diff --git a/jolt-core/clojure/core/40-lazy.clj b/jolt-core/clojure/core/40-lazy.clj
new file mode 100644
index 0000000..7254b95
--- /dev/null
+++ b/jolt-core/clojure/core/40-lazy.clj
@@ -0,0 +1,114 @@
+;; clojure.core — lazy tier. Canonical CLJS-based lazy seq fns.
+;; Loaded after 30-macros.clj, so lazy-seq macro is available.
+;;
+;; Each fn ported from CLJS core.cljs, stripped of chunked-seq branches.
+
+;; --- distinct ---
+(defn distinct [coll]
+  (let [step (fn step [xs seen]
+               (lazy-seq
+                 ((fn [[f :as xs] seen]
+                    (when-let [s (seq xs)]
+                      (if (contains? seen f)
+                        (recur (rest s) seen)
+                        (cons f (step (rest s) (conj seen f))))))
+                   xs seen)))]
+    (step coll #{})))
+
+;; --- dedupe (lazy, canonical) ---
+(defn dedupe [coll]
+  (let [step (fn step [s prev]
+               (lazy-seq
+                 (let [s (seq s)]
+                   (when s
+                     (let [x (first s)]
+                       (if (= x prev)
+                         (step (rest s) prev)
+                         (cons x (step (rest s) x))))))))]
+    (let [s (seq coll)]
+      (if s
+        (lazy-seq (cons (first s) (step (rest s) (first s))))
+        ()))))
+
+;; --- keep ---
+(defn keep
+  ([f]
+   (fn [rf]
+     (fn ([] (rf)) ([result] (rf result))
+       ([result input]
+        (let [v (f input)]
+          (if (nil? v) result (rf result v)))))))
+  ([f coll]
+   (lazy-seq
+    (when-let [s (seq coll)]
+      (let [x (f (first s))]
+        (if (nil? x)
+          (keep f (rest s))
+          (cons x (keep f (rest s)))))))))
+
+;; --- keep-indexed ---
+(defn keep-indexed
+  ([f]
+   (fn [rf]
+     (let [ia (volatile! -1)]
+       (fn ([] (rf)) ([result] (rf result))
+         ([result input]
+          (let [i (vswap! ia inc)
+                v (f i input)]
+            (if (nil? v) result (rf result v))))))))
+  ([f coll]
+   (letfn [(keepi [idx coll]
+             (lazy-seq
+               (when-let [s (seq coll)]
+                 (let [x (f idx (first s))]
+                   (if (nil? x)
+                     (keepi (inc idx) (rest s))
+                     (cons x (keepi (inc idx) (rest s))))))))]
+     (keepi 0 coll))))
+
+;; --- map-indexed ---
+(defn map-indexed
+  ([f]
+   (fn [rf]
+     (let [i (volatile! -1)]
+       (fn ([] (rf)) ([result] (rf result))
+         ([result input] (rf result (f (vswap! i inc) input)))))))
+  ([f coll]
+   (letfn [(mapi [idx coll]
+             (lazy-seq
+               (when-let [s (seq coll)]
+                 (cons (f idx (first s)) (mapi (inc idx) (rest s))))))]
+     (mapi 0 coll))))
+
+;; --- cycle ---
+(defn cycle [coll]
+  (if-let [vals (seq coll)]
+    (let [n (count vals)]
+      (letfn [(cstep [i]
+                (lazy-seq
+                  (cons (nth vals (mod i n)) (cstep (inc i)))))]
+        (cstep 0)))
+    ()))
+
+;; --- repeatedly ---
+(defn repeatedly
+  ([f] (lazy-seq (cons (f) (repeatedly f))))
+  ([n f] (take n (repeatedly f))))
+
+;; --- repeat ---
+(defn repeat
+  ([x] (lazy-seq (cons x (repeat x))))
+  ([n x] (take n (repeat x))))
+
+;; --- iterate ---
+(defn iterate [f x]
+  (lazy-seq (cons x (iterate f (f x)))))
+
+
+;; --- partition-all ---
+(defn partition-all
+  ([n coll] (partition-all n n coll))
+  ([n step coll]
+   (lazy-seq
+    (when-let [s (seq coll)]
+      (cons (take n s) (partition-all n step (nthrest coll step)))))))
diff --git a/src/jolt/api.janet b/src/jolt/api.janet
index 08d6112..299d460 100644
--- a/src/jolt/api.janet
+++ b/src/jolt/api.janet
@@ -50,7 +50,8 @@
    {:ns "clojure.core.00-kernel" :kernel true}
    {:ns "clojure.core.10-seq"    :kernel false}
    {:ns "clojure.core.20-coll"   :kernel false}
-   {:ns "clojure.core.30-macros" :kernel false}])
+   {:ns "clojure.core.30-macros" :kernel false}
+   {:ns "clojure.core.40-lazy"   :kernel false}])
 
 (defn- eval-overlay-source [ctx src]
   (var s src)
diff --git a/src/jolt/compiler.janet b/src/jolt/compiler.janet
index 7af717a..d700472 100644
--- a/src/jolt/compiler.janet
+++ b/src/jolt/compiler.janet
@@ -96,6 +96,7 @@
     "drop" "core-drop"
     "take-while" "core-take-while"
     "drop-while" "core-drop-while"
+    "interpose" "core-interpose"
     "nth" "core-nth"
     "mapcat" "core-mapcat"
     "apply" "core-apply"
diff --git a/src/jolt/core.janet b/src/jolt/core.janet
index c252abc..b9509e2 100644
--- a/src/jolt/core.janet
+++ b/src/jolt/core.janet
@@ -1257,31 +1257,6 @@
           (sort-by keyfn arr))
         (tuple/slice (tuple ;arr))))))
 
-(defn core-distinct [coll]
-  (if (nil? coll) @[]
-  (if (lazy-seq? coll)
-    (do
-      (var seen @{})
-      (defn dstep [c]
-        (fn []
-          (var cur c) (var found false) (var result nil)
-          (while (and (not found) (not (seq-done? cur)))
-            (let [x (ls-first cur)]
-              (set cur (ls-rest cur))
-              (when (nil? (seen x))
-                (put seen x true)
-                (set found true)
-                (set result x))))
-          (if found @[result (dstep cur)] nil)))
-      (make-lazy-seq (dstep coll)))
-    (do
-      (var seen @{})
-      (var result @[])
-      (each x (realize-for-iteration coll)
-        (if (nil? (seen x))
-          (do (put seen x true) (array/push result x))))
-      (if (jvec? coll) (make-vec result) result)))))
-
 # group-by / frequencies now live in the Clojure collection tier
 # (core/20-coll.clj).
 
@@ -1317,32 +1292,6 @@
           (+= i step))
         result))))
 
-
-(defn core-partition-all [n coll]
-  (if (lazy-seq? coll)
-    (do
-      (defn pstep [c]
-        (fn []
-          (if (seq-done? c) nil
-            (do
-              (var part @[]) (var cur c) (var i 0)
-              (while (and (< i n) (not (seq-done? cur)))
-                (array/push part (ls-first cur))
-                (set cur (ls-rest cur))
-                (++ i))
-              @[(tuple/slice (tuple ;part)) (pstep cur)]))))
-      (make-lazy-seq (pstep coll)))
-    (let [c (realize-for-iteration coll)]
-      (var result @[]) (var i 0)
-      (while (< i (length c))
-        (var part @[]) (var j 0)
-        (while (and (< j n) (< (+ i j) (length c)))
-          (array/push part (in c (+ i j))) (++ j))
-        (array/push result (tuple/slice (tuple ;part)))
-        (+= i n))
-      result)))
-
-
 (defn core-keep-indexed [f coll]
   (def f (as-fn f))
   (if (lazy-seq? coll)
@@ -1379,14 +1328,6 @@
           (each x c (array/push result (f i x)) (++ i))
           (tuple/slice (tuple ;result)))))))
 
-(defn core-cycle [coll]
-  (let [c (realize-for-iteration coll)]
-    (if (= 0 (length c))
-      (make-lazy-seq (fn [] nil))
-      (do
-        (defn cstep [i] (fn [] @[(in c (% i (length c))) (cstep (+ i 1))]))
-        (make-lazy-seq (cstep 0))))))
-
 # reduce-kv now lives in the Clojure collection tier (core/20-coll.clj).
 
 # pop is defined only on stacks (vectors -> last end, lists -> front); Clojure
@@ -1432,16 +1373,6 @@
           (+= i step))
         (tuple/slice (tuple ;result))))))
 
-(defn core-repeat
-  "(repeat x) -> infinite lazy seq of x; (repeat n x) -> n copies of x."
-  [a & rest]
-  (if (= 0 (length rest))
-    (do (defn rstep [] (fn [] @[a (rstep)])) (make-lazy-seq (rstep)))
-    (let [n a x (in rest 0)]
-      (var result @[]) (var i 0)
-      (while (< i n) (array/push result x) (++ i))
-      result)))
-
 (defn core-iterate [f x]
   "Lazy infinite sequence x, (f x), (f (f x)), ..."
   (defn istep [v] (fn [] @[v (istep (f v))]))
@@ -2337,6 +2268,7 @@
     (fn [& a] (case (length a) 0 (rf) 1 (rf (a 0))
                 (if started (rf (rf (a 0) sep) (a 1))
                   (do (set started true) (rf (a 0) (a 1))))))))
+
 (defn core-interpose [sep & rest]
   (if (= 0 (length rest)) (td-interpose sep)
     (let [coll (in rest 0)]
@@ -2816,11 +2748,7 @@
     "get-in" core-get-in
     "contains?" core-contains?
     "count" core-count
-    "partition-all" core-partition-all
-    "keep-indexed" core-keep-indexed
-    "map-indexed" core-map-indexed
-    "cycle" core-cycle
-    "pop" core-pop
+                    "pop" core-pop
     "format" core-format
     "rand-int" core-rand-int
     "trampoline" core-trampoline
@@ -2901,10 +2829,8 @@
     "hash-unordered-coll" core-hash-unordered-coll
     "prefers" core-prefers
     "random-uuid" core-random-uuid
-    "interpose" core-interpose
-    "mapcat" core-mapcat
-    "keep" core-keep
-    "find" core-find
+        "mapcat" core-mapcat
+        "find" core-find
     "transduce" core-transduce
     "sequence" core-sequence
     "eduction" core-sequence
@@ -2941,13 +2867,10 @@
     "nth" core-nth
     "sort" core-sort
     "sort-by" core-sort-by
-    "distinct" core-distinct
-    "partition" core-partition
+        "partition" core-partition
+        "interpose" core-interpose
     "range" core-range
-    "repeat" core-repeat
-    "iterate" core-iterate
-    "repeatedly" core-repeatedly
-    "identity" core-identity
+                "identity" core-identity
     "constantly" core-constantly
     "complement" core-complement
     "comp" core-comp