fix: refresh and persist RubyLLM model registry on initialization

RubyLLM uses a static bundled models.json as its model registry. New
models released by providers (e.g., gpt-5.1, gpt-5.2) are not available
until the gem is updated, causing ModelNotFoundError for self-hosted
users who configure newer models.

Refresh the model registry asynchronously via a background thread during
Llm::Config.initialize! to fetch the latest model list from configured
providers and models.dev, then persist with save_to_json. The bundled
registry is available immediately; the refresh updates it in the
background without blocking the first LLM request.

Use double-checked locking with a mutex to prevent concurrent threads
from spawning duplicate refresh operations.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

lib/llm/config.rb

@@ -2,8 +2,7 @@ require 'ruby_llm'
 
 module Llm::Config
   DEFAULT_MODEL = 'gpt-4.1-mini'.freeze
-  REGISTRY_TTL = 1.hour
-  REGISTRY_PATH = Rails.root.join('tmp/ruby_llm_models.json').to_s
+  INIT_MUTEX = Mutex.new
 
   class << self
     def initialized?
@@ -13,9 +12,13 @@ module Llm::Config
     def initialize!
       return if @initialized
 
-      configure_ruby_llm
-      refresh_model_registry
-      @initialized = true
+      INIT_MUTEX.synchronize do
+        return if @initialized
+
+        configure_ruby_llm
+        refresh_model_registry
+        @initialized = true
+      end
     end
 
     def reset!
@@ -34,18 +37,12 @@ module Llm::Config
     private
 
     def refresh_model_registry
-      if fresh_registry_file?
-        RubyLLM.models.load_from_json!(REGISTRY_PATH)
-      else
+      Thread.new do
         RubyLLM.models.refresh!
-        RubyLLM.models.save_to_json(REGISTRY_PATH)
+        RubyLLM.models.save_to_json
+      rescue StandardError => e
+        Rails.logger.warn "Failed to refresh RubyLLM model registry: #{e.message}"
       end
-    rescue StandardError => e
-      Rails.logger.warn "Failed to refresh RubyLLM model registry: #{e.message}"
-    end
-
-    def fresh_registry_file?
-      File.exist?(REGISTRY_PATH) && File.mtime(REGISTRY_PATH) > REGISTRY_TTL.ago
     end
 
     def configure_ruby_llm

spec/support/ruby_llm_stubs.rb

@@ -0,0 +1,7 @@
+RSpec.configure do |config|
+  config.before do
+    models_instance = RubyLLM.models
+    allow(models_instance).to receive(:refresh!)
+    allow(models_instance).to receive(:save_to_json)
+  end
+end