fix(hashline): prevented exposing terminal newline as an addressable row

- Added `splitAddressableFileLines` to strip terminal newlines from line addressability without removing genuine blank lines.
- Updated coding-agent read tool context parsing to use addressable file lines.

packages/hashline/CHANGELOG.md

@@ -2,9 +2,6 @@
 
 ## [Unreleased]
 
-### Fixed
-
-- Stopped `formatNumberedLines` from exposing a terminal newline as an editable blank line; deleting that synthetic row previously produced a misleading no-op.
 
 ### Added
 
@@ -13,6 +10,7 @@
 ### Fixed
 
 - Fixed Rust lifetimes blinding the delimiter-balance scanner. `'` entered string state to end-of-line, so `&'static str {` hid its opening brace; a replacement range swallowing such a signature line looked balance-neutral and the mid-block advisory never fired, silently deleting the signature. Single-quote lexing is now language-aware: on `.rs` targets, `'` opens a literal only when it lexes as a real char literal (`'a'`, `'\n'`, `'\u{7FFF}'`), and lifetimes stay ordinary characters — apostrophes are never paired across lifetimes, which would swallow the delimiters between them (`<'a>(x: &'a str)`).
+- Fixed hashline reads exposing a terminal newline as an editable blank row. `splitAddressableFileLines` now removes that sentinel before consumers build line anchors while retaining genuine blank lines.
 
 ## [17.2.12] - 2026-08-08
 

packages/hashline/src/format.ts

@@ -140,12 +140,19 @@ export function formatNumberedLine(lineNumber: number, line: string): string {
 }
 
 /**
- * Format file text with hashline-mode line-number prefixes for display.
- * A terminal newline terminates the preceding line; it is not an addressable
- * blank line.
+ * Split LF-delimited file text into lines hashline anchors can address.
+ * A terminal newline terminates the preceding line; it is not content.
  */
-export function formatNumberedLines(text: string, startLine = 1): string {
+export function splitAddressableFileLines(text: string): string[] {
 	const lines = text.split("\n");
 	if (lines.length > 1 && lines[lines.length - 1] === "") lines.pop();
-	return lines.map((line, i) => formatNumberedLine(startLine + i, line)).join("\n");
+	return lines;
+}
+
+/** Format file text with hashline-mode line-number prefixes for display. */
+export function formatNumberedLines(text: string, startLine = 1): string {
+	return text
+		.split("\n")
+		.map((line, i) => formatNumberedLine(startLine + i, line))
+		.join("\n");
 }

packages/hashline/test/format-v2.test.ts

@@ -5,6 +5,7 @@ import {
 	parseLid,
 	parsePatch,
 	parsePatchStreaming,
+	splitAddressableFileLines,
 	Tokenizer,
 } from "@oh-my-pi/hashline";
 
@@ -105,9 +106,14 @@ describe("hashline format v4", () => {
 		expect(applyEdits("a\nb\n", edits).text).toBe("a\nb\n");
 	});
 
-	it("does not expose the terminal newline as an editable blank line", () => {
-		expect(formatNumberedLines("a\nb\n")).toBe("1:a\n2:b");
-		expect(formatNumberedLines("a\nb\n\n")).toBe("1:a\n2:b\n3:");
+	it("separates terminal newline sentinels from addressable file lines", () => {
+		expect(splitAddressableFileLines("a\nb\n")).toEqual(["a", "b"]);
+		expect(splitAddressableFileLines("a\nb\n\n")).toEqual(["a", "b", ""]);
+	});
+
+	it("keeps a selected terminal blank line when formatting", () => {
+		const selected = splitAddressableFileLines("a\n\nb\n").slice(0, 2).join("\n");
+		expect(formatNumberedLines(selected)).toBe("1:a\n2:");
 	});
 
 	it("treats a cut range ending at the trailing sentinel as ending at the last real line", () => {