[BUG] `downloads.claude.ai` returning 403 — Cowork workspace fails to start, update check broken (macOS)

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?

Claude Desktop's Cowork workspace fails to start with "Download failed with status code: 403." The update checker also fails simultaneously. Both issues trace to downloads.claude.ai returning HTTP 403 at the CDN level — confirmed via bare curl without any app auth headers involved.

This is not an app-level or auth issue — the CDN itself is rejecting requests.

Cowork was working normally the day before (March 16). The workspace VM bundle exists locally but is missing its boot image (rootfs.img.zst), which the app cannot re-download due to the 403.

What Should Happen?

downloads.claude.ai should serve the requested binaries and VM images. Cowork workspace should start normally as it did on March 16.

If there is a regional or transient CDN issue, the error messaging should not suggest "reinstall workspace" as a fix, since that both destroys user data (279MB sessiondata.img) and would fail anyway against the same 403.

status.anthropic.com shows all systems operational — this CDN issue is not covered by existing monitoring.

Error Messages/Logs

2026-03-17 06:36:14 [error] [CCD] Download attempt 2/3 failed Error: Download failed with status code: 403
2026-03-17 06:36:14 [error] [ClaudeCodeManager-VM] Download attempt 2/3 failed Error: Download failed with status code: 403
2026-03-17 06:36:16 [info]  [CCD] Downloading from https://downloads.claude.ai/claude-code-releases/2.1.74/darwin-arm64/claude.zst
2026-03-17 06:36:16 [info]  [ClaudeCodeManager-VM] Downloading from https://downloads.claude.ai/claude-code-releases/2.1.74/linux-arm64/claude.zst
2026-03-17 06:36:16 [error] [CCD] Download attempt 3/3 failed Error: Download failed with status code: 403
2026-03-17 06:36:16 [error] [CCD] All download attempts failed
2026-03-17 06:36:16 [error] [ClaudeCodeManager-VM] Download attempt 3/3 failed Error: Download failed with status code: 403
2026-03-17 06:36:16 [error] [ClaudeCodeManager-VM] All download attempts failed
2026-03-17 06:36:17 [info]  [download:8] Starting download from https://downloads.claude.ai/vms/linux/arm64/fb30784dadb34104626c8cf6d8f90dd47cd393cc/rootfs.img.zst
2026-03-17 06:42:04 [info]  Update URL: https://downloads.claude.ai/releases/darwin/universal/RELEASES.json
2026-03-17 06:42:05 [error] Auto-update error: [Error: Update check failed. The server sent an invalid response. Try again later.]

Steps to Reproduce

1. Open Claude Desktop on macOS (latest version as of 2026-03-17)
2. Switch to Cowork mode
3. Workspace fails to start: "Failed to start Claude's workspace — Download failed with status code: 403"
4. Check for updates also fails: "Update check failed. The server sent an invalid response."
5. Confirm CDN-level issue: curl -I https://downloads.claude.ai/claude-code-releases/2.1.74/darwin-arm64/claude.zst returns HTTP 403

Claude Model

Opus

Is this a regression?

Yes, this worked in a previous version

Last Working Version

Worked on March 16, 2026 — same app version, same machine

Claude Code Version

2.1.74

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

Terminal.app (macOS)

Additional Information

CDN-level confirmation via bare curl:

$ curl -I https://downloads.claude.ai/claude-code-releases/2.1.74/darwin-arm64/claude.zst
HTTP/2 403
alt-svc: h3=":443"; ma=2592000,h3-29=":443"; ma=2592000

All four affected URLs:

| URL | Purpose | Result |
|-----|---------|--------|
| downloads.claude.ai/claude-code-releases/2.1.74/darwin-arm64/claude.zst | Claude Code binary (macOS) | 403 |
| downloads.claude.ai/claude-code-releases/2.1.74/linux-arm64/claude.zst | Claude Code binary (VM) | 403 |
| downloads.claude.ai/vms/linux/arm64/.../rootfs.img.zst | VM root filesystem | Download started, no completion logged |
| downloads.claude.ai/releases/darwin/universal/RELEASES.json | Update manifest | Invalid response |

Local workspace state — VM bundle exists but no boot image:

$ ls -lah ~/Library/Application\ Support/Claude/vm_bundles/claudevm.bundle/
-rw-r--r-- 0B Mar 17 06:31 .auto_reinstall_attempted
-rw-r--r-- 17B Mar 11 21:33 gvisorMacAddress
-rw-r--r-- 17B Jan 16 21:47 macAddress
-rw-r--r-- 70B Jan 16 21:47 machineIdentifier
-rw-r--r-- 279M Mar 17 06:27 sessiondata.img
-rw-r--r-- 11B Mar 15 11:21 vmIP

$ du -sh ~/Library/Application\ Support/Claude/vm_bundles/
240M total

Note: .auto_reinstall_attempted (0 bytes, created 06:31) shows the app already tried an automatic reinstall and failed against the same 403.

Region: EU (Germany) — possible CDN edge issue. No VPN/proxy, direct connection.