fix(renderer): skip hidden-messages notice in message navigation

Problem: when max_messages truncates older messages, the synthetic
hidden-messages notice (appended to state.messages via
on_message_updated) is matched by get_prev_rendered_message, so [[
yanks the cursor to the buffer top.

Solution: skip entries where is_renderer_synthetic_message is true in
both get_prev_rendered_message and get_next_rendered_message.

Author: phanen

lua/opencode/ui/renderer.lua

@@ -619,10 +619,12 @@ function M.get_next_rendered_message(current_line)
   local next_message = nil
 
   for _, message in ipairs(state.messages or {}) do
-    local rendered = message.info and message.info.id and ctx.render_state:get_message(message.info.id) or nil
-    if rendered and rendered.line_start and rendered.line_start + 1 > current_line then
-      next_message = rendered
-      break
+    if not is_renderer_synthetic_message(message) then
+      local rendered = message.info and message.info.id and ctx.render_state:get_message(message.info.id) or nil
+      if rendered and rendered.line_start and rendered.line_start + 1 > current_line then
+        next_message = rendered
+        break
+      end
     end
   end
 
@@ -634,9 +636,11 @@ end
 function M.get_prev_rendered_message(current_line)
   for i = #(state.messages or {}), 1, -1 do
     local message = state.messages[i]
-    local rendered = message and message.info and message.info.id and ctx.render_state:get_message(message.info.id)
-    if rendered and rendered.line_start and rendered.line_start + 1 < current_line then
-      return rendered
+    if message and not is_renderer_synthetic_message(message) then
+      local rendered = message.info and message.info.id and ctx.render_state:get_message(message.info.id)
+      if rendered and rendered.line_start and rendered.line_start + 1 < current_line then
+        return rendered
+      end
     end
   end
 

tests/unit/navigation_spec.lua

@@ -656,3 +656,69 @@ describe('navigation jumplist preservation', function()
     assert.equals(0, mark[2])
   end)
 end)
+
+describe('navigation hidden-messages-notice handling', function()
+  local output_buf, output_win
+  local original_windows
+
+  before_each(function()
+    original_windows = state.store.get('windows')
+    state.ui.clear_hidden_window_state()
+
+    output_buf = vim.api.nvim_create_buf(false, true)
+    output_win = vim.api.nvim_open_win(output_buf, true, {
+      relative = 'editor',
+      width = 80,
+      height = 20,
+      row = 0,
+      col = 0,
+    })
+    state.ui.set_windows({ output_buf = output_buf, output_win = output_win })
+  end)
+
+  after_each(function()
+    state.ui.clear_hidden_window_state()
+    pcall(vim.api.nvim_win_close, output_win, true)
+    pcall(vim.api.nvim_buf_delete, output_buf, { force = true })
+
+    if original_windows ~= nil then
+      state.ui.set_windows(original_windows)
+    else
+      state.ui.clear_windows()
+    end
+  end)
+
+  it('does not jump [[ to the hidden-messages notice when max_messages truncates', function()
+    local ctx = require('opencode.ui.renderer.ctx')
+    -- Simulate a session where max_messages truncates older messages: the
+    -- hidden notice was emitted into state.messages via on_message_updated,
+    -- so it lives in state.messages with a real line_start. The bug was that
+    -- get_prev_rendered_message iterated state.messages in reverse and matched
+    -- the notice first, jumping the user back to the buffer top.
+    state.renderer.set_messages({
+      { info = { id = 'real_old', role = 'assistant', sessionID = 's1' } },
+      { info = { id = 'real_mid', role = 'user', sessionID = 's1' } },
+      { info = { id = '__opencode_hidden_messages_notice__', role = 'system', sessionID = 's1' } },
+    })
+    ctx.render_state:set_message(
+      { info = { id = '__opencode_hidden_messages_notice__', role = 'system', sessionID = 's1' } },
+      1,
+      2
+    )
+    ctx.render_state:set_message({ info = { id = 'real_old', role = 'assistant', sessionID = 's1' } }, 4, 8)
+    ctx.render_state:set_message({ info = { id = 'real_mid', role = 'user', sessionID = 's1' } }, 10, 18)
+
+    vim.api.nvim_buf_set_lines(output_buf, 0, -1, false, vim.fn['repeat']({ 'line' }, 25))
+    -- Cursor at the first line of `real_mid` (line 11). Without the fix,
+    -- get_prev_rendered_message(11) iterated state.messages in reverse and
+    -- landed on the hidden notice at line 1, returning it (since its
+    -- line_start=1 satisfies `1+1 < 11`), so the user was yanked to line 2.
+    -- With the fix, the synthetic notice is skipped and `real_old` is chosen.
+    vim.api.nvim_win_set_cursor(output_win, { 11, 0 })
+
+    navigation.goto_prev_message()
+
+    local cursor = vim.api.nvim_win_get_cursor(output_win)
+    assert.equals(5, cursor[1])
+  end)
+end)