diff --git a/Command/AddComputed.hs b/Command/AddComputed.hs
index 071015e014..20eacf954f 100644
--- a/Command/AddComputed.hs
+++ b/Command/AddComputed.hs
@@ -28,7 +28,7 @@ import qualified Data.Map as M
 import Data.Time.Clock
 
 cmd :: Command
-cmd = notBareRepo $ 
+cmd = notBareRepo $ withAnnexOptions [backendOption] $
 	command "addcomputed" SectionCommon "add computed files to annex"
 		(paramRepeating paramExpression)
 		(seek <$$> optParser)
@@ -96,11 +96,22 @@ perform o r = do
 	Remote.Compute.runComputeProgram program state
 		(Remote.Compute.ImmutableState False)
 		(getInputContent fast)
-		(addComputed "adding" True r (reproducible o) Just fast)
+		(addComputed "adding" True r (reproducible o) chooseBackend Just fast)
 	next $ return True
 
-addComputed :: StringContainingQuotedPath -> Bool -> Remote -> Maybe Reproducible -> (OsPath -> Maybe OsPath) -> Bool -> Remote.Compute.ComputeState -> OsPath -> NominalDiffTime -> Annex ()
-addComputed addaction stagefiles r reproducibleconfig destfile fast state tmpdir ts = do
+addComputed
+	:: StringContainingQuotedPath
+	-> Bool
+	-> Remote
+	-> Maybe Reproducible
+	-> (OsPath -> Annex Backend)
+	-> (OsPath -> Maybe OsPath)
+	-> Bool
+	-> Remote.Compute.ComputeState
+	-> OsPath
+	-> NominalDiffTime
+	-> Annex ()
+addComputed addaction stagefiles r reproducibleconfig choosebackend destfile fast state tmpdir ts = do
 	let outputs = Remote.Compute.computeOutputs state
 	when (M.null outputs) $
 		giveup "The computation succeeded, but it did not generate any files."
@@ -146,22 +157,24 @@ addComputed addaction stagefiles r reproducibleconfig destfile fast state tmpdir
 			, contentLocation = outputfile'
 			, inodeCache = Nothing
 			}
+		genkey f p = do
+			backend <- choosebackend outputfile
+			fst <$> genKey (ks f) p backend
+		makelink f k = void $ makeLink f k Nothing
+		ingesthelper f p mk
+			| stagefiles = ingestwith $ do
+				k <- maybe (genkey f p) return mk
+				ingestAdd' p (Just (ld f)) (Just k)
+			| otherwise = ingestwith $ do
+				k <- maybe (genkey f p) return mk
+				mk' <- fst <$> ingest p (Just (ld f)) (Just k)
+				maybe noop (makelink f) mk'
+				return mk'
 		ingestwith a = a >>= \case
 			Nothing -> giveup "ingestion failed"
 			Just k -> do
 				logStatus NoLiveUpdate k InfoPresent
 				return k
-		genkey f p = do
-			backend <- chooseBackend outputfile
-			fst <$> genKey (ks f) p backend
-		makelink f k = void $ makeLink f k Nothing
-		ingesthelper f p mk
-			| stagefiles = ingestwith $
-				ingestAdd' p (Just (ld f)) mk
-			| otherwise = ingestwith $ do
-				mk' <- fst <$> ingest p (Just (ld f)) mk
-				maybe noop (makelink f) mk'
-				return mk'
 	
 	ldc = LockDownConfig
 		{ lockingFile = True
diff --git a/Command/Recompute.hs b/Command/Recompute.hs
index 2193216d29..4a3c8355ad 100644
--- a/Command/Recompute.hs
+++ b/Command/Recompute.hs
@@ -14,10 +14,13 @@ import qualified Annex
 import qualified Remote.Compute
 import qualified Remote
 import qualified Types.Remote as Remote
+import Annex.Content
 import Annex.CatFile
 import Git.FilePath
 import Logs.Location
 import Command.AddComputed (Reproducible(..), parseReproducible, getInputContent, getInputContent', addComputed)
+import Backend (maybeLookupBackendVariety, unknownBackendVarietyMessage)
+import Types.Key
 
 import qualified Data.Map as M
 
@@ -62,7 +65,7 @@ seek' o = do
 
 start :: RecomputeOptions -> Maybe Remote -> SeekInput -> OsPath -> Key -> CommandStart
 start o (Just computeremote) si file key = 
-	stopUnless (notElem (Remote.uuid computeremote) <$> loggedLocations key) $
+	stopUnless (elem (Remote.uuid computeremote) <$> loggedLocations key) $
 		start' o computeremote si file key		
 start o Nothing si file key = do
 	rs <- catMaybes <$> (mapM Remote.byUUID =<< loggedLocations key)
@@ -103,31 +106,73 @@ start' o r si file key =
 			-- explains the problem.
 			Nothing -> True
 
--- TODO When reproducible is not set, preserve the
--- reproducible/unreproducible of the input key.
 perform :: RecomputeOptions -> Remote -> OsPath -> Key -> Remote.Compute.ComputeState -> CommandPerform
-perform o r file key origstate = do
+perform o r file origkey origstate = do
 	program <- Remote.Compute.getComputeProgram r
-	fast <- Annex.getRead Annex.fast
+	reproducibleconfig <- getreproducibleconfig
 	showOutput
 	Remote.Compute.runComputeProgram program origstate
-		(Remote.Compute.ImmutableState True)
-		(getinputcontent program fast)
-		(addComputed "processing" False r (reproducible o) destfile fast)
+		(Remote.Compute.ImmutableState False)
+		(getinputcontent program)
+		(go program reproducibleconfig)
 	next $ return True
   where
-	getinputcontent program fast p
+	go program reproducibleconfig state tmpdir ts = do
+		checkbehaviorchange program state
+		addComputed "processing" False r reproducibleconfig
+			choosebackend destfile state tmpdir ts
+
+	checkbehaviorchange program state = do
+		let check s w a b = forM_ (M.keys (w a)) $ \f ->
+			unless (M.member f (w b)) $
+				Remote.Compute.computationBehaviorChangeError program s f
+		
+		check "not using input file"
+			Remote.Compute.computeInputs origstate state
+		check "outputting"
+			Remote.Compute.computeOutputs state origstate
+		check "not outputting"
+			Remote.Compute.computeOutputs origstate state
+
+	getinputcontent program p
 		| originalOption o =
 			case M.lookup p (Remote.Compute.computeInputs origstate) of
-				Just inputkey -> getInputContent' fast inputkey
+				Just inputkey -> getInputContent' False inputkey
 					(fromOsPath p ++ "(key " ++ serializeKey inputkey ++ ")")
 				Nothing -> Remote.Compute.computationBehaviorChangeError program
 					"requesting a new input file" p
-		| otherwise = getInputContent fast p
+		| otherwise = getInputContent False p
 	
 	destfile outputfile
 		| Just outputfile == origfile = Just file
 		| otherwise = Nothing
 	
-	origfile = headMaybe $ M.keys $ M.filter (== Just key)
+	origfile = headMaybe $ M.keys $ M.filter (== Just origkey)
 		(Remote.Compute.computeOutputs origstate)
+
+	origbackendvariety = fromKey keyVariety origkey
+	
+	getreproducibleconfig = case reproducible o of
+		Just (Reproducible True) -> return (Just (Reproducible True))
+		-- A VURL key is used when the computation was
+		-- unreproducible. So recomputing should too, but that
+		-- will result in the same VURL key. Since moveAnnex
+		-- will prefer the current annex object to a new one,
+		-- delete the annex object first, so that if recomputing
+		-- generates a new version of the file, it replaces
+		-- the old version.
+		v -> case origbackendvariety of
+			VURLKey -> do
+				lockContentForRemoval origkey noop removeAnnex
+				-- in case computation fails or is interupted
+				logStatus NoLiveUpdate origkey InfoMissing
+				return (Just (Reproducible False))
+			_ -> return v
+
+	choosebackend _outputfile
+		-- Use the same backend as was used to compute it before,
+		-- so if the computed file is the same, there will be
+		-- no change.
+		| otherwise = maybeLookupBackendVariety origbackendvariety >>= \case
+			Just b -> return b
+			Nothing -> giveup $ unknownBackendVarietyMessage origbackendvariety
diff --git a/Remote/Compute.hs b/Remote/Compute.hs
index e3ec2a8fdd..a8a3cdd32e 100644
--- a/Remote/Compute.hs
+++ b/Remote/Compute.hs
@@ -399,8 +399,8 @@ runComputeProgram (ComputeProgram program) state (ImmutableState immutablestate)
 				liftIO $ hPutStrLn (stdinHandle p) $
 					maybe "" fromOsPath mp'
 				liftIO $ hFlush (stdinHandle p)
-				return $ if knowninput
-					then state'
+				return $ if immutablestate
+					then state
 					else state'
 						{ computeInputs = 
 							M.insert f' k
@@ -411,8 +411,8 @@ runComputeProgram (ComputeProgram program) state (ImmutableState immutablestate)
 			checksafefile tmpdir subdir f' "output"
 			let knownoutput = M.member f' (computeOutputs state')
 			checkimmutable knownoutput "outputting" f' $ 
-				return $ if knownoutput
-					then state'
+				return $ if immutablestate
+					then state
 					else state'
 						{ computeOutputs = 
 							M.insert f' Nothing
diff --git a/TODO-compute b/TODO-compute
index 31d8aaa7b2..fe128b0e4d 100644
--- a/TODO-compute
+++ b/TODO-compute
@@ -1,3 +1,20 @@
+* VURL keys don't currently have the hash key recorded in the equivilant
+  key log by addcompute or when getting from a compute remote.
+
+* need progress bars for computations and implement PROGRESS message
+
+* get input files for a computation (so `git-annex get .` gets every file,
+  even when input files in a directory are processed after computed files)
+
+* autoinit security
+
+* Support non-annexed files as inputs to computations.
+
+* addcomputed should honor annex.addunlocked.
+
+* Perhaps recompute should write a new version of a file as an unlocked
+  file when the file is currently unlocked?
+
 * recompute could ingest keys for other files than the one being
   recomputed, and remember them. Then recomputing those files could just
   use those keys, without re-running a computation. (Better than --others
@@ -18,18 +35,6 @@
   Or it could build a DAG and traverse it, but building a DAG of a large
   directory tree has its own problems.
 
-* recompute should use the same key backend for a file that it used before
-  (except when --reproducible/--unreproducible is passed).
-
-* Check recompute's handling of --reproducible and --unreproducible.
-
-* addcomputed should honor annex.addunlocked.
-
-* Perhaps recompute should write a new version of a file as an unlocked
-  file when the file is currently unlocked?
-
-* Support non-annexed files as inputs to computations.
-
 * Should addcomputed honor annex.smallfiles? That would seem to imply
   that recompute should also support recomputing non-annexed files.
   Otherwise, adding a file and then recomputing it would vary in
diff --git a/doc/git-annex-addcomputed.mdwn b/doc/git-annex-addcomputed.mdwn
index 58261da181..3301381c66 100644
--- a/doc/git-annex-addcomputed.mdwn
+++ b/doc/git-annex-addcomputed.mdwn
@@ -82,6 +82,10 @@ the parameters provided to `git-annex addcomputed`.
   checksum verification error. One thing that can be done then is to use 
   `git-annex recompute --original --unreproducible`.
 
+* `--backend`
+
+  Specifies which key-value backend to use.
+
 *  Also the [[git-annex-common-options]](1) can be used.
 
 # SEE ALSO
diff --git a/doc/git-annex-recompute.mdwn b/doc/git-annex-recompute.mdwn
index b65488bae8..fb895aa75c 100644
--- a/doc/git-annex-recompute.mdwn
+++ b/doc/git-annex-recompute.mdwn
@@ -21,17 +21,7 @@ updated with the new content.
 
 * `--original`
 
-  Use the original content of input files.
-
-* `--unreproducible`, `-u`
-
-  Convert files that were added with `git-annex addcomputed --reproducible`
-  to be as if they were added without that option.
-
-* `--reproducible`, `-r`
-
-  Convert files that were added with `git-annex addcomputed --unreproducible`
-  to be as if they were added with `--reproducible`.
+  Re-run the computation with the original input files.
 
 * `--remote=name`
 
@@ -42,6 +32,22 @@ updated with the new content.
   a file can be computed by multiple remotes, the one with the lowest
   configured cost will be used.
 
+* `--unreproducible`, `-u`
+
+  Indicate that the computation is not expected to be fully reproducible.
+  It can vary, in ways that produce files that equivilant enough to
+  be interchangeable, but are not necessarily identical.
+
+  This is the default unless the compute remote indicates that it produces
+  reproducible output.
+
+* `--reproducible`, `-r`
+
+  Indicate that the computation is expected to be fully reproducible.
+
+  This is the default when the compute remote indicates that it produces
+  reproducible output.
+
 * matching options
 
   The [[git-annex-matching-options]](1) can be used to control what