fix: restructure existing agent patterns and fix bugs

Author: razkenari

frontend/src/lib/agentcore-client/parsers/langgraph.ts

@@ -6,20 +6,19 @@ import type { ChunkParser } from "../types"
 /**
  * Parses SSE chunks from LangGraph agents (stream_mode="messages").
  *
- * Each SSE line is a model_dump() of either AIMessageChunk or ToolMessage.
+ * Uses LangChain's normalized message fields — works with any ChatModel backend.
  *
- * AIMessageChunk shapes:
- *   - text:       content: [{type:"text", text:"...", index:N}]
- *   - tool start: content: [{type:"tool_use", id, name, input:{}, index:N}]  + tool_calls[]
- *   - tool delta: content: [{type:"tool_use", partial_json:"...", index:N}]   + tool_call_chunks[]
- *   - stop:       response_metadata: {stop_reason:"end_turn"|"tool_use"}
- *   - last:       chunk_position: "last"
- *
- * ToolMessage shape:
- *   - type: "tool", content: "result", name: "tool_name", tool_call_id: "id"
+ * Stream format:
+ *   AIMessageChunk:
+ *     - text:        content (string)
+ *     - tool start:  tool_call_chunks[{id, name, args}]  — first chunk has id + name
+ *     - tool delta:  tool_call_chunks[{args}]             — subsequent chunks have args only
+ *     - stop:        response_metadata.stop_reason
+ *   ToolMessage:
+ *     - type: "tool", content: string, tool_call_id: string
  */
 
-// Track current tool_use_id across chunks (deltas don't carry the id)
+// Track current tool_use_id — streaming deltas may omit the id
 let currentToolUseId = ""
 
 export const parseLanggraphChunk: ChunkParser = (line, callback) => {
@@ -43,39 +42,29 @@ export const parseLanggraphChunk: ChunkParser = (line, callback) => {
 
     // AIMessageChunk
     if (json.type === "AIMessageChunk") {
-      // Content as plain string (when model responds without tool use)
+      // Text token — content can be a string or array of text blocks
       if (typeof json.content === "string" && json.content) {
         callback({ type: "text", content: json.content })
-      }
-
-      // Content as array of blocks (when model uses tools)
-      if (Array.isArray(json.content)) {
+      } else if (Array.isArray(json.content)) {
         for (const block of json.content) {
-          // Text token
           if (block.type === "text" && block.text) {
             callback({ type: "text", content: block.text })
           }
+        }
+      }
 
-          // Tool use start — has id and name
-          if (block.type === "tool_use" && block.id && block.name) {
-            currentToolUseId = block.id
-            callback({
-              type: "tool_use_start",
-              toolUseId: block.id,
-              name: block.name,
-            })
+      // Tool calls — streamed via tool_call_chunks (LangChain's standard streaming field)
+      if (Array.isArray(json.tool_call_chunks)) {
+        for (const chunk of json.tool_call_chunks) {
+          if (chunk.id && chunk.name) {
+            currentToolUseId = chunk.id
+            callback({ type: "tool_use_start", toolUseId: chunk.id, name: chunk.name })
           }
-
-          // Tool input streaming — has partial_json
-          if (
-            block.type === "tool_use" &&
-            typeof block.partial_json === "string" &&
-            block.partial_json
-          ) {
+          if (typeof chunk.args === "string" && chunk.args) {
             callback({
               type: "tool_use_delta",
-              toolUseId: currentToolUseId,
-              input: block.partial_json,
+              toolUseId: chunk.id || currentToolUseId,
+              input: chunk.args,
             })
           }
         }

infra-cdk/config.yaml

@@ -5,7 +5,13 @@ stack_name_base: FAST-stack
 admin_user_email: # Example: admin@example.com
 
 backend:
-  pattern: strands-single-agent # Available patterns: strands-single-agent, langgraph-single-agent, claude-agent-sdk
+  pattern: strands-single-agent # See patterns/ for available options
+  # Pattern prefix determines the frontend parser:
+  #   agui-*      → AG-UI parser      (e.g. agui-strands-agent)
+  #   strands-*   → Strands parser    (e.g. strands-single-agent)
+  #   langgraph-* → LangGraph parser  (e.g. langgraph-single-agent)
+  #   claude-*    → Claude parser     (e.g. claude-agent-sdk-single-agent)
+  # The folder name must match exactly and start with the desired parser prefix.
   deployment_type: docker # Available deployment types: docker (default), zip (not supported for claude-agent-sdk)
   network_mode: PUBLIC # Available network modes: PUBLIC (default), VPC
 

patterns/__init__.py

@@ -1,26 +1,27 @@
 # Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
 # SPDX-License-Identifier: Apache-2.0
 
-from code_int_mcp.server import code_int_mcp_server
+import json
+import logging
+import os
+
+from agents.subagents import get_subagent_definitions
+from bedrock_agentcore.runtime import BedrockAgentCoreApp, RequestContext
 from claude_agent_sdk import (
     AssistantMessage,
-    UserMessage,
+    ClaudeAgentOptions,
+    ClaudeSDKClient,
+    ProcessError,
     ResultMessage,
     SystemMessage,
-    ClaudeAgentOptions,
     TextBlock,
-    ToolUseBlock,
-    ClaudeSDKClient,
     ToolResultBlock,
-    ProcessError,
+    ToolUseBlock,
+    UserMessage,
 )
-from bedrock_agentcore.runtime import BedrockAgentCoreApp, RequestContext
-from agents.subagents import get_subagent_definitions
+from code_int_mcp.server import code_int_mcp_server
 from utils.auth import extract_user_id_from_context, get_gateway_access_token
 from utils.ssm import get_ssm_parameter
-import logging
-import json
-import os
 
 logging.basicConfig(level=logging.INFO)
 logger = logging.getLogger(__name__)
@@ -49,7 +50,7 @@ async def main(payload, context: RequestContext):
         }
         return
 
-    code_int_session_id = payload.get("code_int_session_id", "")
+    _code_int_session_id = payload.get("code_int_session_id", "")
     claude_session_id = _session_map.get(runtime_session_id)
 
     # Extract user ID securely from validated JWT token
@@ -68,7 +69,9 @@ async def main(payload, context: RequestContext):
             gateway_url = get_ssm_parameter(f"/{stack_name}/gateway_url")
             access_token = get_gateway_access_token()
         except Exception as e:
-            logger.warning("[AGENT] Gateway not available, continuing without tools: %s", e)
+            logger.warning(
+                "[AGENT] Gateway not available, continuing without tools: %s", e
+            )
             gateway_url = None
             access_token = None
 
@@ -107,13 +110,28 @@ def _build_options(resume_id: str | None) -> ClaudeAgentOptions:
             mcp_servers=mcp_servers,
             model="us.anthropic.claude-opus-4-6-v1",
             allowed_tools=allowed_tools,
-            disallowed_tools=["Bash", "Write", "NotebookEdit", "Edit", "WebFetch", "Read", "Glob", "Grep", "EnterWorktree", "Skill", "TodoWrite", "CronCreate", "CronDelete", "CronList"],
+            disallowed_tools=[
+                "Bash",
+                "Write",
+                "NotebookEdit",
+                "Edit",
+                "WebFetch",
+                "Read",
+                "Glob",
+                "Grep",
+                "EnterWorktree",
+                "Skill",
+                "TodoWrite",
+                "CronCreate",
+                "CronDelete",
+                "CronList",
+            ],
             agents=subagents,
             resume=resume_id,
             thinking={"type": "adaptive"},
             cli_path="/usr/bin/claude",
             stderr=lambda line: logger.error("claude-code stderr: %s", line),
-            system_prompt=f"""You are an AI assistant that helps users with code execution and analysis tasks.
+            system_prompt="""You are an AI assistant that helps users with code execution and analysis tasks.
 
 CRITICAL RULES:
 1. You MUST use mcp__codeint__execute_code for ALL Python code execution tasks.
@@ -144,7 +162,9 @@ async def _process_messages(options: ClaudeAgentOptions):
             async for msg in client.receive_response():
                 if isinstance(msg, SystemMessage):
                     if msg.subtype == "init":
-                        logger.info("Claude session init: %s", msg.data.get("session_id"))
+                        logger.info(
+                            "Claude session init: %s", msg.data.get("session_id")
+                        )
                 elif isinstance(msg, AssistantMessage):
                     for block in msg.content:
                         if isinstance(block, ToolUseBlock):
@@ -153,7 +173,9 @@ async def _process_messages(options: ClaudeAgentOptions):
                                 "current_tool_use": {
                                     "name": block.name,
                                     "input": block.input,
-                                    "toolUseId": f"tool-{block.id}" if hasattr(block, "id") else f"tool-{hash(block.name)}",
+                                    "toolUseId": f"tool-{block.id}"
+                                    if hasattr(block, "id")
+                                    else f"tool-{hash(block.name)}",
                                 }
                             }
                         elif isinstance(block, TextBlock):
@@ -169,9 +191,11 @@ async def _process_messages(options: ClaudeAgentOptions):
                                     try:
                                         result_data = json.loads(text_content)
                                         if isinstance(result_data, dict):
-                                            extracted = result_data.get("code_int_session_id", "")
+                                            extracted = result_data.get(
+                                                "code_int_session_id", ""
+                                            )
                                             if extracted:
-                                                code_int_session_id = extracted
+                                                _code_int_session_id = extracted
                                     except json.JSONDecodeError:
                                         pass
                 elif isinstance(msg, ResultMessage):
@@ -185,7 +209,10 @@ async def _process_messages(options: ClaudeAgentOptions):
             yield event
     except ProcessError:
         if claude_session_id:
-            logger.warning("Resume failed for session %s, starting fresh session", claude_session_id)
+            logger.warning(
+                "Resume failed for session %s, starting fresh session",
+                claude_session_id,
+            )
             async for event in _process_messages(_build_options(None)):
                 yield event
         else:

patterns/claude-agent-sdk-multi-agent/agent.py

@@ -2,11 +2,13 @@
 # SPDX-License-Identifier: Apache-2.0
 
 import json
+import logging
 import os
 import time
+
 import boto3
 from botocore.exceptions import ClientError
-import logging
+
 from .models import CodeIntExecutionResult
 
 logging.basicConfig(level=logging.INFO)
@@ -17,7 +19,9 @@ class CodeInterpreterClient:
     """Client for AgentCore Code Interpreter."""
 
     def __init__(self, region_name: str = None):
-        region = region_name or os.environ.get("AWS_REGION", os.environ.get("AWS_DEFAULT_REGION", "us-east-1"))
+        region = region_name or os.environ.get(
+            "AWS_REGION", os.environ.get("AWS_DEFAULT_REGION", "us-east-1")
+        )
         self.ci_client = boto3.client("bedrock-agentcore", region_name=region)
 
     def _create_sessionid(self) -> str:

patterns/claude-agent-sdk-multi-agent/code_int_mcp/client.py

@@ -3,9 +3,10 @@
 
 """Data models for Code Interpreter."""
 
-from pydantic import BaseModel, Field
 from typing import Optional
 
+from pydantic import BaseModel, Field
+
 
 class CodeIntExecutionResult(BaseModel):
     """Result model for code execution."""

patterns/claude-agent-sdk-multi-agent/code_int_mcp/models.py

@@ -3,11 +3,13 @@
 
 """In-process MCP server for Code Interpreter."""
 
-from .client import CodeInterpreterClient
-from claude_agent_sdk import tool, create_sdk_mcp_server
-from typing import Any
 import json
 import logging
+from typing import Any
+
+from claude_agent_sdk import create_sdk_mcp_server, tool
+
+from .client import CodeInterpreterClient
 
 logger = logging.getLogger(__name__)