feat(examples): add Dynamo Switchyard PreProc service

Cargo.toml

@@ -4,6 +4,7 @@
 [workspace]
 resolver = "3"
 members = [
+    "examples/dynamo-preproc",
     "crates/libsy",
     "crates/libsy-llm-client",
     "crates/prefill-router",

Dockerfile

@@ -10,6 +10,7 @@ COPY Cargo.toml Cargo.lock rust-toolchain.toml ./
 # .cargo/config.toml carries the workspace rustflags (target-cpu, force-frame-pointers).
 COPY .cargo ./.cargo
 COPY crates ./crates
+COPY examples/dynamo-preproc ./examples/dynamo-preproc
 
 RUN cargo build --locked --release -p switchyard-server
 

README.md

@@ -23,6 +23,7 @@ Evaluate the complete agent, model pool, and routing configuration against your
 | Gateway | Start here | Current limits |
 | --- | --- | --- |
 | **LiteLLM** | [Run the Switchyard routing-plugin example](examples/litellm/README.md#quick-start-with-the-local-proxy) | Experimental and checkout-only. The example pins LiteLLM 1.102.0 and supports Stage routing based on request history, plus Random routing. It cannot service intermediate model calls required by classifier or escalation algorithms. |
+| **Dynamo / agentgateway** | [Build the Switchyard PreProc example](examples/dynamo-preproc/README.md) | agentgateway 1.0.0, existing Dynamo model pools and EPPs. One PreProc replica; text and function-tool history only. |
 | **NeMo Relay** | [Build and configure the native plugin](crates/switchyard-nemo-relay-plugin/README.md#build-from-source) | Requires Relay `>=0.8.0, <1.0.0`. The source-build path requires a Rust toolchain and Python 3. |
 
 Relay 0.8.x and 0.9.0 can lose upstream error status and details when the plugin

benchmark/switchyard-server.Dockerfile

@@ -17,6 +17,7 @@ ENV PATH="/opt/switchyard/.venv/bin:${PATH}" \
 
 COPY pyproject.toml uv.lock README.md Cargo.toml Cargo.lock ./
 COPY crates ./crates
+COPY examples/dynamo-preproc ./examples/dynamo-preproc
 COPY switchyard ./switchyard
 COPY switchyard_rust ./switchyard_rust
 

crates/switchyard-translation/src/codecs/openai_chat/buffered.rs

@@ -140,7 +140,7 @@ impl FormatCodec for OpenAiChatCodec {
                         content: vec![ContentBlock::ToolResult(ToolResult {
                             tool_call_id,
                             content: vec![ContentBlock::Text { text }],
-                            is_error: None,
+                            is_error: message.get("is_error").and_then(Value::as_bool),
                         })],
                     });
                     continue;

crates/switchyard-translation/tests/request_translation.rs

@@ -3311,6 +3311,30 @@ fn openai_stop_string_maps_to_anthropic_stop_sequences() -> TestResult {
     Ok(())
 }
 
+#[test]
+fn openai_tool_result_error_flag_survives_decoding() -> TestResult {
+    let engine = TranslationEngine::default();
+    for (flag, expected) in [
+        (Some(json!(true)), Some(true)),
+        (Some(json!(false)), Some(false)),
+        (None, None),
+        (Some(Value::Null), None),
+        (Some(json!("true")), None),
+    ] {
+        let mut message = json!({"role": "tool", "tool_call_id": "call_1", "content": "result"});
+        if let Some(flag) = flag {
+            message["is_error"] = flag;
+        }
+        let body = json!({"model": "route", "messages": [message]});
+        let decoded = engine.decode_request(WireFormat::OpenAiChat, &body, &normalized_policy())?;
+        let ContentBlock::ToolResult(result) = &decoded.request.messages[0].content[0] else {
+            panic!("expected tool result");
+        };
+        assert_eq!(result.is_error, expected);
+    }
+    Ok(())
+}
+
 // Verifies OpenAI tool results merge into Anthropic user tool-result content.
 #[test]
 fn openai_tool_results_are_merged_when_translating_to_anthropic() -> TestResult {

examples/dynamo-preproc/Cargo.toml

@@ -0,0 +1,43 @@
+# SPDX-FileCopyrightText: Copyright (c) 2025-2026 NVIDIA CORPORATION & AFFILIATES. All rights reserved.
+# SPDX-License-Identifier: Apache-2.0
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+# http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+[package]
+name = "switchyard-preproc"
+version = "0.1.0"
+edition = "2024"
+rust-version = "1.96.1"
+license = "Apache-2.0"
+publish = false
+
+[dependencies]
+switchyard-runner.workspace = true
+switchyard-protocol.workspace = true
+switchyard-translation.workspace = true
+anyhow = "1"
+async-stream.workspace = true
+axum = "0.8"
+futures-util.workspace = true
+http.workspace = true
+envoy-types = "=0.6.1"
+serde_json = { workspace = true, features = ["raw_value"] }
+tokio.workspace = true
+tonic = "0.13.1"
+thiserror.workspace = true
+tracing.workspace = true
+tracing-subscriber.workspace = true
+
+[dev-dependencies]
+tokio = { workspace = true, features = ["test-util"] }
+tokio-stream = { version = "0.1", features = ["net"] }