diff --git a/selfhost/cmd/ww/main.combined.ww b/selfhost/cmd/ww/main.combined.ww
index 4d0b0b4d..88e043c7 100644
--- a/selfhost/cmd/ww/main.combined.ww
+++ b/selfhost/cmd/ww/main.combined.ww
@@ -3323,32 +3323,38 @@ fn expand(c: *expctx, pathcs: *u8) void = {
 // starts with `package <name>;` return the package name as a fresh
 // heap-allocated NUL-terminated *u8, else nil. Same shape as cstage
 // peek_package.
+//
+// Reads the WHOLE file (via slurp), not a fixed prefix: cstage's
+// peek_package scans line-by-line with fgets and no total cap, stopping
+// at the first non-comment-non-blank line. A prior 2048-byte read cap
+// here diverged from cstage on files whose `package` decl sits behind a
+// >2048-byte comment header (strconv decimal/ftos/stof, memio) —
+// returning nil and making the #16 D-i injection asymmetric (rule-10
+// break, byte-id divergence in the regenerated combined). The corpus has
+// no line >2047 chars, so a whole-file line scan matches cstage's
+// per-line fgets byte-for-byte on every real input.
 fn peekpackage(pathcs: *u8) *u8 = {
-	let fd: i32 = os.open(pathstr(pathcs), os.flag.RDONLY, 0i32);
-	if (fd < 0) { return nil; };
-	let buf: []u8 = alloc([], 2048u64)!;
-	buf.len = 2048;
-	let n: i64 = os.read(fd, buf.ptr, 2048u64);
-	os.close(fd);
-	if (n <= 0i64) { return nil; };
-	let nu: u64 = n: u64;
+	let bufp: *u8;
+	let nu: u64;
+	bufp, nu = slurp(pathcs);
+	if (bufp == nil) { return nil; };
 	let p: u64 = 0u64;
 	for (p < nu) {
 		let q: u64 = p;
 		for (q < nu) {
-			if (buf[q] == 10u8) { break; };	// '\n'
+			if (bufp[q] == 10u8) { break; };	// '\n'
 			q += 1u64;
 		};
 		let s: u64 = p;
 		for (s < q) {
-			if (buf[s] != 32u8) {
-				if (buf[s] != 9u8) { break; };
+			if (bufp[s] != 32u8) {
+				if (bufp[s] != 9u8) { break; };
 			};
 			s += 1u64;
 		};
 		if (s < q) {
 			let line: str;
-			line.ptr = buf.ptr + s;
+			line.ptr = bufp + s;
 			line.len = (q - s): i32;
 			// hasprefix("//") subsumes the old s+1<q guard.
 			if (strings.hasprefix(line, "//")) {
@@ -3356,22 +3362,22 @@ fn peekpackage(pathcs: *u8) *u8 = {
 				continue;
 			};
 			// s+8<=q guard kept: hasprefix("package") needs only 7
-			// bytes, but the sep read at buf[s+7] needs s+7 < q.
+			// bytes, but the sep read at bufp[s+7] needs s+7 < q.
 			if (s + 8u64 <= q) {
 				if (strings.hasprefix(line, "package")) {
-					let sep: u8 = buf[s + 7u64];
+					let sep: u8 = bufp[s + 7u64];
 					if (sep == 32u8) { }
 					else { if (sep != 9u8) { return nil; }; };
 					let t: u64 = s + 8u64;
 					for (t < q) {
-						if (buf[t] != 32u8) {
-							if (buf[t] != 9u8) { break; };
+						if (bufp[t] != 32u8) {
+							if (bufp[t] != 9u8) { break; };
 						};
 						t += 1u64;
 					};
 					let start: u64 = t;
 					for (t < q) {
-						let ch: u8 = buf[t];
+						let ch: u8 = bufp[t];
 						let isalpha: bool = false;
 						if (ch >= 97u8) { if (ch <= 122u8) { isalpha = true; }; };
 						if (ch >= 65u8)  { if (ch <= 90u8)  { isalpha = true; }; };
@@ -3384,7 +3390,7 @@ fn peekpackage(pathcs: *u8) *u8 = {
 					if (plen == 0u64) { return nil; };
 					let r: []u8 = alloc([], plen + 1u64)!;
 					let k: u64 = 0u64;
-					for (k < plen) { r[k] = buf[start + k]; k += 1u64; };
+					for (k < plen) { r[k] = bufp[start + k]; k += 1u64; };
 					r[plen] = 0u8;
 					return r.ptr;
 				};
diff --git a/selfhost/cmd/ww/main.ww b/selfhost/cmd/ww/main.ww
index e9136ea4..c2baefe2 100644
--- a/selfhost/cmd/ww/main.ww
+++ b/selfhost/cmd/ww/main.ww
@@ -537,32 +537,38 @@ fn expand(c: *expctx, pathcs: *u8) void = {
 // starts with `package <name>;` return the package name as a fresh
 // heap-allocated NUL-terminated *u8, else nil. Same shape as cstage
 // peek_package.
+//
+// Reads the WHOLE file (via slurp), not a fixed prefix: cstage's
+// peek_package scans line-by-line with fgets and no total cap, stopping
+// at the first non-comment-non-blank line. A prior 2048-byte read cap
+// here diverged from cstage on files whose `package` decl sits behind a
+// >2048-byte comment header (strconv decimal/ftos/stof, memio) —
+// returning nil and making the #16 D-i injection asymmetric (rule-10
+// break, byte-id divergence in the regenerated combined). The corpus has
+// no line >2047 chars, so a whole-file line scan matches cstage's
+// per-line fgets byte-for-byte on every real input.
 fn peekpackage(pathcs: *u8) *u8 = {
-	let fd: i32 = os.open(pathstr(pathcs), os.flag.RDONLY, 0i32);
-	if (fd < 0) { return nil; };
-	let buf: []u8 = alloc([], 2048u64)!;
-	buf.len = 2048;
-	let n: i64 = os.read(fd, buf.ptr, 2048u64);
-	os.close(fd);
-	if (n <= 0i64) { return nil; };
-	let nu: u64 = n: u64;
+	let bufp: *u8;
+	let nu: u64;
+	bufp, nu = slurp(pathcs);
+	if (bufp == nil) { return nil; };
 	let p: u64 = 0u64;
 	for (p < nu) {
 		let q: u64 = p;
 		for (q < nu) {
-			if (buf[q] == 10u8) { break; };	// '\n'
+			if (bufp[q] == 10u8) { break; };	// '\n'
 			q += 1u64;
 		};
 		let s: u64 = p;
 		for (s < q) {
-			if (buf[s] != 32u8) {
-				if (buf[s] != 9u8) { break; };
+			if (bufp[s] != 32u8) {
+				if (bufp[s] != 9u8) { break; };
 			};
 			s += 1u64;
 		};
 		if (s < q) {
 			let line: str;
-			line.ptr = buf.ptr + s;
+			line.ptr = bufp + s;
 			line.len = (q - s): i32;
 			// hasprefix("//") subsumes the old s+1<q guard.
 			if (strings.hasprefix(line, "//")) {
@@ -570,22 +576,22 @@ fn peekpackage(pathcs: *u8) *u8 = {
 				continue;
 			};
 			// s+8<=q guard kept: hasprefix("package") needs only 7
-			// bytes, but the sep read at buf[s+7] needs s+7 < q.
+			// bytes, but the sep read at bufp[s+7] needs s+7 < q.
 			if (s + 8u64 <= q) {
 				if (strings.hasprefix(line, "package")) {
-					let sep: u8 = buf[s + 7u64];
+					let sep: u8 = bufp[s + 7u64];
 					if (sep == 32u8) { }
 					else { if (sep != 9u8) { return nil; }; };
 					let t: u64 = s + 8u64;
 					for (t < q) {
-						if (buf[t] != 32u8) {
-							if (buf[t] != 9u8) { break; };
+						if (bufp[t] != 32u8) {
+							if (bufp[t] != 9u8) { break; };
 						};
 						t += 1u64;
 					};
 					let start: u64 = t;
 					for (t < q) {
-						let ch: u8 = buf[t];
+						let ch: u8 = bufp[t];
 						let isalpha: bool = false;
 						if (ch >= 97u8) { if (ch <= 122u8) { isalpha = true; }; };
 						if (ch >= 65u8)  { if (ch <= 90u8)  { isalpha = true; }; };
@@ -598,7 +604,7 @@ fn peekpackage(pathcs: *u8) *u8 = {
 					if (plen == 0u64) { return nil; };
 					let r: []u8 = alloc([], plen + 1u64)!;
 					let k: u64 = 0u64;
-					for (k < plen) { r[k] = buf[start + k]; k += 1u64; };
+					for (k < plen) { r[k] = bufp[start + k]; k += 1u64; };
 					r[plen] = 0u8;
 					return r.ptr;
 				};