diff --git a/Makefile b/Makefile
index 718e557c..8b289f96 100644
--- a/Makefile
+++ b/Makefile
@@ -311,6 +311,7 @@ TESTS	= $(BIN)/test_smoke $(BIN)/test_lex $(BIN)/test_parse $(BIN)/test_check \
 	  $(BIN)/test_cast_enum_movl \
 	  $(BIN)/test_check_enum_fold \
 	  $(BIN)/test_def_widen_const \
+	  $(BIN)/test_inferred_struct_arg_push \
 	  $(BIN)/test_use_promote_alias \
 	  $(BIN)/test_field_signed $(BIN)/test_frame_argcount \
 	  $(BIN)/test_selfhost $(BIN)/test_w6a_ww $(BIN)/test_w6l_ww \
@@ -584,6 +585,12 @@ $(BIN)/test_def_widen_const: test/wcc/760_def_widen_const.c \
 		$(LIB)/libwwrt.a | $(BIN)
 	$(CC) $(CFLAGS) -o $@ $<
 
+$(BIN)/test_inferred_struct_arg_push: test/wcc/761_inferred_struct_arg_push.c \
+		$(BIN)/ww $(BIN)/w6c $(BIN)/w6a $(BIN)/w6l \
+		$(BIN)/ww_ww $(BIN)/w6c_ww $(BIN)/w6a_ww $(BIN)/w6l_ww \
+		$(LIB)/libwwrt.a | $(BIN)
+	$(CC) $(CFLAGS) -o $@ $<
+
 $(BIN)/test_arrlit_str_full: test/wcc/711_arrlit_str_full.c \
 		$(BIN)/ww $(BIN)/w6c $(BIN)/w6a $(BIN)/w6l \
 		$(BIN)/ww_ww $(BIN)/w6c_ww $(BIN)/w6a_ww $(BIN)/w6l_ww \
diff --git a/test/wcc/761_inferred_struct_arg_push.c b/test/wcc/761_inferred_struct_arg_push.c
new file mode 100644
index 00000000..d294d22b
--- /dev/null
+++ b/test/wcc/761_inferred_struct_arg_push.c
@@ -0,0 +1,355 @@
+/*
+ * 761_inferred_struct_arg_push — regression lock for project #16, the
+ * inferred-let-struct-local → call-arg push width. Closed incidentally
+ * by ea1579a (SK_USE-gated N_DOT call result), 7198937 (asserttyped bail
+ * rearm), 39f9267 + 66a91c8 (#169b structabisize convergence cascade).
+ *
+ * Each closing commit removed one path that could have left the local's
+ * type-AST unstamped — together they guarantee cglet's `tn = n.lhs ??
+ * inferletcalltype(...)` and the localadd'd `lc.tnode` always carry a
+ * resolvable N_TNAME for an inferred struct-typed let. pushargsrev's
+ * N_IDENT struct arm (selfhost/cmd/wcc/cgenutil.ww:459) then reaches
+ * structparamsize > 0 and emits the maxalign-rounded 1-or-2 word push,
+ * byte-id with cstage's `args[i]->type` → struct_arg_size path
+ * (cmd/w6c/cgen.c:427, :5452).
+ *
+ * The 16-shape impl-16 probe sweep (worktree-impl-16) confirmed
+ * byte-identity across every reasonable trigger. This file consolidates
+ * the load-bearing rows so the symmetric behavior cannot regress without
+ * a green-to-red flip on these probes.
+ *
+ * WHAT THIS LOCKS
+ *   - cs==ww .s byte-identity for inferred-let + struct-arg-push
+ *     across struct shapes:
+ *       * {i64,i64}                 — canonical 16B, maxalign 8
+ *       * {u32,i64}                 — decf32-shape (ken-flagged
+ *         ftos.ww:411 refactor target), 16B with align-8 tail
+ *       * {i64,i32}                 — narrow-tail (#169 maxalign-8
+ *         tail-padded ABI)
+ *       * {i32,i32,i32}             — maxalign 4, slot-padded 16B
+ *         but ABI 12B (cstage struct_arg_size returns 12, both
+ *         stages still emit 2-word push since stsz>8)
+ *   - cs==ww runtime exit codes for the same shapes
+ *   - Inferral paths covered:
+ *       * `let p = make(...);`            (direct N_CALL infer)
+ *       * `let q = make(...); let p = q;` (N_IDENT-rhs infer chain)
+ *       * `let p = make_big(...);` for >24B sret (no register-ABI
+ *         push, but exercises let_isarray=false sret-recv → ident
+ *         push path)
+ *   - Branched callee (per #105 lesson — single-return masks
+ *     reg-routing via coincidence): both `make` and the consumer
+ *     branch on a flag so the GP register routing is exercised
+ *     through both arms.
+ *
+ * WHAT THIS DOES NOT COVER (separate filed bugs — do NOT bundle)
+ *   - #173: `let p = call_returning_tagged()!` drops CX/word1 on
+ *     receive (wwstage) and elides the CALL entirely (cstage). Live
+ *     miscompile, separate impl.
+ *   - #176: `let x = w.p` where p is a struct field — wwstage emits
+ *     1-word memcpy (under-copy of nested-struct field).
+ *   - #175: `let p = arr[0]` — both stages buggy in different ways.
+ *   - #177: aliased struct return (`type alias_p = point;
+ *     fn make() alias_p`) — cstage emits 1-word push (OPPOSITE of
+ *     the #16 stated symptom polarity).
+ *   - #174: `let p = call(): T;` cast in rhs — cstage drops the
+ *     call. Both-stages broken.
+ *
+ * GATE POLARITY: this file must stay GREEN. A red here means one of
+ * the closing commits regressed. Bisect against the 4 cited commits.
+ */
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+#include <sys/stat.h>
+#include <sys/wait.h>
+
+static int
+runwait(const char *cmd)
+{
+	int rc = system(cmd);
+	if (rc == -1) return -1;
+	if (WIFEXITED(rc)) return WEXITSTATUS(rc);
+	return -1;
+}
+
+struct row { const char *label; const char *src; int want; };
+
+static const struct row rows[] = {
+	/* 1. Canonical {i64,i64} — `let p = make(0);` inferred, then
+	 * `sum(p)` passes p as the struct arg. Branched callee on flag.
+	 * Returns p.a + p.b = 10 + 20 = 30. */
+	{ "i64_i64_infer_direct",
+	  "type point = struct { a: i64, b: i64 };\n"
+	  "fn make(flag: i32) point = {\n"
+	  "    if (flag == 0) { return point { a = 10i64, b = 20i64 }; };\n"
+	  "    return point { a = 100i64, b = 200i64 };\n"
+	  "};\n"
+	  "fn sum(p: point, which: i32) i32 = {\n"
+	  "    if (which == 0) { return (p.a + p.b): i32; };\n"
+	  "    return (p.a - p.b): i32;\n"
+	  "};\n"
+	  "fn main() i32 = {\n"
+	  "    let p = make(0);\n"
+	  "    return sum(p, 0);\n"
+	  "};\n",
+	  30 },
+	/* 2. {u32,i64} — decf32-shape. The narrow-mantissa-first then
+	 * widening-exponent layout is the strconv ftos.ww:411 decf32
+	 * (ken-flagged as one-refactor-away). Returns
+	 * (mantissa: i64) + exponent = 7 + 13 = 20. */
+	{ "u32_i64_decf_infer",
+	  "type decf = struct { mantissa: u32, exponent: i64 };\n"
+	  "fn make(flag: i32) decf = {\n"
+	  "    if (flag == 0) { return decf { mantissa = 7u32, exponent = 13i64 }; };\n"
+	  "    return decf { mantissa = 99u32, exponent = -1i64 };\n"
+	  "};\n"
+	  "fn use_(d: decf, which: i32) i32 = {\n"
+	  "    if (which == 0) { return ((d.mantissa: i64) + d.exponent): i32; };\n"
+	  "    return ((d.mantissa: i64) - d.exponent): i32;\n"
+	  "};\n"
+	  "fn main() i32 = {\n"
+	  "    let d = make(0);\n"
+	  "    return use_(d, 0);\n"
+	  "};\n",
+	  20 },
+	/* 3. {i64,i32} narrow-tail — natural 12B, maxalign 8, ABI 16B
+	 * via #169 structabisize round-up. Branched callee on flag.
+	 * Returns p.a + (p.b: i64) = 50 + 7 = 57. */
+	{ "i64_i32_narrow_tail_infer",
+	  "type ntail = struct { a: i64, b: i32 };\n"
+	  "fn make(flag: i32) ntail = {\n"
+	  "    if (flag == 0) { return ntail { a = 50i64, b = 7i32 }; };\n"
+	  "    return ntail { a = 500i64, b = 70i32 };\n"
+	  "};\n"
+	  "fn use_(p: ntail, which: i32) i32 = {\n"
+	  "    if (which == 0) { return (p.a + (p.b: i64)): i32; };\n"
+	  "    return (p.a - (p.b: i64)): i32;\n"
+	  "};\n"
+	  "fn main() i32 = {\n"
+	  "    let p = make(0);\n"
+	  "    return use_(p, 0);\n"
+	  "};\n",
+	  57 },
+	/* 4. {i32,i32,i32} — maxalign 4, ABI 12B (cstage); wwstage si
+	 * .totsize 16. Both stages still push 2 words since stsz > 8;
+	 * the 2-word push is THE bug #16 watched for. Returns
+	 * p.a + p.b + p.c = 1 + 2 + 3 = 6. */
+	{ "i32_x3_maxalign4_infer",
+	  "type three = struct { a: i32, b: i32, c: i32 };\n"
+	  "fn make(flag: i32) three = {\n"
+	  "    if (flag == 0) { return three { a = 1i32, b = 2i32, c = 3i32 }; };\n"
+	  "    return three { a = 10i32, b = 20i32, c = 30i32 };\n"
+	  "};\n"
+	  "fn use_(p: three, which: i32) i32 = {\n"
+	  "    if (which == 0) { return p.a + p.b + p.c; };\n"
+	  "    return p.a * p.b * p.c;\n"
+	  "};\n"
+	  "fn main() i32 = {\n"
+	  "    let p = make(0);\n"
+	  "    return use_(p, 0);\n"
+	  "};\n",
+	  6 },
+	/* 5. Ident-rhs inference chain — `let p = q;` where q itself
+	 * was inferred from a call. Pre-bail-rearm the checker's
+	 * `n.lhs = src` walk had to propagate q's resolved type through
+	 * exprtype(N_IDENT); a stale path would leave p's lc.tnode nil
+	 * and structparamsize → 0 → 1-word push. Returns
+	 * p.a + p.b = 11 + 22 = 33. */
+	{ "ident_rhs_chain_infer",
+	  "type point = struct { a: i64, b: i64 };\n"
+	  "fn make(flag: i32) point = {\n"
+	  "    if (flag == 0) { return point { a = 11i64, b = 22i64 }; };\n"
+	  "    return point { a = 110i64, b = 220i64 };\n"
+	  "};\n"
+	  "fn sum(p: point, which: i32) i32 = {\n"
+	  "    if (which == 0) { return (p.a + p.b): i32; };\n"
+	  "    return (p.a - p.b): i32;\n"
+	  "};\n"
+	  "fn main() i32 = {\n"
+	  "    let q = make(0);\n"
+	  "    let p = q;\n"
+	  "    return sum(p, 0);\n"
+	  "};\n",
+	  33 },
+	/* 6. >24B sret RECEIVE — exercises the cglet sret-dest wiring
+	 * (selfhost/cmd/wcc/cgenstmt.ww:1231 callsretsize branch). The
+	 * let's own slot is the hidden RDI dest pointer; the callee
+	 * writes through it. The struct is then passed BY POINTER to
+	 * the consumer (NOT by value) — the by-value >24B param ABI is
+	 * orthogonal to #16's call-arg-push scope and has its own
+	 * filed gaps. Returns
+	 * p.a + p.b + p.c + p.d = 1 + 2 + 3 + 4 = 10. */
+	{ "big_sret_infer_then_ptr_arg",
+	  "type big = struct { a: i64, b: i64, c: i64, d: i64 };\n"
+	  "fn make(flag: i32) big = {\n"
+	  "    if (flag == 0) { return big { a = 1i64, b = 2i64, c = 3i64, d = 4i64 }; };\n"
+	  "    return big { a = 10i64, b = 20i64, c = 30i64, d = 40i64 };\n"
+	  "};\n"
+	  "fn use_(p: *big, which: i32) i32 = {\n"
+	  "    if (which == 0) { return (p.a + p.b + p.c + p.d): i32; };\n"
+	  "    return (p.a * p.b * p.c * p.d): i32;\n"
+	  "};\n"
+	  "fn main() i32 = {\n"
+	  "    let p = make(0);\n"
+	  "    return use_(&p, 0);\n"
+	  "};\n",
+	  10 },
+};
+
+static int
+run_driver(const char *driver, const struct row *r, int i)
+{
+	char src[64], tmpdir[64], cmd[1024];
+	snprintf(src, sizeof src, "/tmp/wcisp_%d_%d.ww", getpid(), i);
+	snprintf(tmpdir, sizeof tmpdir, "/tmp/wcisp_%d_d_%d", getpid(), i);
+
+	FILE *f = fopen(src, "wb");
+	if (!f) return -1;
+	fputs(r->src, f);
+	fclose(f);
+
+	mkdir(tmpdir, 0755);
+	/* timeout 180 per repo convention (cf. 760); test/run does not
+	 * bound individual binaries, so an unguarded hang from a future
+	 * cgen regression would stall make test instead of redding here. */
+	snprintf(cmd, sizeof cmd, "cd %s && timeout 180 %s build %s 2>/dev/null",
+	    tmpdir, driver, src);
+	if (runwait(cmd) != 0) {
+		fprintf(stderr, "row[%s]: build via %s failed\n",
+		    r->label, driver);
+		unlink(src); rmdir(tmpdir);
+		return -1;
+	}
+
+	const char *base = strrchr(src, '/');
+	base = base ? base + 1 : src;
+	char outbin[128];
+	snprintf(outbin, sizeof outbin, "%s/%s", tmpdir, base);
+	char *dot = strrchr(outbin, '.');
+	if (dot && strcmp(dot, ".ww") == 0) *dot = '\0';
+	int got = runwait(outbin);
+
+	unlink(src); unlink(outbin); rmdir(tmpdir);
+	return got;
+}
+
+/* asm_byte_identical — diff w6c vs w6c_ww text output. The closing
+ * commits (ea1579a + 7198937 + 39f9267 + 66a91c8) ensure both stages
+ * emit the same struct-arg push width for every shape; a red here
+ * means one of those reverted (#16 surfaces). */
+static int
+asm_byte_identical(const char *bin, const struct row *r, int i)
+{
+	char src[64], cs[64], ws[64], cmd[1024];
+	snprintf(src, sizeof src, "/tmp/wcisp_asm_%d_%d.ww", getpid(), i);
+	snprintf(cs,  sizeof cs,  "/tmp/wcisp_asm_%d_%d_c.s", getpid(), i);
+	snprintf(ws,  sizeof ws,  "/tmp/wcisp_asm_%d_%d_w.s", getpid(), i);
+
+	FILE *f = fopen(src, "wb");
+	if (!f) return -1;
+	fputs(r->src, f);
+	fclose(f);
+
+	snprintf(cmd, sizeof cmd, "timeout 180 %s/w6c -o %s %s 2>/dev/null",
+	    bin, cs, src);
+	if (runwait(cmd) != 0) {
+		fprintf(stderr, "row[%s]: w6c errored\n", r->label);
+		unlink(src);
+		return -1;
+	}
+	snprintf(cmd, sizeof cmd, "timeout 180 %s/w6c_ww -o %s %s 2>/dev/null",
+	    bin, ws, src);
+	if (runwait(cmd) != 0) {
+		fprintf(stderr, "row[%s]: w6c_ww errored\n", r->label);
+		unlink(src); unlink(cs);
+		return -1;
+	}
+
+	FILE *fc = fopen(cs, "rb");
+	FILE *fw = fopen(ws, "rb");
+	int rc = 0;
+	if (!fc || !fw) {
+		rc = -1;
+	} else {
+		for (;;) {
+			int a = fgetc(fc);
+			int b = fgetc(fw);
+			if (a != b) { rc = -1; break; }
+			if (a == EOF) break;
+		}
+	}
+	if (fc) fclose(fc);
+	if (fw) fclose(fw);
+	if (rc != 0)
+		fprintf(stderr, "row[%s]: cstage vs wwstage asm differs\n",
+		    r->label);
+	unlink(src); unlink(cs); unlink(ws);
+	return rc;
+}
+
+int
+main(void)
+{
+	const char *bin = getenv("BIN");
+	if (!bin) bin = "out/bin";
+	char absbin[1024];
+	if (bin[0] != '/') {
+		char cwd[1024];
+		if (getcwd(cwd, sizeof cwd) == NULL) return 1;
+		snprintf(absbin, sizeof absbin, "%s/%s", cwd, bin);
+		bin = absbin;
+	}
+
+	char cdrv[1024];
+	snprintf(cdrv, sizeof cdrv, "%s/ww", bin);
+	char wdrv[1024];
+	snprintf(wdrv, sizeof wdrv, "%s/ww_ww", bin);
+
+	struct { const char *name; const char *path; int gated_on_existence; }
+	drivers[] = {
+		{ "cstage",  cdrv, 0 },
+		{ "wwstage", wdrv, 1 },
+		{ NULL, NULL, 0 },
+	};
+
+	int n = (int)(sizeof rows / sizeof rows[0]);
+	int total = 0, fail = 0;
+
+	for (int d = 0; drivers[d].name; d++) {
+		if (drivers[d].gated_on_existence
+		    && access(drivers[d].path, X_OK) != 0) {
+			fprintf(stderr, "inferred_struct_arg_push: skip %s (no %s)\n",
+			    drivers[d].name, drivers[d].path);
+			continue;
+		}
+		for (int i = 0; i < n; i++) {
+			int got = run_driver(drivers[d].path, &rows[i], i);
+			total++;
+			if (got != rows[i].want) {
+				fprintf(stderr,
+				    "inferred_struct_arg_push[%s][%s]: exit=%d want=%d\n",
+				    drivers[d].name, rows[i].label,
+				    got, rows[i].want);
+				fail++;
+			}
+		}
+	}
+
+	if (access(wdrv, X_OK) == 0) {
+		for (int i = 0; i < n; i++) {
+			total++;
+			if (asm_byte_identical(bin, &rows[i], i) != 0)
+				fail++;
+		}
+	}
+
+	if (fail) {
+		fprintf(stderr,
+		    "inferred_struct_arg_push: %d/%d fixtures failed\n",
+		    fail, total);
+		return 1;
+	}
+	printf("inferred_struct_arg_push: %d/%d ok\n", total, total);
+	return 0;
+}