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Skeleton for the Coding Agent. (#1)

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Reviewed-on: #1
Co-authored-by: Drew Galbraith <drew@tiramisu.one>
Co-committed-by: Drew Galbraith <drew@tiramisu.one>
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Drew 2026-02-24 19:50:38 +00:00 • committed by Drew
parent 42e3ddacc2
commit 5d213b43d3
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443
src/provider/claude.rs Normal file
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use futures::{SinkExt, Stream, StreamExt};
use reqwest::Client;
use serde::Deserialize;
use crate::core::types::{ConversationMessage, StreamEvent};
use super::ModelProvider;
/// Errors that can occur when constructing or using a [`ClaudeProvider`].
#[derive(Debug, thiserror::Error)]
pub enum ClaudeProviderError {
/// The `ANTHROPIC_API_KEY` environment variable is not set.
#[error("ANTHROPIC_API_KEY environment variable not set")]
MissingApiKey,
/// An HTTP-level error from the reqwest client.
#[error("HTTP request failed: {0}")]
Http(#[from] reqwest::Error),
}
/// [`ModelProvider`] implementation that streams responses from the Anthropic Messages API.
///
/// Calls `POST /v1/messages` with `"stream": true` and parses the resulting
/// [Server-Sent Events][sse] stream into [`StreamEvent`]s.
///
/// # Authentication
///
/// Reads the API key from the `ANTHROPIC_API_KEY` environment variable.
/// See the [Anthropic authentication docs][auth] for how to obtain a key.
///
/// # API version
///
/// Sends the `anthropic-version: 2023-06-01` header on every request, which is
/// the stable baseline version required by the API. See the
/// [versioning docs][versioning] for details on how Anthropic handles API versions.
///
/// [sse]: https://html.spec.whatwg.org/multipage/server-sent-events.html
/// [auth]: https://docs.anthropic.com/en/api/getting-started#authentication
/// [versioning]: https://docs.anthropic.com/en/api/versioning
pub struct ClaudeProvider {
api_key: String,
client: Client,
model: String,
}
impl ClaudeProvider {
/// Create a `ClaudeProvider` reading `ANTHROPIC_API_KEY` from the environment.
/// The caller must supply the model ID (e.g. `"claude-opus-4-6"`).
///
/// See the [models overview][models] for available model IDs.
///
/// [models]: https://docs.anthropic.com/en/docs/about-claude/models/overview
pub fn from_env(model: impl Into<String>) -> Result<Self, ClaudeProviderError> {
let api_key =
std::env::var("ANTHROPIC_API_KEY").map_err(|_| ClaudeProviderError::MissingApiKey)?;
Ok(Self {
api_key,
client: Client::new(),
model: model.into(),
})
}
}
impl ModelProvider for ClaudeProvider {
fn stream<'a>(
&'a self,
messages: &'a [ConversationMessage],
) -> impl Stream<Item = StreamEvent> + Send + 'a {
let (mut tx, rx) = futures::channel::mpsc::channel(32);
let client = self.client.clone();
let api_key = self.api_key.clone();
let model = self.model.clone();
let messages = messages.to_vec();
tokio::spawn(async move {
run_stream(client, api_key, model, messages, &mut tx).await;
});
rx
}
}
/// POST to `/v1/messages` with `stream: true`, then parse the SSE response into
/// [`StreamEvent`]s and forward them to `tx`.
///
/// # Request shape
///
/// ```json
/// {
/// "model": "<model-id>",
/// "max_tokens": 8192,
/// "stream": true,
/// "messages": [{ "role": "user"|"assistant", "content": "<text>" }, ...]
/// }
/// ```
///
/// See the [Messages API reference][messages-api] for the full schema.
///
/// # SSE stream lifecycle
///
/// With streaming enabled the API sends a sequence of
/// [Server-Sent Events][sse] separated by blank lines (`\n\n`). Each event
/// has an `event:` line naming its type and a `data:` line containing a JSON
/// object. The full event sequence for a successful turn is:
///
/// ```text
/// event: message_start -> InputTokens(n)
/// event: content_block_start -> (ignored -- signals a new content block)
/// event: ping -> (ignored -- keepalive)
/// event: content_block_delta -> TextDelta(chunk) (repeated)
/// event: content_block_stop -> (ignored -- signals end of content block)
/// event: message_delta -> OutputTokens(n)
/// event: message_stop -> Done
/// ```
///
/// We stop reading as soon as `Done` is emitted; any bytes arriving after
/// `message_stop` are discarded.
///
/// See the [streaming reference][streaming] for the authoritative description
/// of each event type and its JSON payload.
///
/// [messages-api]: https://docs.anthropic.com/en/api/messages
/// [streaming]: https://docs.anthropic.com/en/api/messages-streaming
/// [sse]: https://html.spec.whatwg.org/multipage/server-sent-events.html
async fn run_stream(
client: Client,
api_key: String,
model: String,
messages: Vec<ConversationMessage>,
tx: &mut futures::channel::mpsc::Sender<StreamEvent>,
) {
let body = serde_json::json!({
"model": model,
"max_tokens": 8192,
"stream": true,
"messages": messages,
});
let response = match client
.post("https://api.anthropic.com/v1/messages")
.header("x-api-key", &api_key)
.header("anthropic-version", "2023-06-01")
.header("content-type", "application/json")
.json(&body)
.send()
.await
{
Ok(r) => r,
Err(e) => {
let _ = tx.send(StreamEvent::Error(e.to_string())).await;
return;
}
};
if !response.status().is_success() {
let status = response.status();
let body_text = match response.text().await {
Ok(t) => t,
Err(e) => format!("(failed to read error body: {e})"),
};
let _ = tx
.send(StreamEvent::Error(format!("HTTP {status}: {body_text}")))
.await;
return;
}
let mut stream = response.bytes_stream();
let mut buffer: Vec<u8> = Vec::new();
while let Some(chunk) = stream.next().await {
match chunk {
Err(e) => {
let _ = tx.send(StreamEvent::Error(e.to_string())).await;
return;
}
Ok(bytes) => {
buffer.extend_from_slice(&bytes);
// Drain complete SSE events (delimited by blank lines).
loop {
match find_double_newline(&buffer) {
None => break,
Some(pos) => {
let event_bytes: Vec<u8> = buffer.drain(..pos + 2).collect();
let event_str = String::from_utf8_lossy(&event_bytes);
if let Some(event) = parse_sse_event(&event_str) {
let is_done = matches!(event, StreamEvent::Done);
let _ = tx.send(event).await;
if is_done {
return;
}
}
}
}
}
}
}
}
let _ = tx.send(StreamEvent::Done).await;
}
/// Return the byte offset of the first `\n\n` in `buf`, or `None`.
///
/// SSE uses a blank line (two consecutive newlines) as the event boundary.
/// See [Section 9.2.6 of the SSE spec][sse-dispatch].
///
/// [sse-dispatch]: https://html.spec.whatwg.org/multipage/server-sent-events.html#event-stream-interpretation
fn find_double_newline(buf: &[u8]) -> Option<usize> {
buf.windows(2).position(|w| w == b"\n\n")
}
// -- SSE JSON types -----------------------------------------------------------
//
// These structs mirror the subset of the Anthropic SSE payload we actually
// consume. Unknown fields are silently ignored by serde. Full schemas are
// documented in the [streaming reference][streaming].
//
// [streaming]: https://docs.anthropic.com/en/api/messages-streaming
/// Top-level SSE data object. The `type` field selects which other fields
/// are present; we use `Option` for all of them so a single struct covers
/// every event type without needing an enum.
#[derive(Deserialize, Debug)]
struct SseEvent {
#[serde(rename = "type")]
event_type: String,
/// Present on `content_block_delta` events.
delta: Option<SseDelta>,
/// Present on `message_start` events; carries initial token usage.
message: Option<SseMessageStart>,
/// Present on `message_delta` events; carries final output token count.
usage: Option<SseUsage>,
}
/// The `delta` object inside a `content_block_delta` event.
///
/// `type` is `"text_delta"` for plain text chunks; other delta types
/// (e.g. `"input_json_delta"` for tool-use blocks) are not yet handled.
#[derive(Deserialize, Debug)]
struct SseDelta {
#[serde(rename = "type")]
delta_type: Option<String>,
/// The text chunk; present when `delta_type == "text_delta"`.
text: Option<String>,
}
/// The `message` object inside a `message_start` event.
#[derive(Deserialize, Debug)]
struct SseMessageStart {
usage: Option<SseUsage>,
}
/// Token counts reported at the start and end of a turn.
///
/// `input_tokens` is set in the `message_start` event;
/// `output_tokens` is set in the `message_delta` event.
/// Both fields are `Option` so the same struct works for both events.
#[derive(Deserialize, Debug)]
struct SseUsage {
input_tokens: Option<u32>,
output_tokens: Option<u32>,
}
/// Parse a single SSE event string into a [`StreamEvent`], returning `None` for
/// event types we don't care about (`ping`, `content_block_start`,
/// `content_block_stop`).
///
/// # SSE format
///
/// Each event is a block of `field: value` lines. We only read the `data:`
/// field; the `event:` line is redundant with the `type` key inside the JSON
/// payload so we ignore it. See the [SSE spec][sse-fields] for the full field
/// grammar.
///
/// # Mapping to [`StreamEvent`]
///
/// | API event type | JSON path | Emits |
/// |----------------------|------------------------------------|------------------------------|
/// | `message_start` | `.message.usage.input_tokens` | `InputTokens(n)` |
/// | `content_block_delta`| `.delta.type == "text_delta"` | `TextDelta(chunk)` |
/// | `message_delta` | `.usage.output_tokens` | `OutputTokens(n)` |
/// | `message_stop` | n/a | `Done` |
/// | everything else | n/a | `None` (caller skips) |
///
/// [sse-fields]: https://html.spec.whatwg.org/multipage/server-sent-events.html#parsing-an-event-stream
fn parse_sse_event(event_str: &str) -> Option<StreamEvent> {
// SSE events may have multiple fields; we only need `data:`.
let data = event_str
.lines()
.find_map(|line| line.strip_prefix("data: "))?;
let event: SseEvent = serde_json::from_str(data).ok()?;
match event.event_type.as_str() {
"message_start" => event
.message
.and_then(|m| m.usage)
.and_then(|u| u.input_tokens)
.map(StreamEvent::InputTokens),
"content_block_delta" => {
let delta = event.delta?;
if delta.delta_type.as_deref() == Some("text_delta") {
delta.text.map(StreamEvent::TextDelta)
} else {
None
}
}
// usage lives at the top level of message_delta, not inside delta.
"message_delta" => event
.usage
.and_then(|u| u.output_tokens)
.map(StreamEvent::OutputTokens),
"message_stop" => Some(StreamEvent::Done),
// error, ping, content_block_start, content_block_stop -- ignored or
// handled by the caller.
_ => None,
}
}
// -- Tests --------------------------------------------------------------------
#[cfg(test)]
mod tests {
use super::*;
use crate::core::types::Role;
/// A minimal but complete Anthropic SSE fixture.
const SSE_FIXTURE: &str = concat!(
"event: message_start\n",
"data: {\"type\":\"message_start\",\"message\":{\"id\":\"msg_123\",\"type\":\"message\",",
"\"role\":\"assistant\",\"content\":[],\"model\":\"claude-opus-4-6\",",
"\"stop_reason\":null,\"stop_sequence\":null,",
"\"usage\":{\"input_tokens\":10,\"cache_creation_input_tokens\":0,",
"\"cache_read_input_tokens\":0,\"output_tokens\":1}}}\n",
"\n",
"event: content_block_start\n",
"data: {\"type\":\"content_block_start\",\"index\":0,",
"\"content_block\":{\"type\":\"text\",\"text\":\"\"}}\n",
"\n",
"event: ping\n",
"data: {\"type\":\"ping\"}\n",
"\n",
"event: content_block_delta\n",
"data: {\"type\":\"content_block_delta\",\"index\":0,",
"\"delta\":{\"type\":\"text_delta\",\"text\":\"Hello\"}}\n",
"\n",
"event: content_block_delta\n",
"data: {\"type\":\"content_block_delta\",\"index\":0,",
"\"delta\":{\"type\":\"text_delta\",\"text\":\", world!\"}}\n",
"\n",
"event: content_block_stop\n",
"data: {\"type\":\"content_block_stop\",\"index\":0}\n",
"\n",
"event: message_delta\n",
"data: {\"type\":\"message_delta\",\"delta\":{\"stop_reason\":\"end_turn\",",
"\"stop_sequence\":null},\"usage\":{\"output_tokens\":5}}\n",
"\n",
"event: message_stop\n",
"data: {\"type\":\"message_stop\"}\n",
"\n",
);
#[test]
fn test_parse_sse_events_from_fixture() {
let events: Vec<StreamEvent> = SSE_FIXTURE
.split("\n\n")
.filter(|s| !s.trim().is_empty())
.filter_map(parse_sse_event)
.collect();
// content_block_start, ping, content_block_stop -> None (filtered out)
assert_eq!(events.len(), 5);
assert!(matches!(events[0], StreamEvent::InputTokens(10)));
assert!(matches!(&events[1], StreamEvent::TextDelta(s) if s == "Hello"));
assert!(matches!(&events[2], StreamEvent::TextDelta(s) if s == ", world!"));
assert!(matches!(events[3], StreamEvent::OutputTokens(5)));
assert!(matches!(events[4], StreamEvent::Done));
}
#[test]
fn test_parse_message_stop_yields_done() {
let event_str = "event: message_stop\ndata: {\"type\":\"message_stop\"}\n";
assert!(matches!(
parse_sse_event(event_str),
Some(StreamEvent::Done)
));
}
#[test]
fn test_parse_ping_yields_none() {
let event_str = "event: ping\ndata: {\"type\":\"ping\"}\n";
assert!(parse_sse_event(event_str).is_none());
}
#[test]
fn test_parse_content_block_start_yields_none() {
let event_str = concat!(
"event: content_block_start\n",
"data: {\"type\":\"content_block_start\",\"index\":0,",
"\"content_block\":{\"type\":\"text\",\"text\":\"\"}}\n",
);
assert!(parse_sse_event(event_str).is_none());
}
#[test]
fn test_messages_serialize_to_anthropic_format() {
let messages = vec![
ConversationMessage {
role: Role::User,
content: "Hello".to_string(),
},
ConversationMessage {
role: Role::Assistant,
content: "Hi there!".to_string(),
},
];
let json = serde_json::json!({
"model": "claude-opus-4-6",
"max_tokens": 8192,
"stream": true,
"messages": messages,
});
assert_eq!(json["messages"][0]["role"], "user");
assert_eq!(json["messages"][0]["content"], "Hello");
assert_eq!(json["messages"][1]["role"], "assistant");
assert_eq!(json["messages"][1]["content"], "Hi there!");
assert_eq!(json["stream"], true);
assert!(json["max_tokens"].as_u64().unwrap() > 0);
}
#[test]
fn test_find_double_newline() {
assert_eq!(find_double_newline(b"abc\n\ndef"), Some(3));
assert_eq!(find_double_newline(b"abc\ndef"), None);
assert_eq!(find_double_newline(b"\n\n"), Some(0));
assert_eq!(find_double_newline(b""), None);
}
}

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src/provider/mod.rs Normal file
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mod claude;
pub use claude::ClaudeProvider;
use futures::Stream;
use crate::core::types::{ConversationMessage, StreamEvent};
/// Trait for model providers that can stream conversation responses.
///
/// Implementors take a conversation history and return a stream of [`StreamEvent`]s.
/// The trait is provider-agnostic -- no Claude-specific types appear here.
pub trait ModelProvider: Send + Sync {
/// Stream a response from the model given the conversation history.
fn stream<'a>(
&'a self,
messages: &'a [ConversationMessage],
) -> impl Stream<Item = StreamEvent> + Send + 'a;
}