fix(i18n): render case files in one language per locale

Case bodies hold EN and PT-BR scenes interleaved (## I. EN, ## I. PT, ...),
but the reader rendered the whole body, so an EN visitor saw every scene
twice — once in English, once in Portuguese — and vice-versa.

Add pickLocaleBody(): split by section-number occurrence (first = EN, second
= PT-BR, the narrator's mandated order), with language sniffing only as a
fallback for unpaired/unnumbered sections, and full-body fallback when a body
can't be split (English-only legacy files). Wire it into the case reader
(body, lead, OG description) and the homepage card openings.

Also fix extractBody: it discarded the English H1 by treating the second
(PT-BR) H1 as "the first real heading". Future narrations keep both titles.

Verified live: d44 and doc-65 render EN-only under locale=en and PT-only
under locale=pt-br. Bulk-checked 89 files: 80 clean, 8 structurally clean
(source-language verbatim quotes retained per spec), 1 English-only legacy.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

investigator-runtime/src/detectives/case_writer.ts

@@ -266,13 +266,18 @@ function buildPrompt(
 function extractBody(text: string): string | null {
   const t = text.trim();
   if (/^`?INSUFFICIENT_ARTEFACTS`?\b/i.test(t)) return null;
-  const stripped = t.replace(/^```(?:markdown|md)?\s*\n?/i, "").replace(/\n?```\s*$/i, "");
-  // Find first H1 — anything before is preamble we drop.
+  const stripped = t
+    .replace(/^```(?:markdown|md)?\s*\n?/i, "")
+    .replace(/\n?```\s*$/i, "")
+    .trimStart();
+  // If the text already opens on the title there is no preamble to drop.
+  // Crucial: the narrator emits TWO H1s (EN title then PT-BR title) — both are
+  // the title. Searching for the "first \n# " would mistake the PT-BR H1 for
+  // the real start and silently discard the English title.
+  if (stripped.startsWith("# ")) return stripped;
+  // Otherwise drop any preamble before the first H1.
   const h1 = stripped.indexOf("\n# ");
-  if (h1 === -1) {
-    if (stripped.startsWith("# ")) return stripped;
-    throw new Error(`case-writer returned no H1: ${t.slice(0, 200)}`);
-  }
+  if (h1 === -1) throw new Error(`case-writer returned no H1: ${t.slice(0, 200)}`);
   return stripped.slice(h1 + 1);
 }
 

web/app/c/[slug]/page.tsx

@@ -13,6 +13,7 @@ import { MarkdownBody } from "@/components/markdown-body";
 import { AuthBar } from "@/components/auth-bar";
 import { BureauNav } from "@/components/bureau-nav";
 import { getLocale } from "@/components/locale-toggle";
+import { pickLocaleBody } from "@/lib/bilingual";
 
 export const runtime = "nodejs";
 export const dynamic = "force-dynamic";
@@ -89,7 +90,8 @@ export async function generateMetadata(
   const title = locale === "pt-br"
     ? (h1s[1] ?? h1s[0] ?? c.fm.topic_pt_br ?? c.fm.topic ?? slug)
     : (h1s[0] ?? c.fm.topic ?? slug);
-  const desc = pickLead(c.body, locale).slice(0, 200);
+  const localeBody = pickLocaleBody(c.body.replace(/^#\s+.+$\n?/gm, ""), locale);
+  const desc = pickLead(localeBody, locale).slice(0, 200);
   const canonical = `${SITE_URL}/c/${slug}`;
   // OG image — use the case's editorial illustration when present. WhatsApp,
   // Twitter, Slack, Telegram, ChatGPT search all pull this as the link card.
@@ -138,7 +140,10 @@ export default async function CaseReportPage({
   const bodyTitle = locale === "pt-br" ? (h1s[1] ?? h1s[0]) : h1s[0];
   // Strip H1 lines ("# Title") — the "## section" headers survive since the
   // regex requires whitespace after a single #. Avoids duplicating the title.
-  const body = c.body.replace(/^#\s+.+$\n?/gm, "").replace(/^\s+/, "");
+  const fullBody = c.body.replace(/^#\s+.+$\n?/gm, "").replace(/^\s+/, "");
+  // Keep only the active language's scenes — the file holds EN and PT-BR
+  // sections interleaved; showing both was the language-mixing bug.
+  const body = pickLocaleBody(fullBody, locale);
   const title = bodyTitle ?? (locale === "pt-br" ? (fm.topic_pt_br ?? fm.topic ?? slug) : (fm.topic ?? slug));
   const dateLabel = fm.created_at ? new Date(fm.created_at).toLocaleDateString(locale === "pt-br" ? "pt-BR" : "en-US", { day: "numeric", month: "long", year: "numeric" }) : null;
   const canonical = `${SITE_URL}/c/${slug}`;

web/components/case-library.tsx

@@ -13,6 +13,7 @@
 import Link from "next/link";
 import { readdir, readFile, stat } from "node:fs/promises";
 import path from "node:path";
+import { pickLocaleBody } from "@/lib/bilingual";
 
 interface CaseFile {
   slug: string;
@@ -102,7 +103,7 @@ async function loadCases(locale: "pt-br" | "en"): Promise<CaseFile[]> {
         slug: f.replace(/\.md$/, ""),
         topic: enTitle,
         topic_pt_br: ptTitle,
-        opening: pickOpening(body, locale),
+        opening: pickOpening(pickLocaleBody(body, locale), locale),
         mtimeMs: st.mtimeMs,
       });
     } catch { /* skip broken file */ }

web/components/featured-case.tsx

@@ -8,6 +8,7 @@
 import Link from "next/link";
 import { readdir, readFile, stat } from "node:fs/promises";
 import path from "node:path";
+import { pickLocaleBody } from "@/lib/bilingual";
 
 interface FeaturedCaseData {
   slug: string;
@@ -86,7 +87,7 @@ async function loadFeatured(locale: "pt-br" | "en"): Promise<FeaturedCaseData |
         slug,
         topic: h1s[0] ?? fm.topic ?? f,
         topic_pt_br: h1s[1] ?? h1s[0] ?? fm.topic_pt_br ?? null,
-        opening: pickOpening(body, locale),
+        opening: pickOpening(pickLocaleBody(body, locale), locale),
         hero_doc_id: docRef?.doc_id ?? null,
         hero_page: docRef?.page ?? null,
         hero_illustration: await illustrationFor(slug),

web/lib/bilingual.ts

@@ -0,0 +1,91 @@
+/**
+ * bilingual.ts — split a narrated case-file body into a single language.
+ *
+ * The case-writer emits each scene twice: an English `## N. <title>` section
+ * followed by its Brazilian-Portuguese twin `## N. <título>` (CLAUDE.md §3).
+ * The reader, however, must see ONE language at a time — otherwise an EN
+ * visitor reads the EN scene immediately followed by the same scene in PT,
+ * and vice-versa.
+ *
+ * We classify each `## ` section by language (PT-BR carries diacritics and
+ * Portuguese function words; the English scene text does not) and keep only
+ * the sections matching the active locale. This is more robust than relying
+ * on EN-then-PT ordering: it survives a missing twin or an out-of-order
+ * section. If a body can't be split (no `## ` sections, or none match the
+ * locale), we return it unchanged — better to show everything than to hide
+ * content.
+ */
+
+const PT_DIACRITICS = /[áàâãéêíóôõúüç]/gi;
+const PT_WORDS =
+  /\b(não|que|com|para|sobre|uma|um|também|após|às|aos|nos|nas|pelo|pela|seu|sua|foi|era|está|são|sem|entre|quando|onde|índice|registro|relatório|noite|céu)\b/gi;
+const EN_WORDS =
+  /\b(the|and|with|what|which|after|over|about|into|from|that|this|their|was|were|been|when|where|night|sky|report|record)\b/gi;
+
+/**
+ * Heuristic: does this markdown block read as Brazilian Portuguese?
+ * Diacritics are the strongest signal — English narration here has none,
+ * while PT-BR is accent-rich. Function-word counts break ties.
+ */
+export function isPortuguese(block: string): boolean {
+  const diacritics = (block.match(PT_DIACRITICS) || []).length;
+  const pt = (block.match(PT_WORDS) || []).length;
+  const en = (block.match(EN_WORDS) || []).length;
+  // Diacritics weigh heavily: a few accents reliably mark PT-BR even when an
+  // English place name (e.g. "Áden") sneaks one into an EN block.
+  return diacritics * 2 + pt > en;
+}
+
+/** Section number token ("I", "IV", "3") from an H2 like "## IV. Cables". */
+function sectionKey(section: string): string | null {
+  const m = section.match(/^##\s+([ivxlcdm\d]+)[.)]/i);
+  return m ? m[1].toUpperCase() : null;
+}
+
+/**
+ * Return only the portion of a bilingual case body that matches `locale`.
+ * Operates on a body whose H1 title lines have already been stripped.
+ *
+ * Primary signal is structural, not linguistic: the narrator emits each
+ * numbered scene as an English `## N.` section immediately followed by its
+ * Brazilian-Portuguese twin `## N.`. So for a section number seen twice, the
+ * first occurrence is English and the second is Portuguese — a far more
+ * reliable split than language sniffing (an English scene quoting accented
+ * names would otherwise be misread as Portuguese). Language detection is the
+ * fallback only for unpaired or unnumbered sections.
+ */
+export function pickLocaleBody(body: string, locale: "en" | "pt-br"): string {
+  const parts = body.split(/(?=^##\s)/m);
+  // Content before the first H2 (rare intro/orphan) is shown in both languages.
+  const head = parts.length > 0 && !/^##\s/.test(parts[0]) ? parts[0].trimEnd() : "";
+  const sections = parts.filter((p) => /^##\s/.test(p));
+  if (sections.length === 0) return body;
+
+  const counts = new Map<string, number>();
+  for (const s of sections) {
+    const k = sectionKey(s);
+    if (k) counts.set(k, (counts.get(k) ?? 0) + 1);
+  }
+
+  const wantPt = locale === "pt-br";
+  const seen = new Map<string, number>();
+  const picked: string[] = [];
+  for (const s of sections) {
+    const k = sectionKey(s);
+    let isPt: boolean;
+    if (k && (counts.get(k) ?? 0) >= 2) {
+      const order = seen.get(k) ?? 0;
+      seen.set(k, order + 1);
+      isPt = order >= 1; // first = EN, second = PT-BR
+    } else {
+      isPt = isPortuguese(s); // unpaired / unnumbered — sniff the language
+    }
+    if (isPt === wantPt) picked.push(s.trimEnd());
+  }
+  // Can't isolate the requested language — fall back to the full body so no
+  // content silently disappears.
+  if (picked.length === 0) return body;
+
+  const out = picked.join("\n\n");
+  return head ? `${head}\n\n${out}` : out;
+}