diff --git a/CHANGELOG b/CHANGELOG
index 1dd4b21053..5bd772ff73 100644
--- a/CHANGELOG
+++ b/CHANGELOG
@@ -25,6 +25,10 @@ git-annex (10.20230408) UNRELEASED; urgency=medium
   * assistant --autostop: Avoid crashing when ~/.config/git-annex/autostart
     lists a directory that it cannot chdir to.
   * Honor --force option when operating on a local git remote.
+  * When a nonexistant file is passed to a command and 
+    --json-error-messages is enabled, output a JSON object indicating the
+    problem. (But git ls-files --error-unmatch still displays errors about
+    such files in some situations.)
 
  -- Joey Hess <id@joeyh.name>  Sat, 08 Apr 2023 13:57:18 -0400
 
diff --git a/CmdLine/Seek.hs b/CmdLine/Seek.hs
index d2815383a5..18be0a44f7 100644
--- a/CmdLine/Seek.hs
+++ b/CmdLine/Seek.hs
@@ -147,9 +147,9 @@ withPairs a params = sequence_ $
 	pairs c (x:y:xs) = pairs ((x,y):c) xs
 	pairs _ _ = giveup "expected pairs"
 
-withFilesToBeCommitted :: ((SeekInput, RawFilePath) -> CommandSeek) -> WorkTreeItems -> CommandSeek
-withFilesToBeCommitted a l = seekFiltered (const (pure True)) a $
-	seekHelper id WarnUnmatchWorkTreeItems (const LsFiles.stagedNotDeleted) l
+withFilesToBeCommitted :: WarnUnmatchWhen -> ((SeekInput, RawFilePath) -> CommandSeek) -> WorkTreeItems -> CommandSeek
+withFilesToBeCommitted ww a l = seekFiltered (const (pure True)) a $
+	seekHelper id ww (const LsFiles.stagedNotDeleted) l
 
 {- unlocked pointer files that are staged, and whose content has not been
  - modified-}
@@ -512,15 +512,15 @@ seekHelper c ww a (WorkTreeItems l) = do
 		and <$> sequence cleanups
 seekHelper _ _ _ NoWorkTreeItems = return ([], pure True)
 
-data WarnUnmatchWhen = WarnUnmatchLsFiles | WarnUnmatchWorkTreeItems
+data WarnUnmatchWhen = WarnUnmatchLsFiles String | WarnUnmatchWorkTreeItems String
 
 seekOptions :: WarnUnmatchWhen -> Annex [LsFiles.Options]
-seekOptions WarnUnmatchLsFiles =
+seekOptions (WarnUnmatchLsFiles _) =
 	ifM (annexSkipUnknown <$> Annex.getGitConfig)
 		( return [] 
 		, return [LsFiles.ErrorUnmatch]
 		)
-seekOptions WarnUnmatchWorkTreeItems = return []
+seekOptions (WarnUnmatchWorkTreeItems _) = return []
 
 -- Items in the work tree, which may be files or directories.
 data WorkTreeItems
@@ -554,23 +554,23 @@ workTreeItems = workTreeItems' (AllowHidden False)
 
 workTreeItems' :: AllowHidden -> WarnUnmatchWhen -> CmdParams -> Annex WorkTreeItems
 workTreeItems' (AllowHidden allowhidden) ww ps = case ww of
-	WarnUnmatchWorkTreeItems -> runcheck
-	WarnUnmatchLsFiles -> 
+	(WarnUnmatchWorkTreeItems action) -> runcheck action
+	(WarnUnmatchLsFiles action) -> 
 		ifM (annexSkipUnknown <$> Annex.getGitConfig)
-			( runcheck
+			( runcheck action
 			, return $ WorkTreeItems ps
 			)
   where
-	runcheck = do
+	runcheck action = do
 		currbranch <- getCurrentBranch
 		stopattop <- prepviasymlink
 		ps' <- flip filterM ps $ \p -> do
 			let p' = toRawFilePath p
 			relf <- liftIO $ relPathCwdToFile p'
 			ifM (not <$> (exists p' <||> hidden currbranch relf))
-				( prob (QuotedPath (toRawFilePath p) <> " not found")
+				( prob action FileNotFound p' "not found"
 				, ifM (viasymlink stopattop (upFrom relf))
-					( prob (QuotedPath (toRawFilePath p) <> " is beyond a symbolic link")
+					( prob action FileBeyondSymbolicLink p' "is beyond a symbolic link"
 					, return True
 					)
 				)
@@ -605,8 +605,8 @@ workTreeItems' (AllowHidden allowhidden) ww ps = case ww of
 			<$> catObjectMetaDataHidden f currbranch
 		| otherwise = return False
 
-	prob msg = do
-		toplevelWarning False msg
+	prob action errorid p msg = do
+		toplevelFileProblem False errorid msg action p Nothing (SeekInput [fromRawFilePath p])
 		Annex.incError
 		return False
 	
diff --git a/Command/Add.hs b/Command/Add.hs
index e1e2c32e79..3a00aaa637 100644
--- a/Command/Add.hs
+++ b/Command/Add.hs
@@ -119,7 +119,7 @@ seek o = startConcurrency commandStages $ do
 			-- are not known to git yet, since this will add
 			-- them. Instead, have workTreeItems warn about other
 			-- problems, like files that don't exist.
-			let ww = WarnUnmatchWorkTreeItems
+			let ww = WarnUnmatchWorkTreeItems "add"
 			l <- workTreeItems ww (addThese o)
 			let go b a = a ww (commandAction . gofile b) l
 			unless (updateOnly o) $
diff --git a/Command/Copy.hs b/Command/Copy.hs
index 5c9e97dcef..0034bb26cb 100644
--- a/Command/Copy.hs
+++ b/Command/Copy.hs
@@ -60,7 +60,7 @@ seek' o fto = startConcurrency (Command.Move.stages fto) $ do
 		Batch fmt -> batchOnly (keyOptions o) (copyFiles o) $
 			batchAnnexed fmt seeker keyaction
   where
-	ww = WarnUnmatchLsFiles
+	ww = WarnUnmatchLsFiles "copy"
 	
 	seeker = AnnexedFileSeeker
 		{ startAction = start o fto
diff --git a/Command/Drop.hs b/Command/Drop.hs
index 0a55b4937a..bf0671dde8 100644
--- a/Command/Drop.hs
+++ b/Command/Drop.hs
@@ -74,7 +74,7 @@ seek o = startConcurrency commandStages $ do
 		Batch fmt -> batchOnly (keyOptions o) (dropFiles o) $
 			batchAnnexed fmt seeker (startKeys o from)
   where
-	ww = WarnUnmatchLsFiles
+	ww = WarnUnmatchLsFiles "drop"
 
 start :: DropOptions -> Maybe Remote -> SeekInput -> RawFilePath -> Key -> CommandStart
 start o from si file key = start' o from key afile ai si
diff --git a/Command/FilterBranch.hs b/Command/FilterBranch.hs
index f552e0f4c7..0e1b0a7514 100644
--- a/Command/FilterBranch.hs
+++ b/Command/FilterBranch.hs
@@ -192,4 +192,4 @@ seek o = withOtherTmp $ \tmpdir -> do
 	c <- inRepo $ Git.commitTree cmode cmessage [] t
 	liftIO $ putStrLn (fromRef c)
   where
-	ww = WarnUnmatchLsFiles
+	ww = WarnUnmatchLsFiles "filter-branch"
diff --git a/Command/Find.hs b/Command/Find.hs
index 5dd6a4aac8..21e2a56bd2 100644
--- a/Command/Find.hs
+++ b/Command/Find.hs
@@ -75,7 +75,7 @@ seek o = do
 		Batch fmt -> batchOnly (keyOptions o) (findThese o) $
 			batchAnnexedFiles fmt seeker
   where
-	ww = WarnUnmatchLsFiles
+	ww = WarnUnmatchLsFiles "find"
 
 -- Default to needing content to be present, but if the user specified a
 -- limit, content does not need to be present.
diff --git a/Command/Fix.hs b/Command/Fix.hs
index 3cfa0d8f39..a7aba56de2 100644
--- a/Command/Fix.hs
+++ b/Command/Fix.hs
@@ -35,7 +35,7 @@ seek :: CmdParams -> CommandSeek
 seek ps = unlessM crippledFileSystem $
 	withFilesInGitAnnex ww seeker =<< workTreeItems ww ps
   where
-	ww = WarnUnmatchLsFiles
+	ww = WarnUnmatchLsFiles "fix"
 	seeker = AnnexedFileSeeker
 		{ startAction = start FixAll
 		, checkContentPresent = Nothing
diff --git a/Command/Fsck.hs b/Command/Fsck.hs
index f3b1814466..b25e49b73e 100644
--- a/Command/Fsck.hs
+++ b/Command/Fsck.hs
@@ -113,7 +113,7 @@ seek o = startConcurrency commandStages $ do
 	cleanupIncremental i
 	void $ tryIO $ recordActivity Fsck u
   where
-	ww = WarnUnmatchLsFiles
+	ww = WarnUnmatchLsFiles "fsck"
 
 checkDeadRepo :: UUID -> Annex ()
 checkDeadRepo u =
diff --git a/Command/Get.hs b/Command/Get.hs
index f11296c76f..7d3d4a2ef1 100644
--- a/Command/Get.hs
+++ b/Command/Get.hs
@@ -53,7 +53,7 @@ seek o = startConcurrency transferStages $ do
 		Batch fmt -> batchOnly (keyOptions o) (getFiles o) $
 			batchAnnexed fmt seeker (startKeys from)
   where
-	ww = WarnUnmatchLsFiles
+	ww = WarnUnmatchLsFiles "get"
 
 start :: GetOptions -> Maybe Remote -> SeekInput -> RawFilePath -> Key -> CommandStart
 start o from si file key = start' expensivecheck from key afile ai si
diff --git a/Command/Inprogress.hs b/Command/Inprogress.hs
index 58c5bcfd77..8ab920242f 100644
--- a/Command/Inprogress.hs
+++ b/Command/Inprogress.hs
@@ -49,7 +49,7 @@ seek o = do
 			withFilesInGitAnnex ww seeker
 				=<< workTreeItems ww (inprogressFiles o)
   where
-	ww = WarnUnmatchLsFiles
+	ww = WarnUnmatchLsFiles "inprogress"
 
 start :: IsTerminal -> S.Set Key -> SeekInput -> RawFilePath -> Key -> CommandStart
 start isterminal s _si _file k
diff --git a/Command/List.hs b/Command/List.hs
index 1de9d74983..b14c55d707 100644
--- a/Command/List.hs
+++ b/Command/List.hs
@@ -56,7 +56,7 @@ seek o = do
 		}
 	withFilesInGitAnnex ww seeker =<< workTreeItems ww (listThese o)
   where
-	ww = WarnUnmatchLsFiles
+	ww = WarnUnmatchLsFiles "list"
 
 getList :: ListOptions -> Annex [(UUID, RemoteName, TrustLevel)]
 getList o
diff --git a/Command/Lock.hs b/Command/Lock.hs
index 352abb3745..d547a07f93 100644
--- a/Command/Lock.hs
+++ b/Command/Lock.hs
@@ -32,7 +32,7 @@ cmd = withAnnexOptions [jsonOptions, annexedMatchingOptions] $
 seek :: CmdParams -> CommandSeek
 seek ps = withFilesInGitAnnex ww seeker =<< workTreeItems ww ps
   where
-	ww = WarnUnmatchLsFiles
+	ww = WarnUnmatchLsFiles "lock"
 	seeker = AnnexedFileSeeker
 		{ startAction = start
 		, checkContentPresent = Nothing
diff --git a/Command/Log.hs b/Command/Log.hs
index 645e982675..cbfe0edc82 100644
--- a/Command/Log.hs
+++ b/Command/Log.hs
@@ -105,7 +105,7 @@ seek o = ifM (null <$> Annex.Branch.getUnmergedRefs)
 	, giveup "This repository is read-only, and there are unmerged git-annex branches, which prevents displaying location log changes. (Set annex.merge-annex-branches to false to ignore the unmerged git-annex branches.)"
 	)
   where
-	ww = WarnUnmatchLsFiles
+	ww = WarnUnmatchLsFiles "log"
 
 start :: LogOptions -> (FilePath -> Outputter) -> SeekInput -> RawFilePath -> Key -> CommandStart
 start o outputter _ file key = do
diff --git a/Command/MetaData.hs b/Command/MetaData.hs
index b0bb982793..b01b751641 100644
--- a/Command/MetaData.hs
+++ b/Command/MetaData.hs
@@ -76,7 +76,7 @@ seek :: MetaDataOptions -> CommandSeek
 seek o = case batchOption o of
 	NoBatch -> do
 		c <- currentVectorClock
-		let ww = WarnUnmatchLsFiles
+		let ww = WarnUnmatchLsFiles "metadata"
 		let seeker = AnnexedFileSeeker
 			{ startAction = start c o
 			, checkContentPresent = Nothing
diff --git a/Command/Migrate.hs b/Command/Migrate.hs
index f4fb632353..42f119fffa 100644
--- a/Command/Migrate.hs
+++ b/Command/Migrate.hs
@@ -41,7 +41,7 @@ optParser desc = MigrateOptions
 seek :: MigrateOptions -> CommandSeek
 seek o = withFilesInGitAnnex ww seeker =<< workTreeItems ww (migrateThese o)
   where
-	ww = WarnUnmatchLsFiles
+	ww = WarnUnmatchLsFiles "migrate"
 	seeker = AnnexedFileSeeker
 		{ startAction = start o
 		, checkContentPresent = Nothing
diff --git a/Command/Mirror.hs b/Command/Mirror.hs
index f169aae928..8ec97e467f 100644
--- a/Command/Mirror.hs
+++ b/Command/Mirror.hs
@@ -50,7 +50,7 @@ seek o = startConcurrency stages $
 	stages = case fromToOptions o of
 		FromRemote _ -> transferStages
 		ToRemote _ -> commandStages
-	ww = WarnUnmatchLsFiles
+	ww = WarnUnmatchLsFiles "mirror"
 	seeker = AnnexedFileSeeker
 		{ startAction = start o
 		, checkContentPresent = Nothing
diff --git a/Command/Move.hs b/Command/Move.hs
index fb3cd03ffa..77f7d6d3f1 100644
--- a/Command/Move.hs
+++ b/Command/Move.hs
@@ -84,7 +84,7 @@ seek' o fto = startConcurrency (stages fto) $ do
 		, usesLocationLog = True
 		}
 	keyaction = startKey fto (removeWhen o)
-	ww = WarnUnmatchLsFiles
+	ww = WarnUnmatchLsFiles "move"
 
 stages :: FromToHereOptions -> UsedStages
 stages (FromOrToRemote (FromRemote _)) = transferStages
diff --git a/Command/Multicast.hs b/Command/Multicast.hs
index faa0a09aa1..112a364046 100644
--- a/Command/Multicast.hs
+++ b/Command/Multicast.hs
@@ -131,7 +131,7 @@ send ups fs = do
 	-- expensive.
 	starting "sending files" (ActionItemOther Nothing) (SeekInput []) $
 		withTmpFile "send" $ \t h -> do
-			let ww = WarnUnmatchLsFiles
+			let ww = WarnUnmatchLsFiles "multicast"
 			(fs', cleanup) <- seekHelper id ww LsFiles.inRepo
 				=<< workTreeItems ww fs
 			matcher <- Limit.getMatcher
diff --git a/Command/PreCommit.hs b/Command/PreCommit.hs
index dbb2ce3e25..d8fdeea197 100644
--- a/Command/PreCommit.hs
+++ b/Command/PreCommit.hs
@@ -32,10 +32,10 @@ cmd = command "pre-commit" SectionPlumbing
 
 seek :: CmdParams -> CommandSeek
 seek ps = do
-	let ww = WarnUnmatchWorkTreeItems
+	let ww = WarnUnmatchWorkTreeItems "pre-commit"
 	l <- workTreeItems ww ps
 	-- fix symlinks to files being committed
-	flip withFilesToBeCommitted l $ \(si, f) -> commandAction $
+	flip (withFilesToBeCommitted ww) l $ \(si, f) -> commandAction $
 		maybe stop (Command.Fix.start Command.Fix.FixSymlinks si f)
 			=<< isAnnexLink f
 	-- after a merge conflict or git cherry-pick or stash, pointer
diff --git a/Command/Sync.hs b/Command/Sync.hs
index 3806184a9e..def4d81c54 100644
--- a/Command/Sync.hs
+++ b/Command/Sync.hs
@@ -794,7 +794,7 @@ seekSyncContent o rs currbranch = do
 		in seekFiltered (const (pure True)) filterer $
 			seekHelper id ww (LsFiles.inRepoOrBranch origbranch) l 
 
-	ww = WarnUnmatchLsFiles
+	ww = WarnUnmatchLsFiles "sync"
 
 	gofile bloom mvar _ f k = 
 		go (Right bloom) mvar (AssociatedFile (Just f)) k
diff --git a/Command/Unannex.hs b/Command/Unannex.hs
index d876f79b06..799a31ef8d 100644
--- a/Command/Unannex.hs
+++ b/Command/Unannex.hs
@@ -30,7 +30,7 @@ cmd = withAnnexOptions [annexedMatchingOptions] $
 seek :: CmdParams -> CommandSeek
 seek ps = withFilesInGitAnnex ww (seeker False) =<< workTreeItems ww ps
   where
-	ww = WarnUnmatchLsFiles
+	ww = WarnUnmatchLsFiles "unannex"
 
 seeker :: Bool -> AnnexedFileSeeker
 seeker fast = AnnexedFileSeeker
diff --git a/Command/Uninit.hs b/Command/Uninit.hs
index 57057e58f4..aee530e796 100644
--- a/Command/Uninit.hs
+++ b/Command/Uninit.hs
@@ -53,13 +53,13 @@ seek ps = do
 	l <- workTreeItems ww ps
 	withFilesNotInGit
 		(CheckGitIgnore False)
-		WarnUnmatchWorkTreeItems
+		(WarnUnmatchWorkTreeItems "uninit")
 		checksymlinks
 		l
 	withFilesInGitAnnex ww (Command.Unannex.seeker True) l
 	finish
   where
-	ww = WarnUnmatchLsFiles
+	ww = WarnUnmatchLsFiles "uninit"
 	checksymlinks (_, f) = 
 		commandAction $ lookupKey f >>= \case
 			Nothing -> stop
diff --git a/Command/Unlock.hs b/Command/Unlock.hs
index d338c00dcd..c0c79a7a6a 100644
--- a/Command/Unlock.hs
+++ b/Command/Unlock.hs
@@ -33,7 +33,7 @@ mkcmd n d = withAnnexOptions [jsonOptions, annexedMatchingOptions] $
 seek :: CmdParams -> CommandSeek
 seek ps = withFilesInGitAnnex ww seeker =<< workTreeItems ww ps
   where
-	ww = WarnUnmatchLsFiles
+	ww = WarnUnmatchLsFiles "unlock"
 	seeker = AnnexedFileSeeker
 		{ startAction = start
 		, checkContentPresent = Nothing
diff --git a/Command/Whereis.hs b/Command/Whereis.hs
index 9052147249..c8ca119ed6 100644
--- a/Command/Whereis.hs
+++ b/Command/Whereis.hs
@@ -64,7 +64,7 @@ seek o = do
 		Batch fmt -> batchOnly (keyOptions o) (whereisFiles o) $
 			batchAnnexed fmt seeker (startKeys o m)
   where
-	ww = WarnUnmatchLsFiles
+	ww = WarnUnmatchLsFiles "whereis"
 
 start :: WhereisOptions -> M.Map UUID Remote -> SeekInput -> RawFilePath -> Key -> CommandStart
 start o remotemap si file key = 
diff --git a/Messages.hs b/Messages.hs
index 565822365c..78efd4873f 100644
--- a/Messages.hs
+++ b/Messages.hs
@@ -27,6 +27,8 @@ module Messages (
 	showEndFail,
 	showEndResult,
 	endResult,
+	ErrorId(..),
+	toplevelFileProblem,
 	toplevelWarning,
 	warning,
 	earlyWarning,
@@ -34,6 +36,7 @@ module Messages (
 	indent,
 	JSON.JSONChunk(..),
 	maybeShowJSON,
+	maybeShowJSON',
 	showFullJSON,
 	showCustom,
 	showHeader,
@@ -197,8 +200,18 @@ endResult :: Bool -> S.ByteString
 endResult True = "ok"
 endResult False = "failed"
 
+toplevelMsg :: StringContainingQuotedPath -> StringContainingQuotedPath
+toplevelMsg = ("git-annex: " <>)
+
+toplevelFileProblem :: Bool -> ErrorId -> StringContainingQuotedPath -> String -> RawFilePath -> Maybe Key -> SeekInput -> Annex ()
+toplevelFileProblem makeway errorid msg action file mkey si = do
+	maybeShowJSON' $ JSON.start action (Just file) mkey si
+	maybeShowJSON' $ JSON.errorid errorid
+	warning' makeway id (toplevelMsg (QuotedPath file <> " " <> msg))
+	maybeShowJSON' $ JSON.end False
+
 toplevelWarning :: Bool -> StringContainingQuotedPath -> Annex ()
-toplevelWarning makeway s = warning' makeway id ("git-annex: " <> s)
+toplevelWarning makeway s = warning' makeway id (toplevelMsg s)
 
 warning :: StringContainingQuotedPath -> Annex ()
 warning = warning' True indent
@@ -207,10 +220,10 @@ earlyWarning :: StringContainingQuotedPath -> Annex ()
 earlyWarning = warning' False id
 
 warning' :: Bool -> (S.ByteString -> S.ByteString) -> StringContainingQuotedPath -> Annex ()
-warning' makeway consolewhitespacef w = do
+warning' makeway consolewhitespacef msg = do
 	when makeway $
 		outputMessage JSON.none id "\n"
-	outputError (\s -> consolewhitespacef s <> "\n") w
+	outputError (\s -> consolewhitespacef s <> "\n") msg
 
 {- Not concurrent output safe. -}
 warningIO :: String -> IO ()
@@ -226,6 +239,9 @@ indent = S.intercalate "\n" . map ("  " <>) . S8.lines
 maybeShowJSON :: JSON.JSONChunk v -> Annex ()
 maybeShowJSON v = void $ withMessageState $ bufferJSON (JSON.add v)
 
+maybeShowJSON' :: JSON.JSONBuilder -> Annex ()
+maybeShowJSON' v = void $ withMessageState $ bufferJSON v
+
 {- Shows a complete JSON value, only when in json mode. -}
 showFullJSON :: JSON.JSONChunk v -> Annex Bool
 showFullJSON v = withMessageState $ bufferJSON (JSON.complete v)
diff --git a/Messages/JSON.hs b/Messages/JSON.hs
index 8960dd04a2..9f569c09ea 100644
--- a/Messages/JSON.hs
+++ b/Messages/JSON.hs
@@ -20,6 +20,7 @@ module Messages.JSON (
 	addErrorMessage,
 	note,
 	info,
+	errorid,
 	add,
 	complete,
 	progress,
@@ -51,6 +52,7 @@ import Utility.Metered
 import Utility.Percentage
 import Utility.Aeson
 import Utility.FileSystemEncoding
+import Types.Messages
 
 -- A global lock to avoid concurrent threads emitting json at the same time.
 {-# NOINLINE emitLock #-}
@@ -68,7 +70,8 @@ emit' b = do
 	putMVar emitLock ()
 
 -- Building up a JSON object can be done by first using start,
--- then add and note any number of times, and finally complete.
+-- then add and note and errorid any number of times, and finally
+-- complete.
 type JSONBuilder = Maybe (Object, Bool) -> Maybe (Object, Bool)
 
 none :: JSONBuilder
@@ -112,6 +115,12 @@ note s (Just (o, e)) = Just (HM.unionWith combinelines (HM.singleton "note" (toJ
 		String (old <> "\n" <> new)
 	combinelines new _old = new
 
+errorid :: ErrorId -> JSONBuilder
+errorid _ Nothing = Nothing
+errorid eid (Just (o, e)) = Just (HM.unionWith replaceold (HM.singleton "errorid" (toJSON' (show eid))) o, e)
+  where
+	replaceold new _old = new
+
 info :: String -> JSONBuilder
 info s _ = case j of
 	Object o -> Just (o, True)
diff --git a/Types/Messages.hs b/Types/Messages.hs
index e80dc86d63..15cbfc2a74 100644
--- a/Types/Messages.hs
+++ b/Types/Messages.hs
@@ -84,3 +84,9 @@ data SerializedOutput
 data SerializedOutputResponse
 	= ReadyPrompt
 	deriving (Eq, Show)
+
+-- | Error identifiers. Avoid changing these.
+data ErrorId
+	= FileNotFound
+	| FileBeyondSymbolicLink
+	deriving (Show)
diff --git a/doc/todo/api_for_telling_when_nonexistant_or_non_git_files_passed/comment_8_2550e1760dcfb90c9c2ca1ee145adcf1._comment b/doc/todo/api_for_telling_when_nonexistant_or_non_git_files_passed/comment_8_2550e1760dcfb90c9c2ca1ee145adcf1._comment
new file mode 100644
index 0000000000..a72b9b3286
--- /dev/null
+++ b/doc/todo/api_for_telling_when_nonexistant_or_non_git_files_passed/comment_8_2550e1760dcfb90c9c2ca1ee145adcf1._comment
@@ -0,0 +1,19 @@
+[[!comment format=mdwn
+ username="joey"
+ subject="""comment 8"""
+ date="2023-04-25T22:45:24Z"
+ content="""
+Ok, implemented the simple alternative. Here's how it looks:
+
+	joey@darkstar:~/tmp/xxx>git-annex add 'dne' --json --json-error-messages
+	{"command":"add","error-messages":["git-annex: dne not found"],"errorid":"FileNotFound","file":"dne","input":["dne"],"success":false}
+	add: 1 failed
+
+The errorid will remain stable. I can add those to other error messages
+now, on request BTW.
+
+Note that when git-annex relies on `git ls-files --error-unmatch` to
+complain about nonexistant or non-git files, the error messages from
+git will still be displayed to stderr, not this nice json. So
+datalad will need to keep its parser for that part.
+"""]]