fix: retry fetching opencode agents while server initializes

The OpenCode server may return an empty primary-agent list while it
is still starting up. Treat that transient state like an error and
retry up to 3 times with a 500ms delay before falling back to an
empty agent list.

Author: sudo-tee

lua/opencode/config_file.lua

@@ -141,7 +141,20 @@ end
 
 ---@type fun(): Promise<string[]>
 M.get_opencode_agents = Promise.async(function()
-  return resource('list_primary_agents'):await() or {}
+  local empty_agents = {}
+  return Promise.retry(function()
+    return resource('list_primary_agents'):and_then(function(agents)
+      if agents and #agents > 0 then
+        return agents
+      end
+      return Promise.new():reject(empty_agents)
+    end)
+  end, 3, 500):catch(function(err)
+    if err == empty_agents then
+      return {}
+    end
+    return Promise.new():reject(err)
+  end):await()
 end)
 
 ---@type fun(): Promise<string[]>

tests/unit/config_file_spec.lua

@@ -80,6 +80,27 @@ describe('config_file.setup', function()
     end):wait()
   end)
 
+  it('retries an empty primary-agent response while the server initializes', function()
+    local original_defer_fn = vim.defer_fn
+    local attempts = 0
+    vim.defer_fn = function(callback)
+      callback()
+    end
+
+    set_operations({
+      list_primary_agents = function()
+        attempts = attempts + 1
+        return Promise.new():resolve(attempts < 3 and {} or { 'build' })
+      end,
+    })
+
+    local agents = config_file.get_opencode_agents():wait()
+
+    vim.defer_fn = original_defer_fn
+    assert.same({ 'build' }, agents)
+    assert.equals(3, attempts)
+  end)
+
   it('gets subagents from the selected protocol', function()
     Promise.spawn(function()
       set_operations({