Struct UsageRecord 

pub struct UsageRecord {
    pub turn: usize,
    pub model: String,
    pub prompt_tokens: u64,
    pub completion_tokens: u64,
    pub total_tokens: u64,
    pub cached_tokens: Option<u64>,
    pub timestamp_ms: i64,
    pub cost_usd: Option<f64>,
    pub served_model: Option<String>,
}

One model round-trip’s token accounting, with the context a bare Usage lacks: which turn it was and which model served it (D9 “model provenance” — obligation 6’s “served-model provenance” row). Deliberately flat/typed (not a formatted string) so it survives a save/load round trip byte-for-byte in the fields that matter, and so a future reader (a doctor/inspect stats command, a cost dashboard) can aggregate it without re-parsing text.

Fields

turn: usize

0-based index of the model round-trip this record covers (one per crate::AgentEvent::TurnCompleted, the same cadence UX-23 already uses).

model: String

The model id that served this turn (Config.model, or the mid-session-switched model once obligation 10 lands — recorded per-turn rather than once per session so a handoff is visible in the log, not just implied).

prompt_tokens: u64

Input tokens.

completion_tokens: u64

Output tokens.

total_tokens: u64

Total tokens (provider-reported; not always prompt + completion exactly, so kept as its own field rather than derived).

cached_tokens: Option<u64>

Prompt tokens served from the provider’s cache (B7), if reported.

timestamp_ms: i64

Unix-ms wall-clock time the record was created.

cost_usd: Option<f64>

BP-7 (catalog §4a “Per-turn cost/usage accounting” — the COST half the row’s semantics name alongside tokens): this round-trip’s dollar cost at the model’s resolved crate::pricing::ModelPrice. None when this build cannot price the model — never a guess, and never zero standing in for “unknown”.

served_model: Option<String>

BP-13 (D9 “Model-served-vs-requested provenance”): the model the PROVIDER reported as having produced the response, when it reported one at all. Self::model above is what was REQUESTED; these two can genuinely differ (a gateway resolving a floating name to a dated snapshot, a routed tier, a fallback hop), and a record that carries only the request can never show it. None means the provider said nothing — never “they matched”.

Implementations

impl UsageRecord

pub fn from_usage( turn: usize, model: &str, usage: &Usage, timestamp_ms: i64, ) -> UsageRecord

Build a record from a provider Usage plus the per-turn context a bare Usage doesn’t carry.

pub fn priced(self, price: Option<ModelPrice>) -> UsageRecord

BP-7: the same record with cost_usd filled in from price, or unchanged when the model has no resolvable price.

pub fn with_served_model(self, served: Option<String>) -> UsageRecord

BP-13: attach the provider-reported serving model. None leaves the record saying nothing about it, which is the honest reading when the response carried no model field.

pub fn diverged(&self) -> bool

BP-13: whether the model that answered differs from the one asked for. false when the provider reported nothing — an unknown is not a divergence.

Trait Implementations

impl Clone for UsageRecord

fn clone(&self) -> UsageRecord

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for UsageRecord

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

Formats the value using the given formatter.

impl Default for UsageRecord

fn default() -> UsageRecord

Returns the “default value” for a type.

impl<'de> Deserialize<'de> for UsageRecord

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

where __D: Deserializer<'de>,

Deserialize this value from the given Serde deserializer.

impl PartialEq for UsageRecord

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

Equality operator ==.

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

Inequality operator !=.

impl Serialize for UsageRecord

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 UsageRecord