fix(core,ui): restore-from-messages for initializing current model

This should fix #349

Author: sudo-tee

lua/opencode/core.lua

@@ -528,10 +528,16 @@ M.ensure_current_mode = Promise.async(function()
   return true
 end)
 
----Initialize current model from messages or config.
+---@class InitializeCurrentModelOpts
+---@field restore_from_messages? boolean Restore model/mode from the most recent session message
+
+---Initialize current model from session messages or config.
+---@param opts? InitializeCurrentModelOpts
 ---@return string|nil The current model
-M.initialize_current_model = Promise.async(function()
-  if state.messages then
+M.initialize_current_model = Promise.async(function(opts)
+  opts = opts or {}
+
+  if opts.restore_from_messages and state.messages then
     for i = #state.messages, 1, -1 do
       local msg = state.messages[i]
       if msg and msg.info and msg.info.modelID and msg.info.providerID then

lua/opencode/ui/renderer.lua

@@ -96,7 +96,9 @@ end
 ---Render all messages and parts from session_data into the output buffer
 ---Called after a full session fetch or when revert state changes
 ---@param session_data OpencodeMessage[]
-function M._render_full_session_data(session_data)
+---@param opts? { restore_model_from_messages?: boolean }
+function M._render_full_session_data(session_data, opts)
+  opts = opts or {}
   M.reset()
 
   if not state.active_session or not state.messages then
@@ -144,7 +146,9 @@ function M._render_full_session_data(session_data)
   flush.flush()
   flush.end_bulk_mode()
 
-  require('opencode.core').initialize_current_model()
+  if opts.restore_model_from_messages then
+    require('opencode.core').initialize_current_model({ restore_from_messages = true })
+  end
 
   M.scroll_to_bottom(true)
 
@@ -160,7 +164,7 @@ function M.render_full_session()
     return Promise.new():resolve(nil)
   end
   return fetch_session():and_then(function(session_data)
-    M._render_full_session_data(session_data)
+    M._render_full_session_data(session_data, { restore_model_from_messages = true })
     local active_session = state.active_session
     if active_session and active_session.id then
       require('opencode.ui.question_window').restore_pending_question(active_session.id)

tests/unit/api_spec.lua

@@ -522,6 +522,35 @@ describe('opencode.api', function()
       config_file.get_opencode_config = original_get_opencode_config
       state.model.set_model(original_model)
     end)
+
+    it('does not overwrite a user-selected model from prior session messages', function()
+      local original_model = state.current_model
+      local original_mode = state.current_mode
+      local original_messages = state.messages
+
+      state.model.set_model('openai/gpt-4.1')
+      state.model.set_mode('plan')
+      state.renderer.set_messages({
+        {
+          info = {
+            id = 'm1',
+            providerID = 'anthropic',
+            modelID = 'claude-3-opus',
+            mode = 'build',
+          },
+        },
+      })
+
+      local model = api.current_model():wait()
+
+      assert.equal('openai/gpt-4.1', model)
+      assert.equal('openai/gpt-4.1', state.current_model)
+      assert.equal('plan', state.current_mode)
+
+      state.renderer.set_messages(original_messages)
+      state.model.set_mode(original_mode)
+      state.model.set_model(original_model)
+    end)
   end)
 
   describe('toggle_zoom', function()

tests/unit/core_spec.lua

@@ -779,4 +779,48 @@ describe('opencode.core', function()
       config_file.get_opencode_config:revert()
     end)
   end)
+
+  describe('initialize_current_model', function()
+    it('keeps the current user-selected model and mode by default', function()
+      state.model.set_model('openai/gpt-4.1')
+      state.model.set_mode('plan')
+      state.renderer.set_messages({
+        {
+          info = {
+            id = 'm1',
+            providerID = 'anthropic',
+            modelID = 'claude-3-opus',
+            mode = 'build',
+          },
+        },
+      })
+
+      local model = core.initialize_current_model():wait()
+
+      assert.equal('openai/gpt-4.1', model)
+      assert.equal('openai/gpt-4.1', state.current_model)
+      assert.equal('plan', state.current_mode)
+    end)
+
+    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')
+      state.renderer.set_messages({
+        {
+          info = {
+            id = 'm1',
+            providerID = 'anthropic',
+            modelID = 'claude-3-opus',
+            mode = 'build',
+          },
+        },
+      })
+
+      local model = core.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)
+    end)
+  end)
 end)