feat(plugins): add SubsonicAPI CallRaw, with support for raw=true binary response for host functions (#4982)

* feat: implement raw binary framing for host function responses Signed-off-by: Deluan <deluan@navidrome.org> * feat: add CallRaw method for Subsonic API to handle binary responses Signed-off-by: Deluan <deluan@navidrome.org> * test: add tests for raw=true methods and binary framing generation Signed-off-by: Deluan <deluan@navidrome.org> * fix: improve error message for malformed raw responses to indicate incomplete header Signed-off-by: Deluan <deluan@navidrome.org> * fix: add wasm_import_module attribute for raw methods and improve content-type handling Signed-off-by: Deluan <deluan@navidrome.org> --------- Signed-off-by: Deluan <deluan@navidrome.org>
2026-02-04 15:48:08 -05:00
parent 19ea338bed
commit e8863ed147
23 changed files with 1223 additions and 40 deletions
@@ -264,6 +264,96 @@ var _ = Describe("Generator", func() {
 			Expect(codeStr).To(ContainSubstring(`extism "github.com/extism/go-sdk"`))
 		})

+		It("should generate binary framing for raw=true methods", func() {
+			svc := Service{
+				Name:       "Stream",
+				Permission: "stream",
+				Interface:  "StreamService",
+				Methods: []Method{
+					{
+						Name:     "GetStream",
+						HasError: true,
+						Raw:      true,
+						Params:   []Param{NewParam("uri", "string")},
+						Returns: []Param{
+							NewParam("contentType", "string"),
+							NewParam("data", "[]byte"),
+						},
+					},
+				},
+			}
+
+			code, err := GenerateHost(svc, "host")
+			Expect(err).NotTo(HaveOccurred())
+
+			_, err = format.Source(code)
+			Expect(err).NotTo(HaveOccurred())
+
+			codeStr := string(code)
+
+			// Should include encoding/binary import for raw methods
+			Expect(codeStr).To(ContainSubstring(`"encoding/binary"`))
+
+			// Should NOT generate a response type for raw methods
+			Expect(codeStr).NotTo(ContainSubstring("type StreamGetStreamResponse struct"))
+
+			// Should generate request type (request is still JSON)
+			Expect(codeStr).To(ContainSubstring("type StreamGetStreamRequest struct"))
+
+			// Should build binary frame [0x00][4-byte CT len][CT][data]
+			Expect(codeStr).To(ContainSubstring("frame[0] = 0x00"))
+			Expect(codeStr).To(ContainSubstring("binary.BigEndian.PutUint32"))
+
+			// Should have writeRawError helper
+			Expect(codeStr).To(ContainSubstring("streamWriteRawError"))
+
+			// Should use writeRawError instead of writeError for raw methods
+			Expect(codeStr).To(ContainSubstring("streamWriteRawError(p, stack"))
+		})
+
+		It("should generate both writeError and writeRawError for mixed services", func() {
+			svc := Service{
+				Name:       "API",
+				Permission: "api",
+				Interface:  "APIService",
+				Methods: []Method{
+					{
+						Name:     "Call",
+						HasError: true,
+						Params:   []Param{NewParam("uri", "string")},
+						Returns:  []Param{NewParam("response", "string")},
+					},
+					{
+						Name:     "CallRaw",
+						HasError: true,
+						Raw:      true,
+						Params:   []Param{NewParam("uri", "string")},
+						Returns: []Param{
+							NewParam("contentType", "string"),
+							NewParam("data", "[]byte"),
+						},
+					},
+				},
+			}
+
+			code, err := GenerateHost(svc, "host")
+			Expect(err).NotTo(HaveOccurred())
+
+			_, err = format.Source(code)
+			Expect(err).NotTo(HaveOccurred())
+
+			codeStr := string(code)
+
+			// Should have both helpers
+			Expect(codeStr).To(ContainSubstring("apiWriteResponse"))
+			Expect(codeStr).To(ContainSubstring("apiWriteError"))
+			Expect(codeStr).To(ContainSubstring("apiWriteRawError"))
+
+			// Should generate response type for non-raw method only
+			Expect(codeStr).To(ContainSubstring("type APICallResponse struct"))
+			Expect(codeStr).NotTo(ContainSubstring("type APICallRawResponse struct"))
+		})
+
 		It("should always include json import for JSON protocol", func() {
 			// All services use JSON protocol, so json import is always needed
 			svc := Service{
@@ -626,6 +716,72 @@ var _ = Describe("Generator", func() {
 			Expect(codeStr).To(ContainSubstring(`response.get("floatVal", 0.0)`))
 			Expect(codeStr).To(ContainSubstring(`response.get("boolVal", False)`))
 		})
+
+		It("should generate binary frame parsing for raw methods", func() {
+			svc := Service{
+				Name:       "Stream",
+				Permission: "stream",
+				Interface:  "StreamService",
+				Methods: []Method{
+					{
+						Name:     "GetStream",
+						HasError: true,
+						Raw:      true,
+						Params:   []Param{NewParam("uri", "string")},
+						Returns: []Param{
+							NewParam("contentType", "string"),
+							NewParam("data", "[]byte"),
+						},
+						Doc: "GetStream returns raw binary stream data.",
+					},
+				},
+			}
+
+			code, err := GenerateClientPython(svc)
+			Expect(err).NotTo(HaveOccurred())
+
+			codeStr := string(code)
+
+			// Should import Tuple and struct for raw methods
+			Expect(codeStr).To(ContainSubstring("from typing import Any, Tuple"))
+			Expect(codeStr).To(ContainSubstring("import struct"))
+
+			// Should return Tuple[str, bytes]
+			Expect(codeStr).To(ContainSubstring("-> Tuple[str, bytes]:"))
+
+			// Should parse binary frame instead of JSON
+			Expect(codeStr).To(ContainSubstring("response_bytes = response_mem.bytes()"))
+			Expect(codeStr).To(ContainSubstring("response_bytes[0] == 0x01"))
+			Expect(codeStr).To(ContainSubstring("struct.unpack"))
+			Expect(codeStr).To(ContainSubstring("return content_type, data"))
+
+			// Should NOT use json.loads for response
+			Expect(codeStr).NotTo(ContainSubstring("json.loads(extism.memory.string(response_mem))"))
+		})
+
+		It("should not import Tuple or struct for non-raw services", func() {
+			svc := Service{
+				Name:       "Test",
+				Permission: "test",
+				Interface:  "TestService",
+				Methods: []Method{
+					{
+						Name:     "Call",
+						HasError: true,
+						Params:   []Param{NewParam("uri", "string")},
+						Returns:  []Param{NewParam("response", "string")},
+					},
+				},
+			}
+
+			code, err := GenerateClientPython(svc)
+			Expect(err).NotTo(HaveOccurred())
+
+			codeStr := string(code)
+
+			Expect(codeStr).NotTo(ContainSubstring("Tuple"))
+			Expect(codeStr).NotTo(ContainSubstring("import struct"))
+		})
 	})

 	Describe("GenerateGoDoc", func() {
@@ -782,6 +938,47 @@ var _ = Describe("Generator", func() {
 			// Check for PDK import
 			Expect(codeStr).To(ContainSubstring("github.com/navidrome/navidrome/plugins/pdk/go/pdk"))
 		})
+
+		It("should include encoding/binary import for raw methods", func() {
+			svc := Service{
+				Name:       "Stream",
+				Permission: "stream",
+				Interface:  "StreamService",
+				Methods: []Method{
+					{
+						Name:     "GetStream",
+						HasError: true,
+						Raw:      true,
+						Params:   []Param{NewParam("uri", "string")},
+						Returns: []Param{
+							NewParam("contentType", "string"),
+							NewParam("data", "[]byte"),
+						},
+					},
+				},
+			}
+
+			code, err := GenerateClientGo(svc, "host")
+			Expect(err).NotTo(HaveOccurred())
+
+			codeStr := string(code)
+
+			// Should include encoding/binary for raw binary frame parsing
+			Expect(codeStr).To(ContainSubstring(`"encoding/binary"`))
+
+			// Should NOT generate response type struct for raw methods
+			Expect(codeStr).NotTo(ContainSubstring("streamGetStreamResponse struct"))
+
+			// Should still generate request type
+			Expect(codeStr).To(ContainSubstring("streamGetStreamRequest struct"))
+
+			// Should parse binary frame
+			Expect(codeStr).To(ContainSubstring("responseBytes[0] == 0x01"))
+			Expect(codeStr).To(ContainSubstring("binary.BigEndian.Uint32"))
+
+			// Should return (string, []byte, error)
+			Expect(codeStr).To(ContainSubstring("func StreamGetStream(uri string) (string, []byte, error)"))
+		})
 	})

 	Describe("GenerateClientGoStub", func() {
@@ -1550,6 +1747,51 @@ var _ = Describe("Rust Generation", func() {
 			Expect(codeStr).To(ContainSubstring("Result<bool, Error>"))
 			Expect(codeStr).NotTo(ContainSubstring("Option<bool>"))
 		})
+
+		It("should generate raw extern C import and binary frame parsing for raw methods", func() {
+			svc := Service{
+				Name:       "Stream",
+				Permission: "stream",
+				Interface:  "StreamService",
+				Methods: []Method{
+					{
+						Name:     "GetStream",
+						HasError: true,
+						Raw:      true,
+						Params:   []Param{NewParam("uri", "string")},
+						Returns: []Param{
+							NewParam("contentType", "string"),
+							NewParam("data", "[]byte"),
+						},
+						Doc: "GetStream returns raw binary stream data.",
+					},
+				},
+			}
+
+			code, err := GenerateClientRust(svc)
+			Expect(err).NotTo(HaveOccurred())
+
+			codeStr := string(code)
+
+			// Should use extern "C" with wasm_import_module for raw methods, not #[host_fn] extern "ExtismHost"
+			Expect(codeStr).To(ContainSubstring(`#[link(wasm_import_module = "extism:host/user")]`))
+			Expect(codeStr).To(ContainSubstring(`extern "C"`))
+			Expect(codeStr).To(ContainSubstring("fn stream_getstream(offset: u64) -> u64"))
+
+			// Should NOT generate response type for raw methods
+			Expect(codeStr).NotTo(ContainSubstring("StreamGetStreamResponse"))
+
+			// Should generate request type (request is still JSON)
+			Expect(codeStr).To(ContainSubstring("struct StreamGetStreamRequest"))
+
+			// Should return Result<(String, Vec<u8>), Error>
+			Expect(codeStr).To(ContainSubstring("Result<(String, Vec<u8>), Error>"))
+
+			// Should parse binary frame
+			Expect(codeStr).To(ContainSubstring("response_bytes[0] == 0x01"))
+			Expect(codeStr).To(ContainSubstring("u32::from_be_bytes"))
+			Expect(codeStr).To(ContainSubstring("String::from_utf8_lossy"))
+		})
 	})
 })

@@ -761,6 +761,7 @@ func parseMethod(name string, funcType *ast.FuncType, annotation map[string]stri
 	m := Method{
 		Name:       name,
 		ExportName: annotation["name"],
+		Raw:        annotation["raw"] == "true",
 		Doc:        doc,
 	}

@@ -799,6 +800,13 @@ func parseMethod(name string, funcType *ast.FuncType, annotation map[string]stri
 		}
 	}

+	// Validate raw=true methods: must return exactly (string, []byte, error)
+	if m.Raw {
+		if !m.HasError || len(m.Returns) != 2 || m.Returns[0].Type != "string" || m.Returns[1].Type != "[]byte" {
+			return m, fmt.Errorf("raw=true method %s must return (string, []byte, error) — content-type, data, error", name)
+		}
+	}
+
 	return m, nil
 }

@@ -122,6 +122,119 @@ type TestService interface {
 			Expect(services[0].Methods[0].Name).To(Equal("Exported"))
 		})

+		It("should parse raw=true annotation", func() {
+			src := `package host
+
+import "context"
+
+//nd:hostservice name=Stream permission=stream
+type StreamService interface {
+	//nd:hostfunc raw=true
+	GetStream(ctx context.Context, uri string) (contentType string, data []byte, err error)
+}
+`
+			err := os.WriteFile(filepath.Join(tmpDir, "stream.go"), []byte(src), 0600)
+			Expect(err).NotTo(HaveOccurred())
+
+			services, err := ParseDirectory(tmpDir)
+			Expect(err).NotTo(HaveOccurred())
+			Expect(services).To(HaveLen(1))
+
+			m := services[0].Methods[0]
+			Expect(m.Name).To(Equal("GetStream"))
+			Expect(m.Raw).To(BeTrue())
+			Expect(m.HasError).To(BeTrue())
+			Expect(m.Returns).To(HaveLen(2))
+			Expect(m.Returns[0].Name).To(Equal("contentType"))
+			Expect(m.Returns[0].Type).To(Equal("string"))
+			Expect(m.Returns[1].Name).To(Equal("data"))
+			Expect(m.Returns[1].Type).To(Equal("[]byte"))
+		})
+
+		It("should set Raw=false when raw annotation is absent", func() {
+			src := `package host
+
+import "context"
+
+//nd:hostservice name=Test permission=test
+type TestService interface {
+	//nd:hostfunc
+	Call(ctx context.Context, uri string) (response string, err error)
+}
+`
+			err := os.WriteFile(filepath.Join(tmpDir, "test.go"), []byte(src), 0600)
+			Expect(err).NotTo(HaveOccurred())
+
+			services, err := ParseDirectory(tmpDir)
+			Expect(err).NotTo(HaveOccurred())
+			Expect(services[0].Methods[0].Raw).To(BeFalse())
+		})
+
+		It("should reject raw=true with invalid return signature", func() {
+			src := `package host
+
+import "context"
+
+//nd:hostservice name=Test permission=test
+type TestService interface {
+	//nd:hostfunc raw=true
+	BadRaw(ctx context.Context, uri string) (result string, err error)
+}
+`
+			err := os.WriteFile(filepath.Join(tmpDir, "test.go"), []byte(src), 0600)
+			Expect(err).NotTo(HaveOccurred())
+
+			_, err = ParseDirectory(tmpDir)
+			Expect(err).To(HaveOccurred())
+			Expect(err.Error()).To(ContainSubstring("raw=true"))
+			Expect(err.Error()).To(ContainSubstring("must return (string, []byte, error)"))
+		})
+
+		It("should reject raw=true without error return", func() {
+			src := `package host
+
+import "context"
+
+//nd:hostservice name=Test permission=test
+type TestService interface {
+	//nd:hostfunc raw=true
+	BadRaw(ctx context.Context, uri string) (contentType string, data []byte)
+}
+`
+			err := os.WriteFile(filepath.Join(tmpDir, "test.go"), []byte(src), 0600)
+			Expect(err).NotTo(HaveOccurred())
+
+			_, err = ParseDirectory(tmpDir)
+			Expect(err).To(HaveOccurred())
+			Expect(err.Error()).To(ContainSubstring("raw=true"))
+		})
+
+		It("should parse mixed raw and non-raw methods", func() {
+			src := `package host
+
+import "context"
+
+//nd:hostservice name=API permission=api
+type APIService interface {
+	//nd:hostfunc
+	Call(ctx context.Context, uri string) (responseJSON string, err error)
+
+	//nd:hostfunc raw=true
+	CallRaw(ctx context.Context, uri string) (contentType string, data []byte, err error)
+}
+`
+			err := os.WriteFile(filepath.Join(tmpDir, "api.go"), []byte(src), 0600)
+			Expect(err).NotTo(HaveOccurred())
+
+			services, err := ParseDirectory(tmpDir)
+			Expect(err).NotTo(HaveOccurred())
+			Expect(services).To(HaveLen(1))
+			Expect(services[0].Methods).To(HaveLen(2))
+			Expect(services[0].Methods[0].Raw).To(BeFalse())
+			Expect(services[0].Methods[1].Raw).To(BeTrue())
+			Expect(services[0].HasRawMethods()).To(BeTrue())
+		})
+
 		It("should handle custom export name", func() {
 			src := `package host

@@ -8,6 +8,9 @@
 package {{.Package}}

 import (
+{{- if .Service.HasRawMethods}}
+	"encoding/binary"
+{{- end}}
 	"encoding/json"
 {{- if .Service.HasErrors}}
 	"errors"
@@ -49,7 +52,7 @@ type {{requestType .}} struct {
 {{- end}}
 }
 {{- end}}
-{{- if not .IsErrorOnly}}
+{{- if and (not .IsErrorOnly) (not .Raw)}}

 type {{responseType .}} struct {
 {{- range .Returns}}
@@ -95,7 +98,27 @@ func {{$.Service.Name}}{{.Name}}({{range $i, $p := .Params}}{{if $i}}, {{end}}{{
 	// Read the response from memory
 	responseMem := pdk.FindMemory(responsePtr)
 	responseBytes := responseMem.ReadBytes()
-{{- if .IsErrorOnly}}
+{{- if .Raw}}
+
+	// Parse binary-framed response
+	if len(responseBytes) == 0 {
+		return "", nil, errors.New("empty response from host")
+	}
+	if responseBytes[0] == 0x01 { // error
+		return "", nil, errors.New(string(responseBytes[1:]))
+	}
+	if responseBytes[0] != 0x00 {
+		return "", nil, errors.New("unknown response status")
+	}
+	if len(responseBytes) < 5 {
+		return "", nil, errors.New("malformed raw response: incomplete header")
+	}
+	ctLen := binary.BigEndian.Uint32(responseBytes[1:5])
+	if uint32(len(responseBytes)) < 5+ctLen {
+		return "", nil, errors.New("malformed raw response: content-type overflow")
+	}
+	return string(responseBytes[5 : 5+ctLen]), responseBytes[5+ctLen:], nil
+{{- else if .IsErrorOnly}}

 	// Parse error-only response
 	var response struct {
@@ -8,10 +8,13 @@
 # main __init__.py file. Copy the needed functions from this file into your plugin.

 from dataclasses import dataclass
-from typing import Any
+from typing import Any{{- if .Service.HasRawMethods}}, Tuple{{end}}

 import extism
 import json
+{{- if .Service.HasRawMethods}}
+import struct
+{{- end}}


 class HostFunctionError(Exception):
@@ -29,7 +32,7 @@ def _{{exportName .}}(offset: int) -> int:
 {{- end}}
 {{- /* Generate dataclasses for multi-value returns */ -}}
 {{range .Service.Methods}}
-{{- if .NeedsResultClass}}
+{{- if and .NeedsResultClass (not .Raw)}}


@dataclass
@@ -44,7 +47,7 @@ class {{pythonResultType .}}:
 {{range .Service.Methods}}


-def {{pythonFunc .}}({{range $i, $p := .Params}}{{if $i}}, {{end}}{{$p.PythonName}}: {{$p.PythonType}}{{end}}){{if .NeedsResultClass}} -> {{pythonResultType .}}{{else if .HasReturns}} -> {{(index .Returns 0).PythonType}}{{else}} -> None{{end}}:
+def {{pythonFunc .}}({{range $i, $p := .Params}}{{if $i}}, {{end}}{{$p.PythonName}}: {{$p.PythonType}}{{end}}){{if .Raw}} -> Tuple[str, bytes]{{else if .NeedsResultClass}} -> {{pythonResultType .}}{{else if .HasReturns}} -> {{(index .Returns 0).PythonType}}{{else}} -> None{{end}}:
    """{{if .Doc}}{{.Doc}}{{else}}Call the {{exportName .}} host function.{{end}}
 {{- if .HasParams}}

@@ -53,7 +56,11 @@ def {{pythonFunc .}}({{range $i, $p := .Params}}{{if $i}}, {{end}}{{$p.PythonNam
        {{.PythonName}}: {{.PythonType}} parameter.
 {{- end}}
 {{- end}}
-{{- if .HasReturns}}
+{{- if .Raw}}
+
+    Returns:
+        Tuple of (content_type, data) with the raw binary response.
+{{- else if .HasReturns}}

    Returns:
 {{- if .NeedsResultClass}}
@@ -79,6 +86,24 @@ def {{pythonFunc .}}({{range $i, $p := .Params}}{{if $i}}, {{end}}{{$p.PythonNam
    request_mem = extism.memory.alloc(request_bytes)
    response_offset = _{{exportName .}}(request_mem.offset)
    response_mem = extism.memory.find(response_offset)
+{{- if .Raw}}
+    response_bytes = response_mem.bytes()
+
+    if len(response_bytes) == 0:
+        raise HostFunctionError("empty response from host")
+    if response_bytes[0] == 0x01:
+        raise HostFunctionError(response_bytes[1:].decode("utf-8"))
+    if response_bytes[0] != 0x00:
+        raise HostFunctionError("unknown response status")
+    if len(response_bytes) < 5:
+        raise HostFunctionError("malformed raw response: incomplete header")
+    ct_len = struct.unpack(">I", response_bytes[1:5])[0]
+    if len(response_bytes) < 5 + ct_len:
+        raise HostFunctionError("malformed raw response: content-type overflow")
+    content_type = response_bytes[5:5 + ct_len].decode("utf-8")
+    data = response_bytes[5 + ct_len:]
+    return content_type, data
+{{- else}}
    response = json.loads(extism.memory.string(response_mem))
 {{if .HasError}}
    if response.get("error"):
@@ -94,3 +119,4 @@ def {{pythonFunc .}}({{range $i, $p := .Params}}{{if $i}}, {{end}}{{$p.PythonNam
    return response.get("{{(index .Returns 0).JSONName}}"{{pythonDefault (index .Returns 0)}})
 {{- end}}
 {{- end}}
+{{- end}}
@@ -33,6 +33,7 @@ struct {{requestType .}} {
 {{- end}}
 }
 {{- end}}
+{{- if not .Raw}}

 #[derive(Debug, Clone, Deserialize)]
 #[serde(rename_all = "camelCase")]
@@ -47,16 +48,92 @@ struct {{responseType .}} {
 {{- end}}
 }
 {{- end}}
+{{- end}}

 #[host_fn]
 extern "ExtismHost" {
 {{- range .Service.Methods}}
+{{- if not .Raw}}
    fn {{exportName .}}(input: Json<{{if .HasParams}}{{requestType .}}{{else}}serde_json::Value{{end}}>) -> Json<{{responseType .}}>;
 {{- end}}
+{{- end}}
 }
+{{- /* Declare raw extern "C" imports for raw methods */ -}}
+{{- range .Service.Methods}}
+{{- if .Raw}}
+
+#[link(wasm_import_module = "extism:host/user")]
+extern "C" {
+    fn {{exportName .}}(offset: u64) -> u64;
+}
+{{- end}}
+{{- end}}

 {{- /* Generate wrapper functions */ -}}
 {{range .Service.Methods}}
+{{- if .Raw}}
+
+{{if .Doc}}{{rustDocComment .Doc}}{{else}}/// Calls the {{exportName .}} host function.{{end}}
+{{- if .HasParams}}
+///
+/// # Arguments
+{{- range .Params}}
+/// * `{{.RustName}}` - {{rustType .}} parameter.
+{{- end}}
+{{- end}}
+///
+/// # Returns
+/// A tuple of (content_type, data) with the raw binary response.
+///
+/// # Errors
+/// Returns an error if the host function call fails.
+pub fn {{rustFunc .}}({{range $i, $p := .Params}}{{if $i}}, {{end}}{{$p.RustName}}: {{rustParamType $p}}{{end}}) -> Result<(String, Vec<u8>), Error> {
+{{- if .HasParams}}
+    let req = {{requestType .}} {
+{{- range .Params}}
+        {{.RustName}}: {{.RustName}}{{if .NeedsToOwned}}.to_owned(){{end}},
+{{- end}}
+    };
+    let input_bytes = serde_json::to_vec(&req).map_err(|e| Error::msg(e.to_string()))?;
+{{- else}}
+    let input_bytes = b"{}".to_vec();
+{{- end}}
+    let input_mem = Memory::from_bytes(&input_bytes).map_err(|e| Error::msg(e.to_string()))?;
+
+    let response_offset = unsafe { {{exportName .}}(input_mem.offset()) };
+
+    let response_mem = Memory::find(response_offset)
+        .ok_or_else(|| Error::msg("empty response from host"))?;
+    let response_bytes = response_mem.to_vec();
+
+    if response_bytes.is_empty() {
+        return Err(Error::msg("empty response from host"));
+    }
+    if response_bytes[0] == 0x01 {
+        let msg = String::from_utf8_lossy(&response_bytes[1..]).to_string();
+        return Err(Error::msg(msg));
+    }
+    if response_bytes[0] != 0x00 {
+        return Err(Error::msg("unknown response status"));
+    }
+    if response_bytes.len() < 5 {
+        return Err(Error::msg("malformed raw response: incomplete header"));
+    }
+    let ct_len = u32::from_be_bytes([
+        response_bytes[1],
+        response_bytes[2],
+        response_bytes[3],
+        response_bytes[4],
+    ]) as usize;
+    if ct_len > response_bytes.len() - 5 {
+        return Err(Error::msg("malformed raw response: content-type overflow"));
+    }
+    let ct_end = 5 + ct_len;
+    let content_type = String::from_utf8_lossy(&response_bytes[5..ct_end]).to_string();
+    let data = response_bytes[ct_end..].to_vec();
+    Ok((content_type, data))
+}
+{{- else}}

 {{if .Doc}}{{rustDocComment .Doc}}{{else}}/// Calls the {{exportName .}} host function.{{end}}
 {{- if .HasParams}}
@@ -132,3 +209,4 @@ pub fn {{rustFunc .}}({{range $i, $p := .Params}}{{if $i}}, {{end}}{{$p.RustName
 }
 {{- end}}
 {{- end}}
+{{- end}}
@@ -4,6 +4,9 @@ package {{.Package}}

 import (
 	"context"
+{{- if .Service.HasRawMethods}}
+	"encoding/binary"
+{{- end}}
 	"encoding/json"

 	extism "github.com/extism/go-sdk"
@@ -20,6 +23,7 @@ type {{requestType .}} struct {
 {{- end}}
 }
 {{- end}}
+{{- if not .Raw}}

 // {{responseType .}} is the response type for {{$.Service.Name}}.{{.Name}}.
 type {{responseType .}} struct {
@@ -30,6 +34,7 @@ type {{responseType .}} struct {
 	Error string `json:"error,omitempty"`
 {{- end}}
 }
+{{- end}}
 {{end}}

 // Register{{.Service.Name}}HostFunctions registers {{.Service.Name}} service host functions.
@@ -51,18 +56,48 @@ func new{{$.Service.Name}}{{.Name}}HostFunction(service {{$.Service.Interface}})
 			// Read JSON request from plugin memory
 			reqBytes, err := p.ReadBytes(stack[0])
 			if err != nil {
+{{- if .Raw}}
+				{{$.Service.Name | lower}}WriteRawError(p, stack, err)
+{{- else}}
 				{{$.Service.Name | lower}}WriteError(p, stack, err)
+{{- end}}
 				return
 			}
 			var req {{requestType .}}
 			if err := json.Unmarshal(reqBytes, &req); err != nil {
+{{- if .Raw}}
+				{{$.Service.Name | lower}}WriteRawError(p, stack, err)
+{{- else}}
 				{{$.Service.Name | lower}}WriteError(p, stack, err)
+{{- end}}
 				return
 			}
 {{- end}}

 			// Call the service method
-{{- if .HasReturns}}
+{{- if .Raw}}
+			{{range $i, $r := .Returns}}{{if $i}}, {{end}}{{lower $r.Name}}{{end}}, svcErr := service.{{.Name}}(ctx{{range .Params}}, req.{{title .Name}}{{end}})
+			if svcErr != nil {
+				{{$.Service.Name | lower}}WriteRawError(p, stack, svcErr)
+				return
+			}
+
+			// Write binary-framed response to plugin memory:
+			// [0x00][4-byte content-type length (big-endian)][content-type string][raw data]
+			ctBytes := []byte({{lower (index .Returns 0).Name}})
+			frame := make([]byte, 1+4+len(ctBytes)+len({{lower (index .Returns 1).Name}}))
+			frame[0] = 0x00 // success
+			binary.BigEndian.PutUint32(frame[1:5], uint32(len(ctBytes)))
+			copy(frame[5:5+len(ctBytes)], ctBytes)
+			copy(frame[5+len(ctBytes):], {{lower (index .Returns 1).Name}})
+
+			respPtr, err := p.WriteBytes(frame)
+			if err != nil {
+				stack[0] = 0
+				return
+			}
+			stack[0] = respPtr
+{{- else if .HasReturns}}
 {{- if .HasError}}
 			{{range $i, $r := .Returns}}{{if $i}}, {{end}}{{lower $r.Name}}{{end}}, svcErr := service.{{.Name}}(ctx{{range .Params}}, req.{{title .Name}}{{end}})
 			if svcErr != nil {
@@ -72,14 +107,6 @@ func new{{$.Service.Name}}{{.Name}}HostFunction(service {{$.Service.Interface}})
 {{- else}}
 			{{range $i, $r := .Returns}}{{if $i}}, {{end}}{{lower $r.Name}}{{end}} := service.{{.Name}}(ctx{{range .Params}}, req.{{title .Name}}{{end}})
 {{- end}}
-{{- else if .HasError}}
-			if svcErr := service.{{.Name}}(ctx{{range .Params}}, req.{{title .Name}}{{end}}); svcErr != nil {
-				{{$.Service.Name | lower}}WriteError(p, stack, svcErr)
-				return
-			}
-{{- else}}
-			service.{{.Name}}(ctx{{range .Params}}, req.{{title .Name}}{{end}})
-{{- end}}

 			// Write JSON response to plugin memory
 			resp := {{responseType .}}{
@@ -88,6 +115,22 @@ func new{{$.Service.Name}}{{.Name}}HostFunction(service {{$.Service.Interface}})
 {{- end}}
 			}
 			{{$.Service.Name | lower}}WriteResponse(p, stack, resp)
+{{- else if .HasError}}
+			if svcErr := service.{{.Name}}(ctx{{range .Params}}, req.{{title .Name}}{{end}}); svcErr != nil {
+				{{$.Service.Name | lower}}WriteError(p, stack, svcErr)
+				return
+			}
+
+			// Write JSON response to plugin memory
+			resp := {{responseType .}}{}
+			{{$.Service.Name | lower}}WriteResponse(p, stack, resp)
+{{- else}}
+			service.{{.Name}}(ctx{{range .Params}}, req.{{title .Name}}{{end}})
+
+			// Write JSON response to plugin memory
+			resp := {{responseType .}}{}
+			{{$.Service.Name | lower}}WriteResponse(p, stack, resp)
+{{- end}}
 		},
 		[]extism.ValueType{extism.ValueTypePTR},
 		[]extism.ValueType{extism.ValueTypePTR},
@@ -119,3 +162,16 @@ func {{.Service.Name | lower}}WriteError(p *extism.CurrentPlugin, stack []uint64
 	respPtr, _ := p.WriteBytes(respBytes)
 	stack[0] = respPtr
 }
+{{- if .Service.HasRawMethods}}
+
+// {{.Service.Name | lower}}WriteRawError writes a binary-framed error response to plugin memory.
+// Format: [0x01][UTF-8 error message]
+func {{.Service.Name | lower}}WriteRawError(p *extism.CurrentPlugin, stack []uint64, err error) {
+	errMsg := []byte(err.Error())
+	frame := make([]byte, 1+len(errMsg))
+	frame[0] = 0x01 // error
+	copy(frame[1:], errMsg)
+	respPtr, _ := p.WriteBytes(frame)
+	stack[0] = respPtr
+}
+{{- end}}
@@ -173,6 +173,16 @@ func (s Service) HasErrors() bool {
 	return false
 }

+// HasRawMethods returns true if any method in the service uses raw binary framing.
+func (s Service) HasRawMethods() bool {
+	for _, m := range s.Methods {
+		if m.Raw {
+			return true
+		}
+	}
+	return false
+}
+
 // Method represents a host function method within a service.
 type Method struct {
 	Name       string  // Go method name (e.g., "Call")
@@ -181,6 +191,7 @@ type Method struct {
 	Returns    []Param // Return values (excluding error)
 	HasError   bool    // Whether the method returns an error
 	Doc        string  // Documentation comment for the method
+	Raw        bool    // If true, response uses binary framing instead of JSON
 }

 // FunctionName returns the Extism host function export name.