The Sinceerly Stack

Essay This entry carries an argument or interpretive position, not just a neutral definition.

The product

In April 2026, a Harvard MBA grad named Ben Horwitz launched a Chrome extension called Sinceerly — the doubled e being either a typo deliberately preserved or a feature, depending on how charitable one is feeling¹. The tagline reads, in the upright sans-serif that has become the house font of AI-skeptical tooling: AI to undo your AI writing.

The product is a humaniser. It takes text generated by an AI tool — typically a Gmail draft you wrote with ChatGPT or Claude or Copilot — and reverses the AI-shaped tells. From the marketing page, three product names for three intensity levels:

Subtle. Removes em-dashes, smooths the most obvious AI-isms, leaves most of the prose intact.
Human. Removes the “not just…” family of constructions. Strips em-dashes more aggressively. Adds occasional informalities.
CEO. All of the above, plus: drops words to lowercase. Adds typos. Inserts acronyms. Shortens. The marketing page advertises the result with mock email exchange in which the user’s careful corporate paragraph becomes “sent from my iPhone” plus three sentences with minor errors. The branding leans into the joke.

The founder’s own pitch, copied from the About section verbatim:

“Hi, I’m Ben. I got sick of everyone in my inbox sounding like AI. So I built Sinceerly. I tested Sinceerly by cold emailing 5 Fortune 500 CEOs. 4 CEOs replied. Of those replies, each was under 10 words. 2 replies had typos. One reply called me Larry (my name is Ben).”

The pitch is funny on at least three levels. It extrapolates from five cold emails and four replies, so it is marketing anecdote rather than evidence about how chief executives generally write. The Sinceerly product packages the anecdote as a service.

The product page also offers a free tier (three rewrites), a Pro tier at $4.99/month for unlimited rewrites, and — this is the load-bearing detail for the entry that follows — a Bring Your Own API Key option that lets the user supply an Anthropic key directly. The recursive stack is therefore explicit: a language model can be used to alter prose generated by the same model family or by a competitor.

The stack, named

The Dictionary names the structure that Sinceerly sits inside, because the name is more durable than the product:

The Sinceerly Stack: a recursive cat-and-mouse layer of AI tooling, in which each successive tool is designed to counteract the visible artifacts of the previous one. The current state of the stack, as of May 2026, has at least four layers:

AI to write. ChatGPT, Claude, Gemini, Copilot, and the broader ecosystem of language models used to generate first-draft prose.
AI to detect AI writing. Pangram Labs, GPTZero, Originality.ai, Turnitin’s AI-detection module, and competitors form a visible commercial market. Its precise size is not needed for the argument.
AI to remove the AI tells. Sinceerly is the worked example, but it is one of many humaniser products. What distinguishes it here is the explicit framing and the founder’s willingness to lean into the joke.
AI to detect the de-tellers. Detection firms have publicly described adapting to humanisers, creating the adversarial pattern the entry names. That establishes an active detection-and-evasion loop; it does not show that every vendor can reliably identify every humanised text.

A fifth layer is structurally possible: AI to remove the de-teller-detection signatures, or tools designed to alter the output of humanisers again. The entry predicts that each layer can create demand for the next; it does not claim evidence for a particular fifth-layer product.

Why this is a worked example of a deeper problem

The Sinceerly Stack is funny and the founder is funny and the product is funny, and the Dictionary appreciates a well-executed joke. But the entry is not, in the end, about the joke. It is about what the stack reveals about the underlying economy of AI writing.

The stack is adversarial against itself, and each additional layer imposes a cost. That cost may be money, tokens, time, privacy exposure, or attention. A user who enters at layer one becomes a potential customer for the detection and evasion layers that follow.

The stack does not produce trust. A reader who knows the Sinceerly Stack exists cannot, in fact, trust a slightly-typo-laden email more than a polished one. The typos may be authentic. The typos may be Sinceerly-CEO-mode. The stack has hollowed out the signal that informality used to carry — this person did not have time to polish, therefore the message is sincere — by automating informality. The stack increases the cognitive cost of every reader’s distinguishing labour. The Sinceerly Stack feeds the Zombie Internet, even when the individual tools at each layer are well-intentioned.

The stack creates suppliers at every layer. Model providers may sell additional inference; detection firms sell classification; humaniser firms sell evasion or stylistic alteration. Not every product uses the same provider or pricing model, but the general incentive remains: one layer’s output creates demand for the next layer’s service.

The stack assumes the wrong winning condition. Each layer is structured around the question can the AI provenance be detected?, which is the wrong question. The right question, as the parent entry AI Writing argues, is would I want to be reading this if I knew? The stack does not answer that question. It cannot. It is a stack of detection-and-evasion tools, and detection-and-evasion is not the same thing as trustworthy communication. The stack is therefore solving the wrong problem at every layer.

Max Spero, Pangram Labs’s CEO and one of the people most directly profiting from the stack’s existence, said the quiet part out loud in the Koebler piece: “It’s kind of looking grim for the future of the internet.” This is not the founder of a flat-earth conspiracy commenting on geography. It is the CEO of an AI-detection firm commenting on the stack his own product sits inside. The structural shape is bad enough that even the people running it are saying so.

What the Dictionary recommends

Do not enter the stack.

The recommendation is structural, not moralising. The Dictionary does not claim Ben Horwitz is wrong to have built Sinceerly. It does not claim the Pangram Labs detection economy is fraudulent or that the humaniser-detection arms race is going to ruin civilisation. The recommendation is operational: the stack is bad for the participating writer, in ways that compound across the layers, and the writer’s best move is to opt out at layer zero.

Opting out at layer zero means: when an email or message or post or essay matters, write it yourself, in your own voice, with the cadence of your own reading voice in your head. Use AI tools where they make sense for the task — research, summarisation, copy-editing, brainstorming — but produce the final prose with your own attention on the page. This is the cooperative-writing practice named in AI Writing and detailed across this cluster. It is the alternative to the stack.

The stack will continue to exist. Many users will participate in it. The Dictionary’s bet, in AI Writing, is that the cooperative-writing top — writers whose writing is read, who care about their own register — will be more visible against a background dominated by the stack, not less. Sinceerly’s existence is, in a sense, evidence for the bet. A market for AI-to-undo-AI emerged because the AI default is recognisable enough to be worth undoing. The undoing layer is itself an admission that the AI default has a fingerprint, and the fingerprint matters to the reader, and the writer wants to hide it.

The simpler move is not to leave the fingerprint in the first place. Write the email yourself. Layer zero is the recommendation.

A small note in defence of Ben

The Dictionary has been hard on the Sinceerly Stack in this entry, but is not, in the end, hard on Ben Horwitz. Two observations in his defence:

The product is funny on purpose. Horwitz is a Harvard MBA who has cold-emailed five Fortune 500 CEOs in order to learn that they write like exhausted humans. He has packaged that learning as a product. The Sinceerly marketing page is more honest about what the product does than most AI-tooling marketing pages of 2026, because the founder is in on the joke. The product is a satire that also works as a product. This is a non-trivial achievement and the Dictionary respects it.

The product makes the recursive problem unusually visible. Detection products offer a useful signal in some settings, but their scores can be mistaken for authorship verdicts and some tested systems have produced unequal false-positive rates. Sinceerly, by leaning into the absurdity, exposes the structure of the detection-and-evasion market. The Dictionary recommends opting out of that contest when the writer can do so.

A coda on the name

The name Sinceerly — with the doubled e — is doing more work than the founder may have intended.

Prof. Langenkamp’s essay The Sincere Society (Substack, May 2026) names the structural condition the Sinceerly Stack sits inside: feedback systems that have learned to reward the performance of a virtue rather than the virtue itself, in the way the 18th-century imperial Chinese examination system, the post-Revolutionary French Terror, and modern student-evaluation forms each, in their separate centuries, learned to reward the performance of cheng (誠 — alignment of inner state with outer expression) over the thing itself. The essay’s argument is that cheng in such systems is not a sentiment to be felt but an engineering requirement to be designed in — a structural property of the feedback loop, not a personal virtue of any one participant.

Sinceerly, the product, is precisely the failure mode the Sincere Society essay diagnoses, made into a Chrome extension. It names itself with a sincerity-marker (sincere) and a doubling cute-flag (the second e), because it has reduced sincerity to the stylistic-fingerprint problem — a thing addressable by typo-injection, em-dash-removal, and lowercase-coercion. It cannot do otherwise. A tool that fixes the fingerprint cannot fix the substance. If the underlying email is sincere, the AI fingerprint is a cosmetic concern. If the underlying email is insincere, removing the fingerprint does not make it sincere; it makes it insincere-without-the-fingerprint, which is worse, because it is now undetectable.

The marketing plainly leans into the joke. Sinceerly is funny because the name is doing part of the diagnosis the founder did not have to write. It is sincerity-by-other-means, packaged as a subscription. The Dictionary’s recommendation, restated for this section: do not enter the stack. Write the consequential email with enough attention that its final register is one you will own.