diff --git a/swarm-builder/README.md b/swarm-builder/README.md
index 6892a178..5de45514 100644
--- a/swarm-builder/README.md
+++ b/swarm-builder/README.md
@@ -12,9 +12,10 @@ the answer into a `swarm-builder` commit status on the PR's head.
 
 ## What a build is
 
-- `nix build` of `nix/builder/check-flake`'s `check` output, with its three
-  inputs overridden: `hyperhive` and `nixpkgs` to this host's own sources, and
-  `agent` to `git+https://<forge>/agent-configs/<agent>?ref=refs/pull/<pr>/head&rev=<rev>`.
+- `nix build` of `nix/builder/check-flake`'s `check` output, with its four
+  inputs overridden: `hyperhive` and `nixpkgs` to this host's own sources,
+  `hyperhive-docs` to the `docs/` source its hives use (`c0re.hyperhiveDocs`),
+  and `agent` to `git+https://<forge>/agent-configs/<agent>?ref=refs/pull/<pr>/head&rev=<rev>`.
 - The evaluation runs here, pure; the builds run in the host daemon's sandbox
   as an untrusted client, so a config can neither set daemon options nor read
   this service's environment.