diff --git a/boot/pb/equates.h b/boot/pb/equates.h
index 4ee0aabc1..7e4bf03fc 100644
--- a/boot/pb/equates.h
+++ b/boot/pb/equates.h
@@ -1,4 +1,4 @@
-/* equates.h for Chez Scheme Version 9.9.9-pre-release.22 */
+/* equates.h for Chez Scheme Version 9.9.9-pre-release.23 */
 
 /* Do not edit this file.  It is automatically generated and */
 /* specifically tailored to the version of Chez Scheme named */
@@ -1010,7 +1010,7 @@ typedef uint64_t U64;
 #define rtd_sealed 0x4
 #define sbwp (ptr)0x4E
 #define scaled_shot_1_shot_flag -0x8
-#define scheme_version 0x9090916
+#define scheme_version 0x9090917
 #define seginfo_generation_disp 0x1
 #define seginfo_list_bits_disp 0x8
 #define seginfo_space_disp 0x0
diff --git a/boot/pb/petite.boot b/boot/pb/petite.boot
index a9cf2e991..b75ca78b1 100644
Binary files a/boot/pb/petite.boot and b/boot/pb/petite.boot differ
diff --git a/boot/pb/scheme.boot b/boot/pb/scheme.boot
index 68d0244aa..699cef1e1 100644
Binary files a/boot/pb/scheme.boot and b/boot/pb/scheme.boot differ
diff --git a/boot/pb/scheme.h b/boot/pb/scheme.h
index f0713f57a..24a1418bf 100644
--- a/boot/pb/scheme.h
+++ b/boot/pb/scheme.h
@@ -1,4 +1,4 @@
-/* scheme.h for Chez Scheme Version 9.9.9-pre-release.22 (pb) */
+/* scheme.h for Chez Scheme Version 9.9.9-pre-release.23 (pb) */
 
 /* Do not edit this file.  It is automatically generated and */
 /* specifically tailored to the version of Chez Scheme named */
@@ -40,7 +40,7 @@
 #endif
 
 /* Chez Scheme Version and machine type */
-#define VERSION "9.9.9-pre-release.22"
+#define VERSION "9.9.9-pre-release.23"
 #define MACHINE_TYPE "pb"
 
 /* Integer typedefs */
diff --git a/csug/objects.stex b/csug/objects.stex
index 961462da9..fdc0dd815 100644
--- a/csug/objects.stex
+++ b/csug/objects.stex
@@ -760,22 +760,51 @@ Any attempt to modify an immutable vector causes an exception to be raised.
 %----------------------------------------------------------------------------
 \entryheader
 \formdef{vector-copy}{\categoryprocedure}{(vector-copy \var{vector})}
-\returns a copy of \var{vector}
+\formdef{vector-copy}{\categoryprocedure}{(vector-copy \var{vector} \var{start} \var{end})}
+\returns a new vector
 \listlibraries
 \endentryheader
 
 \noindent
-\scheme{vector-copy} creates a new vector of the same length and contents
-as \var{vector}.
-The elements themselves are not copied.
+\var{vector} must be a vector.
+\var{start} and \var{end} must be exact nonnegative integers, both
+in the range \scheme{0} to the length of \var{vector}, inclusive,
+and \var{start} must be less or equal to \var{end}. When \var{start}
+and \var{end} are not supplied, \scheme{0} and
+\scheme{(vector-length \var{vector})} are used.
+
+\noindent
+\scheme{vector-copy} creates a new vector of length
+\var{end}-\var{start} and contents as elements \var{start} through
+\var{end}-1 of \var{vector}. When \var{start} and \var{end} are not
+supplied, the result is a copy of \var{vector}. The vector elements
+themselves are not copied.
 
 \schemedisplay
 (vector-copy '#(a b c)) ;=> #(a b c)
+(vector-copy '#(a b c d) 1 3) ;=> #(b c)
 
 (let ([v '#(a b c)])
   (eq? v (vector-copy v))) ;=> #f
 \endschemedisplay
 
+%----------------------------------------------------------------------------
+\entryheader
+\formdef{vector-append}{\categoryprocedure}{(vector-append \var{vector} \dots)}
+\returns a new vector
+\listlibraries
+\endentryheader
+
+\noindent
+\scheme{vector-append} creates a new vector whose content is the
+concatenation of the given \var{vector}s in order.
+
+\schemedisplay
+(vector-append '#(a b c)) ;=> #(a b c)
+(vector-append '#(a b c) #'(d e) #'(f)) ;=> #(a b c d e f)
+(vector-append) ;=> #()
+\endschemedisplay
+
 %----------------------------------------------------------------------------
 \entryheader
 \formdef{vector-set-fixnum!}{\categoryprocedure}{(vector-set-fixnum! \var{vector} \var{n} \var{fixnum})}
diff --git a/mats/5_6.ms b/mats/5_6.ms
index 4ba11b913..49596055a 100644
--- a/mats/5_6.ms
+++ b/mats/5_6.ms
@@ -114,6 +114,10 @@
 (mat vector-copy
     (equal? (vector-copy '#()) '#())
     (equal? (vector-copy '#(a b c)) '#(a b c))
+    (equal? (vector-copy '#(a b c) 0 1) '#(a))
+    (equal? (vector-copy '#(a b c) 2 3) '#(c))
+    (equal? (vector-copy '#(a b c d) 1 3) '#(b c))
+    (eq? (vector-copy '#(a b c d) 1 1) '#())
     (let* ((x1 (vector 1 2 3)) (x2 (vector-copy x1)))
         (and (equal? x2 x1) (not (eq? x2 x1))))
     (andmap
@@ -122,6 +126,26 @@
           (equal? (vector-copy v) v)))
       (map random (make-list 500 2500)))
     (error? (vector-copy '(a b c)))
+    (error? (vector-copy '#(a b c) 'x 2))
+    (error? (vector-copy '#(a b c) 1 'x))
+    (error? (vector-copy '#(a b c) -1 2))
+    (error? (vector-copy '#(a b c) 1 4))
+    (error? (vector-copy '#(a b c) 2 1))
+    )
+
+(mat vector-append
+    (eq? (vector-append) '#())
+    (eq? (vector-append '#()) '#())
+    (eq? (vector-append '#() '#()) '#())
+    (eq? (vector-append '#() '#() '#()) '#())
+    (eq? (vector-append '#() '#() '#() '#()) '#())
+    (equal? (vector-append '#(a b c)) '#(a b c))
+    (equal? (vector-append '#(a b c) '#(d e)) '#(a b c d e))
+    (equal? (vector-append '#(a b c) '#(d e) '#(f) '#(g h i)) '#(a b c d e f g h i))
+    (error? (vector-append 1))
+    (error? (vector-append '#(a b c) 'x))
+    (error? (vector-append '#(a b c) '#(d) 'x))
+    (error? (vector-append '#(a b c) '#(d) '#(e)'x))
  )
 
 (mat vector-fill!
diff --git a/mats/root-experr-compile-0-f-f-f b/mats/root-experr-compile-0-f-f-f
index 3b8893086..4beef71b0 100644
--- a/mats/root-experr-compile-0-f-f-f
+++ b/mats/root-experr-compile-0-f-f-f
@@ -4276,6 +4276,15 @@ cp0.mo:Expected error in mat expand/optimize-output: "expand/optimize-output: #<
 5_6.mo:Expected error in mat vector-set-fixnum!: "vector-set-fixnum!: #\d is not a fixnum".
 5_6.mo:Expected error in mat vector-set-fixnum!: "vector-set-fixnum!: (a b c) is not a fixnum".
 5_6.mo:Expected error in mat vector-copy: "vector-copy: (a b c) is not a vector".
+5_6.mo:Expected error in mat vector-copy: "vector-copy: x and 2 are not valid start/end indices for #(a b c)".
+5_6.mo:Expected error in mat vector-copy: "vector-copy: 1 and x are not valid start/end indices for #(a b c)".
+5_6.mo:Expected error in mat vector-copy: "vector-copy: -1 and 2 are not valid start/end indices for #(a b c)".
+5_6.mo:Expected error in mat vector-copy: "vector-copy: 1 and 4 are not valid start/end indices for #(a b c)".
+5_6.mo:Expected error in mat vector-copy: "vector-copy: 2 and 1 are not valid start/end indices for #(a b c)".
+5_6.mo:Expected error in mat vector-append: "vector-append: 1 is not a vector".
+5_6.mo:Expected error in mat vector-append: "vector-append: x is not a vector".
+5_6.mo:Expected error in mat vector-append: "vector-append: x is not a vector".
+5_6.mo:Expected error in mat vector-append: "vector-append: x is not a vector".
 5_6.mo:Expected error in mat vector-fill!: "vector-fill!: #vfx() is not a mutable vector".
 5_6.mo:Expected error in mat list->vector: "list->vector: #(a b c) is not a proper list".
 5_6.mo:Expected error in mat list->vector: "list->vector: (#\a #\b . #\c) is not a proper list".
diff --git a/release_notes/release_notes.stex b/release_notes/release_notes.stex
index e63d71357..cd22ae116 100644
--- a/release_notes/release_notes.stex
+++ b/release_notes/release_notes.stex
@@ -461,6 +461,16 @@ stencil-vector-mask-width
 \endschemedisplay
 
 
+\subsection{New vector functions (9.9.9)}
+
+The \scheme{vector-copy} function now accepts optional start and end
+positions to create a vector that contains a subsequence of the
+original vector's elements. The new \scheme{vector-append} function
+combines vectors. Although these functions could be implemented with
+\scheme{make-vector} and \scheme{vector-set!}, the new versions avoid
+redundant initialization and write barriers.
+
+
 \subsection{New symbol functions (9.9.9)}
 
 While gensyms support most symbol-generation needs, uninterned symbols
diff --git a/s/5_6.ss b/s/5_6.ss
index 725fc8b1f..a94332aa8 100644
--- a/s/5_6.ss
+++ b/s/5_6.ss
@@ -35,26 +35,64 @@
             (loop (cdr ls) (fx+ i 2))))))
     v))
 
-(define ($vector-copy! v1 v2 n)
+(define ($vector-copy! v1 v2 n delta)
   (let loop ([i (fx- n 1)])
     (cond
       [(fx> i 0)
-       (vector-set! v2 i (vector-ref v1 i))
-       (let ([i (fx- i 1)]) (vector-set! v2 i (vector-ref v1 i)))
+       (vector-set! v2 (fx+ i delta) (vector-ref v1 i))
+       (let ([i (fx- i 1)]) (vector-set! v2 (fx+ i delta) (vector-ref v1 i)))
        (loop (fx- i 2))]
-      [(fx= i 0) (vector-set! v2 i (vector-ref v1 i))])))
+      [(fx= i 0) (vector-set! v2 (fx+ i delta) (vector-ref v1 i))])))
 
-;; assumes that `v2` is newer than values to copy
-(define ($vector-fill-copy! v1 v2 n)
-  (if (fx<= n 10)
-      ($vector-copy! v1 v2 n)
-      ($ptr-copy! v1 (constant vector-data-disp) v2
-        (constant vector-data-disp) n)))
-
-(define ($vector-copy v1 n)
-  (let ([v2 (make-vector n)])
-    ($vector-fill-copy! v1 v2 n)
-    v2))
+(set-who! vector-copy
+  (case-lambda
+   [(v)
+    (unless (vector? v)
+      ($oops who "~s is not a vector" v))
+    (#3%vector-copy v 0 (vector-length v))]
+   [(v start end)
+    (unless (vector? v)
+      ($oops who "~s is not a vector" v))
+    (unless (and (fixnum? start) (fixnum? end) (fx<= 0 start end (vector-length v)))
+      ($oops 'vector-copy
+             "~s and ~s are not valid start/end indices for ~s"
+             start end v))
+    (#3%vector-copy v start end)]))
+
+(set-who! vector-append
+  (let ([not-a-vector
+         (lambda (v)
+           ($oops who "~s is not a vector" v))])
+    (case-lambda
+      [(v)
+       (unless (vector? v) (not-a-vector v))
+       (vector-copy v)]
+      [(v1 v2)
+       (unless (vector? v1) (not-a-vector v1))
+       (unless (vector? v2) (not-a-vector v2))
+       (#3%vector-append v1 v2)]
+      [(v1 v2 v3)
+       (unless (vector? v1) (not-a-vector v1))
+       (unless (vector? v2) (not-a-vector v2))
+       (unless (vector? v3) (not-a-vector v3))
+       (#3%vector-append v1 v2 v3)]
+      [vs
+       (let ([len (let loop ([vs vs])
+                    (cond
+                      [(null? vs) 0]
+                      [else
+                       (let ([v (car vs)])
+                         (unless (vector? v) (not-a-vector v))
+                         (fx+ (vector-length v) (loop (cdr vs))))]))])
+         (let ([dest (make-vector len)])
+           (let loop ([vs vs] [i 0])
+             (cond
+               [(null? vs) dest]
+               [else
+                (let* ([v (car vs)]
+                       [len (vector-length v)])
+                  ($vector-copy! v dest len i)
+                  (loop (cdr vs) (fx+ i len)))]))))])))
 
 (set! vector->list
   (lambda (v)
@@ -66,12 +104,6 @@
   (lambda (ls)
     ($list->vector ls ($list-length ls 'list->vector))))
 
-(set! vector-copy
-  (lambda (v)
-    (unless (vector? v)
-      ($oops 'vector-copy "~s is not a vector" v))
-    ($vector-copy v (vector-length v))))
-
 (set-who! vector->immutable-vector
   (lambda (v)
     (cond
@@ -395,7 +427,7 @@
       (unless (procedure? elt<) ($oops who "~s is not a procedure" elt<))
       (unless (vector? v) ($oops who "~s is not a vector" v))
       (let ([n (vector-length v)])
-        (if (fx<= n 1) v (dovsort! elt< ($vector-copy v n) n)))))
+        (if (fx<= n 1) v (dovsort! elt< (vector-copy v 0 n) n)))))
 
   (set-who! vector-sort!
     (lambda (elt< v)
@@ -405,7 +437,7 @@
         (unless (fx<= n 1)
           (let ([outvec (dovsort! elt< v n)])
             (unless (eq? outvec v)
-              ($vector-copy! outvec v n)))))))
+              ($vector-copy! outvec v n 0)))))))
 
   (set-who! list-sort
     (lambda (elt< ls)
diff --git a/s/cmacros.ss b/s/cmacros.ss
index 0eeec7d6f..ae5272659 100644
--- a/s/cmacros.ss
+++ b/s/cmacros.ss
@@ -357,7 +357,7 @@
 ;; ---------------------------------------------------------------------
 ;; Version and machine types:
 
-(define-constant scheme-version #x09090916)
+(define-constant scheme-version #x09090917)
 
 (define-syntax define-machine-types
   (lambda (x)
diff --git a/s/cpprim.ss b/s/cpprim.ss
index aa934ff6e..a1b8fc044 100644
--- a/s/cpprim.ss
+++ b/s/cpprim.ss
@@ -7352,8 +7352,8 @@
       (let ()
         (define do-make-vector
           (lambda (e-length e-fill)
-            ; NB: caller must bind e-fill
-            (safe-assert (no-need-to-bind? #f e-fill))
+            ; NB: caller must bind e-fill, if not #f
+            (safe-assert (or (not e-fill) (no-need-to-bind? #f e-fill)))
             (if (constant? (lambda (x) (and (fixnum? x) (fx<= 0 x 10000))) e-length)
                 (let ([n (constant-value e-length)])
                   (if (fx= n 0)
@@ -7365,7 +7365,9 @@
                              (set! ,(%mref ,t ,(constant vector-type-disp))
                                (immediate ,(+ (fx* n (constant vector-length-factor))
                                               (constant type-vector))))
-                             ,(build-vector-fill t `(immediate ,bytes) e-fill))))))
+                             ,(if e-fill
+                                  (build-vector-fill t `(immediate ,bytes) e-fill)
+                                  t))))))
                 (bind #t (e-length) ; fixnum length doubles as byte count
                   (let ([t-vec (make-tmp 'tvec)])
                     `(if ,(%inline eq? ,e-length (immediate 0))
@@ -7382,11 +7384,63 @@
                                   (constant type-vector)
                                   (constant fixnum-offset)
                                   (constant vector-length-offset)))
-                             ,(build-vector-fill t-vec e-length e-fill)))))))))
+                             ,(if e-fill
+                                  (build-vector-fill t-vec e-length e-fill)
+                                  t-vec)))))))))
         (define default-fill `(immediate ,(fix 0)))
         (define-inline 3 make-vector
           [(e-length) (do-make-vector e-length default-fill)]
           [(e-length e-fill) (bind #t (e-fill) (do-make-vector e-length e-fill))])
+        (let ()
+          (define (extract-vector-length vec)
+            (extract-length (%mref ,vec ,(constant vector-type-disp)) (constant vector-length-offset)))
+          (define build-vector-copy
+            (lambda (e-vec e-start e-end)
+              (let ([Ltop (make-local-label 'Ltop)]
+                    [vec (make-assigned-tmp 'vec 'ptr)]
+                    [t (make-assigned-tmp 't 'uptr)])
+                (bind #t (e-vec e-start e-end)
+                  `(let ([,t ,e-start]
+                         [,vec ,(do-make-vector (%inline - ,e-end ,e-start) #f)])
+                     (label ,Ltop
+                       (if ,(%inline eq? ,t ,e-end)
+                           ,vec
+                           ,(%seq
+                             (set! ,(%mref ,vec ,(%inline - ,t ,e-start) ,(constant vector-data-disp))
+                                   ,(%mref ,e-vec ,t ,(constant vector-data-disp)))
+                             (set! ,t ,(%inline + ,t (immediate ,(constant ptr-bytes))))
+                             (goto ,Ltop)))))))))
+          (define build-vector-append
+            (lambda (e-vecs)
+              (let loop ([e-vecs e-vecs] [len `(immediate 0)])
+                (cond
+                  [(null? e-vecs)
+                   (do-make-vector len #f)]
+                  [else
+                   (let ([Ltop (make-local-label 'Ltop)]
+                         [d-vec (make-assigned-tmp 'd-vec 'ptr)]
+                         [e-vec (car e-vecs)]
+                         [t (make-assigned-tmp 't 'uptr)]
+                         [e-len (make-assigned-tmp 'e-len 'uptr)])
+                     (bind #t (e-vec)
+                       `(let ([,t ,len]
+                              [,e-len ,(extract-vector-length e-vec)])
+                          (let ([,d-vec ,(loop (cdr e-vecs) (%inline + ,t ,e-len))])
+                            (label ,Ltop
+                                   (if ,(%inline eq? ,e-len (immediate 0))
+                                       ,d-vec
+                                       ,(%seq
+                                         (set! ,e-len ,(%inline - ,e-len (immediate ,(constant ptr-bytes))))
+                                         (set! ,(%mref ,d-vec ,(%inline + ,t ,e-len) ,(constant vector-data-disp))
+                                               ,(%mref ,e-vec ,e-len ,(constant vector-data-disp)))
+                                         (goto ,Ltop))))))))]))))
+          (define-inline 3 vector-copy
+            [(vec) (bind #t (vec)
+                     (build-vector-copy vec `(immediate ,(fix 0)) (extract-vector-length vec)))]
+            [(vec start end) (build-vector-copy vec start end)])
+          (define-inline 3 vector-append
+            [() `(quote ,(vector))]
+            [(vec . vecs) (build-vector-append (cons vec vecs))]))
         (let ()
           (define (valid-length? e-length)
             (constant?
diff --git a/s/primdata.ss b/s/primdata.ss
index 1094e15cf..307e654c4 100644
--- a/s/primdata.ss
+++ b/s/primdata.ss
@@ -1831,8 +1831,9 @@
   (utf-16-codec [sig [() -> (codec)] [(sub-symbol) -> (codec)]] [flags pure true]) ; has optional eness argument
   (utf-16le-codec [sig [() -> (codec)]] [flags pure unrestricted true])
   (utf-16be-codec [sig [() -> (codec)]] [flags pure unrestricted true])
+  (vector-append [sig [(vector ...) -> (vector)]] [flags alloc])
   (vector-cas! [sig [(nonempty-vector sub-index ptr ptr) -> (boolean)]] [flags cptypes2])
-  (vector-copy [sig [(vector) -> (vector)]] [flags alloc safeongoodargs])
+  (vector-copy [sig [(vector) -> (vector)] [(vector sub-index sub-index) -> (vector)]] [flags alloc])
   (vector->immutable-vector [sig [(vector) -> (immutable-vector)]] [flags alloc cp02 safeongoodargs])
   (vector->pseudo-random-generator [sig [(nonempty-vector) -> (pseudo-random-generator)]] [flags])
   (vector->pseudo-random-generator! [sig [(pseudo-random-generator nonempty-vector) -> (void)]] [flags])
diff --git a/s/prims.ss b/s/prims.ss
index 8b2365003..d0452deb9 100644
--- a/s/prims.ss
+++ b/s/prims.ss
@@ -1455,7 +1455,7 @@
 ; not safe; assumes `val` is older than `v`
 (define $stencil-vector-fill-set!
   (lambda (v i val)
-    ($stencil-vector-set! v i val)))
+    ($stencil-vector-fill-set! v i val)))
 
 ; not safe
 (define $record-ref
diff --git a/s/reboot.ss b/s/reboot.ss
index a61c43434..8a8d76501 100644
--- a/s/reboot.ss
+++ b/s/reboot.ss
@@ -529,7 +529,7 @@
 
 (define-primitive ($make-source-oops who . args)
   (($top-level-value 'datum->syntax) (or who ($make-interaction-syntax 'unknown))
-                                     '(error "oops")))
+                                     `(error 'source "oops ~s" '(,who . ,args))))
 
 (define-primitive ($source-warning . args)
   (printf "~s\n" args))