fix(agent): follow server model switches via session.model.selected

lua/opencode/services/agent_model.lua

@@ -69,7 +69,7 @@
     return
   end
 
   local config_file = require('opencode.config_file')
   config_file.get_opencode_providers():await()
   local model_info = config_file.get_model_info(provider, model)
 
@@ -249,4 +249,40 @@
   return state.current_model
 end)
 
+---Apply a server-side model selection ({id or modelID, providerID, variant?})
+---to local state; same-value calls are no-ops.
+---@param model? table
+function M.apply_server_selection(model)
+  local model_id = model and (model.id or model.modelID)
+  if not (model and model_id and model.providerID) then
+    return
+  end
+  local model_str = model.providerID .. '/' .. model_id
+  if state.current_model ~= model_str then
+    state.model.set_model(model_str)
+  end
+  if model.variant ~= nil and state.current_variant ~= model.variant then
+    state.model.set_variant(model.variant)
+  end
+end
+
+---Pull the authoritative session model from the server so state converges on
+---panel open; live changes arrive via session.model.selected events.
+---@return Promise|nil nil when there is no ready connection or active session
+function M.sync_from_server()
+  local connection = state.opencode_server
+  local session = state.active_session
+  if not (connection and session and session.id and connection:is_ready()) then
+    return nil
+  end
+  return connection.operations
+    .get_session(connection, session.id, session.location, util.apply_path_map, util.apply_reverse_path_map)
+    :and_then(function(fact)
+      M.apply_server_selection(fact and fact.model)
+    end)
+    :catch(function(err)
+      log.debug('Failed to sync session model from server', { error = err })
+    end)
+end
+
 return M

lua/opencode/services/session_runtime.lua

@@ -46,9 +46,9 @@
   local tab_id = state.active_session_tab
   local function is_current()
     return active_binding == binding
       and state.opencode_server == connection
       and connection:is_ready()
       and state.active_session_tab == tab_id
       and state.active_session ~= nil
       and state.active_session.id == session_id
   end
@@ -122,6 +122,25 @@
   })
 end
 
+local function setup_model_sync_events(enable)
+  vim.api.nvim_create_augroup('opencode_model_sync', { clear = true })
+  if not enable then
+    return
+  end
+  vim.api.nvim_create_autocmd('User', {
+    group = 'opencode_model_sync',
+    pattern = 'OpencodeEvent:session.model.selected',
+    callback = function(args)
+      local props = args.data and args.data.event and args.data.event.properties
+      local session = state.active_session
+      if not (props and props.sessionID and session and props.sessionID == session.id) then
+        return
+      end
+      agent_model.apply_server_selection(props.model)
+    end,
+  })
+end
+
 ---Keep active-session metadata and model selection current independently of rendering.
 ---Disabling releases the observation; enabling also adopts already-loaded facts.
 ---@param subscribe? boolean Defaults to true
@@ -139,6 +158,7 @@
   else
     observe_active_session()
   end
+  setup_model_sync_events(subscribe ~= false)
 end
 
 local function current_location()
@@ -398,6 +418,11 @@
     vim.notify('Error opening panel: ' .. tostring(err), vim.log.levels.ERROR)
     return Promise.new():reject(err)
   end
+
+  -- Re-sync model/variant from the server: the user may have switched them
+  -- in the TUI while this client was unfocused (no SSE broadcast on switch).
+  agent_model.sync_from_server()
+
   return Promise.new():resolve('ok')
 end)
 

tests/unit/persist_state_spec.lua

@@ -141,6 +141,9 @@ describe('persist_state', function()
         create_session = function()
           return Promise.new():resolve({ id = 'persist-test-session', title = 'Persist test', time = { updated = 1 } })
         end,
+        get_session = function(_, id)
+          return Promise.new():resolve({ id = id, title = id, time = { updated = 1 } })
+        end,
         list_primary_agents = function()
           return Promise.new():resolve({ 'build' })
         end,

tests/unit/services_agent_model_spec.lua

@@ -275,4 +275,43 @@ describe('opencode.services.agent_model', function()
     config_file.get_opencode_agents:revert()
     config_file.get_opencode_config:revert()
   end)
+
+  describe('apply_server_selection', function()
+    it('applies a server model ref to state', function()
+      state.store.set('current_model', 'openai/gpt-4.1')
+      agent_model.apply_server_selection({ id = 'gemini-4-argon', providerID = 'opencode' })
+      assert.equal('opencode/gemini-4-argon', state.current_model)
+    end)
+
+    it('accepts the V1 modelID shape', function()
+      state.store.set('current_model', nil)
+      agent_model.apply_server_selection({ modelID = 'claude-3-opus', providerID = 'anthropic' })
+      assert.equal('anthropic/claude-3-opus', state.current_model)
+    end)
+
+    it('updates the variant only when the server provides one', function()
+      state.store.set('current_model', 'anthropic/claude-3-opus')
+      state.model.set_variant('high')
+      agent_model.apply_server_selection({ id = 'claude-3-opus', providerID = 'anthropic' })
+      assert.equal('high', state.current_variant)
+      agent_model.apply_server_selection({ id = 'claude-3-opus', providerID = 'anthropic', variant = 'low' })
+      assert.equal('low', state.current_variant)
+    end)
+
+    it('keeps the local selection when the model ref matches', function()
+      state.store.set('current_model', 'anthropic/claude-3-opus')
+      state.store.set('current_variant', 'high')
+      agent_model.apply_server_selection({ id = 'claude-3-opus', providerID = 'anthropic', variant = 'high' })
+      assert.equal('anthropic/claude-3-opus', state.current_model)
+      assert.equal('high', state.current_variant)
+    end)
+
+    it('ignores incomplete model refs', function()
+      state.store.set('current_model', 'anthropic/claude-3-opus')
+      agent_model.apply_server_selection(nil)
+      agent_model.apply_server_selection({ id = 'claude-3-opus' })
+      agent_model.apply_server_selection({ providerID = 'anthropic' })
+      assert.equal('anthropic/claude-3-opus', state.current_model)
+    end)
+  end)
 end)

tests/unit/session_tabs_spec.lua

@@ -201,6 +201,7 @@ describe('opencode session panel tabs', function()
       stub(session_runtime, 'create_new_session').returns(Promise.new():resolve({ id = 'session-two', title = 'Two' }))
     local ensure_server_stub = stub(server_job, 'ensure_server').returns(Promise.new():resolve(server))
     local ensure_mode_stub = stub(agent_model, 'ensure_current_mode').returns(Promise.new():resolve(true))
+    local sync_model_stub = stub(agent_model, 'sync_from_server').returns(Promise.new():resolve(true))
     local render_stub = stub(renderer, 'render_full_session').returns(Promise.new():resolve(nil))
 
     state.session.set_active({ id = 'session-one', title = 'One' })
@@ -260,6 +261,7 @@ describe('opencode session panel tabs', function()
     create_session_stub:revert()
     ensure_server_stub:revert()
     ensure_mode_stub:revert()
+    sync_model_stub:revert()
     render_stub:revert()
   end)
 end)