Add prompt-caching examples for fetch API

.gitignore

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+node_modules/
+typescript/node_modules/
+typescript/*/node_modules/
+typescript/bun.lock
+*.log
+.DS_Store

Makefile

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+# Makefile - Root orchestration for openrouter-examples
+
+.PHONY: help examples typescript install clean
+
+help:
+	@echo "OpenRouter Examples - Available commands:"
+	@echo ""
+	@echo "  make examples         - Run all examples"
+	@echo "  make typescript       - Run TypeScript monorepo examples"
+	@echo "  make install          - Install TypeScript dependencies"
+	@echo "  make clean            - Clean node_modules and lockfiles"
+	@echo ""
+
+# Run all examples
+examples: typescript
+
+# Run TypeScript monorepo examples
+typescript:
+	@echo "=== Running TypeScript examples ==="
+	@cd typescript && bun examples
+
+# Install TypeScript dependencies
+install:
+	@echo "=== Installing TypeScript dependencies ==="
+	@cd typescript && bun install
+
+# Clean build artifacts
+clean:
+	@echo "=== Cleaning TypeScript artifacts ==="
+	@rm -rf typescript/node_modules
+	@rm -rf typescript/*/node_modules
+	@rm -rf typescript/bun.lock
+	@echo "Clean complete"

README.md

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+# OpenRouter Examples
+
+Comprehensive, tested, executable examples demonstrating OpenRouter features across multiple ecosystems.
+
+## Quick Start
+
+```bash
+# Set your API key
+export OPENROUTER_API_KEY="your-key-here"
+
+# Run all examples
+make examples
+
+# Or run specific ecosystems
+make curl          # Run curl examples
+make typescript    # Run TypeScript monorepo examples
+```
+
+## Repository Structure
+
+```
+.
+├── curl/              - Shell script examples
+├── typescript/        - TypeScript monorepo (Bun workspaces)
+│   ├── shared/        - Shared constants and types
+│   ├── fetch/         - Raw fetch API examples
+│   ├── ai-sdk-v5/     - Vercel AI SDK v5 examples
+│   ├── effect-ai/     - Effect-TS examples
+│   └── openrouter-sdk/ - OpenRouter SDK examples (TODO)
+├── docs/              - Feature documentation
+└── Makefile           - Unified command interface
+```
+
+## Features
+
+### Prompt Caching
+- **Documentation**: [docs/prompt-caching.md](docs/prompt-caching.md)
+- **Examples**:
+  - [curl/prompt-caching.sh](curl/prompt-caching.sh)
+  - [typescript/fetch/src/prompt-caching/](typescript/fetch/src/prompt-caching/)
+  - [typescript/ai-sdk-v5/src/prompt-caching/](typescript/ai-sdk-v5/src/prompt-caching/)
+  - [typescript/effect-ai/src/prompt-caching/](typescript/effect-ai/src/prompt-caching/)
+
+## Prerequisites
+
+- Bun runtime: `curl -fsSL https://bun.sh/install | bash`
+- OpenRouter API key: [https://openrouter.ai/keys](https://openrouter.ai/keys)
+- For curl examples: `jq` (JSON processor)
+
+## Installation
+
+```bash
+# Install TypeScript dependencies
+make install
+
+# Or manually
+cd typescript && bun install
+```
+
+## Running Examples
+
+### All Examples
+```bash
+make examples
+```
+
+### By Ecosystem
+```bash
+make curl          # Shell scripts with curl + jq
+make typescript    # All TypeScript examples (fetch, AI SDK, Effect)
+```
+
+### Individual Examples
+```bash
+# curl
+bash curl/prompt-caching.sh
+
+# TypeScript
+cd typescript/fetch && bun examples
+cd typescript/ai-sdk-v5 && bun examples
+cd typescript/effect-ai && bun examples
+```
+
+## Benefits
+
+### For Users
+1. **Copy-paste ready** - All examples are runnable as-is
+2. **Tested and proven** - Every example has been verified to work
+3. **Evidence-based** - Examples show expected outputs and verification
+4. **Multiple ecosystems** - Choose the one that matches your stack
+
+### For Developers
+1. **Single source of truth** - Constants defined once in `typescript/shared/`
+2. **Type safety** - Shared types across all TypeScript examples
+3. **Consistent patterns** - Each ecosystem follows its own idioms
+4. **Easy maintenance** - Bun monorepo for TypeScript workspaces
+
+## Contributing
+
+See individual ecosystem READMEs:
+- [curl/README.md](curl/README.md)
+- [typescript/README.md](typescript/README.md)
+
+## License
+
+See [LICENSE.md](LICENSE.md)

biome.jsonc

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+{
+  "$schema": "https://biomejs.dev/schemas/2.3.3/schema.json",
+  "vcs": {
+    "enabled": true,
+    "clientKind": "git",
+    "useIgnoreFile": true
+  },
+  "files": {
+    "ignoreUnknown": false,
+    "ignore": [
+      "**/*.json",
+      "!biome.json"
+    ]
+  },
+  "formatter": {
+    "enabled": true,
+    "indentStyle": "space",
+    "indentWidth": 2,
+    "lineWidth": 100,
+    "attributePosition": "multiline"
+  },
+  "organizeImports": {
+    "enabled": true
+  },
+  "linter": {
+    "enabled": true,
+    "rules": {
+      "recommended": true,
+      "complexity": {
+        "useLiteralKeys": "off",
+        "noExtraBooleanCast": "off",
+        "noForEach": "off",
+        "noBannedTypes": "error",
+        "noUselessSwitchCase": "off"
+      },
+      "style": {
+        "noNonNullAssertion": "off",
+        "useNodejsImportProtocol": "off",
+        "useTemplate": "off",
+        "useBlockStatements": "error",
+        "noParameterAssign": "error",
+        "useConst": "error",
+        "useAsConstAssertion": "error",
+        "useDefaultParameterLast": "error",
+        "useEnumInitializers": "error",
+        "useSelfClosingElements": "error",
+        "useSingleVarDeclarator": "error",
+        "noUnusedTemplateLiteral": "error",
+        "useNumberNamespace": "error",
+        "noInferrableTypes": "error",
+        "noUselessElse": "error",
+        "useImportType": "error"
+      },
+      "correctness": {
+        "noUnusedImports": "error",
+        "useExhaustiveDependencies": "off",
+        "noUnknownFunction": "off",
+        "noChildrenProp": "off",
+        "noInnerDeclarations": "error"
+      },
+      "suspicious": {
+        "noExplicitAny": "error",
+        "noArrayIndexKey": "off",
+        "noAssignInExpressions": "error",
+        "noAsyncPromiseExecutor": "off",
+        "noFallthroughSwitchClause": "error",
+        "noConsole": "off",
+        "noDoubleEquals": {
+          "level": "error",
+          "options": {
+            "ignoreNull": false
+          }
+        },
+        "noExtraNonNullAssertion": "error"
+      },
+      "performance": {
+        "recommended": true,
+        "noAccumulatingSpread": "error"
+      },
+      "security": {
+        "recommended": true
+      }
+    }
+  },
+  "javascript": {
+    "formatter": {
+      "lineWidth": 100,
+      "arrowParentheses": "always",
+      "jsxQuoteStyle": "single",
+      "attributePosition": "multiline",
+      "quoteProperties": "asNeeded",
+      "trailingCommas": "all",
+      "semicolons": "always",
+      "bracketSpacing": true,
+      "bracketSameLine": false,
+      "quoteStyle": "single"
+    }
+  }
+}

docs/prompt-caching.md

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+# Prompt Caching
+
+OpenRouter maintains the canonical documentation for prompt caching at:
+
+- **[OpenRouter Prompt Caching Guide](https://openrouter.ai/docs/features/prompt-caching)**
+
+That guide covers provider-specific behavior, pricing, configuration requirements, and up-to-date usage examples. This repository intentionally links out to avoid duplicating content that can drift from production behavior.
+
+## Examples
+
+See ecosystem-specific examples in this repository for runnable reference implementations:
+
+- **TypeScript + fetch**: [typescript/fetch/src/prompt-caching/](../typescript/fetch/src/prompt-caching/)

typescript/README.md

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+# TypeScript Examples
+
+A Bun monorepo containing OpenRouter examples across different TypeScript ecosystems.
+
+## Structure
+
+- **shared/** - Shared constants and utilities (LARGE_SYSTEM_PROMPT, types, etc.)
+- **fetch/** - Raw fetch API examples
+- **ai-sdk-v5/** - Vercel AI SDK v5 examples (using ai v4.x package)
+- **effect-ai/** - Effect-TS AI examples
+- **openrouter-sdk/** - OpenRouter TypeScript SDK examples (TODO)
+
+## Prerequisites
+
+- Bun runtime: `curl -fsSL https://bun.sh/install | bash`
+- `OPENROUTER_API_KEY` environment variable
+
+## Installation
+
+```bash
+# From repository root
+make install
+
+# Or from the typescript/ directory
+cd typescript
+bun install
+```
+
+## Running Examples
+
+```bash
+# From repository root
+export OPENROUTER_API_KEY="your-key-here"
+make typescript
+
+# Or from the typescript/ directory
+cd typescript
+bun examples
+
+# Or run individual workspaces
+cd fetch && bun examples
+cd ai-sdk-v5 && bun examples
+cd effect-ai && bun examples
+```
+
+## Workspace Benefits
+
+1. **Shared constants** - LARGE_SYSTEM_PROMPT defined once in `shared/`
+2. **Consistent dependencies** - Managed at monorepo root with Bun workspaces
+3. **Type sharing** - Common types available across workspaces
+4. **Easy testing** - Run all examples from one location with `make typescript` or `bun examples`

typescript/fetch/README.md

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+# TypeScript + fetch Examples
+
+Raw HTTP examples using TypeScript and the native `fetch` API.
+
+## Prerequisites
+
+- Bun runtime: `curl -fsSL https://bun.sh/install | bash`
+- `OPENROUTER_API_KEY` environment variable
+
+## Running Examples
+
+```bash
+# From monorepo root (typescript/)
+bun examples
+
+# Or from this workspace
+cd fetch
+bun examples
+```
+
+## Features
+
+- [prompt-caching](./src/prompt-caching/) - Anthropic caching examples
+
+## Dependencies
+
+- `@openrouter-examples/shared` - Shared constants (LARGE_SYSTEM_PROMPT) and types

typescript/fetch/package.json

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+{
+  "name": "@openrouter-examples/fetch",
+  "version": "1.0.0",
+  "private": true,
+  "type": "module",
+  "scripts": {
+    "examples": "bun run run-examples.ts",
+    "typecheck": "tsc --noEmit"
+  },
+  "dependencies": {
+    "@openrouter-examples/shared": "workspace:*"
+  },
+  "devDependencies": {
+    "@types/bun": "1.3.2"
+  }
+}