Unclear Whether CLAUDE_CODE_PLAIN_DELTA_FAST_PATH still controls the streaming shortcut on its own is not clear.
What
In headless mode, where Claude Code runs without its interactive screen, there is a shortcut that sends streamed pieces of text straight to output. The debug log line for that shortcut was reworded and no longer names CLAUDE_CODE_PLAIN_DELTA_FAST_PATH, although that variable still appears in the code.
The information Claude Code builds for each turn now also includes the thinking settings, fast mode and the current permission settings.
Why
Whether the streaming shortcut is used may now depend on a condition other than the environment variable alone.
Names in the bundleCLAUDE_CODE_PLAIN_DELTA_FAST_PATH
Something disagreesSomething we can check disagrees with this entry, or the writer said they could not settle it.
The writer flagged doubt
Whether `CLAUDE_CODE_PLAIN_DELTA_FAST_PATH` still controls the streaming shortcut on its own is not clear.