From 4219a91df5e85e1af5e4aa03956093200e015e0c Mon Sep 17 00:00:00 2001
From: Siddharth Balyan <52913345+alt-glitch@users.noreply.github.com>
Date: Mon, 8 Jun 2026 20:10:47 +0530
Subject: [PATCH] fix(nix): make config.yaml group-writable under
 addToSystemPackages (#41940)
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addToSystemPackages exports HERMES_HOME system-wide and puts the hermes CLI on
interactive users' PATH, so those users (in the hermes group) share the
gateway's state — that's the option's whole purpose. But the activation script
wrote config.yaml as 0640 (group read-only), so an interactive user saving a
setting via the CLI/TUI hit:

  error: [Errno 13] Permission denied: '/var/lib/hermes/.hermes/config.yaml'

Make the mode conditional: 0660 when addToSystemPackages is set (group hermes
can write), else the previous 0640. .env stays 0640 either way — it holds
secrets, not user-facing settings. The config merge already preserves
user-added keys across rebuilds, so this simply lets interactive hermes-group
users actually make those edits.

Verified by evaluating the module's activation script for both option values:
addToSystemPackages=true -> chmod 0660, false -> chmod 0640.
---
 nix/nixosModules.nix | 15 ++++++++++++---
 1 file changed, 12 insertions(+), 3 deletions(-)

diff --git a/nix/nixosModules.nix b/nix/nixosModules.nix
index 19abc81a3b7..4458926b0f0 100644
--- a/nix/nixosModules.nix
+++ b/nix/nixosModules.nix
@@ -49,6 +49,12 @@
 
     configMergeScript = pkgs.callPackage ./configMergeScript.nix { };
 
+    # config.yaml mode: group-writable (0660) when interactive users share this
+    # HERMES_HOME via addToSystemPackages, so they can save settings through the
+    # CLI/TUI without hitting EACCES; otherwise group-read-only (0640). Secrets
+    # (.env) stay 0640 regardless — see below.
+    configYamlMode = if cfg.addToSystemPackages then "0660" else "0640";
+
     # Generate .env from non-secret environment attrset
     envFileContent = lib.concatStringsSep "\n" (
       lib.mapAttrsToList (k: v: "${k}=${v}") cfg.environment
@@ -728,7 +734,8 @@
           chmod 0750 ${cfg.stateDir}/home
 
           # Create subdirs, set setgid + group-writable, migrate existing files.
-          # Nix-managed files (config.yaml, .env, .managed) stay 0640/0644.
+          # Nix-managed .env/.managed stay 0640/0644; config.yaml uses
+          # configYamlMode (0660 under addToSystemPackages, else 0640).
           find ${cfg.stateDir}/.hermes -maxdepth 1 \
             \( -name "*.db" -o -name "*.db-wal" -o -name "*.db-shm" -o -name "SOUL.md" \) \
             -exec chmod g+rw {} + 2>/dev/null || true
@@ -743,12 +750,14 @@
           # Merge Nix settings into existing config.yaml.
           # Preserves user-added keys (skills, streaming, etc.); Nix keys win.
           # If configFile is user-provided (not generated), overwrite instead of merge.
+          # Mode is configYamlMode (0660 under addToSystemPackages so interactive
+          # hermes-group users can save settings via the CLI/TUI, else 0640).
           ${if cfg.configFile != null then ''
-            install -o ${cfg.user} -g ${cfg.group} -m 0640 -D ${configFile} ${cfg.stateDir}/.hermes/config.yaml
+            install -o ${cfg.user} -g ${cfg.group} -m ${configYamlMode} -D ${configFile} ${cfg.stateDir}/.hermes/config.yaml
           '' else ''
             ${configMergeScript} ${generatedConfigFile} ${cfg.stateDir}/.hermes/config.yaml
             chown ${cfg.user}:${cfg.group} ${cfg.stateDir}/.hermes/config.yaml
-            chmod 0640 ${cfg.stateDir}/.hermes/config.yaml
+            chmod ${configYamlMode} ${cfg.stateDir}/.hermes/config.yaml
           ''}
 
           # Managed mode marker (so interactive shells also detect NixOS management)