fix: remove misleading write byte counts

The write tools reported UTF-16 code units as bytes. Remove the count from success messages instead of scanning content again.

Closes #8979

packages/agent/CHANGELOG.md

@@ -2,6 +2,10 @@
 
 ## [Unreleased]
 
+### Fixed
+
+- Fixed the write tool reporting UTF-16 code-unit counts as byte counts by removing the misleading count ([#8979](https://github.com/earendil-works/pi/issues/8979)).
+
 ## [0.84.4] - 2026-08-28
 
 ### Breaking Changes

packages/agent/src/harness/tools/write.ts

@@ -30,7 +30,7 @@ export function createWriteTool<TContext extends ExecutionToolContext = Executio
 				getOrThrow(await env.writeFile(absolutePath, content, signal));
 				if (signal?.aborted) throw new Error("Operation aborted");
 				return {
-					content: [{ type: "text", text: `Successfully wrote ${content.length} bytes to ${path}` }],
+					content: [{ type: "text", text: `Successfully wrote to ${path}` }],
 					details: undefined,
 				};
 			});

packages/agent/test/harness/tools.test.ts

@@ -263,7 +263,7 @@ describe("AgentHarness tools", () => {
 				context,
 			);
 
-			expect(textOutput(result)).toBe("Successfully wrote 5 bytes to nested/dir/file.txt");
+			expect(textOutput(result)).toBe("Successfully wrote to nested/dir/file.txt");
 			expect(getOrThrow(await context.env.readTextFile("nested/dir/file.txt"))).toBe("hello");
 		});
 

packages/coding-agent/CHANGELOG.md

@@ -4,6 +4,7 @@
 
 ### Fixed
 
+- Fixed the write tool reporting UTF-16 code-unit counts as byte counts by removing the misleading count ([#8979](https://github.com/earendil-works/pi/issues/8979)).
 - Fixed proxied plain-HTTP provider requests hanging after a tool call by tunneling them with CONNECT ([#8134](https://github.com/earendil-works/pi/issues/8134)).
 
 ## [0.84.4] - 2026-08-28

packages/coding-agent/src/core/tools/write.ts

@@ -226,7 +226,7 @@ export function createWriteToolDefinition(
 				throwIfAborted();
 
 				return {
-					content: [{ type: "text", text: `Successfully wrote ${content.length} bytes to ${path}` }],
+					content: [{ type: "text", text: `Successfully wrote to ${path}` }],
 					details: undefined,
 				};
 			});

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

@@ -256,8 +256,7 @@ describe("Coding Agent Tools", () => {
 
 			const result = await writeTool.execute("test-call-3", { path: testFile, content });
 
-			expect(getTextOutput(result)).toContain("Successfully wrote");
-			expect(getTextOutput(result)).toContain(testFile);
+			expect(getTextOutput(result)).toBe(`Successfully wrote to ${testFile}`);
 			expect(result.details).toBeUndefined();
 		});