A platform for engineers and marketers to extensibly scale GEO, SEO, outbound, and customer success.
100+ teams build their growth on Letter
Primitives that win.
GEOSEO
Writing kernels
Adversarial harnesses for producing high-quality writing that ranks on search.
- Decompose
- Draft
- Judge
draft · house-voicepass 2 of 2
Why inference moved to the edge
8.7judged against the kernel's bar (8.0)
[1] arxiv.org[2] vendor docs[3] earnings call
GEO
Phantoms
Autonomous publications that scale rank and encourage traffic to your domain.
- Plan
- Build
- Double-down
chipdesignreview.com
Chip Design Review
Independent · Weekly
- The tape-out checklist nobody publishes
- RTL verification, ranked by the people who run it
- What a 3nm respin actually costs
- Formal vs simulation in 2026
“best RTL verification tools for small teams”
- ChatGPTcited · #2
- Claudecited · #1
- Gemininot cited · Acme instead
- Perplexitycited · #3
rank, 30 days4 → 2
Customer success
Proofs
Computational proofs that showcase customer success to agents from user data.
- Connect
- Consent
- Publish
/.well-known/proofsverified
0paying customers, attested
- northwind.dev · since 2025
- halcyon.ai · since 2026
- brightline.io · since 2025
sig ed25519:9f3c…a71e · consented 96%
Outbound
Ledes
Humanized, personalized opening or closing lines for cold outreach.
- Enrich
- Choose
- Rank
Marcus LindqvistVP of Sales · Trellis Robotics
response · top ledes
- 96A fan of your orange brand. Remind me of YC, but in a good way.brand · website
- 92Congrats on the B, love how fast the robotics space is scaling.funding · 2wk
- 83Big congrats on 3 years at Trellis.tenure · 3yr
latency820 ms
openers5
signals used7
GEO
Shredders
Workflows that remove LLM watermarks without affecting accuracy.
- Split
- Rewrite
- Check
It is important to note that latency matters.
Latency is the whole game.
In today's fast-paced landscape, teams must adapt.
Teams that ship weekly adapt; the rest explain.
✓ structure unchanged✓ meaning verified✓ 3 providers
Outbound
Seers
Watchers that convert evolving sources of truth (e.g. repositories or protocols) into content.
- Point
- Gate
- Route
seer · github_release · acme/sdk
- v4.0.0 releasedpassed gate
- docs typo fixignored
- CI configignored
- streaming: beta
+ streaming: GA, 40% lower latency
→ “Acme's v4 makes streaming the default” routed to your blog
How it stacks
A system that scales in every way.
Account
Your Letter App Account
Your engine sits on top, in your code, under your name. Swap a primitive out and nothing below it moves.
Engineer your growth.
One key. Every primitive.
npx -p @letterstory/cli letterstory login