Silent Model Updates Are Breaking Your EU AI Act Risk Assessment

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OpenAI updated GPT-4-turbo's training data cutoff from April 2023 to December 2023 without issuing a new model ID. Anthropic regularly updates Claude models within a named version — `claude-sonnet-4-6` today is not bit-for-bit identical to `claude-sonnet-4-6` three months ago. Google has retrained Gemini models while keeping the same API endpoint identifiers.

If your production AI system is built on any of these, your EU AI Act Article 9 risk assessment is covering a system that may no longer exist in the form you assessed.

## The Article 9 gap

EU AI Act Article 9 requires providers of high-risk AI systems to maintain a risk management system that is "a continuous iterative process run throughout the entire lifecycle." Article 9(2)(c) requires "examination, testing and validation procedures" — procedures that are implicitly tied to the AI system as it exists at test time.

Article 17, which governs Quality Management Systems, requires documentation of "the AI system design, development process and testing methodology." A QMS that references a risk assessment performed against model version X is not a valid QMS if version X is no longer what runs in production.

Neither article defines what constitutes a "model version change" at the foundation model level. Article 83 addresses substantial modifications at the system level, but is silent on what happens when a third-party foundation model component updates beneath your system. Recital 66 suggests that the deployer who builds on a third-party model takes on responsibility for its behavior — including changes introduced by the upstream provider.

The compliance obligation falls on you, not the provider.

## What providers expose

Most providers return the following in an API response:

- The model ID you requested (e.g., `gpt-4o`, `claude-sonnet-4-6`)
- A response ID scoped to the request, not the model version
- Token usage counts
- Finish reason

What they rarely expose:

- The specific training checkpoint that pr