What Langsmith does

Langsmith Inc. (Langsmith株式会社) is a Tokyo-based, privately held Japanese corporation founded in May 2018 as a wholly-owned subsidiary of Machine Learning Solutions Co., Ltd. (MLS), with co-founders Takumi Ito and Tatsuki Kuribayashi (then doctoral students at Tohoku University's Inui-Suzuki Laboratory) and Takashi Goto as Representative Director. The company develops AI-powered writing-assistance systems that help users — particularly Japanese writers and non-native English researchers — convert thoughts into well-phrased text. Its current commercial product is Langsmith Cowriter, launched 2026-01-30 as a single Japanese-language plan at ¥1,500/month with a 7-day free trial, supporting the full writing workflow from draft generation through revision, persona-aware optimization, AI review, and AI chat. It replaces the discontinued Langsmith Editor (2020-2026), which offered domain-specialized English academic-writing engines covering NLP, ML, biology, chemistry, medicine, psychology, and 40+ computer-science sub-fields.

The underlying technology stack is built on neural sequence-to-sequence NLP models fine-tuned on large quantities of academic text from ACL Anthology and arXiv, producing revision candidates, full-sentence drafts, masked-position completions, and reviewer-style feedback. The company also maintains the publicly released TEASPN protocol/framework (Text Editing Assistance Protocol for Natural Language, GitHub: teaspn/teaspn-server) co-developed with Masato Hagiwara of Octanove Labs/RIKEN AIP, and has produced academic research including the STEP method for parameter-efficient LLM pre-training (53.9% maximum memory reduction vs. standard pre-training, NLP2025 Excellence Award). AI advice and research collaboration come from advisors Sugiyama (RIKEN AIP), Inui (Tohoku/RIKEN), Harada (Tokyo/RIKEN), Kashima (Kyoto/RIKEN), and Sato (Tokyo/RIKEN).

Langsmith's business model is a direct-to-consumer subscription at a single price tier for Cowriter, supplemented by an institutional arrangement with Tohoku University (signed 2022-01-25) that grants university affiliates free premium access in exchange for operational data feedback used to improve the AI. Distribution is entirely through Langsmith's own Japanese-language websites (corp.langsmith.co.jp, langsmith.co.jp, cowriter.langsmith.co.jp); marketing relies on owned-media content, Japanese press coverage, organic Twitter (@langsmith_nlp), and academic publication-based thought leadership. The company is privately funded through its MLS parent, whose shareholders include Transcosmos, Fuji Startup Ventures (Fuji Media Holdings group), and teamLab; no external funding rounds or revenue figures are publicly disclosed.

Name

Langsmith

Legal name

Langsmith株式会社 (Langsmith Inc.)

Website

https://corp.langsmith.co.jp

Company type

Private

Founded year

2018

Operating status

Operating

Headcount range

101–250 employees

Short description

Langsmith Inc. is a Tokyo-based, MLS-subsidiary AI company that operates Langsmith Cowriter, a Japanese-language generative-AI writing assistant (¥1,500/month) supporting drafting, revision, persona-aware feedback, and AI review for academic, business, and creative writers.

Ownership category

akta.pro rank

Product category

AI Writing Assistance Software

NAICS

Document Preparation Services (561410)

SIC

Books: Publishing Or Publishing & Printing (2731)

akta.pro primary industry

Content Generation & Writing Assistance (copy, emails, reports) (HDAAADAG)

akta.pro secondary industry

Manuscript Development Services (Coaching, Developmental Editing) (MPAJAJAF)

Keywords

• AI writing assistance
• Academic text revision
• Japanese language tools
• NLP writing software
• Generative AI assistant

Headquarters

HQ city

Tokyo

HQ country

Japan

HQ region

Asia

Offices3 records

Markets served

GTM type

B2C

Offering type

Software

Cost components

Personnel, Technology or R&D, Operations, Marketing or Sales, Infrastructure

Revenue model

1. Langsmith Cowriter monthly subscription: Primary current revenue stream. Single ¥1,500/month plan with 7-day free trial (credit card required at signup, no charge if cancelled within trial). Replaces the discontinued Langsmith Editor service.
2. Langsmith Editor Premium subscription (discontinued): Previously ran Free plan (NLP-only engine) + Premium paid subscription with domain engines (medicine, chemistry, biology, ML, image processing, NLP, psychology, CS). Service ended 2026-03-31 with refunds processed by 2026-04-30.
3. Tohoku University Plan (institutional license): Institutional arrangement granting Tohoku University affiliates free access to premium (most features) functionality under a cooperation agreement; operation data is shared back to Langsmith to improve the AI.

Pricing tiers

Go-to-market motion1 record

Distribution channels4 records

Marketing channels7 records

Core offering

Langsmith develops and operates an AI-powered writing-assistance SaaS, currently branded Langsmith Cowriter, that supports the end-to-end Japanese writing workflow from draft generation (from notes/outlines) through multi-candidate rewriting and AI-driven review that surfaces logical gaps and contradictions. The successor product is built on NLP and deep-learning models originally trained on large corpora of academic text; its predecessor Langsmith Editor offered field-specialized engines (medicine, chemistry, biology, psychology, computer science and sub-fields, NLP, ML) for English academic paper revision and was discontinued on 2026-03-31.

Product overview

Langsmith Inc. operates a single-product-architecture AI writing-assistance offering centered on the Langsmith Cowriter core product, supported by a discontinued predecessor (Langsmith Editor) and the publicly released open-source TEASPN protocol/framework that originally underpinned the editor. Langsmith Cowriter is the current GA product covering Japanese business, creative, and academic writing end-to-end (draft, revision, AI review); Langsmith Editor previously filled the same role for English academic papers with field-specialized engines; and TEASPN remains the public, open-source integration protocol that allowed third-party editors to connect to Langsmith-style language-processing modules.

Differentiator

Problem solved

Functional benefit

Brands

• Langsmith Editor: English academic paper writing assistance system using NLP and deep learning to suggest phrasing, correct errors, and continue drafts; discontinued March 31, 2026.
• Langsmith Cowriter (ラングスミス コライター)
• TEASPN (Text Editing Assistance Smartness Protocol for Natural Language)

Products and services

• Langsmith Cowriter (ラングスミス コウライター) AI writing-assistance SaaS for Japanese-language users that generates drafts from notes/outlines, produces multiple rewrite candidates (shorter, more polite, logic-supplementing), runs an AI Review that surfaces logical gaps and contradictions, optimizes output for a target persona/reader, and exposes AI workflow templates. Sold via a single ¥1,500/month subscription with a 7-day free trial; Japanese-only at launch.
• TEASPN (Text Editing Assistance Smartness Protocol for Natural Language) Open-source protocol and framework that standardizes the bridge between NLP modules (error correction, auto-completion, suggestion generation) and editors, enabling integrated writing-assistance environments. Reference implementation available on GitHub; used as the underlying integration protocol of Langsmith Editor.

Quantifiable outcome

• 53.9% reduction in maximum memory requirement during LLM pre-training using the STEP method (vs. standard pre-training), while maintaining equivalent performance
• +1 more outcomes

Named customers1 record

Segments4 records

Ideal customer profiles2 records

Technology focussed Yes

API detail

Has API

Yes

API docs

API detail

Core technology

AI maturity

App detail

Integration1 record

AI capability1 record

Feature9 records

Partnerships

Seven partnerships are on record, tiered minor, flagship and core.

• Team-J (Tohoku University, RIKEN, NAIST, Future Corporation, Langsmith)minorStrategic or Co-development Partner · 20 November 2024Joint research team for the WMT 2024 General Translation Task, producing the paper 'Document-level Translation with LLM Reranking'. Future Corporation, NAIST, RIKEN and Tohoku University are listed collaborators alongside Langsmith.
• Tohoku University (国立大学法人東北大学)flagshipStrategic or Co-development Partner · 25 January 2022Mutual cooperation agreement signed 2022-01-25. Tohoku University provides Langsmith Editor (later Cowriter) to its researchers and students free of charge under the Tohoku University Plan; operational data (user selections, edits) is fed back to Langsmith to improve AI accuracy. Founders Ito and Kuribayashi are graduate students of Tohoku University (Inui/Suzuki Lab).
• Octanove Labs (Masato Hagiwara, RIKEN AIP)coreStrategic or Co-development Partner · 3 July 2019Joint development of the TEASPN framework (Text Editing Assistance Smartness Protocol for Natural Language) — a protocol and framework for bridging NLP modules (error correction, auto-completion) with editors. Open-source release with GitHub server sample implementation (teaspn/teaspn-server). Demo paper co-authored at EMNLP-IJCNLP 2019.
• Machine Learning Solutions, Inc. (マシンラーニング・ソリューションズ株式会社, MLS)flagshipStrategic or Co-development PartnerMLS is the 100% parent company of Langsmith Inc. since founding in 2018. MLS is an incubator (machine learning consulting, funding/incubation of ML startups) whose shareholders include Transcosmos, Fuji Startup Ventures (Fuji Media Holdings) and teamLab.
• Edge Intelligence Systems, Inc. (エッジインテリジェンス・システムズ株式会社, EIS)minorStrategic or Co-development PartnerGroup/sister company of Langsmith, listed under 'Group Companies' on the corporate site; supported Langsmith Editor's front-end and back-end development.
• RIKEN AIP (RIKEN Center for Advanced Intelligence Project)coreStrategic or Co-development PartnerAffiliated with multiple Langsmith advisors and collaborators (notably Masato Hagiwara on the TEASPN work; also listed as WMT24 Team-J collaborator).
• Future Corporation (フューチャー株式会社)minorStrategic or Co-development PartnerCo-author/collaborator on the WMT 2024 Team-J paper 'Document-level Translation with LLM Reranking'.

Scale indicators6 records

Recent moves7 records

Expansion highlights5 records

Direct peers

• Rimo: Japanese AI summarization and writing service aimed at business document workflows. Closest direct competitor in the Japanese-language AI writing category, with similar business-document use cases and a Japanese go-to-market.
• Writesonic: AI writing assistant for articles, ads, and general content. Comparable subscription SaaS AI writing tool with overlapping drafting and rewriting functionality for SMB and prosumer users.
• LanguageTool: Multilingual grammar and style checker supporting Japanese among 30+ languages. Comparable subscription-based writing assistance model with overlapping target user (non-native/professional writers) and Japanese-language support.
• Stockmark: Japanese AI company offering AI writing and document-generation products for Japanese enterprises. Comparable Japanese-language AI writing offering with overlapping enterprise and business-document target segments.
• Jasper: AI content-generation platform for marketing copy, blogs, and business writing. Comparable AI writing subscription product targeting similar business-document and creative-writing use cases, though English-centric and marketing-focused.
• DeepL Write: Multilingual AI writing assistant from DeepL offering style, tone, and phrasing suggestions. Directly named by Langsmith as a competitor, and similarly positioned as an AI writing tool aimed at non-native English writers — a closely comparable direct peer.

Broad incumbents

• Grammarly: Global AI writing assistance leader with grammar, style, and tone suggestions. Langsmith explicitly positions against Grammarly on the 'how to say' dimension rather than surface correction, making it a comparable writing-assistance category incumbent though broader in scope and English-centric.
• Notion AI: AI writing features bundled inside the Notion workspace product. Competes for the same drafting/rewriting use cases Langsmith targets, but as part of a broader productivity suite rather than a specialized writing tool.

Emerging players

• ELYZA: Japanese-focused LLM developer offering Japanese-tuned language models and AI writing APIs. Comparable Japan-centric NLP technology stack with potential to power or compete with Langsmith Cowriter.
• AI inside: Japanese AI platform offering OCR, document automation, and generative AI for enterprise workflows. Adjacent Japanese AI ecosystem participant with overlapping enterprise document-AI use cases for the same Japanese corporate buyers.

Market position

Strengths5 records

Weaknesses5 records

Competitive moat5 records

Key risks6 records

Key highlights7 records

Customer concentration

• Xtwitter.com/langsmith_nlp
• GitHubgithub.com/teaspn/teaspn-server
• YouTubeyoutube.com/watch?v=9DNqpudDehM

Revenue estimate

Valuation estimate

Number of profiles

Profiles4 records

Funding overview

Funding rounds

Investors

Funding detail is available on the Subscription and Enterprise plan.Contact sales →

M&A

Investments

M&A and investment is available on the Subscription and Enterprise plan.Contact sales →

Frequently asked questions about Langsmith