harness: surface hive + swarm display names to agents (#701)

hive-c0re/src/meta.rs

@@ -280,6 +280,33 @@ fn render_flake(
 /// meta-level reference (#355).
 const CANONICAL_INPUTS: &[&str] = &["nixpkgs", "nixpkgs-unstable"];
 
+/// Env vars hive-c0re forwards from its own systemd unit env into every
+/// sub-agent's harness service env. Each entry is `(env_var_name,
+/// host_value)`. Empty / unset vars are filtered out so absent options
+/// don't render no-op `FOO = ""` lines into the meta flake.
+///
+/// Returns owned `String` values so the result is `'static`-friendly +
+/// trivial to stub from tests (which build their own slice instead of
+/// touching process-wide env).
+const FORWARDED_VARS: &[&str] = &[
+    "HIVE_FORGE_URL",
+    "HYPERHIVE_HIVE_DOMAIN",
+    "HYPERHIVE_HIVE_NAME",
+    "HYPERHIVE_SWARM_NAME",
+];
+
+fn forwarded_env_vars() -> Vec<(&'static str, String)> {
+    FORWARDED_VARS
+        .iter()
+        .filter_map(|&name| {
+            std::env::var(name)
+                .ok()
+                .filter(|v| !v.is_empty())
+                .map(|v| (name, v))
+        })
+        .collect()
+}
+
 /// Read an agent's applied `flake.lock` and return the subset of
 /// `CANONICAL_INPUTS` it declares as direct (root-level) inputs.
 /// Returns an empty vec when the lock is missing or unparsable —
@@ -446,14 +473,21 @@ where
             "                HIVE_CONTEXT_WINDOW_TOKENS_{upper_key} = \"{val}\";"
         );
     }
-    // Forge URL — injected when hive-c0re itself has HIVE_FORGE_URL set
-    // (the NixOS module derives it from hyperhive.forge.{domain,httpPort}).
-    // Agents use it in forge_notify to poll Forgejo for PR/review events.
-    if let Ok(forge_url) = std::env::var("HIVE_FORGE_URL")
-        && !forge_url.is_empty()
-    {
-        let escaped = forge_url.replace('\\', "\\\\").replace('"', "\\\"");
-        let _ = writeln!(out, "                HIVE_FORGE_URL = \"{escaped}\";");
+    // Forwarded env vars — picked up from hive-c0re's own systemd unit
+    // env (`services.hyperhive.*` options flow through nix/modules/
+    // hive-c0re.nix into the host process). We copy whatever's set into
+    // each sub-agent's harness service env so the in-container surfaces
+    // (`identity.rs`, `forge_notify`) see a consistent view across the
+    // whole hive. Absent host-side env (option not set) → skip emission
+    // → in-container accessors fall back to None / defaults gracefully.
+    //
+    // - HIVE_FORGE_URL: agents poll this for Forgejo notifications.
+    // - HYPERHIVE_HIVE_DOMAIN: machine-readable hive DNS (#589).
+    // - HYPERHIVE_HIVE_NAME / HYPERHIVE_SWARM_NAME: human display
+    //   names for hive + swarm (#701).
+    for (var, val) in forwarded_env_vars() {
+        let escaped = val.replace('\\', "\\\\").replace('"', "\\\"");
+        let _ = writeln!(out, "                {var} = \"{escaped}\";");
     }
     out.push_str(
         r#"                HYPERHIVE_STATE_DIR = "/agents/${name}/state";