AppFactor raises $4m to hand legacy code upkeep to AI agents

On 4 February AppFactor, a London-based software company, announced a $4m (£3m) seed round led by Tensor Ventures, with Begin Capital, Adara Ventures and Narwhal Investments also taking part. The money will go on go-to-market work and on extending the platform, the company said, including what it calls autonomous refactoring that turns legacy software into “self-maintaining, secure, cloud-ready assets”.

AppFactor sells an agentic orchestration platform: a layer of specialized AI agents that takes on the maintenance work enterprise engineering teams carry year after year. The release lists bug fixes, vulnerability patches, dependency updates and code smell remediation, up to full code migrations and rewrites. Its stated aim is software that maintains itself “without a developer ever opening an IDE”.

“Enterprises have brilliant engineers spending the majority of their time maintaining the past instead of inventing what’s next,” said Keith Neilson, AppFactor’s chief executive and a co-founder. “AppFactor changes that by turning software upkeep into an autonomous, closed-loop process.”

The release casts the rest of the industry as racing to embed AI assistants in code editors. AppFactor’s pitch, and the case its investors have backed, is that the larger cost sits in code companies already run, and that buyers will let agents change that code if every change passes through the same review gates as a human engineer’s. Tensor, in its own announcement of the deal, describes maintaining thousands of outdated applications as a burden for “large and medium-sized companies around the world”.

Three founders from cloud migration

Neilson founded the business with Gabriel Ciuloaica, its chief technology officer, and Attila Vajda, who leads product and engineering, according to the company’s website. AppFactor.io Ltd was incorporated on 21 June 2021, Companies House records show, and Neilson holds more than 25% but not more than 50% of its shares. The company lists offices on Euston Road in London and in Cluj-Napoca, Romania.

The idea came out of the founders’ earlier work. The company’s website says the team had “lived and breathed application modernization and cloud migration for the best part of a decade”. Adara Ventures, which describes itself as a co-lead of the round in its own note on the deal, says Neilson previously built and sold a modernization product to AWS. In August 2023 the company closed an oversubscribed pre-seed round led by Haatch, as reported by IFA Magazine.

Agents that work through review gates

According to the release, the platform runs its own discovery system that scans where software is actually running and flags vulnerabilities, code smells and infrastructure misconfigurations in real time. The agents are given the topology of each workload: its repositories, the dependencies between them, the underlying infrastructure and the links between components. Every task produces human-readable success criteria, so a team can see what the system is trying to do and check that it has done it.

The release uses vulnerability remediation as its worked example. When a library crosses a CVSS threshold or a known CVE turns up in the environment, the system locates the issue, proposes a fix, generates and runs system-level tests, verifies performance and rolls the change to production with progressive delivery. Changes travel through pull requests, approval gates and existing code review, with full auditability.

The company also offers to regenerate code in Rust, with integration tests generated alongside, and pitches this at estates running COBOL, compute-heavy workloads or large cloud bills. It says Rust rewrites can cut costs through better performance and lower resource use.

What the investors are paying for

Tensor is a Czech deep-tech investor, and the AppFactor stake comes from its second fund, which holds €50m (about £44m). Ondřej Lipold, one of the Tensor partners in charge of the investment, said the firm had “never seen a company that could monitor, modernize, and then deploy updates to functioning applications without impacting the end users”.

Begin Capital’s Saagar Bhavsar, a general partner there and a director of AppFactor.io Ltd since 19 September 2025 according to Companies House, said the platform “tackles the 1.5 trillion dollar technical debt problem holding these companies back”. The $1.5tn (£1.1tn) figure is his; the release gives no source for it.

On customers, the release says only that “initial large enterprise customers” are using the technology to compress modernization timelines and move applications to serverless compute, managed databases and event-driven architectures. Tensor’s announcement goes further: AppFactor has deployed its product at one of the largest banks in England and at one of the top 10 companies in the Fortune 500. Neither is named.

AppFactor has built its platform around pull requests and sign-off rather than the developer’s editor, so every change an agent makes goes to the same reviewers as a human engineer’s. Until the bank or the Fortune 500 company agrees to be named, the claim that enterprises will hand their legacy estates to those agents rests on its investors’ account.