diff --git a/Makefile b/Makefile
index f94c8ddc..c586ad12 100644
--- a/Makefile
+++ b/Makefile
@@ -537,6 +537,7 @@ TESTS	= $(BIN)/test_smoke $(BIN)/test_lex $(BIN)/test_parse $(BIN)/test_check \
 	  $(BIN)/test_w6c_ww $(BIN)/test_ww_ww $(BIN)/test_self_rebuild \
 	  $(BIN)/test_dyn_ww $(BIN)/test_selfcheck $(BIN)/test_at_test_ww \
 	  $(BIN)/test_attest_record $(BIN)/test_attest_drop \
+	  $(BIN)/test_declns_sep \
 	  $(BIN)/test_fmt_run $(BIN)/test_log_run $(BIN)/test_fnmatch_run \
 	  $(BIN)/test_shlex_run $(BIN)/test_getenv_run $(BIN)/test_dirs_run \
 	  $(BIN)/test_dirs_toolong_run \
@@ -2965,6 +2966,15 @@ $(BIN)/test_attest_drop: test/wcc/911_attest_drop.c $(BIN)/w6c $(BIN)/w6c_ww \
 		$(LIB)/libwwrt.a | $(BIN)
 	$(CC) $(CFLAGS) -o $@ $<
 
+# C2c — #23/#30 decl-namespace (dup family + builtin carve-out via direct
+# w6c/w6c_ww) + module-fn coexistence (dir-package `ww build --sep` + run,
+# both driver stages + cross-order byte-id) → all six tools + drivers +
+# libwwrt for the builtin_redecl link.
+$(BIN)/test_declns_sep: test/wcc/989_declns_sep.c $(BIN)/ww $(BIN)/ww_ww \
+		$(BIN)/w6c $(BIN)/w6c_ww $(BIN)/w6a $(BIN)/w6a_ww \
+		$(BIN)/w6l $(BIN)/w6l_ww $(LIB)/libwwrt.a | $(BIN)
+	$(CC) $(CFLAGS) -o $@ $<
+
 $(BIN)/test_fmt_run: test/wcc/970_fmt_run.c $(BIN)/ww $(BIN)/w6c \
 		$(BIN)/w6a $(BIN)/w6l $(LIB)/libwwrt.a | $(BIN)
 	$(CC) $(CFLAGS) -o $@ $<
diff --git a/test/wcc/989_declns_sep.c b/test/wcc/989_declns_sep.c
new file mode 100644
index 00000000..00c12245
--- /dev/null
+++ b/test/wcc/989_declns_sep.c
@@ -0,0 +1,392 @@
+/*
+ * 989_declns_sep — #23/#30 declaration-namespace + module-fn coexistence
+ * under the directory-package model (task #83, M4 E2-C2c).
+ *
+ * Re-hosts every decl-namespace assertion that today lives ONLY in
+ * 910/997 onto a gate that survives the M4 flip (910/997 are deleted at
+ * the flip — they feed combined.ww / amalgamation inputs). Three legs:
+ *
+ *   dup family    — a duplicate top-level fn/type/def/let in one (flat)
+ *                   module must build-FAIL on BOTH stages. The fixtures
+ *                   are flat single-package (the surviving shape) and feed
+ *                   `w6c` / `w6c_ww` DIRECTLY — no driver resolution; the
+ *                   dup is an install-pass property, not a build-model one.
+ *                   712 covered the cstage let arm; 997 covered the wwstage
+ *                   arm — this gate asserts BOTH stages reject every kind,
+ *                   closing the ww arm that dies with 997.
+ *   builtin_redecl— the carve-out: a user redecl of a pre-seeded builtin
+ *                   name (`nomem`) is NOT a duplicate. cstage keeps no
+ *                   builtins in scope (lookup_builtin wins first), wwstage
+ *                   seeds them into c.top so installtop must DROP the redecl
+ *                   rather than error. Both stages accept + run to 7.
+ *   modfn coexist — a top-level value-namespace `fn aa` and an imported
+ *                   MODULE `aa` coexist: bare `aa()` binds the fn (a module
+ *                   is not callable), `aa.helper()` binds through the module.
+ *                   RESHAPED from the dying multi-`package`-single-file
+ *                   910/997 fixtures to dir-packages (696 precedent), built
+ *                   via `ww build --sep` + run. The _vbu twin flips the decl
+ *                   order (`fn aa` BEFORE `import aa`): cstage installs every
+ *                   SK_USE in an order-independent first pass, wwstage in
+ *                   source order, so vbu exercises a DISTINCT promote path —
+ *                   its asm must be byte-identical to the use-before-value
+ *                   order, the teeth against silent order-dependence.
+ *
+ * dup_xpkg (same leaf in distinct packages = legal) RIDES on 696/697's
+ * dir-package coverage — no port (spec C2c).
+ *
+ * Light wwstage-driver test (CLAUDE.md rule 14): every modfn intermediate
+ * is `-o`-redirected to /tmp, so it is phase-1 parallel-safe; the dup +
+ * builtin legs feed w6c directly with `-o /tmp`. Models 989_sepbuild_run +
+ * 911_attest_drop conventions; 989 prefix per the sep-gate precedent (the
+ * 7xx cgen/check range is exhausted).
+ */
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+#include <sys/wait.h>
+#include <sys/stat.h>
+
+static int
+runwait(const char *cmd)
+{
+	int rc = system(cmd);
+	if (rc == -1) return -1;
+	if (WIFEXITED(rc)) return WEXITSTATUS(rc);
+	return 1;
+}
+
+static const char *
+absbin(void)
+{
+	const char *b = getenv("BIN");
+	if (!b) b = "out/bin";
+	if (b[0] == '/') return b;
+	static char buf[2048];
+	char cwd[1024];
+	if (getcwd(cwd, sizeof cwd) == NULL) return NULL;
+	snprintf(buf, sizeof buf, "%s/%s", cwd, b);
+	return buf;
+}
+
+static int
+slurp(const char *path, char **outbuf, size_t *outlen)
+{
+	FILE *f = fopen(path, "rb");
+	if (!f) return -1;
+	fseek(f, 0, SEEK_END);
+	long n = ftell(f);
+	fseek(f, 0, SEEK_SET);
+	if (n < 0) { fclose(f); return -1; }
+	char *b = malloc((size_t)n + 1);
+	if (!b) { fclose(f); return -1; }
+	if (fread(b, 1, (size_t)n, f) != (size_t)n) { free(b); fclose(f); return -1; }
+	b[n] = '\0';
+	fclose(f);
+	*outbuf = b;
+	*outlen = (size_t)n;
+	return 0;
+}
+
+static int
+files_eq(const char *a, const char *b)
+{
+	char *ba = NULL, *bb = NULL;
+	size_t na = 0, nb = 0;
+	if (slurp(a, &ba, &na) < 0 || slurp(b, &bb, &nb) < 0) {
+		free(ba); free(bb);
+		return -1;
+	}
+	int eq = (na == nb && memcmp(ba, bb, na) == 0);
+	free(ba); free(bb);
+	return eq ? 0 : 1;
+}
+
+/* 0 if `needle` occurs in the file at `path`, else 1 (or -1 on read err). */
+static int
+file_contains(const char *path, const char *needle)
+{
+	char *b = NULL;
+	size_t n = 0;
+	if (slurp(path, &b, &n) < 0) return -1;
+	int found = (strstr(b, needle) != NULL);
+	free(b);
+	return found ? 0 : 1;
+}
+
+/*
+ * dup family — direct-w6c/w6c_ww. Each fixture is a flat single-package
+ * with one duplicate top-level decl; both stages must build-FAIL, and the
+ * diagnostic must name the duplicate (non-vacuity: a fixture that failed
+ * for an unrelated reason would pass an exit-only check). cstage prefixes
+ * line:col, wwstage does not, so the asserted substring is the shared tail.
+ */
+static const struct {
+	const char *fixture;
+	const char *diag;	/* shared "duplicate <kind> <name>" substring */
+} dup_rows[] = {
+	{ "test/wcc/data/dup_fn.ww",   "duplicate fn foo" },
+	{ "test/wcc/data/dup_type.ww", "duplicate type t" },
+	{ "test/wcc/data/dup_def.ww",  "duplicate def D" },
+	{ "test/wcc/data/dup_let.ww",  "duplicate let g" },
+};
+
+static int
+dup_family(const char *bin)
+{
+	int pid = getpid();
+	char err[256], cmd[4096];
+	snprintf(err, sizeof err, "/tmp/declns_dup_%d.err", pid);
+
+	int rc = 0;
+	const char *comps[] = { "w6c", "w6c_ww" };
+	for (size_t r = 0; r < sizeof dup_rows / sizeof dup_rows[0]; r++) {
+		for (size_t c = 0; c < sizeof comps / sizeof comps[0]; c++) {
+			snprintf(cmd, sizeof cmd, "%s/%s %s -o /dev/null 2>%s",
+			    bin, comps[c], dup_rows[r].fixture, err);
+			if (runwait(cmd) == 0) {
+				fprintf(stderr, "declns FAIL: %s accepted %s (expected "
+				    "build-fail)\n", comps[c], dup_rows[r].fixture);
+				rc = 1;
+			} else if (file_contains(err, dup_rows[r].diag) != 0) {
+				fprintf(stderr, "declns FAIL: %s rejected %s but not on "
+				    "`%s` (wrong reason)\n", comps[c], dup_rows[r].fixture,
+				    dup_rows[r].diag);
+				rc = 1;
+			}
+		}
+	}
+	unlink(err);
+	return rc;
+}
+
+/*
+ * builtin_redecl — the carve-out. Import-free + flat, so it feeds the
+ * direct w6c→w6a→w6l pipeline (mirrors 911's linkfail staging). The
+ * builtin `nomem` (= !void) wins, so g()'s i32 arm returns 7; both stages
+ * must accept AND run to that exact code.
+ */
+static const struct {
+	const char *comp;
+	const char *asmt;
+	const char *linkt;
+} stages[] = {
+	{ "w6c",    "w6a",    "w6l"    },
+	{ "w6c_ww", "w6a_ww", "w6l_ww" },
+};
+
+static int
+builtin_redecl(const char *bin)
+{
+	int pid = getpid();
+	char rt[1024], asmf[256], obj[256], exe[256], cmd[4096];
+	snprintf(rt, sizeof rt, "%s/../lib/libwwrt.a", bin);
+
+	int rc = 0;
+	for (size_t i = 0; i < sizeof stages / sizeof stages[0]; i++) {
+		snprintf(asmf, sizeof asmf, "/tmp/declns_br_%s_%d.s", stages[i].comp, pid);
+		snprintf(obj,  sizeof obj,  "/tmp/declns_br_%s_%d.o", stages[i].comp, pid);
+		snprintf(exe,  sizeof exe,  "/tmp/declns_br_%s_%d.exe", stages[i].comp, pid);
+
+		int ok = 1;
+		snprintf(cmd, sizeof cmd,
+		    "%s/%s test/wcc/data/builtin_redecl_ok.ww -o %s 2>/dev/null",
+		    bin, stages[i].comp, asmf);
+		if (ok && runwait(cmd) != 0) {
+			fprintf(stderr, "declns FAIL: %s rejected builtin_redecl "
+			    "(carve-out must accept)\n", stages[i].comp);
+			ok = 0; rc = 1;
+		}
+		snprintf(cmd, sizeof cmd, "%s/%s -o %s %s 2>/dev/null",
+		    bin, stages[i].asmt, obj, asmf);
+		if (ok && runwait(cmd) != 0) {
+			fprintf(stderr, "declns FAIL: %s asm of builtin_redecl\n",
+			    stages[i].asmt);
+			ok = 0; rc = 1;
+		}
+		snprintf(cmd, sizeof cmd, "%s/%s -o %s %s %s 2>/dev/null",
+		    bin, stages[i].linkt, exe, obj, rt);
+		if (ok && runwait(cmd) != 0) {
+			fprintf(stderr, "declns FAIL: %s link of builtin_redecl\n",
+			    stages[i].linkt);
+			ok = 0; rc = 1;
+		}
+		if (ok) {
+			int got = runwait(exe);
+			if (got != 7) {
+				fprintf(stderr, "declns FAIL: builtin_redecl (%s) "
+				    "exit=%d want=7\n", stages[i].comp, got);
+				rc = 1;
+			}
+		}
+		unlink(asmf); unlink(obj); unlink(exe);
+	}
+	return rc;
+}
+
+/*
+ * modfn coexist — the two dir-package layouts. Build each via `ww build
+ * --sep` + run, both driver stages, expect exit 6 (aa()=1 + aa.helper()=5).
+ * `ww build` (NOT `ww run`) per spec: run is not sep-wired until the driver
+ * flip. Returns 0 on success; leaves <prog>.sepwork in `td` for the byte-id
+ * compares below.
+ */
+struct modfn { const char *lay; const char *fixture; };
+static const struct modfn modfn_lays[] = {
+	{ "coexist",     "test/wcc/data/modfn_coexist/main.ww" },
+	{ "coexist_vbu", "test/wcc/data/modfn_coexist_vbu/main.ww" },
+};
+
+/* per-package output the sep driver materializes; the root carries no .wwi
+ * (post-#69 it is compiled without -I), so its suffix set omits .wwi. */
+static const struct {
+	const char *pkg;
+	const char *suf;
+} parts[] = {
+	{ "aa",     ".s" },
+	{ "aa",     ".wwi" },
+	{ "aa",     ".unit.ww" },
+	{ "__root", ".s" },
+	{ "__root", ".unit.ww" },
+};
+
+static int
+modfn_build(const char *bin, const char *td)
+{
+	char cmd[4096], prog[1024];
+	int rc = 0;
+	for (size_t l = 0; l < sizeof modfn_lays / sizeof modfn_lays[0]; l++) {
+		for (size_t s = 0; s < sizeof stages / sizeof stages[0]; s++) {
+			const char *drv = (s == 0) ? "ww" : "ww_ww";
+			snprintf(prog, sizeof prog, "%s/%s.%s", td, modfn_lays[l].lay,
+			    (s == 0) ? "cs" : "ww");
+			snprintf(cmd, sizeof cmd, "%s/%s build --sep -o %s %s 2>/dev/null",
+			    bin, drv, prog, modfn_lays[l].fixture);
+			if (runwait(cmd) != 0) {
+				fprintf(stderr, "declns FAIL: %s build --sep %s\n", drv,
+				    modfn_lays[l].lay);
+				rc = 1;
+				continue;
+			}
+			int got = runwait(prog);
+			if (got != 6) {
+				fprintf(stderr, "declns FAIL: modfn %s (%s) exit=%d want=6 "
+				    "(coexistence mis-resolved)\n", modfn_lays[l].lay, drv, got);
+				rc = 1;
+			}
+		}
+	}
+	return rc;
+}
+
+/* cs==ww (rule 10): for one layout, every per-package .s/.wwi/.unit.ww the
+ * cstage and wwstage sep drivers emitted must be byte-identical. */
+static int
+modfn_cs_eq_ww(const char *td, const char *lay)
+{
+	int rc = 0;
+	for (size_t p = 0; p < sizeof parts / sizeof parts[0]; p++) {
+		char a[1024], b[1024];
+		snprintf(a, sizeof a, "%s/%s.cs.sepwork/%s%s", td, lay, parts[p].pkg, parts[p].suf);
+		snprintf(b, sizeof b, "%s/%s.ww.sepwork/%s%s", td, lay, parts[p].pkg, parts[p].suf);
+		if (files_eq(a, b) != 0) {
+			fprintf(stderr, "declns FAIL: %s cs!=ww for %s%s (rule 10)\n",
+			    lay, parts[p].pkg, parts[p].suf);
+			rc = 1;
+		}
+	}
+	return rc;
+}
+
+/* cross-order byte-id: the value-before-use layout must emit asm/interface
+ * byte-identical to the use-before-value layout (same stage). Silent
+ * order-dependence in the SK_USE/value-sym promote is exactly what regresses;
+ * a divergence here is the teeth. */
+static int
+modfn_order_id(const char *td)
+{
+	int rc = 0;
+	const char *tags[] = { "cs", "ww" };
+	for (size_t t = 0; t < sizeof tags / sizeof tags[0]; t++) {
+		for (size_t p = 0; p < sizeof parts / sizeof parts[0]; p++) {
+			/* `.unit.ww` is the driver's verbatim source-assembly
+			 * intermediate — it embeds the two layouts' differently
+			 * ORDERED source text, so it differs by construction. The
+			 * order-independence claim is about CODEGEN, so it is tested
+			 * on the compiled `.s`/`.wwi` only. */
+			if (strcmp(parts[p].suf, ".unit.ww") == 0) continue;
+			char a[1024], b[1024];
+			snprintf(a, sizeof a, "%s/coexist.%s.sepwork/%s%s",
+			    td, tags[t], parts[p].pkg, parts[p].suf);
+			snprintf(b, sizeof b, "%s/coexist_vbu.%s.sepwork/%s%s",
+			    td, tags[t], parts[p].pkg, parts[p].suf);
+			if (files_eq(a, b) != 0) {
+				fprintf(stderr, "declns FAIL: vbu!=non-vbu for %s%s (%s) — "
+				    "silent decl-order dependence\n", parts[p].pkg,
+				    parts[p].suf, tags[t]);
+				rc = 1;
+			}
+		}
+	}
+	return rc;
+}
+
+/* non-vacuity: __root.s must carry BOTH calls distinctly — through the
+ * module (`aa.helper`) and to the local value fn (`main.aa`) — proving the
+ * two namespaces resolved to different symbols rather than collapsing. */
+static int
+modfn_coexist_present(const char *td)
+{
+	int rc = 0;
+	const char *tags[] = { "cs", "ww" };
+	for (size_t t = 0; t < sizeof tags / sizeof tags[0]; t++) {
+		char rs[1024];
+		snprintf(rs, sizeof rs, "%s/coexist.%s.sepwork/__root.s", td, tags[t]);
+		if (file_contains(rs, "CALL\taa.helper(SB)") != 0) {
+			fprintf(stderr, "declns FAIL: __root.s (%s) lacks module-qualified "
+			    "`CALL aa.helper(SB)`\n", tags[t]);
+			rc = 1;
+		}
+		if (file_contains(rs, "CALL\tmain.aa(SB)") != 0) {
+			fprintf(stderr, "declns FAIL: __root.s (%s) lacks local-fn "
+			    "`CALL main.aa(SB)`\n", tags[t]);
+			rc = 1;
+		}
+	}
+	return rc;
+}
+
+int
+main(void)
+{
+	const char *bin = absbin();
+	if (!bin) { fprintf(stderr, "declns FAIL: getcwd\n"); return 1; }
+
+	int fail = 0;
+	fail += dup_family(bin);
+	fail += builtin_redecl(bin);
+
+	char td[64], cmd[256];
+	snprintf(td, sizeof td, "/tmp/wwdeclns_%d", getpid());
+	snprintf(cmd, sizeof cmd, "rm -rf %s", td);
+	runwait(cmd);
+	mkdir(td, 0755);
+
+	fail += modfn_build(bin, td);
+	fail += modfn_cs_eq_ww(td, "coexist");
+	fail += modfn_cs_eq_ww(td, "coexist_vbu");
+	fail += modfn_order_id(td);
+	fail += modfn_coexist_present(td);
+
+	snprintf(cmd, sizeof cmd, "rm -rf %s", td);
+	runwait(cmd);
+
+	if (fail) {
+		fprintf(stderr, "declns: %d check(s) failed\n", fail);
+		return 1;
+	}
+	printf("declns: dup fn/type/def/let build-fail (both stages) + "
+	    "builtin_redecl accept→7 + modfn dir-pkg coexist→6 (cs==ww, "
+	    "vbu byte-id to use-before-value), both stages (#23/#30)\n");
+	return 0;
+}
diff --git a/test/wcc/data/modfn_coexist/aa/aa.ww b/test/wcc/data/modfn_coexist/aa/aa.ww
new file mode 100644
index 00000000..fedf3da5
--- /dev/null
+++ b/test/wcc/data/modfn_coexist/aa/aa.ww
@@ -0,0 +1,5 @@
+// #30 dir-package — the imported module `aa`. Paired with ../main.ww,
+// whose primary package also declares a value-namespace `fn aa`. Driver:
+// the modfn_coexist leg of the decl-namespace gate (NNN_declns_sep.c).
+package aa;
+export fn helper() i32 = { return 5; };
diff --git a/test/wcc/data/modfn_coexist/main.ww b/test/wcc/data/modfn_coexist/main.ww
new file mode 100644
index 00000000..22e939f5
--- /dev/null
+++ b/test/wcc/data/modfn_coexist/main.ww
@@ -0,0 +1,11 @@
+// #30 dir-package coexistence — the value-namespace `fn aa` and the
+// imported MODULE `aa` (SK_USE) coexist. `aa()` binds the local fn (a
+// module is not callable); `aa.helper()` binds through the module (the
+// fn has no field `helper`). Both must resolve, so any mis-resolution
+// fails to COMPILE; running to 1+5=6 proves both bind. The dir-package
+// reshape of the dying single-file modfn_coexist_ok.ww (M4 amalgamation
+// shape retired at the flip).
+package main;
+import aa;
+fn aa() i32 = { return 1; };
+export fn main() i32 = { return aa() + aa.helper(); };
diff --git a/test/wcc/data/modfn_coexist_vbu/aa/aa.ww b/test/wcc/data/modfn_coexist_vbu/aa/aa.ww
new file mode 100644
index 00000000..61486cbe
--- /dev/null
+++ b/test/wcc/data/modfn_coexist_vbu/aa/aa.ww
@@ -0,0 +1,6 @@
+// #30 dir-package — the imported module `aa` for the VALUE-BEFORE-USE
+// twin. Identical to ../../modfn_coexist/aa/aa.ww; kept as its own dir so
+// the two layouts are independently buildable. Driver: the
+// modfn_coexist_vbu leg of the decl-namespace gate (NNN_declns_sep.c).
+package aa;
+export fn helper() i32 = { return 5; };
diff --git a/test/wcc/data/modfn_coexist_vbu/main.ww b/test/wcc/data/modfn_coexist_vbu/main.ww
new file mode 100644
index 00000000..f62990d6
--- /dev/null
+++ b/test/wcc/data/modfn_coexist_vbu/main.ww
@@ -0,0 +1,12 @@
+// #30 VALUE-BEFORE-USE — the twin of ../modfn_coexist/main.ww with the
+// decl order flipped: `fn aa` is declared BEFORE `import aa`. cstage is
+// order-independent (installs every SK_USE in a first pass); wwstage
+// installs in source order, so this direction exercises a DISTINCT path
+// (installdecl's N_USE arm must set use_alias on the pre-installed value
+// sym). The gate asserts this builds + runs to 6 AND emits asm
+// byte-identical to the use-before-value order — silent order-dependence
+// is exactly what regresses.
+package main;
+fn aa() i32 = { return 1; };
+import aa;
+export fn main() i32 = { return aa() + aa.helper(); };