fix(native-chat): derive Claude slash-command recognition from the sent prompt

Claude encodes a user turn as attachment blocks followed by the typed text and
recovers the prompt by reading only the trailing text block, so a body ending in
an image has no recoverable prompt and its `/command` reaches the model as prose.
The composer builds text-then-images, so that was every send with an attachment.

Emit one trailing text block rather than appending each block: a partitioned
`[...images, ...texts]` still strands a command ahead of trailing prose, because
only the last block is read. Derive `acceptsResult` from that same sent content
so the mapper and the dispatch waiter cannot disagree about whether a command
ran; the previous `blocks.some(trimStart)` was strictly more permissive than
Claude, which does not trim before matching `/`.

src/main/claude/claude-structured-dispatch-content.test.ts

@@ -1,6 +1,17 @@
+import { mkdtemp, rm, writeFile } from 'node:fs/promises'
+import { tmpdir } from 'node:os'
+import { join } from 'node:path'
 import { describe, expect, it } from 'vitest'
 import type { AgentJournalMessageItem } from '../../shared/agent-session-journal-types'
-import { claudeDispatchMessageContent } from './claude-structured-dispatch-content'
+import {
+  claudeDispatchInvokesSlashCommand,
+  claudeDispatchMessageContent
+} from './claude-structured-dispatch-content'
+
+const PNG = Buffer.from(
+  'iVBORw0KGgoAAAANSUhEUgAAAAEAAAABCAYAAAAfFcSJAAAADUlEQVR42mP8z8BQDwAEhQGAhKmMIQAAAABJRU5ErkJggg==',
+  'base64'
+)
 
 function userMessage(blocks: AgentJournalMessageItem['blocks']): AgentJournalMessageItem {
   return { kind: 'message', role: 'user', blocks }
@@ -72,4 +83,70 @@ describe('claudeDispatchMessageContent', () => {
       })
     ).rejects.toThrow('Claude dispatch accepts only user messages')
   })
+
+  it('joins several text blocks so a command is not stranded ahead of trailing prose', async () => {
+    // Appending each block would leave `thanks` trailing, and Claude reads only that block.
+    const content = await claudeDispatchMessageContent(
+      userMessage([
+        { type: 'text', text: '/goal ship' },
+        REMOTE_IMAGE,
+        { type: 'text', text: 'thanks' }
+      ])
+    )
+
+    expect(content).toEqual([
+      { type: 'image', source: { type: 'url', url: 'https://example.test/a.png' } },
+      { type: 'text', text: '/goal ship\nthanks' }
+    ])
+    expect(claudeDispatchInvokesSlashCommand(content)).toBe(true)
+  })
+
+  it('puts a locally attached image ahead of the text, the shape the composer sends', async () => {
+    const dir = await mkdtemp(join(tmpdir(), 'claude-dispatch-content-'))
+    const path = join(dir, 'shot.png')
+    await writeFile(path, PNG)
+
+    try {
+      const content = await claudeDispatchMessageContent(
+        userMessage([
+          { type: 'text', text: '/goal ship' },
+          { type: 'image-ref', path }
+        ])
+      )
+
+      expect(content).toEqual([
+        {
+          type: 'image',
+          source: { type: 'base64', media_type: 'image/png', data: PNG.toString('base64') }
+        },
+        { type: 'text', text: '/goal ship' }
+      ])
+    } finally {
+      await rm(dir, { recursive: true, force: true })
+    }
+  })
+})
+
+describe('claudeDispatchInvokesSlashCommand', () => {
+  it('reads the trailing prompt Claude recovers, not any text block', () => {
+    expect(
+      claudeDispatchInvokesSlashCommand([
+        { type: 'image', source: { type: 'url', url: 'https://example.test/a.png' } },
+        { type: 'text', text: '/goal ship' }
+      ])
+    ).toBe(true)
+    // The pre-fix order: Claude recovers no prompt at all, so no command runs.
+    expect(
+      claudeDispatchInvokesSlashCommand([
+        { type: 'text', text: '/goal ship' },
+        { type: 'image', source: { type: 'url', url: 'https://example.test/a.png' } }
+      ])
+    ).toBe(false)
+  })
+
+  it('matches untrimmed, as Claude does, and ignores a promptless turn', () => {
+    expect(claudeDispatchInvokesSlashCommand([{ type: 'text', text: '  /goal ship' }])).toBe(false)
+    expect(claudeDispatchInvokesSlashCommand([{ type: 'text', text: 'ship it' }])).toBe(false)
+    expect(claudeDispatchInvokesSlashCommand([])).toBe(false)
+  })
 })

src/main/claude/claude-structured-dispatch-content.ts

@@ -3,6 +3,7 @@ import { open } from 'node:fs/promises'
 import { extname } from 'node:path'
 import type { AgentJournalMessageItem } from '../../shared/agent-session-journal-types'
 import type { NativeChatBlock } from '../../shared/native-chat-types'
+import { claudeRecord } from './claude-structured-item-translation'
 
 const MAX_IMAGE_BYTES = 5 * 1024 * 1024
 const MAX_IMAGE_COUNT = 20
@@ -88,31 +89,49 @@ async function imageContent(
   }
 }
 
+/**
+ * Claude encodes a user turn as attachment blocks followed by the typed text, and recovers the
+ * typed prompt by reading only the trailing text block. Verified against the real CLI over
+ * stream-json: a body ending in an image has no recoverable prompt, so its `/command` reaches
+ * the model as prose instead of being expanded.
+ */
 export async function claudeDispatchMessageContent(
   body: AgentJournalMessageItem
 ): Promise<unknown[]> {
   if (body.role !== 'user') {
     throw new Error('Claude dispatch accepts only user messages')
   }
-  // Claude reads a streamed user message as a slash-command invocation only when the LAST
-  // content block is text, so images must precede the prompt or `/command` arrives as prose.
   const images: unknown[] = []
-  const texts: unknown[] = []
+  const texts: string[] = []
   const imageBudget: ImageBudget = { count: 0, localBytes: 0 }
   for (const block of body.blocks as NativeChatBlock[]) {
     if (block.type === 'text' && block.text.length > 0) {
-      texts.push({ type: 'text', text: block.text })
+      texts.push(block.text)
     } else if (block.type === 'image-ref') {
       images.push(await imageContent(block, imageBudget))
     }
   }
-  const content = [...images, ...texts]
+  // Join rather than append each block: only the trailing text is read as the prompt, so several
+  // text blocks would silently discard every one but the last.
+  const content = texts.length > 0 ? [...images, { type: 'text', text: texts.join('\n') }] : images
   if (content.length === 0) {
     throw new Error('Claude dispatch requires text or an image')
   }
   return content
 }
 
+/** The prompt Claude recovers from a dispatch, or null when the turn carries no prompt. */
+function claudeDispatchPrompt(content: readonly unknown[]): string | null {
+  const last = claudeRecord(content.at(-1))
+  return last?.type === 'text' && typeof last.text === 'string' ? last.text : null
+}
+
+/** Mirrors how Claude decides a turn is a command. Untrimmed on purpose: Claude does not trim
+ *  here either, so leading whitespace really does mean no command runs. */
+export function claudeDispatchInvokesSlashCommand(content: readonly unknown[]): boolean {
+  return claudeDispatchPrompt(content)?.startsWith('/') === true
+}
+
 /**
  * Keep waiter metadata bounded even when a dispatch contains large base64 images.
  * The digest is only diagnostic: replay acknowledgement must use provider identity.

src/main/claude/claude-structured-dispatch.test.ts

@@ -423,6 +423,61 @@ describe('Claude structured dispatch image limits', () => {
     })
   })
 
+  it('accepts a slash command sent with an attachment from its result receipt', async () => {
+    const session = sessionFor()
+    const dispatched = dispatchClaudeTurn(
+      session,
+      {
+        clientMessageId: 'client-1',
+        body: userMessage([
+          { type: 'text', text: '/permissions' },
+          { type: 'image-ref', url: 'https://example.test/a.png' }
+        ])
+      },
+      100
+    )
+    await vi.waitFor(() => expect(session.dispatchWaiters).toHaveLength(1))
+    // The mapper moves the image ahead of the prompt, so Claude runs the command and replies
+    // with a result receipt instead of a user replay.
+    expect(
+      resolveClaudeReplayWaiter(session, {
+        type: 'result',
+        subtype: 'success',
+        session_id: 'provider-session',
+        uuid: 'command-result-uuid'
+      })
+    ).toBe(false)
+
+    await expect(dispatched).resolves.toMatchObject({
+      state: 'accepted',
+      providerIdentity: { uuid: 'command-result-uuid' }
+    })
+  })
+
+  it('does not take a result receipt for leading whitespace Claude never reads as a command', async () => {
+    const session = sessionFor()
+    const dispatched = dispatchClaudeTurn(
+      session,
+      {
+        clientMessageId: 'client-1',
+        body: userMessage([{ type: 'text', text: '  /permissions' }])
+      },
+      100
+    )
+    await vi.waitFor(() => expect(session.dispatchWaiters).toHaveLength(1))
+
+    expect(
+      resolveClaudeReplayWaiter(session, {
+        type: 'result',
+        subtype: 'success',
+        session_id: 'provider-session',
+        uuid: 'unrelated-result-uuid'
+      })
+    ).toBe(false)
+
+    await expect(dispatched).resolves.toMatchObject({ state: 'unknown' })
+  })
+
   it('correlates a later slash-command result by user_message_uuid despite a timed-out slash waiter', async () => {
     const session = sessionFor()
     const first = dispatchClaudeTurn(

src/main/claude/claude-structured-dispatch.ts

@@ -12,6 +12,7 @@ import type { ClaudeDispatchWaiter, ClaudeSession } from './claude-structured-se
 import { readClaudeFrameString } from './claude-structured-init-proof'
 import {
   claudeDispatchContentKey,
+  claudeDispatchInvokesSlashCommand,
   claudeDispatchMessageContent
 } from './claude-structured-dispatch-content'
 
@@ -231,9 +232,9 @@ export async function dispatchClaudeTurn(
     return { state: 'rejected', reason: (error as Error).message }
   }
   const dispatchSequence = ++session.dispatchSequence
-  const acceptsResult = input.body.blocks.some(
-    (block) => block.type === 'text' && block.text.trimStart().startsWith('/')
-  )
+  // Read the sent content, not the journal blocks: only the mapped trailing prompt decides
+  // whether Claude runs a command, so the two cannot disagree about which frame settles this.
+  const acceptsResult = claudeDispatchInvokesSlashCommand(content)
   const sentUuid = randomUUID()
   const replay = waitForReplay(
     session,