feat: add session-wise diff support using codediff.nvim #137

naowalrahman · 2026-01-19T02:30:43Z

Using codediff.nvim, this PR enables users to pick a session to view a diff of. It compares the state of the repository at the start of the session to that after the session by somewhat reverse-engineering using opencode's snapshots feature. Since that feature only works on git repositories, this diff feature also only works on git repositories.

Changes

adds session diff to require("opencode").select menu, which can be toggled via select opts
warns users if trying to run require("opencode").session_diff without codediff.nvim installed
uses vim.ui.select to let user pick which session to diff, fetched from /session endpoint of opencode server
creates before/after temp directories for the file states from the snapshots and diffs them with codediff.nvim

Addresses #101 and #91.

Screenshots

naowalrahman · 2026-01-19T02:34:43Z

P.S. there's a type checking error between string|nil and string in diff.lua that I tried to mess around with but couldn't quite fix, so I'd appreciate any help fixing that 😅

Copilot

Pull request overview

This PR adds session-wise diff functionality to opencode.nvim using the codediff.nvim plugin. It enables users to view all changes made during an opencode session by comparing repository state snapshots from the beginning to the end of a session.

Changes:

Added session_diff command accessible via the select menu that lets users pick and diff sessions
Implemented snapshot extraction from opencode's storage to create before/after directory comparisons
Added /session API endpoint client to fetch available sessions from the opencode server

Reviewed changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated 6 comments.

Show a summary per file

File	Description
lua/opencode/diff.lua	New module implementing session diff functionality with snapshot retrieval and git tree export
lua/opencode/ui/select.lua	Added "session diff" option to the select menu when codediff.nvim is available
lua/opencode/cli/client.lua	Added `get_sessions` API function to retrieve session list from opencode server
lua/opencode/config.lua	Enabled diff section by default in select menu configuration
lua/opencode.lua	Exported `session_diff` function to public API
README.md	Added documentation for the new session diff feature

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Copilot · 2026-01-19T02:35:15Z

lua/opencode/diff.lua

+      local cleanup_group = vim.api.nvim_create_augroup("OpencodeDiffCleanup", { clear = false })
+      vim.api.nvim_create_autocmd("TabClosed", {
+        group = cleanup_group,
+        once = true,
+        callback = function()
+          vim.fn.delete(dir1, "rf")
+          vim.fn.delete(dir2, "rf")
+        end,
+      })


The autocmd group is created with clear = false, but multiple calls to session_diff() will create multiple autocmds in the same group. Each autocmd will capture different dir1/dir2 values in closures, but all autocmds will trigger on any tab close. This could lead to errors when trying to delete already-deleted directories. Consider either using clear = true or creating a unique group name per invocation, or better yet, attach the cleanup to specific buffer/window events instead of TabClosed.

Copilot · 2026-01-19T02:35:15Z

lua/opencode/diff.lua

+      -- Use CodeDiff command to compare directories
+      vim.cmd("CodeDiff " .. vim.fn.fnameescape(dir1) .. " " .. vim.fn.fnameescape(dir2))


There's no validation that the CodeDiff command executed successfully. If codediff.nvim is not properly loaded or the command fails, temp directories won't be cleaned up since the autocmd relies on a tab being created. Consider using pcall around vim.cmd or checking if the command exists before executing it, and ensure cleanup happens even on failure.

Suggested change

-- Use CodeDiff command to compare directories

vim.cmd("CodeDiff " .. vim.fn.fnameescape(dir1) .. " " .. vim.fn.fnameescape(dir2))

-- Ensure CodeDiff command is available

if vim.fn.exists(":CodeDiff") == 0 then

vim.notify("CodeDiff command not found. Is codediff.nvim installed and loaded?", vim.log.levels.ERROR, {

title = "opencode",

})

vim.fn.delete(dir1, "rf")

vim.fn.delete(dir2, "rf")

return

end

-- Use CodeDiff command to compare directories

local ok, cmd_err = pcall(vim.cmd, "CodeDiff " .. vim.fn.fnameescape(dir1) .. " " .. vim.fn.fnameescape(dir2))

if not ok then

vim.notify("Failed to run CodeDiff: " .. tostring(cmd_err), vim.log.levels.ERROR, { title = "opencode" })

vim.fn.delete(dir1, "rf")

vim.fn.delete(dir2, "rf")

return

end

Copilot · 2026-01-19T02:35:15Z

lua/opencode/diff.lua

+local function export_tree(snapshot_git, tree_hash, callback)
+  -- Create temp directory
+  local temp_dir = vim.fn.tempname()
+  vim.fn.mkdir(temp_dir, "p")
+
+  -- Verify the object exists
+  vim.system({ "git", "--git-dir=" .. snapshot_git, "cat-file", "-t", tree_hash }, { text = true }, function(result)
+    if result.code ~= 0 then
+      vim.schedule(function()
+        callback("Snapshot object no longer exists (may have been garbage collected): " .. tree_hash, nil)
+      end)
+      return
+    end
+
+    -- Export the tree using git archive
+    vim.system({ "git", "--git-dir=" .. snapshot_git, "archive", tree_hash }, { text = false }, function(archive_result)
+      if archive_result.code ~= 0 then
+        vim.schedule(function()
+          callback("Failed to archive tree: " .. (archive_result.stderr or ""), nil)
+        end)
+        return
+      end
+
+      -- Extract the archive
+      vim.system(
+        { "tar", "-xf", "-", "-C", temp_dir },
+        { stdin = archive_result.stdout, text = false },
+        function(tar_result)
+          vim.schedule(function()
+            if tar_result.code ~= 0 then
+              callback("Failed to extract archive: " .. (tar_result.stderr or ""), nil)
+            else
+              callback(nil, temp_dir)
+            end
+          end)
+        end
+      )
+    end)
+  end)
+end


The implementation uses Unix-specific commands (git, tar) and assumes Unix-style paths ($HOME/.local/share). This feature will likely not work on Windows systems. Consider adding a platform check and providing appropriate error messaging for Windows users, or implement Windows-compatible alternatives.

Copilot · 2026-01-19T02:35:15Z

lua/opencode/diff.lua

+  vim.system({ "git", "--git-dir=" .. snapshot_git, "cat-file", "-t", tree_hash }, { text = true }, function(result)
+    if result.code ~= 0 then
+      vim.schedule(function()
+        callback("Snapshot object no longer exists (may have been garbage collected): " .. tree_hash, nil)
+      end)
+      return
+    end
+
+    -- Export the tree using git archive
+    vim.system({ "git", "--git-dir=" .. snapshot_git, "archive", tree_hash }, { text = false }, function(archive_result)
+      if archive_result.code ~= 0 then
+        vim.schedule(function()
+          callback("Failed to archive tree: " .. (archive_result.stderr or ""), nil)
+        end)
+        return
+      end


If the git cat-file or git archive commands fail after creating the temp directory, that directory is not cleaned up. The temp_dir created at line 133-134 should be deleted in the error paths at lines 140 and 149 to prevent temporary directory leaks.

Copilot · 2026-01-19T02:35:16Z

lua/opencode/diff.lua

+      local cleanup_group = vim.api.nvim_create_augroup("OpencodeDiffCleanup", { clear = false })
+      vim.api.nvim_create_autocmd("TabClosed", {
+        group = cleanup_group,
+        once = true,
+        callback = function()
+          vim.fn.delete(dir1, "rf")
+          vim.fn.delete(dir2, "rf")
+        end,
+      })


The TabClosed autocmd may not reliably clean up temporary directories. If the user closes the diff buffers or windows without closing the tab (e.g., using :bdelete or :close), the temporary directories will not be cleaned up and will persist on disk. Consider using BufDelete or WinClosed events on the specific buffers/windows created by CodeDiff, or track the tab number with vim.api.nvim_get_current_tabpage() and match it in the autocmd pattern.

Copilot · 2026-01-19T02:35:16Z

lua/opencode/diff.lua

+local STORAGE = vim.fn.expand("$HOME/.local/share/opencode/storage")
+local SNAPSHOT_DIR = vim.fn.expand("$HOME/.local/share/opencode/snapshot")
+


The hardcoded storage paths assume the opencode server uses the default XDG data directory. If the opencode server is configured with a custom storage location (e.g., via environment variables or configuration), this implementation will fail to find the snapshots. Consider making these paths configurable or detecting them from the opencode server's configuration.

Suggested change

local STORAGE = vim.fn.expand("$HOME/.local/share/opencode/storage")

local SNAPSHOT_DIR = vim.fn.expand("$HOME/.local/share/opencode/snapshot")

---Resolve the base data directory used by the opencode server.

---Order of precedence:

--- 1. OPENCODE_DATA_DIR environment variable

--- 2. vim.g.opencode_data_dir global (if set by config)

--- 3. $XDG_DATA_HOME/opencode (if XDG_DATA_HOME is set)

--- 4. $HOME/.local/share/opencode (current default)

---@return string

local function get_opencode_data_dir()

-- Explicit override via environment variable

local env_dir = vim.env.OPENCODE_DATA_DIR

if env_dir and env_dir ~= "" then

return vim.fn.expand(env_dir)

end

-- Optional override via Neovim global (can be set in user config)

local global_dir = vim.g.opencode_data_dir

if type(global_dir) == "string" and global_dir ~= "" then

return vim.fn.expand(global_dir)

end

-- Respect XDG data home if available

local xdg_data_home = vim.env.XDG_DATA_HOME

if xdg_data_home and xdg_data_home ~= "" then

return xdg_data_home .. "/opencode"

end

-- Fallback to the original hardcoded default

return vim.fn.expand("$HOME/.local/share/opencode")

end

local OPENCODE_DATA_DIR = get_opencode_data_dir()

local STORAGE = OPENCODE_DATA_DIR .. "/storage"

local SNAPSHOT_DIR = OPENCODE_DATA_DIR .. "/snapshot"

naowalrahman · 2026-01-20T02:55:10Z

A few changes with the last 3 commits:

fixed the LSP error so all checks pass now
removed temp directory cleanup all together because they get erased when you close neovim anyway
allow users to set their opencode data directory in opts, eliminating cross-platform storage directory differences

naowalrahman added 2 commits January 18, 2026 18:27

reference files for later

40977cb

feat: add session diff support using codediff.nvim

a1aa764

Copilot AI review requested due to automatic review settings January 19, 2026 02:30

Copilot started reviewing on behalf of naowalrahman January 19, 2026 02:31 View session

Copilot AI reviewed Jan 19, 2026

View reviewed changes

naowalrahman mentioned this pull request Jan 19, 2026

Add diff viewing #91

Draft

12 tasks

naowalrahman added 3 commits January 19, 2026 21:38

fix: improve session diff robustness and configurability

b303625

fix: improve session diff error reporting and command execution

2befc29

refactor: remove unnecessary temp directory cleanup in diff.lua

037d991

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feat: add session-wise diff support using codediff.nvim #137

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		-- Use CodeDiff command to compare directories
		vim.cmd("CodeDiff " .. vim.fn.fnameescape(dir1) .. " " .. vim.fn.fnameescape(dir2))

		local STORAGE = vim.fn.expand("$HOME/.local/share/opencode/storage")
		local SNAPSHOT_DIR = vim.fn.expand("$HOME/.local/share/opencode/snapshot")

-local STORAGE = vim.fn.expand("$HOME/.local/share/opencode/storage")
-local SNAPSHOT_DIR = vim.fn.expand("$HOME/.local/share/opencode/snapshot")
+---Resolve the base data directory used by the opencode server.
+---Order of precedence:
+---  1. OPENCODE_DATA_DIR environment variable
+---  2. vim.g.opencode_data_dir global (if set by config)
+---  3. $XDG_DATA_HOME/opencode (if XDG_DATA_HOME is set)
+---  4. $HOME/.local/share/opencode (current default)
+---@return string
+local function get_opencode_data_dir()
+  -- Explicit override via environment variable
+  local env_dir = vim.env.OPENCODE_DATA_DIR
+  if env_dir and env_dir ~= "" then
+    return vim.fn.expand(env_dir)
+  end
+  -- Optional override via Neovim global (can be set in user config)
+  local global_dir = vim.g.opencode_data_dir
+  if type(global_dir) == "string" and global_dir ~= "" then
+    return vim.fn.expand(global_dir)
+  end
+  -- Respect XDG data home if available
+  local xdg_data_home = vim.env.XDG_DATA_HOME
+  if xdg_data_home and xdg_data_home ~= "" then
+    return xdg_data_home .. "/opencode"
+  end
+  -- Fallback to the original hardcoded default
+  return vim.fn.expand("$HOME/.local/share/opencode")
+end
+local OPENCODE_DATA_DIR = get_opencode_data_dir()
+local STORAGE = OPENCODE_DATA_DIR .. "/storage"
+local SNAPSHOT_DIR = OPENCODE_DATA_DIR .. "/snapshot"

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naowalrahman commented Jan 19, 2026

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