diff --git a/jolt-core/jolt/reader.clj b/jolt-core/jolt/reader.clj
new file mode 100644
index 0000000..1b3c5bf
--- /dev/null
+++ b/jolt-core/jolt/reader.clj
@@ -0,0 +1,195 @@
+(ns jolt.reader
+  "Portable Clojure reader: source text -> reader forms (Chez Phase 3, jolt-cf1q.4).
+
+  The no-Janet replacement for src/jolt/reader.janet. All the lexing/parsing LOGIC
+  is portable Clojure; form CONSTRUCTION and string->number parsing delegate to the
+  jolt.host contract (form-make-symbol/char, form-char-from-name, form-scan-number)
+  — a Clojure source file cannot write a {:jolt/type :symbol} literal (it parses as
+  a tagged reader form), and the concrete form representation is the host's to own.
+  Same split the analyzer uses for the form-* readers. Once cross-compiled this runs
+  ON Chez so compile-from-source needs no Janet reader.
+
+  Positions are CHARACTER indices (the Janet reader uses byte indices); for ASCII
+  source they coincide, and form VALUES are identical either way — the parity gate
+  compares values, not positions.
+
+  INCREMENT 5a (jolt-50xx): the ATOM layer — whitespace/comments, symbols (+ nil/
+  true/false), keywords, strings, numbers (sign/hex/radix/ratio/fractional/
+  exponent, trailing N/M), characters. Collections, quote/deref/meta, and dispatch
+  (#) land in 5b/5c (they throw not-yet-ported so a hit is loud)."
+  (:require [clojure.string :as str]
+            [jolt.host :refer [form-make-symbol form-make-char form-char-from-name
+                               form-scan-number]]))
+
+;; Source access by CHARACTER codepoint, mirroring the Janet reader's byte access
+;; (identical for ASCII). cp = codepoint at i; len = character count.
+(defn- cp [s i] (int (nth s i)))
+(defn- len [s] (count s))
+
+(defn- whitespace? [c] (or (= c 32) (= c 9) (= c 10) (= c 13) (= c 44)))  ; space tab nl cr ,
+(defn- digit? [c] (and (>= c 48) (<= c 57)))
+(defn- hex-digit? [c]
+  (or (digit? c) (and (>= c 65) (<= c 70)) (and (>= c 97) (<= c 102))))
+(defn- symbol-start? [c]
+  (or (and (>= c 65) (<= c 90)) (and (>= c 97) (<= c 122))
+      (= c 42) (= c 43) (= c 33) (= c 95) (= c 45) (= c 63) (= c 46)
+      (= c 60) (= c 62) (= c 61) (= c 38) (= c 124) (= c 36) (= c 37) (= c 47)))
+(defn- symbol-char? [c]
+  (or (symbol-start? c) (digit? c) (= c 35) (= c 39) (= c 58)))  ; + # ' :
+
+(defn- skip-whitespace [s pos]
+  (if (and (< pos (len s)) (whitespace? (cp s pos)))
+    (recur s (inc pos))
+    pos))
+
+(defn- read-until-newline [s pos]
+  (if (or (>= pos (len s)) (= (cp s pos) 10)) pos (recur s (inc pos))))
+
+;; --- symbols -----------------------------------------------------------------
+(defn- read-symbol-name [s pos end]
+  (if (and (< end (len s)) (symbol-char? (cp s end))) (recur s pos (inc end)) end))
+
+(defn- read-symbol* [s pos]
+  (let [end (read-symbol-name s pos pos)]
+    (when (= end pos)
+      (throw (ex-info (str "Unrecognized character: " (char (cp s pos))) {})))
+    (let [nm (subs s pos end)]
+      (cond
+        (= nm "nil") [nil end]
+        (= nm "true") [true end]
+        (= nm "false") [false end]
+        :else [(form-make-symbol nm) end]))))
+
+;; --- keywords ----------------------------------------------------------------
+(defn- read-keyword-name [s pos end]
+  (if (and (< end (len s)) (symbol-char? (cp s end))) (recur s pos (inc end)) end))
+
+(defn- read-keyword* [s pos]
+  ;; pos is at the first colon; ::foo is treated as :foo (no auto-resolution),
+  ;; matching the Janet reader.
+  (let [start (if (and (< (inc pos) (len s)) (= (cp s (inc pos)) 58)) (+ pos 2) (inc pos))
+        end (read-keyword-name s start start)]
+    [(keyword (subs s start end)) end]))
+
+;; --- strings -----------------------------------------------------------------
+(defn- escape-char [c]
+  (cond (= c 110) "\n" (= c 116) "\t" (= c 114) "\r" (= c 92) "\\" (= c 34) "\""
+        :else (str (char c))))
+
+(defn- read-string* [s pos]
+  ;; pos at opening double-quote
+  (loop [p (inc pos) acc []]
+    (when (>= p (len s)) (throw (ex-info "Unterminated string" {})))
+    (let [c (cp s p)]
+      (cond
+        (= c 92) (let [np (inc p)]
+                   (when (>= np (len s)) (throw (ex-info "Unterminated escape" {})))
+                   (recur (+ p 2) (conj acc (escape-char (cp s np)))))
+        (= c 34) [(apply str acc) (inc p)]
+        :else (recur (inc p) (conj acc (str (char c))))))))
+
+;; --- numbers -----------------------------------------------------------------
+(defn- read-digits [s pos end]
+  (if (and (< end (len s)) (digit? (cp s end))) (recur s pos (inc end)) end))
+(defn- read-hex-digits [s pos end]
+  (if (and (< end (len s)) (hex-digit? (cp s end))) (recur s pos (inc end)) end))
+
+;; Value of an alphanumeric digit for radix parsing (0-9, a-z/A-Z = 10-35).
+(defn- radix-digit-val [c]
+  (cond
+    (and (>= c 48) (<= c 57)) (- c 48)
+    (and (>= c 97) (<= c 122)) (+ 10 (- c 97))
+    (and (>= c 65) (<= c 90)) (+ 10 (- c 65))
+    :else nil))
+(defn- read-alnum [s pos end]
+  (if (and (< end (len s)) (radix-digit-val (cp s end))) (recur s pos (inc end)) end))
+
+(defn- read-exponent [s end]
+  ;; if s[end] is e/E (optionally signed) followed by digits, return index past it
+  (if (and (< end (len s)) (let [c (cp s end)] (or (= c 101) (= c 69))))
+    (let [p (if (and (< (inc end) (len s)) (let [c (cp s (inc end))] (or (= c 43) (= c 45))))
+              (+ end 2) (inc end))
+          de (read-digits s p p)]
+      (if (> de p) de end))
+    end))
+
+;; Jolt has no bignum/ratio: N (bigint) / M (bigdec) suffixes read as the plain
+;; number, a ratio a/b reads as the double quotient, radixed ints by base.
+(defn- read-number* [s pos]
+  (let [length (len s)
+        neg (and (< pos length) (= (cp s pos) 45))
+        start (if neg (inc pos) pos)
+        hex? (and (< (inc start) length) (= (cp s start) 48)
+                  (let [c1 (cp s (inc start))] (or (= c1 120) (= c1 88))))]  ; 0x / 0X
+    (if hex?
+      (let [hs (+ start 2) he (read-hex-digits s hs hs)]
+        (when (= he hs) (throw (ex-info "Expected hex digits" {})))
+        (let [he2 (if (and (< he length) (= (cp s he) 78)) (inc he) he)   ; trailing N
+              val (form-scan-number (str "0x" (subs s hs he)))]
+          [(if neg (- val) val) he2]))
+      (let [iend (read-digits s start start)]
+        (when (= iend start) (throw (ex-info "Expected number" {})))
+        (cond
+          ;; radix integer <base>r<digits>
+          (and (< iend length) (let [c (cp s iend)] (or (= c 114) (= c 82))))
+          (let [base (form-scan-number (subs s start iend))
+                ds (inc iend) de (read-alnum s ds ds)]
+            (when (= de ds) (throw (ex-info "Expected radix digits" {})))
+            (let [acc (reduce (fn [a i] (+ (* a base) (radix-digit-val (cp s i)))) 0 (range ds de))]
+              [(if neg (- acc) acc) de]))
+          ;; ratio <int>/<int> (only when a digit follows the slash)
+          (and (< (inc iend) length) (= (cp s iend) 47) (digit? (cp s (inc iend))))
+          (let [ds (inc iend) de (read-digits s ds ds)
+                numr (form-scan-number (subs s start iend))
+                den (form-scan-number (subs s ds de))]
+            [(if neg (- (/ numr den)) (/ numr den)) de])
+          ;; fractional and/or exponent, optional trailing N/M
+          :else
+          (let [frac-end (if (and (< iend length) (= (cp s iend) 46))
+                           (let [fs (inc iend) fe (read-digits s fs fs)]
+                             (when (= fe fs) (throw (ex-info "Expected digit after ." {})))
+                             fe)
+                           iend)
+                exp-end (read-exponent s frac-end)
+                val (form-scan-number (subs s start exp-end))
+                fin (if (and (< exp-end length) (let [c (cp s exp-end)] (or (= c 78) (= c 77))))
+                      (inc exp-end) exp-end)]
+            [(if neg (- val) val) fin]))))))
+
+;; --- characters --------------------------------------------------------------
+(defn- read-char-name-end [s pos]
+  (if (and (< pos (len s)) (symbol-char? (cp s pos))) (recur s (inc pos)) pos))
+
+(defn- read-char* [s pos]
+  (when (>= (inc pos) (len s)) (throw (ex-info "unexpected end of input after \\" {})))
+  (let [end (read-char-name-end s (inc pos))]
+    (if (= end (inc pos))
+      ;; a non-symbol char right after \ is a one-character literal of itself
+      [(form-make-char (cp s (inc pos))) (+ pos 2)]
+      [(form-char-from-name (subs s (inc pos) end)) end])))
+
+;; --- dispatcher --------------------------------------------------------------
+(defn- number-start? [s pos c]
+  (or (digit? c)
+      (and (= c 45) (< (inc pos) (len s)) (digit? (cp s (inc pos))))
+      (and (= c 43) (< (inc pos) (len s)) (digit? (cp s (inc pos))))))
+
+(defn read-form [s pos]
+  (let [pos (skip-whitespace s pos)]
+    (if (>= pos (len s))
+      [nil pos]
+      (let [c (cp s pos)]
+        (cond
+          (= c 59) (read-form s (read-until-newline s pos))   ; ; comment: skip + reread
+          (= c 34) (read-string* s pos)
+          (= c 58) (read-keyword* s pos)
+          (= c 92) (read-char* s pos)
+          (number-start? s pos c) (read-number* s pos)
+          (symbol-start? c) (read-symbol* s pos)
+          :else (throw (ex-info (str "read-form: not yet ported (inc 5a atoms): '"
+                                     (char c) "' (" c ")") {})))))))
+
+(defn read-one
+  "Read the first form of `s` (skipping leading trivia). Returns the form."
+  [s]
+  (first (read-form s 0)))
diff --git a/src/jolt/host_iface.janet b/src/jolt/host_iface.janet
index 364b3d9..693e402 100644
--- a/src/jolt/host_iface.janet
+++ b/src/jolt/host_iface.janet
@@ -282,8 +282,24 @@
 (defn h-record-shapes [ctx]
   (or (get (ctx :env) :record-shapes) @{}))
 
+# Reader form CONSTRUCTORS (Chez Phase 3, jolt-cf1q.4). The portable Clojure
+# reader (jolt.reader) holds all the LEXING/PARSING logic but must DELEGATE form
+# construction to the host — a Clojure source file cannot write a {:jolt/type
+# :symbol} literal (it parses as a tagged reader form, CLAUDE.md), and the
+# concrete representation (Janet struct/array/tuple here; something else on Chez)
+# is the host's to own. Same split the analyzer already uses for form-* readers.
+(defn h-make-symbol [name] (rdr/make-symbol name))
+(defn h-make-char [code] (make-char code))
+(defn h-char-from-name [name] (char-from-name name))
+# Parse a numeric literal substring to a number. The reader keeps the radix/ratio/
+# sign/exponent LOGIC portable; only the final string->number bottoms out here
+# (Janet scan-number; Chez string->number). Returns nil on a non-number.
+(defn h-scan-number [str] (scan-number str))
+
 (def- exports
   {"form-sym?" h-sym? "form-sym-name" h-sym-name "form-sym-ns" h-sym-ns
+   "form-make-symbol" h-make-symbol "form-make-char" h-make-char
+   "form-char-from-name" h-char-from-name "form-scan-number" h-scan-number
    "ref-put!" h-ref-put!
    "ref-get" h-ref-get
    "tagged-table" h-tagged-table
diff --git a/test/chez/reader-parity.janet b/test/chez/reader-parity.janet
new file mode 100644
index 0000000..62caa68
--- /dev/null
+++ b/test/chez/reader-parity.janet
@@ -0,0 +1,66 @@
+# Chez Phase 3 inc 5a (jolt-50xx) — value-parity gate for the PORTABLE Clojure
+# reader (jolt.reader) vs the Janet seed reader (src/jolt/reader.janet, oracle).
+#
+# jolt.reader holds the lexing/parsing LOGIC in portable Clojure and delegates
+# form construction + number parsing to the jolt.host contract. Here it runs
+# interpreted ON THE JANET HOST (loaded via bootstrap-load-source); each input is
+# read by BOTH readers and the resulting FORMS compared with jolt's own = (so the
+# representation, host-built either way, matches structurally). Positions differ
+# (char vs byte indices) and are not compared.
+#
+#   janet test/chez/reader-parity.janet      (from repo root)
+(import ../../src/jolt/api :as api)
+(import ../../src/jolt/backend :as backend)
+(import ../../src/jolt/reader :as r)
+(import ../../src/jolt/types_ctx :as tctx)
+(import ../../src/jolt/types_ns :as tns)
+(import ../../src/jolt/types_var :as tvar)
+(import ../../src/jolt/core :as core)
+
+(var total 0) (var fails 0)
+(defn ok [name pred &opt extra]
+  (++ total)
+  (if pred (printf "ok: %s" name)
+    (do (++ fails) (printf "FAIL: %s   %s" name (or extra "")))))
+
+(def ctx (api/init {:compile? true}))
+(def src (get (get (ctx :env) :embedded-sources) "jolt.reader"))
+(assert src "jolt.reader not embedded (check stdlib_embed collect)")
+(backend/bootstrap-load-source ctx "jolt.reader" src)
+(def read-one (tvar/var-get (tns/ns-find (tctx/ctx-find-ns ctx "jolt.reader") "read-one")))
+(assert read-one "jolt.reader/read-one not found")
+
+# jolt's own value equality (the host =), the same comparator the corpus gate uses.
+(defn jeq [a b] (core/jolt-equal? a b))
+
+(defn check [input]
+  (def w (protect (in (r/parse-next input) 0)))   # Janet seed reader (oracle)
+  (def g (protect (read-one input)))               # portable Clojure reader
+  (cond
+    # both readers throw on the same input = faithful parity (e.g. the +N latent
+    # bug, jolt-if19 — reader.janet dispatches +digit to read-number but never
+    # strips the +, so "+5" errors; the port reproduces it).
+    (and (not (w 0)) (not (g 0))) (ok input true)
+    (not (w 0)) (ok input false (string "janet threw, clj didn't: clj=" (string/format "%p" (g 1))))
+    (not (g 0)) (ok input false (string "clj threw, janet ok: " (string (g 1))))
+    (ok input (jeq (w 1) (g 1))
+        (string "clj=" (string/format "%p" (g 1)) " janet=" (string/format "%p" (w 1))))))
+
+# --- inc 5a: atoms -------------------------------------------------------------
+# nil / bool
+(each i ["nil" "true" "false"] (check i))
+# symbols (plain, ns'd, punctuation, special chars)
+(each i ["foo" "foo-bar" "my.ns/bar" "+" "-" "*" "->" "<=" "some?" "a1" "x'" "ns/+"] (check i))
+# keywords
+(each i [":a" ":foo-bar" ":my.ns/key" "::auto" ":a1" ":+"] (check i))
+# strings (escapes)
+(each i [`"hello"` `"with space"` `"tab\there"` `"nl\nhere"` `"q\"q"` `"back\\slash"` `""`] (check i))
+# integers / signs / hex / radix
+(each i ["0" "42" "-7" "+5" "123456" "0xFF" "0x10" "-0xff" "2r1010" "16rFF" "36rZ" "8r17"] (check i))
+# floats / exponent / ratio / N|M suffix
+(each i ["3.14" "-2.5" "0.0" "1e10" "1.5e-3" "2E5" "10N" "3.14M" "1/2" "-3/4" "22/7"] (check i))
+# characters
+(each i [`\a` `\Z` `\0` `\newline` `\tab` `\space` `\return` `\\` `\(` `\{` `\%` `A` `\o101`] (check i))
+
+(printf "\n%d/%d ok" (- total fails) total)
+(when (> fails 0) (os/exit 1))