diff --git a/packages/coding-agent/src/tools/path-utils.ts b/packages/coding-agent/src/tools/path-utils.ts
index 645f1390c..da6a96225 100644
--- a/packages/coding-agent/src/tools/path-utils.ts
+++ b/packages/coding-agent/src/tools/path-utils.ts
@@ -7,14 +7,22 @@ import { InternalUrlRouter, type LocalProtocolOptions } from "../internal-urls";
 import { ToolError } from "./tool-errors";
 
 const UNICODE_SPACES = /[\u00A0\u2000-\u200A\u202F\u205F\u3000]/g;
-const FILE_LINE_RANGE_RE = /^(?:L?\d+(?:[-+]L?\d+|-)?(?:,L?\d+(?:[-+]L?\d+|-)?)*|raw|conflicts)$/i;
-const FILE_LINE_RANGE_ONLY_RE = /^L?\d+(?:[-+]L?\d+|-)?(?:,L?\d+(?:[-+]L?\d+|-)?)*$/i;
+// A single line-range chunk: `N`, `N-M`, `N+K`, or open-ended `N-`. `..` is
+// accepted everywhere `-` is, as a forgiving alias for Rust/Python-style ranges
+// (e.g. `2724..2727` == `2724-2727`, `2724..` == `2724-`); it is normalized to
+// `-` in parseLineRangeChunk. Keep this fragment and LINE_RANGE_CHUNK_RE in sync.
+const RANGE_CHUNK_SRC = String.raw`L?\d+(?:(?:[-+]|\.\.)L?\d+|-|\.\.)?`;
+const RANGE_LIST_SRC = `${RANGE_CHUNK_SRC}(?:,${RANGE_CHUNK_SRC})*`;
+const FILE_LINE_RANGE_RE = new RegExp(`^(?:${RANGE_LIST_SRC}|raw|conflicts)$`, "i");
+const FILE_LINE_RANGE_ONLY_RE = new RegExp(`^${RANGE_LIST_SRC}$`, "i");
 const FILE_RAW_ONLY_RE = /^raw$/i;
 // Permissive selector chunk for internal URLs — accepts well-formed selectors
 // plus common malformed shapes (e.g. `:-N`) so the read tool peels the entire
 // selector chain off before dispatching to a protocol handler.
-const INTERNAL_URL_SELECTOR_PART_RE =
-	/^(?:raw|conflicts|L?\d+(?:[-+]L?\d+|-)?(?:,L?\d+(?:[-+]L?\d+|-)?)*|-\d+(?:[-+]\d+)?)$/i;
+const INTERNAL_URL_SELECTOR_PART_RE = new RegExp(
+	String.raw`^(?:raw|conflicts|${RANGE_LIST_SRC}|-\d+(?:[-+]\d+)?)$`,
+	"i",
+);
 // Schemes whose host grammar is identifier-shaped, so any trailing
 // `:<selector-chunk>` is unambiguously a read-tool selector. `mcp://` is
 // excluded because mcp resource URIs may legitimately contain colons.
@@ -144,9 +152,9 @@ export interface LineRange {
 	endLine: number | undefined;
 }
 
-const LINE_RANGE_CHUNK_RE = /^L?(\d+)(?:([-+])L?(\d+)?)?$/i;
+const LINE_RANGE_CHUNK_RE = /^L?(\d+)(?:(\.\.|[-+])L?(\d+)?)?$/i;
 
-/** Parse a single `N`, `N-M`, `N-`, or `N+K` chunk. Throws via {@link ToolError} on invalid bounds. */
+/** Parse a single `N`, `N-M`, `N-`, `N+K`, or `..`-aliased (`N..M`, `N..`) chunk. Throws via {@link ToolError} on invalid bounds. */
 export function parseLineRangeChunk(sel: string): LineRange | null {
 	const lineMatch = LINE_RANGE_CHUNK_RE.exec(sel);
 	if (!lineMatch) return null;
@@ -154,7 +162,8 @@ export function parseLineRangeChunk(sel: string): LineRange | null {
 	if (rawStart < 1) {
 		throw new ToolError("Line selector 0 is invalid; lines are 1-indexed. Use :1.");
 	}
-	const sep = lineMatch[2];
+	// `..` is a forgiving alias for `-` (e.g. `2724..2727` == `2724-2727`).
+	const sep = lineMatch[2] === ".." ? "-" : lineMatch[2];
 	const rhs = lineMatch[3] ? Number.parseInt(lineMatch[3], 10) : undefined;
 	let rawEnd: number | undefined;
 	if (sep === "+") {
diff --git a/packages/coding-agent/test/read-multi-range.test.ts b/packages/coding-agent/test/read-multi-range.test.ts
index 61554edff..6072369f8 100644
--- a/packages/coding-agent/test/read-multi-range.test.ts
+++ b/packages/coding-agent/test/read-multi-range.test.ts
@@ -129,6 +129,36 @@ describe("read tool multi-range selector", () => {
 		expect(text).not.toContain("line 19");
 	});
 
+	it("accepts `..` as a forgiving alias for `-`, producing identical output", async () => {
+		const filePath = path.join(tmpDir, "numbered.txt");
+		await fs.writeFile(filePath, makeNumberedContent(30));
+
+		const tool = new ReadTool(createSession(tmpDir));
+		const dotdot = textOutput(await tool.execute("call-dotdot", { path: `${filePath}:3..5` }));
+		const dash = textOutput(await tool.execute("call-dash", { path: `${filePath}:3-5` }));
+
+		expect(dotdot).toContain("line 3");
+		expect(dotdot).toContain("line 5");
+		// `..` must be a pure alias: byte-for-byte identical to the `-` form.
+		expect(dotdot).toBe(dash);
+	});
+
+	it("accepts `..` in multi-range selectors", async () => {
+		const filePath = path.join(tmpDir, "numbered.txt");
+		await fs.writeFile(filePath, makeNumberedContent(50));
+
+		const tool = new ReadTool(createSession(tmpDir));
+		const result = await tool.execute("call-dotdot-multi", { path: `${filePath}:3..5,20..22` });
+		const text = textOutput(result);
+
+		expect(text).toContain("line 3");
+		expect(text).toContain("line 5");
+		expect(text).toContain("line 20");
+		expect(text).toContain("line 22");
+		expect(text).not.toContain("line 10");
+		expect(text).toContain("…");
+	});
+
 	it("rejects multi-range selectors on directories", async () => {
 		const tool = new ReadTool(createSession(tmpDir));
 		await expect(tool.execute("call-dir", { path: `${tmpDir}:1-2,5-6` })).rejects.toThrow(
diff --git a/packages/coding-agent/test/tools/path-utils-dotdot-selector.test.ts b/packages/coding-agent/test/tools/path-utils-dotdot-selector.test.ts
new file mode 100644
index 000000000..ce9a6cf1f
--- /dev/null
+++ b/packages/coding-agent/test/tools/path-utils-dotdot-selector.test.ts
@@ -0,0 +1,46 @@
+import { describe, expect, it } from "bun:test";
+import { parseLineRangeChunk, parseLineRanges, splitPathAndSel } from "@oh-my-pi/pi-coding-agent/tools/path-utils";
+import { ToolError } from "@oh-my-pi/pi-coding-agent/tools/tool-errors";
+
+describe("`..` range selector alias", () => {
+	it("treats `N..M` as the inclusive range `N-M`", () => {
+		expect(parseLineRangeChunk("2724..2727")).toEqual({ startLine: 2724, endLine: 2727 });
+		// Same line count and bounds as the canonical dash form.
+		expect(parseLineRangeChunk("2724..2727")).toEqual(parseLineRangeChunk("2724-2727"));
+	});
+
+	it("treats trailing `N..` as open-ended, like `N-`", () => {
+		expect(parseLineRangeChunk("301..")).toEqual({ startLine: 301, endLine: undefined });
+		expect(parseLineRangeChunk("301..")).toEqual(parseLineRangeChunk("301-"));
+	});
+
+	it("accepts `..` inside comma-separated multi-range selectors", () => {
+		expect(parseLineRanges("3..5,20..22")).toEqual([
+			{ startLine: 3, endLine: 5 },
+			{ startLine: 20, endLine: 22 },
+		]);
+	});
+
+	it("allows mixing `..` and `-` separators across chunks", () => {
+		expect(parseLineRanges("3-5,20..22")).toEqual([
+			{ startLine: 3, endLine: 5 },
+			{ startLine: 20, endLine: 22 },
+		]);
+	});
+
+	it("rejects inverted `..` ranges with the same guard as `-`", () => {
+		expect(() => parseLineRangeChunk("2727..2724")).toThrow(ToolError);
+	});
+
+	it("peels a trailing `:N..M` selector off the path", () => {
+		expect(splitPathAndSel("packages/editor/src/Editor.ts:2724..2727")).toEqual({
+			path: "packages/editor/src/Editor.ts",
+			sel: "2724..2727",
+		});
+	});
+
+	it("does not mistake a `..` path segment for a selector", () => {
+		// No digits around the dots → still a plain path, not a range selector.
+		expect(splitPathAndSel("foo:../bar.ts")).toEqual({ path: "foo:../bar.ts" });
+	});
+});