diff --git a/hive-c0re/src/meta.rs b/hive-c0re/src/meta.rs
index 3ec17332..fb803936 100644
--- a/hive-c0re/src/meta.rs
+++ b/hive-c0re/src/meta.rs
@@ -505,7 +505,6 @@ const CANONICAL_INPUTS: &[&str] = &["nixpkgs", "nixpkgs-unstable"];
 const FORWARDED_VARS: &[&str] = &[
     "HIVE_FORGE_URL",
     "HIVE_FORGE_PUBLIC_URL",
-    "HIVE_MATRIX_URL",
     "HYPERHIVE_PEERS",
     "HYPERHIVE_HIVE_DOMAIN",
     "HYPERHIVE_HIVE_NAME",
diff --git a/nix/modules/hive-c0re.nix b/nix/modules/hive-c0re.nix
index ef3f9e98..3fc87ab3 100644
--- a/nix/modules/hive-c0re.nix
+++ b/nix/modules/hive-c0re.nix
@@ -764,27 +764,6 @@ in
           else
             "http://127.0.0.1:${toString config.services.hyperhive.forge.httpPort}";
       }
-      // lib.optionalAttrs config.services.hyperhive.matrix.enable {
-        # In-cluster matrix homeserver URL for each agent's
-        # hive-matrix-daemon. Same shape + rationale as HIVE_FORGE_URL:
-        # - Isolated (private netns): reach tuwunel via the gateway vhost
-        #   (`matrix.<domain>`) on plain http:80 — host loopback is dead.
-        # - Shared netns: direct host loopback on the tuwunel port.
-        # gatewayHost null-guard falls back to loopback so a domain-less
-        # config doesn't break eval (it just won't work under isolation,
-        # which needs a gateway anyway). Forwarded to agents by meta.rs
-        # alongside HIVE_FORGE_URL; shares the same env-forwarding ordering
-        # caveat (value baked at config-generation time).
-        HIVE_MATRIX_URL =
-          if
-            config.services.hyperhive.network.enable
-            && config.services.hyperhive.network.isolateContainers
-            && config.services.hyperhive.matrix.gatewayHost != null
-          then
-            "http://${config.services.hyperhive.matrix.gatewayHost}"
-          else
-            "http://127.0.0.1:${toString config.services.hyperhive.matrix.httpPort}";
-      }
       // lib.optionalAttrs config.services.hyperhive.matrix.gui.enable {
         # Availability flags read by the dashboard's `/api/state`.
         # Matrix GUI lives entirely on the gateway nginx (matrix tab
diff --git a/nix/templates/harness-base.nix b/nix/templates/harness-base.nix
index edd43c25..8d3b91ee 100644
--- a/nix/templates/harness-base.nix
+++ b/nix/templates/harness-base.nix
@@ -17,12 +17,6 @@ let
   # from `userName` to keep them coupled.
   userName = config.hyperhive.user.name;
   homeDir = "/home/${userName}";
-  # Single source of truth for the default matrix homeserver URL, shared
-  # by the `hyperhive.matrix.url` option default and the daemon-unit guard
-  # that decides whether to set a unit-level HIVE_MATRIX_URL (so the two
-  # cannot drift). Matches the daemon's own built-in default
-  # (`paths::DEFAULT_HOMESERVER`).
-  matrixUrlDefault = "http://localhost:8008";
 in
 {
   # Shared scaffolding for every hyperhive harness container.
@@ -294,7 +288,7 @@ in
 
   options.hyperhive.matrix.url = lib.mkOption {
     type = lib.types.str;
-    default = matrixUrlDefault;
+    default = "http://localhost:8008";
     example = "https://matrix.darkest.space";
     description = ''
       Matrix homeserver URL the agent's `hive-matrix-daemon` connects
@@ -1333,20 +1327,10 @@ in
       after = [ "network-online.target" ];
       wants = [ "network-online.target" ];
       environment = {
+        HIVE_MATRIX_URL = config.hyperhive.matrix.url;
         HIVE_MATRIX_SOCKET = "/run/hive-matrix/socket";
         RUST_LOG = "info";
       }
-      # Homeserver URL: by default the daemon inherits the host-forwarded
-      # HIVE_MATRIX_URL (set isolation-aware by hive-c0re: `matrix.<domain>`
-      # via the gateway under private-netns isolation, loopback otherwise),
-      # falling back to the daemon's built-in localhost default if the
-      # forward is absent. A per-agent `hyperhive.matrix.url` override
-      # (non-default) is set unit-level so it wins over the forwarded value;
-      # at the default we deliberately DON'T set it so the forwarded
-      # isolation-aware value isn't shadowed.
-      // lib.optionalAttrs (config.hyperhive.matrix.url != matrixUrlDefault) {
-        HIVE_MATRIX_URL = config.hyperhive.matrix.url;
-      }
       # Multi-account: serialize the *extra* accounts to the JSON the
       # daemon parses (`accounts::configured`). Only set when extras are
       # declared; the daemon always synthesizes the primary `main`