fix(opencode): pass run prompts as positional messages

Preserve run flags and use the existing shell quoting and run-command detector
to append the initial message after --, reusing an existing separator.
TUI launches retain their version-selected prompt transport and draft behavior.

Original run-order work: @coelho-doti (#13065, tracked in #17551).

src/shared/flag-prompt-startup.ts

@@ -0,0 +1,50 @@
+import type { AgentStartupPlan } from './tui-agent-startup'
+import type { SleepingAgentLaunchConfig } from './agent-session-resume'
+import type { SessionOptionValue } from './native-chat-session-options'
+import type { TuiAgent } from './tui-agent'
+import { TUI_AGENT_CONFIG } from './tui-agent-config'
+import { tokenizeStartupCommand, type AgentStartupShell } from './tui-agent-startup-shell'
+import { isOpenCodeRunCommand } from './opencode-headless-command'
+import { openCodeStartupPromptEnv } from './opencode-startup-prompt'
+
+export function appliedSessionOptionProps(values: Record<string, SessionOptionValue>) {
+  return Object.keys(values).length > 0 ? { sessionOptions: { ...values } } : {}
+}
+
+export function buildFlagPromptStartupPlan(args: {
+  agent: TuiAgent
+  launchCommand: string
+  quotedPrompt: string
+  prompt: string
+  shell: AgentStartupShell
+  launchConfig: SleepingAgentLaunchConfig
+  sessionOptions: Record<string, SessionOptionValue>
+  agentEnv: Record<string, string> | null | undefined
+}): AgentStartupPlan {
+  const parsed = tokenizeStartupCommand(args.launchCommand, args.shell)
+  const isOpenCodeRun =
+    (args.agent === 'opencode' || args.agent === 'opencode2') &&
+    parsed.ok &&
+    isOpenCodeRunCommand(parsed.tokens)
+  // OpenCode run takes a positional message; --prompt belongs to its TUI.
+  const promptSuffix = isOpenCodeRun
+    ? parsed.tokens.includes('--')
+      ? ` ${args.quotedPrompt}`
+      : ` -- ${args.quotedPrompt}`
+    : ` --prompt ${args.quotedPrompt}`
+  return {
+    agent: args.agent,
+    launchCommand: `${args.launchCommand}${promptSuffix}`,
+    expectedProcess: TUI_AGENT_CONFIG[args.agent].expectedProcess,
+    followupPrompt: null,
+    launchConfig: args.launchConfig,
+    ...appliedSessionOptionProps(args.sessionOptions),
+    ...openCodeStartupPromptEnv(
+      args.agent,
+      args.launchCommand,
+      args.shell,
+      args.prompt,
+      args.agentEnv
+    )
+  }
+}

src/shared/opencode-startup-prompt.test.ts

@@ -6,6 +6,7 @@ import {
   OPENCODE_STARTUP_PROMPT_BODY_ENV,
   OPENCODE_STARTUP_PROMPT_SHELL_ENV
 } from './opencode-startup-prompt'
+import { tokenizeStartupCommand } from './tui-agent-startup-shell'
 
 describe('native OpenCode startup submission intent', () => {
   it('binds the exact trimmed native prompt to host-selectable transport', () => {
@@ -33,9 +34,63 @@ describe('native OpenCode startup submission intent', () => {
       platform: 'linux'
     })
     expect(plan?.env).toBeUndefined()
-    expect(plan?.launchCommand).toContain('run --prompt')
+    expect(plan?.launchCommand).toContain("run -- 'task'")
   })
 
+  it.each(['posix', 'powershell', 'cmd'] as const)(
+    'keeps run and its flags before a positional message in %s',
+    (shell) => {
+      for (const agent of ['opencode', 'opencode2'] as const) {
+        const prompt = '--literal task with unicode é'
+        const plan = buildAgentStartupPlan({
+          agent,
+          prompt,
+          cmdOverrides: { [agent]: 'opencode --log-level debug run --standalone' },
+          platform: shell === 'posix' ? 'linux' : 'win32',
+          shell,
+          agentEnv: { CUSTOM_CONFIG: 'kept' }
+        })
+        expect(plan).not.toBeNull()
+        const parsed = tokenizeStartupCommand(plan?.launchCommand ?? '', shell)
+        expect(parsed.ok).toBe(true)
+        if (!parsed.ok) {
+          throw new Error(parsed.error)
+        }
+        expect(parsed.tokens).toEqual([
+          'opencode',
+          '--log-level',
+          'debug',
+          'run',
+          '--standalone',
+          '--',
+          prompt
+        ])
+        expect(plan?.env).toEqual({ CUSTOM_CONFIG: 'kept' })
+        expect(plan?.followupPrompt).toBeNull()
+      }
+    }
+  )
+
+  it.each(['posix', 'powershell', 'cmd'] as const)(
+    'reuses an existing run message separator in %s',
+    (shell) => {
+      const plan = buildAgentStartupPlan({
+        agent: 'opencode',
+        prompt: '--literal task',
+        cmdOverrides: { opencode: 'opencode run --standalone --' },
+        platform: shell === 'posix' ? 'linux' : 'win32',
+        shell
+      })
+      const parsed = tokenizeStartupCommand(plan?.launchCommand ?? '', shell)
+      expect(parsed.ok).toBe(true)
+      if (!parsed.ok) {
+        throw new Error(parsed.error)
+      }
+      expect(parsed.tokens).toEqual(['opencode', 'run', '--standalone', '--', '--literal task'])
+      expect(plan?.env).toBeUndefined()
+    }
+  )
+
   it('never gives an editable draft or empty launch an automatic submission intent', () => {
     const args = { agent: 'opencode' as const, cmdOverrides: {}, platform: 'linux' as const }
     expect(

src/shared/tui-agent-startup.ts

@@ -17,7 +17,7 @@ import { inlineAgentDraftFitsPlatform } from './agent-draft-platform-limit'
 import type { TuiAgent } from './tui-agent'
 import type { SessionOptionValue } from './native-chat-session-options'
 import { resolveAgentLaunchCommand } from './tui-agent-launch-command'
-import { openCodeStartupPromptEnv } from './opencode-startup-prompt'
+import { appliedSessionOptionProps, buildFlagPromptStartupPlan } from './flag-prompt-startup'
 
 export { buildAgentResumeStartupPlan } from './tui-agent-resume-startup'
 
@@ -36,10 +36,6 @@ export type AgentStartupPlan = {
   sessionOptions?: Record<string, SessionOptionValue>
 }
 
-function appliedSessionOptionProps(values: Record<string, SessionOptionValue>) {
-  return Object.keys(values).length > 0 ? { sessionOptions: { ...values } } : {}
-}
-
 export function buildAgentStartupPlan(args: {
   agent: TuiAgent
   prompt: string
@@ -117,15 +113,16 @@ export function buildAgentStartupPlan(args: {
   }
 
   if (config.promptInjectionMode === 'flag-prompt') {
-    return {
+    return buildFlagPromptStartupPlan({
       agent,
-      launchCommand: `${launchCommand} --prompt ${quotedPrompt}`,
-      expectedProcess: config.expectedProcess,
-      followupPrompt: null,
+      launchCommand,
+      quotedPrompt,
+      prompt: trimmedPrompt,
+      shell,
       launchConfig,
-      ...appliedSessionOptionProps(baseCommand.appliedSessionOptions),
-      ...openCodeStartupPromptEnv(agent, launchCommand, shell, trimmedPrompt, args.agentEnv)
-    }
+      sessionOptions: baseCommand.appliedSessionOptions,
+      agentEnv: args.agentEnv
+    })
   }
 
   if (config.promptInjectionMode === 'hermes-query') {