fix(ai-formats): support OpenAI Responses custom tool/raw passthrough

crates/aether-ai-formats/src/formats/openai/responses/request.rs

@@ -11,14 +11,15 @@ use crate::{
         canonical_response_format_to_openai_responses, canonical_tool_is_openai_custom,
         canonical_tool_use_to_openai_responses_item, is_claude_messages_request,
         is_claude_system_instruction, is_claude_thinking_block, is_claude_tool_result,
-        is_openai_thinking_block, media_data_or_url, namespace_extension_object,
-        openai_content_text, openai_extensions, openai_response_format_to_canonical,
-        openai_responses_extension, openai_responses_generation_config,
-        openai_responses_input_to_canonical_messages, openai_responses_tool_choice_to_canonical,
-        openai_responses_tools_to_canonical, openai_tool_choice_raw_to_responses,
-        CanonicalContentBlock, CanonicalInstruction, CanonicalRequest, CanonicalRole,
-        CanonicalThinkingConfig, CanonicalToolChoice, CanonicalToolDefinition,
-        OPENAI_RESPONSES_EXTENSION_NAMESPACE, OPENAI_RESPONSES_LEGACY_EXTENSION_NAMESPACE,
+        is_openai_responses_input_message, is_openai_thinking_block, media_data_or_url,
+        namespace_extension_object, openai_content_text, openai_extensions,
+        openai_response_format_to_canonical, openai_responses_extension,
+        openai_responses_generation_config, openai_responses_input_to_canonical_messages,
+        openai_responses_tool_choice_to_canonical, openai_responses_tools_to_canonical,
+        openai_tool_choice_raw_to_responses, CanonicalContentBlock, CanonicalInstruction,
+        CanonicalRequest, CanonicalRole, CanonicalThinkingConfig, CanonicalToolChoice,
+        CanonicalToolDefinition, OPENAI_RESPONSES_EXTENSION_NAMESPACE,
+        OPENAI_RESPONSES_LEGACY_EXTENSION_NAMESPACE,
     },
 };
 
@@ -307,6 +308,12 @@ fn canonical_messages_to_responses_input(canonical: &CanonicalRequest) -> Option
         let role = match message.role {
             CanonicalRole::Assistant => "assistant",
             CanonicalRole::Tool | CanonicalRole::User | CanonicalRole::Unknown => "user",
+            CanonicalRole::System if is_openai_responses_input_message(&message.extensions) => {
+                "system"
+            }
+            CanonicalRole::Developer if is_openai_responses_input_message(&message.extensions) => {
+                "developer"
+            }
             CanonicalRole::System | CanonicalRole::Developer => continue,
         };
         let mut content = Vec::new();
@@ -806,14 +813,6 @@ fn canonical_tool_to_responses(tool: &CanonicalToolDefinition) -> Value {
             tool.extensions
                 .get(OPENAI_RESPONSES_LEGACY_EXTENSION_NAMESPACE)
         })
-        .filter(|value| {
-            value
-                .get("type")
-                .and_then(Value::as_str)
-                .is_some_and(|tool_type| {
-                    tool_type == "custom" || tool_type.starts_with("web_search")
-                })
-        })
     {
         return raw.clone();
     }

crates/aether-ai-formats/src/formats/openai/responses/response.rs

@@ -10,11 +10,12 @@ use crate::{
     protocol::canonical::{
         canonical_content_block_to_openai_responses_part, canonical_extension_object_mut,
         canonical_tool_use_to_openai_responses_item, canonical_usage_to_openai_responses_usage,
-        flush_openai_responses_message_item, is_openai_thinking_block, namespace_extension_object,
-        openai_responses_extensions, openai_responses_output_to_canonical_blocks,
-        openai_usage_to_canonical, CanonicalContentBlock, CanonicalResponse,
-        CanonicalResponseOutput, CanonicalRole, CanonicalStopReason,
-        OPENAI_RESPONSES_EXTENSION_NAMESPACE, OPENAI_RESPONSES_LEGACY_EXTENSION_NAMESPACE,
+        flush_openai_responses_message_item, is_openai_responses_raw_block,
+        is_openai_thinking_block, namespace_extension_object, openai_responses_extensions,
+        openai_responses_output_to_canonical_blocks, openai_usage_to_canonical,
+        CanonicalContentBlock, CanonicalResponse, CanonicalResponseOutput, CanonicalRole,
+        CanonicalStopReason, OPENAI_RESPONSES_EXTENSION_NAMESPACE,
+        OPENAI_RESPONSES_LEGACY_EXTENSION_NAMESPACE,
     },
 };
 
@@ -273,6 +274,19 @@ pub fn to_raw(canonical: &CanonicalResponse, report_context: &Value, _compact: b
                     }
                 }
             }
+            CanonicalContentBlock::Unknown {
+                payload,
+                extensions,
+                ..
+            } if is_openai_responses_raw_block(extensions) => {
+                flush_openai_responses_message_item(
+                    &mut output,
+                    &mut message_content,
+                    &response_id,
+                    &mut message_index,
+                );
+                output.push(payload.clone());
+            }
             CanonicalContentBlock::Unknown { .. } => {}
         }
     }

crates/aether-ai-formats/src/formats/registry.rs

@@ -356,9 +356,38 @@ fn validate_response_conversion(
     }
 
     validate_source_response_stop_enums(source, target, body)?;
+    validate_response_content_has_no_unknown_blocks(source, target, response)?;
     validate_canonical_response_stop_reasons(source, target, response)
 }
 
+fn validate_response_content_has_no_unknown_blocks(
+    source: FormatId,
+    target: FormatId,
+    response: &CanonicalResponse,
+) -> Result<(), FormatError> {
+    for block in response.content.iter().chain(
+        response
+            .outputs
+            .iter()
+            .flat_map(|output| output.content.iter()),
+    ) {
+        if let CanonicalContentBlock::Unknown { raw_type, .. } = block {
+            if raw_type == "refusal" {
+                continue;
+            }
+            return Err(FormatError::LossyConversionBlocked {
+                source_format: source.as_str().to_string(),
+                target_format: target.as_str().to_string(),
+                field: "output[].type".to_string(),
+                reason: format!(
+                    "target format has no lossless mapping for unknown source output item type {raw_type:?}"
+                ),
+            });
+        }
+    }
+    Ok(())
+}
+
 fn validate_known_standard_request_root_fields(
     source: FormatId,
     target: FormatId,
@@ -3130,6 +3159,44 @@ mod tests {
         }
     }
 
+    #[test]
+    fn pure_openai_responses_request_same_format_preserves_raw_tools_and_roles() {
+        let body = json!({
+            "model": "gpt-source",
+            "input": [
+                {
+                    "type": "message",
+                    "role": "developer",
+                    "content": [{"type": "input_text", "text": "Use policy"}]
+                },
+                {"role": "user", "content": "hello"}
+            ],
+            "tools": [
+                {
+                    "type": "file_search",
+                    "vector_store_ids": ["vs_123"],
+                    "max_num_results": 3
+                },
+                {
+                    "type": "mcp",
+                    "server_label": "docs",
+                    "server_url": "https://example.com/mcp"
+                }
+            ]
+        });
+
+        let converted = convert_request_pure("openai:responses", "openai:responses", &body)
+            .expect("same-format Responses request should preserve official raw fields")
+            .value;
+
+        assert_eq!(converted["input"][0]["role"], "developer");
+        assert_eq!(converted["input"][0]["content"][0]["text"], "Use policy");
+        assert_eq!(converted["tools"][0]["type"], "file_search");
+        assert_eq!(converted["tools"][0]["vector_store_ids"][0], "vs_123");
+        assert_eq!(converted["tools"][1]["type"], "mcp");
+        assert_eq!(converted["tools"][1]["server_label"], "docs");
+    }
+
     #[test]
     fn pure_openai_chat_to_claude_blocks_target_unsupported_generation_field() {
         let body = json!({
@@ -3453,6 +3520,72 @@ mod tests {
         );
     }
 
+    #[test]
+    fn pure_openai_responses_response_same_format_preserves_raw_output_items() {
+        let body = json!({
+            "id": "resp_raw_items",
+            "object": "response",
+            "model": "gpt-source",
+            "status": "completed",
+            "output": [
+                {
+                    "type": "file_search_call",
+                    "id": "fs_123",
+                    "status": "completed",
+                    "queries": ["rust"],
+                    "results": [{"file_id": "file_123", "text": "Rust"}]
+                },
+                {
+                    "type": "code_interpreter_call",
+                    "id": "ci_123",
+                    "status": "completed",
+                    "code": "print('hi')",
+                    "outputs": []
+                },
+                {
+                    "type": "message",
+                    "id": "msg_123",
+                    "role": "assistant",
+                    "content": [{"type": "output_text", "text": "done"}]
+                }
+            ]
+        });
+
+        let converted = convert_response_pure("openai:responses", "openai:responses", &body)
+            .expect("same-format Responses response should preserve raw output items")
+            .value;
+
+        assert_eq!(converted["output"][0]["type"], "file_search_call");
+        assert_eq!(converted["output"][0]["results"][0]["file_id"], "file_123");
+        assert_eq!(converted["output"][1]["type"], "code_interpreter_call");
+        assert_eq!(converted["output"][2]["content"][0]["text"], "done");
+    }
+
+    #[test]
+    fn pure_openai_responses_response_cross_format_blocks_raw_output_items() {
+        let body = json!({
+            "id": "resp_raw_items",
+            "object": "response",
+            "model": "gpt-source",
+            "status": "completed",
+            "output": [{
+                "type": "mcp_call",
+                "id": "mcp_123",
+                "status": "completed",
+                "name": "lookup"
+            }]
+        });
+
+        let error = convert_response_pure("openai:responses", "openai:chat", &body)
+            .expect_err("cross-format raw Responses output items should fail closed");
+
+        assert!(matches!(
+            error,
+            super::FormatError::LossyConversionBlocked { ref field, .. }
+                if field == "output[].type"
+        ));
+    }
+
     #[test]
     fn pure_claude_response_same_format_preserves_unknown_stop_reason() {
         let body = json!({

crates/aether-ai-formats/src/formats/shared/sync_products.rs

@@ -1974,7 +1974,7 @@ pub fn aggregate_openai_responses_stream_sync_response(body: &[u8]) -> Option<Va
                         reasoning_states.entry(output_index).or_default(),
                         item,
                     ),
-                    "function_call" => {
+                    "function_call" | "custom_tool_call" => {
                         merge_openai_responses_tool_item(
                             tool_states.entry(output_index).or_default(),
                             item,
@@ -1991,7 +1991,7 @@ pub fn aggregate_openai_responses_stream_sync_response(body: &[u8]) -> Option<Va
                     _ => {}
                 }
             }
-            "response.function_call_arguments.delta" => {
+            "response.function_call_arguments.delta" | "response.custom_tool_call_input.delta" => {
                 let Some(output_index) =
                     resolve_openai_responses_tool_output_index(event_object, &item_output_indexes)
                 else {
@@ -2004,18 +2004,43 @@ pub fn aggregate_openai_responses_stream_sync_response(body: &[u8]) -> Option<Va
                 if delta.is_empty() {
                     continue;
                 }
-                tool_states
-                    .entry(output_index)
-                    .or_default()
-                    .arguments
-                    .push_str(delta);
+                let state = tool_states.entry(output_index).or_default();
+                if event_object
+                    .get("type")
+                    .and_then(Value::as_str)
+                    .is_some_and(|value| value.starts_with("response.custom_tool_call_input."))
+                {
+                    state
+                        .item
+                        .entry("type".to_string())
+                        .or_insert_with(|| Value::String("custom_tool_call".to_string()));
+                    if let Some(name) = event_object.get("name").and_then(Value::as_str) {
+                        state
+                            .item
+                            .entry("name".to_string())
+                            .or_insert_with(|| Value::String(name.to_string()));
+                    }
+                    if let Some(item_id) = event_object.get("item_id").and_then(Value::as_str) {
+                        state
+                            .item
+                            .entry("id".to_string())
+                            .or_insert_with(|| Value::String(item_id.to_string()));
+                    }
+                    if let Some(call_id) = event_object.get("call_id").and_then(Value::as_str) {
+                        state
+                            .item
+                            .entry("call_id".to_string())
+                            .or_insert_with(|| Value::String(call_id.to_string()));
+                    }
+                }
+                state.arguments.push_str(delta);
                 register_openai_responses_tool_event_aliases(
                     &mut item_output_indexes,
                     event_object,
                     output_index,
                 );
             }
-            "response.function_call_arguments.done" => {
+            "response.function_call_arguments.done" | "response.custom_tool_call_input.done" => {
                 let Some(output_index) =
                     resolve_openai_responses_tool_output_index(event_object, &item_output_indexes)
                 else {
@@ -2032,14 +2057,44 @@ pub fn aggregate_openai_responses_stream_sync_response(body: &[u8]) -> Option<Va
                         item,
                     );
                 }
+                if event_object
+                    .get("type")
+                    .and_then(Value::as_str)
+                    .is_some_and(|value| value.starts_with("response.custom_tool_call_input."))
+                {
+                    let state = tool_states.entry(output_index).or_default();
+                    state
+                        .item
+                        .entry("type".to_string())
+                        .or_insert_with(|| Value::String("custom_tool_call".to_string()));
+                    if let Some(name) = event_object.get("name").and_then(Value::as_str) {
+                        state
+                            .item
+                            .entry("name".to_string())
+                            .or_insert_with(|| Value::String(name.to_string()));
+                    }
+                    if let Some(item_id) = event_object.get("item_id").and_then(Value::as_str) {
+                        state
+                            .item
+                            .entry("id".to_string())
+                            .or_insert_with(|| Value::String(item_id.to_string()));
+                    }
+                    if let Some(call_id) = event_object.get("call_id").and_then(Value::as_str) {
+                        state
+                            .item
+                            .entry("call_id".to_string())
+                            .or_insert_with(|| Value::String(call_id.to_string()));
+                    }
+                }
                 let arguments = event_object
                     .get("arguments")
+                    .or_else(|| event_object.get("input"))
                     .and_then(Value::as_str)
                     .or_else(|| {
                         event_object
                             .get("item")
                             .and_then(Value::as_object)
-                            .and_then(|item| item.get("arguments"))
+                            .and_then(|item| item.get("arguments").or_else(|| item.get("input")))
                             .and_then(Value::as_str)
                     })
                     .unwrap_or_default();
@@ -2076,7 +2131,7 @@ pub fn aggregate_openai_responses_stream_sync_response(body: &[u8]) -> Option<Va
                                 reasoning_states.entry(output_index).or_default(),
                                 item,
                             ),
-                            "function_call" => {
+                            "function_call" | "custom_tool_call" => {
                                 merge_openai_responses_tool_item(
                                     tool_states.entry(output_index).or_default(),
                                     item,
@@ -2644,6 +2699,12 @@ fn materialize_openai_responses_tool_item(
     state: OpenAIResponsesSyncToolState,
 ) -> Value {
     let mut item = state.item;
+    let item_type = item
+        .get("type")
+        .and_then(Value::as_str)
+        .filter(|value| *value == "custom_tool_call")
+        .unwrap_or("function_call")
+        .to_string();
     let generated_id = format!("call_auto_{output_index}");
     let call_id = item
         .get("call_id")
@@ -2660,10 +2721,7 @@ fn materialize_openai_responses_tool_item(
         })
         .unwrap_or(generated_id.clone());
 
-    item.insert(
-        "type".to_string(),
-        Value::String("function_call".to_string()),
-    );
+    item.insert("type".to_string(), Value::String(item_type.clone()));
     item.entry("id".to_string())
         .or_insert_with(|| Value::String(call_id.clone()));
     item.insert("call_id".to_string(), Value::String(call_id));
@@ -2672,9 +2730,19 @@ fn materialize_openai_responses_tool_item(
     item.entry("status".to_string())
         .or_insert_with(|| Value::String("completed".to_string()));
     if !state.arguments.is_empty() {
-        item.insert("arguments".to_string(), Value::String(state.arguments));
+        let argument_key = if item_type == "custom_tool_call" {
+            "input"
+        } else {
+            "arguments"
+        };
+        item.insert(argument_key.to_string(), Value::String(state.arguments));
     } else {
-        item.entry("arguments".to_string())
+        let argument_key = if item_type == "custom_tool_call" {
+            "input"
+        } else {
+            "arguments"
+        };
+        item.entry(argument_key.to_string())
             .or_insert_with(|| Value::String(String::new()));
     }
     Value::Object(item)
@@ -4289,6 +4357,27 @@ mod tests {
         assert_eq!(result["output"][0]["arguments"], r#"{"location": "Tokyo"}"#);
     }
 
+    #[test]
+    fn custom_tool_call_input_events_materialize_custom_tool_call() {
+        let body = concat!(
+            "event: response.custom_tool_call_input.delta\n",
+            "data: {\"type\":\"response.custom_tool_call_input.delta\",\"output_index\":0,\"item_id\":\"ctc_123\",\"name\":\"code_exec\",\"delta\":\"print\"}\n\n",
+            "event: response.custom_tool_call_input.done\n",
+            "data: {\"type\":\"response.custom_tool_call_input.done\",\"output_index\":0,\"item_id\":\"ctc_123\",\"call_id\":\"call_custom_123\",\"name\":\"code_exec\",\"input\":\"print('hi')\"}\n\n",
+            "event: response.completed\n",
+            "data: {\"type\":\"response.completed\",\"response\":{\"id\":\"resp_custom_123\",\"object\":\"response\",\"model\":\"gpt-5\",\"status\":\"completed\",\"output\":[]}}\n\n",
+        );
+
+        let result = aggregate_openai_responses_stream_sync_response(body.as_bytes())
+            .expect("custom tool stream should aggregate into a sync body");
+
+        assert_eq!(result["output"][0]["type"], "custom_tool_call");
+        assert_eq!(result["output"][0]["call_id"], "call_custom_123");
+        assert_eq!(result["output"][0]["name"], "code_exec");
+        assert_eq!(result["output"][0]["input"], "print('hi')");
+        assert!(result["output"][0].get("arguments").is_none());
+    }
+
     #[test]
     fn aggregates_modern_reasoning_text_and_response_done_alias() {
         let body = concat!(

crates/aether-ai-formats/src/protocol/canonical.rs

@@ -22,6 +22,8 @@ const OPENAI_CUSTOM_TOOL_CALL_SOURCE_MARKER: &str = "openai_custom_tool_call";
 const OPENAI_OUTPUT_AUDIO_SOURCE_MARKER: &str = "openai_output_audio";
 const OPENAI_CHAT_TOOL_RESULT_SOURCE_MARKER: &str = "openai_chat_tool_result";
 const OPENAI_RESPONSES_TOOL_RESULT_SOURCE_MARKER: &str = "openai_responses_tool_result";
+const OPENAI_RESPONSES_INPUT_MESSAGE_SOURCE_MARKER: &str = "openai_responses_input_message";
+const OPENAI_RESPONSES_RAW_SOURCE_MARKER: &str = "openai_responses_raw";
 const OPENAI_CHAT_TOOL_ERROR_PREFIX: &str = "[tool error]";
 
 #[derive(Debug, Clone, Default, PartialEq, Eq, Serialize, Deserialize)]
@@ -1879,16 +1881,18 @@ pub(crate) fn openai_responses_input_to_canonical_messages(
                         if matches!(role, CanonicalRole::System | CanonicalRole::Developer) {
                             let text = openai_content_text(item_object.get("content"));
                             if !text.trim().is_empty() {
+                                let mut extensions = openai_responses_extensions(
+                                    item_object,
+                                    &["type", "role", "content"],
+                                );
+                                mark_openai_responses_input_message(&mut extensions);
                                 messages.push(CanonicalMessage {
                                     role,
                                     content: vec![CanonicalContentBlock::Text {
                                         text,
                                         extensions: BTreeMap::new(),
                                     }],
-                                    extensions: openai_responses_extensions(
-                                        item_object,
-                                        &["type", "role", "content"],
-                                    ),
+                                    extensions,
                                 });
                             }
                             pending_reasoning = None;
@@ -2235,7 +2239,7 @@ pub(crate) fn openai_responses_output_to_canonical_blocks(
             blocks.push(CanonicalContentBlock::Unknown {
                 raw_type: String::new(),
                 payload: item.clone(),
-                extensions: BTreeMap::new(),
+                extensions: openai_responses_raw_extensions(BTreeMap::new()),
             });
             continue;
         };
@@ -2306,7 +2310,7 @@ pub(crate) fn openai_responses_output_to_canonical_blocks(
                     blocks.push(CanonicalContentBlock::Unknown {
                         raw_type: item_type,
                         payload: item.clone(),
-                        extensions: BTreeMap::new(),
+                        extensions: openai_responses_raw_extensions(BTreeMap::new()),
                     });
                 }
             }
@@ -2466,7 +2470,7 @@ pub(crate) fn openai_responses_output_to_canonical_blocks(
             _ => blocks.push(CanonicalContentBlock::Unknown {
                 raw_type: item_type,
                 payload: item.clone(),
-                extensions: BTreeMap::new(),
+                extensions: openai_responses_raw_extensions(BTreeMap::new()),
             }),
         }
     }
@@ -3207,6 +3211,16 @@ fn claude_raw_extensions(mut extensions: BTreeMap<String, Value>) -> BTreeMap<St
     extensions
 }
 
+fn openai_responses_raw_extensions(
+    mut extensions: BTreeMap<String, Value>,
+) -> BTreeMap<String, Value> {
+    canonical_extension_object_mut(&mut extensions, AETHER_EXTENSION_NAMESPACE).insert(
+        "source".to_string(),
+        Value::String(OPENAI_RESPONSES_RAW_SOURCE_MARKER.to_string()),
+    );
+    extensions
+}
+
 fn openai_thinking_extensions(mut extensions: BTreeMap<String, Value>) -> BTreeMap<String, Value> {
     canonical_extension_object_mut(&mut extensions, AETHER_EXTENSION_NAMESPACE).insert(
         "source".to_string(),
@@ -3229,6 +3243,13 @@ fn mark_openai_output_audio(extensions: &mut BTreeMap<String, Value>) {
     );
 }
 
+fn mark_openai_responses_input_message(extensions: &mut BTreeMap<String, Value>) {
+    canonical_extension_object_mut(extensions, AETHER_EXTENSION_NAMESPACE).insert(
+        "source".to_string(),
+        Value::String(OPENAI_RESPONSES_INPUT_MESSAGE_SOURCE_MARKER.to_string()),
+    );
+}
+
 pub(crate) fn is_claude_thinking_block(extensions: &BTreeMap<String, Value>) -> bool {
     extensions
         .get(AETHER_EXTENSION_NAMESPACE)
@@ -3245,6 +3266,22 @@ fn is_claude_raw_block(extensions: &BTreeMap<String, Value>) -> bool {
         == Some(CLAUDE_RAW_SOURCE_MARKER)
 }
 
+pub(crate) fn is_openai_responses_raw_block(extensions: &BTreeMap<String, Value>) -> bool {
+    extensions
+        .get(AETHER_EXTENSION_NAMESPACE)
+        .and_then(|value| value.get("source"))
+        .and_then(Value::as_str)
+        == Some(OPENAI_RESPONSES_RAW_SOURCE_MARKER)
+}
+
+pub(crate) fn is_openai_responses_input_message(extensions: &BTreeMap<String, Value>) -> bool {
+    extensions
+        .get(AETHER_EXTENSION_NAMESPACE)
+        .and_then(|value| value.get("source"))
+        .and_then(Value::as_str)
+        == Some(OPENAI_RESPONSES_INPUT_MESSAGE_SOURCE_MARKER)
+}
+
 pub(crate) fn is_openai_thinking_block(extensions: &BTreeMap<String, Value>) -> bool {
     extensions
         .get(AETHER_EXTENSION_NAMESPACE)
@@ -4542,6 +4579,26 @@ pub(crate) fn openai_responses_tools_to_canonical(
                     tool.clone(),
                 )]),
             });
+        } else {
+            let name = tool_object
+                .get("name")
+                .and_then(Value::as_str)
+                .map(str::trim)
+                .filter(|value| !value.is_empty())
+                .unwrap_or(tool_type.as_str());
+            canonical.push(CanonicalToolDefinition {
+                name: name.to_string(),
+                description: tool_object
+                    .get("description")
+                    .and_then(Value::as_str)
+                    .map(ToOwned::to_owned),
+                parameters: None,
+                strict: None,
+                extensions: BTreeMap::from([(
+                    OPENAI_RESPONSES_EXTENSION_NAMESPACE.to_string(),
+                    tool.clone(),
+                )]),
+            });
         }
     }
     Some(canonical)