fix(confirmation): recognize localized subscribe CTAs in weak link signals

The weak link-signal vocabulary was English-only, so a genuine double
opt-in whose confirm button reads "Je m'inscris…" over an opaque tracking
redirect scored 0 on every link and was missed. Make the weak vocab
multilingual (FR/DE/ES) to match the confirmation keywords.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

CHANGELOG.md

@@ -21,6 +21,11 @@ verbatim as the GitHub Release notes — so what you write here is what ships.
 
 ### Fixed
 
+- Subscription-confirmation detection now recognizes localized "subscribe" CTAs.
+  The weak link-signal vocabulary was English-only (`subscrib`),
+  so a genuine double opt-in whose confirm button reads "Je m'inscris…" over an
+  opaque tracking redirect scored 0 on every link and was missed. The weak vocab
+  is now multilingual (FR/DE/ES) to match the confirmation keywords.
 - Per-feed favicons no longer fail for senders whose DuckDuckGo icon is a
   hi-res PNG: the maximum accepted favicon size is raised from 100 KB to 256 KB,
   so legitimate large icons (~107 KB and up) are cached instead of rejected.

src/domain/confirmation.test.ts

@@ -178,6 +178,27 @@ describe("detectConfirmation", () => {
     expect(result![0]).toContain("click.example.com");
   });
 
+  it("detects a French confirm email whose CTA text is a localized 'subscribe' over an opaque tracking href", () => {
+    // Real-world double opt-in: subject/body clearly confirm, but the
+    // button's href is an opaque provider redirect (proc.php?…&act=csub — no
+    // signal) and its visible text "Je m'inscris…" is the French equivalent of
+    // "subscribe" (a weak signal). The weak vocab must be multilingual like the
+    // confirmation keywords, otherwise the link scores 0 and the email is missed.
+    const result = detectConfirmation({
+      subject: "[Action requise] Confirme ton inscription",
+      text: "Avant de confirmer ton inscription, clique ici.",
+      links: [
+        {
+          href: "https://email.example.com/proc.php?nl=1&f=36&s=abc&act=csub",
+          text: "Je m'inscris sur la liste d'attente",
+        },
+        { href: "https://www.example.com/", text: "Notre site" },
+      ],
+    });
+    expect(result).not.toBeNull();
+    expect(result![0]).toContain("proc.php");
+  });
+
   it("dedupes a confirmation link repeated in the body", () => {
     const result = detectConfirmation({
       subject: "Confirm your subscription",

src/domain/confirmation.ts

@@ -48,11 +48,18 @@ const STRONG_LINK_SIGNALS = [
 
 // Weak signals: ambiguous subscribe/subscription words that also appear in
 // ordinary "manage subscription" footers. Matched on the link href OR its visible
-// text (a CTA button often reads "Yes, subscribe me…" over an opaque tracking
-// redirect). Worth only +1 — and only once, never href+text additively — so they
-// cannot, on their own (with a stray body keyword), cross the threshold and cry
-// wolf, yet still let a genuine "confirm your subscription" email pass.
-const WEAK_LINK_SIGNALS = ["subscription", "subscribe"];
+// text (a CTA button often reads "Yes, subscribe me…" / "Je m'inscris…" over an
+// opaque tracking redirect). Worth only +1 — and only once, never href+text
+// additively — so they cannot, on their own (with a stray body keyword), cross
+// the threshold and cry wolf, yet still let a genuine "confirm your subscription"
+// email pass. Multilingual like KEYWORDS (EN / FR / DE / ES) — extend per language.
+const WEAK_LINK_SIGNALS = [
+  "subscrib", // EN: subscribe / subscription (unsubscribe is caught by NEGATIVE first)
+  "inscri", // FR: s'inscrire / inscription / je m'inscris
+  "anmeld", // DE: anmelden / anmeldung
+  "suscrib", // ES: suscribir / suscripción
+  "inscrib", // ES: inscribirse / inscripción
+];
 
 // Negative patterns: a link matching any of these is NEVER a candidate, and these
 // tokens are stripped from text before keyword scanning (kills the unsubscribe