systemprompt-api 0.21.1

Axum-based HTTP server and API gateway for systemprompt.io AI governance infrastructure. Exposes governed agents, MCP, A2A, and admin endpoints with rate limiting and RBAC.
Documentation 
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151

//! Observe-while-forwarding tap that captures an external MCP tool-call result.
//!
//! For an SSE response the tap forwards each chunk untouched while scanning the
//! stream for the JSON-RPC frame matching the request id; for a single JSON
//! response it buffers, parses, and forwards. Either way it finalizes the
//! [`McpAudit`] exactly once, on stream EOF or drop.
//!
//! Copyright (c) systemprompt.io — Business Source License 1.1.
//! See <https://systemprompt.io> for licensing details.

use std::io;
use std::pin::Pin;
use std::sync::{Arc, Mutex};
use std::task::{Context, Poll};

use axum::body::Body;
use axum::http::StatusCode;
use axum::response::Response;
use bytes::Bytes;
use futures_util::{Stream, TryStreamExt};
use serde_json::Value;

use super::super::backend::{ResponseHandler, SSE_KEEPALIVE_INTERVAL, SseKeepaliveStream};
use super::McpAudit;
use super::jsonrpc::{ToolCallOutcome, extract_sse_data, parse_response_frame};

pub(crate) async fn record(
    response: reqwest::Response,
    audit: McpAudit,
) -> Result<Response<Body>, String> {
    let status = StatusCode::from_u16(response.status().as_u16())
        .map_err(|e| format!("Invalid status code: {e}"))?;
    let headers = response.headers().clone();
    let is_sse = ResponseHandler::is_event_stream(&headers);

    if is_sse {
        let accumulator = Arc::new(Mutex::new(SseAccumulator::new(audit.request_id().clone())));
        let stream = response.bytes_stream().map_err(io::Error::other);
        let tapped = McpAuditTapStream {
            inner: stream,
            accumulator,
            audit: Some(audit),
        };
        let body = Body::from_stream(SseKeepaliveStream::new(tapped, SSE_KEEPALIVE_INTERVAL));
        ResponseHandler::assemble(status, &headers, true, body)
    } else {
        let bytes = response.bytes().await.map_err(|e| e.to_string())?;
        let outcome = match std::str::from_utf8(&bytes) {
            Ok(text) => parse_response_frame(text, audit.request_id()),
            Err(e) => {
                tracing::warn!(error = %e, "external MCP response body was not valid UTF-8; not audited");
                None
            },
        };
        audit.finalize(outcome);
        ResponseHandler::assemble(status, &headers, false, Body::from(bytes))
    }
}

struct SseAccumulator {
    buf: Vec<u8>,
    request_id: Value,
    outcome: Option<ToolCallOutcome>,
}

impl SseAccumulator {
    const fn new(request_id: Value) -> Self {
        Self {
            buf: Vec::new(),
            request_id,
            outcome: None,
        }
    }

    fn push(&mut self, chunk: &[u8]) {
        if self.outcome.is_some() {
            return;
        }
        self.buf.extend_from_slice(chunk);
        while let Some(end) = find_frame_end(&self.buf) {
            let frame: Vec<u8> = self.buf.drain(..end).collect();
            self.consume(&frame);
            if self.outcome.is_some() {
                break;
            }
        }
    }

    fn consume(&mut self, frame: &[u8]) {
        let text = String::from_utf8_lossy(frame);
        if let Some(data) = extract_sse_data(&text) {
            self.outcome = parse_response_frame(&data, &self.request_id);
        }
    }
}

fn find_frame_end(buf: &[u8]) -> Option<usize> {
    buf.windows(2)
        .position(|w| w == b"\n\n")
        .map(|i| i + 2)
        .or_else(|| buf.windows(4).position(|w| w == b"\r\n\r\n").map(|i| i + 4))
}

struct McpAuditTapStream<S> {
    inner: S,
    accumulator: Arc<Mutex<SseAccumulator>>,
    audit: Option<McpAudit>,
}

impl<S> McpAuditTapStream<S> {
    fn finish(&mut self) {
        if let Some(audit) = self.audit.take() {
            let outcome = self
                .accumulator
                .lock()
                .ok()
                .and_then(|mut acc| acc.outcome.take());
            audit.finalize(outcome);
        }
    }
}

impl<S> Stream for McpAuditTapStream<S>
where
    S: Stream<Item = Result<Bytes, io::Error>> + Unpin,
{
    type Item = Result<Bytes, io::Error>;

    fn poll_next(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Option<Self::Item>> {
        match Pin::new(&mut self.inner).poll_next(cx) {
            Poll::Ready(Some(Ok(bytes))) => {
                if let Ok(mut acc) = self.accumulator.lock() {
                    acc.push(&bytes);
                }
                Poll::Ready(Some(Ok(bytes)))
            },
            Poll::Ready(Some(Err(e))) => Poll::Ready(Some(Err(e))),
            Poll::Ready(None) => {
                self.finish();
                Poll::Ready(None)
            },
            Poll::Pending => Poll::Pending,
        }
    }
}

impl<S> Drop for McpAuditTapStream<S> {
    fn drop(&mut self) {
        self.finish();
    }
}