diff --git a/ui-tui/src/__tests__/createSlashHandler.test.ts b/ui-tui/src/__tests__/createSlashHandler.test.ts
index 9180651f51..b47efb3d52 100644
--- a/ui-tui/src/__tests__/createSlashHandler.test.ts
+++ b/ui-tui/src/__tests__/createSlashHandler.test.ts
@@ -1,6 +1,7 @@
 import { beforeEach, describe, expect, it, vi } from 'vitest'
 
 import { createSlashHandler } from '../app/createSlashHandler.js'
+import { TUI_SESSION_MODEL_FLAG } from '../domain/slash.js'
 import { getOverlayState, resetOverlayState } from '../app/overlayStore.js'
 import { getUiState, patchUiState, resetUiState } from '../app/uiStore.js'
 
@@ -55,7 +56,7 @@ describe('createSlashHandler', () => {
 
     expect(
       createSlashHandler(ctx)(
-        '/model anthropic/claude-sonnet-4.6 --provider openrouter --tui-session'
+        `/model anthropic/claude-sonnet-4.6 --provider openrouter ${TUI_SESSION_MODEL_FLAG}`
       )
     ).toBe(true)
     expect(ctx.gateway.rpc).toHaveBeenCalledWith('config.set', {
diff --git a/ui-tui/src/app/slash/commands/session.ts b/ui-tui/src/app/slash/commands/session.ts
index a6408ec1f1..a31a4cbe43 100644
--- a/ui-tui/src/app/slash/commands/session.ts
+++ b/ui-tui/src/app/slash/commands/session.ts
@@ -10,6 +10,7 @@ import type {
   VoiceToggleResponse
 } from '../../../gatewayTypes.js'
 import { fmtK } from '../../../lib/text.js'
+import { TUI_SESSION_MODEL_FLAG } from '../../../domain/slash.js'
 import type { PanelSection } from '../../../types.js'
 import { patchOverlayState } from '../../overlayStore.js'
 import { patchUiState } from '../../uiStore.js'
@@ -17,8 +18,8 @@ import type { SlashCommand } from '../types.js'
 
 const GLOBAL_MODEL_FLAG_RE = /(?:^|\s)--global(?:\s|$)/
 
-/** Stripped before `config.set`; TUI model picker uses this for session-scoped switches. */
-const TUI_SESSION_MODEL_RE = /(?:^|\s)--tui-session(?:\s|$)/
+const TUI_SESSION_MODEL_RE = new RegExp(`(?:^|\\s)${TUI_SESSION_MODEL_FLAG}(?:\\s|$)`)
+const TUI_SESSION_STRIP_RE = new RegExp(`\\s*${TUI_SESSION_MODEL_FLAG}\\b\\s*`, 'g')
 
 const persistedModelArg = (arg: string) => {
   const trimmed = arg.trim()
@@ -26,6 +27,9 @@ const persistedModelArg = (arg: string) => {
   return !trimmed || GLOBAL_MODEL_FLAG_RE.test(trimmed) ? trimmed : `${trimmed} --global`
 }
 
+const stripTuiSessionFlag = (trimmed: string) =>
+  trimmed.replace(TUI_SESSION_STRIP_RE, ' ').replace(/\s+/g, ' ').trim()
+
 const modelValueForConfigSet = (arg: string) => {
   const trimmed = arg.trim()
 
@@ -34,7 +38,7 @@ const modelValueForConfigSet = (arg: string) => {
   }
 
   if (TUI_SESSION_MODEL_RE.test(trimmed)) {
-    return trimmed.replace(/\s*--tui-session\b\s*/g, ' ').replace(/\s+/g, ' ').trim()
+    return stripTuiSessionFlag(trimmed)
   }
 
   return persistedModelArg(trimmed)
diff --git a/ui-tui/src/components/modelPicker.tsx b/ui-tui/src/components/modelPicker.tsx
index ec9acaa779..b5882a1352 100644
--- a/ui-tui/src/components/modelPicker.tsx
+++ b/ui-tui/src/components/modelPicker.tsx
@@ -2,6 +2,7 @@ import { Box, Text, useInput, useStdout } from '@hermes/ink'
 import { useEffect, useMemo, useState } from 'react'
 
 import { providerDisplayNames } from '../domain/providers.js'
+import { TUI_SESSION_MODEL_FLAG } from '../domain/slash.js'
 import type { GatewayClient } from '../gatewayClient.js'
 import type { ModelOptionProvider, ModelOptionsResponse } from '../gatewayTypes.js'
 import { asRpcResult, rpcErrorMessage } from '../lib/rpc.js'
@@ -112,7 +113,7 @@ export function ModelPicker({ gw, onCancel, onSelect, sessionId, t }: ModelPicke
 
       if (provider && model) {
         onSelect(
-          `${model} --provider ${provider.slug}${persistGlobal ? ' --global' : ' --tui-session'}`
+          `${model} --provider ${provider.slug}${persistGlobal ? ' --global' : ` ${TUI_SESSION_MODEL_FLAG}`}`
         )
       } else {
         setStage('provider')
@@ -140,7 +141,7 @@ export function ModelPicker({ gw, onCancel, onSelect, sessionId, t }: ModelPicke
         }
       } else if (provider && models[offset + n - 1]) {
         onSelect(
-          `${models[offset + n - 1]} --provider ${provider.slug}${persistGlobal ? ' --global' : ' --tui-session'}`
+          `${models[offset + n - 1]} --provider ${provider.slug}${persistGlobal ? ' --global' : ` ${TUI_SESSION_MODEL_FLAG}`}`
         )
       }
     }
diff --git a/ui-tui/src/domain/slash.ts b/ui-tui/src/domain/slash.ts
index 1fc8082ba5..8090f6046f 100644
--- a/ui-tui/src/domain/slash.ts
+++ b/ui-tui/src/domain/slash.ts
@@ -1,3 +1,6 @@
+/** Appended to `/model` args from the TUI picker for session scope; stripped in `session` slash before `config.set`. */
+export const TUI_SESSION_MODEL_FLAG = '--tui-session'
+
 export const looksLikeSlashCommand = (text: string) => /^\/[^\s/]*(?:\s|$)/.test(text)
 
 export const parseSlashCommand = (cmd: string) => {