diff --git a/racket/src/cs/main.sps b/racket/src/cs/main.sps
index 7651e6d7cd..a70b9fbfc4 100644
--- a/racket/src/cs/main.sps
+++ b/racket/src/cs/main.sps
@@ -207,6 +207,8 @@
             (let () body ...)
             (string-case arg rest ...))]))
 
+   (define remaining-command-line-arguments '#())
+
    (seq
     (let flags-loop ([args (list-tail the-command-line-arguments 5)]
                      [saw (hasheq)])
@@ -220,7 +222,8 @@
                (not (saw? saw 'non-config)))
           (loop (cons "-u" args))]
          [else
-          (|#%app| current-command-line-arguments (list->vector args))
+          (set! remaining-command-line-arguments (vector->immutable-vector
+                                                  (list->vector args)))
           (when (and (null? args) (not (saw? saw 'non-config)))
             (set! repl? #t)
             (unless gracket?
@@ -459,6 +462,7 @@
                '()))))
 
    (define (initialize-place!)
+     (|#%app| current-command-line-arguments remaining-command-line-arguments)
      (|#%app| use-compiled-file-paths compiled-file-paths)
      (|#%app| use-user-specific-search-paths user-specific-search-paths?)
      (|#%app| load-on-demand-enabled load-on-demand?)
diff --git a/racket/src/cs/place-register.ss b/racket/src/cs/place-register.ss
index ff5a9696a0..37a2accc29 100644
--- a/racket/src/cs/place-register.ss
+++ b/racket/src/cs/place-register.ss
@@ -5,16 +5,16 @@
 ;; first index is reserved for Rumble:
 
 (meta chez:define thread-register-start 1)
-(meta chez:define thread-register-count 14)
+(meta chez:define thread-register-count 31)
 
 (meta chez:define io-register-start (+ thread-register-start thread-register-count))
-(meta chez:define io-register-count 16)
+(meta chez:define io-register-count 32)
 
 (meta chez:define regexp-register-start (+ io-register-start io-register-count))
-(meta chez:define regexp-register-count 3)
+(meta chez:define regexp-register-count 32)
 
 (meta chez:define expander-register-start (+ regexp-register-start regexp-register-count))
-(meta chez:define expander-register-count 30)
+(meta chez:define expander-register-count 32)
 
 ;; ----------------------------------------
 
diff --git a/racket/src/cs/rumble/place.ss b/racket/src/cs/rumble/place.ss
index 33faac057c..40c5abcc1e 100644
--- a/racket/src/cs/rumble/place.ss
+++ b/racket/src/cs/rumble/place.ss
@@ -7,7 +7,7 @@
 ;; place-local values, and the rest are used by the thread, io, etc.,
 ;; layers for directly accessed variables.
 
-(define NUM-PLACE-REGISTERS 64)
+(define NUM-PLACE-REGISTERS 128)
 
 (define-virtual-register place-registers (make-vector NUM-PLACE-REGISTERS 0))
 (define place-register-inits (make-vector NUM-PLACE-REGISTERS 0))
diff --git a/racket/src/thread/place-message.rkt b/racket/src/thread/place-message.rkt
index 8120a6284a..4d50b641cd 100644
--- a/racket/src/thread/place-message.rkt
+++ b/racket/src/thread/place-message.rkt
@@ -42,7 +42,7 @@
              (or (not direct?)
                  (and (immutable? v)
                       (not (impersonator? v))))
-             (let ([graph (hash-ref graph v #t)])
+             (let ([graph (hash-set graph v #t)])
                (for/and ([e (in-vector v)])
                  (loop e graph))))
         (and (immutable-prefab-struct-key v)
@@ -128,7 +128,7 @@
                   (apply make-prefab-struct
                          k
                          (for/list ([e (in-vector (struct->vector v) 1)])
-                           (loop v)))))]
+                           (loop e)))))]
            [(hash? v)
             (define ph (make-placeholder #f))
             (hash-set! graph v ph)
@@ -177,14 +177,15 @@
       [(pair? v)
        (cons (loop (car v)) (loop (cdr v)))]
       [(vector? v)
-       (for/vector #:length (vector-length v) ([e (in-vector v)])
-         (loop e))]
+       (vector->immutable-vector
+        (for/vector #:length (vector-length v) ([e (in-vector v)])
+          (loop e)))]
       [(immutable-prefab-struct-key v)
        => (lambda (k)
             (apply make-prefab-struct
                    k
                    (for/list ([e (in-vector (struct->vector v) 1)])
-                     (loop v))))]
+                     (loop e))))]
       [(hash? v)
        (cond
          [(hash-eq? v)
diff --git a/racket/src/thread/schedule.rkt b/racket/src/thread/schedule.rkt
index 9c297466f4..f544dafb1a 100644
--- a/racket/src/thread/schedule.rkt
+++ b/racket/src/thread/schedule.rkt
@@ -36,6 +36,7 @@
 (define (call-in-another-main-thread c thunk)
   (make-another-initial-thread-group)
   (set-root-custodian! c)
+  (init-system-idle-evt!)
   (call-in-main-thread thunk))
 
 ;; ----------------------------------------
diff --git a/racket/src/thread/system-idle-evt.rkt b/racket/src/thread/system-idle-evt.rkt
index 5ec00d5440..b5cadbbfb0 100644
--- a/racket/src/thread/system-idle-evt.rkt
+++ b/racket/src/thread/system-idle-evt.rkt
@@ -1,14 +1,16 @@
 #lang racket/base
-(require "evt.rkt"
+(require "place-local.rkt"
+         "evt.rkt"
          "semaphore.rkt")
 
 (provide (rename-out [get-system-idle-evt system-idle-evt])
 
          any-idle-waiters?
-         post-idle)
+         post-idle
+         init-system-idle-evt!)
 
-(define idle-sema (make-semaphore))
-(define wrapped-idle-sema (wrap-evt idle-sema void))
+(define-place-local idle-sema (make-semaphore))
+(define-place-local wrapped-idle-sema (wrap-evt idle-sema void))
 (struct system-idle-evt ()
   #:property prop:evt (lambda (i) wrapped-idle-sema))
 
@@ -29,3 +31,7 @@
        (begin
          (semaphore-post/atomic idle-sema)
          #t)))
+
+(define (init-system-idle-evt!)
+  (set! idle-sema (make-semaphore))
+  (set! wrapped-idle-sema (wrap-evt idle-sema void)))