Enum StreamChunk 

pub enum StreamChunk {
    Token(String),
    Done,
    Error(String),
}

One piece of a streamed model reply, delivered in order over the Receiver that ModelAdapter::stream returns.

This enum is a frozen contract — every adapter (local, echo, cloud, and anything built later) emits exactly these three variants, and every consumer (the kopitiam ai chat loop today, a ratatui pane tomorrow) matches on exactly these three. Don’t add or rename variants without treating it as the breaking change it is.

A well-formed stream is: zero or more StreamChunk::Token, then one terminal chunk — StreamChunk::Done on success or StreamChunk::Error on failure — then nothing (the sender drops, closing the channel).

Variants

Token(String)

One decoded increment of the reply — in practice one model token’s text (e.g. "Hel", "lo", " world"). Concatenating every Token in arrival order rebuilds the full reply.

Honest caveat, inherited from kopitiam_runtime::generate’s token-by-token decode: a single multi-byte Unicode character that a tokenizer splits across two tokens can arrive split across two Tokens. That’s the normal, accepted tradeoff of any streaming LLM UI — the blocking complete() path decodes the whole sequence together and never splits — so a caller that needs character-perfect text mid-stream should buffer, but a chat UI that just appends each Token to a pane is fine.

Done

The stream finished cleanly. Always the last chunk on a successful run; nothing follows it. Its arrival is how a consumer knows the reply is complete (as opposed to the model still thinking).

Error(String)

Generation failed partway. Always the last chunk on a failed run; carries a human-readable reason (rendered from the underlying anyhow error). Nothing follows it. Any Tokens that arrived before it are still valid partial output — the failure just means the reply is truncated, not that what came before is wrong.

Trait Implementations

impl Clone for StreamChunk

fn clone(&self) -> StreamChunk

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for StreamChunk

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

Formats the value using the given formatter.

impl Eq for StreamChunk

impl PartialEq for StreamChunk

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

Equality operator ==.

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

Inequality operator !=.

impl StructuralPartialEq for StreamChunk