fix(session): restore subagent mode from messages

Restore the mode recorded in session message history without validating it against the visible primary-agent list. Hidden subagents are intentionally omitted from that list, but existing session messages can still record them as the active mode; filtering restored modes left state.current_mode stuck on a stale primary agent, 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)