[BUG] Code mode broken after v2.1.78 update — .app bundle binary not spawnable by desktop SDK

Preflight Checklist

• [x] I have searched existing issues and this hasn't been reported yet
• [x] This is a single bug report (please file separate reports for different bugs)
• [x] I am using the latest version of Claude Code

What's Wrong?

Code mode in Claude Desktop stopped working after Claude Code auto-updated from v2.1.76 to v2.1.78 on March 19, 2026. Every code mode session immediately fails with exit code 1 and zero output. Chat and Cowork modes continue to work fine. Claude Code CLI works perfectly from the terminal.

Root cause: binary distribution format changed between versions.

| Version | Binary path | Format | Status |
|---------|------------|--------|--------|
| v2.1.76 | .../claude-code/2.1.76/claude | Standalone binary | Working |
| v2.1.78 | .../claude-code/2.1.78/claude.app/Contents/MacOS/claude | macOS app bundle | Broken |

The desktop app correctly locates the new binary inside the .app bundle, but the process exits with code 1 instantly (0-5 seconds) with zero output. The binary itself is functional — --version and --help both succeed from the terminal.

This points to an incompatibility in how the desktop app's SDK spawns the new app-bundle-wrapped binary (e.g., entitlements, sandbox context, or exec path handling).

Timeline from logs:

• 2026-03-19 00:14:56 — Last successful code mode session using v2.1.76 standalone binary
• 2026-03-19 13:17:59 — App starts, initializes v2.1.78, downloads claude.app.tar.zst bundle
• 2026-03-19 13:18:00 — Falls back to v2.1.76 while download completes
• 2026-03-19 13:18:02 — v2.1.78 bundle installed at .../claude-code/2.1.78/
• 2026-03-19 13:27:13 — First code mode attempt with v2.1.78: exit code 1, 5s, no_response
• 2026-03-19 13:27:18 — Retry: exit code 1, immediate
• 2026-03-19 13:27:31 — Another attempt: exit code 1, 0s, no_response
• Every subsequent attempt on March 19 and March 20: same failure

Key log lines:

[info] Using Claude Code binary at: /Users/.../claude-code/2.1.78/claude.app/Contents/MacOS/claude
[error] Session local_XXX query error: Claude Code process exited with code 1
[info] [CCD CycleHealth] unhealthy cycle (0s, hadFirstResponse=false, reason=no_response)

What still works:

• Chat mode (uses claude.ai web)
• Cowork mode (runs Claude Code in the Linux VM)
• Claude Code CLI from terminal (v2.1.80)

What was tried:

• Multiple app restarts
• Force re-downloading the v2.1.78 bundle (app re-downloaded claude.app.tar.zst, same result)
• Deleting cached bundle at ~/Library/Application Support/Claude/claude-code/2.1.78/

What Should Happen?

Code mode sessions should start and respond to messages, as they did with v2.1.76.

claude-code-mode-bug-logs.zip

Error Messages/Logs

See attached `claude-code-mode-bug-logs.zip` containing:
- `main1.log` — Last working v2.1.76 session through the v2.1.78 transition and first failures (March 19)
- `main.log` — Continued v2.1.78 failures (March 20)
- `system-info.txt` — Full system/app details

Steps to Reproduce

1. Have Claude Code v2.1.76 working in code mode
2. Allow auto-update to v2.1.78
3. Open code mode, send a message
4. Session fails immediately — no loading indicator, no response

Claude Model

Opus

Is this a regression?

Yes, this worked in a previous version

Last Working Version

v2.1.76 (standalone binary format)

Claude Code Version

2.1.78 (desktop-managed), 2.1.80 (CLI)

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

Terminal.app (macOS)

Additional Information

• Claude Desktop app version: 1.1.7714
• Electron: 40.4.1
• The download URL confirms the format change: https://downloads.claude.ai/claude-code-releases/2.1.78/darwin-arm64/claude.app.tar.zst (note .app.tar.zst vs plain binary in prior versions)
• Possibly related to #36362, #30717, but those have different root causes (SSH plugin failure, wrong platform binary). This is specifically about the .app bundle format change breaking the SDK spawn path.

claude-code-mode-bug-logs.zip