docs: fill five sandbox lifecycle and template doc gaps (#284)

* docs: fill five sandbox lifecycle and template doc gaps

Close documentation gaps surfaced by customers:
- persistence: state on_timeout defaults to "kill"; expand paused-sandbox
  retention (indefinite, no auto-kill, explicit kill required)
- base-image: document base template default resources (2 vCPU, 512 MiB)
  and pre-installed tooling with a link to the public Dockerfile
- build: clarify disk size is tier-derived at build time, not a
  per-sandbox parameter
- lifecycle events API: document 7-day event retention
- lifecycle webhooks: document delivery retry policy and idempotency
- billing: fix stale default RAM (1 GB -> 512 MiB)

* docs: drop explicit-kill bullet from paused retention per review

* docs: reword paused-sandbox removal bullet (free -> remove)

Author: beran-t

docs/billing.mdx

@@ -96,7 +96,7 @@ Check your usage and costs in the [dashboard usage tab](https://e2b.dev/dashboar
     - **Enable auto-pause** - Automatically pause sandboxes after a period of inactivity to stop billing while preserving state
     - **Pause sandboxes when idle** - Use `sbx.pause()` to stop billing while keeping state available for later
     - **Kill sandboxes you no longer need** - Use `sbx.kill()` to stop billing and release resources permanently
-    - **Allocate only what you need** - Start with default resources (2 vCPU, 1 GB RAM) and increase only if necessary
+    - **Allocate only what you need** - Start with default resources (2 vCPU, 512 MiB RAM) and increase only if necessary
     - **Monitor actively running sandboxes** - Use the [CLI](/docs/cli/list-sandboxes) or [dashboard](https://e2b.dev/dashboard?tab=usage) to track active sandboxes
     - **Use lifecycle events** - Set up [webhooks](/docs/sandbox/lifecycle-events-webhooks) to get notified when sandboxes are created
   </Accordion>

docs/sandbox/lifecycle-events-api.mdx

@@ -6,6 +6,10 @@ sidebarTitle: Lifecycle events API
 The lifecycle API provides RESTful endpoints to request the latest sandbox lifecycle events. This allows you to track when sandboxes are created, paused, resumed, updated, snapshotted, or killed, along with metadata.
 All requests require authentication using your team [API key](/docs/api-key#where-to-find-api-key).
 
+## Retention
+
+Sandbox lifecycle events are retained for **7 days** by default. After the retention window passes, a sandbox's events are no longer available through this API.
+
 Query Parameters:
 - `offset` (optional): Number of events to skip (default: 0, min: 0)
 - `limit` (optional): Number of events to return (default: 10, min: 1, max: 100)

docs/sandbox/lifecycle-events-webhooks.mdx

@@ -352,6 +352,12 @@ When webhooks is send, we are adding headers to help you verify the authenticity
 - `e2b-signature-version` - Currently always `v1`, reserved for future use
 - `e2b-signature` - Signature for verifying the request authenticity`
 
+## Delivery and retries
+
+If a delivery fails, E2B retries it **up to 3 times, 10 seconds apart**. A delivery is treated as failed when your endpoint returns a 4xx or 5xx status code, the request times out, or it fails with a network error.
+
+Because a delivery can be retried, the same event may be delivered more than once. Make your webhook handler idempotent and use the `e2b-delivery-id` header to deduplicate deliveries you've already processed.
+
 ## Available event types
 
 The following event types can be subscribed to via webhooks, they are used as the `type` field in the [payload](#webhook-payload).

docs/sandbox/persistence.mdx

@@ -229,7 +229,7 @@ sbx = Sandbox.connect(sandbox_id, timeout=60) # 60 seconds
 
 ### Auto-pause
 
-Auto-pause is configured in the sandbox lifecycle on create. Set `onTimeout`/`on_timeout` to `pause`.
+Auto-pause is configured in the sandbox lifecycle on create. `onTimeout`/`on_timeout` defaults to `"kill"`, meaning the sandbox is terminated when its timeout expires. Set it to `"pause"` to auto-pause on timeout instead.
 
 <CodeGroup>
 ```js JavaScript & TypeScript
@@ -238,7 +238,7 @@ import { Sandbox } from 'e2b'
 const sandbox = await Sandbox.create({
   timeoutMs: 10 * 60 * 1000, // Optional: change default timeout (10 minutes)
   lifecycle: {
-    onTimeout: 'pause',
+    onTimeout: 'pause', // Defaults to 'kill'; set to 'pause' to auto-pause on timeout
     autoResume: false, // Optional (default is false)
   },
 })
@@ -249,8 +249,8 @@ from e2b import Sandbox
 sandbox = Sandbox.create(
     timeout=10 * 60,  # Optional: change default timeout (10 minutes)
     lifecycle={
-        "on_timeout": "pause", # Auto-pause after the sandbox times out
-        "auto_resume": False,  # Optional (default is False)
+        "on_timeout": "pause",  # Defaults to "kill"; set to "pause" to auto-pause on timeout
+        "auto_resume": False,   # Optional (default is False)
     },
 )
 ```
@@ -276,8 +276,10 @@ If you resume the sandbox, the service will be accessible again but you need to
 - Resuming a sandbox takes approximately **1 second**
 
 ### Paused sandbox retention
-- Paused sandboxes are kept **indefinitely** — there is no automatic deletion or time-to-live limit
+- Paused sandboxes are kept **indefinitely**; there is no automatic deletion or time-to-live limit
+- There is currently **no configurable "auto-kill after N days" option**; a paused sandbox will not expire on its own
 - You can resume a paused sandbox at any time
+- To remove a paused sandbox, you must kill it explicitly with an API call (`sandbox.kill()` / `Sandbox.kill(sandboxId)`), as shown in [Removing paused sandboxes](#removing-paused-sandboxes)
 
 ### Continuous runtime limits
 - A sandbox can remain running (without being paused) for:

docs/template/base-image.mdx

@@ -91,6 +91,14 @@ template.from_base_image()  # e2bdev/base
 
 </CodeGroup>
 
+`base` is also the template used when you call `Sandbox.create()` without specifying one. It is Debian-based and comes with common tooling pre-installed: Python 3, Node.js, Yarn, `git`, `curl`, `build-essential`, and the GitHub CLI (`gh`). For the exact contents, see the public Dockerfile: [`templates/base/e2b.Dockerfile`](https://github.com/e2b-dev/E2B/blob/main/templates/base/e2b.Dockerfile).
+
+### Default resources
+
+A sandbox gets its CPU and memory from the template it's built on. A sandbox built from `base` starts with **2 vCPU and 512 MiB of RAM**.
+
+You can override CPU and memory when you [build a template](/docs/template/build) (`cpuCount`/`cpu_count`, `memoryMB`/`memory_mb`). Disk size is not a default you set per sandbox; it's determined by your team's tier limit and applied at build time (see [Build limits](/docs/template/quickstart#build-limits)).
+
 ### Build from existing template
 
 Extend an existing template from your team or organization:

docs/template/build.mdx

@@ -39,6 +39,10 @@ build_info = Template.build(
 
 </CodeGroup>
 
+<Note>
+**Disk size is not a per-sandbox setting.** Unlike `cpuCount`/`cpu_count` and `memoryMB`/`memory_mb`, there is no disk-size parameter, neither on the template build nor on `Sandbox.create`. A sandbox's disk size is determined by your team's tier limit and applied when the template is built (see [Build limits](/docs/template/quickstart#build-limits)). `diskSizeMB` only ever appears in API response payloads (for example on sandbox and template info), never as an input. To get a larger disk, raise your tier or contact [support@e2b.dev](mailto:support@e2b.dev).
+</Note>
+
 ## Build in background
 
 The `buildInBackground` method starts the build process and returns immediately without waiting for completion. This is useful when you want to trigger a build and check its status later.