All cases

Every case documents a real failure — symptom, repro, cause, workaround — with public citations.

AliasesCommands that are not what they claim to be.

5

command v noop›curl alias›Get-Command vs where.exe›NPM PS1 not comspec›npm spawn: ENOENT & EINVAL›

QuotingArguments shredded between shells.

16

-WindowStyle vs windowsHide›'and' is not a separator›Backslash ends quoted span›bun ps windowstyle argv›CMD c newline not separator›CMD shim reparses argv›CMD start ampersand splits›createprocess cmdline 32767›dollar backslash vars›dq regex interpolates›oss native arg quoting›piped IEX drops params›prose as unknown flags›ps file extension dispatch›Semicolon splits Start-Process›shell true fallback injects›

StreamsOutput that goes places you did not expect.

4

dev null redirect›native stderr errorrecord›out string multiplies stderr›write host not success stream›

EncodingBOMs, code pages, and corrupted bytes.

11

BOM less PS1 CP949›bomless bat oem codepage›CMD lf drops first byte›lf pure transform mixes eol›oss outfile BOM›python subprocess locale encoding›python textio newline translation›redirected ps output mojibake›split n leaves cr›tee object UTF-16›utf8 BOM still breaks grep›

Exit codesSuccess and failure, misreported.

9

exit code vs dollar q›explorer exits one›if(native) truthiness›IRM IEX kills host›kill hits one pid or the whole tree›process exit fastfail 0xc0000409›pwsh leaks lastexitcode›Start-Process exit codes›startup artifact is not a process›

Versions5.1 and 7 are different languages.

3

PS 5.1 no and and›PS 5.1 vs 7 split›strictmode missing property›

Env & pathsPATH, registry env, and Win32 path rules.

26

atomic rename loses to scanner›CMD unc cwd not supported›dynamic import needs file url›env domain principal›env PATH vs PATH casing›envpath pollutes user›esm is main file url›file url encodes backslash›icacls inheritance r empty dacl›known folder empty not error›max PATH 260›node PATH host delimiter›PATH case sensitive map›PATH colon not delimiter›PATH dot hijacks bare NPM›PATH unmatched quote swallows›PATHEXT bare name ENOENT›PATHEXT exe beats CMD›reserved dos device names›session PATH stale›tcp tcb survives listener›test PATH trailing whitespace›unlink while open ebusy›windowsapps alias EPERM›wsl unc rejects nt acl›wslenv shared with host›

CI & agentsRunners and agents assuming POSIX.

4

actions default shell›CMD posix env prefix›execution policy file block›NPM script runs under CMD›

CollectionsTypes that change with element count.

3

-ne filters collections›get content scalar collapse›return does not mean return›

ParsingSerialization and culture-sensitive parsing.

6

altgr reports as ctrl alt›basename split slash only›convertto JSON depth two›culture comma decimal cast›localized cli output parsing›zip entry drive letter escapes›