Clipboard sharing does not work with macOS 14 (Sonoma) guests (works on Sequoia/Tahoe with the same agent)

[AlexandrPkhm]

Summary

Host↔guest clipboard sharing is completely non-functional when the guest is macOS 14 (Sonoma), while the same host and the same tart-guest-agent version work fine with a macOS 26 (Tahoe) guest. This extends the observation in #1167 (comment) ("clipboard sharing does not work … unlikely an agent issue because macos-sequoia-xcode works and has the same agent version") with byte-level evidence that the failure is at the SPICE vdagent layer and is guest-OS-version dependent.

Environment

• Host: Apple Silicon (arm64), macOS 27.0 (26A428)
• tart: 2.32.1
• Guests: ghcr.io/cirruslabs/macos-sonoma-base:latest (macOS 14) and ghcr.io/cirruslabs/macos-tahoe-base:latest (macOS 26), both cloned locally
• tart-guest-agent 0.14.1 on both guests, installed identically (launchd LaunchAgent org.cirruslabs.tart-guest-agent, --run-agent)

Steps to reproduce

1. tart run macos14-sonoma
2. Copy text on the host, paste in the guest → nothing appears.
3. Copy text in the guest, paste on the host → nothing appears.
4. Repeat with macos26-tahoe → both directions work.

Diagnostics

The guest side is healthy in every way we could check:

• agent running, --run-vdagent active, RPC on AF_VSOCK:8080 up
• SPICE port held by the agent: lsof -p <agent> | grep spice → /dev/tty.com.redhat.spice.0
• the guest's own pasteboard works (pbpaste/pbcopy fine inside the guest)

The decisive difference is how much data ever crosses the SPICE channel:

Guest	lsof offset on /dev/tty.com.redhat.spice.0	Clipboard
macOS 14 (Sonoma)	0t0 headless / 0t36 windowed — effectively zero	dead, both directions
macOS 26 (Tahoe)	0t693	works, both directions

On Sonoma the vdagent protocol never completes — no clipboard data flows in either direction, with identical host, agent binary, launchd setup, and run flags. This matches the finding that macos-sequoia-xcode works while macos-sonoma-xcode does not, with the same agent version.

Restarting the guest agent (launchctl kickstart -k gui/$(id -u)/org.cirruslabs.tart-guest-agent) does not help on Sonoma — the channel stays at zero bytes.

Additional observation (macOS 26, possibly unrelated)

On the Tahoe guest we also intermittently saw the agent log failed to run vdagent: unexpected EOF with backoff retries after repeated VM start/stop cycles; clipboard still worked in a clean boot. Mentioning in case it's related, but the Sonoma failure above is deterministic and the primary issue.

Related

• [Bug] Special symbols are being passed through incorrectly to macOS VM #1167
• [Bug] Special symbols are being passed through incorrectly to macOS VM #1167 (comment)