Changelog

What we've shipped, week by week.

We're building Rival Newsletter as a research project on agent-written email. This is the public log — every change to how the agents read, write, and personalise.

28 May 2026

Research

The editor agent now reads five context docs about each subscriber

We added a five-doc markdown system per subscriber — positioning, ICP, pricing, voice, differentiators. The agents draft them from each subscriber's live site, refresh them weekly, and let the subscriber lock or edit any of them. Every weekly brief now anchors its takeaways to those docs.

Feature

Six signal sources, scored and merged before composition

Beyond website diffs we now extract per-release entries from changelogs, per-post entries from blogs, web news from Bing News RSS (Google News blocks Cloudflare Workers — Bing doesn't), Reddit + Hacker News mentions, and snapshot diffs across pricing and feature pages.

Improvement

First-week briefs no longer fabricate change language

If you just signed up and there are no real moves yet, the editor agent switches to 'intro mode' — it summarises where each rival stands today in present tense, never claims they shipped anything. Anti-hallucination guard enforced in the system prompt.

Feature

Every theme ships with a ready-to-ship draft

≤30-word artifact per theme — a tweet, hero line, pricing copy variant — phrased in the subscriber's voice. The editor agent reads the voice doc and writes draft copy you can A/B test the same morning.

27 May 2026

Feature

Claude Haiku 4.5 in production for digest composition

Switched from Workers AI Llama-3.1-8B to Claude Haiku for digest composition. Takeaways went from generic 'review their pages' to specific marketing actions grounded in the subscriber's own positioning. Roughly $0.005 per brief.

Research

Subject-line validator rejects untracked-competitor names

Found the LLM occasionally hallucinated rivals not in the tracked list (e.g. 'Notion's Turn Next?' when Notion wasn't tracked). Added a hard validator: if the proposed subject line doesn't include at least one tracked brand or domain, we reject it and fall back to a deterministic template.

26 May 2026

Feature

Magic-link dashboard with editable business context

/r/[token] shows each subscriber's tracked rivals, latest brief, and the five context docs. Markdown textarea with debounced auto-save. Locked docs survive the weekly auto-refresh.

Fix

Server-side rendering of the dashboard moved client-side

The /r/[token] route was 500-ing on transient API hiccups because data fetching ran in the server component. Moved to a client-side fetch with proper loading / error / invalid states.

25 May 2026

Feature

Live on rivalnewsletter.com

Site → Vercel, Worker → Cloudflare on api.rivalnewsletter.com, all D1/R2/queues/Vectorize in the Spronta Ltd account. End-to-end signup flow live.