feat(tools): add run_shell, edit_file, write_file + read_file directory listing

Four standard-tier tool extensions (one tool per extension, zero ABI change):
- tool-read-file: read_file now lists directory contents (sorted, /-suffixed subdirs)
- tool-shell: run_shell (foreground, streamed, cancellable, cwd, timeout + output cap)
- tool-edit-file: edit_file (oldString/newString/replaceAll; errors on absent/non-unique)
- tool-write-file: write_file (explicit overwrite flag)
Registered in host-bin CORE_EXTENSIONS. Live boot clean (shell capability accepted).
686 vitest + 89 bun = 775 tests; tsc -b EXIT 0; biome clean.

1 files changed, 291 insertions, 0 deletions

diff --git a/packages/tool-write-file/src/write-file.test.ts b/packages/tool-write-file/src/write-file.test.ts
new file mode 100644
index 0000000..cf4fa64
--- /dev/null
+++ b/packages/tool-write-file/src/write-file.test.ts
@@ -0,0 +1,291 @@
+import { mkdir, mkdtemp, readFile, rm, writeFile } from "node:fs/promises";
+import { tmpdir } from "node:os";
+import { join } from "node:path";
+import { createLogger, type ToolExecuteContext } from "@dispatch/kernel";
+import { afterEach, beforeEach, describe, expect, it } from "vitest";
+import {
+	createWriteFileTool,
+	decideOverwrite,
+	isPathWithinWorkdir,
+	validateArgs,
+} from "./write-file.js";
+
+function stubCtx(overrides?: Partial<ToolExecuteContext>): ToolExecuteContext {
+	return {
+		toolCallId: "test-call-1",
+		onOutput: () => {},
+		signal: AbortSignal.timeout(5000),
+		log: createLogger(
+			{ extensionId: "test" },
+			{ emit: () => {} },
+			{ now: () => 0, newId: () => "id" },
+		),
+		...overrides,
+	};
+}
+
+let workdir: string;
+
+beforeEach(async () => {
+	workdir = await mkdtemp(join(tmpdir(), "tool-write-file-test-"));
+});
+
+afterEach(async () => {
+	await rm(workdir, { recursive: true, force: true });
+});
+
+describe("decideOverwrite", () => {
+	it("returns create when file absent and overwrite is false", () => {
+		expect(decideOverwrite(false, false)).toBe("create");
+	});
+
+	it("returns create when file absent and overwrite is false (default)", () => {
+		expect(decideOverwrite(false, false)).toBe("create");
+	});
+
+	it("returns error when file exists and overwrite is false", () => {
+		const result = decideOverwrite(true, false);
+		expect(typeof result).toBe("object");
+		if (typeof result === "object") {
+			expect(result.error).toContain("already exists");
+		}
+	});
+
+	it("returns overwrite when file exists and overwrite is true", () => {
+		expect(decideOverwrite(true, true)).toBe("overwrite");
+	});
+
+	it("returns error when file absent and overwrite is true", () => {
+		const result = decideOverwrite(false, true);
+		expect(typeof result).toBe("object");
+		if (typeof result === "object") {
+			expect(result.error).toContain("does not exist");
+		}
+	});
+
+	it("covers all four rows of the truth table", () => {
+		expect(decideOverwrite(false, false)).toBe("create");
+		expect(decideOverwrite(true, false)).toEqual(
+			expect.objectContaining({ error: expect.any(String) }),
+		);
+		expect(decideOverwrite(true, true)).toBe("overwrite");
+		expect(decideOverwrite(false, true)).toEqual(
+			expect.objectContaining({ error: expect.any(String) }),
+		);
+	});
+});
+
+describe("isPathWithinWorkdir", () => {
+	it("accepts a path within workdir", () => {
+		expect(isPathWithinWorkdir("/tmp/workdir/file.txt", "/tmp/workdir")).toBe(true);
+	});
+
+	it("accepts the workdir itself", () => {
+		expect(isPathWithinWorkdir("/tmp/workdir", "/tmp/workdir")).toBe(true);
+	});
+
+	it("rejects a path outside workdir", () => {
+		expect(isPathWithinWorkdir("/tmp/other/file.txt", "/tmp/workdir")).toBe(false);
+	});
+
+	it("rejects a prefix attack (workdir prefix but different dir)", () => {
+		expect(isPathWithinWorkdir("/tmp/workdir-evil/file.txt", "/tmp/workdir")).toBe(false);
+	});
+});
+
+describe("validateArgs", () => {
+	it("returns validated args for valid input", () => {
+		const result = validateArgs({ path: "foo.txt", content: "hello" });
+		expect(result).toEqual({ path: "foo.txt", content: "hello", overwrite: false });
+	});
+
+	it("parses overwrite as true", () => {
+		const result = validateArgs({ path: "foo.txt", content: "x", overwrite: true });
+		expect(result).toEqual({ path: "foo.txt", content: "x", overwrite: true });
+	});
+
+	it("defaults overwrite to false", () => {
+		const result = validateArgs({ path: "foo.txt", content: "x" });
+		expect(result).toEqual({ path: "foo.txt", content: "x", overwrite: false });
+	});
+
+	it("accepts empty string content", () => {
+		const result = validateArgs({ path: "foo.txt", content: "" });
+		expect(result).toEqual({ path: "foo.txt", content: "", overwrite: false });
+	});
+
+	it("returns error for null args", () => {
+		expect(validateArgs(null)).toHaveProperty("error");
+	});
+
+	it("returns error for missing path", () => {
+		expect(validateArgs({ content: "x" })).toHaveProperty("error");
+	});
+
+	it("returns error for missing content", () => {
+		expect(validateArgs({ path: "foo.txt" })).toHaveProperty("error");
+	});
+
+	it("returns error for non-string content", () => {
+		expect(validateArgs({ path: "foo.txt", content: 123 })).toHaveProperty("error");
+	});
+
+	it("returns error for non-boolean overwrite", () => {
+		expect(validateArgs({ path: "foo.txt", content: "x", overwrite: "yes" })).toHaveProperty(
+			"error",
+		);
+	});
+});
+
+describe("createWriteFileTool", () => {
+	it("creates a new file when overwrite is unset and the file is absent", async () => {
+		const tool = createWriteFileTool(workdir);
+		const result = await tool.execute({ path: "new-file.txt", content: "hello world" }, stubCtx());
+
+		expect(result.isError).toBeUndefined();
+		expect(result.content).toContain("Created");
+		const written = await readFile(join(workdir, "new-file.txt"), "utf8");
+		expect(written).toBe("hello world");
+	});
+
+	it("errors when the file exists and overwrite is unset", async () => {
+		await writeFile(join(workdir, "existing.txt"), "old content", "utf8");
+
+		const tool = createWriteFileTool(workdir);
+		const result = await tool.execute({ path: "existing.txt", content: "new content" }, stubCtx());
+
+		expect(result.isError).toBe(true);
+		expect(result.content).toContain("already exists");
+		expect(result.content).toContain("overwrite");
+		const unchanged = await readFile(join(workdir, "existing.txt"), "utf8");
+		expect(unchanged).toBe("old content");
+	});
+
+	it("overwrites an existing file when overwrite is true", async () => {
+		await writeFile(join(workdir, "existing.txt"), "old content", "utf8");
+
+		const tool = createWriteFileTool(workdir);
+		const result = await tool.execute(
+			{ path: "existing.txt", content: "new content", overwrite: true },
+			stubCtx(),
+		);
+
+		expect(result.isError).toBeUndefined();
+		expect(result.content).toContain("Overwrote");
+		const written = await readFile(join(workdir, "existing.txt"), "utf8");
+		expect(written).toBe("new content");
+	});
+
+	it("errors when overwrite is true but the file is absent", async () => {
+		const tool = createWriteFileTool(workdir);
+		const result = await tool.execute(
+			{ path: "nonexistent.txt", content: "data", overwrite: true },
+			stubCtx(),
+		);
+
+		expect(result.isError).toBe(true);
+		expect(result.content).toContain("does not exist");
+	});
+
+	it("errors when the parent directory does not exist", async () => {
+		const tool = createWriteFileTool(workdir);
+		const result = await tool.execute({ path: "no/such/dir/file.txt", content: "data" }, stubCtx());
+
+		expect(result.isError).toBe(true);
+		expect(result.content).toContain("Parent directory");
+	});
+
+	it("rejects a path outside the working directory", async () => {
+		const tool = createWriteFileTool(workdir);
+		const result = await tool.execute({ path: "../escape.txt", content: "data" }, stubCtx());
+
+		expect(result.isError).toBe(true);
+		expect(result.content).toContain("outside the working directory");
+	});
+
+	it("rejects an absolute path outside workdir", async () => {
+		const tool = createWriteFileTool(workdir);
+		const result = await tool.execute({ path: "/tmp/escape.txt", content: "data" }, stubCtx());
+
+		expect(result.isError).toBe(true);
+		expect(result.content).toContain("outside the working directory");
+	});
+
+	it("concurrencySafe is false", () => {
+		const tool = createWriteFileTool(workdir);
+		expect(tool.concurrencySafe).toBe(false);
+	});
+
+	it("has correct name and parameters shape", () => {
+		const tool = createWriteFileTool(workdir);
+		expect(tool.name).toBe("write_file");
+		expect(tool.parameters.type).toBe("object");
+		expect(tool.parameters.required).toEqual(["path", "content"]);
+		expect(tool.parameters.properties?.path?.type).toBe("string");
+		expect(tool.parameters.properties?.content?.type).toBe("string");
+		expect(tool.parameters.properties?.overwrite?.type).toBe("boolean");
+	});
+
+	it("never throws on bad input (always returns ToolResult)", async () => {
+		const tool = createWriteFileTool(workdir);
+		const inputs = [null, undefined, 42, "string", {}, { path: "" }, { path: 123 }];
+		for (const input of inputs) {
+			const result = await tool.execute(input, stubCtx());
+			expect(result).toHaveProperty("content");
+			expect(typeof result.content).toBe("string");
+		}
+	});
+
+	it("respects ctx.cwd over baked workdir", async () => {
+		const ctxDir = await mkdtemp(join(tmpdir(), "ctx-cwd-test-"));
+		try {
+			const tool = createWriteFileTool(workdir);
+			const result = await tool.execute(
+				{ path: "ctx-file.txt", content: "from ctx" },
+				stubCtx({ cwd: ctxDir }),
+			);
+
+			expect(result.isError).toBeUndefined();
+			const written = await readFile(join(ctxDir, "ctx-file.txt"), "utf8");
+			expect(written).toBe("from ctx");
+		} finally {
+			await rm(ctxDir, { recursive: true, force: true });
+		}
+	});
+
+	it("handles symlink escape attempt", async () => {
+		const outsideDir = await mkdtemp(join(tmpdir(), "outside-"));
+		try {
+			const symlinkPath = join(workdir, "link.txt");
+			const { symlink } = await import("node:fs/promises");
+			await symlink(join(outsideDir, "target.txt"), symlinkPath);
+
+			const tool = createWriteFileTool(workdir);
+			const result = await tool.execute({ path: "link.txt", content: "escape" }, stubCtx());
+
+			expect(result.isError).toBe(true);
+			expect(result.content).toContain("outside the working directory");
+		} finally {
+			await rm(outsideDir, { recursive: true, force: true });
+		}
+	});
+
+	it("writes empty content", async () => {
+		const tool = createWriteFileTool(workdir);
+		const result = await tool.execute({ path: "empty.txt", content: "" }, stubCtx());
+
+		expect(result.isError).toBeUndefined();
+		const written = await readFile(join(workdir, "empty.txt"), "utf8");
+		expect(written).toBe("");
+	});
+
+	it("writes content in subdirectory that exists", async () => {
+		await mkdir(join(workdir, "sub"));
+		const tool = createWriteFileTool(workdir);
+		const result = await tool.execute({ path: "sub/file.txt", content: "nested" }, stubCtx());
+
+		expect(result.isError).toBeUndefined();
+		const written = await readFile(join(workdir, "sub", "file.txt"), "utf8");
+		expect(written).toBe("nested");
+	});
+});