feat(session): add sibling and parent session navigation

README.md

@@ -190,6 +190,8 @@ require('opencode').setup({
       ['i'] = { 'focus_input', 'n' }, -- Focus on input window and enter insert mode at the end of the input from the output window
       ['<M-r>'] = { 'cycle_variant', mode = { 'n' } }, -- Cycle through available model variants
       ['<leader>oS'] = { 'select_child_session' }, -- Select and load a child session
+      ['<leader>oP'] = { 'select_parent_session' }, -- Go to parent session
+      ['<leader>oB'] = { 'select_sibling_session' }, -- Select sibling session (children of same parent)
       ['<leader>oD'] = { 'debug_message' }, -- Open raw message in new buffer for debugging
       ['<leader>oO'] = { 'debug_output' }, -- Open raw output in new buffer for debugging
       ['<leader>ods'] = { 'debug_session' }, -- Open raw session in new buffer for debugging
@@ -603,7 +605,9 @@ The plugin provides the following actions that can be triggered via keymaps, com
 | Toggle focus opencode / last window                         | `<leader>ot`                          | `:Opencode toggle focus`                    | `require('opencode.api').toggle_focus()`                               |
 | Close UI windows                                            | `<leader>oq`                          | `:Opencode close`                           | `require('opencode.api').close()`                                      |
 | Select and load session                                     | `<leader>os`                          | `:Opencode session select`                  | `require('opencode.api').select_session()`                             |
-| **Select and load child session**                           | `<leader>oS`                          | `:Opencode session select_child`            | `require('opencode.api').select_child_session()`                       |
+| **Select and load child session**                           | `<leader>oS`                          | `:Opencode session child`                   | `require('opencode.api').select_child_session()`                       |
+| **Select sibling session**                                  | `<leader>oB`                          | `:Opencode session sibling`                 | `require('opencode.api').select_sibling_session()`                     |
+| **Go to parent session**                                    | `<leader>oP`                          | `:Opencode session parent`                  | `require('opencode.api').select_parent_session()`                      |
 | Open timeline picker (navigate/undo/redo/fork to message)   | `<leader>oT`                          | `:Opencode timeline`                        | `require('opencode.api').timeline()`                                   |
 | Browse code references from conversation                    | `gr` (window)                         | `:Opencode references` / `/references`      | `require('opencode.api').references()`                                 |
 | Configure provider and model                                | `<leader>op`                          | `:Opencode configure provider`              | `require('opencode.api').configure_provider()`                         |

lua/opencode/api.lua

@@ -42,6 +42,8 @@ local action_groups = {
   session = {
     open_input_new_session = session.open_input_new_session,
     select_child_session = session.select_child_session,
+    select_sibling_session = session.select_sibling_session,
+    select_parent_session = session.select_parent_session,
     share = session.share,
     unshare = session.unshare,
     initialize = session.initialize,

lua/opencode/commands/handlers/session.lua

@@ -10,7 +10,7 @@ local M = {
   actions = {},
 }
 
-local session_subcommands = { 'new', 'select', 'child', 'compact', 'share', 'unshare', 'agents_init', 'rename' }
+local session_subcommands = { 'new', 'select', 'child', 'sibling', 'parent', 'compact', 'share', 'unshare', 'agents_init', 'rename' }
 
 ---@param message string
 local function invalid_arguments(message)
@@ -105,6 +105,25 @@ function M.actions.select_child_session()
   session_runtime.select_session(active and active.id or nil)
 end
 
+function M.actions.select_sibling_session()
+  local active = state.active_session
+  if not active or not active.parentID then
+    vim.notify('Current session has no parent – showing root sessions', vim.log.levels.INFO)
+    session_runtime.select_session(nil)
+    return
+  end
+  session_runtime.select_session(active.parentID)
+end
+
+function M.actions.select_parent_session()
+  local active = state.active_session
+  if not active or not active.parentID then
+    vim.notify('Current session has no parent', vim.log.levels.INFO)
+    return
+  end
+  session_runtime.switch_session(active.parentID)
+end
+
 ---@param current_session? Session
 function M.actions.compact_session(current_session)
   local state_obj = state
@@ -411,6 +430,12 @@ local session_subcommand_actions = {
   child = function()
     return M.actions.select_child_session()
   end,
+  sibling = function()
+    return M.actions.select_sibling_session()
+  end,
+  parent = function()
+    return M.actions.select_parent_session()
+  end,
   compact = function()
     return M.actions.compact_session()
   end,
@@ -443,6 +468,8 @@ M.command_defs = {
   open_input_new_session = { desc = 'Open input (new session)', execute = M.actions.open_input_new_session },
   select_session         = { desc = 'Select session',           execute = function() return M.actions.select_session() end },
   select_child_session   = { desc = 'Select child session',     execute = M.actions.select_child_session },
+  select_sibling_session = { desc = 'Select sibling session',   execute = M.actions.select_sibling_session },
+  select_parent_session  = { desc = 'Go to parent session',     execute = M.actions.select_parent_session },
   rename_session         = { desc = 'Rename session',           execute = function(args) return M.actions.rename_session(nil, args[1]) end },
   undo = {
     desc = 'Undo last action',

lua/opencode/config.lua

@@ -36,6 +36,9 @@ M.defaults = {
       ['<leader>oT'] =  { 'timeline',                                          desc = 'Session timeline' },
       ['<leader>oq'] =  { 'close',                                             desc = 'Close Opencode window' },
       ['<leader>os'] =  { 'select_session',                                    desc = 'Select session' },
+      ['<leader>oS'] =  { 'select_child_session',                              desc = 'Select child session' },
+      ['<leader>oP'] =  { 'select_parent_session',                             desc = 'Go to parent session' },
+      ['<leader>oB'] =  { 'select_sibling_session',                            desc = 'Select sibling session' },
       ['<leader>oR'] =  { 'rename_session',                                    desc = 'Rename session' },
       ['<leader>op'] =  { 'configure_provider',                                desc = 'Configure provider' },
       ['<leader>oV'] =  { 'configure_variant',                                 desc = 'Configure model variant' },
@@ -71,6 +74,8 @@ M.defaults = {
       ['<M-i>'] =       { 'toggle_input',                 mode = { 'n' },      desc = 'Toggle input window' },
       ['<M-r>'] =       { 'cycle_variant',                mode = { 'n' },      desc = 'Cycle model variants' },
       ['<leader>oS'] =  { 'select_child_session',                              desc = 'Select child session' },
+      ['<leader>oP'] =  { 'select_parent_session',                             desc = 'Go to parent session' },
+      ['<leader>oB'] =  { 'select_sibling_session',                            desc = 'Select sibling session' },
       ['<leader>oD'] =  { 'debug_message',                                     desc = 'Open raw message debug view' },
       ['<leader>oO'] =  { 'debug_output',                                      desc = 'Open raw output debug view' },
       ['<leader>ods'] = { 'debug_session',                                     desc = 'Open raw session debug view' },
@@ -93,6 +98,8 @@ M.defaults = {
       ['<M-i>']  =      { 'toggle_input',                 mode = { 'n', 'i' }, desc = 'Toggle input window'                                      },
       ['gr']     =      { 'references',                                        desc = 'Browse code references'                                   },
       ['<leader>oS'] =  { 'select_child_session',                              desc = 'Select child session'                                     },
+      ['<leader>oP'] =  { 'select_parent_session',                             desc = 'Go to parent session'                                     },
+      ['<leader>oB'] =  { 'select_sibling_session',                            desc = 'Select sibling session'                                   },
       ['<leader>oD'] =  { 'debug_message',                                     desc = 'Open raw message debug view'                              },
       ['<leader>oO'] =  { 'debug_output',                                      desc = 'Open raw output debug view'                               },
       ['<leader>ods'] = { 'debug_session',                                     desc = 'Open raw session debug view'                              },

tests/unit/commands_handlers_spec.lua

@@ -94,7 +94,7 @@ describe('opencode.commands.handlers', function()
     assert.same({ 'accept', 'accept_all', 'deny' }, defs.permission.completions)
     assert.same({ allow_empty = false }, defs.permission.nested_subcommand)
 
-    assert.same({ 'new', 'select', 'child', 'compact', 'share', 'unshare', 'agents_init', 'rename' }, defs.session.completions)
+    assert.same({ 'new', 'select', 'child', 'sibling', 'parent', 'compact', 'share', 'unshare', 'agents_init', 'rename' }, defs.session.completions)
     assert.same({ allow_empty = false }, defs.session.nested_subcommand)
 
     assert.same({ 'input', 'output' }, defs.open.completions)
@@ -203,4 +203,150 @@ describe('opencode.commands.handlers', function()
     assert.equal('all', called.scope)
     assert.is_nil(called.snapshot_id)
   end)
+
+  it('select_sibling_session calls select_session with parentID when active session is a child', function()
+    local session_handler = require('opencode.commands.handlers.session')
+    local session_runtime = require('opencode.services.session_runtime')
+    local state = require('opencode.state')
+
+    state.session.set_active({ id = 'child1', parentID = 'root1', title = 'Child 1' })
+    local called_parent_id
+    local original = session_runtime.select_session
+    session_runtime.select_session = function(parent_id)
+      called_parent_id = parent_id
+    end
+
+    session_handler.actions.select_sibling_session()
+
+    session_runtime.select_session = original
+    assert.equal('root1', called_parent_id)
+  end)
+
+  it('select_sibling_session falls back to root sessions when active session has no parent', function()
+    local session_handler = require('opencode.commands.handlers.session')
+    local session_runtime = require('opencode.services.session_runtime')
+    local state = require('opencode.state')
+
+    state.session.set_active({ id = 'root1', parentID = nil, title = 'Root' })
+    local called_parent_id = 'sentinel'
+    local original = session_runtime.select_session
+    session_runtime.select_session = function(parent_id)
+      called_parent_id = parent_id
+    end
+
+    local notify_stub = stub(vim, 'notify')
+    session_handler.actions.select_sibling_session()
+    notify_stub:revert()
+
+    session_runtime.select_session = original
+    assert.is_nil(called_parent_id)
+  end)
+
+  it('select_parent_session switches to parent when active session is a child', function()
+    local session_handler = require('opencode.commands.handlers.session')
+    local session_runtime = require('opencode.services.session_runtime')
+    local state = require('opencode.state')
+
+    state.session.set_active({ id = 'child1', parentID = 'root1', title = 'Child 1' })
+    local switched_to
+    local original = session_runtime.switch_session
+    session_runtime.switch_session = function(session_id)
+      switched_to = session_id
+    end
+
+    session_handler.actions.select_parent_session()
+
+    session_runtime.switch_session = original
+    assert.equal('root1', switched_to)
+  end)
+
+  it('select_parent_session notifies when active session has no parent', function()
+    local session_handler = require('opencode.commands.handlers.session')
+    local session_runtime = require('opencode.services.session_runtime')
+    local state = require('opencode.state')
+
+    state.session.set_active({ id = 'root1', parentID = nil, title = 'Root' })
+    local switched_to = nil
+    local original = session_runtime.switch_session
+    session_runtime.switch_session = function(session_id)
+      switched_to = session_id
+    end
+
+    local notify_stub = stub(vim, 'notify')
+    session_handler.actions.select_parent_session()
+
+    session_runtime.switch_session = original
+    assert.is_nil(switched_to)
+    assert.stub(notify_stub).was_called()
+    notify_stub:revert()
+  end)
+
+  it('select_sibling_session does nothing when no active session', function()
+    local session_handler = require('opencode.commands.handlers.session')
+    local session_runtime = require('opencode.services.session_runtime')
+    local state = require('opencode.state')
+
+    state.session.set_active(nil)
+    local called = false
+    local original = session_runtime.select_session
+    session_runtime.select_session = function()
+      called = true
+    end
+
+    local notify_stub = stub(vim, 'notify')
+    session_handler.actions.select_sibling_session()
+    notify_stub:revert()
+
+    session_runtime.select_session = original
+    assert.is_true(called)
+  end)
+
+  it('select_parent_session does nothing when no active session', function()
+    local session_handler = require('opencode.commands.handlers.session')
+    local session_runtime = require('opencode.services.session_runtime')
+    local state = require('opencode.state')
+
+    state.session.set_active(nil)
+    local switched_to = nil
+    local original = session_runtime.switch_session
+    session_runtime.switch_session = function(session_id)
+      switched_to = session_id
+    end
+
+    local notify_stub = stub(vim, 'notify')
+    session_handler.actions.select_parent_session()
+
+    session_runtime.switch_session = original
+    assert.is_nil(switched_to)
+    assert.stub(notify_stub).was_called()
+    notify_stub:revert()
+  end)
+
+  it('session subcommand sibling routes to select_sibling_session', function()
+    local session_handler = require('opencode.commands.handlers.session')
+    local called = false
+    local original = session_handler.actions.select_sibling_session
+    session_handler.actions.select_sibling_session = function()
+      called = true
+    end
+
+    session_handler.command_defs.session.execute({ 'sibling' })
+
+    session_handler.actions.select_sibling_session = original
+    assert.is_true(called)
+  end)
+
+  it('session subcommand parent routes to select_parent_session', function()
+    local session_handler = require('opencode.commands.handlers.session')
+    local called = false
+    local original = session_handler.actions.select_parent_session
+    session_handler.actions.select_parent_session = function()
+      called = true
+    end
+
+    session_handler.command_defs.session.execute({ 'parent' })
+
+    session_handler.actions.select_parent_session = original
+    assert.is_true(called)
+  end)
 end)

tests/unit/services_session_runtime_spec.lua

@@ -308,6 +308,29 @@ describe('opencode.services.session_runtime', function()
       assert.truthy(state.active_session)
       assert.equal('session3', state.active_session.id)
     end)
+
+    it('filters child sessions by parentID', function()
+      local mock_sessions = {
+        { id = 'root1', title = 'Root', modified = 1, parentID = nil },
+        { id = 'child1', title = 'Child 1', modified = 2, parentID = 'root1' },
+        { id = 'child2', title = 'Child 2', modified = 3, parentID = 'root1' },
+        { id = 'child3', title = 'Child of other', modified = 4, parentID = 'root2' },
+      }
+      stub(session, 'get_all_workspace_sessions').invokes(function()
+        return Promise.new():resolve(mock_sessions)
+      end)
+      local passed
+      stub(ui, 'select_session').invokes(function(sessions, cb)
+        passed = sessions
+        cb(nil)
+      end)
+
+      state.ui.set_windows({ input_buf = 1, output_buf = 2 })
+      session_runtime.select_session('root1'):wait()
+      assert.equal(2, #passed)
+      assert.equal('child1', passed[1].id)
+      assert.equal('child2', passed[2].id)
+    end)
   end)
 
   describe('send_message', function()