diff --git a/Programs/CosmOS/Source/cosmos.asm b/Programs/CosmOS/Source/cosmos.asm
index d851f28..02d2cb3 100644
--- a/Programs/CosmOS/Source/cosmos.asm
+++ b/Programs/CosmOS/Source/cosmos.asm
@@ -168,6 +168,20 @@ promptSay:
   LDA.0
   BNA quitRanOut
 
+  ; ---- How this line went, assumed good until something says otherwise ----
+  ;
+  ; Cleared here rather than set at the end of each command, and that is what makes this
+  ; affordable. There are thirty seven ways back to this prompt and only fourteen of them
+  ; are failures, so marking the failures costs fourteen lines and marking the successes
+  ; would cost twenty three - and the twenty three would have to be found again every time
+  ; a command grew a new way to finish. A command that says nothing worked.
+  ;
+  ; A PROGRAM SETS THIS ITSELF, from handleExit, and it runs after this point - so what a
+  ; program made of its work is what stands, not the zero written here before it started.
+  SETD.1 LineFailed
+  RSTA
+  STA.1
+
   SETD.0 CommandLine
   CALL textSplit
 
@@ -268,6 +282,17 @@ promptSay:
   CALL textSame
   BRQ doAssemble
 
+; ---- A command that did not work ----
+;
+; The one place a failure is recorded, so that the thing reading lines out of a file can
+; tell whether to go on. It says nothing: whatever sent us here has already said what was
+; wrong in words, and a number after that is noise. See LastStatus.
+commandFailed:
+  INIA 0x01
+  SETD.1 LineFailed
+  STA.1
+  BRI prompt
+
 promptUnknown:
   ; Nothing built in matched, so the disk is asked before anybody is told they are wrong. A
   ; word this shell does not know is very often the name of a program sitting right there,
@@ -337,7 +362,7 @@ promptSayUnknown:
   SETD.0 CommandLine
   CALL printString
   CALL newLine
-  BRI prompt
+  BRI commandFailed
 
 ; Running out of console leaves the cursor part way along a line, because there was no
 ; return at the end to move it on. Somebody who typed "exit" has already pressed one, and
@@ -544,7 +569,7 @@ dirNoDisk:
   SETD.0 NoDisk
   CALL printString
   CALL newLine
-  BRI prompt
+  BRI commandFailed
 
 ; DP0 names a string. Q is how many spaces pad it out to twenty four columns. A name
 ; already that long gets one space, so that it cannot run into the number after it.
@@ -724,13 +749,13 @@ loadFailed:
   LDD.0.1
   CALL printString
   CALL newLine
-  BRI prompt
+  BRI commandFailed
 
 loadNothingNamed:
   SETD.0 LoadWhat
   CALL printString
   CALL newLine
-  BRI prompt
+  BRI commandFailed
 
 ; ---- loadProgram ----
 ;
@@ -1504,7 +1529,7 @@ fileNoDisk:
 fileComplain:
   CALL printString
   CALL newLine
-  BRI prompt
+  BRI commandFailed
 
 ; ---- run ----
 ;
@@ -1552,7 +1577,7 @@ runNothing:
   SETD.0 NothingLoaded
   CALL printString
   CALL newLine
-  BRI prompt
+  BRI commandFailed
 
 ; DP0 is a string, DP1 is where it should go, and B is how much room there is counting
 ; the zero on the end. What does not fit is left behind, and what is written is a string
@@ -2264,6 +2289,12 @@ handlePrintNumber:
 ; that failed has already said so in words, and a number beside that would be noise. It is
 ; here for the thing that cannot read words - whatever comes to run programs in sequence and
 ; has to decide whether to run the next one.
+;
+; IT IS NOT LineFailed, and the difference is worth keeping. This one is a PROGRAM'S answer
+; and belongs to whoever asks for it, which the shell's own status command does and a test
+; records. Zeroing it as each line began - which is what the script reader wanted - wiped
+; the answer before the command that reports it could read its own line. Two questions, two
+; bytes.
 handleLastStatus:
   SETD.2 LastStatus
   LDA.2
@@ -2333,6 +2364,15 @@ handleExit:
   SETD.1 LastStatus
   STA.1
 
+  ; And the line that started it failed, if the program says it did. The script reader asks
+  ; one question - did this line work - and a program answering "no" is one of the ways it
+  ; can be answered.
+  BRA exitWorked
+  INIA 0x01
+  SETD.1 LineFailed
+  STA.1
+exitWorked:
+
   SETD.1 SystemStack
   LDD.0.1
   MVDS.0
@@ -2445,13 +2485,13 @@ bankNotThere:
   SETD.0 NoSuchBank
   CALL printString
   CALL newLine
-  BRI prompt
+  BRI commandFailed
 
 bankWhat:
   SETD.0 BankUsage
   CALL printString
   CALL newLine
-  BRI prompt
+  BRI commandFailed
 
 ; x [address] - sixty four bytes. d [address] - eight instructions. Without an address
 ; either carries on from where the last one stopped, so reading through memory is one
@@ -2603,12 +2643,12 @@ dumpBadWhere:
   SETD.0 ExamineUsage
   CALL printString
   CALL newLine
-  BRI prompt
+  BRI commandFailed
 dumpNoBank:
   SETD.0 NoSuchBank
   CALL printString
   CALL newLine
-  BRI prompt
+  BRI commandFailed
 
 ; s <address> <byte> <byte> ...
 ;
@@ -2663,13 +2703,13 @@ setReadOnly:
   SETD.0 ReadOnlyText
   CALL printString
   CALL newLine
-  BRI prompt
+  BRI commandFailed
 
 setWhat:
   SETD.0 SetUsage
   CALL printString
   CALL newLine
-  BRI prompt
+  BRI commandFailed
 
 ; g <address>
 ;
@@ -2699,7 +2739,7 @@ goWhat:
   SETD.0 GoUsage
   CALL printString
   CALL newLine
-  BRI prompt
+  BRI commandFailed
 
 ; DP0 names text that textHexWord has just read a number off the front of. LEAVES DP3 past
 ; the digits and any spaces after them, ready for the next one.
@@ -3079,7 +3119,7 @@ assembleWhat:
   SETD.0 AsmUsage
   CALL printString
   CALL newLine
-  BRI prompt
+  BRI commandFailed
 
 ; The mnemonic is in CommandLine's place - AsmLine - and TextRest is what followed it.
 ; Puts the bytes down and steps the cursor past them.
@@ -3463,6 +3503,12 @@ Banner:
 PromptText:
 "> "
 ; Nothing has run yet, so nothing has failed yet.
+; Whether the line the shell is on failed. Read by the script reader and by nothing else,
+; which is why it is a plain flag and not a number: a script wants to know whether to go on,
+; not what went wrong, and what went wrong has already been said in words.
+LineFailed:
+  0x00
+
 LastStatus:
   0x00