The protocol reserved 127 for "this host does not run commands", and the Swift runner used the same code for "the binary is not there" (via a `/usr/bin/env` fallback) — so alibaba's feed read a missing `bl` as a refusal and told the user to capture a console session, when the actual problem was that the command did not exist. The tray surfaced exactly that wrong sentence within minutes of being wired up. - a command that cannot be found or spawned answers 126 ("found it, could not run it"), which the feed treats as an ordinary CLI failure, and the header now names both codes. - a non-zero exit with empty stdout carries stderr as the body, so the feed has something to show. - the CLI failure reason includes the host's first line of text: "bailian CLI failed (exit 126): bl is not on PATH" rather than "exit 126". Mirrored in the TypeScript reference so parity holds.