Add prompt-caching placeholder for OpenRouter SDK

- Add typescript/openrouter-sdk/src/prompt-caching/README.md
- Placeholder for future @openrouter/sdk examples
- Will follow same pattern as other SDKs (separate files per scenario)

Author: subtleGradient

docs/prompt-caching.md

@@ -190,3 +190,4 @@ See ecosystem-specific examples:
 - **TypeScript + fetch**: [typescript/fetch/src/prompt-caching/](../typescript/fetch/src/prompt-caching/)
 - **AI SDK v5** (Vercel): [typescript/ai-sdk-v5/src/prompt-caching/](../typescript/ai-sdk-v5/src/prompt-caching/)
 - **Effect AI** (@effect/ai): [typescript/effect-ai/src/prompt-caching/](../typescript/effect-ai/src/prompt-caching/)
+- **OpenRouter SDK** (@openrouter/sdk): [typescript/openrouter-sdk/src/prompt-caching/](../typescript/openrouter-sdk/src/prompt-caching/)

typescript/openrouter-sdk/README.md

@@ -0,0 +1,16 @@
+# OpenRouter TypeScript SDK Examples
+
+Examples using the official @openrouter/sdk package.
+
+## Status
+
+**TODO**: Examples not yet implemented
+
+## Prerequisites
+
+- Bun runtime: `curl -fsSL https://bun.sh/install | bash`
+- `OPENROUTER_API_KEY` environment variable
+
+## Planned Features
+
+- [ ] prompt-caching.ts - Anthropic caching with OpenRouter SDK

typescript/openrouter-sdk/package.json

@@ -0,0 +1,15 @@
+{
+  "name": "@openrouter-examples/openrouter-sdk",
+  "version": "1.0.0",
+  "private": true,
+  "type": "module",
+  "scripts": {
+    "examples": "echo 'TODO: OpenRouter SDK examples not yet implemented'"
+  },
+  "dependencies": {
+    "@openrouter-examples/shared": "workspace:*"
+  },
+  "devDependencies": {
+    "@types/bun": "latest"
+  }
+}

typescript/openrouter-sdk/src/prompt-caching/README.md

@@ -0,0 +1,27 @@
+# Anthropic Prompt Caching Examples (OpenRouter SDK)
+
+**TODO**: Add prompt caching examples using the @openrouter/sdk package.
+
+This directory will contain examples demonstrating Anthropic's prompt caching feature via the OpenRouter TypeScript SDK.
+
+## Placeholder
+
+Examples will be added in a future commit.
+
+## Expected Structure
+
+```
+prompt-caching/
+├── README.md                        # This file
+├── system-message-cache.ts         # TODO: Cache on system message
+├── user-message-cache.ts           # TODO: Cache on user message
+├── multi-message-cache.ts          # TODO: Cache in conversation
+└── no-cache-control.ts             # TODO: Control scenario
+```
+
+## Pattern (To Be Implemented)
+
+The examples will use the official @openrouter/sdk package to demonstrate:
+- How to configure cache_control with the SDK
+- Where cache metrics appear in responses
+- Evidence-based verification of cache behavior

typescript/package.json

@@ -13,7 +13,8 @@
     "shared",
     "fetch",
     "ai-sdk-v5",
-    "effect-ai"
+    "effect-ai",
+    "openrouter-sdk"
   ],
   "devDependencies": {
     "@types/bun": "latest",