Enum OpenAiApiFormat 

pub enum OpenAiApiFormat {
    Auto,
    Completions,
    Responses,
}

Which OpenAI-family API format to use when talking to the LLM.

• Auto (default): Auto-detects from the model name. Codex models use Responses API, everything else uses Chat Completions.
• Completions: Forces the Chat Completions API (/v1/chat/completions)
• Responses: Forces the Responses API (/v1/responses)

Most OpenAI models (GPT-4o, GPT-4.1, GPT-5, o1, etc.) support both APIs. Codex models (codex-*, *-codex) are Responses API only. OpenAI recommends the Responses API for new projects (better caching, reasoning).

Can be set at the model_settings level in agent definitions:

[model_settings]
model = "codex-mini-latest"
api_format = "responses"  # or "completions" or "auto"

Variants

Auto

Auto-detect based on model name (codex models → Responses, everything else → Completions)

Completions

Chat Completions API (/v1/chat/completions)

Responses

Responses API (/v1/responses) — required for Codex models, recommended for new projects

Implementations

impl OpenAiApiFormat

pub fn resolve(&self, model: &str) -> ResolvedOpenAiApiFormat

Resolve the effective format given a model name. When Auto, inspects the model name to decide.

Trait Implementations

impl Clone for OpenAiApiFormat

fn clone(&self) -> OpenAiApiFormat

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for OpenAiApiFormat

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Default for OpenAiApiFormat

fn default() -> OpenAiApiFormat

Returns the “default value” for a type.

impl<'de> Deserialize<'de> for OpenAiApiFormat

fn deserialize<__D>(__deserializer: __D) -> Result<Self, __D::Error>

where __D: Deserializer<'de>,

Deserialize this value from the given Serde deserializer.

impl JsonSchema for OpenAiApiFormat

fn schema_name() -> Cow<'static, str>

The name of the generated JSON Schema.

fn schema_id() -> Cow<'static, str>

Returns a string that uniquely identifies the schema produced by this type.

fn json_schema(generator: &mut SchemaGenerator) -> Schema

Generates a JSON Schema for this type.

fn inline_schema() -> bool

Whether JSON Schemas generated for this type should be included directly in parent schemas, rather than being re-used where possible using the $ref keyword.

impl PartialEq for OpenAiApiFormat

fn eq(&self, other: &OpenAiApiFormat) -> bool

Tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl Serialize for OpenAiApiFormat

fn serialize<__S>(&self, __serializer: __S) -> Result<__S::Ok, __S::Error>

where __S: Serializer,

Serialize this value into the given Serde serializer.

impl StructuralPartialEq for OpenAiApiFormat