Struct Usage 

pub struct Usage {
    pub input_tokens: u64,
    pub output_tokens: u64,
    pub cache_read_tokens: Option<u64>,
    pub cache_creation_tokens: Option<u64>,
    pub reasoning_tokens: Option<u64>,
}

Token accounting parsed from the provider’s terminal usage event.

Fields

input_tokens: u64

Input (prompt) tokens.

output_tokens: u64

Output (completion) tokens.

cache_read_tokens: Option<u64>

Tokens served from the prompt cache. None = this wire/provider does not report the counter; Some(0) = reported as zero (a real signal: no cache hit). ADR-0009 amendment 2026-07-19 — zero-as-N/A rejected.

cache_creation_tokens: Option<u64>

Tokens written to the prompt cache (None on wires that never report writes, e.g. the OpenAI family).

reasoning_tokens: Option<u64>

Reasoning/thinking tokens (None on wires that fold them into output_tokens, e.g. Anthropic).

Implementations

impl Usage

pub fn context_tokens(&self) -> u64

Everything this turn put on the wire and got back: the full prompt (input plus both cache counters) plus the completion.

Both cache counters belong in the total. A cached read and a cache write are prompt tokens that a provider bills differently — they occupy the context window exactly like uncached input, so leaving either out under-reports how full it is.

Trait Implementations

impl AddAssign for Usage

fn add_assign(&mut self, rhs: Self)

Accumulate another turn’s usage field-wise (the engine sums across turns).

impl Clone for Usage

fn clone(&self) -> Usage

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Copy for Usage

impl Debug for Usage

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

Formats the value using the given formatter.

impl Default for Usage

fn default() -> Usage

Returns the “default value” for a type.

impl<'de> Deserialize<'de> for Usage

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

where __D: Deserializer<'de>,

Deserialize this value from the given Serde deserializer.

impl Eq for Usage

impl PartialEq for Usage

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

Equality operator ==.

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

Inequality operator !=.

impl Serialize for Usage

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 Usage