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//! Relax a forced tool choice on routes whose catalog row rejects forcing.
thread_local! {
static FORCED_TOOL_CHOICE_WARN_ONCE: std::cell::RefCell<std::collections::HashSet<String>> =
std::cell::RefCell::new(std::collections::HashSet::new());
}
/// Lower a forced tool choice (`required` / `any` / a named tool) to `auto`
/// on routes whose catalog row says forcing is rejected (Fable 5.1, Opus 5.5:
/// `tool_choice: type "tool" and "any" are not supported for this model`).
///
/// Failing the call would turn a recoverable nudge into a dead turn, and
/// sending it is a guaranteed 400. `auto` is the provider's documented
/// replacement: the caller's prompt still asks for the tool, and loops that
/// forced a call already handle a turn without one. A
/// `disable_parallel_tool_use` flag on an object choice is kept.
pub(super) fn relax_rejected_forced_tool_choice(
choice: serde_json::Value,
caps: &crate::llm::capabilities::Capabilities,
model: &str,
) -> serde_json::Value {
if !crate::llm::providers::anthropic::tool_choice_forces_tool_use(&choice)
|| crate::llm::providers::anthropic::forced_tool_choice_allowed(caps)
{
return choice;
}
let first =
FORCED_TOOL_CHOICE_WARN_ONCE.with(|seen| seen.borrow_mut().insert(model.to_string()));
if first {
crate::events::log_warn(
"llm.tool_choice",
&format!(
"model \"{model}\" rejects forced tool choice; sending `tool_choice: \"auto\"` \
instead of {choice}"
),
);
}
match choice.get("disable_parallel_tool_use") {
Some(flag) => serde_json::json!({"type": "auto", "disable_parallel_tool_use": flag}),
None => serde_json::json!("auto"),
}
}