Browser pane crashes Claude Code when pointed at a port-bound local server (preview_start with launch.json)

Environment: Windows 11 Pro 10.0.26200, Claude Code Desktop App version 1.34493.1 (255293), build dated 2026-08-21

Steps to reproduce:

1. Create a .claude/launch.json with a config that runs a local server bound to a port (reproduced with python -m http.server 8123)
2. Call preview_start with that config's name
3. navigate to the resulting localhost URL via the Browser pane
4. Call computer (screenshot) against that tab

Observed: Claude Code (the application itself) crashes.

Additional technical details:

• Port mismatch: launch.json specified "port": 8123, but the tool's response reported "port": 5173 and the Browser pane actually opened http://localhost:5173, not 8123 — suggesting a proxy/port-forwarding layer between the configured server port and what the Browser pane connects to.

• Crash timing: preview_start succeeded (valid tabId returned) and the subsequent navigate call also completed normally. The crash occurs on the next action — a computer screenshot call against the now-loaded port-bound tab — not at preview_start or navigate time. Points to a failure in compositing/screenshotting a page served through the proxied local port.

• No crash over file://: opening the identical HTML file directly via a file:// URL (no server) does not crash the app, and screenshots against that tab work normally — though local relative asset references (e.g. <img src="images/foo.png">) silently fail to load in that mode (zero network requests fire for them), a separate unrelated issue.

• Reproducibility: at least the second occurrence of this class of crash (Browser pane + locally-served content on a port) on the same project across different sessions; this occurrence is the first with enough detail captured to pin down the exact preview_start → navigate → screenshot sequence.