bchanot-cv/.claude/memory/learnings.md

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type: learnings_registry entry_prefix: LRN schema: id: LRN-XXX date: YYYY-MM-DD pattern: string (what was observed, abstracted) context: string (where/when it happened - concrete) future_application: string (when to recall this) rules:

• Capture learnings that apply beyond the current task.
• Abstract from the incident - the pattern is what is reusable, not the one-shot fact.
• Link to source (commit, file, PR) when possible. ---

Learnings registry (LRN)

Index

ID	Date	Pattern	Applies to
LRN-001	2026-05-15	certbot --nginx matches server_name, not filename	nginx + certbot on multi-site VPS
LRN-002	2026-05-17	PIL supersample ×8 + Lanczos = clean icon antialiasing	Python stdlib icon generation

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LRN-001 — certbot --nginx matches server_name, not filename

• Date: 2026-05-15
• Pattern: certbot install --cert-name X (and certbot --nginx -d X) locates the target vhost by scanning every server_name directive in active nginx configs. The filename in sites-available/ is irrelevant. A file named X.conf with server_name Y; inside will NOT be picked up for domain X.
• Context: /etc/nginx/sites-available/bchanot.fr existed and was symlinked into sites-enabled/, but its body still contained server_name autreprojet.fr www.autreprojet.fr; — a copy-paste leftover from a previous project. Certbot returned Could not automatically find a matching server block for bchanot.fr.
• Future application: Before running certbot on a multi-site VPS, grep -n "server_name" /etc/nginx/sites-enabled/* — confirm the target domain is actually declared inside, not just present in the filename. Same logic applies when troubleshooting "why is nginx serving the wrong site" — match by server_name, never by filename.

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LRN-002 — PIL supersample ×8 + Lanczos = clean small-format icon antialiasing

• Date: 2026-05-17
• Pattern: Render icon at 8× target size via ImageDraw.rounded_rectangle + ellipse on RGBA canvas, then Image.resize((target, target), Image.LANCZOS). Output rivals rsvg-convert / inkscape for simple geometric shapes. Crisp at 16×16 favicon scale, no visible jaggies.
• Context: Generated favicon-32.png, apple-touch-icon.png (180×180), favicon.ico (multi-size 16/24/32/48) for bchanot.fr from scratch — no rsvg-convert / inkscape / ImageMagick on host. Single PIL script, ~20 lines.
• Future application: Any project needing a PNG/ICO icon set with a stdlib-only Python toolchain. Skip if shape is complex (text rendering, gradients, curves) — use rsvg-convert or commit a finalized PNG instead.