Rules

Manage persisted window rules that control layout behavior, default workspace placement, and the initial Niri container primary span for matching windows. Primary span is width in horizontal orientation and height in vertical orientation. Rule add, replace, and config reload trigger automatic reevaluation. A valid workspace assignment applies as the initial default whenever the matching app currently has no tracked windows. Additional windows use the workspace active when creation began. Automatic reevaluation preserves existing managed windows’ workspaces, while readmission, structural replacements, tracked transient children, and unique persisted boot-restore matches preserve placement continuity. rule apply is the explicit path that may move existing managed windows. Initial container primary span is a one-shot Niri admission hint and never resizes an existing container.

omniwmctl rule <action> [arguments...] [options...]

Rule Options

Option	Value	Description
--bundle-id	<bundle-id>	Application bundle identifier. Optional: omit it to match apps with no runtime bundle ID, but then supply at least one of --app-name-substring / --title-substring / --title-regex
--app-name-substring	<text>	Match app name containing this substring
--title-substring	<text>	Match window title containing this substring
--title-regex	<pattern>	Match window title against this regex
--ax-role	<role>	Match accessibility role
--ax-subrole	<subrole>	Match accessibility subrole
--layout	<auto|tile|float>	Layout action (auto = default behavior)
--assign-to-workspace	<raw-name>	Use this workspace as the initial default whenever the matching app currently has no tracked windows
--initial-container-primary-span	<proportion>	Initial Niri container primary span for a resizable window, from 0.05 through 1.0 inclusive
--min-width	<points>	Minimum window width in points
--min-height	<points>	Minimum window height in points

When supplied, bundle IDs must match the pattern: ^[a-zA-Z0-9]+([.-][a-zA-Z0-9]+)*$. Every rule needs at least one identifier — a bundle ID, app-name substring, or title (substring/regex). The bundle ID is the app’s runtime identifier (NSRunningApplication.bundleIdentifier); apps without one (e.g. ad-hoc or wrapper apps) are matched by app name and/or title. AX role/subrole refine an existing match but cannot identify a rule on their own. Title substring and title regex are mutually exclusive, and a supplied regex must compile. Every rule also needs at least one effect: a layout other than auto, a workspace assignment, an initial container primary span, or a minimum width or height. Minimum sizes must be positive and finite.

initialContainerPrimarySpan is stored and returned over IPC as a proportion. omniwmctl query rules renders it as a percentage in human-readable table or text output. It applies only when a matching resizable window creates or claims a new Niri container, and the user can resize that container afterward.

Niri’s Single Window Fit policy retains precedence for a lone window, so it can visually mask the seeded primary span. Physical minimum-size constraints can clamp the resolved span in pixels, but they do not rewrite the stored initialContainerPrimarySpan proportion.

Rule Actions

Add a rule:

omniwmctl rule add [options...]

Supply --bundle-id and/or at least one matcher (--app-name-substring, --title-substring, --title-regex). Appends a new rule to the end of the rule list. Its placement defaults apply whenever the matching app currently has no tracked windows; already managed windows are not moved.

Replace a rule:

omniwmctl rule replace <rule-id> [options...]

Replaces a rule in-place by its UUID (same identifier requirement as add). The rule ID is preserved. Already managed windows are not moved until rules are explicitly applied.

Remove a rule:

omniwmctl rule remove <rule-id>

Removes a rule by its UUID.

Move a rule:

omniwmctl rule move <rule-id> <position>

Moves a rule to a new one-based position in the rule list.

Apply rules:

omniwmctl rule apply [--focused | --window <opaque-id> | --pid <pid>]

Re-evaluates the current rule set against the target. Defaults to --focused if no target is specified. This is the explicit path for applying ongoing rule effects to already managed windows; the one-shot initial container primary-span hint is not reasserted on an existing container. Explicit application may move an existing window to its valid assigned workspace.

Target	Description
--focused	Apply to the currently focused window (default)
--window <id>	Apply to a specific window by opaque ID
--pid <pid>	Apply to all managed windows for a process

Examples:

# Float all Finder windows
omniwmctl rule add --bundle-id com.apple.finder --layout float

# Tile Safari's first newly admitted window on workspace 2 when Safari has no tracked windows
omniwmctl rule add --bundle-id com.apple.Safari --layout tile --assign-to-workspace 2

# Start new Kitty containers at 50% of the primary axis in Niri
omniwmctl rule add --bundle-id net.kovidgoyal.kitty --initial-container-primary-span 0.5

# Float windows with "Preferences" in the title
omniwmctl rule add --bundle-id com.apple.Safari --title-substring Preferences --layout float

# Float an app that has no runtime bundle ID, matched by app name
omniwmctl rule add --app-name-substring VMD --layout float

# Remove a rule
omniwmctl rule remove 550e8400-e29b-41d4-a716-446655440000

# Explicitly reapply rules to all windows of a specific app
omniwmctl rule apply --pid 12345