chore: import upstream snapshot with attribution

showcase/integrations/langgraph-python/src/agents/open_gen_ui_agent.py

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+"""Minimal LangGraph agent for the Open-Ended Generative UI demo.
+
+The simplest possible example that exercises the open-ended generative UI
+pipeline. All the interesting work happens outside the agent:
+
+- `CopilotKitMiddleware` merges the frontend-registered `generateSandboxedUi`
+  tool (auto-registered by `CopilotKitProvider` when the runtime has
+  `openGenerativeUI` enabled) into the agent's tool list. The LLM then sees
+  the tool via the normal AG-UI flow.
+- When the LLM calls `generateSandboxedUi`, the runtime's
+  `OpenGenerativeUIMiddleware` (enabled via `openGenerativeUI` on the
+  runtime — see `src/app/api/copilotkit-ogui/route.ts`) converts that
+  streaming tool call into `open-generative-ui` activity events that the
+  built-in renderer mounts inside a sandboxed iframe.
+
+This is the minimal variant: no sandbox functions, no app-side tools. The
+agent simply asks the LLM to design and emit a single-shot sandboxed UI.
+The "advanced" sibling (`open_gen_ui_advanced_agent.py`) builds on this
+with sandbox-to-host function calling via `openGenerativeUI.sandboxFunctions`.
+"""
+
+from __future__ import annotations
+
+from copilotkit import CopilotKitMiddleware
+from langchain.agents import create_agent
+from langchain_openai import ChatOpenAI
+
+
+SYSTEM_PROMPT = """You are a UI-generating assistant for an Open Generative UI demo
+focused on intricate, educational visualisations (3D axes / rotations,
+neural-network activations, sorting-algorithm walkthroughs, Fourier
+series, wave interference, planetary orbits, etc.).
+
+On every user turn you MUST call the `generateSandboxedUi` frontend tool
+exactly once. Design a visually polished, self-contained HTML + CSS +
+SVG widget that *teaches* the requested concept.
+
+The frontend injects a detailed "design skill" as agent context
+describing the palette, typography, labelling, and motion conventions
+expected — follow it closely. Key invariants:
+- Use inline SVG (or <canvas>) for geometric content, not stacks of <div>s.
+- Every axis is labelled; every colour-coded series has a legend.
+- Prefer CSS @keyframes / transitions over setInterval; loop cyclical
+  concepts with animation-iteration-count: infinite.
+- Motion must teach — animate the actual step of the concept, not decoration.
+- No fetch / XHR / localStorage — the sandbox has no same-origin access.
+
+Output order:
+- `initialHeight` (typically 480-560 for visualisations) first.
+- A short `placeholderMessages` array (2-3 lines describing the build).
+- `css` (complete).
+- `html` (streams live — keep it tidy). CDN <script> tags for Chart.js /
+  D3 / etc. go inside the html.
+
+Keep your own chat message brief (1 sentence) — the real output is the
+rendered visualisation.
+"""
+
+
+graph = create_agent(
+    model=ChatOpenAI(model="gpt-5.4", model_kwargs={"parallel_tool_calls": False}),
+    tools=[],
+    middleware=[CopilotKitMiddleware()],
+    system_prompt=SYSTEM_PROMPT,
+)