diff --git a/core/bootstrap/compiler/compiler.factor b/core/bootstrap/compiler/compiler.factor
index ff9d5c5e1e..2b278ac458 100755
--- a/core/bootstrap/compiler/compiler.factor
+++ b/core/bootstrap/compiler/compiler.factor
@@ -77,3 +77,14 @@ nl
 [ compiled-usages recompile ] recompile-hook set-global
 
 " done" print flush
+
+! Load empty test vocabs
+USE: compiler.test.curry
+USE: compiler.test.float
+USE: compiler.test.intrinsics
+USE: compiler.test.redefine
+USE: compiler.test.simple
+USE: compiler.test.stack-trace
+USE: compiler.test.templates
+USE: compiler.test.templates-early
+USE: compiler.test.tuples
diff --git a/core/classes/classes.factor b/core/classes/classes.factor
index 151429bf69..345676e106 100755
--- a/core/classes/classes.factor
+++ b/core/classes/classes.factor
@@ -20,7 +20,9 @@ PREDICATE: class tuple-class
 
 : classes ( -- seq ) class<map get keys ;
 
-: type>class ( n -- class ) builtins get nth ;
+: type>class ( n -- class ) builtins get-global nth ;
+
+: bootstrap-type>class ( n -- class ) builtins get nth ;
 
 : predicate-word ( word -- predicate )
     [ word-name "?" append ] keep word-vocabulary create ;
diff --git a/core/compiler/compiler-tests.factor b/core/compiler/compiler-tests.factor
deleted file mode 100755
index 7e4e79437d..0000000000
--- a/core/compiler/compiler-tests.factor
+++ /dev/null
@@ -1,7 +0,0 @@
-IN: temporary
-USING: tools.browser tools.test kernel sequences vocabs ;
-
-"compiler.test" child-vocabs empty? [
-    "compiler.test" load-children
-    "compiler.test" test
-] when
diff --git a/core/compiler/test/simple/simple-tests.factor b/core/compiler/test/simple/simple-tests.factor
index 3f4f6451a3..743fb713d9 100755
--- a/core/compiler/test/simple/simple-tests.factor
+++ b/core/compiler/test/simple/simple-tests.factor
@@ -1,6 +1,6 @@
 USING: compiler tools.test kernel kernel.private
 combinators.private math.private math combinators strings
-alien arrays ;
+alien arrays memory ;
 IN: temporary
 
 ! Test empty word
@@ -48,6 +48,8 @@ IN: temporary
 [ 4 1 3 ] [ 0 [ { [ bar 1 ] [ 3 1 ] } dispatch 3 ] compile-call ] unit-test
 [ 3 1 3 ] [ 1 [ { [ bar 1 ] [ 3 1 ] } dispatch 3 ] compile-call ] unit-test
 
+[ 2 3 ] [ 1 [ { [ code-gc 1 ] [ code-gc 2 ] } dispatch 3 ] compile-call ] unit-test
+
 ! Labels
 
 : recursive ( ? -- ) [ f recursive ] when ; inline
diff --git a/core/cpu/architecture/architecture.factor b/core/cpu/architecture/architecture.factor
index 4da22ff38a..4bb10b23a2 100755
--- a/core/cpu/architecture/architecture.factor
+++ b/core/cpu/architecture/architecture.factor
@@ -60,9 +60,7 @@ HOOK: %jump-label compiler-backend ( label -- )
 ! Test if vreg is 'f' or not
 HOOK: %jump-t compiler-backend ( label -- )
 
-HOOK: %call-dispatch compiler-backend ( -- label )
-
-HOOK: %jump-dispatch compiler-backend ( -- )
+HOOK: %dispatch compiler-backend ( -- )
 
 HOOK: %dispatch-label compiler-backend ( word -- )
 
diff --git a/core/cpu/ppc/architecture/architecture.factor b/core/cpu/ppc/architecture/architecture.factor
index 7444c21a8c..1daf3ac622 100755
--- a/core/cpu/ppc/architecture/architecture.factor
+++ b/core/cpu/ppc/architecture/architecture.factor
@@ -111,20 +111,15 @@ M: ppc-backend %jump-label ( label -- ) B ;
 M: ppc-backend %jump-t ( label -- )
     0 "flag" operand f v>operand CMPI BNE ;
 
-: (%dispatch) ( len -- )
-    0 11 LOAD32 rc-absolute-ppc-2/2 rel-here
-    "offset" operand "n" operand 1 SRAWI
-    11 11 "offset" operand ADD
-    11 dup rot cells LWZ ;
-
-M: ppc-backend %call-dispatch ( word-table# -- )
-    [ 7 (%dispatch) (%call) <label> dup B ] H{
-        { +input+ { { f "n" } } }
-        { +scratch+ { { f "offset" } } }
-    } with-template ;
-
-M: ppc-backend %jump-dispatch ( -- )
-    [ %epilogue-later 6 (%dispatch) (%jump) ] H{
+M: ppc-backend %dispatch ( -- )
+    [
+        %epilogue-later
+        0 11 LOAD32 rc-absolute-ppc-2/2 rel-here
+        "offset" operand "n" operand 1 SRAWI
+        11 11 "offset" operand ADD
+        11 dup 6 cells LWZ
+        (%jump)
+    ] H{
         { +input+ { { f "n" } } }
         { +scratch+ { { f "offset" } } }
     } with-template ;
diff --git a/core/cpu/x86/architecture/architecture.factor b/core/cpu/x86/architecture/architecture.factor
index 8c5d5c1dc0..20564bbde3 100755
--- a/core/cpu/x86/architecture/architecture.factor
+++ b/core/cpu/x86/architecture/architecture.factor
@@ -77,26 +77,29 @@ M: x86-backend %jump-label ( label -- ) JMP ;
 M: x86-backend %jump-t ( label -- )
     "flag" operand f v>operand CMP JNE ;
 
-: (%dispatch) ( n -- operand )
-    ! Load jump table base. We use a temporary register
-    ! since on AMD64 we have to load a 64-bit immediate. On
-    ! x86, this is redundant.
-    ! Untag and multiply to get a jump table offset
-    "n" operand fixnum>slot@
-    ! Add jump table base
-    "offset" operand HEX: ffffffff MOV rc-absolute-cell rel-here
-    "n" operand "offset" operand ADD
-    "n" operand swap bootstrap-cell 8 = 14 9 ? + [+] ;
+: code-alignment ( -- n )
+    building get length dup cell align swap - ;
 
-M: x86-backend %call-dispatch ( word-table# -- )
-    [ 5 (%dispatch) CALL <label> dup JMP ] H{
-        { +input+ { { f "n" } } }
-        { +scratch+ { { f "offset" } } }
-        { +clobber+ { "n" } }
-    } with-template ;
+: align-code ( n -- )
+    0 <repetition> % ;
 
-M: x86-backend %jump-dispatch ( -- )
-    [ %epilogue-later 0 (%dispatch) JMP ] H{
+M: x86-backend %dispatch ( -- )
+    [
+        %epilogue-later
+        ! Load jump table base. We use a temporary register
+        ! since on AMD64 we have to load a 64-bit immediate. On
+        ! x86, this is redundant.
+        ! Untag and multiply to get a jump table offset
+        "n" operand fixnum>slot@
+        ! Add jump table base
+        "offset" operand HEX: ffffffff MOV rc-absolute-cell rel-here
+        "n" operand "offset" operand ADD
+        "n" operand HEX: 7f [+] JMP
+        ! Fix up the displacement above
+        code-alignment dup bootstrap-cell 8 = 14 9 ? +
+        building get dup pop* push
+        align-code
+    ] H{
         { +input+ { { f "n" } } }
         { +scratch+ { { f "offset" } } }
         { +clobber+ { "n" } }
diff --git a/core/generator/generator.factor b/core/generator/generator.factor
index 3883fb6e35..d8164fdce7 100755
--- a/core/generator/generator.factor
+++ b/core/generator/generator.factor
@@ -56,13 +56,16 @@ GENERIC: generate-node ( node -- next )
 : generate-nodes ( node -- )
     [ node@ generate-node ] iterate-nodes end-basic-block ;
 
+: init-generate-nodes ( -- )
+    init-templates
+    %save-word-xt
+    %prologue-later
+    current-label-start define-label
+    current-label-start resolve-label ;
+    
 : generate ( word label node -- )
     [
-        init-templates
-        %save-word-xt
-        %prologue-later
-        current-label-start define-label
-        current-label-start resolve-label
+        init-generate-nodes
         [ generate-nodes ] with-node-iterator
     ] generate-1 ;
 
@@ -168,17 +171,23 @@ M: #if generate-node
         ] if %dispatch-label
     ] each ;
 
+: generate-dispatch ( node -- )
+    %dispatch dispatch-branches init-templates ;
+
 M: #dispatch generate-node
     #! The order here is important, dispatch-branches must
     #! run after %dispatch, so that each branch gets the
     #! correct register state
     tail-call? [
-        %jump-dispatch dispatch-branches
+        generate-dispatch iterate-next
     ] [
-        0 frame-required
-        %call-dispatch >r dispatch-branches r> resolve-label
-    ] if
-    init-templates iterate-next ;
+        compiling-word get gensym [
+            rot [
+                init-generate-nodes
+                generate-dispatch
+            ] generate-1
+        ] keep generate-call
+    ] if ;
 
 ! #call
 : define-intrinsics ( word intrinsics -- )
diff --git a/core/generic/math/math.factor b/core/generic/math/math.factor
index 8cf83b0ba7..21a7857646 100755
--- a/core/generic/math/math.factor
+++ b/core/generic/math/math.factor
@@ -61,7 +61,7 @@ TUPLE: no-math-method left right generic ;
 : math-vtable* ( picker max quot -- quot )
     [
         rot , \ tag ,
-        [ >r [ type>class ] map r> map % ] { } make ,
+        [ >r [ bootstrap-type>class ] map r> map % ] { } make ,
         \ dispatch ,
     ] [ ] make ; inline
 
diff --git a/core/generic/standard/standard.factor b/core/generic/standard/standard.factor
index 88f6a05bc2..7f4f423d8b 100755
--- a/core/generic/standard/standard.factor
+++ b/core/generic/standard/standard.factor
@@ -97,7 +97,7 @@ TUPLE: no-method object generic ;
     [ small-generic ] picker class-hash-dispatch-quot ;
 
 : vtable-class ( n -- class )
-    type>class [ hi-tag bootstrap-word ] unless* ;
+    bootstrap-type>class [ hi-tag bootstrap-word ] unless* ;
 
 : group-methods ( assoc -- vtable )
     #! Input is a predicate -> method association.
diff --git a/core/inference/inference-tests.factor b/core/inference/inference-tests.factor
index c5bc3b5fda..2691be8c3a 100755
--- a/core/inference/inference-tests.factor
+++ b/core/inference/inference-tests.factor
@@ -4,7 +4,8 @@ math.parser math.private namespaces namespaces.private parser
 sequences strings vectors words quotations effects tools.test
 continuations generic.standard sorting assocs definitions
 prettyprint io inspector tuples classes.union classes.predicate
-debugger threads.private io.streams.string combinators.private ;
+debugger threads.private io.streams.string io.timeouts
+combinators.private ;
 IN: temporary
 
 { 0 2 } [ 2 "Hello" ] must-infer-as
diff --git a/core/io/io-docs.factor b/core/io/io-docs.factor
index 208e2a2ba7..9c73a3b2b1 100755
--- a/core/io/io-docs.factor
+++ b/core/io/io-docs.factor
@@ -22,8 +22,7 @@ $nl
 { $subsection make-block-stream }
 { $subsection make-cell-stream }
 { $subsection stream-write-table }
-"Optional word for network streams:"
-{ $subsection set-timeout } ;
+{ $see-also "io.timeouts" } ;
 
 ARTICLE: "stdio" "The default stream"
 "Various words take an implicit stream parameter from a variable to reduce stack shuffling."
@@ -73,11 +72,6 @@ ARTICLE: "streams" "Streams"
 
 ABOUT: "streams"
 
-HELP: set-timeout
-{ $values { "n" "an integer" } { "stream" "a stream" } }
-{ $contract "Sets a timeout, in milliseconds, for input and output operations on the stream. If a read or a write is initiated and no activity is seen before the timeout expires, an error will be thrown to the caller of the operation being performed." }
-{ $notes "Whether or not the stream is closed when the error is thrown is implementation-specific, and user code should take care to close the stream on all error conditions in any case." } ;
-
 HELP: stream-readln
 { $values { "stream" "an input stream" } { "str" string } }
 { $contract "Reads a line of input from the stream. Outputs " { $link f } " on stream exhaustion." }
diff --git a/core/io/io.factor b/core/io/io.factor
index e0c890c0e3..2d927d088a 100755
--- a/core/io/io.factor
+++ b/core/io/io.factor
@@ -4,7 +4,6 @@ USING: hashtables generic kernel math namespaces sequences strings
     continuations assocs io.styles sbufs ;
 IN: io
 
-GENERIC: set-timeout ( n stream -- )
 GENERIC: stream-readln ( stream -- str )
 GENERIC: stream-read1 ( stream -- ch/f )
 GENERIC: stream-read ( n stream -- str/f )
diff --git a/core/io/streams/duplex/duplex.factor b/core/io/streams/duplex/duplex.factor
index 86660b2752..97e60b4a60 100755
--- a/core/io/streams/duplex/duplex.factor
+++ b/core/io/streams/duplex/duplex.factor
@@ -74,8 +74,3 @@ M: duplex-stream dispose
         [ dup duplex-stream-out dispose ]
         [ dup duplex-stream-in dispose ] [ ] cleanup
     ] unless drop ;
-
-M: duplex-stream set-timeout
-    2dup
-    duplex-stream-in set-timeout
-    duplex-stream-out set-timeout ;
diff --git a/extra/cocoa/cocoa.factor b/extra/cocoa/cocoa.factor
index cbc6c9d762..c94984f00b 100755
--- a/extra/cocoa/cocoa.factor
+++ b/extra/cocoa/cocoa.factor
@@ -58,6 +58,7 @@ SYMBOL: super-sent-messages
         "NSPasteboard"
         "NSResponder"
         "NSSavePanel"
+        "NSScreen"
         "NSView"
         "NSWindow"
         "NSWorkspace"
diff --git a/extra/concurrency/concurrency-tests.factor b/extra/concurrency/concurrency-tests.factor
index 1a19ce7096..8908506d51 100755
--- a/extra/concurrency/concurrency-tests.factor
+++ b/extra/concurrency/concurrency-tests.factor
@@ -133,4 +133,9 @@ SYMBOL: value
 [ 3 3 ] [
     [ 3 ] future
     dup ?future swap ?future
+] unit-test
+
+! Another race
+[ 3 ] [
+    [ 3 yield ] future ?future
 ] unit-test
\ No newline at end of file
diff --git a/extra/concurrency/concurrency.factor b/extra/concurrency/concurrency.factor
index a8e0bc6eeb..1c5f6322a8 100755
--- a/extra/concurrency/concurrency.factor
+++ b/extra/concurrency/concurrency.factor
@@ -273,14 +273,14 @@ TUPLE: future value processes ;
 
 : future ( quot -- future )
     #! Spawn a process to call the quotation and immediately return.
-    \ future construct-empty [
+    f V{ } clone \ future construct-boa [
         [
             >r [ t 2array ] compose [ f 2array ] recover r>
             notify-future
         ] 2curry spawn drop
     ] keep ;
- 
- : ?future ( future -- result )
+
+: ?future ( future -- result )
     #! Block the process until the future has completed and then
     #! place the result on the stack. Return the result
     #! immediately if the future has completed.
diff --git a/extra/delegate/protocols/protocols.factor b/extra/delegate/protocols/protocols.factor
index 1121883b7c..37f3812d2d 100755
--- a/extra/delegate/protocols/protocols.factor
+++ b/extra/delegate/protocols/protocols.factor
@@ -18,7 +18,7 @@ PROTOCOL: stream-protocol
     stream-read1 stream-read stream-read-until
     stream-flush stream-write1 stream-write stream-format
     stream-nl make-span-stream make-block-stream stream-readln
-    make-cell-stream stream-write-table set-timeout ;
+    make-cell-stream stream-write-table ;
 
 PROTOCOL: definition-protocol
     where set-where forget uses redefined*
diff --git a/extra/help/handbook/handbook.factor b/extra/help/handbook/handbook.factor
index d6b4ec7ffe..9472e1f519 100755
--- a/extra/help/handbook/handbook.factor
+++ b/extra/help/handbook/handbook.factor
@@ -157,7 +157,8 @@ ARTICLE: "io" "Input and output"
 "Advanced features:"
 { $subsection "io.launcher" }
 { $subsection "io.mmap" }
-{ $subsection "io.monitors" } ;
+{ $subsection "io.monitors" }
+{ $subsection "io.timeouts" } ;
 
 ARTICLE: "tools" "Developer tools"
 { $subsection "tools.annotations" }
diff --git a/extra/http/client/client.factor b/extra/http/client/client.factor
index 109bf17c40..679d603708 100755
--- a/extra/http/client/client.factor
+++ b/extra/http/client/client.factor
@@ -1,8 +1,8 @@
 ! Copyright (C) 2005, 2007 Slava Pestov.
 ! See http://factorcode.org/license.txt for BSD license.
 USING: assocs http kernel math math.parser namespaces sequences
-io io.sockets io.streams.string io.files strings splitting
-continuations assocs.lib ;
+io io.sockets io.streams.string io.files io.timeouts strings
+splitting continuations assocs.lib ;
 IN: http.client
 
 : parse-host ( url -- host port )
diff --git a/extra/http/server/server.factor b/extra/http/server/server.factor
index eca2253e2a..957a82d09f 100755
--- a/extra/http/server/server.factor
+++ b/extra/http/server/server.factor
@@ -1,6 +1,6 @@
 ! Copyright (C) 2003, 2008 Slava Pestov.
 ! See http://factorcode.org/license.txt for BSD license.
-USING: assocs kernel namespaces io strings splitting
+USING: assocs kernel namespaces io io.timeouts strings splitting
 threads http http.server.responders sequences prettyprint
 io.server logging ;
 
diff --git a/extra/io/launcher/launcher-docs.factor b/extra/io/launcher/launcher-docs.factor
index e414d98d65..4f5a85244b 100755
--- a/extra/io/launcher/launcher-docs.factor
+++ b/extra/io/launcher/launcher-docs.factor
@@ -76,6 +76,9 @@ HELP: +append-environment+
 $nl
 "This is used in situations where you want a spawn child process with some overridden environment variables." } ;
 
+HELP: +timeout+
+{ $description "Launch descriptor key. If set, specifies a maximum running time for the process. If the process runs longer than this time, it will be killed." } ;
+
 HELP: default-descriptor
 { $description "Association storing default values for launch descriptor keys." } ;
 
@@ -94,22 +97,16 @@ HELP: run-process*
 
 HELP: >descriptor
 { $values { "desc" "a launch descriptor" } { "desc" "a launch descriptor" } }
-{ $description "Creates a launch descriptor from an object, which must be one of the following:"
-    { $list
-        { "a string -- this is wrapped in a launch descriptor with a single " { $link +command+ } " key" }
-        { "a sequence of strings -- this is wrapped in a launch descriptor with a single " { $link +arguments+ } " key" }
-        { "an association, used to set launch parameters for additional control" }
-    }
-} ;
+{ $description "Creates a launch descriptor from an object. See " { $link "io.launcher.descriptors" } " for details." } ;
 
 HELP: run-process
 { $values { "desc" "a launch descriptor" } { "process" process } }
-{ $description "Launches a process. The object can either be a string, a sequence of strings or a launch descriptor. See " { $link >descriptor } " for details." }
+{ $description "Launches a process. The object can either be a string, a sequence of strings or a launch descriptor. See " { $link "io.launcher.descriptors" } " for details." }
 { $notes "The output value can be passed to " { $link wait-for-process } " to get an exit code." } ;
 
 HELP: run-detached
 { $values { "desc" "a launch descriptor" } { "process" process } }
-{ $contract "Launches a process without waiting for it to complete. The object can either be a string, a sequence of strings or a launch descriptor. See " { $link >descriptor } " for details." }
+{ $contract "Launches a process without waiting for it to complete. The object can either be a string, a sequence of strings or a launch descriptor. See " { $link "io.launcher.descriptors" } " for details." }
 { $notes
     "This word is functionally identical to passing a launch descriptor to " { $link run-process } " having the " { $link +detached+ } " key set."
     $nl
@@ -162,25 +159,27 @@ HELP: wait-for-process
 { $values { "process" process } { "status" integer } }
 { $description "If the process is still running, waits for it to exit, otherwise outputs the exit code immediately. Can be called multiple times on the same process." } ;
 
-ARTICLE: "io.launcher" "Launching OS processes"
-"The " { $vocab-link "io.launcher" } " vocabulary implements cross-platform process launching."
-$nl
-"Words which launch processes can take either a command line string, a sequence of command line arguments, or a launch descriptor:"
+ARTICLE: "io.launcher.descriptors" "Launch descriptors"
+"Words which launch processes can take either a command line string, a sequence of command line arguments, or an assoc:"
 { $list
-    { "strings are wrapped in a launch descriptor with a single " { $link +command+ } " key" }
-    { "sequences of strings are wrapped in a launch descriptor with a single " { $link +arguments+ } " key" }
-    { "launch descriptors are associations, which can set extra launch parameters for finer control" }
+    { "strings are wrapped in an assoc with a single " { $link +command+ } " key" }
+    { "sequences of strings are wrapped in an assoc with a single " { $link +arguments+ } " key" }
+    { "associations can be passed in, which allows finer control over launch parameters" }
 }
-"A launch descriptor is an association containing keys from the below set:"
+"The associations can contain the following keys:"
 { $subsection +command+ }
 { $subsection +arguments+ }
 { $subsection +detached+ }
 { $subsection +environment+ }
 { $subsection +environment-mode+ }
-"Redirecting standard input and output to files:"
+{ $subsection +timeout+ }
 { $subsection +stdin+ }
 { $subsection +stdout+ }
-{ $subsection +stderr+ }
+{ $subsection +stderr+ } ;
+
+ARTICLE: "io.launcher" "Launching OS processes"
+"The " { $vocab-link "io.launcher" } " vocabulary implements cross-platform process launching."
+{ $subsection "io.launcher.descriptors" }
 "The following words are used to launch processes:"
 { $subsection run-process }
 { $subsection run-detached }
@@ -193,6 +192,7 @@ $nl
 "A class representing an active or finished process:"
 { $subsection process }
 "Waiting for a process to end, or getting the exit code of a finished process:"
-{ $subsection wait-for-process } ;
+{ $subsection wait-for-process }
+"Processes support the " { $link "io.timeouts" } "; the timeout specifies an upper bound on the running time of the process." ;
 
 ABOUT: "io.launcher"
diff --git a/extra/io/launcher/launcher.factor b/extra/io/launcher/launcher.factor
index 3f0df4ed18..cbece818c9 100755
--- a/extra/io/launcher/launcher.factor
+++ b/extra/io/launcher/launcher.factor
@@ -1,8 +1,8 @@
 ! Copyright (C) 2008 Slava Pestov.
 ! See http://factorcode.org/license.txt for BSD license.
-USING: io io.backend system kernel namespaces strings hashtables
-sequences assocs combinators vocabs.loader init threads
-continuations math ;
+USING: io io.backend io.timeouts system kernel namespaces
+strings hashtables sequences assocs combinators vocabs.loader
+init threads continuations math ;
 IN: io.launcher
 
 ! Non-blocking process exit notification facility
@@ -10,14 +10,14 @@ SYMBOL: processes
 
 [ H{ } clone processes set-global ] "io.launcher" add-init-hook
 
-TUPLE: process handle status ;
+TUPLE: process handle status killed? lapse ;
 
 HOOK: register-process io-backend ( process -- )
 
 M: object register-process drop ;
 
 : <process> ( handle -- process )
-    f process construct-boa
+    f f <lapse> process construct-boa
     V{ } clone over processes get set-at
     dup register-process ;
 
@@ -25,6 +25,8 @@ M: process equal? 2drop f ;
 
 M: process hashcode* process-handle hashcode* ;
 
+: process-running? ( process -- ? ) process-status not ;
+
 SYMBOL: +command+
 SYMBOL: +arguments+
 SYMBOL: +detached+
@@ -34,6 +36,7 @@ SYMBOL: +stdin+
 SYMBOL: +stdout+
 SYMBOL: +stderr+
 SYMBOL: +closed+
+SYMBOL: +timeout+
 
 SYMBOL: +prepend-environment+
 SYMBOL: +replace-environment+
@@ -63,22 +66,30 @@ SYMBOL: +append-environment+
         { +replace-environment+ [ ] }
     } case ;
 
-GENERIC: >descriptor ( desc -- desc )
+: string-array? ( obj -- ? )
+    dup sequence? [ [ string? ] all? ] [ drop f ] if ;
 
-M: string >descriptor +command+ associate ;
-M: sequence >descriptor +arguments+ associate ;
-M: assoc >descriptor >hashtable ;
+: >descriptor ( desc -- desc )
+    {
+        { [ dup string? ] [ +command+ associate ] }
+        { [ dup string-array? ] [ +arguments+ associate ] }
+        { [ dup assoc? ] [ >hashtable ] }
+    } cond ;
 
 HOOK: run-process* io-backend ( desc -- handle )
 
 : wait-for-process ( process -- status )
-    dup process-handle [
-        dup [ processes get at push stop ] curry callcc0
-    ] when process-status ;
+    [
+        dup process-handle
+        [ dup [ processes get at push stop ] curry callcc0 ] when
+        dup process-killed?
+        [ "Process was killed" throw ] [ process-status ] if
+    ] with-timeout ;
 
 : run-process ( desc -- process )
     >descriptor
     dup run-process*
+    +timeout+ pick at [ over set-timeout ] when*
     +detached+ rot at [ dup wait-for-process drop ] unless ;
 
 : run-detached ( desc -- process )
@@ -96,8 +107,13 @@ TUPLE: process-failed code ;
 HOOK: kill-process* io-backend ( handle -- )
 
 : kill-process ( process -- )
+    t over set-process-killed?
     process-handle [ kill-process* ] when* ;
 
+M: process get-lapse process-lapse ;
+
+M: process timed-out kill-process ;
+
 HOOK: process-stream* io-backend ( desc -- stream process )
 
 TUPLE: process-stream process ;
diff --git a/extra/io/nonblocking/nonblocking-docs.factor b/extra/io/nonblocking/nonblocking-docs.factor
index af73a47030..d8d2cf5479 100755
--- a/extra/io/nonblocking/nonblocking-docs.factor
+++ b/extra/io/nonblocking/nonblocking-docs.factor
@@ -38,8 +38,6 @@ $nl
 { $list
     { { $link port-handle } " - a native handle identifying the underlying native resource used by the port" }
     { { $link port-error } " - the most recent I/O error, if any. This error is thrown to the waiting thread when " { $link pending-error } " is called by stream operations" }
-    { { $link port-timeout } " - a timeout, specifying the maximum length of time, in milliseconds, for which input operations can block before throwing an error. A value of 0 denotes no timeout is desired." }
-    { { $link port-cutoff } " - the time when the current timeout expires; if no input data arrives before this time, an error is thrown" }
     { { $link port-type } " - a symbol identifying the port's intended purpose" }
     { { $link port-eof? } " - a flag indicating if the port has reached the end of file while reading" }
 } } ;
diff --git a/extra/io/nonblocking/nonblocking.factor b/extra/io/nonblocking/nonblocking.factor
index 5dbd3d1490..72507f26b6 100755
--- a/extra/io/nonblocking/nonblocking.factor
+++ b/extra/io/nonblocking/nonblocking.factor
@@ -1,10 +1,10 @@
 ! Copyright (C) 2005, 2008 Slava Pestov, Doug Coleman
 ! See http://factorcode.org/license.txt for BSD license.
 IN: io.nonblocking
-USING: math kernel io sequences io.buffers generic sbufs system
-io.streams.lines io.streams.plain io.streams.duplex io.backend
-continuations debugger classes byte-arrays namespaces splitting
-dlists assocs ;
+USING: math kernel io sequences io.buffers io.timeouts generic
+sbufs system io.streams.lines io.streams.plain io.streams.duplex
+io.backend continuations debugger classes byte-arrays namespaces
+splitting dlists assocs ;
 
 SYMBOL: default-buffer-size
 64 1024 * default-buffer-size set-global
@@ -13,9 +13,12 @@ SYMBOL: default-buffer-size
 TUPLE: port
 handle
 error
-timeout-entry timeout cutoff
+lapse
 type eof? ;
 
+! Ports support the lapse protocol
+M: port get-lapse port-lapse ;
+
 SYMBOL: closed
 
 PREDICATE: port input-port port-type input-port eq? ;
@@ -26,12 +29,11 @@ GENERIC: close-handle ( handle -- )
 
 : <port> ( handle buffer type -- port )
     pick init-handle
-    0 0 {
+    <lapse> {
         set-port-handle
         set-delegate
         set-port-type
-        set-port-timeout
-        set-port-cutoff
+        set-port-lapse
     } port construct ;
 
 : <buffered-port> ( handle type -- port )
@@ -48,50 +50,14 @@ GENERIC: close-handle ( handle -- )
     [ >r <reader> r> <duplex-stream> ] [ ] [ dispose ]
     cleanup ;
 
-: timeout? ( port -- ? )
-    port-cutoff dup zero? not swap millis < and ;
-
 : pending-error ( port -- )
     dup port-error f rot set-port-error [ throw ] when* ;
 
-SYMBOL: timeout-queue
-
-timeout-queue global [ [ <dlist> ] unless* ] change-at
-
-: unqueue-timeout ( port -- )
-    port-timeout-entry [
-        timeout-queue get-global swap delete-node
-    ] when* ;
-
-: queue-timeout ( port -- )
-    dup timeout-queue get-global push-front*
-    swap set-port-timeout-entry ;
-
 HOOK: cancel-io io-backend ( port -- )
 
 M: object cancel-io drop ;
 
-: expire-timeouts ( -- )
-    timeout-queue get-global dup dlist-empty? [ drop ] [
-        dup peek-back timeout?
-        [ pop-back cancel-io expire-timeouts ] [ drop ] if
-    ] if ;
-
-: begin-timeout ( port -- )
-    dup port-timeout dup zero? [
-        2drop
-    ] [
-        millis + over set-port-cutoff
-        dup unqueue-timeout queue-timeout
-    ] if ;
-
-: end-timeout ( port -- )
-    unqueue-timeout ;
-
-: with-port-timeout ( port quot -- )
-    over begin-timeout keep end-timeout ; inline
-
-M: port set-timeout set-port-timeout ;
+M: port timed-out cancel-io ;
 
 GENERIC: (wait-to-read) ( port -- )
 
diff --git a/extra/io/streams/null/null.factor b/extra/io/streams/null/null.factor
index f76b0cbce3..d747fa0a29 100755
--- a/extra/io/streams/null/null.factor
+++ b/extra/io/streams/null/null.factor
@@ -1,12 +1,12 @@
 ! Copyright (C) 2007 Slava Pestov.
 ! See http://factorcode.org/license.txt for BSD license.
 IN: io.streams.null
-USING: kernel io continuations ;
+USING: kernel io io.timeouts continuations ;
 
 TUPLE: null-stream ;
 
 M: null-stream dispose drop ;
-M: null-stream set-timeout 2drop ;
+M: null-stream set-timeout drop ;
 M: null-stream stream-readln drop f ;
 M: null-stream stream-read1 drop f ;
 M: null-stream stream-read-until 2drop f f ;
diff --git a/extra/io/timeouts/timeouts-docs.factor b/extra/io/timeouts/timeouts-docs.factor
new file mode 100755
index 0000000000..a704e3473a
--- /dev/null
+++ b/extra/io/timeouts/timeouts-docs.factor
@@ -0,0 +1,32 @@
+IN: io.timeouts
+USING: help.markup help.syntax math kernel ;
+
+HELP: get-lapse
+{ $values { "obj" object } { "lapse" lapse } }
+{ $contract "Outputs an object's timeout lapse descriptor." } ;
+
+HELP: set-timeout
+{ $values { "ms" integer } { "obj" object } }
+{ $contract "Sets an object's timeout, in milliseconds." }
+{ $notes "The default implementation delegates the call to the object's timeout lapse descriptor." } ;
+
+HELP: timed-out
+{ $values { "obj" object } }
+{ $contract "Handles a timeout, usually by waking up all threads waiting on the object." } ;
+
+HELP: with-timeout
+{ $values { "obj" object } { "quot" "a quotation with stack effect " { $snippet "( obj -- )" } } }
+{ $description "Applies the quotation to the object. If the object's timeout expires before the quotation returns, " { $link timed-out } " is called on the object." } ;
+
+ARTICLE: "io.timeouts" "I/O timeout protocol"
+"Streams and processes support optional timeouts, which impose an upper bound on the length of time for which an operation on these objects can block. Timeouts are used in network servers to prevent malicious clients from holding onto connections forever, and to ensure that runaway processes get killed."
+{ $subsection set-timeout }
+"The I/O timeout protocol can be implemented by any class wishing to support timeouts on blocking operations."
+{ $subsection get-lapse }
+{ $subsection timed-out }
+"A combinator to be used in operations which can time out:"
+{ $subsection with-timeout }
+{ $see-also "stream-protocol" "io.launcher" }
+;
+
+ABOUT: "io.timeouts"
diff --git a/extra/io/timeouts/timeouts.factor b/extra/io/timeouts/timeouts.factor
new file mode 100755
index 0000000000..ddc92a4bdd
--- /dev/null
+++ b/extra/io/timeouts/timeouts.factor
@@ -0,0 +1,67 @@
+! Copyright (C) 2008 Slava Pestov, Doug Coleman
+! See http://factorcode.org/license.txt for BSD license.
+USING: kernel math system dlists namespaces assocs init threads
+io.streams.duplex ;
+IN: io.timeouts
+
+TUPLE: lapse entry timeout cutoff ;
+
+: <lapse> f 0 0 \ lapse construct-boa ;
+
+GENERIC: get-lapse ( obj -- lapse )
+GENERIC: set-timeout ( ms obj -- )
+
+M: object set-timeout get-lapse set-lapse-timeout ;
+
+M: duplex-stream set-timeout
+    2dup
+    duplex-stream-in set-timeout
+    duplex-stream-out set-timeout ;
+
+: timeout ( obj -- ms ) get-lapse lapse-timeout ;
+: entry ( obj -- dlist-node ) get-lapse lapse-entry ;
+: set-entry ( obj dlist-node -- ) get-lapse set-lapse-entry ;
+: cutoff ( obj -- ms ) get-lapse lapse-cutoff ;
+: set-cutoff ( ms obj -- ) get-lapse set-lapse-cutoff ;
+
+SYMBOL: timeout-queue
+
+: timeout? ( lapse -- ? )
+    cutoff dup zero? not swap millis < and ;
+
+timeout-queue global [ [ <dlist> ] unless* ] change-at
+
+: unqueue-timeout ( obj -- )
+    entry [
+        timeout-queue get-global swap delete-node
+    ] when* ;
+
+: queue-timeout ( obj -- )
+    dup timeout-queue get-global push-front*
+    swap set-entry ;
+
+GENERIC: timed-out ( obj -- )
+
+M: object timed-out drop ;
+
+: expire-timeouts ( -- )
+    timeout-queue get-global dup dlist-empty? [ drop ] [
+        dup peek-back timeout?
+        [ pop-back timed-out expire-timeouts ] [ drop ] if
+    ] if ;
+
+: begin-timeout ( obj -- )
+    dup timeout dup zero? [
+        2drop
+    ] [
+        millis + over set-cutoff
+        dup unqueue-timeout queue-timeout
+    ] if ;
+
+: with-timeout ( obj quot -- )
+    over begin-timeout keep unqueue-timeout ; inline
+
+: expiry-thread ( -- )
+    expire-timeouts 5000 sleep expiry-thread ;
+
+[ [ expiry-thread ] in-thread ] "io.timeouts" add-init-hook
diff --git a/extra/io/unix/backend/backend.factor b/extra/io/unix/backend/backend.factor
index 7112c48551..7d9f76c686 100755
--- a/extra/io/unix/backend/backend.factor
+++ b/extra/io/unix/backend/backend.factor
@@ -3,7 +3,7 @@
 USING: alien generic assocs kernel kernel.private math
 io.nonblocking sequences strings structs sbufs threads unix
 vectors io.buffers io.backend io.streams.duplex math.parser
-continuations system libc qualified namespaces ;
+continuations system libc qualified namespaces io.timeouts ;
 QUALIFIED: io
 IN: io.unix.backend
 
@@ -61,7 +61,7 @@ M: mx register-io-task ( task mx -- )
     mx get-global register-io-task stop ;
 
 : with-port-continuation ( port quot -- port )
-    [ callcc0 ] curry with-port-timeout ; inline
+    [ callcc0 ] curry with-timeout ; inline
 
 M: mx unregister-io-task ( task mx -- )
     fd/container delete-at drop ;
@@ -178,7 +178,7 @@ M: port port-flush ( port -- )
     dup buffer-empty? [ drop ] [ (wait-to-write) ] if ;
 
 M: unix-io io-multiplex ( ms -- )
-    expire-timeouts mx get-global wait-for-events ;
+    mx get-global wait-for-events ;
 
 M: unix-io init-stdio ( -- )
     0 1 handle>duplex-stream io:stdio set-global
diff --git a/extra/io/unix/linux/linux.factor b/extra/io/unix/linux/linux.factor
index 55f5f01abc..b3bd2eee4e 100755
--- a/extra/io/unix/linux/linux.factor
+++ b/extra/io/unix/linux/linux.factor
@@ -1,9 +1,10 @@
 ! Copyright (C) 2008 Slava Pestov.
 ! See http://factorcode.org/license.txt for BSD license.
-USING: kernel io.backend io.monitors io.monitors.private io.files
-io.buffers io.nonblocking io.unix.backend io.unix.select
-io.unix.launcher unix.linux.inotify assocs namespaces threads
-continuations init math alien.c-types alien vocabs.loader ;
+USING: kernel io.backend io.monitors io.monitors.private
+io.files io.buffers io.nonblocking io.timeouts io.unix.backend
+io.unix.select io.unix.launcher unix.linux.inotify assocs
+namespaces threads continuations init math alien.c-types alien
+vocabs.loader ;
 IN: io.unix.linux
 
 TUPLE: linux-io ;
diff --git a/extra/io/unix/unix.factor b/extra/io/unix/unix.factor
index 7dc66a05ad..9013df29aa 100755
--- a/extra/io/unix/unix.factor
+++ b/extra/io/unix/unix.factor
@@ -1,4 +1,4 @@
-USING: io.unix.backend io.unix.files io.unix.sockets
+USING: io.unix.backend io.unix.files io.unix.sockets io.timeouts
 io.unix.launcher io.unix.mmap io.backend combinators namespaces
 system vocabs.loader ;
 
diff --git a/extra/io/windows/ce/sockets/sockets.factor b/extra/io/windows/ce/sockets/sockets.factor
index 9114dceb75..e9ca6220af 100755
--- a/extra/io/windows/ce/sockets/sockets.factor
+++ b/extra/io/windows/ce/sockets/sockets.factor
@@ -55,7 +55,7 @@ M: windows-ce-io accept ( server -- client )
             ] keep
         ] keep server-port-addr parse-sockaddr swap
         <win32-socket> dup handle>duplex-stream <client-stream>
-    ] with-port-timeout ;
+    ] with-timeout ;
 
 M: windows-ce-io <datagram> ( addrspec -- datagram )
     [
diff --git a/extra/io/windows/nt/backend/backend.factor b/extra/io/windows/nt/backend/backend.factor
index 760bcec457..597bc99be2 100755
--- a/extra/io/windows/nt/backend/backend.factor
+++ b/extra/io/windows/nt/backend/backend.factor
@@ -91,7 +91,7 @@ M: windows-nt-io cancel-io
     port-handle win32-file-handle CancelIo drop ;
 
 M: windows-nt-io io-multiplex ( ms -- )
-    expire-timeouts drain-overlapped ;
+    drain-overlapped ;
 
 M: windows-nt-io init-io ( -- )
     <master-completion-port> master-completion-port set-global
diff --git a/extra/io/windows/nt/files/files.factor b/extra/io/windows/nt/files/files.factor
index a1c331816c..ecc989530e 100755
--- a/extra/io/windows/nt/files/files.factor
+++ b/extra/io/windows/nt/files/files.factor
@@ -1,8 +1,8 @@
 USING: continuations destructors io.buffers io.files io.backend
-io.nonblocking io.windows io.windows.nt.backend kernel libc math
-threads windows windows.kernel32 alien.c-types alien.arrays
-sequences combinators combinators.lib sequences.lib ascii
-splitting alien strings ;
+io.timeouts io.nonblocking io.windows io.windows.nt.backend
+kernel libc math threads windows windows.kernel32 alien.c-types
+alien.arrays sequences combinators combinators.lib sequences.lib
+ascii splitting alien strings ;
 IN: io.windows.nt.files
 
 M: windows-nt-io cwd
@@ -98,7 +98,7 @@ M: windows-nt-io FileArgs-overlapped ( port -- overlapped )
     ] if ;
 
 : flush-output ( port -- )
-    [ [ (flush-output) ] with-port-timeout ] with-destructors ;
+    [ [ (flush-output) ] with-timeout ] with-destructors ;
 
 M: port port-flush
     dup buffer-empty? [ dup flush-output ] unless drop ;
@@ -122,4 +122,4 @@ M: port port-flush
     ] [ 2drop ] if ;
 
 M: input-port (wait-to-read) ( port -- )
-    [ [ ((wait-to-read)) ] with-port-timeout ] with-destructors ;
+    [ [ ((wait-to-read)) ] with-timeout ] with-destructors ;
diff --git a/extra/io/windows/nt/monitors/monitors.factor b/extra/io/windows/nt/monitors/monitors.factor
index a593e829fe..a7a1e2f485 100755
--- a/extra/io/windows/nt/monitors/monitors.factor
+++ b/extra/io/windows/nt/monitors/monitors.factor
@@ -3,8 +3,9 @@
 USING: alien.c-types destructors io.windows
 io.windows.nt.backend kernel math windows windows.kernel32
 windows.types libc assocs alien namespaces continuations
-io.monitors io.monitors.private io.nonblocking io.buffers io.files
-io sequences hashtables sorting arrays combinators ;
+io.monitors io.monitors.private io.nonblocking io.buffers
+io.files io.timeouts io sequences hashtables sorting arrays
+combinators ;
 IN: io.windows.nt.monitors
 
 : open-directory ( path -- handle )
@@ -52,7 +53,7 @@ M: windows-nt-io <monitor> ( path recursive? -- monitor )
             swap [ save-callback ] 2keep
             dup check-monitor ! we may have closed it...
             get-overlapped-result
-        ] with-port-timeout
+        ] with-timeout
     ] with-destructors ;
 
 : parse-action ( action -- changed )
diff --git a/extra/io/windows/nt/sockets/sockets.factor b/extra/io/windows/nt/sockets/sockets.factor
index 77249df9f1..eef7476dd5 100755
--- a/extra/io/windows/nt/sockets/sockets.factor
+++ b/extra/io/windows/nt/sockets/sockets.factor
@@ -1,6 +1,6 @@
 USING: alien alien.accessors alien.c-types byte-arrays
-continuations destructors io.nonblocking io io.sockets
-io.sockets.impl namespaces io.streams.duplex io.windows
+continuations destructors io.nonblocking io.timeouts io.sockets
+io.sockets.impl io namespaces io.streams.duplex io.windows
 io.windows.nt.backend windows.winsock kernel libc math sequences
 threads tuples.lib ;
 IN: io.windows.nt.sockets
@@ -139,7 +139,7 @@ M: windows-nt-io accept ( server -- client )
             AcceptEx-args-port pending-error
             dup duplex-stream-in pending-error
             dup duplex-stream-out pending-error
-        ] with-port-timeout
+        ] with-timeout
     ] with-destructors ;
 
 M: windows-nt-io <server> ( addrspec -- server )
diff --git a/extra/smtp/server/server.factor b/extra/smtp/server/server.factor
old mode 100644
new mode 100755
index 2cfc1e65e4..275deee994
--- a/extra/smtp/server/server.factor
+++ b/extra/smtp/server/server.factor
@@ -27,8 +27,8 @@
 ! bye
 ! Connection closed by foreign host.
 
-USING: combinators kernel prettyprint io io.server sequences
-namespaces io.sockets continuations ;
+USING: combinators kernel prettyprint io io.timeouts io.server
+sequences namespaces io.sockets continuations ;
 
 SYMBOL: data-mode
 
diff --git a/extra/smtp/smtp.factor b/extra/smtp/smtp.factor
index 211fbbcabd..27aac1202e 100755
--- a/extra/smtp/smtp.factor
+++ b/extra/smtp/smtp.factor
@@ -1,8 +1,9 @@
-! Copyright (C) 2007, 2008 Elie CHAFTARI, Dirk Vleugels, Slava Pestov.
+! Copyright (C) 2007, 2008 Elie CHAFTARI, Dirk Vleugels,
+! Slava Pestov.
 ! See http://factorcode.org/license.txt for BSD license.
-USING: namespaces io kernel logging io.sockets sequences
-combinators sequences.lib splitting assocs strings math.parser
-random system calendar ;
+USING: namespaces io io.timeouts kernel logging io.sockets
+sequences combinators sequences.lib splitting assocs strings
+math.parser random system calendar ;
 
 IN: smtp
 
diff --git a/extra/ui/backend/backend.factor b/extra/ui/backend/backend.factor
index a0646f35b0..cc1f5f7d05 100755
--- a/extra/ui/backend/backend.factor
+++ b/extra/ui/backend/backend.factor
@@ -7,6 +7,10 @@ SYMBOL: ui-backend
 
 HOOK: set-title ui-backend ( string world -- )
 
+HOOK: set-fullscreen? ui-backend ( ? world -- )
+
+HOOK: fullscreen? ui-backend ( world -- ? )
+
 HOOK: (open-window) ui-backend ( world -- )
 
 HOOK: (close-window) ui-backend ( handle -- )
diff --git a/extra/ui/cocoa/cocoa.factor b/extra/ui/cocoa/cocoa.factor
index 1e46544180..184e6fd856 100755
--- a/extra/ui/cocoa/cocoa.factor
+++ b/extra/ui/cocoa/cocoa.factor
@@ -1,6 +1,6 @@
 ! Copyright (C) 2006, 2007 Slava Pestov.
 ! See http://factorcode.org/license.txt for BSD license.
-USING: arrays cocoa cocoa.application command-line
+USING: math arrays cocoa cocoa.application command-line
 kernel memory namespaces cocoa.messages cocoa.runtime
 cocoa.subclassing cocoa.pasteboard cocoa.types cocoa.windows
 cocoa.classes cocoa.application sequences system ui ui.backend
@@ -53,6 +53,18 @@ M: pasteboard set-clipboard-contents
 M: cocoa-ui-backend set-title ( string world -- )
     world-handle second swap <NSString> -> setTitle: ;
 
+: enter-fullscreen ( world -- )
+    world-handle first NSScreen -> mainScreen f -> enterFullScreenMode:withOptions: drop ;
+
+: exit-fullscreen ( world -- )
+    world-handle first f -> exitFullScreenModeWithOptions: ;
+
+M: cocoa-ui-backend set-fullscreen? ( ? world -- )
+    swap [ enter-fullscreen ] [ exit-fullscreen ] if ;
+
+M: cocoa-ui-backend fullscreen? ( world -- ? )
+    world-handle first -> isInFullScreenMode zero? not ;
+
 : auto-position ( world -- )
     dup world-loc { 0 0 } = [
         world-handle second -> center
diff --git a/extra/ui/gadgets/worlds/worlds-docs.factor b/extra/ui/gadgets/worlds/worlds-docs.factor
index a47717329d..8a64750751 100755
--- a/extra/ui/gadgets/worlds/worlds-docs.factor
+++ b/extra/ui/gadgets/worlds/worlds-docs.factor
@@ -13,6 +13,15 @@ HELP: set-title
 { $description "Sets the title bar of the native window containing the world." }
 { $notes "This word should not be called directly by user code. Instead, change the " { $link world-title } " model; see " { $link "models" } "." } ;
 
+HELP: set-fullscreen?
+{ $values { "?" "a boolean" } { "world" world } }
+{ $description "Sets and unsets fullscreen mode for the world." }
+{ $notes "Find a world using " { $link find-world } "." } ;
+
+HELP: fullscreen?
+{ $values { "world" world } { "?" "a boolean" } }
+{ $description "Queries the world to see if it is running in fullscreen mode." } ;
+
 HELP: raise-window
 { $values { "world" world } }
 { $description "Makes the native window containing the given world the front-most window." }
diff --git a/extra/ui/tools/walker/walker.factor b/extra/ui/tools/walker/walker.factor
index 4740ff86d4..a23345d214 100755
--- a/extra/ui/tools/walker/walker.factor
+++ b/extra/ui/tools/walker/walker.factor
@@ -21,21 +21,21 @@ TUPLE: walker model interpreter history ;
 : walker-active? ( walker -- ? )
     walker-interpreter interpreter-continuation >boolean ;
 
-: walker-command ( gadget quot -- )
-    over walker-active? [ with-walker ] [ 2drop ] if ; inline
-
 : save-interpreter ( walker -- )
     dup walker-interpreter interpreter-continuation clone
     swap walker-history push ;
 
-: com-step ( walker -- )
-    dup save-interpreter [ step ] walker-command ;
+: walker-command ( gadget quot -- )
+    over walker-active? [
+        over save-interpreter
+        with-walker
+    ] [ 2drop ] if ; inline
 
-: com-into ( walker -- )
-    dup save-interpreter [ step-into ] walker-command ;
+: com-step ( walker -- ) [ step ] walker-command ;
 
-: com-out ( walker -- )
-    dup save-interpreter [ step-out ] walker-command ;
+: com-into ( walker -- ) [ step-into ] walker-command ;
+
+: com-out ( walker -- ) [ step-out ] walker-command ;
 
 : com-back ( walker -- )
     dup walker-history