This is a meta-issue for tracking multiple related but distinct stderr/stdout issues.

Below are checklists indicating the progress of these issues & pull requests.
A checkmark indicates it is resolved (or merged).

This issue encompasses the following issues:

• Chunked stdout/stderr drops writes if terminated early. Chunked stdout/stderr drops writes if terminated early. #784
• Interleaved stdout/stderr on terminals (TTYs)
  • Part of: stdio buffered writes (chunked) issues & process.exit() truncation stdio buffered writes (chunked) issues & process.exit() truncation #6456
• Missing or truncated error message Missing or truncated error message #6867

And the following pull requests:

• process: flush stdout/stderr upon process.exit() process: flush stdout/stderr upon process.exit() #6773
• tty: set the handle to blocking mode tty: set the handle to blocking mode #6816
• tty: use blocking mode on OS X tty: use blocking mode on OS X #6895
• unix: add uv_flush_sync unix: add uv_flush_sync libuv/libuv#876
• unix,stream: fix getting the correct fd for a handle unix,stream: fix getting the correct fd for a handle #6838
  • Should be backported to v4.x (and maybe v5.x)

The current item in focus is:
n/a

The TTY (Terminal) issues have been resolved. Pipes still remain a problem.

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This pr was a result of the discussion in #6968 to better track all the efforts going on here.

[EDIT by @Trott: Did some edits around the 6773 PR checklist item, but undid them]