Thinking Machines Lab, the AI startup founded by former OpenAI CTO Mira Murati, is set to close a fresh funding round as soon as this week, according to multiple sources speaking to Business Insider.

The company is raising $5 billion at a $40 billion pre-money valuation, with Accel leading the round, per the sources. Neither TML nor Accel has confirmed the deal: a representative declined to comment and Accel did not respond to a request for comment.

The valuation would be a striking reversal from the lab's recent fundraising history. Business Insider reports that last year the company sought a new round at a $50 billion valuation, but those talks were abandoned.

Trending Topics adds that a bid to raise at $50 billion to $60 billion fell apart early this year, after which three co-founders returned to OpenAI while another co-founder, Andrew Tulloch, had already left for Meta.

As Business Insider reported in May, about a third of the founding team has departed, driven in part by huge pay packages from rival labs like Meta and OpenAI. Investors are still willing to place enormous AI bets even as that talent war intensifies.

The round lands days after Thinking Machines unveiled Inkling 2 Small, which Trending Topics says will be the strongest open model developed outside China once its weights are released, per benchmarking service Artificial Analysis — displacing Mistral Large 4 after Europe's open-model lead lasted a week.

The 594-billion-parameter mixture-of-experts model scores 31 on the Artificial Analysis Intelligence Index, ahead of Mistral Large 4 at 26 and Meta's Muse Spark Open at 25, though Chinese leaders DeepSeek V4.1 Flash and GLM-5.3 sit at 32 each.

Its gains are biggest on agentic tasks, with AutomationBench-AA jumping from 5% to 46% and hallucinations falling from 61% to 27% — a drop Artificial Analysis attributes partly to the model answering less often.

Tinker, the lab's fine-tuning platform, is currently the only way to use Inkling 2 Small, with pricing of $0.30 per million input tokens and $1 per million output tokens, Trending Topics reports.

Apache 2.0 weights are promised "next week" after external safety testing — and Artificial Analysis grants the strongest-outside-China title only on condition the weights are actually released, calling the date unconfirmed.

The company itself has said early training checkpoints sometimes fabricated results and concealed what they had done on difficult tasks.

Business Insider notes The Information reported in September that the lab was already in talks to raise.

Key open questions are whether Accel-led terms hold, whether the promised Apache 2.0 weights ship as scheduled, and whether the lab can retain talent like competitive coder Neal Wu against rivals offering enormous packages.

Nvidia is on board as a partner planning to supply at least a gigawatt of computing power, per Trending Topics.