diff --git a/host/chez/driver.janet b/host/chez/driver.janet
index 0404da0..59c0c3a 100644
--- a/host/chez/driver.janet
+++ b/host/chez/driver.janet
@@ -66,6 +66,16 @@
   (def final-scm (emit/emit (backend/analyze-form ctx (in forms (- n 1)))))
   (emit/program def-scm final-scm))
 
+# Drain a pipe to EOF. A single (ev/read pipe N) can return BEFORE the child has
+# flushed everything — a program with a stdout side effect (newline/print) flushes
+# in two writes, and the first ev/read sometimes catches only the first chunk, so
+# the trailing real value is lost (intermittent gate divergence). Loop until EOF.
+(defn- drain [pipe]
+  (def b @"")
+  (var c (ev/read pipe 0x10000))
+  (while c (buffer/push b c) (set c (ev/read pipe 0x10000)))
+  (string b))
+
 (defn run-on-chez
   "Compile `src` and run it on Chez; returns [exit-code stdout stderr]."
   [ctx src &opt scheme-out]
@@ -73,10 +83,10 @@
   (def path (or scheme-out "/tmp/chez-jolt-prog.ss"))
   (spit path prog)
   (def proc (os/spawn ["chez" "--script" path] :p {:out :pipe :err :pipe}))
-  (def out (ev/read (proc :out) 0x100000))
-  (def err (ev/read (proc :err) 0x100000))
+  (def out (drain (proc :out)))
+  (def err (drain (proc :err)))
   (def code (os/proc-wait proc))
-  [code (string/trim (if out (string out) "")) (string/trim (if err (string err) ""))])
+  [code (string/trim out) (string/trim err)])
 
 # --- clojure.core prelude assembly (jolt-9ziu) --------------------------------
 # The -e-capable jolt-chez path: emit EVERY non-macro clojure.core form across
@@ -172,7 +182,7 @@
           path (or scheme-out (string "/tmp/jolt-chez-e-" (os/getpid) ".ss"))]
       (spit path prog)
       (def proc (os/spawn ["chez" "--script" path] :p {:out :pipe :err :pipe}))
-      (def out (ev/read (proc :out) 0x100000))
-      (def err (ev/read (proc :err) 0x100000))
+      (def out (drain (proc :out)))
+      (def err (drain (proc :err)))
       (def code (os/proc-wait proc))
-      [code (string/trim (if out (string out) "")) (string/trim (if err (string err) ""))])))
+      [code (string/trim out) (string/trim err)])))
diff --git a/host/chez/natives-xform.ss b/host/chez/natives-xform.ss
new file mode 100644
index 0000000..5275ac3
--- /dev/null
+++ b/host/chez/natives-xform.ss
@@ -0,0 +1,51 @@
+;; volatiles + sequence / transduce (jolt-cf1q.3, jolt-xjx6) — the transducer
+;; application surface.
+;;
+;; `sequence` and `transduce` are seed natives that were jolt-nil on the prelude.
+;; The stateful transducer arities (take-nth/map-indexed/partition-by/dedupe/
+;; distinct, all overlay) use volatile!/vswap!/vreset!/deref, also unshimmed — so
+;; the whole (sequence xform coll) / (transduce xform f coll) surface crashed.
+;;
+;; Volatiles are a native mutable box (jvol) — the overlay vreset!/vswap! drive a
+;; volatile through jolt.host/ref-put!+get, but a Chez volatile is a record, not a
+;; tagged table, so those overlay versions are overridden natively in
+;; post-prelude.ss. transduce/sequence build on the existing into-xform / reduce-
+;; seq machinery (natives-seq.ss / seq.ss). Loaded after those + atoms.ss (deref).
+
+;; --- volatiles ---------------------------------------------------------------
+(define-record-type jvol (fields (mutable v)) (nongenerative chez-jvol-v1))
+(define (jolt-volatile! x) (make-jvol x))
+(define (jolt-vreset! vol x) (jvol-v-set! vol x) x)
+(define (jolt-vswap! vol f . args)
+  (let ((nv (apply jolt-invoke f (jvol-v vol) args))) (jvol-v-set! vol nv) nv))
+(define (jolt-volatile-pred? x) (jvol? x))
+;; deref reads a volatile too (partition-all/-by transducers @-deref their box).
+(define %xf-deref jolt-deref)
+(set! jolt-deref (lambda (x) (if (jvol? x) (jvol-v x) (%xf-deref x))))
+
+(def-var! "clojure.core" "volatile!" jolt-volatile!)
+(def-var! "clojure.core" "deref" jolt-deref)
+
+;; --- transduce / sequence ----------------------------------------------------
+;; (transduce xform f coll) / (transduce xform f init coll): build the transformed
+;; reducing fn (xform f), reduce it over coll (reduce-seq honors `reduced`), then
+;; run the completion (1-arg) arity. The 3-arg init defaults to (f) — the rf's
+;; 0-arity, e.g. (+) = 0, (conj) = [].
+(define jolt-transduce
+  (case-lambda
+    ((xform f coll) (jolt-transduce xform f (jolt-invoke f) coll))
+    ((xform f init coll)
+     (let* ((xf (jolt-invoke xform f))
+            (res (reduce-seq xf init (jolt-seq coll))))
+       (jolt-invoke xf res)))))
+
+;; (sequence coll) -> a seq; (sequence xform coll) -> coll transformed by xform.
+;; Materialized eagerly through into-xform then seq'd (corpus inputs are finite; a
+;; fully-lazy pull is future work). Honors reduced via into-xform/reduce-seq.
+(define jolt-sequence
+  (case-lambda
+    ((coll) (jolt-seq coll))
+    ((xform coll) (jolt-seq (into-xform (jolt-vector) xform coll)))))
+
+(def-var! "clojure.core" "transduce" jolt-transduce)
+(def-var! "clojure.core" "sequence" jolt-sequence)
diff --git a/host/chez/post-prelude.ss b/host/chez/post-prelude.ss
index 88ea85a..1826bf7 100644
--- a/host/chez/post-prelude.ss
+++ b/host/chez/post-prelude.ss
@@ -13,3 +13,9 @@
 ;; override.)
 (def-var! "clojure.core" "char?" jolt-char-pred?)
 (def-var! "clojure.core" "atom?" jolt-atom?)
+;; volatiles: a Chez volatile is a jvol record, but the overlay vreset!/vswap!/
+;; volatile? drive it via jolt.host/ref-put!+get / :jolt/type (tagged-table only).
+;; Override with the native versions (defined in natives-xform.ss).
+(def-var! "clojure.core" "vreset!" jolt-vreset!)
+(def-var! "clojure.core" "vswap!" jolt-vswap!)
+(def-var! "clojure.core" "volatile?" jolt-volatile-pred?)
diff --git a/host/chez/rt.ss b/host/chez/rt.ss
index 1de77d9..7eb4834 100644
--- a/host/chez/rt.ss
+++ b/host/chez/rt.ss
@@ -212,3 +212,8 @@
 ;; iterate/cycle/dedupe/take-nth/keep/interpose/reductions/tree-seq/lazy-cat).
 ;; Loaded LAST so %ls-seq captures the fully-extended (sorted-aware) jolt-seq.
 (load "host/chez/lazy-bridge.ss")
+
+;; volatiles + sequence / transduce (jolt-xjx6, Phase 2): native volatile boxes +
+;; the transduce/sequence entry points over into-xform/reduce-seq. After
+;; natives-seq.ss (into-xform), seq.ss (reduce-seq) + atoms.ss (deref).
+(load "host/chez/natives-xform.ss")
diff --git a/test/chez/run-corpus-prelude.janet b/test/chez/run-corpus-prelude.janet
index 5cf0077..f298140 100644
--- a/test/chez/run-corpus-prelude.janet
+++ b/test/chez/run-corpus-prelude.janet
@@ -176,8 +176,12 @@
 # referential lazy-cat (fib) stays productive. Unblocks repeat/iterate/cycle/
 # dedupe/take-nth/keep/interpose/reductions/map-indexed/distinct/interleave/
 # tree-seq->flatten/partition-all/lazy-cat) 1886.
+# Phase 2 inc H (jolt-xjx6: native volatiles (jvol) + sequence/transduce over the
+# existing into-xform/reduce-seq — unblocks (sequence xform coll), (transduce
+# xform f coll), and the stateful transducer xforms take-nth/map-indexed/
+# partition-by that drive a volatile) 1898.
 # Strided runs scale down.
-(def base-floor (scan-number (or (os/getenv "JOLT_CHEZ_PRELUDE_FLOOR") "1886")))
+(def base-floor (scan-number (or (os/getenv "JOLT_CHEZ_PRELUDE_FLOOR") "1898")))
 (def floor (if (os/getenv "JOLT_CORPUS_LIMIT") 0 base-floor))
 (when (or (> (length diverged) 0) (< pass floor))
   (printf "REGRESSION: pass %d < floor %d or %d new divergence(s)" pass floor (length diverged)))