# Vespper

Aiolum story: https://aiolum.com/story/vespper/ · added 2026-11-12 · updated 2026-11-12

**In short.** Vespper (A fine-tuned model that lets AI agents edit Word documents, United States): Self-serve paid plan on sale, November 2026. Evidence grade E: no revenue figure was checked. Team: 2 co-founders; team size 2 on Y Combinator's company page, November 2026. Launched March 2024; still running.

A fine-tuned model that lets AI agents edit Word documents · United States · AI-native · team of 2 to 10 · still running · group: Developer tools and coding agents

- Outcome: Self-serve paid plan on sale, November 2026 (evidence grade of the headline number: E; no revenue figure)
- Launch: March 2024; months from launch to the outcome: 32
- Team: 2 co-founders; team size 2 on Y Combinator's company page, November 2026
- Outside funding: Y Combinator Fall 2024 batch; no amount stated in the sources read
- Main factor: Product
- Meters, 1 to 4: evidence strength 1, copyable pattern 2, capital needed 2
- Tags: AI-native, Small team, Funded, Running, B2B, Developer tools

Links:

- Visit vespper.com: https://www.vespper.com/

**The product.** A hosted service that lets an AI agent read, search and edit Microsoft Word files without handling the file's XML. The agent works on a simplified HTML view. A small fine-tuned model writes the matching change into the original file as a Word tracked change.

**Why it worked.** Vespper sells a single job to people who build AI agents: editing Word files without breaking their styles. The company says a model trained for this one step makes the agent cheaper and faster than the alternatives. It is the company's own benchmark, and no outside test is in the sources.

Evidence grades: A = disclosed by a public company, a filing or a payment processor, or verified by one; B = two or more independent reports agree, or a journalist confirmed it; C = a founder claim that no one else verified; D = reported, not verified: one founder claim or a third-party estimate with no second source; E = no revenue figure found, so the headline is a non-money fact and the other facts carry their own grades; calc = computed on this page from graded facts.

## Summary

Vespper is a service for DOCX editing, which means changing a Word file. A DOCX file is a zip archive of XML files, a verbose text format that costs an AI model many tokens. Vespper shows the agent HTML instead, and a reconciler model writes each change back into the original file. The service is an MCP server, a standard way for an AI agent to call outside tools.

Topaz Turkenitz and Dudu Lasry run the company; Y Combinator lists the team size as 2. The company's own pages date from March 2024, when the product was an AI helper for on-call engineers called Merlinn. It then became Vespper, moved to an AI document editor, and launched the Word MCP on 1 September 2026. The pricing page lists a free plan with 500 edits and a Starter plan at US$100 a month for 10,000 edits.

No revenue figure, customer number or named paying customer was found, so the story is grade E. The pricing page says self-serve card billing is included, and a sign-up button leads to the company's app. No source states that a customer has paid.

## Why did Vespper work?

### A small model writes the change instead of an agent loop

The company says a step of 20 seconds for each edit would give users a poor experience. So it did not use an agent loop. It trains a model of 3 to 8 billion parameters to turn old HTML, new HTML and old XML into new XML for one block. The agent never sees the XML.

### The agent works on HTML and Word gets tracked changes

The about page says Vespper exposes Word files as high-fidelity HTML and applies the change to the original file with tracked changes. A legal or compliance team can review each edit in Word. The company says this keeps styles, lists and tables.

### Pricing counts edits, so cost follows the agent's work

The pricing page charges for edits, with 500 free ones and 10,000 a month on Starter. A builder of document agents pays more only when the agent edits more. Enterprise adds self-hosting, SSO and audit logs for sensitive documents.

## How it was built

These details come from the company's launch article, privacy notice and pricing page. They are grade C.

- The reconciler was trained with supervised fine-tuning, using the Unsloth framework and Modal for GPUs, according to the launch article.
- The company says it built the HTML view itself. Converters such as pandoc and mammoth.js did not produce clean, high-fidelity HTML.
- A deterministic locator finds the matching block of XML, so the model only writes the new XML.
- The service is offered as a hosted MCP endpoint, with Python and TypeScript SDKs announced on 27 September 2026.
- The privacy notice says the website uses Vercel Analytics, PostHog and Warmly.

Sources: [6, 8, 2]

## Who tried this before Vespper, and why did they fail?

Two companies in our database of failed startups built online tools for writing and editing documents. The values below are from that database, were read on 12 November 2026 and are not independently verified.

The failed startups come from our database of dead startups, retold here in our own words; Its entries are AI-assisted summaries of public sources, so they carry no evidence grade.

### Draft (2011 to 2014; funding US$120K cash burned; cause: Competition)

- Promise: A cloud writing and editing tool with version control and tracked changes between writers and editors.
- Why it died: The record says it had an overly niche focus and little difference from existing tools. It adds that Google Workspace and Microsoft 365 now lead the market.
- Record: 

### Graphite Docs (2018 to 2020; funding US$400K cash burned; cause: Business model)

- Promise: A privacy-focused alternative to Google Docs, built on a blockchain.
- Why it died: The record says the business model was not sustainable, because privacy added friction for the users it wanted to charge.
- Record: 

## What changed

Both records built a better place to write a document, and both met Google and Microsoft, who own the place where most documents live. Vespper does not replace Word. It sells to the builders of agents that edit Word files, so Word is the file format that its customers already use.

The risk is that a model provider or Microsoft adds a built-in way to edit Word files. The company's own blog post of 24 October 2026 tested four other Word MCP servers and a python-docx baseline on 180 legal tasks. It reports that the baseline had the highest mean score and the lowest cost, and that one server had a higher all-pass rate. The post did not test Vespper.

## Can one person copy Vespper now?

**Verdict: The structure can be copied; the result is not shown.**

A small team can pick one file format that agents handle badly. It can train a small model for the one step that fails, and sell it by usage. The sources show a price list and a benchmark, and they show no customer or revenue. Treat this as a pattern, not as proof that it earns.

1. Pick a file format that agents edit badly, such as Word, where the raw format is large and fragile.
2. Give the agent a simple view of the file and keep the raw format away from the agent.
3. Train a small model for the one conversion step, and measure it against a plain baseline.
4. Charge by edit, with a free allowance and a flat monthly plan.

**What is still open.** Other formats where agents break the file: spreadsheets, slide decks, PDFs with forms, and the layout formats that design tools use.

## How much revenue does Vespper make? The numbers, graded

A two-person Y Combinator company on its third product, with a self-serve price list and no revenue figure

| Fact | Value | Grade | Note | Sources |
|---|---|---|---|---|
| Company and founders | Vespper Inc.; Topaz Turkenitz, co-founder and CEO; Dudu Lasry, co-founder and CTO | C | The company's about page names both as co-founders. Its footer reads Vespper Inc. Y Combinator's page lists the same two as active founders. | [7, 1, 3] |
| Start of the company | 2024; Y Combinator Fall 2024 batch | C | Y Combinator's company page says Founded: 2024. The oldest dated copy of the company's pages is from March 2024, under the name Merlinn. | [3, 13, 12] |
| Earlier names and products | Merlinn, an AI helper for incidents (2024); Vespper on-call engineer (October 2024); AI document editor (by April 2026); Word MCP (1 September 2026) | C | Each entry comes from a dated page of the company. The Vespper site of November 2024 still used Merlinn addresses in its page code. No page read states the rename in words. | [11, 12, 13, 14, 4, 15, 16, 5] |
| Team | 2 people | C | Y Combinator's company page says Team Size: 2 and Jobs 0, read on 12 November 2026. The Vespper site of November 2024 and the launch post of October 2024 also name only Topaz and Dudu. | [3, 14, 4] |
| Funding | Y Combinator Fall 2024 batch; no amount stated | C | The home page says Backed by Y Combinator. No source read gives an amount or other investors. | [1, 3] |
| What is sold today | A hosted MCP server and SDKs that let agents edit Word files; the model is fine-tuned for that task | C | The launch article says the reconciler model has 3 to 8 billion parameters. It was trained with LoRA on about 16,000 tasks. | [6, 1] |
| Prices today | Free; Starter US$100 a month; Enterprise custom | C | The company's pricing page, read on 12 November 2026. Starter lists 10,000 edits a month at 1 cent per edit. | [2] |
| How a plan is bought | Self-serve sign-up; the page says self-serve card billing is included | C | The Free button and the Starter button, which reads Get Pro, lead to the company's app. Its sign-in page offers e-mail or Google sign-in. The terms say commercial terms are those shown when you subscribe. No checkout page was read, and no source names a payment processor. | [2, 17, 9] |
| Company's benchmark of cost per task, 1 September 2026 | US$0.054 for Vespper against US$0.157 for the DOCX skill | C | The company's own benchmark on its home page. It also states task accuracy of 81.4% against 78.1%. No outside test of Vespper was found. | [1, 6] |
| Launch posts on Y Combinator's site | 31 October 2024 (on-call engineer; 74 votes); 1 September 2026 (Word MCP; 5 votes) | C | The company's own posts and Y Combinator's vote counts, read on 12 November 2026. Neither post gives a customer or revenue number. | [4, 5] |
| Prices of the Merlinn product, April 2024 | Free; Business US$600 a month; Enterprise on request | C | An archive copy of the Merlinn site dated 13 April 2024. The Business plan's button reads Contact Us. | [11] |
| Paying customers | No source states that any customer has paid | C | The company's pages, blog and launch posts were read. They show a price list and no customer, revenue or user number. | [1, 2, 10] |

How to read this table. Grade C means the company states the value, or a dated archive copy of its own page shows it. No value is grade A or B, and no calc value is used.

## Pricing

Vespper prices read from the company's pricing page on 12 November 2026 (grade C)

| Plan | Per month, billed yearly (US$) | Per month, billed monthly (US$) | Limit |
|---|---|---|---|
| Free |  | 0 | 500 one-time edits, 1 seat, community Slack channel |
| Starter |  | 100 | 10,000 edits a month (1 cent per edit), unlimited seats, auto top-up, zero data retention, uptime SLA |
| Enterprise |  | custom | custom edit volume, self-hosting or private VPC, SSO, audit logs; the button reads Talk to founders |

The page lists a flat monthly price per plan and one cent per edit on Starter. The Free plan's 500 edits are one-time. The Starter plan includes unlimited seats, auto top-up, zero data retention and an uptime service-level agreement. Enterprise has custom prices and a Talk to founders button.

## When did Vespper launch, and how did it grow? Timeline

From an incident helper called Merlinn in March 2024 to a Word editing service with a price list in November 2026.

- **March 2024** (grade C [11, 12, 13]): Archive copies show the Merlinn site and docs, an AI helper that investigates production incidents. A blog post is dated 30 March 2024, and the site lists a free plan and a US$600 Business plan.
- **29 June 2024** (grade C [12]): The Merlinn blog announces an open-source and community edition.
- **31 October 2024** (grade C [4, 14]): Y Combinator launch post for Vespper: 24/7 AI on-call engineer. An archive copy of the site from 6 November 2024 carries the name Vespper.
- **April and May 2026** (grade C [16, 15]): Archive copies of the home page and the pricing page show an AI editor for professional documents. The pricing page lists a free Starter plan, a Professional plan with a Contact sales button, and Enterprise.
- **1 September 2026** (grade C [5, 6]): Y Combinator launch post and launch article for the Word MCP, a model fine-tuned to edit Word files.
- **24 October 2026** (grade C [10]): A company blog post compares four other Word MCP servers and a python-docx baseline on 180 legal tasks. It leaves Vespper out.

## What could go wrong for Vespper?

- **What is not verified.** No revenue figure was found, so the story is grade E. The home page, pricing, about, security, privacy and terms pages, the blog and the Y Combinator pages were read. The company says self-serve card billing is included, and no source states that a customer has paid. A reader could look for a payment-processor profile, a press interview or a named customer. Y Combinator says the company was founded in 2024, and the oldest dated page is from March 2024 under the name Merlinn.
- **The company is on its third product.** The company offered an incident helper in 2024, an AI document editor by April 2026, and the Word MCP from 1 September 2026. The archive copy of the pricing page of 14 May 2026 has a Testimonials section headed "Hear what experts have to say". It shows three quotations signed only with a job title and a type of company, such as Senior Scientist at a life sciences company. Each one describes a need for an automated report tool, in the conditional. None names Vespper or says the speaker used it. The current pages show no testimonial.
- **The benchmark is the company's own.** The home page says the model is the only state-of-the-art post-trained model for Word editing, and states cost, accuracy and speed gains. The launch post calls it an internal benchmark. The company's later post of 24 October 2026 did not include Vespper and said its results would follow.
- **The home-page logos are the founders' earlier employers, not customers.** The home page shows the logos of Google, Snyk and Viz.ai under the words Made by professionals from. Y Combinator's page lists Snyk, Google, Viz.ai and SafeBreach as earlier employers of the founders. No source shows these companies as customers. The home page also shows a Backed by Y Combinator badge, and Y Combinator lists the company in its Fall 2024 batch. The security page says a SOC 2 program is in progress, and the home page does not call the service compliant.

## Sources

1. Vespper home page: DOCX MCP Server — https://www.vespper.com/ (grade C). Read in full on 12 November 2026. Source for the product description, the benchmark figures, the badge, the logo wall and the footer.
2. Vespper pricing page — https://www.vespper.com/pricing (grade C). Read in full on 12 November 2026. Source for the plans, the prices, the self-serve billing row and the sign-up links.
3. Y Combinator company page: Vespper — https://www.ycombinator.com/companies/vespper (grade C). Read in full on 12 November 2026. Source for the founders, the batch, the year founded and the team size.
4. Y Combinator launch page: Vespper: 24/7 AI on-call engineer — https://www.ycombinator.com/launches/M9l-vespper-24-7-ai-on-call-engineer (grade C). Read in full on 12 November 2026. The company's own post, created on 31 October 2024, with 74 votes.
5. Y Combinator launch page: Vespper DOCX MCP — https://www.ycombinator.com/launches/TSL-vespper-docx-mcp (grade C). Read in full on 12 November 2026. The company's own post, created on 1 September 2026, with 5 votes.
6. Vespper blog: Launching Vespper DOCX MCP — https://www.vespper.com/blog/launching-vespper-docx-mcp (grade C). Read in full on 12 November 2026. Source for how the model works, how it was trained and the benchmark method.
7. Vespper about page — https://www.vespper.com/about (grade C). Read in full on 12 November 2026. Source for the co-founder roles and the description of the product.
8. Vespper privacy policy — https://www.vespper.com/privacy (grade C). Read in full on 12 November 2026. Source for the analytics providers.
9. Vespper terms and security pages — https://www.vespper.com/terms (grade C). Read in full on 12 November 2026, with the security page at https://www.vespper.com/security. Source for the account terms and the SOC 2 status.
10. Vespper blog: Benchmarking DOCX MCPs on Harvey LAB — https://www.vespper.com/blog/docx-mcps-harvey-lab (grade C). Read the introduction, the setup and the results on 12 November 2026. Dated 24 October 2026; it does not include Vespper.
11. Internet Archive copy of the Merlinn site, 13 April 2024 — https://web.archive.org/web/20240413143257/https://www.merlinn.co/ (grade C). Read in full on 12 November 2026. Source for the Merlinn product description and the plans and prices of that date.
12. Internet Archive copy of the Merlinn blog, 7 September 2024 — https://web.archive.org/web/20240907100309/https://www.merlinn.co/blog (grade C). Read in full on 12 November 2026. Source for the blog dates of 30 March, 29 June and 1 July 2024.
13. Internet Archive copy of the Merlinn docs, 20 March 2024 — https://web.archive.org/web/20240320094754/https://docs.merlinn.co/ (grade C). Read in full on 12 November 2026. The oldest dated copy found; the archive offered no earlier copy for requests dated 2022 and 2023.
14. Internet Archive copy of the Vespper site, 6 November 2024 — https://web.archive.org/web/20241106152801/https://www.vespper.com/ (grade C). Read in full on 12 November 2026. Source for the on-call product, with the Merlinn address still in its page code.
15. Internet Archive copy of the Vespper pricing page, 14 May 2026 — https://web.archive.org/web/20260514193621/https://www.vespper.com/pricing (grade C). Read in full on 12 November 2026. Source for the AI document editor, its prices and its three testimonials.
16. Internet Archive copy of the Vespper home page, 21 April 2026 — https://web.archive.org/web/20260421103605/https://www.vespper.com/ (grade C). Read in full on 12 November 2026. Source for the AI document editor description of April 2026.
17. Vespper app sign-in page — https://app.vespper.com/login (grade C). Read in full on 12 November 2026. Source for the e-mail and Google sign-in options that the plan buttons lead to.
18. Database of failed startups, local export — /method/#dead (grade C). Record pages read on the website on 12 November 2026. AI-written summaries, not independently verified.

Contact: aiolum@livyden.com. Run Vespper? Send corrections or a verified figure to aiolum@livyden.com (subject: Correction: Vespper).