" ]; then
+            git fetch --no-tags --depth=1 origin "${{ github.event.pull_request.base.ref }}"
+            python3 scripts/invariant-mutation-probe.py --changed FETCH_HEAD
+          else
+            python3 scripts/invariant-mutation-probe.py
+          fi
+
       # Ratchets: no new conventions, no new raw SQL interpolation sites, and the
       # trust atlas stays in sync with the boundary claims (no managed chokepoint
       # left off the atlas, no dangling edge).
diff --git a/mnemion-js/scripts/invariant-mutation-probe.py b/mnemion-js/scripts/invariant-mutation-probe.py
index fde4821..6e86c11 100755
--- a/mnemion-js/scripts/invariant-mutation-probe.py
+++ b/mnemion-js/scripts/invariant-mutation-probe.py
@@ -121,7 +121,7 @@ def restore():
     for f in {e[0] for e in RUN}:
         sh(["git","checkout","--",f])
 
-results=[]; notes=[]
+results=[]; notes=[]; diaglogs=[]
 try:
     print(f"{'BOUNDARY (oracle)':<48} VERDICT")
     print(f"{'-'*48} -------")
@@ -131,26 +131,44 @@ def restore():
         if match not in src:
             print(f"{label:<48} SKIP (match drifted)"); results.append((label,"SKIP")); continue
         open(path,"w").write(src.replace(match,repl,1))
-        r=sh(["npx","vitest","run",oracle])
+        # NO_COLOR: keep vitest output plain. CI forces ANSI, which interleaves
+        # escape codes INTO the summary ("Tests \x1b[..m1 failed") and broke the
+        # ANCHORED match on the first CI run — the tests DID catch the mutation, the
+        # harness just couldn't read its own output. Belt: strip ANSI before matching.
+        r=sh(["npx","vitest","run",oracle], env={**os.environ,"NO_COLOR":"1","FORCE_COLOR":"0"})
         sh(["git","checkout","--",f])           # revert immediately
-        log=r.stdout+r.stderr
+        log=re.sub(r"\x1b\[[0-9;]*m","",r.stdout+r.stderr)
+        # ANCHORED = the oracle RAN and an assertion FAILED (any of vitest's failure
+        # markers), as opposed to erroring before running (INVALID).
+        ran_and_failed = (re.search(r"Tests\s+\d+\s+failed", log)
+                          or re.search(r"Failed Tests\s+\d+", log)
+                          or re.search(r"\bFAIL\b.*\.test\.", log))
         if r.returncode==0:
             if shadow:
                 v="SHADOWED"; mark="o SHADOWED (expected — chokepoint not operative in test runtime)"
             else:
                 v="VACUOUS"; mark="x VACUOUS  (oracle missed the break — CONFIRM not shadowed)"
-        elif re.search(r"Tests\s+\d+\s+failed", log):
+        elif ran_and_failed:
             v="ANCHORED"; mark="+ ANCHORED"
         else:
             v="INVALID"; mark="~ INVALID  (no compile / inconclusive)"
         print(f"{label:<48} {mark}"); results.append((label,v))
         if v=="SHADOWED" and shadow: notes.append((label,shadow))
+        # Diagnosability: dump the captured oracle output for any verdict that means
+        # "the harness could not confirm this oracle is semantic" — without it an
+        # INVALID/VACUOUS in CI is a black box (the lesson from the first re-land).
+        if v in ("VACUOUS","INVALID"):
+            tail="\n".join((log or "<no output captured>").splitlines()[-40:])
+            diaglogs.append((label,v,tail))
 finally:
     restore()
 
 for label,note in notes:
     print(f"\n  note [{label}]:\n    {note}")
 
+for label,v,tail in diaglogs:
+    print(f"\n----- captured oracle output [{label}] ({v}) — last 40 lines -----\n{tail}")
+
 a=sum(1 for _,v in results if v=="ANCHORED"); vc=sum(1 for _,v in results if v=="VACUOUS")
 iv=sum(1 for _,v in results if v=="INVALID"); sh_=sum(1 for _,v in results if v=="SHADOWED")
 sk=sum(1 for _,v in results if v=="SKIP")