`browser_batch` always fails with "No tab available" while single-action tools work on the same tabId

browser_batch returns No tab available for any batch — including a single-action batch [{"name":"computer","params":{"action":"screenshot","tabId":<id>}}] — while the identical action via the individual computer / navigate tools succeeds on the same explicit tabId immediately after (verified back-to-back in the same session).

Reproduced across:

• two different Claude Code sessions on different days;
• three fresh tab groups (including ones created via tabs_context_mcp with createIfEmpty: true);
• extension disconnect/reconnect cycles (list_connected_browsers + select_browser);
• a full Chrome quit + relaunch (to pick up pending extension updates);
• Claude Code 2.1.216 (latest at the time of writing).

Environment: macOS (Darwin 25.5.0), current stable Chrome, Claude Code CLI running in a terminal.

Hypothesis from the failure shape: the batch executor resolves the session's active tab from internal state instead of honoring the per-action tabId params — single-action tools take the explicit tabId path and work; the batch path never finds a tab even when tabs_context_mcp lists it.

Happy to provide timestamps or run further repro steps if useful.