Add egress header template documentation

docs.json

@@ -148,7 +148,8 @@
                   "docs/template/examples/expo",
                   "docs/template/examples/desktop",
                   "docs/template/examples/claude-code",
-                  "docs/template/examples/docker"
+                  "docs/template/examples/docker",
+                  "docs/template/examples/egress-header"
                 ]
               },
               "docs/template/migration-v2"

docs/template/examples/egress-header.mdx

@@ -0,0 +1,65 @@
+---
+title: "Egress header"
+description: "Sandbox with automatic HTTP header injection on outbound requests"
+---
+
+This template automatically tags every outbound HTTP and HTTPS request from the sandbox with a custom header containing the sandbox ID. No code changes needed — any request your agent makes to external APIs will carry the `X-Sandbox-ID` header transparently.
+
+This enables you to:
+- **Track API usage per sandbox** — correlate external API calls back to the sandbox that made them
+- **Route traffic** — use the header in your API gateway or proxy to apply per-sandbox rate limits, logging, or access policies
+- **Audit agent behavior** — see exactly which external services each sandbox is calling
+
+## How it works
+
+A transparent proxy runs inside the sandbox and intercepts all outbound HTTP/HTTPS traffic. It injects an `X-Sandbox-ID` header into every request before forwarding it to the destination. The sandbox's CA certificate is automatically trusted so HTTPS works without any configuration in Python, Node.js, or any other runtime.
+
+Your code doesn't need to know the proxy exists — it works at the network level.
+
+## Usage
+
+Create a sandbox from the template. Every outbound request automatically includes the `X-Sandbox-ID` header.
+
+<CodeGroup>
+
+```typescript JavaScript & TypeScript
+import { Sandbox } from 'e2b'
+
+const sbx = await Sandbox.create('sandbox-egress-header', { timeoutMs: 120_000 })
+
+// Any outbound request from the sandbox will include X-Sandbox-ID
+const result = await sbx.commands.run('curl -s https://httpbin.org/headers')
+console.log(result.stdout)
+
+await sbx.kill()
+```
+
+```python Python
+from e2b import Sandbox
+
+sbx = Sandbox.create("sandbox-egress-header", timeout=120)
+
+# Any outbound request from the sandbox will include X-Sandbox-ID
+result = sbx.commands.run("curl -s https://httpbin.org/headers")
+print(result.stdout)
+
+sbx.kill()
+```
+
+</CodeGroup>
+
+The response from httpbin.org shows the injected header:
+
+```json
+{
+  "headers": {
+    "Accept": "*/*",
+    "Host": "httpbin.org",
+    "X-Sandbox-Id": "i3sb4m2knepruowf004y7"
+  }
+}
+```
+
+## Source code
+
+The full template source including the proxy addon, startup script, and build configuration is available on [GitHub](https://github.com/e2b-dev/template-examples).