# Per-function settings (llmcpp)

**Per-function settings** override generation policy for a single annotated definition. They are written inside the `__llm__` modifier rather than changing every generated function in a compilation.

```cpp
__llm__(max_attempts(2), timeout(120))
int twice(int value)
{
    Return twice value.
}
```

Environment variables provide defaults, command-line settings override those defaults, and function settings override the corresponding driver settings. This lets a particular function use a different model, agent, prompt file, cache policy, or generation budget.

Numeric budgets require positive integer literals, with documented exceptions such as zero cache lifetime meaning no expiry. File-backed settings resolve paths from the compiler's working directory. Their contents can affect [[llmcpp-cache-identity|cache identity]], so changing instructions or references can require generation again.

Some combinations are rejected, including `no_cache` with an explicit cache key. Settings also have distinct meanings: `context` attaches reference material, while `append_prompt` adds instructions. The resolved settings are supplied to the generation session, allowing the compiler and agent to agree on the policy for that target.