Mistral got a US patent on tool calls in 118 days. Without prior public notice
Ranked #4 on Hacker News with 16 points and 3 comments.
US 12,670,045 B1 was filed on 4 March 2026 and granted on 30 June. The claims are now readable and they are narrow: a stateless sandbox that pauses a code block, ships one tool call to the client, and resumes by replaying from the top. The prior art that bears on that is durable execution, not CodeAct. The people who would know that are exactly the ones the closed prior-art window locked out.
On 30 June 2026 the United States Patent and Trademark Office granted Mistral AI a patent titled "Code implemented tool calls". The application was filed on 4 March 2026. That is 118 days from filing to grant, in a system where the average utility application waits somewhere north of two years .
The number is US 12,670,045 B1 , application 19/557,103, twenty claims, classified at G06F 9/547. The named inventor is Gabriel Vergnaud, of Paris. The assignee is Mistral AI SAS, the company that has spent three years positioning itself as the open-weights alternative to the American labs. Of all of that, the detail worth your attention is the trailing letter.
Start with what it doesn't say, because plenty of people have now told me that Mistral has patented the practice of letting an agent write code to call its tools. It hasn't, and the claims are worth reading before anyone lights anything on fire.
Claim 1 is a method with a specific shape. A server receives a request. An LLM generates a code block that encapsulates the tool calls. The server runs that block in a sandbox. When execution reaches a tool call that has to happen somewhere else, the block pauses , that single pending call is transmitted to a client, the client executes it, the result comes back, execution resumes with the result substituted in for the call, and only the final output is returned to the model.
The dependent claims give away the mechanism, and it is the interesting part. Claim 4: resumption works by "using an evaluation stack that replays the code block from a beginning of the code block". Claim 5: that stack "ensures deterministic execution by capturing and replaying results of non-deterministic operations". Claim 10: those non-deterministic operations are wrapped in a function "configured to store initial values".