adds blob retrieval

Author: m4sterbunny

docs/concepts/peer-das.md

@@ -56,8 +56,7 @@ With PeerDAS, consensus layer clients will use network and storage space for sid
   Storage consumption is increased, taking about 500 GB with 14 blobs of data layer space compared to 100 GB in Pectra.
 
   :::warning important
-  If a node operator needs complete blob data through the REST API, they must run in supernode mode.
-  Other types of nodes store only partial blob data.
+  If a node operator needs complete blob data through the REST API (for example, the `getBlobs` endpoint), they must either run in supernode mode or enable [`--get-blobs-api-p2p-sidecars-download-enabled`](../reference/cli/index.md#get-blobs-api-p2p-sidecars-download-enabled), which allows Teku to retrieve required sidecars on demand from the P2P network. Other types of nodes store only partial blob data.
   :::
 
 All node space requirements are subject to change proportionally to the target number of blobs, which is currently scheduled to be 14 starting from January 7, 2026 (about 1 month after the Fusaka fork).

docs/reference/cli/index.md

@@ -1002,6 +1002,85 @@ You can use [Infura](https://infura.io/) as the source of initial states using
 
 :::
 
+### `get-blobs-api-p2p-sidecars-download-enabled`
+
+<Tabs>
+  <TabItem value="Syntax" label="Syntax" default>
+
+```bash
+--get-blobs-api-p2p-sidecars-download-enabled[=<BOOLEAN>]
+```
+
+  </TabItem>
+  <TabItem value="Example" label="Example" >
+
+```bash
+--get-blobs-api-p2p-sidecars-download-enabled=true
+```
+
+  </TabItem>
+  <TabItem value="Environment variable" label="Environment variable" >
+
+```bash
+TEKU_GET_BLOBS_API_P2P_SIDECARS_DOWNLOAD_ENABLED=true
+```
+
+  </TabItem>
+  <TabItem value="Configuration file" label="Configuration file" >
+
+```bash
+get-blobs-api-p2p-sidecars-download-enabled: true
+```
+
+  </TabItem>
+</Tabs>
+
+Enables on-demand P2P download of required sidecars. When enabled, the `getBlobs` endpoint attempts to 
+download missing sidecars from the P2P network so that blobs can be reconstructed and returned.
+
+This allows nodes that are not 
+[supernodes](https://github.com/ethereum/consensus-specs/blob/master/specs/fulu/p2p-interface.md#supernodes) 
+to access [blob data via the Beacon API](https://consensys.github.io/teku/#tag/Beacon/operation/getBlobs).
+Successful retrievals are stored so that subsequent requests for the same slot do not trigger P2P download via RPC again.
+The default is `false`.
+
+### `get-blobs-sidecars-download-timeout`
+
+<Tabs>
+  <TabItem value="Syntax" label="Syntax" default>
+
+```bash
+--get-blobs-sidecars-download-timeout=<INTEGER>
+```
+
+  </TabItem>
+  <TabItem value="Example" label="Example" >
+
+```bash
+--get-blobs-sidecars-download-timeout=30
+```
+
+  </TabItem>
+  <TabItem value="Environment variable" label="Environment variable" >
+
+```bash
+TEKU_GET_BLOBS_SIDECARS_DOWNLOAD_TIMEOUT=30
+```
+
+  </TabItem>
+  <TabItem value="Configuration file" label="Configuration file" >
+
+```bash
+get-blobs-sidecars-download-timeout: 30
+```
+
+  </TabItem>
+</Tabs>
+
+Timeout in seconds for on-demand P2P sidecar download when serving the Beacon API (getBlobs).
+Only applies when [`--get-blobs-api-p2p-sidecars-download-enabled`](#get-blobs-api-p2p-sidecars-download-enabled) 
+is `true`.
+
 ### `help`
 
 ```bash title="Syntax"
@@ -2608,9 +2687,9 @@ but no less than 8 subnets.
 This option is a mostly altruistic feature for a node with an excess of resources
 that could be dedicated to serving network stability. When enabled, the option turns the node
 into a [supernode](https://github.com/ethereum/consensus-specs/blob/master/specs/fulu/p2p-interface.md#supernodes).
-If the node is required to provide blob data via the Beacon API, it's required
-to be a supernode; otherwise, the node doesn't have all data for blob
-reconstruction.
+To provide blob data via the Beacon API's `getBlobs` method, the node must either be a supernode or 
+have [`--get-blobs-api-p2p-sidecars-download-enabled`](#get-blobs-api-p2p-sidecars-download-enabled) set to 
+`true`, which allows Teku to retrieve required sidecars on demand from the P2P network.
 
 :::caution