fix(tmux): prefer split-or-defer with FIFO deferred attach

src/shared/tmux/tmux-utils/layout.ts

@@ -2,14 +2,52 @@ import { spawn } from "bun"
 import type { TmuxLayout } from "../../../config/schema"
 import { getTmuxPath } from "../../../tools/interactive-bash/tmux-path-resolver"
 
+type TmuxSpawnCommand = (
+	args: string[],
+	options: { stdout: "ignore"; stderr: "ignore" },
+) => { exited: Promise<number> }
+
+interface LayoutDeps {
+	spawnCommand?: TmuxSpawnCommand
+}
+
+interface MainPaneWidthOptions {
+	mainPaneSize?: number
+	mainPaneMinWidth?: number
+	agentPaneMinWidth?: number
+}
+
+function clamp(value: number, min: number, max: number): number {
+	return Math.max(min, Math.min(max, value))
+}
+
+function calculateMainPaneWidth(
+	windowWidth: number,
+	options?: MainPaneWidthOptions,
+): number {
+	const dividerWidth = 1
+	const sizePercent = clamp(options?.mainPaneSize ?? 50, 20, 80)
+	const minMainPaneWidth = options?.mainPaneMinWidth ?? 0
+	const minAgentPaneWidth = options?.agentPaneMinWidth ?? 0
+	const desiredMainPaneWidth = Math.floor(
+		(windowWidth - dividerWidth) * (sizePercent / 100),
+	)
+	const maxMainPaneWidth = Math.max(
+		0,
+		windowWidth - dividerWidth - minAgentPaneWidth,
+	)
+
+	return clamp(Math.max(desiredMainPaneWidth, minMainPaneWidth), 0, maxMainPaneWidth)
+}
+
 export async function applyLayout(
+	tmux: string,
 	layout: TmuxLayout,
 	mainPaneSize: number,
+	deps?: LayoutDeps,
 ): Promise<void> {
-	const tmux = await getTmuxPath()
-	if (!tmux) return
-
-	const layoutProc = spawn([tmux, "select-layout", layout], {
+	const spawnCommand: TmuxSpawnCommand = deps?.spawnCommand ?? spawn
+	const layoutProc = spawnCommand([tmux, "select-layout", layout], {
 		stdout: "ignore",
 		stderr: "ignore",
 	})
@@ -18,7 +56,7 @@ export async function applyLayout(
 	if (layout.startsWith("main-")) {
 		const dimension =
 			layout === "main-horizontal" ? "main-pane-height" : "main-pane-width"
-		const sizeProc = spawn(
+		const sizeProc = spawnCommand(
 			[tmux, "set-window-option", dimension, `${mainPaneSize}%`],
 			{ stdout: "ignore", stderr: "ignore" },
 		)
@@ -29,15 +67,17 @@ export async function applyLayout(
 export async function enforceMainPaneWidth(
 	mainPaneId: string,
 	windowWidth: number,
-	mainPaneSize: number,
+	mainPaneSizeOrOptions?: number | MainPaneWidthOptions,
 ): Promise<void> {
 	const { log } = await import("../../logger")
 	const tmux = await getTmuxPath()
 	if (!tmux) return
 
-	const dividerWidth = 1
-	const boundedMainPaneSize = Math.max(20, Math.min(80, mainPaneSize))
-	const mainWidth = Math.floor(((windowWidth - dividerWidth) * boundedMainPaneSize) / 100)
+	const options: MainPaneWidthOptions =
+		typeof mainPaneSizeOrOptions === "number"
+			? { mainPaneSize: mainPaneSizeOrOptions }
+			: mainPaneSizeOrOptions ?? {}
+	const mainWidth = calculateMainPaneWidth(windowWidth, options)
 
 	const proc = spawn([tmux, "resize-pane", "-t", mainPaneId, "-x", String(mainWidth)], {
 		stdout: "ignore",
@@ -49,6 +89,8 @@ export async function enforceMainPaneWidth(
 		mainPaneId,
 		mainWidth,
 		windowWidth,
-		mainPaneSize: boundedMainPaneSize,
+		mainPaneSize: options?.mainPaneSize,
+		mainPaneMinWidth: options?.mainPaneMinWidth,
+		agentPaneMinWidth: options?.agentPaneMinWidth,
 	})
 }