Fix: LangChain systemPrompt param + add missing @types deps + unblock Python Agent Framework startup

[Yogeshp-MSFT]

Issue 1: Nodejs LangChain Quickstart Build Error

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Problem
The LangChain Quickstart agent build command displays error due to an incorrect parameter name used in the createAgent API.

In client.ts (line 37), the parameter instructions is passed to createAgent
The LangChain API expects the parameter to be named systemPrompt

This mismatch causes a build error during agent initialization.
Additionally, the package.json file is missing required TypeScript type definitions for Express and Node.js, which results in TypeScript compilation errors.

Fix
Updated the createAgent API call to use systemPrompt instead of instructions
Added the following missing dev dependencies to package.json:

@types/express: ^5.0.6
@types/node: ^25.2.3

Evidence

Issue 2: Nodejs Devin Sample Build Error

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Problem
The Devin sample agent build command reports TypeScript errors due to missing type definitions for Express and Node.js.
The following dev dependencies were not present in the sample’s package.json:

@types/express
@types/node

This results in build‑time errors when running the project.

Fix
Added the required TypeScript type definitions to devDependencies:

@types/express: ^5.0.6
@types/node: ^25.2.3

Evidence

Issue 3: Python Agent-framework not running

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Problem
The agent-framework-core package exports Agent but does not export ChatAgent.
However, microsoft-agents-a365-tooling-extensions-agentframework expects ChatAgent to exist in the module.
This causes a failure in agent.py at line 40, where the extension attempts to reference/import ChatAgent.

Incorrect constructor argument passed to ChatAgent
The ChatAgent constructor is being called with chat_client instead of the expected parameter name client.

Fix

• Added a temporary import patch in agent.py to alias Agent as ChatAgent, resolving a mismatch where agent-framework-core does not export ChatAgent but the tooling extension expects it.
• Fixed an incorrect constructor invocation by renaming the keyword argument from chat_client to client, which was causing TypeError: Agent.init() missing 1 required positional argument: 'client'.
• These changes unblock agent initialization and allow the Python agent server to start successfully.

Evidence

Testing

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Verified all three samples using Agents Playground.

fixes #221

[Copilot]

Pull request overview

This pull request fixes critical build and runtime issues in three sample agents caused by API changes in their respective frameworks. The PR addresses a LangChain API parameter name mismatch, adds missing TypeScript type definitions to Node.js samples, and implements a workaround for breaking changes in the Python Agent Framework.

Changes:

• Fixed LangChain createAgent API call to use systemPrompt instead of incorrect instructions parameter
• Added missing TypeScript type definitions (@types/express and @types/node) to langchain/quickstart-before and devin samples
• Implemented import workaround for Python Agent Framework's ChatAgent removal and fixed constructor parameter name

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 6 comments.

File	Description
nodejs/langchain/quickstart-before/src/client.ts	Corrected parameter name from instructions to systemPrompt in createAgent call
nodejs/langchain/quickstart-before/package.json	Added @types/express and @types/node devDependencies for TypeScript compilation
nodejs/devin/sample-agent/package.json	Added @types/express and @types/node devDependencies for TypeScript compilation
python/agent-framework/sample-agent/agent.py	Added ChatAgent import workaround and fixed constructor parameter from chat_client to client

[Yogeshp-MSFT]

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