[Aleksandergreg]

$?

• It uses real Linux exit codes, not just 0 and 1:

Status	When
0	success
1	most failures, including grep with no match and false
2	shell syntax errors, and errors from ls, grep or sort
126	a script that exists but can't run (directory, not executable, missing #!/bin/sh)
127	an unknown command or missing script

• It works with $?, ${?} and inside double quotes. Single-quoted or escaped $? stays literal.
• A command skipped by && or || keeps the previous status, and a blank or comment line doesn't reset it.
• It carries over between lines, so ls /nope followed by echo $? prints 2.
• Each script starts at 0, and a script's final status becomes the caller's $?.
• In the built game, ls /nope then echo $? printed 2, and an unknown command reported 127.
• Other special parameters ($1, $$, $#) are still rejected.
• The in-game help and the player and safety docs list the codes, and new tests cover each status plus scripts and persistence.

Diagram

• I updated the Mermaid source and confirmed it renders with Mermaid CLI 11, downloaded with npx into the scratchpad only.
• I didn't replace the published SVG with that raw render. All three repo diagrams are hand-made illustrations in a custom style, so I edited the SVG directly to match:
  • a "Split lists" gate before Lex
  • Lex now runs once per pipeline and mentions $?
  • the redirect box notes that > empties the file first and restores it on failure
  • a loop back for the next pipeline, labelled with the ; / && / || rules