diff --git a/Makefile b/Makefile
index 72c0b5e..9d34ba2 100644
--- a/Makefile
+++ b/Makefile
@@ -4,7 +4,7 @@
 # build step. `make test` is the full gate. `make remint` rebuilds the seed after a
 # source change.
 
-.PHONY: test ci values corpus unit smoke selfhost sci certify ffi transient remint
+.PHONY: test ci values corpus unit smoke buildsmoke selfhost sci certify ffi transient remint
 
 # Full gate (dev machine). Includes the self-host byte-fixpoint, which only holds
 # on the same Chez that minted the seed.
@@ -15,7 +15,7 @@ test: selfhost ci
 # lockfile) — it RUNS correctly on any Chez, but `selfhost` rebuilds it and a
 # different Chez version may emit byte-different (gensym/order) output, so the
 # byte-fixpoint is a dev-machine check, not a CI one (jolt-8479).
-ci: values corpus unit smoke sci ffi transient certify
+ci: values corpus unit smoke buildsmoke sci ffi transient certify
 	@echo "OK: CI gates passed"
 
 # Self-host fixpoint: bootstrap.ss rebuild == checked-in seed.
@@ -38,6 +38,10 @@ unit:
 smoke:
 	@sh host/chez/smoke.sh
 
+# `jolt build` produces a working standalone binary.
+buildsmoke:
+	@sh host/chez/build-smoke.sh
+
 # SCI conformance: load borkdude/sci's source through joltc (floor-gated).
 sci:
 	@chez --script host/chez/run-sci.ss
diff --git a/docs/rfc/0007-compilation-modes-and-binary-output.md b/docs/rfc/0007-compilation-modes-and-binary-output.md
new file mode 100644
index 0000000..53ee2b3
--- /dev/null
+++ b/docs/rfc/0007-compilation-modes-and-binary-output.md
@@ -0,0 +1,186 @@
+# RFC 0007 — Compilation modes and binary output
+
+- **Status**: Draft. No code yet; this fixes the design before Phase 4 work
+  (beads `jolt-cf1q.5`) starts.
+- **Champions**: jolt maintainers
+- **Created**: 2026-06-22
+
+## Summary
+
+Give jolt a `jolt build` command that emits a standalone executable, and a
+three-mode model that trades dynamism for speed:
+
+- **dev** — open/indirect linking, redefinition works, no perf focus. What
+  `repl`/`-e`/`nrepl` already are.
+- **release** (default for a built program) — direct-linked, closed-world,
+  per-namespace inference. Fast, still a recognizable Clojure runtime.
+- **optimized** — whole-program inference, `fl*`/`fx*` typed emission, Chez
+  whole-program optimization. Fastest, sacrifices dynamic redefinition.
+
+All three already have their machinery in the tree — the inference and inline
+passes were ported into `jolt-core/jolt/passes/`. What is missing is (a) a code
+path that writes emitted Scheme to disk and AOT-compiles it instead of
+eval'ing it in process, and (b) a switch that turns the dormant passes on. This
+RFC specifies both.
+
+## Motivation
+
+The Janet host could produce binaries (`jolt uberscript` with dead-code
+elimination, `jolt cgen-build` for a single native binary). The Chez rehost
+dropped that machinery with the Janet host — it was Janet-specific (IR→C made
+sense when the host was Janet). On Chez the natural target is Chez's own native
+compiler, so the old emitters were deleted rather than re-pointed.
+
+The result today: `bin/joltc` only ever loads the checked-in seed and
+compile-evals in process. `jolt.main/-main` dispatches `run / -M / -A / repl /
+nrepl / task` and nothing else. There is no way to ship an app as a binary, and
+the optimization passes are inert — `jolt.host/inline-enabled?` is a stub
+returning `#f` (`host/chez/host-contract.ss:283`), so every call links
+indirectly and nothing inlines. Jolt on Chez runs only in what this RFC calls
+dev mode.
+
+The passes themselves survived intact:
+
+- `jolt/passes/types.clj` — structural collection-type inference (RFC 0005) +
+  success-type checking (RFC 0006).
+- `jolt/passes/inline.clj` — inline + flatten-lets + scalar-replace, already
+  gated "direct-link only".
+- `jolt/passes/fold.clj` — const-fold, including predicate folding.
+
+So this is not a port of lost code. It is wiring: a build front-end, a
+file-emitting back-end path, and a mode switch over passes that already exist.
+
+## The three modes
+
+| Mode | Linking | Inference | Redefinition | Driver |
+|---|---|---|---|---|
+| **dev** | indirect (var-deref per call) | off | yes | `repl`, `-e`, `nrepl`, `run` of a file by default |
+| **release** | direct, closed-world | per-namespace | no (closed world) | `jolt build` default |
+| **optimized** | direct + whole-program | whole-program fixpoint, `fl*`/`fx*` | no | `jolt build --opt` / `-M`-style entry |
+
+The modes are points on one axis (how much the back end may assume is fixed),
+not three code paths. Each mode is a setting of two independent knobs the passes
+already understand:
+
+- **direct-link?** — may a call to a var compile to a direct procedure
+  reference instead of a `var-deref`? Enables inlining and call-site folding.
+  Opt-out is per-target: a `^:redef` or `^:dynamic` var always links indirect.
+- **whole-program?** — does inference see the whole reachable program at once
+  (closed world), so a record param's callers in other namespaces are visible
+  and its field reads specialize? Without it, inference is per-namespace and a
+  cross-ns param de-specializes to `:any` (the cross-ns penalty documented in
+  the `cross-ns-param-penalty` memory; declared `^RecordType` hints are the
+  open-world escape hatch).
+
+```
+dev:        direct-link? = false   whole-program? = false
+release:    direct-link? = true    whole-program? = false
+optimized:  direct-link? = true    whole-program? = true
+```
+
+`fl*`/`fx*` typed emission (unchecked flonum/fixnum Scheme ops) rides on
+optimized: only whole-program inference proves the types that make dropping the
+numeric-tower dispatch sound. Release keeps the tower.
+
+## CLI surface
+
+```
+jolt build [-m NS | FILE] [-o OUT] [--opt] [--dev]
+```
+
+- Resolves `deps.edn` exactly as `run` does (reuse `jolt.deps`).
+- Default mode is **release**. `--opt` selects optimized; `--dev` builds an
+  unoptimized binary (useful to ship a debuggable build, not for the REPL).
+- `-o` names the output (default the entry ns / file stem).
+- Output is a single executable: a Chez boot file plus the compiled program,
+  launched by a thin wrapper, or a fully linked image where the platform allows.
+  App libraries are baked in — no source roots needed at runtime.
+
+Env opt-outs for the build (mirrors the Janet knobs, now keyed off the mode
+rather than the run): `JOLT_NO_DIRECT_LINK` forces open linking even in a build,
+`JOLT_NO_WHOLE_PROGRAM` keeps direct-link but per-namespace, `JOLT_WHOLE_PROGRAM=1`
+forces whole-program. These already name the two knobs above.
+
+## Emission pipeline
+
+The in-process spine today (`host/chez/compile-eval.ss`) is, per form:
+
+```
+source → read → analyze (→ IR) → emit (→ Scheme string) → (eval (read …))
+```
+
+`jolt build` keeps everything up to `emit` and replaces the per-form `eval` with
+accumulate-then-compile:
+
+1. **Assemble the program.** Starting from the entry ns's `-main`, load the
+   transitive `require` graph (the loader already does this) and collect every
+   reachable top-level form, in dependency order, with its compile namespace.
+2. **Dead-code elimination.** Re-target the uberscript DCE idea: compute
+   reachability from `-main` plus non-prunable forms, drop dead `defn`/`defn-`.
+   Bail to keep-all on `resolve`/`ns-resolve`/`requiring-resolve`/`find-var`/
+   `intern`/`eval`/`load-string` (anything that defeats static reachability);
+   keep and scan `defmethod`/`defrecord`/`extend` bodies so dispatch targets
+   stay live.
+3. **Emit to a file.** Run `analyze → emit` for each surviving form under the
+   mode's knobs, concatenating the Scheme strings into one program source (the
+   core overlay prelude first, exactly as the seed image is built today).
+4. **Compile.** Feed that source to Chez `compile-program` (release) or
+   `compile-whole-program` (optimized, which also lets Chez cross-module
+   inline), producing a compiled object, then link a boot file / wrapper into
+   the final executable.
+
+Steps 3–4 are the only genuinely new back-end code. Step 2 is a re-port of a
+deleted pass. Steps before them already run on every `joltc` invocation.
+
+## Turning the passes on
+
+`inline-enabled?` is the existing gate. Today `host-contract.ss` hardwires it to
+`#f`. Under this RFC the build sets it (and a parallel `whole-program?` flag)
+from the chosen mode before compiling, so:
+
+- release: `inline-enabled?` → true, whole-program off. Per-ns inference and
+  inlining light up; `fl*`/`fx*` stays off.
+- optimized: both on; the types pass runs its whole-program fixpoint and the
+  back end may emit unchecked numeric ops where a flonum/fixnum is proven.
+
+No new pass is required to reach release — it is the ported passes, ungated.
+
+## Staging
+
+1. **Spike (de-risk Chez AOT).** Emit a trivial whole program to disk and prove
+   `compile-program` + boot/static link yields a standalone binary that runs.
+   This is the only real unknown.
+2. **`jolt build` release.** Front-end + file-emitting back-end path + flip
+   `inline-enabled?` from the mode. Gate against the bench/corpus suites; binary
+   output must pass the corpus a `run` passes.
+3. **DCE.** Re-port the reachability pass; gate with a test like the old
+   `uberscript-dce` case.
+4. **Optimized.** Whole-program flag, `compile-whole-program`, `fl*`/`fx*`
+   emission. Gate on the bench suite (ray tracer, binary-trees) for size and
+   speed vs the spike baseline.
+
+Each stage is TDD against the existing gates (`make test`, `make corpus`, the
+`bench/` programs). Modes land behind the build command, so dev — the only mode
+today — is unaffected until a stage proves out.
+
+## Open questions
+
+- **Static vs. boot-file linking.** A fully static Chez image is the smallest,
+  most portable artifact but the most work to link; a boot file plus a stub
+  launcher is the easy first cut. Spike decides which step 1 targets.
+- **FFI in a built binary.** `jolt.ffi` loads native libraries at runtime; a
+  closed-world build still needs that to work. The build must bake the FFI
+  Clojure side and keep dynamic `dlopen` at run time.
+- **Macro and `eval` at runtime.** Release/optimized are closed-world, but an
+  app that calls `eval`/`load-string` needs the compiler present. Either ship
+  the compiler image in the binary (larger) or reject those builds (the DCE
+  bail-out already detects the calls).
+
+## Prior art in this repo
+
+The optimization design these modes turn on is RFC 0004 (type hints), RFC 0005
+(structural inference), RFC 0006 (success checking). The linking model — direct
+linking as a per-unit property, `^:redef`/`^:dynamic` as the only opt-out — and
+the cross-ns specialization penalty are recorded in beads memories
+(`jolt-linking-model`, `cross-ns-param-penalty`). Phase 4 (`jolt-cf1q.5`) is the
+tracking issue.
diff --git a/host/chez/build-smoke.sh b/host/chez/build-smoke.sh
new file mode 100755
index 0000000..8cd75de
--- /dev/null
+++ b/host/chez/build-smoke.sh
@@ -0,0 +1,32 @@
+#!/bin/sh
+# build smoke: `jolt build` compiles a multi-namespace app (macro + cross-ns +
+# clojure.string) into a standalone binary, which then runs with no jolt source
+# or Chez install on the path — args reach -main, output matches.
+root="$(CDPATH= cd -- "$(dirname -- "$0")/../.." && pwd)"
+cd "$root"
+
+app="$root/test/chez/build-app"
+out="$(mktemp -d)/app-bin"
+trap 'rm -rf "$(dirname "$out")"' EXIT
+
+echo "build smoke: compiling app.core -> $out"
+if ! JOLT_PWD="$app" bin/joltc build -m app.core -o "$out" >/dev/null 2>&1; then
+  echo "  FAIL: jolt build exited non-zero"
+  exit 1
+fi
+[ -x "$out" ] || { echo "  FAIL: no executable produced"; exit 1; }
+
+# Run from a neutral cwd with args; check the three output lines.
+got="$(cd / && "$out" alpha bb ccc 2>&1)"
+want='HELLO FROM A BUILT BINARY!
+HELLO FROM A BUILT BINARY!
+args: [alpha bb ccc]
+sum: 10'
+if [ "$got" = "$want" ]; then
+  echo "build smoke: passed"
+else
+  echo "  FAIL: binary output mismatch"
+  echo "--- want ---"; echo "$want"
+  echo "--- got ----"; echo "$got"
+  exit 1
+fi
diff --git a/host/chez/build.ss b/host/chez/build.ss
new file mode 100644
index 0000000..a3bacdb
--- /dev/null
+++ b/host/chez/build.ss
@@ -0,0 +1,253 @@
+;; build.ss — `jolt build`: AOT-compile an app into a standalone executable.
+;;
+;; Loaded on demand by cli.ss when the command is `build`. Defines the host
+;; primitive jolt.host/build-binary, which jolt.main's build command calls after
+;; resolving the project's deps + source roots.
+;;
+;; The pipeline (Phase 4 stage 2):
+;;   1. load the entry namespace — registers its macros/vars and follows requires,
+;;      recording the app namespaces in dependency order (loader's ns-loaded-hook).
+;;   2. re-emit each app namespace to Scheme (the emit-image cross-compile path),
+;;      now that its macros are registered.
+;;   3. textually inline the cli.ss runtime load sequence into one flat source,
+;;      append the app emission + a launcher that calls the entry's -main.
+;;   4. compile-file -> make-boot-file -> embed the boot as C bytes -> cc-link
+;;      against libkernel.a into a single self-contained binary.
+;;
+;; emit-image.ss supplies the cross-compiler (ei-* helpers); it's loaded here so a
+;; normal run never pays for it.
+
+(load "host/chez/emit-image.ss")
+
+;; --- shell helpers ----------------------------------------------------------
+;; Run a command, return its stdout as one trimmed string ("" on no output).
+(define (bld-sh-capture cmd)
+  (let* ((p (process cmd)) (in (car p)))
+    (let loop ((acc '()))
+      (let ((l (get-line in)))
+        (if (eof-object? l)
+            (begin (close-port in)
+                   (let ((s (apply string-append (reverse acc))))
+                     ;; trim a trailing newline-equivalent (we joined without them)
+                     s))
+            (loop (cons l acc)))))))
+
+(define (bld-system cmd)
+  (let ((rc (system cmd)))
+    (unless (zero? rc)
+      (error 'jolt-build (string-append "command failed (" (number->string rc) "): " cmd)))))
+
+(define (bld-contains? s sub)
+  (let ((ns (string-length s)) (nsub (string-length sub)))
+    (let loop ((i 0))
+      (cond ((> (+ i nsub) ns) #f)
+            ((string=? (substring s i (+ i nsub)) sub) #t)
+            (else (loop (+ i 1)))))))
+
+;; --- toolchain discovery ----------------------------------------------------
+(define bld-machine (symbol->string (machine-type)))
+(define bld-osx? (bld-contains? bld-machine "osx"))
+
+;; The Chez executable, for the isolated compile pass (see build-binary step 4).
+(define bld-chez
+  (let ((p (bld-sh-capture "command -v chez || command -v scheme || command -v petite")))
+    (if (> (string-length p) 0) p "chez")))
+
+;; Chez version off (scheme-version) "Chez Scheme Version X.Y.Z" — last token.
+(define bld-version
+  (let* ((s (scheme-version)) (n (string-length s)))
+    (let loop ((i n))
+      (if (or (= i 0) (char=? (string-ref s (- i 1)) #\space))
+          (substring s i n)
+          (loop (- i 1))))))
+
+;; The csv<ver>/<machine> dir holding scheme.h, libkernel.a, *.boot. Derived from
+;; the chez executable's location; JOLT_CHEZ_CSV overrides.
+(define bld-csv-dir
+  (let ((env (getenv "JOLT_CHEZ_CSV")))
+    (or (and env (> (string-length env) 0) env)
+        (let* ((bindir (bld-sh-capture "dirname \"$(command -v chez || command -v scheme || command -v petite)\""))
+               (cand (string-append bindir "/../lib/csv" bld-version "/" bld-machine)))
+          cand))))
+
+(define (bld-check-toolchain)
+  (for-each
+    (lambda (f)
+      (let ((p (string-append bld-csv-dir "/" f)))
+        (unless (file-exists? p)
+          (error 'jolt-build (string-append "Chez build file missing: " p
+                                             "\nSet JOLT_CHEZ_CSV to the csv<ver>/<machine> dir.")))))
+    '("scheme.h" "libkernel.a" "petite.boot" "scheme.boot")))
+
+;; Link flags. macOS Homebrew layout for the kernel's lz4/zlib/ncurses deps.
+(define (bld-link-libs)
+  (if bld-osx?
+      (let ((lz4 (bld-sh-capture "brew --prefix lz4 2>/dev/null")))
+        (string-append
+          (if (> (string-length lz4) 0) (string-append "-L" lz4 "/lib ") "")
+          "-llz4 -lz -lncurses -framework Foundation -liconv -lm"))
+      ;; Best-effort Linux/other; untested here.
+      "-llz4 -lz -lncurses -ldl -lpthread -lm"))
+
+;; --- runtime manifest (mirrors host/chez/cli.ss's load order) ---------------
+(define bld-runtime-manifest
+  (list
+    "(load \"host/chez/rt.ss\")"
+    "(set-chez-ns! \"clojure.core\")"
+    "(load \"host/chez/seed/prelude.ss\")"
+    "(load \"host/chez/post-prelude.ss\")"
+    "(set-chez-ns! \"user\")"
+    "(load \"host/chez/host-contract.ss\")"
+    "(load \"host/chez/seed/image.ss\")"
+    "(load \"host/chez/compile-eval.ss\")"
+    "(load \"host/chez/png.ss\")"
+    "(load \"host/chez/loader.ss\")"
+    "(load \"host/chez/ffi.ss\")"
+    "(set-source-roots! (list \"jolt-core\" \"stdlib\"))"))
+
+;; A single-line top-level `(load "PATH")` -> PATH, else #f.
+(define (bld-load-path line)
+  (let ((s (let trim ((i 0))
+             (if (and (< i (string-length line))
+                      (memv (string-ref line i) '(#\space #\tab)))
+                 (trim (+ i 1))
+                 (substring line i (string-length line))))))
+    (and (>= (string-length s) 7)
+         (string=? (substring s 0 6) "(load ")
+         (let* ((q1 (let scan ((i 6)) (if (char=? (string-ref s i) #\") i (scan (+ i 1)))))
+                (q2 (let scan ((i (+ q1 1))) (if (char=? (string-ref s i) #\") i (scan (+ i 1))))))
+           (substring s (+ q1 1) q2)))))
+
+(define (bld-file-lines path)
+  (call-with-input-file path
+    (lambda (p)
+      (let loop ((acc '()))
+        (let ((l (get-line p)))
+          (if (eof-object? l) (reverse acc) (loop (cons l acc))))))))
+
+;; Emit one line to OUT, recursively inlining a `(load ...)` of a repo file.
+(define (bld-inline-line line out depth)
+  (when (> depth 50) (error 'jolt-build "load nesting too deep"))
+  (let ((p (bld-load-path line)))
+    (if p
+        (for-each (lambda (l) (bld-inline-line l out (+ depth 1))) (bld-file-lines p))
+        (begin (put-string out line) (put-string out "\n")))))
+
+(define (bld-emit-runtime out)
+  (for-each (lambda (l) (bld-inline-line l out 0)) bld-runtime-manifest))
+
+;; --- app emission -----------------------------------------------------------
+;; Re-emit one app namespace to a list of Scheme strings. Like emit-image's
+;; ei-emit-ns but WITHOUT the silent (guard ...) wrapper — a form that fails to
+;; emit must fail the build, not vanish.
+(define (bld-emit-ns ns-name src)
+  (let loop ((forms (ei-read-all src)) (acc '()))
+    (if (null? forms)
+        (reverse acc)
+        (let ((f (car forms)))
+          (ce-scan-requires! f ns-name)
+          (cond
+            ((ei-ns-form? f) (loop (cdr forms) acc))
+            ((ce-macro-form? f)
+             (let-values (((nm fn-form) (ce-defmacro->fn f)))
+               (let ((scm (let ((ctx (make-analyze-ctx ns-name)))
+                            (jolt-ce-emit (jolt-ce-analyze ctx fn-form)))))
+                 (loop (cdr forms)
+                       (cons (string-append
+                               "(def-var! " (ei-str-lit ns-name) " " (ei-str-lit nm) "\n  "
+                               scm ")\n(mark-macro! "
+                               (ei-str-lit ns-name) " " (ei-str-lit nm) ")")
+                             acc)))))
+            (else
+             (let* ((ctx (make-analyze-ctx ns-name))
+                    (scm (jolt-ce-emit (jolt-ce-analyze ctx f))))
+               (loop (cdr forms) (cons scm acc)))))))))
+
+;; --- the build --------------------------------------------------------------
+;; entry-ns: the app's main namespace (a string). out-path: the binary to write.
+;; mode: "dev" | "release" | "optimized" (recorded; optimization passes wired in a
+;; later stage). Deps + source roots are already applied by the caller.
+(define (build-binary entry-ns out-path mode)
+  (bld-check-toolchain)
+  ;; 1. record app namespaces in dependency order as they finish loading.
+  (let ((app-order '()))
+    (set-ns-loaded-hook!
+      (lambda (name file) (set! app-order (cons (cons name file) app-order))))
+    (load-namespace entry-ns)
+    (set-ns-loaded-hook! (lambda (name file) #f))
+    (let ((ordered (reverse app-order)))   ; deps first, entry last
+      (when (null? ordered)
+        (error 'jolt-build (string-append "no source namespace loaded for " entry-ns
+                                          " — is it on the source roots?")))
+      ;; 2. emit each app namespace.
+      (let* ((app-strs (apply append
+                         (map (lambda (nf) (bld-emit-ns (car nf) (read-file-string (cdr nf))))
+                              ordered)))
+             (builddir (string-append out-path ".build"))
+             (flat-ss  (string-append builddir "/flat.ss"))
+             (flat-so  (string-append builddir "/flat.so"))
+             (boot     (string-append builddir "/jolt.boot"))
+             (boot-h   (string-append builddir "/boot_data.h"))
+             (main-c   (string-append builddir "/main.c")))
+        (bld-system (string-append "mkdir -p '" builddir "'"))
+        ;; 3. flat source = runtime + app + launcher.
+        (let ((out (open-output-file flat-ss 'replace)))
+          (bld-emit-runtime out)
+          (put-string out "\n;; === app ===\n")
+          (for-each (lambda (s) (put-string out s) (put-string out "\n")) app-strs)
+          ;; The launcher runs as Chez's scheme-start (so argv reaches -main —
+          ;; top-level boot forms run during heap build, before args are set), and
+          ;; suppresses the interactive greeting.
+          (put-string out "\n;; === launcher ===\n")
+          (put-string out (string-append
+                            "(suppress-greeting #t)\n"
+                            "(scheme-start\n"
+                            "  (lambda args\n"
+                            "    (let ((mainv (var-deref " (ei-str-lit entry-ns) " \"-main\")))\n"
+                            "      (apply jolt-invoke mainv args))\n"
+                            "    (exit 0)))\n"))
+          (close-port out))
+        ;; 4. compile -> boot -> embed -> link.
+        ;; compile-file/make-boot-file run in a FRESH Chez, not this process: the
+        ;; loaded runtime shadows `error` (regex.ss, for irregex), which would
+        ;; otherwise bake a broken `error` reference into the boot.
+        (display (string-append "jolt build: compiling " entry-ns " (" mode " mode)\n"))
+        (let ((cs (string-append builddir "/compile.ss")))
+          (let ((p (open-output-file cs 'replace)))
+            (put-string p
+              (string-append
+                "(import (chezscheme))\n"
+                "(compile-file " (ei-str-lit flat-ss) " " (ei-str-lit flat-so) ")\n"
+                "(make-boot-file " (ei-str-lit boot) " '()\n  "
+                (ei-str-lit (string-append bld-csv-dir "/petite.boot")) "\n  "
+                (ei-str-lit (string-append bld-csv-dir "/scheme.boot")) "\n  "
+                (ei-str-lit flat-so) ")\n"))
+            (close-port p))
+          (bld-system (string-append bld-chez " --script '" cs "'")))
+        (bld-system (string-append "xxd -i '" boot "' > '" boot-h "'"))
+        ;; The xxd symbol is derived from the path; normalize to jolt_boot.
+        (bld-system (string-append
+          "sed -i.bak -E 's/unsigned char [A-Za-z0-9_]+\\[\\]/unsigned char jolt_boot[]/; "
+          "s/unsigned int [A-Za-z0-9_]+_len/unsigned int jolt_boot_len/' '" boot-h "'"))
+        (let ((mc (open-output-file main-c 'replace)))
+          (put-string mc
+            (string-append
+              "#include \"scheme.h\"\n#include \"boot_data.h\"\n"
+              "int main(int argc, char *argv[]) {\n"
+              "  Sscheme_init(0);\n"
+              "  Sregister_boot_file_bytes(\"jolt\", jolt_boot, jolt_boot_len);\n"
+              "  Sbuild_heap(0, 0);\n"
+              "  int status = Sscheme_start(argc, (const char **)argv);\n"
+              "  Sscheme_deinit();\n  return status;\n}\n"))
+          (close-port mc))
+        (bld-system (string-append
+          "cc -O2 -I'" bld-csv-dir "' '" main-c "' '" bld-csv-dir "/libkernel.a' "
+          "-o '" out-path "' " (bld-link-libs)))
+        (display (string-append "jolt build: wrote " out-path "\n"))))))
+
+(def-var! "jolt.host" "build-binary"
+  (lambda (entry out mode)
+    (build-binary (jolt-str-render-one entry)
+                  (jolt-str-render-one out)
+                  (jolt-str-render-one mode))
+    jolt-nil))
diff --git a/host/chez/cli.ss b/host/chez/cli.ss
index 349acfd..9f597cb 100644
--- a/host/chez/cli.ss
+++ b/host/chez/cli.ss
@@ -66,6 +66,11 @@
          (display result) (newline))))
     ;; otherwise dispatch the argv through jolt.main/-main
     (else
+     ;; `build` AOT-compiles an app to a standalone binary — load the build
+     ;; driver (the cross-compiler emitter) on demand so a normal run never pays
+     ;; for it. It defines jolt.host/build-binary, which jolt.main's build cmd calls.
+     (when (and (pair? cli-args) (string=? (car cli-args) "build"))
+       (load "host/chez/build.ss"))
      (load-namespace "jolt.main")
      (let ((mainv (var-deref "jolt.main" "-main")))
        (apply jolt-invoke mainv cli-args)))))
diff --git a/host/chez/loader.ss b/host/chez/loader.ss
index 973e0cf..a0087b9 100644
--- a/host/chez/loader.ss
+++ b/host/chez/loader.ss
@@ -53,6 +53,23 @@
 (vector-for-each (lambda (c) (hashtable-set! loaded-ns (var-cell-ns c) #t))
                  (hashtable-values var-table))
 
+;; Does `name` already have vars in the var-table? A namespace baked into the
+;; image after the snapshot above — an AOT'd app namespace in a `jolt build`
+;; binary — exists in memory with no source file; a later `require` of it must
+;; no-op rather than hunt the (absent) source.
+(define (ns-has-vars? name)
+  (let ((found #f))
+    (vector-for-each
+      (lambda (c) (when (and (not found) (string=? (var-cell-ns c) name)) (set! found #t)))
+      (hashtable-values var-table))
+    found))
+
+;; Called after a file-backed namespace finishes loading, with (name file). The
+;; build driver sets this to record app namespaces in dependency order for AOT
+;; emission; a no-op for normal runs.
+(define ns-loaded-hook (lambda (name file) #f))
+(define (set-ns-loaded-hook! f) (set! ns-loaded-hook f))
+
 ;; Read every form from a file and compile+eval it in turn. The first form is
 ;; normally (ns …), which expands to (in-ns …) and switches the current ns, so
 ;; later forms compile in that namespace — (chez-current-ns) is re-read each step.
@@ -80,17 +97,22 @@
 ;; restored afterward, since loading the file switched it.
 (define (load-namespace name)
   (unless (hashtable-ref loaded-ns name #f)
-    (hashtable-set! loaded-ns name #t)
     (let ((file (find-ns-file name)))
-      (if (not file)
-          (begin
-            (hashtable-delete! loaded-ns name)
-            (error #f (string-append "Could not locate " (ns-name->rel name)
-                                     ".clj (or .cljc) on the source roots") name))
-          (let ((saved (chez-current-ns)))
-            (load-jolt-file file)
-            ;; restore the current ns (thread-local); *ns* reads derive from it.
-            (set-chez-ns! saved))))))
+      (cond
+        (file
+         (hashtable-set! loaded-ns name #t)   ; mark before load so a cycle terminates
+         (let ((saved (chez-current-ns)))
+           (load-jolt-file file)
+           ;; restore the current ns (thread-local); *ns* reads derive from it.
+           (set-chez-ns! saved))
+         (ns-loaded-hook name file))
+        ;; No source file but the namespace exists in memory (AOT'd into a built
+        ;; binary): it's already defined — mark loaded and move on.
+        ((ns-has-vars? name)
+         (hashtable-set! loaded-ns name #t))
+        (else
+         (error #f (string-append "Could not locate " (ns-name->rel name)
+                                  ".clj (or .cljc) on the source roots") name))))))
 
 ;; load-file: load an explicit path (a `run FILE`), in the current ns.
 (define (jolt-load-file path)
diff --git a/jolt-core/jolt/main.clj b/jolt-core/jolt/main.clj
index 94c2626..40e674a 100644
--- a/jolt-core/jolt/main.clj
+++ b/jolt-core/jolt/main.clj
@@ -112,6 +112,28 @@
       (map? task) (do (apply-project! resolved) (apply-main-opts (:main-opts task) more))
       :else (throw (ex-info (str "bad task " name) {})))))
 
+;; build [-m NS | FILE] [-o OUT] [--opt | --dev] — AOT-compile the app into a
+;; standalone executable. Resolves deps + roots like `run`, then hands the entry
+;; namespace to the host build driver (jolt.host/build-binary, defined by
+;; build.ss). Default mode is release; --opt selects optimized, --dev unoptimized.
+(defn- cmd-build [more]
+  (apply-project! (deps/resolve-project (project-dir)))
+  (let [opts (loop [a more, entry nil, out nil]
+               (cond
+                 (empty? a)          {:entry entry :out out}
+                 (= "-m" (first a))  (recur (drop 2 a) (second a) out)
+                 (= "-o" (first a))  (recur (drop 2 a) entry (second a))
+                 (str/starts-with? (first a) "-") (recur (rest a) entry out)
+                 :else               (recur (rest a) (or entry (first a)) out)))
+        entry (:entry opts)
+        mode  (cond (some #{"--opt"} more) "optimized"
+                    (some #{"--dev"} more) "dev"
+                    :else                  "release")]
+    (when (nil? entry)
+      (throw (ex-info "build needs an entry: -m NS" {})))
+    (let [out (or (:out opts) (first (str/split entry #"\.")))]
+      (jolt.host/build-binary entry out mode))))
+
 (defn- nrepl [more]
   ;; resolve the project (deps on the roots, native libs loaded), then start the
   ;; nREPL server so an editor can connect and (require '[some.lib]) live. A
@@ -128,6 +150,7 @@
   (println "usage: jolt <command> [args]")
   (println "  run -m NS [args]   resolve deps.edn, load NS, call its -main")
   (println "  run FILE           load a Clojure file")
+  (println "  build -m NS [-o OUT] [--opt|--dev]  compile a standalone binary")
   (println "  -M:alias [args]    run the alias's :main-opts")
   (println "  -A:alias [args]    add the alias's paths/deps")
   (println "  repl               start a line REPL")
@@ -146,4 +169,5 @@
       (str/starts-with? cmd "-M") (cmd-M cmd more)
       (str/starts-with? cmd "-A") (cmd-A cmd more)
       (= cmd "-m")                (cmd-run (cons "-m" more))
+      (= cmd "build")             (cmd-build more)
       :else                       (run-task cmd more))))
diff --git a/test/chez/build-app/deps.edn b/test/chez/build-app/deps.edn
new file mode 100644
index 0000000..ccd9a31
--- /dev/null
+++ b/test/chez/build-app/deps.edn
@@ -0,0 +1 @@
+{:paths ["src"]}
diff --git a/test/chez/build-app/src/app/core.clj b/test/chez/build-app/src/app/core.clj
new file mode 100644
index 0000000..4fd95a0
--- /dev/null
+++ b/test/chez/build-app/src/app/core.clj
@@ -0,0 +1,7 @@
+(ns app.core
+  (:require [app.util :as util]))
+
+(defn -main [& args]
+  (util/twice (println (util/shout "hello from a built binary")))
+  (println "args:" (vec args))
+  (println "sum:" (reduce + (map count args))))
diff --git a/test/chez/build-app/src/app/util.clj b/test/chez/build-app/src/app/util.clj
new file mode 100644
index 0000000..c4f7429
--- /dev/null
+++ b/test/chez/build-app/src/app/util.clj
@@ -0,0 +1,8 @@
+(ns app.util
+  (:require [clojure.string :as str]))
+
+(defn shout [s]
+  (str/upper-case (str s "!")))
+
+(defmacro twice [x]
+  `(do ~x ~x))