fix(http): separate transport and protocol limits

crates/wip-client/tests/adapter.rs

@@ -145,16 +145,37 @@ fn valid_error_envelope_is_authoritative_and_status_mismatch_is_diagnostic() {
 }
 
 #[test]
-fn non_success_without_valid_envelope_remains_transport_failure() {
+fn resource_envelope_on_413_uses_code_and_records_canonical_422_mismatch() {
     let (mut client, session) = setup();
     let request = client.refresh_observed(&session, "/item", 0).unwrap();
-    let error = client
+    let error = ProtocolError {
-        .complete(
+        code: ProtocolErrorCode::ResourceLimitExceeded,
-            request.id,
+        message: "logical observation limit exceeded".into(),
-            response(StatusCode::BAD_GATEWAY, b"gateway html"),
+    };
-        )
+    let mut encoded =
-        .unwrap_err();
+        encode_protocol_error_response(ProtocolInteraction::Observe, &error, limits()).unwrap();
-    assert_eq!(error.kind, ClientErrorKind::Transport);
+    *encoded.status_mut() = StatusCode::PAYLOAD_TOO_LARGE;
+
+    assert_eq!(
+        client.complete(request.id, encoded).unwrap(),
+        Completion::ProtocolFailure(error)
+    );
+    assert_eq!(
+        client.diagnostics(&session).unwrap().back().unwrap().kind,
+        DiagnosticKind::HttpStatusMismatch
+    );
+}
+
+#[test]
+fn non_success_without_valid_envelope_remains_transport_failure() {
+    for status in [StatusCode::BAD_GATEWAY, StatusCode::PAYLOAD_TOO_LARGE] {
+        let (mut client, session) = setup();
+        let request = client.refresh_observed(&session, "/item", 0).unwrap();
+        let error = client
+            .complete(request.id, response(status, b"infrastructure failure"))
+            .unwrap_err();
+        assert_eq!(error.kind, ClientErrorKind::Transport);
+    }
 }
 
 #[test]
@@ -250,3 +271,80 @@ fn malformed_call_success_after_dispatch_is_outcome_unknown_and_stales_object()
     );
     assert_eq!(client.in_flight_len(), 0);
 }
+
+#[test]
+fn plain_413_after_call_dispatch_is_unknown_transport_outcome() {
+    let (mut client, session) = setup();
+    let observation = client.refresh_observed(&session, "/item", 0).unwrap();
+    client
+        .complete(
+            observation.id,
+            encode_observe_response(
+                &ObserveRequest {
+                    path: "/item".into(),
+                    depth: 0,
+                },
+                &ObjectObservation {
+                    object: object(),
+                    children: None,
+                },
+                limits(),
+            )
+            .unwrap(),
+        )
+        .unwrap();
+    let interface = client.prepare_interface(&session, "math").unwrap();
+    client
+        .complete(
+            interface.id,
+            encode_fetch_interface_response(
+                &FetchInterfaceRequest {
+                    interface: "math".into(),
+                },
+                &FetchInterfaceResponse {
+                    interface: "math".into(),
+                    descriptor: descriptor(INTERFACE_FORMAT_V1),
+                    validator: None,
+                },
+                limits(),
+            )
+            .unwrap(),
+        )
+        .unwrap();
+    let call = client
+        .prepare_call(
+            &session,
+            "/item",
+            "math",
+            "calculate",
+            BTreeMap::from([("value".into(), Value::Integer(2))]),
+        )
+        .unwrap();
+    client.mark_dispatched(call.id).unwrap();
+
+    let completion = client
+        .complete(
+            call.id,
+            Response::builder()
+                .status(StatusCode::PAYLOAD_TOO_LARGE)
+                .body(Vec::<u8>::new())
+                .unwrap(),
+        )
+        .unwrap();
+    assert!(matches!(
+        completion,
+        Completion::Call(record)
+            if matches!(
+                &record.outcome,
+                CallOutcome::Unknown {
+                    reason: OutcomeUnknownReason::ResponseDecode,
+                    failure: Some(failure),
+                } if failure.kind == ClientErrorKind::Transport
+            )
+    ));
+    assert_eq!(
+        client.object(&session, "/item").unwrap().state,
+        ObservationState::Stale
+    );
+    assert_eq!(client.in_flight_len(), 0);
+}

crates/wip-fs-server/src/server.rs

@@ -5,15 +5,15 @@ use std::sync::atomic::{AtomicBool, Ordering};
 use std::thread;
 use std::time::{Duration, Instant};
 
+use http::header::ALLOW;
 use http::{Request, Response, StatusCode};
 use wip_host::{ExecutionContext, ObjectProvider};
 use wip_http::{
     BatchRequestKind, BatchResponse, BatchResponseItem, BatchSuccess, CodecError, EncodeHttpError,
-    Endpoint, RequestMetadataError, ResourceLimitKind, Route, decode_batch_request,
+    Endpoint, RequestMetadataError, Route, decode_batch_request, decode_call_operation_metadata,
-    decode_call_operation_metadata, decode_fetch_interface_request, decode_observe_request,
+    decode_fetch_interface_request, decode_observe_request, encode_batch_error_response,
-    encode_batch_error_response, encode_batch_resource_limit_error_response, encode_batch_response,
+    encode_batch_response, encode_call_operation_response, encode_fetch_interface_response,
-    encode_call_operation_response, encode_fetch_interface_response, encode_observe_response,
+    encode_observe_response, encode_protocol_error_response, validate_http_request,
-    encode_protocol_error_response, encode_resource_limit_error_response, validate_http_request,
 };
 use wip_protocol::{ProtocolError, ProtocolErrorCode, ProtocolInteraction};
 
@@ -68,20 +68,25 @@ impl WipFsServer {
         request: Request<Vec<u8>>,
         deadline: Instant,
     ) -> Response<Vec<u8>> {
-        let Some(route) = self.route(request.uri().path()) else {
+        let Some(route) = self.route(request.uri()) else {
             return empty_response(StatusCode::NOT_FOUND);
         };
         if let Err(error) = validate_http_request(&self.endpoint, route, &request) {
-            return self.metadata_error(route, error);
+            return self.metadata_error(error);
         }
         let context = ExecutionContext::new()
             .with_deadline(deadline)
             .with_resource_budget(u64::from(self.config.limits.max_observation_nodes));
-        match route {
+        let response = match route {
             Route::Observe => self.observe(request.body(), &context),
             Route::FetchInterface => self.fetch_interface(request.body()),
             Route::CallOperation => self.call_operation(request.body(), &context),
             Route::Batch => self.batch(request.body(), &context),
+        };
+        if Instant::now() >= deadline {
+            empty_response(StatusCode::GATEWAY_TIMEOUT)
+        } else {
+            response
         }
     }
 
@@ -106,7 +111,10 @@ impl WipFsServer {
         })
     }
 
-    fn route(&self, path: &str) -> Option<Route> {
+    fn route(&self, uri: &http::Uri) -> Option<Route> {
+        if uri.query().is_some() {
+            return None;
+        }
         [
             Route::Observe,
             Route::FetchInterface,
@@ -114,7 +122,7 @@ impl WipFsServer {
             Route::Batch,
         ]
         .into_iter()
-        .find(|route| self.endpoint.route(*route).path() == path)
+        .find(|route| self.endpoint.route(*route).path() == uri.path())
     }
 
     fn observe(&self, body: &[u8], context: &ExecutionContext) -> Response<Vec<u8>> {
@@ -127,7 +135,7 @@ impl WipFsServer {
                 .unwrap_or_else(|error| {
                     self.read_encode_error(ProtocolInteraction::Observe, error)
                 }),
-            Err(error) => self.protocol_error(ProtocolInteraction::Observe, &error, None),
+            Err(error) => self.protocol_error(ProtocolInteraction::Observe, &error),
         }
     }
 
@@ -143,7 +151,7 @@ impl WipFsServer {
                         self.read_encode_error(ProtocolInteraction::FetchInterface, error)
                     })
             }
-            Err(error) => self.protocol_error(ProtocolInteraction::FetchInterface, &error, None),
+            Err(error) => self.protocol_error(ProtocolInteraction::FetchInterface, &error),
         }
     }
 
@@ -181,7 +189,7 @@ impl WipFsServer {
                         },
                         message: "operation completed without response metadata".into(),
                     };
-                    return self.protocol_error(ProtocolInteraction::CallOperation, &error, None);
+                    return self.protocol_error(ProtocolInteraction::CallOperation, &error);
                 };
                 encode_call_operation_response(
                     &request,
@@ -190,6 +198,12 @@ impl WipFsServer {
                     self.config.limits.wire,
                 )
                 .unwrap_or_else(|encode_error| {
+                    if matches!(
+                        &encode_error,
+                        EncodeHttpError::Codec(codec) if is_transport_limit(codec)
+                    ) {
+                        return empty_response(StatusCode::INTERNAL_SERVER_ERROR);
+                    }
                     if !may_commit {
                         return self
                             .read_encode_error(ProtocolInteraction::CallOperation, encode_error);
@@ -200,10 +214,10 @@ impl WipFsServer {
                         code: ProtocolErrorCode::OperationOutcomeUnknown,
                         message: "operation completed but its response could not be encoded".into(),
                     };
-                    self.protocol_error(ProtocolInteraction::CallOperation, &error, None)
+                    self.protocol_error(ProtocolInteraction::CallOperation, &error)
                 })
             }
-            Err(error) => self.protocol_error(ProtocolInteraction::CallOperation, &error, None),
+            Err(error) => self.protocol_error(ProtocolInteraction::CallOperation, &error),
         }
     }
 
@@ -236,22 +250,20 @@ impl WipFsServer {
         let response = BatchResponse { responses };
         encode_batch_response(&request, &response, self.config.limits.wire).unwrap_or_else(
             |error| match error {
-                EncodeHttpError::Codec(codec) => self.batch_codec_error(codec),
+                EncodeHttpError::Codec(codec) => self.batch_encode_error(&codec),
-                EncodeHttpError::Http(_) => self.batch_top_error(&internal_error(), None),
+                EncodeHttpError::Http(_) => self.batch_top_error(&internal_error()),
             },
         )
     }
 
-    fn metadata_error(&self, route: Route, error: RequestMetadataError) -> Response<Vec<u8>> {
+    fn metadata_error(&self, error: RequestMetadataError) -> Response<Vec<u8>> {
         match error {
-            RequestMetadataError::InvalidRequest(_) => self.protocol_error(
+            RequestMetadataError::NotFound => empty_response(StatusCode::NOT_FOUND),
-                interaction(route),
+            RequestMetadataError::MethodNotAllowed => Response::builder()
-                &ProtocolError {
+                .status(StatusCode::METHOD_NOT_ALLOWED)
-                    code: ProtocolErrorCode::InvalidRequest,
+                .header(ALLOW, "POST")
-                    message: "invalid HTTP request metadata".into(),
+                .body(Vec::new())
-                },
+                .expect("static method response is valid"),
-                None,
-            ),
             RequestMetadataError::UnsupportedMediaType => {
                 empty_response(StatusCode::UNSUPPORTED_MEDIA_TYPE)
             }
@@ -264,8 +276,8 @@ impl WipFsServer {
         interaction: ProtocolInteraction,
         error: CodecError,
     ) -> Response<Vec<u8>> {
-        if let Some(kind) = error.resource_limit_kind() {
+        if is_transport_limit(&error) {
-            self.protocol_error(interaction, &resource_error(), Some(kind))
+            empty_response(StatusCode::PAYLOAD_TOO_LARGE)
         } else {
             self.protocol_error(
                 interaction,
@@ -273,22 +285,18 @@ impl WipFsServer {
                     code: ProtocolErrorCode::InvalidRequest,
                     message: "malformed WIP request".into(),
                 },
-                None,
             )
         }
     }
 
     fn batch_codec_error(&self, error: CodecError) -> Response<Vec<u8>> {
-        if let Some(kind) = error.resource_limit_kind() {
+        if is_transport_limit(&error) {
-            self.batch_top_error(&resource_error(), Some(kind))
+            empty_response(StatusCode::PAYLOAD_TOO_LARGE)
         } else {
-            self.batch_top_error(
+            self.batch_top_error(&ProtocolError {
-                &ProtocolError {
+                code: ProtocolErrorCode::InvalidRequest,
-                    code: ProtocolErrorCode::InvalidRequest,
+                message: "malformed WIP batch request".into(),
-                    message: "malformed WIP batch request".into(),
+            })
-                },
-                None,
-            )
         }
     }
 
@@ -298,10 +306,18 @@ impl WipFsServer {
         error: EncodeHttpError,
     ) -> Response<Vec<u8>> {
         match error {
-            EncodeHttpError::Codec(codec) if codec.resource_limit_kind().is_some() => {
+            EncodeHttpError::Codec(codec) if is_transport_limit(&codec) => {
-                self.protocol_error(interaction, &resource_error(), codec.resource_limit_kind())
+                empty_response(StatusCode::INTERNAL_SERVER_ERROR)
             }
-            _ => self.protocol_error(interaction, &internal_error(), None),
+            _ => self.protocol_error(interaction, &internal_error()),
+        }
+    }
+
+    fn batch_encode_error(&self, error: &CodecError) -> Response<Vec<u8>> {
+        if is_transport_limit(error) {
+            empty_response(StatusCode::INTERNAL_SERVER_ERROR)
+        } else {
+            self.batch_top_error(&internal_error())
         }
     }
 
@@ -309,32 +325,14 @@ impl WipFsServer {
         &self,
         interaction: ProtocolInteraction,
         error: &ProtocolError,
-        resource_kind: Option<ResourceLimitKind>,
     ) -> Response<Vec<u8>> {
-        let encoded = match resource_kind {
+        encode_protocol_error_response(interaction, error, self.config.limits.wire)
-            Some(kind) => encode_resource_limit_error_response(
+            .unwrap_or_else(|_| empty_response(StatusCode::INTERNAL_SERVER_ERROR))
-                interaction,
-                error,
-                kind,
-                self.config.limits.wire,
-            ),
-            None => encode_protocol_error_response(interaction, error, self.config.limits.wire),
-        };
-        encoded.unwrap_or_else(|_| empty_response(StatusCode::INTERNAL_SERVER_ERROR))
     }
 
-    fn batch_top_error(
+    fn batch_top_error(&self, error: &ProtocolError) -> Response<Vec<u8>> {
-        &self,
+        encode_batch_error_response(error, self.config.limits.wire)
-        error: &ProtocolError,
+            .unwrap_or_else(|_| empty_response(StatusCode::INTERNAL_SERVER_ERROR))
-        resource_kind: Option<ResourceLimitKind>,
-    ) -> Response<Vec<u8>> {
-        let encoded = match resource_kind {
-            Some(kind) => {
-                encode_batch_resource_limit_error_response(error, kind, self.config.limits.wire)
-            }
-            None => encode_batch_error_response(error, self.config.limits.wire),
-        };
-        encoded.unwrap_or_else(|_| empty_response(StatusCode::INTERNAL_SERVER_ERROR))
     }
 }
 
@@ -404,7 +402,7 @@ struct ParsedRequestHead {
 enum IntakeError {
     Timeout,
     HeaderTooLarge,
-    PayloadTooLarge { target: String },
+    PayloadTooLarge,
     BadRequest,
     Socket,
 }
@@ -425,9 +423,7 @@ fn serve_connection(service: &WipFsServer, mut stream: TcpStream) {
         Err(IntakeError::HeaderTooLarge) => {
             Some(empty_response(StatusCode::REQUEST_HEADER_FIELDS_TOO_LARGE))
         }
-        Err(IntakeError::PayloadTooLarge { target }) => {
+        Err(IntakeError::PayloadTooLarge) => Some(empty_response(StatusCode::PAYLOAD_TOO_LARGE)),
-            Some(payload_too_large_response(service, &target))
-        }
         Err(IntakeError::BadRequest) => Some(empty_response(StatusCode::BAD_REQUEST)),
         Err(IntakeError::Timeout | IntakeError::Socket) => None,
     };
@@ -466,9 +462,7 @@ fn read_http_request(
 
     let parsed = parse_request_head(&received[..header_end])?;
     if parsed.content_length > maximum_body {
-        return Err(IntakeError::PayloadTooLarge {
+        return Err(IntakeError::PayloadTooLarge);
-            target: parsed.target,
-        });
     }
     let mut body = Vec::with_capacity(parsed.content_length);
     let buffered = &received[header_end..];
@@ -567,27 +561,6 @@ fn read_with_deadline(
     })
 }
 
-fn payload_too_large_response(service: &WipFsServer, target: &str) -> Response<Vec<u8>> {
-    let route = service.route(target.split('?').next().unwrap_or_default());
-    route.map_or_else(
-        || empty_response(StatusCode::PAYLOAD_TOO_LARGE),
-        |route| {
-            if route == Route::Batch {
-                service.batch_top_error(
-                    &resource_error(),
-                    Some(ResourceLimitKind::RepresentationBytes),
-                )
-            } else {
-                service.protocol_error(
-                    interaction(route),
-                    &resource_error(),
-                    Some(ResourceLimitKind::RepresentationBytes),
-                )
-            }
-        },
-    )
-}
-
 fn write_http_response(
     stream: &mut TcpStream,
     response: &Response<Vec<u8>>,
@@ -648,20 +621,13 @@ fn write_all_with_deadline(
     stream.flush()
 }
 
-fn interaction(route: Route) -> ProtocolInteraction {
+fn is_transport_limit(error: &CodecError) -> bool {
-    match route {
+    matches!(
-        Route::Observe => ProtocolInteraction::Observe,
+        error,
-        Route::FetchInterface => ProtocolInteraction::FetchInterface,
+        CodecError::BodyTooLarge { .. }
-        Route::CallOperation => ProtocolInteraction::CallOperation,
+            | CodecError::NestingTooDeep { .. }
-        Route::Batch => ProtocolInteraction::Observe,
+            | CodecError::TooManyBatchItems { .. }
-    }
+    )
-}
-
-fn resource_error() -> ProtocolError {
-    ProtocolError {
-        code: ProtocolErrorCode::ResourceLimitExceeded,
-        message: "configured resource limit exceeded".into(),
-    }
 }
 
 fn internal_error() -> ProtocolError {

crates/wip-fs-server/tests/end_to_end.rs

@@ -9,8 +9,9 @@ use std::time::{Duration, Instant};
 use tempfile::tempdir;
 use wip_fs_server::{AccessMode, ServerConfig, WipFsServer};
 use wip_http::{
-    BatchRequest, BatchRequestItem, BatchRequestKind, BatchResponse, BatchSuccess, DecodedResponse,
+    BatchRequest, BatchRequestItem, BatchRequestKind, BatchResponse, BatchSuccess,
-    Endpoint, JSON_CONTENT_TYPE, Limits, Route, decode_batch_request, decode_batch_response,
+    ClientResponseError, DecodedResponse, Endpoint, JSON_CONTENT_TYPE, Limits, Route,
+    TransportFailureKind, decode_batch_request, decode_batch_response,
     decode_call_operation_response, decode_fetch_interface_response, decode_observe_response,
     encode_batch_request, encode_call_operation_request, encode_fetch_interface_request,
     encode_observe_request,
@@ -210,6 +211,166 @@ fn real_listener_serves_three_core_interactions_batch_and_write() {
         .expect("listener exits cleanly");
 }
 
+#[test]
+fn real_listener_keeps_route_method_and_malformed_body_boundaries_distinct() {
+    let temporary = tempdir().expect("temporary root");
+    let mut config = ServerConfig::for_root(temporary.path());
+    config.limits.wire = Limits::new(64, 4_096, 64, 4).expect("wire limits");
+    let bound = Arc::new(
+        WipFsServer::new(config)
+            .expect("build server")
+            .bind()
+            .expect("bind"),
+    );
+    let address = bound.local_addr();
+    let shutdown = Arc::new(AtomicBool::new(false));
+    let worker = {
+        let bound = Arc::clone(&bound);
+        let shutdown = Arc::clone(&shutdown);
+        thread::spawn(move || bound.serve_until(shutdown))
+    };
+
+    for uri in [
+        "/wip/v1/unknown",
+        "/wip/v1/observe?unexpected=true",
+        "/wip/v1/observe/extra",
+    ] {
+        let response = exchange(address, json_request(http::Method::POST, uri, b"{}"));
+        assert_eq!(response.status(), http::StatusCode::NOT_FOUND);
+        assert!(response.body().is_empty());
+        assert!(!response.headers().contains_key(http::header::CONTENT_TYPE));
+    }
+
+    let wrong_method = exchange(
+        address,
+        json_request(http::Method::GET, "/wip/v1/observe", b""),
+    );
+    assert_eq!(wrong_method.status(), http::StatusCode::METHOD_NOT_ALLOWED);
+    assert_eq!(wrong_method.headers()[http::header::ALLOW], "POST");
+    assert!(wrong_method.body().is_empty());
+    assert!(
+        !wrong_method
+            .headers()
+            .contains_key(http::header::CONTENT_TYPE)
+    );
+
+    let mut unsupported_coding = json_request(
+        http::Method::POST,
+        "/wip/v1/observe",
+        br#"{"path":"/","depth":0}"#,
+    );
+    unsupported_coding
+        .headers_mut()
+        .insert(http::header::CONTENT_ENCODING, "gzip".parse().unwrap());
+    let unsupported_coding = exchange(address, unsupported_coding);
+    assert_eq!(
+        unsupported_coding.status(),
+        http::StatusCode::UNSUPPORTED_MEDIA_TYPE
+    );
+    assert!(unsupported_coding.body().is_empty());
+    assert!(
+        !unsupported_coding
+            .headers()
+            .contains_key(http::header::CONTENT_TYPE)
+    );
+
+    let malformed = exchange(
+        address,
+        json_request(http::Method::POST, "/wip/v1/observe", b"{"),
+    );
+    assert_eq!(malformed.status(), http::StatusCode::BAD_REQUEST);
+    assert_eq!(
+        malformed.headers()[http::header::CONTENT_TYPE],
+        JSON_CONTENT_TYPE
+    );
+    assert!(
+        std::str::from_utf8(malformed.body())
+            .expect("UTF-8 error envelope")
+            .contains("\"invalid_request\"")
+    );
+
+    let oversized = exchange(
+        address,
+        json_request(http::Method::POST, "/wip/v1/observe", &[b'x'; 65]),
+    );
+    assert_eq!(oversized.status(), http::StatusCode::PAYLOAD_TOO_LARGE);
+    assert!(oversized.body().is_empty());
+    assert!(!oversized.headers().contains_key(http::header::CONTENT_TYPE));
+
+    let mut header_only = TcpStream::connect(address).expect("connect header-only client");
+    header_only
+        .set_read_timeout(Some(Duration::from_secs(1)))
+        .expect("set header-only timeout");
+    write!(
+        header_only,
+        "POST /wip/v1/observe HTTP/1.1\r\nHost: localhost\r\nContent-Type: application/json\r\nContent-Length: 65\r\n\r\n"
+    )
+    .expect("write oversized request head");
+    header_only.flush().expect("flush oversized request head");
+    let mut raw = Vec::new();
+    header_only
+        .read_to_end(&mut raw)
+        .expect("read immediate limit response");
+    assert!(raw.starts_with(b"HTTP/1.1 413 "));
+    assert!(raw.ends_with(b"\r\n\r\n"));
+    assert!(
+        !raw.windows(b"resource_limit_exceeded".len())
+            .any(|window| { window == b"resource_limit_exceeded" })
+    );
+
+    shutdown.store(true, Ordering::Release);
+    worker
+        .join()
+        .expect("join listener")
+        .expect("listener exits cleanly");
+}
+
+#[test]
+fn raw_decoder_and_batch_packaging_limits_are_transport_failures() {
+    let temporary = tempdir().expect("temporary root");
+    let mut config = ServerConfig::for_root(temporary.path());
+    config.limits.wire = Limits::new(4_096, 4_096, 8, 1).expect("wire limits");
+    let server = WipFsServer::new(config).expect("build server");
+
+    let nested = br#"{"path":[[[[[[[[["/"]]]]]]]]],"depth":0}"#;
+    let response = server.handle_http(json_request(http::Method::POST, "/wip/v1/observe", nested));
+    assert_eq!(response.status(), http::StatusCode::PAYLOAD_TOO_LARGE);
+    assert!(response.body().is_empty());
+    assert!(!response.headers().contains_key(http::header::CONTENT_TYPE));
+
+    let batch = br#"{"requests":[{"id":"one","method":"observe","arguments":{"path":"/","depth":0}},{"id":"two","method":"observe","arguments":{"path":"/","depth":0}}]}"#;
+    let response = server.handle_http(json_request(http::Method::POST, "/wip/v1/batch", batch));
+    assert_eq!(response.status(), http::StatusCode::PAYLOAD_TOO_LARGE);
+    assert!(response.body().is_empty());
+    assert!(!response.headers().contains_key(http::header::CONTENT_TYPE));
+}
+
+#[test]
+fn logical_observation_limit_remains_protocol_resource_failure() {
+    let temporary = tempdir().expect("temporary root");
+    let mut config = ServerConfig::for_root(temporary.path());
+    config.limits.max_observation_depth = 0;
+    let limits = config.limits.wire;
+    let server = WipFsServer::new(config).expect("build server");
+    let endpoint = Endpoint::parse("http://localhost/wip").expect("endpoint");
+    let request = ObserveRequest {
+        path: "/".into(),
+        depth: 1,
+    };
+
+    let response = server.handle_http(
+        encode_observe_request(&endpoint, &request, limits).expect("encode observation"),
+    );
+    assert_eq!(response.status(), http::StatusCode::UNPROCESSABLE_ENTITY);
+    assert!(matches!(
+        decode_observe_response(&request, &response, limits).expect("decode logical limit"),
+        DecodedResponse::ProtocolFailure {
+            error,
+            status_mismatch: None,
+        } if error.code == ProtocolErrorCode::ResourceLimitExceeded
+    ));
+}
+
 #[test]
 fn stalled_request_body_times_out_and_releases_the_only_worker() {
     let temporary = tempdir().expect("temporary root");
@@ -359,7 +520,7 @@ fn backend_invalid_unicode_path_is_not_found_not_internal() {
 }
 
 #[test]
-fn read_response_size_failure_preserves_non_commit_guarantee() {
+fn read_response_size_failure_is_transport_local() {
     let temporary = tempdir().expect("temporary root");
     std::fs::write(temporary.path().join("large"), vec![b'x'; 2_000]).expect("write file");
     let mut config = ServerConfig::for_root(temporary.path());
@@ -406,15 +567,16 @@ fn read_response_size_failure_preserves_non_commit_guarantee() {
         encode_call_operation_request(&endpoint, &call, &interface.descriptor, limits)
             .expect("encode read call"),
     );
-    assert_eq!(response.status(), http::StatusCode::PAYLOAD_TOO_LARGE);
+    assert_eq!(response.status(), http::StatusCode::INTERNAL_SERVER_ERROR);
-    match decode_call_operation_response(&call, &interface.descriptor, &response, limits)
+    assert!(response.body().is_empty());
-        .expect("decode resource failure")
+    assert!(!response.headers().contains_key(http::header::CONTENT_TYPE));
-    {
+    assert!(matches!(
-        DecodedResponse::ProtocolFailure { error, .. } => {
+        decode_call_operation_response(&call, &interface.descriptor, &response, limits)
-            assert_eq!(error.code, ProtocolErrorCode::ResourceLimitExceeded);
+            .expect_err("oversized representation is not a protocol failure"),
-        }
+        ClientResponseError::TransportBinding(failure)
-        DecodedResponse::Success(_) => panic!("oversized read response must fail"),
+            if failure.status == http::StatusCode::INTERNAL_SERVER_ERROR
-    }
+                && failure.kind == TransportFailureKind::HttpStatus
+    ));
 }
 
 fn assert_batch_successes(batch: &BatchResponse) {
@@ -440,6 +602,16 @@ fn success<T>(response: DecodedResponse<T>) -> T {
     }
 }
 
+fn json_request(method: http::Method, uri: &str, body: &[u8]) -> http::Request<Vec<u8>> {
+    http::Request::builder()
+        .method(method)
+        .uri(uri)
+        .header(http::header::CONTENT_TYPE, JSON_CONTENT_TYPE)
+        .header(http::header::ACCEPT, "application/json")
+        .body(body.to_vec())
+        .expect("build JSON request")
+}
+
 fn exchange(address: SocketAddr, request: http::Request<Vec<u8>>) -> http::Response<Vec<u8>> {
     let mut stream = TcpStream::connect(address).expect("connect listener");
     stream

crates/wip-http/src/batch.rs

@@ -11,7 +11,8 @@ use wip_protocol::{
 use crate::response::{self, DecodedResponse};
 use crate::{
     BodyKind, ClientResponseError, CodecError, EncodeHttpError, Endpoint, InvalidResponseKind,
-    JSON_CONTENT_TYPE, Limits, ResourceLimitKind, Route, is_json_content_type, json,
+    JSON_CONTENT_TYPE, Limits, Route, codec::has_supported_content_coding, is_json_content_type,
+    json,
 };
 
 /// A retrieval method accepted by the standard v1 batch endpoint.
@@ -335,20 +336,16 @@ pub fn encode_batch_response(
 
 /// Encodes a top-level batch-envelope failure.
 ///
-/// Item-local failures belong in [`BatchResponseItem`]. Only failures that can
+/// Item-local failures belong in [`BatchResponseItem`]. Only `invalid_request`
-/// reject the batch envelope before item execution are accepted here. A
+/// and `internal` may reject the complete batch as protocol failures; packaging
-/// resource-limit failure defaults to the logical-limit status; use
+/// and representation limits remain transport-local.
-/// [`encode_batch_resource_limit_error_response`] when the concrete class is
-/// known.
 pub fn encode_batch_error_response(
     error: &ProtocolError,
     limits: Limits,
 ) -> Result<Response<Vec<u8>>, EncodeHttpError> {
     if !matches!(
         error.code,
-        ProtocolErrorCode::InvalidRequest
+        ProtocolErrorCode::InvalidRequest | ProtocolErrorCode::Internal
-            | ProtocolErrorCode::ResourceLimitExceeded
-            | ProtocolErrorCode::Internal
     ) {
         return Err(CodecError::InvalidField {
             field: "error.code".into(),
@@ -363,26 +360,6 @@ pub fn encode_batch_error_response(
         .body(body)?)
 }
 
-/// Encodes a class-specific top-level batch `resource_limit_exceeded` failure.
-pub fn encode_batch_resource_limit_error_response(
-    error: &ProtocolError,
-    kind: ResourceLimitKind,
-    limits: Limits,
-) -> Result<Response<Vec<u8>>, EncodeHttpError> {
-    if error.code != ProtocolErrorCode::ResourceLimitExceeded {
-        return Err(CodecError::InvalidField {
-            field: "error.code".into(),
-            reason: "resource-limit encoder requires resource_limit_exceeded".into(),
-        }
-        .into());
-    }
-    let body = json::serialize(&response::error_to_json(error), BodyKind::Response, limits)?;
-    Ok(Response::builder()
-        .status(response::status_for_resource_limit(kind))
-        .header(CONTENT_TYPE, JSON_CONTENT_TYPE)
-        .body(body)?)
-}
-
 fn response_from_json(
     value: &Json,
     request: &BatchRequest,
@@ -466,6 +443,9 @@ pub fn decode_batch_response<B: AsRef<[u8]>>(
     value: &Response<B>,
     limits: Limits,
 ) -> Result<DecodedResponse<BatchResponse>, ClientResponseError> {
+    if !has_supported_content_coding(value.headers()) {
+        return Err(response::unsupported_content_coding(value.status()));
+    }
     let valid_content_type = value
         .headers()
         .get(CONTENT_TYPE)
@@ -496,9 +476,7 @@ pub fn decode_batch_response<B: AsRef<[u8]>>(
     if let DecodedResponse::ProtocolFailure { error, .. } = &decoded
         && !matches!(
             error.code,
-            ProtocolErrorCode::InvalidRequest
+            ProtocolErrorCode::InvalidRequest | ProtocolErrorCode::Internal
-                | ProtocolErrorCode::ResourceLimitExceeded
-                | ProtocolErrorCode::Internal
         )
     {
         return Err(ClientResponseError::invalid(

crates/wip-http/src/codec.rs

@@ -1,7 +1,7 @@
 use std::error::Error;
 use std::fmt::{self, Display, Formatter};
 
-use http::header::{ACCEPT, CONTENT_TYPE};
+use http::header::{ACCEPT, CONTENT_ENCODING, CONTENT_TYPE};
 use http::{HeaderMap, Method, Request, Response, StatusCode};
 use wip_protocol::{
     CallOperationRequest, CallOperationResponse, FetchInterfaceRequest, FetchInterfaceResponse,
@@ -12,7 +12,7 @@ use wip_protocol::{
 use crate::response::{self, DecodedResponse};
 use crate::{
     BodyKind, ClientResponseError, CodecError, Endpoint, InvalidResponseKind, JSON_CONTENT_TYPE,
-    Limits, ResourceLimitKind, Route, json,
+    Limits, Route, json,
 };
 
 fn request(
@@ -36,6 +36,9 @@ fn response(status: StatusCode, body: Vec<u8>) -> Result<Response<Vec<u8>>, http
 }
 
 fn require_response_content_type<B>(response: &Response<B>) -> Result<(), ClientResponseError> {
+    if !has_supported_content_coding(response.headers()) {
+        return Err(response::unsupported_content_coding(response.status()));
+    }
     let valid = response
         .headers()
         .get(CONTENT_TYPE)
@@ -181,9 +184,11 @@ fn accepts_json(headers: &HeaderMap) -> bool {
 /// A failure while validating inbound HTTP request metadata.
 #[derive(Debug)]
 pub enum RequestMetadataError {
-    /// The method or route does not match the selected WIP interaction.
+    /// The request URI does not exactly identify the selected standard route.
-    InvalidRequest(CodecError),
+    NotFound,
-    /// The request body does not use UTF-8 `application/json`.
+    /// A known standard route was requested with a method other than `POST`.
+    MethodNotAllowed,
+    /// The request body does not use UTF-8 `application/json` or identity coding.
     UnsupportedMediaType,
     /// The request's `Accept` metadata excludes `application/json`.
     NotAcceptable,
@@ -194,32 +199,47 @@ impl RequestMetadataError {
     #[must_use]
     pub const fn status(&self) -> StatusCode {
         match self {
-            Self::InvalidRequest(_) => StatusCode::BAD_REQUEST,
+            Self::NotFound => StatusCode::NOT_FOUND,
+            Self::MethodNotAllowed => StatusCode::METHOD_NOT_ALLOWED,
             Self::UnsupportedMediaType => StatusCode::UNSUPPORTED_MEDIA_TYPE,
             Self::NotAcceptable => StatusCode::NOT_ACCEPTABLE,
         }
     }
+
+    /// Returns the value for an `Allow` response header, when required.
+    #[must_use]
+    pub const fn allow(&self) -> Option<&'static str> {
+        match self {
+            Self::MethodNotAllowed => Some("POST"),
+            Self::NotFound | Self::UnsupportedMediaType | Self::NotAcceptable => None,
+        }
+    }
 }
 
 impl Display for RequestMetadataError {
     fn fmt(&self, formatter: &mut Formatter<'_>) -> fmt::Result {
         match self {
-            Self::InvalidRequest(error) => error.fmt(formatter),
+            Self::NotFound => formatter.write_str("request URI is not a standard WIP route"),
+            Self::MethodNotAllowed => formatter.write_str("standard WIP routes require POST"),
             Self::UnsupportedMediaType => {
-                formatter.write_str("expected UTF-8 application/json Content-Type")
+                formatter.write_str("expected identity-coded UTF-8 application/json Content-Type")
             }
             Self::NotAcceptable => formatter.write_str("request does not accept application/json"),
         }
     }
 }
 
-impl Error for RequestMetadataError {
+impl Error for RequestMetadataError {}
-    fn source(&self) -> Option<&(dyn Error + 'static)> {
+
-        match self {
+pub(crate) fn has_supported_content_coding(headers: &HeaderMap) -> bool {
-            Self::InvalidRequest(error) => Some(error),
+    headers.get_all(CONTENT_ENCODING).iter().all(|value| {
-            Self::UnsupportedMediaType | Self::NotAcceptable => None,
+        value.to_str().is_ok_and(|value| {
-        }
+            let mut codings = value.split(',').map(str::trim);
-    }
+            let first = codings.next();
+            first.is_some_and(|coding| coding.eq_ignore_ascii_case("identity"))
+                && codings.all(|coding| coding.eq_ignore_ascii_case("identity"))
+        })
+    })
 }
 
 /// Validates mandatory HTTP metadata for an inbound WIP request.
@@ -233,29 +253,19 @@ pub fn validate_http_request<B>(
     route: Route,
     value: &Request<B>,
 ) -> Result<(), RequestMetadataError> {
-    if value.method() != Method::POST {
-        return Err(RequestMetadataError::InvalidRequest(
-            CodecError::InvalidField {
-                field: "method".into(),
-                reason: "standard WIP routes require POST".into(),
-            },
-        ));
-    }
     let expected = endpoint.route(route);
     if value.uri().path() != expected.path() || value.uri().query().is_some() {
-        return Err(RequestMetadataError::InvalidRequest(
+        return Err(RequestMetadataError::NotFound);
-            CodecError::InvalidField {
+    }
-                field: "route".into(),
+    if value.method() != Method::POST {
-                reason: "request URI does not match the selected standard route".into(),
+        return Err(RequestMetadataError::MethodNotAllowed);
-            },
-        ));
     }
     let valid_content_type = value
         .headers()
         .get(CONTENT_TYPE)
         .and_then(|value| value.to_str().ok())
         .is_some_and(is_json_content_type);
-    if !valid_content_type {
+    if !valid_content_type || !has_supported_content_coding(value.headers()) {
         return Err(RequestMetadataError::UnsupportedMediaType);
     }
     if !accepts_json(value.headers()) {
@@ -526,9 +536,8 @@ fn encode_protocol_error_with_status(
 /// The code must be allowed for `interaction`. This API accepts only
 /// [`ProtocolError`], so client-local `InvalidResponse` and
 /// `UnsupportedDescriptorFormat` classifications cannot be emitted as Host
-/// error envelopes. Resource-limit errors use the logical-limit status; callers
+/// error envelopes. Logical `resource_limit_exceeded` failures use HTTP 422;
-/// that know the concrete limit class should use
+/// representation and deployment limits are not protocol errors.
-/// [`encode_resource_limit_error_response`].
 pub fn encode_protocol_error_response(
     interaction: ProtocolInteraction,
     error: &ProtocolError,
@@ -542,28 +551,6 @@ pub fn encode_protocol_error_response(
     )
 }
 
-/// Encodes a `resource_limit_exceeded` envelope with its class-specific status.
-pub fn encode_resource_limit_error_response(
-    interaction: ProtocolInteraction,
-    error: &ProtocolError,
-    kind: ResourceLimitKind,
-    limits: Limits,
-) -> Result<Response<Vec<u8>>, EncodeHttpError> {
-    if error.code != wip_protocol::ProtocolErrorCode::ResourceLimitExceeded {
-        return Err(CodecError::InvalidField {
-            field: "error.code".into(),
-            reason: "resource-limit encoder requires resource_limit_exceeded".into(),
-        }
-        .into());
-    }
-    encode_protocol_error_with_status(
-        interaction,
-        error,
-        response::status_for_resource_limit(kind),
-        limits,
-    )
-}
-
 /// Failure while building an outbound framework-neutral HTTP message.
 #[derive(Debug)]
 pub enum EncodeHttpError {

crates/wip-http/src/error.rs

@@ -102,15 +102,6 @@ pub enum BodyKind {
     Response,
 }
 
-/// The class of a resource limit exceeded by a wire representation.
-#[derive(Debug, Clone, Copy, PartialEq, Eq)]
-pub enum ResourceLimitKind {
-    /// A request or response representation exceeded its byte-size limit.
-    RepresentationBytes,
-    /// A logical limit such as nesting depth, batch count, or collection size was exceeded.
-    Logical,
-}
-
 /// A malformed or locally disallowed wire representation.
 #[derive(Debug)]
 pub enum CodecError {
@@ -186,20 +177,6 @@ pub enum CodecError {
     },
 }
 
-impl CodecError {
-    /// Classifies this failure when it represents a canonical resource limit.
-    #[must_use]
-    pub const fn resource_limit_kind(&self) -> Option<ResourceLimitKind> {
-        match self {
-            Self::BodyTooLarge { .. } => Some(ResourceLimitKind::RepresentationBytes),
-            Self::NestingTooDeep { .. } | Self::TooManyBatchItems { .. } => {
-                Some(ResourceLimitKind::Logical)
-            }
-            _ => None,
-        }
-    }
-}
-
 impl Display for CodecError {
     fn fmt(&self, formatter: &mut Formatter<'_>) -> fmt::Result {
         match self {

crates/wip-http/src/lib.rs

@@ -40,8 +40,7 @@ mod response;
 pub use batch::{
     BatchMethod, BatchRequest, BatchRequestItem, BatchRequestKind, BatchResponse,
     BatchResponseItem, BatchSuccess, decode_batch_request, decode_batch_response,
-    encode_batch_error_response, encode_batch_request, encode_batch_resource_limit_error_response,
+    encode_batch_error_response, encode_batch_request, encode_batch_response,
-    encode_batch_response,
 };
 pub use codec::{
     CallOperationMetadata, EncodeHttpError, RequestMetadataError, decode_call_operation_metadata,
@@ -49,15 +48,13 @@ pub use codec::{
     decode_fetch_interface_response, decode_observe_request, decode_observe_response,
     encode_call_operation_request, encode_call_operation_response, encode_fetch_interface_request,
     encode_fetch_interface_response, encode_observe_request, encode_observe_response,
-    encode_protocol_error_response, encode_resource_limit_error_response, is_json_content_type,
+    encode_protocol_error_response, is_json_content_type, validate_http_request,
-    validate_http_request,
 };
 pub use endpoint::{Endpoint, EndpointError, JSON_CONTENT_TYPE, Route};
-pub use error::{BodyKind, CodecError, LimitConfigurationError, Limits, ResourceLimitKind};
+pub use error::{BodyKind, CodecError, LimitConfigurationError, Limits};
 pub use response::{
     ClientResponseError, DecodedResponse, InvalidResponseKind, StatusMismatch,
     TransportBindingFailure, TransportFailureKind, error_code_name, status_for_error,
-    status_for_resource_limit,
 };
 
 /// Framework-neutral HTTP types used by this binding's public API.

crates/wip-http/src/response.rs

@@ -5,7 +5,7 @@ use http::StatusCode;
 use serde_json::{Map, Value as Json};
 use wip_protocol::{ProtocolError, ProtocolErrorCode, ProtocolInteraction};
 
-use crate::{BodyKind, CodecError, Limits, ResourceLimitKind, json};
+use crate::{BodyKind, CodecError, Limits, json};
 
 /// A successfully classified client response.
 #[derive(Debug, Clone, PartialEq, Eq)]
@@ -37,6 +37,8 @@ pub enum TransportFailureKind {
     AuthenticationRequired,
     /// HTTP 403, commonly emitted by endpoint policy or infrastructure.
     EndpointForbidden,
+    /// The response uses a content coding the client does not support.
+    UnsupportedContentCoding,
     /// Another non-success HTTP response without a WIP error envelope.
     HttpStatus,
 }
@@ -119,10 +121,6 @@ impl Display for ClientResponseError {
 impl Error for ClientResponseError {}
 
 /// Returns the canonical HTTP status for a wire-level protocol error.
-///
-/// [`ProtocolErrorCode::ResourceLimitExceeded`] defaults to the logical-limit
-/// status. Use [`status_for_resource_limit`] when the concrete limit class is
-/// known.
 #[must_use]
 pub const fn status_for_error(code: ProtocolErrorCode) -> StatusCode {
     match code {
@@ -145,22 +143,8 @@ pub const fn status_for_error(code: ProtocolErrorCode) -> StatusCode {
     }
 }
 
-/// Returns the canonical HTTP status for a concrete resource-limit class.
-#[must_use]
-pub const fn status_for_resource_limit(kind: ResourceLimitKind) -> StatusCode {
-    match kind {
-        ResourceLimitKind::RepresentationBytes => StatusCode::PAYLOAD_TOO_LARGE,
-        ResourceLimitKind::Logical => StatusCode::UNPROCESSABLE_ENTITY,
-    }
-}
-
 fn status_matches_error(status: StatusCode, code: ProtocolErrorCode) -> bool {
-    match code {
+    status == status_for_error(code)
-        ProtocolErrorCode::ResourceLimitExceeded => {
-            status == StatusCode::PAYLOAD_TOO_LARGE || status == StatusCode::UNPROCESSABLE_ENTITY
-        }
-        _ => status == status_for_error(code),
-    }
 }
 
 /// Returns the stable snake-case wire spelling of a protocol code.
@@ -355,6 +339,13 @@ pub(crate) fn decode<T>(
     }
 }
 
+pub(crate) fn unsupported_content_coding(status: StatusCode) -> ClientResponseError {
+    ClientResponseError::TransportBinding(TransportBindingFailure {
+        status,
+        kind: TransportFailureKind::UnsupportedContentCoding,
+    })
+}
+
 pub(crate) fn transport_failure(status: StatusCode) -> ClientResponseError {
     let kind = match status {
         StatusCode::UNAUTHORIZED => TransportFailureKind::AuthenticationRequired,

crates/wip-http/tests/batch.rs

@@ -6,9 +6,8 @@ use wip_http::wip_protocol::{
 use wip_http::{
     BatchMethod, BatchRequest, BatchRequestItem, BatchRequestKind, BatchResponse,
     BatchResponseItem, BatchSuccess, ClientResponseError, DecodedResponse, Endpoint,
-    InvalidResponseKind, Limits, ResourceLimitKind, decode_batch_request, decode_batch_response,
+    InvalidResponseKind, Limits, TransportFailureKind, decode_batch_request, decode_batch_response,
-    encode_batch_error_response, encode_batch_request, encode_batch_resource_limit_error_response,
+    encode_batch_error_response, encode_batch_request, encode_batch_response,
-    encode_batch_response,
 };
 
 fn limits() -> Limits {
@@ -200,29 +199,93 @@ fn invalid_batch_envelopes_are_rejected_at_top_level() {
 }
 
 #[test]
-fn batch_resource_limits_use_413_or_422_and_never_429() {
+fn resource_limit_is_item_local_and_forbidden_as_a_top_level_batch_error() {
     let error = ProtocolError {
         code: ProtocolErrorCode::ResourceLimitExceeded,
-        message: "bounded".into(),
+        message: "logical observation limit exceeded".into(),
     };
-    for (kind, status) in [
+    assert!(encode_batch_error_response(&error, limits()).is_err());
-        (
+
-            ResourceLimitKind::RepresentationBytes,
+    let request = request();
-            StatusCode::PAYLOAD_TOO_LARGE,
+    let response = BatchResponse {
-        ),
+        responses: vec![
-        (ResourceLimitKind::Logical, StatusCode::UNPROCESSABLE_ENTITY),
+            BatchResponseItem {
-    ] {
+                id: "object".into(),
-        let encoded = encode_batch_resource_limit_error_response(&error, kind, limits()).unwrap();
+                outcome: Err(error.clone()),
-        assert_eq!(encoded.status(), status);
+            },
-        assert_ne!(encoded.status(), StatusCode::TOO_MANY_REQUESTS);
+            BatchResponseItem {
-        assert_eq!(
+                id: "interface".into(),
-            decode_batch_response(&request(), &encoded, limits()).unwrap(),
+                outcome: Err(ProtocolError {
-            DecodedResponse::ProtocolFailure {
+                    code: ProtocolErrorCode::InterfaceNotFound,
-                error: error.clone(),
+                    message: "gone".into(),
-                status_mismatch: None,
+                }),
-            }
+            },
-        );
+        ],
-    }
+    };
+    let encoded = encode_batch_response(&request, &response, limits()).unwrap();
+    assert_eq!(encoded.status(), StatusCode::OK);
+    assert_eq!(
+        decode_batch_response(&request, &encoded, limits()).unwrap(),
+        DecodedResponse::Success(response)
+    );
+
+    let top_level = wip_http::http::Response::builder()
+        .status(StatusCode::UNPROCESSABLE_ENTITY)
+        .header("content-type", "application/json; charset=utf-8")
+        .body(br#"{"error":{"code":"resource_limit_exceeded","message":"not allowed"}}"#.to_vec())
+        .unwrap();
+    assert!(matches!(
+        decode_batch_response(&request, &top_level, limits()).unwrap_err(),
+        ClientResponseError::InvalidResponse {
+            kind: InvalidResponseKind::InvalidBatch,
+            ..
+        }
+    ));
+}
+
+#[test]
+fn batch_transport_failures_do_not_become_protocol_errors() {
+    let request = request();
+    let bare_413 = wip_http::http::Response::builder()
+        .status(StatusCode::PAYLOAD_TOO_LARGE)
+        .body(Vec::<u8>::new())
+        .unwrap();
+    assert!(matches!(
+        decode_batch_response(&request, &bare_413, limits()).unwrap_err(),
+        ClientResponseError::TransportBinding(failure)
+            if failure.status == StatusCode::PAYLOAD_TOO_LARGE
+                && failure.kind == TransportFailureKind::HttpStatus
+    ));
+
+    let mut encoded = encode_batch_response(
+        &request,
+        &BatchResponse {
+            responses: vec![
+                BatchResponseItem {
+                    id: "object".into(),
+                    outcome: Ok(BatchSuccess::Observe(observed_item(None))),
+                },
+                BatchResponseItem {
+                    id: "interface".into(),
+                    outcome: Err(ProtocolError {
+                        code: ProtocolErrorCode::InterfaceNotFound,
+                        message: "gone".into(),
+                    }),
+                },
+            ],
+        },
+        limits(),
+    )
+    .unwrap();
+    encoded
+        .headers_mut()
+        .insert("content-encoding", "gzip".parse().unwrap());
+    assert!(matches!(
+        decode_batch_response(&request, &encoded, limits()).unwrap_err(),
+        ClientResponseError::TransportBinding(failure)
+            if failure.status == StatusCode::OK
+                && failure.kind == TransportFailureKind::UnsupportedContentCoding
+    ));
 }
 
 #[test]

crates/wip-http/tests/codecs.rs

@@ -10,11 +10,11 @@ use wip_http::wip_protocol::{
 };
 use wip_http::{
     ClientResponseError, CodecError, DecodedResponse, Endpoint, InvalidResponseKind, Limits,
-    ResourceLimitKind, decode_call_operation_metadata, decode_call_operation_request,
+    decode_call_operation_metadata, decode_call_operation_request, decode_call_operation_response,
-    decode_call_operation_response, decode_fetch_interface_request,
+    decode_fetch_interface_request, decode_fetch_interface_response, decode_observe_request,
-    decode_fetch_interface_response, decode_observe_request, decode_observe_response,
+    decode_observe_response, encode_call_operation_request, encode_call_operation_response,
-    encode_call_operation_request, encode_call_operation_response, encode_fetch_interface_request,
+    encode_fetch_interface_request, encode_fetch_interface_response, encode_observe_request,
-    encode_fetch_interface_response, encode_observe_request, encode_observe_response,
+    encode_observe_response,
 };
 
 fn limits() -> Limits {
@@ -404,23 +404,15 @@ fn malformed_unknown_null_and_noncanonical_base64_are_rejected() {
 }
 
 #[test]
-fn caller_limits_bound_bytes_and_nesting() {
+fn caller_limits_remain_local_codec_failures() {
     let tiny = Limits::new(8, 8, 2, 1).unwrap();
     let too_large = decode_observe_request(br#"{"path":"/long","depth":0}"#, tiny).unwrap_err();
     assert!(matches!(&too_large, CodecError::BodyTooLarge { .. }));
-    assert_eq!(
-        too_large.resource_limit_kind(),
-        Some(ResourceLimitKind::RepresentationBytes)
-    );
 
     let nested = br#"{"path":[[["/"]]],"depth":0}"#;
     let nesting_limited = Limits::new(1024, 1024, 2, 1).unwrap();
     let too_deep = decode_observe_request(nested, nesting_limited).unwrap_err();
     assert!(matches!(&too_deep, CodecError::NestingTooDeep { .. }));
-    assert_eq!(
-        too_deep.resource_limit_kind(),
-        Some(ResourceLimitKind::Logical)
-    );
 
     let outbound_limited = Limits::new(1_000_000, 1_000_000, 1, 10).unwrap();
     assert!(

crates/wip-http/tests/responses.rs

@@ -3,10 +3,9 @@ use wip_http::wip_protocol::{
     ObserveRequest, ProtocolError, ProtocolErrorCode, ProtocolInteraction,
 };
 use wip_http::{
-    ClientResponseError, DecodedResponse, InvalidResponseKind, Limits, ResourceLimitKind,
+    ClientResponseError, DecodedResponse, InvalidResponseKind, Limits, TransportFailureKind,
-    TransportFailureKind, decode_observe_response, encode_protocol_error_response,
+    decode_observe_response, encode_protocol_error_response, error_code_name, is_json_content_type,
-    encode_resource_limit_error_response, error_code_name, is_json_content_type, status_for_error,
+    status_for_error,
-    status_for_resource_limit,
 };
 
 fn limits() -> Limits {
@@ -120,41 +119,45 @@ fn every_protocol_code_has_stable_name_and_status() {
 }
 
 #[test]
-fn resource_limit_statuses_encode_and_decode_by_concrete_limit_class() {
+fn logical_resource_limit_uses_only_422_and_bare_413_is_transport_failure() {
     let error = ProtocolError {
         code: ProtocolErrorCode::ResourceLimitExceeded,
-        message: "bounded".into(),
+        message: "logical observation limit exceeded".into(),
     };
-    let cases = [
+    let encoded =
-        (
-            ResourceLimitKind::RepresentationBytes,
-            StatusCode::PAYLOAD_TOO_LARGE,
-        ),
-        (ResourceLimitKind::Logical, StatusCode::UNPROCESSABLE_ENTITY),
-    ];
-    for (kind, status) in cases {
-        assert_eq!(status_for_resource_limit(kind), status);
-        let encoded = encode_resource_limit_error_response(
-            ProtocolInteraction::Observe,
-            &error,
-            kind,
-            limits(),
-        )
-        .unwrap();
-        assert_eq!(encoded.status(), status);
-        assert_eq!(
-            decode_observe_response(&request(), &encoded, limits()).unwrap(),
-            DecodedResponse::ProtocolFailure {
-                error: error.clone(),
-                status_mismatch: None,
-            }
-        );
-    }
-
-    let default =
         encode_protocol_error_response(ProtocolInteraction::Observe, &error, limits()).unwrap();
-    assert_eq!(default.status(), StatusCode::UNPROCESSABLE_ENTITY);
+    assert_eq!(encoded.status(), StatusCode::UNPROCESSABLE_ENTITY);
-    assert_ne!(default.status(), StatusCode::TOO_MANY_REQUESTS);
+    assert_eq!(
+        decode_observe_response(&request(), &encoded, limits()).unwrap(),
+        DecodedResponse::ProtocolFailure {
+            error: error.clone(),
+            status_mismatch: None,
+        }
+    );
+
+    let mut noncanonical = encoded;
+    *noncanonical.status_mut() = StatusCode::PAYLOAD_TOO_LARGE;
+    assert_eq!(
+        decode_observe_response(&request(), &noncanonical, limits()).unwrap(),
+        DecodedResponse::ProtocolFailure {
+            error,
+            status_mismatch: Some(wip_http::StatusMismatch {
+                actual: StatusCode::PAYLOAD_TOO_LARGE,
+                expected: StatusCode::UNPROCESSABLE_ENTITY,
+            }),
+        }
+    );
+
+    let bare_413 = Response::builder()
+        .status(StatusCode::PAYLOAD_TOO_LARGE)
+        .body(Vec::<u8>::new())
+        .unwrap();
+    assert!(matches!(
+        decode_observe_response(&request(), &bare_413, limits()).unwrap_err(),
+        ClientResponseError::TransportBinding(failure)
+            if failure.status == StatusCode::PAYLOAD_TOO_LARGE
+                && failure.kind == TransportFailureKind::HttpStatus
+    ));
 }
 
 #[test]
@@ -171,6 +174,49 @@ fn rate_limit_status_without_protocol_envelope_stays_transport_failure() {
     ));
 }
 
+#[test]
+fn unsupported_response_content_coding_is_transport_failure() {
+    let mut encoded = encode_protocol_error_response(
+        ProtocolInteraction::Observe,
+        &ProtocolError {
+            code: ProtocolErrorCode::NotFound,
+            message: "missing".into(),
+        },
+        limits(),
+    )
+    .unwrap();
+    encoded
+        .headers_mut()
+        .insert("content-encoding", "gzip".parse().unwrap());
+    assert!(matches!(
+        decode_observe_response(&request(), &encoded, limits()).unwrap_err(),
+        ClientResponseError::TransportBinding(failure)
+            if failure.status == StatusCode::NOT_FOUND
+                && failure.kind == TransportFailureKind::UnsupportedContentCoding
+    ));
+
+    let success = response(StatusCode::OK, br#"{"object":{"name":"","interfaces":[]}}"#);
+    let mut identity = success.clone();
+    identity
+        .headers_mut()
+        .insert("content-encoding", "identity".parse().unwrap());
+    assert!(matches!(
+        decode_observe_response(&request(), &identity, limits()).unwrap(),
+        DecodedResponse::Success(_)
+    ));
+
+    let mut unsupported = success;
+    unsupported
+        .headers_mut()
+        .insert("content-encoding", "br".parse().unwrap());
+    assert!(matches!(
+        decode_observe_response(&request(), &unsupported, limits()).unwrap_err(),
+        ClientResponseError::TransportBinding(failure)
+            if failure.status == StatusCode::OK
+                && failure.kind == TransportFailureKind::UnsupportedContentCoding
+    ));
+}
+
 #[test]
 fn valid_success_body_requires_exactly_http_200() {
     let success_body = br#"{"object":{"name":"","interfaces":[]}}"#;

crates/wip-http/tests/routes.rs

@@ -61,7 +61,10 @@ fn inbound_http_metadata_enforces_post_route_and_json() {
         .header("content-type", "application/json")
         .body(Vec::<u8>::new())
         .unwrap();
-    assert!(validate_http_request(&endpoint, Route::Observe, &wrong_method).is_err());
+    let error = validate_http_request(&endpoint, Route::Observe, &wrong_method).unwrap_err();
+    assert!(matches!(&error, RequestMetadataError::MethodNotAllowed));
+    assert_eq!(error.status(), StatusCode::METHOD_NOT_ALLOWED);
+    assert_eq!(error.allow(), Some("POST"));
 
     let wrong_route = Request::builder()
         .method(Method::POST)
@@ -69,7 +72,21 @@ fn inbound_http_metadata_enforces_post_route_and_json() {
         .header("content-type", "application/json")
         .body(Vec::<u8>::new())
         .unwrap();
-    assert!(validate_http_request(&endpoint, Route::Observe, &wrong_route).is_err());
+    let error = validate_http_request(&endpoint, Route::Observe, &wrong_route).unwrap_err();
+    assert!(matches!(&error, RequestMetadataError::NotFound));
+    assert_eq!(error.status(), StatusCode::NOT_FOUND);
+    assert_eq!(error.allow(), None);
+
+    let query_and_wrong_method = Request::builder()
+        .method(Method::GET)
+        .uri("/wip/v1/observe?unexpected=true")
+        .header("content-type", "application/json")
+        .body(Vec::<u8>::new())
+        .unwrap();
+    assert!(matches!(
+        validate_http_request(&endpoint, Route::Observe, &query_and_wrong_method).unwrap_err(),
+        RequestMetadataError::NotFound
+    ));
 
     for accept in [
         "text/plain, */*;q=1, application/json;q=0",
@@ -114,6 +131,29 @@ fn inbound_http_metadata_enforces_post_route_and_json() {
         validate_http_request(&endpoint, Route::Observe, &unsupported_media_type).unwrap_err();
     assert!(matches!(&error, RequestMetadataError::UnsupportedMediaType));
     assert_eq!(error.status(), StatusCode::UNSUPPORTED_MEDIA_TYPE);
+
+    for coding in ["gzip", "identity, gzip"] {
+        let unsupported_coding = Request::builder()
+            .method(Method::POST)
+            .uri("/wip/v1/observe")
+            .header("content-type", "application/json")
+            .header("content-encoding", coding)
+            .body(Vec::<u8>::new())
+            .unwrap();
+        let error =
+            validate_http_request(&endpoint, Route::Observe, &unsupported_coding).unwrap_err();
+        assert!(matches!(&error, RequestMetadataError::UnsupportedMediaType));
+        assert_eq!(error.status(), StatusCode::UNSUPPORTED_MEDIA_TYPE);
+    }
+
+    let identity_coding = Request::builder()
+        .method(Method::POST)
+        .uri("/wip/v1/observe")
+        .header("content-type", "application/json")
+        .header("content-encoding", "identity")
+        .body(Vec::<u8>::new())
+        .unwrap();
+    assert!(validate_http_request(&endpoint, Route::Observe, &identity_coding).is_ok());
 }
 
 #[test]