unterm.conf reference

unterm.conf is Unterm’s terminal config: fonts, colours, window chrome, the shell, scrollback, the MCP confirmation policy, environment variables and key bindings. The other files in ~/.unterm/ (proxy, theme, language, recording) are covered in Configuration files.

Where the file lives

• Path: ~/.unterm/unterm.conf. On Windows that is %USERPROFILE%\.unterm\unterm.conf. If UNTERM_STATE_DIR is set and not empty, the file is $UNTERM_STATE_DIR/unterm.conf instead.
• Another file: the GUI accepts --config <file>, -c <file> or --config=<file>. A bare file path on the command line (for example, a file dropped on the app icon) is also read as the config. unterm-core takes no such flag and always reads the default path.
• No file: no error. Every key takes its built-in default.
• Encoding: UTF-8. A leading byte-order mark, which Notepad and Set-Content -Encoding utf8 add, is removed before parsing.
• Packaged copy: the installers put a copy of the project’s default config (assets/unterm.conf) inside the app bundle. The current code reads only the path above, so with no ~/.unterm/unterm.conf, the built-in defaults in the tables below apply, not the values in that copy. Where the two differ, the tables give both.

When changes take effect

The config is read once, when the process starts. Nothing watches the file, so edits apply on the next start.

• The GUI (unterm) reads it at startup for everything in this document.
• unterm-core, the background process that owns the terminal sessions and serves MCP, reads it at its own startup. It uses scrollback_lines, shell, quick_select_alphabet, [window] initial_cols/initial_rows, color_scheme, [mcp] and [cockpit]. The Core keeps running when you close the window, so those keys change only after the Core restarts. A window that reconnects to a running Core does not restart it.
• [env] and path_append are set on the GUI process before it starts or connects to the Core. A Core started by that window inherits them. A Core that was already running keeps the environment it started with.

Errors and warnings

• Parse errors (a missing quote, an unquoted string, an unclosed list, a key set twice) make the whole file ignored. Unterm starts on built-in defaults and logs each error with its line number. A key set twice is an error, not “last one wins”.
• Unknown keys do not stop the rest of the file from applying. Each one is logged as a warning with its line number, plus the closest real key when one is near enough (unknown setting 'font_sze' -- did you mean 'font_size'?). Names under [env] and [keys] are never treated as unknown.
• Checked values: line_height must be between 0.1 and 10, window.background_opacity between 0 and 1, tab_bar.title_format may only use the {title} and {index} placeholders, and every hyperlink_rules entry must have the right shape. A failed check is a warning. It does not stop the rest of the file from loading.
• Wrong types: outside those checks, a value of the wrong type (for example, font_size = "big") is usually ignored without a warning, and the key keeps its default.

The GUI writes these messages to its log as config line N: …. unterm-core prints them to stderr as unterm-core: config line N: ….

A small example

# ~/.unterm/unterm.conf
font_family = "JetBrains Mono"
font_fallback = ["PingFang SC", "Symbols Nerd Font Mono"]
font_size = 13
line_height = 1.15
scrollback_lines = 50000

[window]
initial_cols = 120
initial_rows = 30
padding_left = 12

[visual_bell]
fade_in_duration_ms = 75
fade_out_duration_ms = 150

[mcp]
input_confirmation = "first_time_per_agent"
trusted_agents = ["claude"]

[env]
EDITOR = "vim"

[keys]
CTRL|SHIFT+T = "NewTab"
F11 = "None"

Syntax

The format is line-based key = value, with [section] headers. Parser: unterm-engine/src/next_core/config.rs.

Sections. [name] prefixes every key after it with name. until the next header. A header can contain dots, and so can a key, so these three spell the same key:

[colors.tab_bar.active_tab]
bg_color = "#2b2d31"

[colors]
tab_bar.active_tab.bg_color = "#2b2d31"

# (at the top of the file, before any header)
colors.tab_bar.active_tab.bg_color = "#2b2d31"

Only one of those can appear in a file, because setting a key twice is an error. Keys before the first header are top-level.

Comments. # starts a comment anywhere on a line, except inside a quoted string. "#1e1e2e" is a colour, not a comment. Blank lines are ignored.

Values.

Type	Written as	Notes
Boolean	true, false	Lowercase only.
Integer	13, -1, 50000	64-bit signed.
Number	1.15, 0.5	An integer is accepted where a number is expected (font_size = 12 means 12.0).
String	"text"	Double quotes only. Escapes: \n, \t, \r, \\, \". Any other backslash is kept as written, so "C:\Users\me\pwsh.exe" works without doubling. But \n, \t, \r are still escapes inside a path: "C:\Program Files\nodejs" contains a newline and "C:\tools" a tab. Double the backslash there ("C:\Program Files\\nodejs") or use forward slashes.
List	["a", "b", 3]	Items can be of any type, including nested lists. A list may span several lines, with comments and a trailing comma.

An unquoted word such as font_family = Cascadia is a parse error. The message suggests the quoted form.

Platform sections. The format defines [platform.windows], [platform.macos], [platform.linux] and [platform.other]. Keys inside them are meant to apply only on that platform: the base value first, then [platform.other] (used only when the file has no section for the current platform), then the named platform’s section. assets/unterm.conf uses them for title_button.* and the Windows path_append.

Caveat, current build: the config loader (unterm-services/src/settings.rs load()) does not apply this platform logic. No production code calls Config::resolve_platform. A key such as [platform.windows] path_append is therefore stored as platform.windows.path_append, logged as an unknown setting, and has no effect on any platform. Until that changes, put platform-specific values in the main part of the file.

Top-level keys

Key	Type	Default	What it does
font_family	string	none (bundled JetBrains Mono)	The terminal font family, at its regular weight. If the family is not installed, a warning is logged and the default is used. If the bundled font cannot be opened, the system’s default monospace font is used.
font_fallback	list of strings	[]	Families to try, in order, for characters the main font lacks (for example, CJK or Nerd Font icons). They are tried before the built-in fallback list. Non-string entries are skipped. The packaged copy lists PingFang SC, Microsoft YaHei, Noto Sans CJK SC, Noto Sans Mono CJK SC and Symbols Nerd Font Mono.
font_size	number	13	The font size in points. Values below 6 become 6.
line_height	number	1.0 (packaged copy: 1.15)	Multiplies the font’s line height. The value used is clamped to 0.5–4.0. The checker warns outside 0.1–10.
color_scheme	string	none (packaged copy: "Unterm Dark")	Recorded in settings and reported by MCP (terminal.color_scheme). It does not change any colours: those come from the theme (~/.unterm/theme.json, the theme picker) and [colors].
scrollback_lines	integer	scrollback.json, otherwise 10000 (packaged copy: 50000)	Scrollback lines kept for each pane created after startup. Accepted range: 0–999,999,999. If the key is missing, negative, too large or not an integer, the lines value in ~/.unterm/scrollback.json is used, and if that is missing too, 10,000. Scrollback stays in memory, so large values on many panes use a lot of RAM.
enable_scroll_bar	bool	true	Shows the scroll bar beside each pane.
text_blink_rate	number (ms)	500	How fast text with the SGR 5 (slow blink) attribute blinks. 0 stops it blinking. Negative values count as 0.
text_blink_rate_rapid	number (ms)	250	The same for SGR 6 (rapid blink).
hyperlink_rules	list of rules	built-in rules	Rules that turn printed text into clickable links. Each rule is ["regex", "format"] or ["regex", "format", capture]. In the format, $0 is the whole match and $1 the first group. capture is the group drawn as the link (default 0). Setting this key replaces all built-in rules (bare and bracketed URLs, email addresses), and [] turns link detection off. A rule whose regex does not compile is skipped with a warning.
quick_select_alphabet	string	"asdfqwerzxcvjklmiuopghtybn"	Letters used for Quick Select labels (Ctrl+Shift+S). Converted to lowercase. It must have at least 8 characters, no whitespace and no repeats. Otherwise a warning is logged and the default is used.
shell	string or list of strings	platform default	The program new panes start. A string is one program path with no arguments. Use a list for arguments: ["pwsh.exe", "-NoLogo"]. If unset, Windows uses PowerShell 7 (pwsh.exe -NoLogo -NoProfile) when it is found, otherwise powershell.exe -NoLogo -NoProfile. macOS and Linux use the login shell from the user database, or /bin/sh. The Web Settings “default shell” control writes this key.
path_append	list of strings	[]	Directories added to the end of PATH at startup, skipping ones already there (without regard to case on Windows). Shells, agent discovery and the Core started by this window all see the result. On Windows, Unterm also adds C:\Program Files\nodejs, C:\Strawberry\perl\bin, %APPDATA%\npm and %USERPROFILE%\.bun\bin when those directories exist, whether or not this key is set.
shell_integration	bool	true	Load Unterm’s shell integration into the zsh, bash, fish and PowerShell sessions it starts, without touching your own startup files. It gives Unterm prompt and command marks (OSC 133) with exit codes, and the working directory (OSC 7). false starts shells exactly as configured. See Shell integration.
audible_bell	string	on	Whether the bell also beeps. "Disabled" (any case) turns the beep off, and any other string leaves it on. The value must be a string: audible_bell = false is ignored, so the beep stays on. The beep is the Windows system sound (MessageBeep). On macOS and Linux nothing is played.
status_bar	bool	false	Shows a status strip below the terminal. Off by default. It is read once at startup so that the number of terminal rows does not change while running.
window_background_image	string (file path)	none	A picture drawn behind the terminal. It is scaled to cover the window and cropped from the centre. Its opacity comes from [window] background_opacity. A missing or unreadable file is logged and skipped.
use_ime	bool	—	Accepted but currently has no effect. The input method is always enabled for the window.

[colors]

Colours are hex strings: "#rrggbb", "#rgb", or the same without #. A value that is not valid hex is ignored.

Key	Type	Default	What it does
background	colour	the theme’s background (packaged copy: "#111315")	The terminal background. It overrides the active theme’s background even after you pick another theme.
foreground	colour	the theme’s foreground (packaged copy: "#e8eaed")	The default text colour. It also overrides the theme.
tab_bar_lift	number	— (packaged copy: 0.05)	Accepted but currently has no effect.
inactive_dim	number	— (packaged copy: 0.35)	Accepted but currently has no effect.

[colors.tab_bar] and its subsections

These colour the title bar and tab strip. They are applied on top of the computed chrome colours.

Key	Type	Default	What it does
[colors.tab_bar] background	colour	computed	The bar surface (title bar, footer, group background). Used only when [window_frame] active_titlebar_bg is not set.
[colors.tab_bar.active_tab] bg_color	colour	computed	Background of the selected row or tab.
[colors.tab_bar.active_tab] fg_color	colour	theme foreground	The bar’s text colour in a focused window. Used only when [window_frame] active_titlebar_fg is not set. Like all chrome text colours, it applies only while no theme has been picked (see [window_frame]).
[colors.tab_bar.inactive_tab] bg_color	colour	—	Accepted but currently has no effect.
[colors.tab_bar.inactive_tab] fg_color	colour	computed	Colour of dimmed (secondary) text in the bar. Falls back to [window_frame] inactive_titlebar_fg.
[colors.tab_bar.inactive_tab_hover] bg_color	colour	computed	The hover background in the bar. Falls back to [window_frame] button_hover_bg.
[colors.tab_bar.inactive_tab_hover] fg_color	colour	—	Accepted but currently has no effect.
[colors.tab_bar.new_tab] bg_color	colour	—	Accepted but currently has no effect.
[colors.tab_bar.new_tab] fg_color	colour	—	Accepted but currently has no effect.
[colors.tab_bar.new_tab_hover] bg_color	colour	—	Accepted but currently has no effect.
[colors.tab_bar.new_tab_hover] fg_color	colour	—	Accepted but currently has no effect.

[window_frame]

Title bar and window-button colours, as hex strings. These win over the matching [colors.tab_bar] keys. The foreground keys (active_titlebar_fg, inactive_titlebar_fg) apply only when no theme has been picked. Once a theme is chosen, the bar text uses the theme’s foreground, at 70% alpha in an unfocused window.

Key	Type	Default	What it does
active_titlebar_bg	colour	computed	Bar surface in the focused window.
active_titlebar_fg	colour	theme foreground	Bar text in the focused window.
inactive_titlebar_bg	colour	active_titlebar_bg	Bar surface in an unfocused window.
inactive_titlebar_fg	colour	active_titlebar_fg	Bar text in an unfocused window. It is also the fallback for dimmed text.
active_titlebar_border_bottom	colour	computed	The window’s outer edge line when focused.
inactive_titlebar_border_bottom	colour	active_titlebar_border_bottom	The outer edge line when unfocused.
button_bg	colour	—	Accepted but currently has no effect.
button_fg	colour	style default	Glyph colour of the drawn minimise, maximise and close buttons.
button_hover_bg	colour	style default	Hover fill of the minimise and maximise buttons (not close). It is also the fallback hover background for the bar.
button_hover_fg	colour	button_fg	Button glyph colour on hover (not for the close button).

[visual_bell]

With both durations at 0 (the default), the screen does not flash when the bell rings.

Key	Type	Default	What it does
fade_in_duration_ms	number (ms)	0	How long the flash takes to reach full strength.
fade_out_duration_ms	number (ms)	0	How long it takes to fade back.
fade_in_function	string	"Ease"	Easing curve for the fade-in: Linear, Ease, EaseIn, EaseInOut, EaseOut or Constant (any case). An unknown name means Ease.
fade_out_function	string	"Ease"	Easing curve for the fade-out. It takes the same names.
target	string	"BackgroundColor"	What flashes: BackgroundColor (the pane background) or CursorColor (the cursor cell). Any value other than CursorColor (any case) means BackgroundColor.

[window]

Key	Type	Default	What it does
background_opacity	number 0–1	0.25 (packaged copy: 1.0)	How strongly window_background_image shows. The value used is capped at 0.5 so text stays readable. It has no effect without a background image and does not make the window transparent. The older top-level spelling window_background_opacity is also read.
backdrop	string	off	"mica", "on" or "true" (any case, written as a string) asks for the Windows 11 Mica backdrop. It applies only on Windows with DX12, with decorations off and no background image. It does nothing on other platforms.
decorations	bool	false	true uses the operating system’s title bar and frame. false lets Unterm draw its own. The packaged copy sets the string "INTEGRATED_BUTTONS|RESIZE", which is not a boolean, so it is ignored and behaves as false.
initial_cols	integer	80 (packaged copy: 120)	Columns for the first window’s terminal area. Values below 1 become 1.
initial_rows	integer	24 (packaged copy: 30)	Rows for the first window. Values below 1 become 1.
padding_left	number (logical px)	12	Space between the window edge and the text. Negative values become 0.
padding_right	number	12	Same, right side.
padding_top	number	8	Same, top.
padding_bottom	number	8	Same, bottom.
close_confirmation	string	— (packaged copy: "NeverPrompt")	Accepted but currently has no effect. The code reads the top-level key window_close_confirmation instead (see Keys read outside the schema). The unterm.lua conversion writes this key, so a converted setting also has no effect.

[inactive_pane]

Multipliers applied to the colours of panes that do not have focus, in hue, saturation and brightness (HSB). At 1.0 for all three (the default), inactive panes are not changed. Negative values become 0.

Key	Type	Default	What it does
hue	number	1.0	Multiplies the hue. The result wraps around the colour wheel.
saturation	number	1.0	Multiplies the saturation.
brightness	number	1.0	Multiplies the brightness. For example, 0.6 dims unfocused panes.

[tab_bar]

None of these keys is read by the current front end. Tab titles come from fixed rules: a name you gave the tab, otherwise the pane’s title or foreground program with .exe removed, otherwise shell. The keys are kept so that configs converted from unterm.lua do not produce warnings.

Key	Type	Default	What it does
position	string	— (packaged copy: "Left")	Accepted but currently has no effect.
max_width	integer	— (packaged copy: 32)	Accepted but currently has no effect.
hide_if_only_one_tab	bool	—	Accepted but currently has no effect.
show_index	bool	—	Accepted but currently has no effect.
show_new_tab_button	bool	—	Accepted but currently has no effect.
title_format	string	— (packaged copy: " {title} ")	Accepted but currently has no effect. It is still checked: placeholders other than {title} and {index} cause a warning.
fallback_title	string	—	Accepted but currently has no effect.
strip_extension	bool	—	Accepted but currently has no effect.
capitalize	bool	—	Accepted but currently has no effect.

[stats]

Key	Type	Default	What it does
refresh_ms	integer (ms)	1000	How often the facts line in the top bar is refreshed: bound agent, git branch, CPU and memory, and the running command. Clamped to 250–60,000. It must be an integer: 1000.0 is ignored. GUI only.

[mcp]

These control how agents connected over MCP may drive the terminal. They are read by the process that serves MCP, which is normally unterm-core.

Key	Type	Default	What it does
input_confirmation	string	"first_time_per_agent"	When an agent writing to a pane needs your approval in a banner. "never": no banner. "always": a banner for every write. "first_time_per_agent": ask the first time each agent writes, then remember. Any other value keeps first_time_per_agent. "never" also skips approval of destructive MCP actions. Writes made by unterm-cli itself never raise a banner.
trusted_agents	string or list of strings	[]	Agent names that never need confirmation, for pane writes or for destructive actions.
confirmation_timeout_ms	integer (ms)	30000	How long a confirmation banner waits before it counts as a denial. Values below 1000 are raised to 1000. unterm-cli also uses this value to wait for a confirmed call.
suggest_default_ttl_ms	integer (ms)	300000	How long a suggestion an agent posts stays valid when the agent does not give its own ttl_ms.
suggest_queue_capacity	integer	32	Most pending suggestions kept. The oldest are dropped first. Values below 8 are raised to 8.
audit_log_capacity	integer	1000	Entries kept in the in-memory MCP audit log, including entries reloaded from disk at startup. Values below 16 are raised to 16.

[cockpit]

The agent cockpit tracks which agent runs in which pane and what it is doing. Its inbox opens with Ctrl+Shift+A.

Key	Type	Default	What it does
enabled	bool	true	Turns agent status tracking on or off. When it is off, the MCP agent.status call returns {"enabled": false, "agents": []}.
auto_checkpoint	bool	true	Takes a git snapshot of the pane’s repository when an agent starts working, so you can review what it changed.
done_hold_secs	integer (s)	20	How long an agent stays “done” before it returns to “idle”.

[title_button]

None of these keys is read by the current front end. The packaged copy sets them in [platform.*] sections, which the current build does not apply either (see Syntax).

Key	Type	Default	What it does
style	string	—	Accepted but currently has no effect.
alignment	string	—	Accepted but currently has no effect.
buttons	list of strings	—	Accepted but currently has no effect.

[env]

Every key in [env] is an environment variable name, and its value must be a string.

[env]
EDITOR = "vim"
LANG = "en_US.UTF-8"

At startup the GUI sets each variable on its own process. New panes inherit them, along with agents launched from the terminal and a Core started by this window. A non-string value (COUNT = 3) is not exported and is logged with its line number. Values are used literally: $HOME and %USERPROFILE% are not expanded. Any variable name is accepted, and names under [env] never produce unknown-setting warnings.

[keys]

[keys] changes key bindings. Each line is chord = "Action":

[keys]
CTRL|SHIFT+T = "NewTab"          # replace (here: restate) a built-in binding
CTRL|ALT+Left = "FocusPaneLeft"  # add a new chord
ALT+Equal = "IncreaseFontSize"   # `=` cannot be written directly
F11 = "None"                     # unbind: F11 goes to the shell

Chord syntax. Modifier names, then the key, separated by | or + (CTRL|SHIFT+T and CTRL+SHIFT+T are the same). Names are case-insensitive.

• Modifiers: CTRL (or CONTROL), SHIFT, ALT (or OPT, META), and NONE, which means no modifier. Any other name is an error. Only Ctrl, Shift and Alt are checked when a key is pressed. There is no Cmd, Super or Win modifier, and on macOS CTRL means the Control key, not Command.
• Keys: any single character (letters match either case, so CTRL+t = CTRL+T), Left, Right, Up, Down, PageUp, PageDown, Tab, Space, F1–F12, and Equal (or Equals), Plus, Minus for =, + and -. Those three need names because = ends the key and + separates modifiers. Other key names (Enter, Escape, Home, F13 and so on) are errors.
• Matching is exact. A binding for CTRL+T does not fire for Ctrl+Shift+T.

Values. The value is an action name (case-insensitive), or "None" to unbind.

• A chord that has a built-in binding is replaced by your entry.
• A new chord adds a binding.
• "None" removes the binding, so the keystroke goes to the program in the pane.

Bindings from [keys] are checked before the built-in ones. The command palette’s shortcut hints and the MCP meta.keybindings reply show the merged result. A bad chord, an unknown action or a non-string value is logged with its line number and skipped. The other entries still apply. Two spellings of the same chord (CTRL+T and ctrl+t) are different keys to the parser, so both load. Avoid that.

Actions.

Action	Built-in chord
Copy	Ctrl+Shift+C
Paste	Ctrl+Shift+V
SplitRight	Ctrl+Shift+D
SplitDown	Ctrl+Shift+E
ScrollPageUp / ScrollPageDown	Shift+PageUp / Shift+PageDown
PreviousPrompt / NextPrompt	Ctrl+Shift+Up / Ctrl+Shift+Down
NewTab	Ctrl+Shift+T
NextTab / PreviousTab	Ctrl+Tab / Ctrl+Shift+Tab
CloseTab	Ctrl+Shift+W
Search	Ctrl+Shift+F
CommandPalette	Ctrl+Shift+P
Launcher	Ctrl+Shift+L and Ctrl+Shift+N
CopyMode	Ctrl+Shift+X
QuickSelect	Ctrl+Shift+S
Insights	Ctrl+Shift+I
CockpitInbox	Ctrl+Shift+A
GitPanel	Ctrl+Shift+G
Composer	Ctrl+Shift+J
ThemePicker	—
LeftTabBar	—
DirJump	—
NewWindow	Ctrl+Shift+Alt+N
NewAdminWindow	— (Windows only)
ClosePane	Ctrl+Shift+Q
ZoomPane	Ctrl+Shift+Z
Settings	—
CharSelect	Ctrl+Shift+U
TreeSidebar	Ctrl+Shift+B
FleetLaunch	Ctrl+Shift+Alt+A
ClearScrollback	Ctrl+Shift+K
ClearScreen	Ctrl+Shift+Alt+K
SelectPane	Ctrl+Shift+‘
SwapPane	Ctrl+Shift+Alt+‘
FocusPaneLeft / Right / Up / Down	Alt+arrow
ResizePaneLeft / Right / Up / Down	Shift+Alt+arrow
MoveTabLeft / MoveTabRight	Ctrl+Shift+PageUp / Ctrl+Shift+PageDown
SelectTab1 … SelectTab9	Ctrl+1 … Ctrl+9 (SelectTab9 goes to the last tab)
IncreaseFontSize	Ctrl+= and Ctrl++
DecreaseFontSize	Ctrl+-
ResetFontSize	Ctrl+0
ToggleFullScreen	F11

Plain Ctrl+C is not bound. It always reaches the shell as an interrupt.

Keys read outside the schema

The code also reads the keys below, but the schema does not list them. They work, and each one also logs an “unknown setting” warning.

Key	Type	Default	What it does
theme	string	the theme picked in the picker	Theme id for terminal colours. It takes priority over the theme picker.
font	string	—	An early spelling of font_family, used only when font_family is not set.
cell_width	number	1.0	Multiplies the cell width. Clamped to 0.5–4.0.
default_cursor_style	string	block, steady	SteadyBlock, BlinkingBlock, SteadyUnderline, BlinkingUnderline, SteadyBar or BlinkingBar. Anything else means a steady block.
cursor_blink_rate	number (ms)	800	Blink speed of a blinking cursor. 0 turns blinking off.
default_cwd	string (path)	none	Directory a new session starts in when no --cwd (or restored directory) is given.
window_close_confirmation	string	asks	"NeverPrompt" (any case) closes without asking. Any other value keeps the prompt shown when closing would end tabs or running programs.
window_background_opacity	number	—	Older spelling of [window] background_opacity, used only when that key is not set.
top_bar	string	compact	"full" uses the full-height top bar. Any other value, or no value, keeps the compact one.

Migrating from unterm.lua

Releases before the declarative config read a Lua file. On startup, the GUI converts that file once, when all of these are true:

1. ~/.unterm/unterm.conf does not exist. An existing unterm.conf is never overwritten.
2. One of these files exists. The first match is used:
   • ~/.config/unterm/unterm.lua
   • ~/.unterm/unterm.lua (inside the state directory)
   • ~/.unterm.lua
   • ~/.wezterm.lua

The converted text is written to ~/.unterm/unterm.conf. The Lua file is not changed. Each line that could not be converted is logged as not converted: … with its line number and the reason. unterm-core does not convert. Only the GUI does.

What converts (unterm-engine/src/next_core/config_migrate.rs):

• Plain assignments of booleans, numbers, strings and flat lists, written as config.x = …, config['x'] = …, M.x = … or a bare x = … inside the returned table.
• Nested tables opened on their own line become sections (colors = { → [colors]).
• wezterm.font("Name") with a single literal name becomes font_family.
• One-line window_padding = { left = …, … } becomes [window] padding_left and the other sides.
• One-line inactive_pane_hsb = { … } becomes [inactive_pane] hue, saturation and brightness.
• if/elseif/else branches on wezterm.target_triple become [platform.macos], [platform.windows], [platform.linux] and [platform.other]. As noted under Syntax, the current build does not apply those sections. Move the values you need out of them by hand.
• Old names are renamed: initial_cols and initial_rows → [window]; window_close_confirmation → [window] close_confirmation; window_background_opacity → [window] background_opacity; window_decorations → [window] decorations; tab_bar_position, tab_max_width, hide_tab_bar_if_only_one_tab, show_tab_index_in_tab_bar and show_new_tab_button_in_tab_bar → [tab_bar]; the integrated_title_button_* keys → [title_button]; status_update_interval → [stats] refresh_ms.
• check_for_updates, win32_system_backdrop, show_unterm_status_bar and use_fancy_tab_bar are dropped without a report, because the new front end has fixed behaviour for them.

What is reported instead of converted: functions (including key bindings and event handlers written as Lua callbacks), anything inside other if/for/do blocks, local variables, calls into wezterm.* or require, strings built with .., tables with named fields written on one line, and a key that ends up set twice (for example, by two platform branches). Re-create these by hand, using [keys] for bindings and [env] for set_environment_variables.

After the conversion, check the log for unknown-setting warnings. Some converted keys, such as [window] close_confirmation and the [tab_bar] keys, are accepted but currently have no effect, as the tables above note.