docs: workaround for bb pr diff | delta scroll break#19
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Bun's runtime issues TCSETS2 on stdin and stderr at exit, restoring the terminal to whatever state it captured at startup. When that state has ICANON|ECHO set, downstream pagers (delta -> less) end up reading from a cooked-mode terminal — keystrokes get echoed, require Enter to act. Root cause is upstream in Bun. Documented the redirect-both workaround until they fix it.
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Summary
Documents a Bun-runtime quirk:
bb pr diff <id> | delta(or any pipe to aless-using pager) breaks scrolling on subsequent invocations. Workaround: redirect both stdin and stderr away from the terminal.Root cause (diagnosed via strace)
Bun's runtime calls
TCSETS2on both stdin and stderr at process exit, restoring whichever terminal state it captured at startup. When the capturedc_lflagincludesICANON|ECHO, the terminal ends up in cooked mode for downstreamless, which can't get raw keystrokes.Strace evidence (relevant flag in
c_lflag):ISIG|IEXTEN|ECHOCTL|ECHOKE(raw)ISIG|ICANON|ECHO|ECHOE|ECHOK|IEXTEN|ECHOCTL|ECHOKE(cooked)Verified:
</dev/null 2>/dev/nullworks; either alone doesn't. So both fds matter.Out of scope
The fix belongs upstream in Bun. Will file a bug there with the strace as a minimal reproducer; this PR is just documentation so users aren't blocked.