diff --git a/.woodpecker.yml b/.woodpecker.yml
index eca2f89..f0a0447 100644
--- a/.woodpecker.yml
+++ b/.woodpecker.yml
@@ -42,7 +42,13 @@ steps:
     commands:
       # Bundle Decap locally so the /admin page makes zero third-party requests.
       - wget -q -O static/admin/decap-cms.js https://unpkg.com/decap-cms@^3.0.0/dist/decap-cms.js
-      - hugo --minify
+      # --printPathWarnings makes Hugo report two pages resolving to one output
+      # path; --panicOnWarning turns that report into a failed build. Without
+      # both, Hugo writes both documents into the same index.html and the site
+      # ships a page that renders as the article followed by a second copy of
+      # the whole site — with nothing in the CMS, the pipeline or the logs
+      # saying a word about it. Better a red build than a corrupted page.
+      - hugo --minify --printPathWarnings --panicOnWarning
 
   deploy:
     image: alpine:3.20
diff --git a/config.yaml b/config.yaml
index e180dac..f2bf9e5 100644
--- a/config.yaml
+++ b/config.yaml
@@ -9,9 +9,14 @@ theme: "vienalatina"
 defaultContentLanguage: "es"
 defaultContentLanguageInSubdir: false
 
-# Preserve WordPress slugs so external inbound links keep working.
+# Date-scoped so two posts can share a title without fighting over one URL.
+# `:slug` falls back to the title when front matter sets none, so a bare
+# "/:slug/" mapped every post called "Hola mundo" onto /hola-mundo/; Hugo wrote
+# both documents into that one index.html and the page rendered as two stacked
+# copies of the site, with no error anywhere. Community blogs repeat titles
+# constantly ("Resumen del mes"), so the year and month carry the uniqueness.
 permalinks:
-  post: "/:slug/"
+  post: "/:year/:month/:slug/"
 
 taxonomies:
   category: "categories"
diff --git a/scripts/translate.py b/scripts/translate.py
index 76d7a24..724fbb5 100644
--- a/scripts/translate.py
+++ b/scripts/translate.py
@@ -78,6 +78,14 @@ def split_lang(path: Path) -> tuple[str, str] | None:
     return None
 
 
+# Decap resolves a filename clash by appending a counter, turning
+# `hola-mundo.es.md` into `hola-mundo.es-1.md`. That name no longer ends in a
+# language, so Hugo stops pairing it with its siblings and split_lang() returns
+# None: the post publishes in Spanish and is never translated, with nothing
+# anywhere reporting it. Recognising the shape lets us fail loudly instead.
+CLASH_SUFFIX = re.compile(r"\.(?:%s)-\d+$" % "|".join(re.escape(l) for l in SITE_LANGS))
+
+
 def split_frontmatter(text: str) -> tuple[dict, str]:
     match = re.match(r"\A---\n(.*?)\n---\n?(.*)\Z", text, re.DOTALL)
     if not match:
@@ -130,6 +138,14 @@ def authored_sources(paths: list[Path]) -> list[tuple[Path, str, str]]:
     for path in paths:
         parsed = split_lang(path)
         if not parsed:
+            rel = path.relative_to(REPO_ROOT)
+            if CLASH_SUFFIX.search(path.name[: -len(".md")] if path.suffix == ".md" else ""):
+                raise SystemExit(
+                    f"{rel}: filename ends in a clash counter, so it is neither a "
+                    f"translation source nor a sibling — it would publish untranslated.\n"
+                    f"Rename it to <something-unique>.<lang>.md (the CMS produced this "
+                    f"because another post already claimed the name)."
+                )
             continue
         basename, lang = parsed
         fm = read_frontmatter(path)
diff --git a/static/admin/config.yml b/static/admin/config.yml
index 95d0215..58c970c 100644
--- a/static/admin/config.yml
+++ b/static/admin/config.yml
@@ -22,7 +22,12 @@ collections:
     create: true
     extension: md
     format: yaml-frontmatter
-    slug: "{{slug}}.es"
+    # Date-prefixed so a repeated title does not collide on the filename. When
+    # it does collide, Decap appends "-1" and writes `hola-mundo.es-1.md` — a
+    # name whose suffix is no longer `.es`, so Hugo stops seeing a Spanish
+    # sibling and translate.py's split_lang() skips the file entirely: the post
+    # publishes but is never translated, with nothing reported anywhere.
+    slug: "{{year}}-{{month}}-{{day}}-{{slug}}.es"
     filter: { field: lang, value: es }
     fields:
       - { name: title, label: "Título", widget: string }