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TemplatesAgent Patterns
OpenAI Prompt Caching (AI Gateway)
OpenAI Prompt Caching (AI Gateway)
Lightweight ToolLoopAgent pattern for OpenAI prompt caching through Vercel AI Gateway: stable system instructions, promptCacheKey, and per-turn cachedPromptTokens metrics.
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Problems solved
Technical challenges this implementation handles out of the box.
- Enable OpenAI prompt caching with promptCacheKey via AI Gateway
- Reuse a stable system prefix across ToolLoopAgent turns
- Inspect cachedPromptTokens from provider metadata
Use cases
Products and workflows this pattern is designed to support.
- Lowering cost on repeated agent system prompts
- Teaching promptCacheKey grouping with ToolLoopAgent
- Comparing cache metrics across multi-turn sessions
Setup
Requirements, wiring steps, and what this pattern adds to your project.
Getting started
Pick how you want to pull this pattern in. Then wire env vars and routes the same way.
- 1
Download → Next.js app
Use Download → Next.js app in the preview toolbar. You get a zip scaffold (Pro downloads rewrite preview `/view/.../api/*` paths to `/api/*` automatically).
- 2
Extract the zip and install dependencies
Unzip the archive, then run `pnpm install` (or npm / yarn) in the project folder.
- 3
Fill .env.local
The download includes .env.local placeholders when needed. Add real values for: AI_GATEWAY_API_KEY.
- 4
Customize the agent and tool files
Adapt prompts, tools, and stop conditions in the generated project for your product.
- 5
Run the app and open the pattern route
Run `pnpm dev`, open the setup/checklist page if present, then navigate to the generated pattern route and verify responses.
Environment variables
AI_GATEWAY_API_KEYGet key
Capabilities
AI SDK APIs
ToolLoopAgentgatewayproviderOptionsstepCountIsProviders
OpenAI
Files added
8 filesapp/page.tsxapp/layout.tsxapp/api/cache-openai/route.tslib/cache-openai-agent.tslib/cache-metrics.tslib/stable-system-prompt.tslib/request-utils.tsREADME.md
Dependencies
9 totalnpm packages
5AISDKlucide-reactNext.jsReactZod
Registry components
alertbadgebuttonskeleton
Critical files
lib/cache-openai-agent.tsToolLoopAgent with gateway model, stable instructions, and providerOptions.openai.promptCacheKey.
cache-openai/route.tsRuns agent.generate({ messages }) and returns text plus cachedPromptTokens metrics.
Requirements
- Complexity
- Intermediate
- Setup time
- ~5 minutes
- Node
- 24+
- Memory
- 256MB
