fix: correct agent handling in chat client

Improves agent handling in the chat client by:
- Fixing agent config extension when agent is not provided
- Correcting URL generation for agent endpoints
- Fixing agent list mapping to use proper agent IDs
- Improving type annotations for provider options

These changes make the agent-related functionality more robust and
type-safe throughout the codebase.

Author: deathbeam

lua/CopilotChat/client.lua

@@ -394,8 +394,8 @@ function Client:ask(prompt, opts)
   end
 
   local agents = self:fetch_agents()
-  local agent_config = agent and agents[agent] or {}
-  if not agent_config then
+  local agent_config = agent and agents[agent]
+  if agent and not agent_config then
     error('Agent not found: ' .. agent)
   end
 
@@ -412,7 +412,7 @@ function Client:ask(prompt, opts)
     model = vim.tbl_extend('force', model_config, {
       id = opts.model:gsub(':' .. provider_name .. '$', ''),
     }),
-    agent = vim.tbl_extend('force', agent_config, {
+    agent = agent_config and vim.tbl_extend('force', agent_config, {
       id = opts.agent and opts.agent:gsub(':' .. provider_name .. '$', ''),
     }),
     temperature = temperature,
@@ -612,7 +612,7 @@ function Client:ask(prompt, opts)
     args.stream = stream_func
   end
 
-  local response, err = utils.curl_post(provider.get_url(opts), args)
+  local response, err = utils.curl_post(provider.get_url(options), args)
 
   if self.current_job ~= job_id then
     return

lua/CopilotChat/config/providers.lua

@@ -20,7 +20,7 @@ local utils = require('CopilotChat.utils')
 
 ---@class CopilotChat.Provider.options
 ---@field model CopilotChat.Provider.model
----@field agent CopilotChat.Provider.agent
+---@field agent CopilotChat.Provider.agent?
 ---@field temperature number?
 
 ---@class CopilotChat.Provider.input
@@ -46,7 +46,7 @@ local utils = require('CopilotChat.utils')
 ---@field embed nil|string|fun(inputs:table<string>, headers:table):table<CopilotChat.Provider.embed>
 ---@field prepare_input nil|fun(inputs:table<CopilotChat.Provider.input>, opts:CopilotChat.Provider.options):table
 ---@field prepare_output nil|fun(output:table, opts:CopilotChat.Provider.options):CopilotChat.Provider.output
----@field get_url nil|fun(opts:table):string
+---@field get_url nil|fun(opts:CopilotChat.Provider.options):string
 
 local EDITOR_VERSION = 'Neovim/'
   .. vim.version().major
@@ -270,7 +270,7 @@ M.copilot = {
 
   get_url = function(opts)
     if opts.agent then
-      return 'https://api.githubcopilot.com/agents/' .. opts.agent .. '?chat'
+      return 'https://api.githubcopilot.com/agents/' .. opts.agent.id .. '?chat'
     end
 
     return 'https://api.githubcopilot.com/chat/completions'

lua/CopilotChat/init.lua

@@ -277,7 +277,10 @@ end
 ---@param prompt string
 ---@param config CopilotChat.config.shared
 function M.resolve_agent(prompt, config)
-  local agents = vim.tbl_keys(client:list_agents())
+  local agents = vim.tbl_map(function(agent)
+    return agent.id
+  end, client:list_agents())
+
   local selected_agent = config.agent
   prompt = prompt:gsub('@' .. WORD, function(match)
     if vim.tbl_contains(agents, match) then