User feedback: previous prompt produced robotic word-for-word output that
lost the marketing impact. The system prompt was too restrictive on
preservation, suppressing Gemini's natural rephrasing ability.
Rewrote the system prompt with three structural changes:
1. FRAME shifted from "translator" to "senior marketing copywriter"
The opening line now says "You are NOT translating words — you are
rewriting marketing copy that lands the same way for a different
audience." This unlocks idiomatic rephrasing, sentence reorganization,
active/passive switching, and cultural metaphor adaptation.
2. FEW-SHOT EXAMPLES showing the desired style
4 FR→EN pairs in the prompt itself, with explicit "NOT: <literal>"
anti-examples to show what to avoid:
• "loyauté envers l'achat local" → "keeping it local"
(not "loyalty to local shopping")
• "connexions stables et relations durables" →
"steady connections — both the fiber kind and the human kind"
(not "stable connections and lasting relationships")
• "On est juste à côté" → "We're right next door"
• "Avec l'arrivée de l'été" → "Summer's here"
These ground Gemini in the brand voice with concrete examples.
3. TONE constraint explicit
"Warm, conversational, slightly playful. Like a neighbor explaining
something — never corporate, never stiff." Use of contractions
("we're", "you'll") encouraged.
Plus: temperature bumped from 0.2 → 0.7 so Gemini actually exercises
creative rephrasing instead of staying glued to source word order.
Structural preservation rules (HTML, Mustache vars, brand names, emojis,
URLs, technical values like "3.5 Gbit/s") kept as HARD CONSTRAINTS but
clearly separated from the creative freedom on text content.
Live re-translation of gift-email-fr → gift-email-en applied:
• 51s response time (similar to literal version)
• 35,934 → 36,067 bytes (slight expansion, normal for EN)
• Output markers confirm idiomatic phrasing landed:
"Thanks for keeping it local", "steady connections — both kinds",
"right next door", "lending a hand", "Summer's here"
• Mustache vars + brand names + HTML preserved (verified)
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
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