How does ForthWrite build its understanding of my writing?

On first connect, it batch-imports your full Gmail Sent folder, normalizes each message (stripping HTML and forwarded sections), and embeds them in a database. When you draft a reply, it queries for similar past emails, re-ranks them to avoid duplicate examples, and injects the best matches as few-shot examples into the prompt so the model imitates your actual sent writing rather than a description of your style.

How does the feedback loop work?

Every time you edit an AI draft and send it, ForthWrite calculates an edit-distance score between the generated version and what you actually sent. Low scores (heavy rewrites) feed an optimizer that suggests prompt updates; high scores (nearly verbatim sends) go into the corpus as positive signals. Separately, a word-level miner tracks deletions and substitutions you repeat across emails and writes explicit avoid or prefer rules to your system prompt.

When and how much does it cost?

ForthWrite offers a 14-day free trial with no card required. The body does not state pricing after the trial period.

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ForthWrite: Email AI That Learns From Your Edits

Hacker News6h ago5 min read

Key takeaway

ForthWrite is a Chrome extension for Gmail that learns your personal writing style by analyzing edits you make to AI-drafted emails. Unlike tools that ask you to describe your voice or impose static fine-tuning, it batch-imports your full sent-folder history, uses retrieval-augmented generation to pull real examples into each draft, and runs a deterministic word-level miner to catch small recurring phrases you remove—building a feedback loop that improves over time as you send emails.

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3 Key Points

What happened
ForthWrite, a Chrome extension for Gmail, uses a feedback loop to learn your writing voice. When you edit AI-drafted emails and send them, the tool measures how much you changed the draft (using edit-distance scoring) and feeds heavy-edit pairs to an optimizer that refines its system prompt, while near-verbatim sends become positive examples for future drafts.
Why it matters
Most email AI tools today claim to learn your voice but hit a ceiling—prompt engineering doesn't update, and fine-tuning is too expensive per user. ForthWrite imports your full Gmail Sent folder on first connect (not manual samples), then uses retrieval-augmented generation (RAG) with a word-level phrasing miner to catch small recurring edits you always make by hand, meaning the tool improves as you use it rather than staying static.
What to watch
The tool addresses a non-obvious problem: as the model improves and you make fewer edits, correction signals starve the feedback loop. ForthWrite solves this by running phrasing analysis on a time-based schedule independent of edit scores, so users in steady state still get periodic refinement. A 14-day free trial is available at forthwrite.ai.

FAQ

How does ForthWrite build its understanding of my writing?: On first connect, it batch-imports your full Gmail Sent folder, normalizes each message (stripping HTML and forwarded sections), and embeds them in a database. When you draft a reply, it queries for similar past emails, re-ranks them to avoid duplicate examples, and injects the best matches as few-shot examples into the prompt so the model imitates your actual sent writing rather than a description of your style.
How does the feedback loop work?: Every time you edit an AI draft and send it, ForthWrite calculates an edit-distance score between the generated version and what you actually sent. Low scores (heavy rewrites) feed an optimizer that suggests prompt updates; high scores (nearly verbatim sends) go into the corpus as positive signals. Separately, a word-level miner tracks deletions and substitutions you repeat across emails and writes explicit avoid or prefer rules to your system prompt.
When and how much does it cost?: ForthWrite offers a 14-day free trial with no card required. The body does not state pricing after the trial period.

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