fix(agent): prevent hidden agents from switching the active mode (#382)

* fix(agent): prevent hidden agents from becoming the active mode

When a slash command uses a custom hidden agent, the plugin was
switching the global current_mode to that hidden agent. Since hidden
agents are filtered from the mode picker and M-m cycle, the user
would get stuck with no way to switch back.

The OpenCode TUI handles this by only switching mode when the agent
is visible (not hidden). Match that behavior in both code paths that
set the mode:

- messaging.send_message: check agent against visible agents list
  before calling set_mode
- agent_model.initialize_current_model: skip restoring mode from
  messages when the message's agent is hidden

* fix(agent): switch mode for visible agents when running user commands

run_user_command sends commands via api_client:send_command which
bypasses messaging.send_message, so the mode was never updated
when a command specified a visible agent. Call switch_to_mode
before sending the command so visible agents switch the mode
(matching TUI behavior), while hidden agents are silently skipped
by switch_to_mode's existing validation.

Author: hermandavid

lua/opencode/commands/handlers/workflow.lua

@@ -11,6 +11,7 @@ local input_window = require('opencode.ui.input_window')
 local ui = require('opencode.ui.ui')
 local nvim = vim['api']
 local session_runtime = require('opencode.services.session_runtime')
+local agent_model = require('opencode.services.agent_model')
 
 local M = {
   actions = {},
@@ -243,6 +244,13 @@ M.actions.run_user_command = Promise.async(function(name, args)
     local model = command_cfg.model or state.current_model
     local agent = command_cfg.agent or state.current_mode
 
+    if command_cfg.agent then
+      local available_agents = config_file.get_opencode_agents():await()
+      if vim.tbl_contains(available_agents, agent) then
+        agent_model.switch_to_mode(agent)
+      end
+    end
+
     local active_session = get_active_session_or_warn('No active session')
     if not active_session then
       return

lua/opencode/services/agent_model.lua

@@ -174,7 +174,10 @@ 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
-          state.model.set_mode(msg.info.mode)
+          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
         end
         return state.current_model
       end

lua/opencode/services/messaging.lua

@@ -2,6 +2,7 @@ local state = require('opencode.state')
 local context = require('opencode.context')
 local util = require('opencode.util')
 local config = require('opencode.config')
+local config_file = require('opencode.config_file')
 local Promise = require('opencode.promise')
 local log = require('opencode.log')
 local agent_model = require('opencode.services.agent_model')
@@ -48,7 +49,10 @@ M.send_message = Promise.async(function(prompt, opts)
 
   if opts.agent then
     params.agent = opts.agent
-    state.model.set_mode(opts.agent)
+    local available_agents = config_file.get_opencode_agents():await()
+    if vim.tbl_contains(available_agents, opts.agent) then
+      state.model.set_mode(opts.agent)
+    end
   end
 
   params.parts = context.format_message(prompt, opts.context):await()

tests/unit/api_spec.lua

@@ -463,6 +463,8 @@ describe('opencode.api', function()
         stub(api, 'open_input').invokes(function()
           return resolved('done')
         end)
+        local config_file = require('opencode.config_file')
+        stub(config_file, 'get_opencode_agents').returns(resolved({ 'plan', 'build' }))
       end)
 
       it('invokes run with correct model and agent', function()

tests/unit/services_agent_model_spec.lua

@@ -144,6 +144,9 @@ describe('opencode.services.agent_model', function()
   it('restores the latest session model and mode when explicitly requested', 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 = {
@@ -160,5 +163,33 @@ 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()
+    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 = {
+          id = 'm1',
+          providerID = 'anthropic',
+          modelID = 'claude-3-opus',
+          mode = 'hidden-xyz',
+        },
+      },
+    })
+
+    local model = agent_model.initialize_current_model({ restore_from_messages = true }):wait()
+
+    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)
 end)

tests/unit/services_messaging_spec.lua

@@ -7,6 +7,7 @@ loaded.services_messaging_spec = true
 
 local messaging = require('opencode.services.messaging')
 local session_runtime = require('opencode.services.session_runtime')
+local config_file = require('opencode.config_file')
 local state = require('opencode.state')
 local Promise = require('opencode.promise')
 local stub = require('luassert.stub')
@@ -52,6 +53,8 @@ describe('opencode.services.messaging', function()
     state.ui.set_windows({ mock = 'windows' })
     state.session.set_active({ id = 'sess1' })
 
+    stub(config_file, 'get_opencode_agents').returns(Promise.new():resolve({ 'plan', 'build' }))
+
     local create_called = false
     state.api_client.create_message = function(_, sid, params)
       create_called = true
@@ -69,6 +72,59 @@ describe('opencode.services.messaging', function()
     assert.equal(state.current_model, 'test/model')
     assert.is_true(create_called)
     state.api_client.create_message = orig
+    config_file.get_opencode_agents:revert()
+  end)
+
+  it('does not switch mode when agent is hidden', function()
+    state.ui.set_windows({ mock = 'windows' })
+    state.session.set_active({ id = 'sess1' })
+    state.model.set_mode('build')
+
+    stub(config_file, 'get_opencode_agents').returns(Promise.new():resolve({ 'plan', 'build' }))
+
+    local captured_params = nil
+    local orig = state.api_client.create_message
+    state.api_client.create_message = function(_, sid, params)
+      captured_params = params
+      return Promise.new():resolve({ id = 'm1' })
+    end
+
+    messaging.send_message('hello world', { agent = 'hidden-xyz' })
+    vim.wait(50, function()
+      return captured_params ~= nil
+    end)
+
+    assert.equal('build', state.current_mode)
+    assert.equal('hidden-xyz', captured_params.agent)
+
+    state.api_client.create_message = orig
+    config_file.get_opencode_agents:revert()
+  end)
+
+  it('switches mode when agent is visible', function()
+    state.ui.set_windows({ mock = 'windows' })
+    state.session.set_active({ id = 'sess1' })
+    state.model.set_mode('build')
+
+    stub(config_file, 'get_opencode_agents').returns(Promise.new():resolve({ 'plan', 'build' }))
+
+    local captured_params = nil
+    local orig = state.api_client.create_message
+    state.api_client.create_message = function(_, sid, params)
+      captured_params = params
+      return Promise.new():resolve({ id = 'm1' })
+    end
+
+    messaging.send_message('hello world', { agent = 'plan' })
+    vim.wait(50, function()
+      return captured_params ~= nil
+    end)
+
+    assert.equal('plan', state.current_mode)
+    assert.equal('plan', captured_params.agent)
+
+    state.api_client.create_message = orig
+    config_file.get_opencode_agents:revert()
   end)
 
   it('increments and decrements user_message_count correctly', function()

tests/unit/services_session_runtime_spec.lua

@@ -650,6 +650,9 @@ describe('opencode.services.session_runtime', function()
     it('restores the latest session model and mode when explicitly requested', 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 = {
@@ -666,6 +669,8 @@ describe('opencode.services.session_runtime', 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)
   end)
 end)