fix(session): restore subagent mode from messages

Restore the mode recorded in session message history without validating it against the current agent list. Hidden or disabled subagents can remain valid for existing sessions; filtering them out left state.current_mode stuck on a stale main agent mode, affecting both UI display and subsequent message routing.

Author: jensenojs

lua/opencode/services/agent_model.lua

@@ -174,10 +174,7 @@ M.initialize_current_model = Promise.async(function(opts)
           state.model.set_model(model_str)
         end
         if msg.info.mode and state.current_mode ~= msg.info.mode then
-          local available_agents = config_file.get_opencode_agents():await()
-          if vim.tbl_contains(available_agents, msg.info.mode) then
-            state.model.set_mode(msg.info.mode)
-          end
+          state.model.set_mode(msg.info.mode)
         end
         return state.current_model
       end

tests/unit/services_agent_model_spec.lua

@@ -145,8 +145,6 @@ describe('opencode.services.agent_model', function()
     state.model.set_model('openai/gpt-4.1')
     state.model.set_mode('plan')
 
-    stub(config_file, 'get_opencode_agents').returns(Promise.new():resolve({ 'plan', 'build' }))
-
     state.renderer.set_messages({
       {
         info = {
@@ -163,16 +161,12 @@ describe('opencode.services.agent_model', function()
     assert.equal('anthropic/claude-3-opus', model)
     assert.equal('anthropic/claude-3-opus', state.current_model)
     assert.equal('build', state.current_mode)
-
-    config_file.get_opencode_agents:revert()
   end)
 
-  it('does not restore mode to a hidden agent from messages', function()
+  it('restores mode from messages even if the agent is hidden', function()
     state.model.set_model('openai/gpt-4.1')
     state.model.set_mode('build')
 
-    stub(config_file, 'get_opencode_agents').returns(Promise.new():resolve({ 'plan', 'build' }))
-
     state.renderer.set_messages({
       {
         info = {
@@ -188,8 +182,6 @@ describe('opencode.services.agent_model', function()
 
     assert.equal('anthropic/claude-3-opus', model)
     assert.equal('anthropic/claude-3-opus', state.current_model)
-    assert.equal('build', state.current_mode)
-
-    config_file.get_opencode_agents:revert()
+    assert.equal('hidden-xyz', state.current_mode)
   end)
 end)