Linux x86_64, real fish 4.9.3 via node-pty, --no-config, no client terminal-query replies. Direct PTY probe; Manager spawn environment covered separately by tests.
Before (fish_features absent): prompt 10125 ms; DA1 at 110 ms and 10125 ms; warning true.
After (fish_features=no-query-term): prompt 12 ms; no DA1; warning false.

Integrated web app check: dev server on isolated worktree .t3; opened terminal drawer through actual browser UI, typed command via Terminal input. Real persisted terminal output:
T3_FISH_FEATURES=no-query-term
FISH_COMMAND_OK
The command invoked fish 4.9.3 from the server-spawned bash terminal and completed successfully.