perf(coding-agent): bound completed diff rendering

packages/coding-agent/test/tools/edit-renderer.test.ts

@@ -255,6 +255,19 @@ describe("editToolRenderer", () => {
 	it("caches completed diff rendering across stable frame renders", async () => {
 		const uiTheme = await getUiTheme();
 		let renderDiffCalls = 0;
+		let statsColorCalls = 0;
+		const countingTheme = new Proxy(uiTheme, {
+			get(target, property) {
+				if (property === "fg") {
+					return (color: Parameters<themeModule.Theme["fg"]>[0], text: string): string => {
+						if (color === "toolDiffAdded" && text === "+1") statsColorCalls++;
+						return target.fg(color, text);
+					};
+				}
+				const value = Reflect.get(target, property, target) as unknown;
+				return typeof value === "function" ? value.bind(target) : value;
+			},
+		});
 		const options = {
 			expanded: false,
 			isPartial: false,
@@ -275,17 +288,19 @@ describe("editToolRenderer", () => {
 				},
 			},
 			options,
-			uiTheme,
+			countingTheme,
 			{ file_path: "src/example.ts" },
 		);
 
 		component.render(160);
 		component.render(120);
 		expect(renderDiffCalls).toBe(1);
+		expect(statsColorCalls).toBe(1);
 
 		options.expanded = true;
 		component.render(120);
 		expect(renderDiffCalls).toBe(2);
+		expect(statsColorCalls).toBe(1);
 	});
 
 	it("computes the hashline preview diff once a single-line edit finishes streaming", async () => {
@@ -420,6 +435,27 @@ describe("editToolRenderer", () => {
 		expect(lines.filter(line => line.includes("+2/-1"))).toHaveLength(1);
 	});
 
+	it("bounds a completed diff that contains one oversized change hunk", async () => {
+		const uiTheme = await getUiTheme();
+		const diff = Array.from({ length: 1_000 }, (_, i) => `+${i + 1}│line ${i}`).join("\n");
+		const component = editToolRenderer.renderResult(
+			{
+				content: [{ type: "text", text: "Updated demo.ts" }],
+				details: { diff, op: "update" },
+			},
+			{ expanded: false, isPartial: false, renderContext: { editMode: "hashline" } },
+			uiTheme,
+			{ file_path: "demo.ts" },
+		);
+
+		const lines = component.render(160).map(line => Bun.stripANSI(line));
+		const rendered = lines.join("\n");
+		expect(lines.filter(line => line.includes("│line "))).toHaveLength(40);
+		expect(rendered).toContain("+40│line 39");
+		expect(rendered).not.toContain("+41│line 40");
+		expect(rendered).toContain("960 more lines");
+	});
+
 	it("renders completed edit gutters without inherited frame padding", async () => {
 		const uiTheme = await getUiTheme();
 		const component = editToolRenderer.renderResult(

packages/coding-agent/test/tools/render-utils.test.ts

@@ -286,6 +286,75 @@ describe("truncateDiffByHunk", () => {
 		expect(idxOld).toBeLessThan(idxNew);
 		expect(idxNew).toBeLessThan(idxTrailing);
 	});
+	it("caps one oversized change hunk at the line budget", () => {
+		const diff = makeHunk("+", 0, 1_000).join("\n");
+		const head = truncateDiffByHunk(diff, 4, 32);
+		const tail = truncateDiffByHunk(diff, 4, 32, { fromTail: true });
+
+		expect(head.text.split("\n")).toHaveLength(32);
+		expect(head.text).toStartWith("+ new 0\n");
+		expect(head.text).toEndWith("+ new 31");
+		expect(head.hiddenLines).toBe(968);
+		expect(head.hiddenHunks).toBe(0);
+
+		expect(tail.text.split("\n")).toHaveLength(32);
+		expect(tail.text).toStartWith("+ new 968\n");
+		expect(tail.text).toEndWith("+ new 999");
+		expect(tail.hiddenLines).toBe(968);
+		expect(tail.hiddenHunks).toBe(0);
+	});
+
+	it("keeps an exact-size change hunk unchanged", () => {
+		const diff = makeHunk("-", 0, 32).join("\n");
+		expect(truncateDiffByHunk(diff, 4, 32)).toEqual({
+			text: diff,
+			hiddenHunks: 0,
+			hiddenLines: 0,
+		});
+	});
+	it("drops surrounding context when changes exactly fill the line budget", () => {
+		const diff = [" leading context", ...makeHunk("+", 0, 32), " trailing context"].join("\n");
+
+		for (const result of [truncateDiffByHunk(diff, 4, 32), truncateDiffByHunk(diff, 4, 32, { fromTail: true })]) {
+			expect(result.text.split("\n")).toHaveLength(32);
+			expect(result.text).not.toContain("context");
+			expect(result.hiddenLines).toBe(2);
+			expect(result.hiddenHunks).toBe(0);
+		}
+	});
+
+	it("does not exceed the line budget when context rounding spans multiple hunks", () => {
+		const diff = [
+			" leading context",
+			...makeHunk("+", 0, 15),
+			" middle context a",
+			" middle context b",
+			...makeHunk("-", 100, 15),
+			" trailing context",
+		].join("\n");
+
+		for (const result of [truncateDiffByHunk(diff, 4, 32), truncateDiffByHunk(diff, 4, 32, { fromTail: true })]) {
+			expect(result.text.split("\n")).toHaveLength(32);
+			expect(result.hiddenLines).toBe(2);
+			expect(result.hiddenHunks).toBe(0);
+		}
+	});
+	it("does not count a removed separator as a hidden hunk", () => {
+		const diff = [...makeHunk("+", 0, 16), " hunk separator", ...makeHunk("-", 100, 16)].join("\n");
+
+		for (const result of [truncateDiffByHunk(diff, 4, 32), truncateDiffByHunk(diff, 4, 32, { fromTail: true })]) {
+			expect(result.text.split("\n")).toHaveLength(32);
+			expect(result.hiddenLines).toBe(1);
+			expect(result.hiddenHunks).toBe(0);
+		}
+	});
+	it("reports every hunk excluded by the hunk limit", () => {
+		const diff = buildDiff(6, 1);
+
+		for (const result of [truncateDiffByHunk(diff, 2, 100), truncateDiffByHunk(diff, 2, 100, { fromTail: true })]) {
+			expect(result.hiddenHunks).toBe(4);
+		}
+	});
 });
 
 describe("formatErrorMessage (F4 sanitization)", () => {