diff --git a/Makefile b/Makefile
index c19ec793..88b9dda8 100644
--- a/Makefile
+++ b/Makefile
@@ -255,6 +255,7 @@ TESTS	= $(BIN)/test_smoke $(BIN)/test_lex $(BIN)/test_parse $(BIN)/test_check \
 	  $(BIN)/test_tagtupfieldsize_run \
 	  $(BIN)/test_arrlit_tail_zero_run \
 	  $(BIN)/test_defdim_slice_run \
+	  $(BIN)/test_trystr_run \
 	  $(BIN)/test_gunsigned_run \
 	  $(BIN)/test_taggedidx_run \
 	  $(BIN)/test_fnptrcollide_run \
@@ -734,6 +735,17 @@ $(BIN)/test_defdim_slice_run: test/wcc/989_defdim_slice_run.c \
 		$(LIB)/libwwrt.a | $(BIN)
 	$(CC) $(CFLAGS) -o $@ $<
 
+# 989_trystr_run (#16): `?`/`!` unwrap of a str-success tagged union shuffles
+# the str header for ANY operand shape + variant order, keyed off the stamped
+# operand type (not a name-keyed call-only first-variant lookup). Builds+runs
+# on BOTH driver twins (rule-10).
+$(BIN)/test_trystr_run: test/wcc/989_trystr_run.c \
+		$(BIN)/ww $(BIN)/ww_ww \
+		$(BIN)/w6c $(BIN)/w6a $(BIN)/w6l \
+		$(BIN)/w6c_ww $(BIN)/w6a_ww $(BIN)/w6l_ww \
+		$(LIB)/libwwrt.a | $(BIN)
+	$(CC) $(CFLAGS) -o $@ $<
+
 # 989_gunsigned_run (F7-c5, #25): a module-global unsigned ident on the
 # divide/shift/relational path must pick the unsigned opcode. Builds+runs on
 # BOTH driver twins (rule-10). CLASS-M — see the test header.
diff --git a/selfhost/cmd/w6c/main.combined.ww b/selfhost/cmd/w6c/main.combined.ww
index edb7a4a5..56982b2f 100644
--- a/selfhost/cmd/w6c/main.combined.ww
+++ b/selfhost/cmd/w6c/main.combined.ww
@@ -23738,42 +23738,13 @@ fn cgtryprop(c: *cgen, n: *node) void = {
 	// the codegen expects the success value in AX (and BX for str).
 	// AX=tag, DX=val0, CX=val1 from the call ABI. For str success,
 	// shuffle (DX,CX) → (AX,BX); else move DX → AX.
+	// #16: read the STAMPED operand's success-variant type (any source
+	// shape, any variant order), not a name-keyed call-only lookup of
+	// the first variant. Mirrors cstage cgen.c:10459-10466
+	// (success_is_str = type_isstr(succ_t at cg_tagged_success_tag)).
 	let succisstr: bool = false;
 	if (n.lhs != nil) {
-		if (n.lhs.kind == nkind.N_CALL) {
-			let callee: *node = n.lhs.lhs;
-			if (callee != nil) {
-				let cname: str;
-				cname.ptr = nil; cname.len = 0;
-				let cmod: str;
-				cmod.ptr = nil; cmod.len = 0;
-				if (callee.kind == nkind.N_IDENT) {
-					cname = callee.str;
-					cmod = c.curmod;
-				};
-				if (callee.kind == nkind.N_DOT) {
-					cname = callee.str;
-					if (callee.lhs != nil) {
-						if (callee.lhs.kind == nkind.N_IDENT) {
-							cmod = callee.lhs.str;
-						};
-					};
-				};
-				if (cname.len > 0) {
-					let rtyp: *node = fnretlookupmod(c, cname, cmod);
-					if (rtyp != nil) {
-						if (rtyp.kind == nkind.N_TTAGGED) {
-							let first: *node = rtyp.list;
-							if (first != nil) {
-								if (isstrtype(c, first)) {
-									succisstr = true;
-								};
-							};
-						};
-					};
-				};
-			};
-		};
+		succisstr = typeisstr(successvariant(n.lhs.type_: *tinfo));
 	};
 	if (succisstr) {
 		// str IS []u8: success arrives DX=ptr, CX=len, R8=cap
@@ -23836,42 +23807,11 @@ fn cgtryunw(c: *cgen, n: *node) void = {
 	if (cgtrytupleshift(c, n)) { return; };
 	if (cgtrytaggedshift(c, n)) { return; };
 	// Unwrap success value. (Same shuffle pattern as cgtryprop.)
+	// #16: stamped success-variant type, any source/order (twin of
+	// cgtryprop; cstage cgen.c:10595-10602).
 	let succisstr: bool = false;
 	if (n.lhs != nil) {
-		if (n.lhs.kind == nkind.N_CALL) {
-			let callee: *node = n.lhs.lhs;
-			if (callee != nil) {
-				let cname: str;
-				cname.ptr = nil; cname.len = 0;
-				let cmod: str;
-				cmod.ptr = nil; cmod.len = 0;
-				if (callee.kind == nkind.N_IDENT) {
-					cname = callee.str;
-					cmod = c.curmod;
-				};
-				if (callee.kind == nkind.N_DOT) {
-					cname = callee.str;
-					if (callee.lhs != nil) {
-						if (callee.lhs.kind == nkind.N_IDENT) {
-							cmod = callee.lhs.str;
-						};
-					};
-				};
-				if (cname.len > 0) {
-					let rtyp: *node = fnretlookupmod(c, cname, cmod);
-					if (rtyp != nil) {
-						if (rtyp.kind == nkind.N_TTAGGED) {
-							let first: *node = rtyp.list;
-							if (first != nil) {
-								if (isstrtype(c, first)) {
-									succisstr = true;
-								};
-							};
-						};
-					};
-				};
-			};
-		};
+		succisstr = typeisstr(successvariant(n.lhs.type_: *tinfo));
 	};
 	if (succisstr) {
 		// str IS []u8: success arrives DX=ptr, CX=len, R8=cap
diff --git a/selfhost/cmd/wcc/cgenexpr.ww b/selfhost/cmd/wcc/cgenexpr.ww
index 0d59129f..20bce72e 100644
--- a/selfhost/cmd/wcc/cgenexpr.ww
+++ b/selfhost/cmd/wcc/cgenexpr.ww
@@ -518,42 +518,13 @@ fn cgtryprop(c: *cgen, n: *node) void = {
 	// the codegen expects the success value in AX (and BX for str).
 	// AX=tag, DX=val0, CX=val1 from the call ABI. For str success,
 	// shuffle (DX,CX) → (AX,BX); else move DX → AX.
+	// #16: read the STAMPED operand's success-variant type (any source
+	// shape, any variant order), not a name-keyed call-only lookup of
+	// the first variant. Mirrors cstage cgen.c:10459-10466
+	// (success_is_str = type_isstr(succ_t at cg_tagged_success_tag)).
 	let succisstr: bool = false;
 	if (n.lhs != nil) {
-		if (n.lhs.kind == nkind.N_CALL) {
-			let callee: *node = n.lhs.lhs;
-			if (callee != nil) {
-				let cname: str;
-				cname.ptr = nil; cname.len = 0;
-				let cmod: str;
-				cmod.ptr = nil; cmod.len = 0;
-				if (callee.kind == nkind.N_IDENT) {
-					cname = callee.str;
-					cmod = c.curmod;
-				};
-				if (callee.kind == nkind.N_DOT) {
-					cname = callee.str;
-					if (callee.lhs != nil) {
-						if (callee.lhs.kind == nkind.N_IDENT) {
-							cmod = callee.lhs.str;
-						};
-					};
-				};
-				if (cname.len > 0) {
-					let rtyp: *node = fnretlookupmod(c, cname, cmod);
-					if (rtyp != nil) {
-						if (rtyp.kind == nkind.N_TTAGGED) {
-							let first: *node = rtyp.list;
-							if (first != nil) {
-								if (isstrtype(c, first)) {
-									succisstr = true;
-								};
-							};
-						};
-					};
-				};
-			};
-		};
+		succisstr = typeisstr(successvariant(n.lhs.type_: *tinfo));
 	};
 	if (succisstr) {
 		// str IS []u8: success arrives DX=ptr, CX=len, R8=cap
@@ -616,42 +587,11 @@ fn cgtryunw(c: *cgen, n: *node) void = {
 	if (cgtrytupleshift(c, n)) { return; };
 	if (cgtrytaggedshift(c, n)) { return; };
 	// Unwrap success value. (Same shuffle pattern as cgtryprop.)
+	// #16: stamped success-variant type, any source/order (twin of
+	// cgtryprop; cstage cgen.c:10595-10602).
 	let succisstr: bool = false;
 	if (n.lhs != nil) {
-		if (n.lhs.kind == nkind.N_CALL) {
-			let callee: *node = n.lhs.lhs;
-			if (callee != nil) {
-				let cname: str;
-				cname.ptr = nil; cname.len = 0;
-				let cmod: str;
-				cmod.ptr = nil; cmod.len = 0;
-				if (callee.kind == nkind.N_IDENT) {
-					cname = callee.str;
-					cmod = c.curmod;
-				};
-				if (callee.kind == nkind.N_DOT) {
-					cname = callee.str;
-					if (callee.lhs != nil) {
-						if (callee.lhs.kind == nkind.N_IDENT) {
-							cmod = callee.lhs.str;
-						};
-					};
-				};
-				if (cname.len > 0) {
-					let rtyp: *node = fnretlookupmod(c, cname, cmod);
-					if (rtyp != nil) {
-						if (rtyp.kind == nkind.N_TTAGGED) {
-							let first: *node = rtyp.list;
-							if (first != nil) {
-								if (isstrtype(c, first)) {
-									succisstr = true;
-								};
-							};
-						};
-					};
-				};
-			};
-		};
+		succisstr = typeisstr(successvariant(n.lhs.type_: *tinfo));
 	};
 	if (succisstr) {
 		// str IS []u8: success arrives DX=ptr, CX=len, R8=cap
diff --git a/selfhost/cmd/wwdump/main.combined.ww b/selfhost/cmd/wwdump/main.combined.ww
index 3ec59838..9c5c2c0f 100644
--- a/selfhost/cmd/wwdump/main.combined.ww
+++ b/selfhost/cmd/wwdump/main.combined.ww
@@ -23738,42 +23738,13 @@ fn cgtryprop(c: *cgen, n: *node) void = {
 	// the codegen expects the success value in AX (and BX for str).
 	// AX=tag, DX=val0, CX=val1 from the call ABI. For str success,
 	// shuffle (DX,CX) → (AX,BX); else move DX → AX.
+	// #16: read the STAMPED operand's success-variant type (any source
+	// shape, any variant order), not a name-keyed call-only lookup of
+	// the first variant. Mirrors cstage cgen.c:10459-10466
+	// (success_is_str = type_isstr(succ_t at cg_tagged_success_tag)).
 	let succisstr: bool = false;
 	if (n.lhs != nil) {
-		if (n.lhs.kind == nkind.N_CALL) {
-			let callee: *node = n.lhs.lhs;
-			if (callee != nil) {
-				let cname: str;
-				cname.ptr = nil; cname.len = 0;
-				let cmod: str;
-				cmod.ptr = nil; cmod.len = 0;
-				if (callee.kind == nkind.N_IDENT) {
-					cname = callee.str;
-					cmod = c.curmod;
-				};
-				if (callee.kind == nkind.N_DOT) {
-					cname = callee.str;
-					if (callee.lhs != nil) {
-						if (callee.lhs.kind == nkind.N_IDENT) {
-							cmod = callee.lhs.str;
-						};
-					};
-				};
-				if (cname.len > 0) {
-					let rtyp: *node = fnretlookupmod(c, cname, cmod);
-					if (rtyp != nil) {
-						if (rtyp.kind == nkind.N_TTAGGED) {
-							let first: *node = rtyp.list;
-							if (first != nil) {
-								if (isstrtype(c, first)) {
-									succisstr = true;
-								};
-							};
-						};
-					};
-				};
-			};
-		};
+		succisstr = typeisstr(successvariant(n.lhs.type_: *tinfo));
 	};
 	if (succisstr) {
 		// str IS []u8: success arrives DX=ptr, CX=len, R8=cap
@@ -23836,42 +23807,11 @@ fn cgtryunw(c: *cgen, n: *node) void = {
 	if (cgtrytupleshift(c, n)) { return; };
 	if (cgtrytaggedshift(c, n)) { return; };
 	// Unwrap success value. (Same shuffle pattern as cgtryprop.)
+	// #16: stamped success-variant type, any source/order (twin of
+	// cgtryprop; cstage cgen.c:10595-10602).
 	let succisstr: bool = false;
 	if (n.lhs != nil) {
-		if (n.lhs.kind == nkind.N_CALL) {
-			let callee: *node = n.lhs.lhs;
-			if (callee != nil) {
-				let cname: str;
-				cname.ptr = nil; cname.len = 0;
-				let cmod: str;
-				cmod.ptr = nil; cmod.len = 0;
-				if (callee.kind == nkind.N_IDENT) {
-					cname = callee.str;
-					cmod = c.curmod;
-				};
-				if (callee.kind == nkind.N_DOT) {
-					cname = callee.str;
-					if (callee.lhs != nil) {
-						if (callee.lhs.kind == nkind.N_IDENT) {
-							cmod = callee.lhs.str;
-						};
-					};
-				};
-				if (cname.len > 0) {
-					let rtyp: *node = fnretlookupmod(c, cname, cmod);
-					if (rtyp != nil) {
-						if (rtyp.kind == nkind.N_TTAGGED) {
-							let first: *node = rtyp.list;
-							if (first != nil) {
-								if (isstrtype(c, first)) {
-									succisstr = true;
-								};
-							};
-						};
-					};
-				};
-			};
-		};
+		succisstr = typeisstr(successvariant(n.lhs.type_: *tinfo));
 	};
 	if (succisstr) {
 		// str IS []u8: success arrives DX=ptr, CX=len, R8=cap
diff --git a/test/wcc/989_trystr_run.c b/test/wcc/989_trystr_run.c
new file mode 100644
index 00000000..3caaaa46
--- /dev/null
+++ b/test/wcc/989_trystr_run.c
@@ -0,0 +1,168 @@
+/*
+ * 989_trystr_run (#16) — the `?`/`!` unwrap of a str-success tagged union
+ * must shuffle the str header (DX,CX,R8) → (AX,BX,CX) for ANY operand shape
+ * and ANY variant order, keyed off the STAMPED operand type.
+ *
+ * THE BUG (wwstage only): cgtryprop/cgtryunw computed succisstr ONLY when the
+ * operand was an N_CALL, via a name-keyed fnretlookupmod on the callee leaf,
+ * and tested the FIRST variant (not the success variant). So an ident-source
+ * unwrap (`let r = mk(); r!`) and an error-first union (`(e|str)`) both
+ * dropped the `MOVQ CX,BX / MOVQ R8,CX` shuffle — the unwrapped str kept a
+ * stale len/cap. cstage reads success_is_str = type_isstr(succ_t) at
+ * cg_tagged_success_tag from the stamped operand type. THE FIX: read the
+ * stamped operand's success-variant type via successvariant()+typeisstr().
+ *
+ *   row             | shape                                  | exit (cs==ww)
+ *   ----------------+----------------------------------------+--------------
+ *   ident_source    | let r=mk(); junk; r!  → s.len          | 2  (was ww 40)
+ *   errfirst_call   | (e|str) mk2()!        → s.len          | 3
+ *   succfirst_call  | (str|e) mk()!  (control)               | 4
+ * A 40-byte `junk` str precedes the unwrap so a dropped shuffle leaks junk's
+ * len into s.len: pre-fix ident_source ran ww=40 vs cs=2 (silent overrun).
+ */
+#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_exit; };
+
+static const struct row rows[] = {
+	{ "ident_source",
+	  "package main;\n"
+	  "type e = !i32;\n"
+	  "fn mk() (str | e) = { return \"hi\"; };\n"
+	  "export fn main() i32 = {\n"
+	  "	let r: (str | e) = mk();\n"
+	  "	let junk: str = \"0123456789012345678901234567890123456789\";\n"
+	  "	let s: str = r!;\n"
+	  "	return s.len: i32;\n"
+	  "};\n",
+	  2 },
+
+	{ "errfirst_call",
+	  "package main;\n"
+	  "type e = !i32;\n"
+	  "fn mk2() (e | str) = { return \"abc\"; };\n"
+	  "export fn main() i32 = {\n"
+	  "	let junk: str = \"0123456789012345678901234567890123456789\";\n"
+	  "	let s3: str = mk2()!;\n"
+	  "	return s3.len: i32;\n"
+	  "};\n",
+	  3 },
+
+	{ "succfirst_call",
+	  "package main;\n"
+	  "type e = !i32;\n"
+	  "fn mk() (str | e) = { return \"wxyz\"; };\n"
+	  "export fn main() i32 = {\n"
+	  "	let junk: str = \"0123456789012345678901234567890123456789\";\n"
+	  "	let s: str = mk()!;\n"
+	  "	return s.len: i32;\n"
+	  "};\n",
+	  4 },
+};
+
+static int
+run_build(const char *driver, const struct row *r, int i)
+{
+	char src[64], tmpdir[64], cmd[1024];
+	snprintf(src, sizeof src, "/tmp/trystr_%d_%d.ww", getpid(), i);
+	snprintf(tmpdir, sizeof tmpdir, "/tmp/trystr_%d_d_%d", getpid(), i);
+
+	FILE *f = fopen(src, "wb");
+	if (!f) return -2;
+	fputs(r->src, f);
+	fclose(f);
+
+	mkdir(tmpdir, 0755);
+	snprintf(cmd, sizeof cmd, "cd %s && %s build %s 2>/dev/null",
+	    tmpdir, driver, src);
+	int brc = runwait(cmd);
+
+	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 = -1;
+	if (brc == 0) got = runwait(outbin);
+
+	unlink(src); unlink(outbin); rmdir(tmpdir);
+	return brc == 0 ? got : -1;
+}
+
+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], wdrv[1024];
+	snprintf(cdrv, sizeof cdrv, "%s/ww", bin);
+	snprintf(wdrv, sizeof wdrv, "%s/ww_ww", bin);
+	int have_ww = (access(wdrv, X_OK) == 0);
+
+	int n = (int)(sizeof rows / sizeof rows[0]);
+	int total = 0, fail = 0;
+
+	for (int i = 0; i < n; i++) {
+		total++;
+		int gc = run_build(cdrv, &rows[i], i);
+		if (gc < 0) {
+			fprintf(stderr, "trystr[cstage][%s]: build/run failed "
+			    "(got %d)\n", rows[i].label, gc);
+			fail++;
+			continue;
+		}
+		if (gc != rows[i].want_exit) {
+			fprintf(stderr, "trystr[cstage][%s]: exit=%d want=%d\n",
+			    rows[i].label, gc, rows[i].want_exit);
+			fail++;
+		}
+		if (!have_ww) {
+			fprintf(stderr, "trystr: skip wwstage (no %s)\n", wdrv);
+			continue;
+		}
+		int gw = run_build(wdrv, &rows[i], i);
+		if (gw != gc) {
+			fprintf(stderr, "trystr[%s]: cs=%d != ww=%d "
+			    "(str-success unwrap shuffle dropped — #16)\n",
+			    rows[i].label, gc, gw);
+			fail++;
+		}
+		if (gw != rows[i].want_exit) {
+			fprintf(stderr, "trystr[wwstage][%s]: exit=%d want=%d\n",
+			    rows[i].label, gw, rows[i].want_exit);
+			fail++;
+		}
+	}
+
+	if (fail) {
+		fprintf(stderr, "trystr_run: %d/%d checks failed\n",
+		    fail, total);
+		return 1;
+	}
+	printf("trystr_run: %d/%d ok\n", total, total);
+	return 0;
+}