fix(runtime): only override a paired host's agent args when the client chose one

Forwarding the client's fully-resolved args made an unconfigured client push
the built-in YOLO default onto a host whose own Agent Permissions say Manual.
Send the override only when the caller passed args or the user actually
configured a mode for this agent; otherwise stay silent and keep the host's
choice. Manual's empty string still rides the wire, which is the #15373 fix.

src/renderer/src/lib/launch-agent-in-new-tab-web-runtime.test.ts

@@ -93,10 +93,11 @@ describe('launchAgentInNewTab paired web runtime', () => {
       activate: true,
       agentSessionKind: 'fresh',
       agent: 'claude',
-      // Why: the client resolves its default explicitly so the host cannot apply its own.
-      agentArgs: '--dangerously-skip-permissions',
       viewMode: 'terminal'
     })
+    // Why (#15373): an unconfigured client must not push the built-in YOLO default onto a host
+    // whose own Agent Permissions say Manual; omission keeps the host's choice.
+    expect(mocks.createWebRuntimeSessionTerminal.mock.calls[0]?.[0]).not.toHaveProperty('agentArgs')
     expect(mocks.createTab).not.toHaveBeenCalled()
     await Promise.resolve()
     expect(mocks.setActiveTabType).toHaveBeenCalledWith('terminal')
@@ -159,4 +160,22 @@ describe('launchAgentInNewTab paired web runtime', () => {
       })
     )
   })
+
+  it('forwards caller-supplied agent args even when the client has no configured default', async () => {
+    const { launchAgentInNewTab } = await import('./launch-agent-in-new-tab')
+
+    launchAgentInNewTab({
+      agent: 'claude',
+      worktreeId: 'wt-1',
+      groupId: 'group-1',
+      agentArgs: '--permission-mode plan'
+    })
+
+    expect(mocks.createWebRuntimeSessionTerminal).toHaveBeenCalledWith(
+      expect.objectContaining({
+        agent: 'claude',
+        agentArgs: '--permission-mode plan'
+      })
+    )
+  })
 })

src/renderer/src/lib/launch-agent-in-new-tab.ts

@@ -17,6 +17,7 @@ import { getLocalProjectExecutionRuntimeContext } from '@/lib/local-preflight-co
 import { isWebRuntimeSessionActive } from '@/runtime/web-runtime-session'
 import { launchAgentInWebHostTab } from '@/lib/launch-agent-web-host-tab'
 import {
+  hasConfiguredTuiAgentLaunchArgs,
   resolveTuiAgentLaunchArgs,
   resolveTuiAgentLaunchEnv
 } from '../../../shared/tui-agent-launch-defaults'
@@ -106,6 +107,14 @@ export function launchAgentInNewTab(args: LaunchAgentInNewTabArgs): LaunchAgentI
     agentArgs !== undefined
       ? agentArgs
       : resolveTuiAgentLaunchArgs(agent, store.settings?.agentDefaultArgs)
+  // Why (#15373): a paired host re-resolves omitted args against its own settings, so a client that
+  // actually chose a permission mode must send it — including Manual's empty string. An unconfigured
+  // client has chosen nothing, so stay silent rather than forcing the built-in YOLO default on the host.
+  const pairedHostAgentArgs =
+    agentArgs !== undefined ||
+    hasConfiguredTuiAgentLaunchArgs(agent, store.settings?.agentDefaultArgs)
+      ? effectiveAgentArgs
+      : undefined
   const agentEnv = resolveTuiAgentLaunchEnv(agent, store.settings?.agentDefaultEnv)
   const trimmedPrompt = prompt?.trim() ?? ''
   const hasPrompt = trimmedPrompt.length > 0
@@ -157,9 +166,7 @@ export function launchAgentInNewTab(args: LaunchAgentInNewTabArgs): LaunchAgentI
       promptDelivery,
       pastePromptAfterReady: pasteDraftAfterLaunch,
       submitPastedPrompt,
-      // Why: the raw param is undefined on ordinary UI launches, so omission let a headless host apply its
-      // own YOLO default (#15373). Send the resolved value — present-but-empty is an explicit no-args override.
-      agentArgs: effectiveAgentArgs,
+      agentArgs: pairedHostAgentArgs,
       // Why: omission means terminal locally, but would let a paired host apply
       // its own default; send the client's resolved terminal choice explicitly.
       viewMode: initialViewModeProps.viewMode ?? 'terminal',

src/shared/tui-agent-launch-defaults.ts

@@ -79,16 +79,24 @@ export function getTuiAgentDefaultEnv(agent: TuiAgent): Record<string, string> {
   return { ...DEFAULT_TUI_AGENT_ENV[agent] }
 }
 
+/** Manual is stored as `''`, so the key's presence — not its truthiness — is the user's explicit choice. */
+export function hasConfiguredTuiAgentLaunchArgs(
+  agent: TuiAgent,
+  configuredArgs: Partial<Record<TuiAgent, string>> | null | undefined
+): boolean {
+  return Boolean(
+    configuredArgs &&
+    Object.hasOwn(configuredArgs, agent) &&
+    typeof configuredArgs[agent] === 'string'
+  )
+}
+
 export function resolveTuiAgentLaunchArgs(
   agent: TuiAgent,
   configuredArgs: Partial<Record<TuiAgent, string>> | null | undefined
 ): string {
-  if (
-    configuredArgs &&
-    Object.hasOwn(configuredArgs, agent) &&
-    typeof configuredArgs[agent] === 'string'
-  ) {
-    return configuredArgs[agent] ?? ''
+  if (hasConfiguredTuiAgentLaunchArgs(agent, configuredArgs)) {
+    return configuredArgs?.[agent] ?? ''
   }
   return getTuiAgentDefaultArgs(agent)
 }