diff --git a/src/cli/handlers/file.test.ts b/src/cli/handlers/file.test.ts
index 4e36ddbfff2..66f55158ff5 100644
--- a/src/cli/handlers/file.test.ts
+++ b/src/cli/handlers/file.test.ts
@@ -45,6 +45,7 @@ vi.mock('../runtime-client', () => {
 })
 
 import { main } from '../index'
+import { RuntimeRpcFailureError } from '../runtime-client'
 import { buildWorktree, okFixture, queueFixtures, worktreeListFixture } from '../test-fixtures'
 
 describe('orca file CLI handlers', () => {
@@ -87,6 +88,29 @@ describe('orca file CLI handlers', () => {
     expect(vi.mocked(console.log).mock.calls[0][0]).toBe('Opened src/App.tsx.')
   })
 
+  it('reports a missing file as a JSON failure with a nonzero exit code', async () => {
+    const priorExitCode = process.exitCode
+    queueFixtures(callMock, worktreeListFixture([buildWorktree('/tmp/repo', 'feature')]))
+    callMock.mockRejectedValueOnce(
+      new RuntimeRpcFailureError({
+        id: 'req_open',
+        ok: false,
+        error: { code: 'runtime_error', message: 'File not found: docs/missing.md' },
+        _meta: { runtimeId: 'runtime-1' }
+      })
+    )
+
+    await main(['file', 'open', 'docs/missing.md', '--json'], '/tmp/repo')
+
+    expect(JSON.parse(String(vi.mocked(console.log).mock.calls[0][0]))).toMatchObject({
+      ok: false,
+      error: { code: 'runtime_error', message: 'File not found: docs/missing.md' }
+    })
+    expect(process.exitCode).toBe(1)
+
+    process.exitCode = priorExitCode
+  })
+
   it('opens a staged diff for an explicit worktree without cwd inference', async () => {
     queueFixtures(
       callMock,
diff --git a/src/main/runtime/orca-runtime-files.test.ts b/src/main/runtime/orca-runtime-files.test.ts
index d43e48c4695..4a52e01233f 100644
--- a/src/main/runtime/orca-runtime-files.test.ts
+++ b/src/main/runtime/orca-runtime-files.test.ts
@@ -248,6 +248,8 @@ describe('RuntimeFileCommands', () => {
   it('opens text files through the renderer host (inheriting active runtime env)', async () => {
     const openFile = vi.fn()
     const { commands } = createRuntimeFileCommands({ openFile })
+    resolveAuthorizedPathMock.mockImplementation(async (path: string) => path)
+    statMock.mockResolvedValue(mockStats(12, 3))
 
     const result = await commands.openMobileFile('id:wt-1', 'docs/readme.md')
 
@@ -268,6 +270,8 @@ describe('RuntimeFileCommands', () => {
   it('opens previewable images through the renderer host as an image tab', async () => {
     const openFile = vi.fn()
     const { commands } = createRuntimeFileCommands({ openFile })
+    resolveAuthorizedPathMock.mockImplementation(async (path: string) => path)
+    statMock.mockResolvedValue(mockStats(12, 3))
 
     const result = await commands.openMobileFile('id:wt-1', 'assets/logo.png')
 
@@ -288,6 +292,8 @@ describe('RuntimeFileCommands', () => {
   it('leaves non-previewable binaries unavailable on mobile', async () => {
     const openFile = vi.fn()
     const { commands } = createRuntimeFileCommands({ openFile })
+    resolveAuthorizedPathMock.mockImplementation(async (path: string) => path)
+    statMock.mockResolvedValue(mockStats(12, 3))
 
     const result = await commands.openMobileFile('id:wt-1', 'dist/bundle.zip')
 
@@ -300,6 +306,43 @@ describe('RuntimeFileCommands', () => {
     })
   })
 
+  it('rejects a missing local file before opening a renderer tab', async () => {
+    const openFile = vi.fn()
+    const { commands } = createRuntimeFileCommands({ openFile })
+    resolveAuthorizedPathMock.mockImplementation(async (path: string) => path)
+    statMock.mockRejectedValue(enoent())
+
+    await expect(commands.openMobileFile('id:wt-1', 'docs/missing.md')).rejects.toThrow(
+      'File not found: docs/missing.md'
+    )
+
+    expect(openFile).not.toHaveBeenCalled()
+  })
+
+  it('rejects a missing SSH file before opening a renderer tab', async () => {
+    const openFile = vi.fn()
+    const stat = vi.fn().mockRejectedValue(new Error('ENOENT: no such file'))
+    const { commands } = createRuntimeFileCommands({
+      openFile,
+      resolveRuntimeFileTarget: vi.fn(async () => ({
+        worktree: {
+          id: 'wt-1',
+          repoId: 'repo-1',
+          path: '/repo'
+        },
+        connectionId: 'ssh-1'
+      }))
+    })
+    vi.mocked(getSshFilesystemProvider).mockReturnValue({ stat } as never)
+
+    await expect(commands.openMobileFile('id:wt-1', 'docs/missing.md')).rejects.toThrow(
+      'File not found: docs/missing.md'
+    )
+
+    expect(stat).toHaveBeenCalledWith('/repo/docs/missing.md')
+    expect(openFile).not.toHaveBeenCalled()
+  })
+
   it('does not follow symlinks when reading runtime-local file explorer dirs', async () => {
     const { commands } = createRuntimeFileCommands()
     resolveAuthorizedPathMock.mockResolvedValue('/repo')
diff --git a/src/main/runtime/orca-runtime-files.ts b/src/main/runtime/orca-runtime-files.ts
index acdf3616f47..09d81dfe972 100644
--- a/src/main/runtime/orca-runtime-files.ts
+++ b/src/main/runtime/orca-runtime-files.ts
@@ -248,10 +248,12 @@ export class RuntimeFileCommands {
     worktreeSelector: string,
     relativePath: string
   ): Promise<RuntimeFileOpenResult> {
-    const { worktree } = await this.host.resolveRuntimeFileTarget(worktreeSelector)
+    const { worktree, connectionId } = await this.host.resolveRuntimeFileTarget(worktreeSelector)
     if (!isSafeMobileRelativePath(relativePath)) {
       throw new Error('invalid_relative_path')
     }
+    const filePath = joinWorktreeRelativePath(worktree.path, relativePath)
+    await this.assertMobileFileExists(filePath, relativePath, connectionId)
     // Previewable images open like text (the mobile viewer renders them via
     // files.readPreview); other binaries stay unavailable on mobile.
     const kind = isMobilePreviewableImagePath(relativePath)
@@ -264,7 +266,6 @@ export class RuntimeFileCommands {
     if (kind === 'binary') {
       return { worktree: worktree.id, relativePath, kind, opened: false }
     }
-    const filePath = joinWorktreeRelativePath(worktree.path, relativePath)
     // Why: the service's internal runtimeId is not a registered runtime env selector
     // (those live in orca-environments.json). Passing it caused Unknown environment
     // errors on content load for CLI-initiated opens (via files.open from orca cli
@@ -275,6 +276,32 @@ export class RuntimeFileCommands {
     return { worktree: worktree.id, relativePath, kind, opened: true }
   }
 
+  private async assertMobileFileExists(
+    filePath: string,
+    relativePath: string,
+    connectionId?: string
+  ): Promise<void> {
+    try {
+      if (connectionId) {
+        const provider = getSshFilesystemProvider(connectionId)
+        if (!provider) {
+          throw new Error(SSH_FILESYSTEM_PROVIDER_UNAVAILABLE_MESSAGE)
+        }
+        await provider.stat(filePath)
+        return
+      }
+      await stat(await resolveAuthorizedPath(filePath, this.host.requireStore()))
+    } catch (error) {
+      if (
+        isENOENT(error) ||
+        (connectionId && RuntimeFileCommands.isRemoteNotFoundErrorMessage(error))
+      ) {
+        throw new Error(`File not found: ${relativePath}`)
+      }
+      throw error
+    }
+  }
+
   async openMobileDiff(
     worktreeSelector: string,
     relativePath: string,