diff --git a/src/features/tmux-subagent/decision-engine.test.ts b/src/features/tmux-subagent/decision-engine.test.ts
index b514d555..c0fa2ccc 100644
--- a/src/features/tmux-subagent/decision-engine.test.ts
+++ b/src/features/tmux-subagent/decision-engine.test.ts
@@ -351,4 +351,47 @@ describe("calculateCapacity", () => {
     expect(capacity.rows).toBe(4)
     expect(capacity.total).toBe(12)
   })
+
+  it("#given a smaller minPaneWidth #when calculating capacity #then fits more columns", () => {
+    //#given
+    const smallMinWidth = 30
+
+    //#when
+    const defaultCapacity = calculateCapacity(212, 44)
+    const customCapacity = calculateCapacity(212, 44, smallMinWidth)
+
+    //#then
+    expect(customCapacity.cols).toBeGreaterThanOrEqual(defaultCapacity.cols)
+  })
+})
+
+describe("decideSpawnActions with custom agentPaneWidth", () => {
+  const createWindowState = (
+    windowWidth: number,
+    windowHeight: number,
+    agentPanes: Array<{ paneId: string; width: number; height: number; left: number; top: number }> = []
+  ): WindowState => ({
+    windowWidth,
+    windowHeight,
+    mainPane: { paneId: "%0", width: Math.floor(windowWidth / 2), height: windowHeight, left: 0, top: 0, title: "main", isActive: true },
+    agentPanes: agentPanes.map((p, i) => ({
+      ...p,
+      title: `agent-${i}`,
+      isActive: false,
+    })),
+  })
+
+  it("#given a smaller agentPaneWidth #when window would be too small for default #then spawns with custom config", () => {
+    //#given
+    const smallConfig: CapacityConfig = { mainPaneMinWidth: 120, agentPaneWidth: 25 }
+    const state = createWindowState(100, 30)
+
+    //#when
+    const defaultResult = decideSpawnActions(state, "ses1", "test", { mainPaneMinWidth: 120, agentPaneWidth: 52 }, [])
+    const customResult = decideSpawnActions(state, "ses1", "test", smallConfig, [])
+
+    //#then
+    expect(defaultResult.canSpawn).toBe(false)
+    expect(customResult.canSpawn).toBe(true)
+  })
 })
diff --git a/src/features/tmux-subagent/grid-planning.ts b/src/features/tmux-subagent/grid-planning.ts
index 9e0fcb91..037b14bc 100644
--- a/src/features/tmux-subagent/grid-planning.ts
+++ b/src/features/tmux-subagent/grid-planning.ts
@@ -1,10 +1,10 @@
+import { MIN_PANE_HEIGHT, MIN_PANE_WIDTH } from "./types"
 import type { TmuxPaneInfo } from "./types"
 import {
 	DIVIDER_SIZE,
 	MAIN_PANE_RATIO,
 	MAX_GRID_SIZE,
 } from "./tmux-grid-constants"
-import { MIN_PANE_HEIGHT, MIN_PANE_WIDTH } from "./types"
 
 export interface GridCapacity {
 	cols: number
@@ -27,6 +27,7 @@ export interface GridPlan {
 export function calculateCapacity(
 	windowWidth: number,
 	windowHeight: number,
+	minPaneWidth: number = MIN_PANE_WIDTH,
 ): GridCapacity {
 	const availableWidth = Math.floor(windowWidth * (1 - MAIN_PANE_RATIO))
 	const cols = Math.min(
@@ -34,7 +35,7 @@ export function calculateCapacity(
 		Math.max(
 			0,
 			Math.floor(
-				(availableWidth + DIVIDER_SIZE) / (MIN_PANE_WIDTH + DIVIDER_SIZE),
+				(availableWidth + DIVIDER_SIZE) / (minPaneWidth + DIVIDER_SIZE),
 			),
 		),
 	)
diff --git a/src/features/tmux-subagent/pane-split-availability.ts b/src/features/tmux-subagent/pane-split-availability.ts
index fd9d34ec..65f85247 100644
--- a/src/features/tmux-subagent/pane-split-availability.ts
+++ b/src/features/tmux-subagent/pane-split-availability.ts
@@ -1,3 +1,4 @@
+import { MIN_PANE_HEIGHT, MIN_PANE_WIDTH } from "./types"
 import type { SplitDirection, TmuxPaneInfo } from "./types"
 import {
 	DIVIDER_SIZE,
@@ -7,6 +8,10 @@ import {
 	MIN_SPLIT_WIDTH,
 } from "./tmux-grid-constants"
 
+function minSplitWidthFor(minPaneWidth: number): number {
+	return 2 * minPaneWidth + DIVIDER_SIZE
+}
+
 export function getColumnCount(paneCount: number): number {
 	if (paneCount <= 0) return 1
 	return Math.min(MAX_COLS, Math.max(1, Math.ceil(paneCount / MAX_ROWS)))
@@ -21,26 +26,32 @@ export function getColumnWidth(agentAreaWidth: number, paneCount: number): numbe
 export function isSplittableAtCount(
 	agentAreaWidth: number,
 	paneCount: number,
+	minPaneWidth: number = MIN_PANE_WIDTH,
 ): boolean {
 	const columnWidth = getColumnWidth(agentAreaWidth, paneCount)
-	return columnWidth >= MIN_SPLIT_WIDTH
+	return columnWidth >= minSplitWidthFor(minPaneWidth)
 }
 
 export function findMinimalEvictions(
 	agentAreaWidth: number,
 	currentCount: number,
+	minPaneWidth: number = MIN_PANE_WIDTH,
 ): number | null {
 	for (let k = 1; k <= currentCount; k++) {
-		if (isSplittableAtCount(agentAreaWidth, currentCount - k)) {
+		if (isSplittableAtCount(agentAreaWidth, currentCount - k, minPaneWidth)) {
 			return k
 		}
 	}
 	return null
 }
 
-export function canSplitPane(pane: TmuxPaneInfo, direction: SplitDirection): boolean {
+export function canSplitPane(
+	pane: TmuxPaneInfo,
+	direction: SplitDirection,
+	minPaneWidth: number = MIN_PANE_WIDTH,
+): boolean {
 	if (direction === "-h") {
-		return pane.width >= MIN_SPLIT_WIDTH
+		return pane.width >= minSplitWidthFor(minPaneWidth)
 	}
 	return pane.height >= MIN_SPLIT_HEIGHT
 }
diff --git a/src/features/tmux-subagent/spawn-action-decider.ts b/src/features/tmux-subagent/spawn-action-decider.ts
index 1a279b65..9a2f71ff 100644
--- a/src/features/tmux-subagent/spawn-action-decider.ts
+++ b/src/features/tmux-subagent/spawn-action-decider.ts
@@ -13,23 +13,23 @@ import {
 } from "./pane-split-availability"
 import { findSpawnTarget } from "./spawn-target-finder"
 import { findOldestAgentPane, type SessionMapping } from "./oldest-agent-pane"
-import { MIN_PANE_WIDTH } from "./types"
 
 export function decideSpawnActions(
 	state: WindowState,
 	sessionId: string,
 	description: string,
-	_config: CapacityConfig,
+	config: CapacityConfig,
 	sessionMappings: SessionMapping[],
 ): SpawnDecision {
 	if (!state.mainPane) {
 		return { canSpawn: false, actions: [], reason: "no main pane found" }
 	}
 
+	const minPaneWidth = config.agentPaneWidth
 	const agentAreaWidth = Math.floor(state.windowWidth * (1 - MAIN_PANE_RATIO))
 	const currentCount = state.agentPanes.length
 
-	if (agentAreaWidth < MIN_PANE_WIDTH) {
+	if (agentAreaWidth < minPaneWidth) {
 		return {
 			canSpawn: false,
 			actions: [],
@@ -44,7 +44,7 @@ export function decideSpawnActions(
 
 	if (currentCount === 0) {
 		const virtualMainPane: TmuxPaneInfo = { ...state.mainPane, width: state.windowWidth }
-		if (canSplitPane(virtualMainPane, "-h")) {
+		if (canSplitPane(virtualMainPane, "-h", minPaneWidth)) {
 			return {
 				canSpawn: true,
 				actions: [
@@ -61,7 +61,7 @@ export function decideSpawnActions(
 		return { canSpawn: false, actions: [], reason: "mainPane too small to split" }
 	}
 
-	if (isSplittableAtCount(agentAreaWidth, currentCount)) {
+	if (isSplittableAtCount(agentAreaWidth, currentCount, minPaneWidth)) {
 		const spawnTarget = findSpawnTarget(state)
 		if (spawnTarget) {
 			return {
@@ -79,7 +79,7 @@ export function decideSpawnActions(
 		}
 	}
 
-	const minEvictions = findMinimalEvictions(agentAreaWidth, currentCount)
+	const minEvictions = findMinimalEvictions(agentAreaWidth, currentCount, minPaneWidth)
 	if (minEvictions === 1 && oldestPane) {
 		return {
 			canSpawn: true,