Voice-matched drafts - it writes like you, not like ChatGPT
BusinessOnce a week, RadiusOS reads your recent sent emails and learns how you actually write - sentence cadence, openers, sign-off, formality. Future drafts (Morning Digest, on-demand follow-ups, Ask RadiusOS) come back in your voice instead of generic AI voice.
What it is
Most AI email tools sound like AI. They're trained on the entire internet, so the drafts read fluent but generic - the cadence is too even, the openers are too friendly, the sign-offs are too long. Recipients can tell.
Voice-matched drafts close that gap. Each week, RadiusOS reads ~10 of your recent sent emails (from your connected Gmail) and asks Claude Haiku to summarize how you write - sentence length, opener phrases, formality, sign-off, the words you reach for. That summary plus 3 redacted exemplars get layered onto every future draft this workspace generates.
Voice-matched drafts are a Business / Team feature and require Gmail connected. Drafts on Free / Pro and on Business workspaces without Gmail still work - they just fall through to the existing generic professional voice.
How it works
Weekly cron at 06:00 UTC Sunday
RadiusOS connects to your Gmail using the same OAuth token that powers Gmail sync, scans the last 30 days of sent mail, and pulls up to 10 emails you actually wrote (forwarded threads and quoted reply chains stripped out).
Haiku reads them and builds a voice profile
Claude produces a 200-400 word paragraph describing the patterns: "Short, often fragment-like sentences. Opens with a context line, no greeting. Signs off with first name only. Uses 'quick one for you' as a recurring opener." The profile is stored on your workspace, not on a contact record.
Three exemplars get cached too
The actual subject lines and short body excerpts of your three most recent sent emails are stored alongside the profile. They give the model concrete reference text to anchor on - the profile describes the voice, the exemplars demonstrate it.
Every future draft picks both up
When the Morning Digest cron drafts a follow-up, when you click "Draft a follow-up" on a contact, or when Ask RadiusOS drafts on your behalf, the profile gets layered as a third cached system block on top of the base draft prompt and the vertical context. The exemplars ride in the user message.
Refreshes weekly
The cron re-runs every Sunday and rewrites the profile from your most recent sent mail, so the voice stays current as your style evolves.
What gets profiled and what doesn't
The profile builder only reads emails you SENT - never received emails, never inbox content. It also filters out:
- Forwarded marketing emails or system-generated mail (where the From header doesn't match your address)
- Emails shorter than ~20 characters (one-word replies, auto-acknowledgments)
- Quoted reply chains and signature blocks (so we profile what you actually wrote, not what you replied to)
If your sample is thin (fewer than 5 sent emails in the last 30 days) we skip the profile entirely rather than build one from a tiny, unrepresentative sample. The next week's cron tries again.
What the model is told to do
The profile contains tactical observations only - sentence structure, real phrases, sign-off habits. No personality language, no "the user is friendly and professional." Concrete patterns the next model can match.
Voice-matching is presentation. The base draft prompt's correctness rules - USER vs CONTACT separation, persona handling, vertical guardrails (especially for compliance verticals like therapist and financial advisor) - all override voice. A roofer's profile cannot bend a therapist workspace into clinical language; the compliance guardrails win.
Privacy
Three things to know:
- The voice profile and exemplars stay on your workspace. They never leave RadiusOS except when included as context on a Claude API call you initiated (or that runs on your workspace's behalf, like the Morning Digest cron).
- We don't store full email bodies long-term - the exemplars are 400-character excerpts of subject + body, and only three of them.
- Disconnect Gmail in Settings and the cron stops running for your workspace. Existing profile data persists until the next refresh attempts to write over it; you can also clear it by request.
Cost
One Haiku call per workspace per week to build the profile (~$0.001/workspace/week with the system prompt cached). Each draft after that pays roughly $0.0008 extra for the voice context block - well below the noise floor of typical Business+ usage.
Drafts still consume one AI credit each on Free and Pro tiers. Business and Team get unlimited drafts (fair-use ~5K/mo on Business, ~10K/mo on Team).