fix: display cost during streaming, guard winbar against nil/zero crashes, and async providers for percentage (#379)

* fix: display cost during streaming and guard against nil/zero overwrite

- Extract token/cost from step-finish parts before early return so
  cost appears before the chat fully completes (events.lua)
- Reject zero/nil cost in set_cost to preserve last known non-zero
  amount when a new chat starts or is cancelled (renderer.lua)
- Fix nil check in switch_mode: util.index_of returns nil not -1,
  causing arithmetic error when current_mode is not in agents list
  (agent.lua)

* fix(topbar): guard format_token_info against nil/zero cost crashes

* fix: load model info synchronously and use %= for winbar right-alignment

- Fall back to :wait(200) in get_model_info when :peek() returns nil
  so providers data is available on first render, enabling percentage
- Replace manual space-padding winbar alignment with neovim's %=
  statusline directive for reliable right-alignment regardless of
  description character width

* fix: trigger topbar re-render when providers load for context limit

Replace unreliable :wait() approach with a one-time finally callback
on the providers promise that calls topbar.render(). This guarantees
the percentage appears even when providers load asynchronously after
the initial render.

Author: CnsMaple

lua/opencode/commands/handlers/agent.lua

@@ -55,7 +55,7 @@ M.actions.switch_mode = Promise.async(function()
   local modes = config_file.get_opencode_agents():await() --[[@as string[] ]]
   local current_index = util.index_of(modes, state.store.get('current_mode'))
 
-  if current_index == -1 then
+  if current_index == nil then
     current_index = 0
   end
 

lua/opencode/config_file.lua

@@ -51,16 +51,27 @@ M.get_workspace_snapshot_path = Promise.async(function()
   return home .. '/.local/share/opencode/snapshot/' .. project.id
 end)
 
+local _providers_render_callback = false
+
 ---@return Promise<OpencodeProvidersResponse|nil>
 function M.get_opencode_providers()
   if not M.providers_promise then
     local state = require('opencode.state')
     M.providers_promise = state.api_client:list_providers()
   end
-  return M.providers_promise:catch(function(err)
+  local wrapped = M.providers_promise:catch(function(err)
     vim.notify('Error fetching Opencode providers: ' .. vim.inspect(err), vim.log.levels.ERROR)
     return nil
   end)
+  if not _providers_render_callback then
+    _providers_render_callback = true
+    wrapped:finally(function()
+      local ok, _ = pcall(function()
+        require('opencode.ui.topbar').render()
+      end)
+    end)
+  end
+  return wrapped
 end
 
 --- Get model information for a specific provider and model

lua/opencode/state/renderer.lua

@@ -29,6 +29,9 @@ function M.update_pending_permissions(mutator)
 end
 ---@param cost number
 function M.set_cost(cost)
+  if not cost or cost <= 0 then
+    return
+  end
   return store.set('cost', cost)
 end
 
@@ -42,7 +45,9 @@ end
 function M.set_stats(tokens_count, cost)
   return store.batch(function()
     store.set('tokens_count', tokens_count)
-    store.set('cost', cost)
+    if cost and cost > 0 then
+      store.set('cost', cost)
+    end
   end)
 end
 

lua/opencode/ui/renderer/events.lua

@@ -350,8 +350,15 @@ function M.on_part_updated(properties, revert_index)
     end
   end
 
-  -- step-start / step-finish are bookkeeping only — nothing to render
   if part.type == 'step-start' or part.type == 'step-finish' then
+    if part.type == 'step-finish' and part.tokens then
+      local tokens = part.tokens
+      if tokens.input > 0 and part.cost and type(part.cost) == 'number' then
+        state.renderer.set_stats(tokens.input + tokens.output + tokens.cache.read + tokens.cache.write, part.cost)
+      elseif tokens.input > 0 then
+        state.renderer.set_tokens_count(tokens.input + tokens.output + tokens.cache.read + tokens.cache.write)
+      end
+    end
     return
   end
 

lua/opencode/ui/topbar.lua

@@ -22,13 +22,22 @@ local function format_token_info()
         model_info = nil
       end
       local limit = state.tokens_count and model_info and model_info.limit and model_info.limit.context or 0
-      table.insert(parts, util.format_number(state.tokens_count) or nil)
+      local formatted_count = util.format_number(state.tokens_count)
+      if formatted_count then
+        table.insert(parts, formatted_count)
+      end
       if limit > 0 then
-        table.insert(parts, util.format_percentage(state.tokens_count / limit) or nil)
+        local formatted_pct = util.format_percentage(state.tokens_count / limit)
+        if formatted_pct then
+          table.insert(parts, formatted_pct)
+        end
       end
     end
-    if config.ui.display_cost and state.cost then
-      table.insert(parts, util.format_cost(state.cost) or nil)
+    if config.ui.display_cost and state.cost and state.cost > 0 then
+      local formatted_cost = util.format_cost(state.cost)
+      if formatted_cost then
+        table.insert(parts, formatted_cost)
+      end
     end
   end
 
@@ -37,21 +46,8 @@ local function format_token_info()
   return result
 end
 
-local function create_winbar_text(description, token_info, win_width)
-  local left_content = ''
-  local right_content = token_info
-
-  local desc_width = win_width - util.strdisplaywidth(left_content) - util.strdisplaywidth(right_content)
-
-  local desc_formatted
-  if #description >= desc_width then
-    local ellipsis = '... '
-    desc_formatted = description:sub(1, desc_width - #ellipsis) .. ellipsis
-  else
-    desc_formatted = description .. string.rep(' ', math.floor(desc_width - #description))
-  end
-
-  return left_content .. desc_formatted .. right_content
+local function create_winbar_text(description, token_info, _)
+  return description .. '%=' .. token_info
 end
 
 local function get_session_desc()