refactor(workspace): enforce layered crate boundaries

crates/aether-gateway/execution/src/lib.rs

@@ -0,0 +1,10 @@
+//! Gateway execution request-lifecycle components.
+//!
+//! This crate starts with transport-independent stream framing and bounded
+//! execution limits. Planner, executor, and response-finalization adapters can
+//! migrate behind this boundary without making the binary their owner.
+
+mod limits;
+pub mod stream;
+
+pub use limits::{MAX_ERROR_BODY_BYTES, MAX_STREAM_PREFETCH_BYTES, MAX_STREAM_PREFETCH_FRAMES};

crates/aether-gateway/execution/src/limits.rs

@@ -0,0 +1,3 @@
+pub const MAX_ERROR_BODY_BYTES: usize = 16_384;
+pub const MAX_STREAM_PREFETCH_FRAMES: usize = 5;
+pub const MAX_STREAM_PREFETCH_BYTES: usize = 16_384;

crates/aether-gateway/execution/src/stream/mod.rs

@@ -0,0 +1,5 @@
+//! Execution stream protocol codecs.
+
+mod ndjson;
+
+pub use ndjson::{decode_stream_frame_ndjson, encode_stream_frame_ndjson};

crates/aether-gateway/execution/src/stream/ndjson.rs

@@ -0,0 +1,39 @@
+use std::io::Error as IoError;
+
+use aether_contracts::StreamFrame;
+use bytes::Bytes;
+
+pub fn encode_stream_frame_ndjson(frame: &StreamFrame) -> Result<Bytes, IoError> {
+    let mut raw = serde_json::to_vec(frame).map_err(|err| IoError::other(err.to_string()))?;
+    raw.push(b'\n');
+    Ok(Bytes::from(raw))
+}
+
+pub fn decode_stream_frame_ndjson(line: &[u8]) -> Result<StreamFrame, IoError> {
+    serde_json::from_slice(line).map_err(|err| IoError::other(err.to_string()))
+}
+
+#[cfg(test)]
+mod tests {
+    use std::collections::BTreeMap;
+
+    use aether_contracts::{StreamFramePayload, StreamFrameType};
+
+    use super::{decode_stream_frame_ndjson, encode_stream_frame_ndjson};
+
+    #[test]
+    fn ndjson_round_trip_preserves_frame() {
+        let frame = aether_contracts::StreamFrame {
+            frame_type: StreamFrameType::Headers,
+            payload: StreamFramePayload::Headers {
+                status_code: 200,
+                headers: BTreeMap::from([("content-type".into(), "text/event-stream".into())]),
+            },
+        };
+
+        let raw = encode_stream_frame_ndjson(&frame).expect("frame should encode");
+        let decoded =
+            decode_stream_frame_ndjson(raw.trim_ascii_end()).expect("frame should decode");
+        assert_eq!(decoded, frame);
+    }
+}