docs: document the gRPC-Web interface (GA in 1.39)

docs/cloud/manage-clusters/connect.mdx

@@ -80,6 +80,8 @@ If you don't have an existing API key, you'll need to create one. Follow these s
 
 :::note REST Endpoint vs gRPC Endpoint
 When using an official Weaviate [client library](/weaviate/client-libraries), you need to authenticate using the `REST Endpoint` and your API key. The client will infer the gRPC endpoint automatically and use the more performant gRPC protocol when available.
+
+To reach the [gRPC-Web interface](/weaviate/api/grpc.md#grpc-web), use the `REST Endpoint` URL, not the `gRPC Endpoint` URL, because gRPC-Web is served on the REST port.
 :::
 
 ### Environment variables

docs/deploy/configuration/env-vars/runtime-config.md

@@ -11,7 +11,7 @@ import RuntimeConfig from '/_includes/feature-notes/runtime-config.mdx';
 
 Weaviate supports runtime configuration management, allowing some configurations to be changed without any further restarts.
 
-Each runtime configuration corresponds to an existing environment variable. When a runtime configuration is updated, it overrides the value set by the corresponding environment variable.
+Most runtime configurations correspond to an existing environment variable. When a runtime configuration is updated, it overrides the value set by the corresponding environment variable.
 
 ## How to set up runtime configuration
 
@@ -69,6 +69,7 @@ The following overrides are currently supported:
 | `export_default_path`                            | `EXPORT_DEFAULT_PATH`                        |
 | `export_enabled`                                 | `EXPORT_ENABLED`                             |
 | `export_parallelism`                             | `EXPORT_PARALLELISM`                         |
+| `grpc_web_enabled`                               | _(not applicable)_                           |
 | `inverted_sorter_disabled`                       | `INVERTED_SORTER_DISABLED`                   |
 | `maximum_allowed_collections_count`              | `MAXIMUM_ALLOWED_COLLECTIONS_COUNT`          |
 | `objects_ttl_batch_size`                          | `OBJECTS_TTL_BATCH_SIZE`                     |

docs/weaviate/api/grpc.md

@@ -55,6 +55,19 @@ Alternatively, you can use other tools, such as the `grpcurl` command-line tool,
 - `grpcurl` command-line tool ([GitHub repo](https://github.com/fullstorydev/grpcurl))
 - Postman ([How to send a gRPC request with Postman](https://learning.postman.com/docs/sending-requests/grpc/grpc-request-interface/))
 
+## gRPC-Web
+
+:::info Added in `v1.38.3`
+:::
+
+Browsers cannot speak plain gRPC. To reach the gRPC API from a browser, Weaviate also serves a gRPC-Web interface over ordinary HTTP. It is served under the `/v1/grpc-web/` path prefix on the same port as the REST API (default `8080`), not on the gRPC port, so there is no second port to expose.
+
+The gRPC-Web interface is enabled by default. **[Runtime configuration](/deploy/configuration/env-vars/runtime-config.md) override:** set `grpc_web_enabled` to `false`. Note the snake_case. This takes effect without a restart.
+
+This setting has no environment variable equivalent. When the interface is disabled, requests to `/v1/grpc-web/` fall through to the REST handler, so other REST endpoints keep working as usual.
+
+The Weaviate client libraries connect over plain gRPC, so they do not use the gRPC-Web interface yet.
+
 ## Questions and feedback
 
 import DocsFeedback from "/\_includes/docs-feedback.mdx";