fix(agent): isolate conversation workspaces

tests/runtime/opencode.test.ts

@@ -1,5 +1,8 @@
 import { describe, expect, it } from "bun:test";
 import { type OpencodeClient } from "@opencode-ai/sdk/v2";
+import { mkdtemp, readdir, rm, stat } from "node:fs/promises";
+import { tmpdir } from "node:os";
+import { join, relative } from "node:path";
 
 import { config } from "../../src/config.js";
 import { OpencodeRuntimeAdapter } from "../../src/runtime/opencode.js";
@@ -87,6 +90,79 @@ describe("OpencodeRuntimeAdapter.ensureClient", () => {
   });
 });
 
+describe("OpencodeRuntimeAdapter.createSession", () => {
+  it("creates a real chat session inside a dedicated conversation workspace", async () => {
+    const workspaceRoot = await mkdtemp(join(tmpdir(), "tjwater-conversations-"));
+    const calls: Array<Record<string, unknown>> = [];
+    const client = {
+      session: {
+        create: async (input: Record<string, unknown>) => {
+          calls.push(input);
+          return {
+            data: {
+              id: "runtime-session-1",
+              directory: input.directory,
+            },
+          };
+        },
+      },
+    } as unknown as OpencodeClient;
+    const runtime = Object.assign(Object.create(OpencodeRuntimeAdapter.prototype), {
+      clientPromise: null,
+      closeServer: null,
+      ensureClient: async () => client,
+    }) as OpencodeRuntimeAdapter;
+
+    try {
+      const session = await runtime.createSession("chat", {
+        conversationWorkspace: true,
+        workspaceRoot,
+      });
+      const directory = String(calls[0]?.directory);
+
+      expect(relative(workspaceRoot, directory).startsWith("..")).toBe(false);
+      const workspaceStat = await stat(directory);
+      expect(workspaceStat.isDirectory()).toBe(true);
+      expect(workspaceStat.mode & 0o777).toBe(0o700);
+      expect(session.directory).toBe(directory);
+      expect(calls[0]?.permission).toEqual([
+        { permission: "read", pattern: `${directory}/**`, action: "allow" },
+        { permission: "edit", pattern: `${directory}/**`, action: "ask" },
+      ]);
+    } finally {
+      await rm(workspaceRoot, { force: true, recursive: true });
+    }
+  });
+
+  it("removes an empty conversation workspace when session creation fails", async () => {
+    const workspaceRoot = await mkdtemp(join(tmpdir(), "tjwater-conversations-"));
+    const client = {
+      session: {
+        create: async () => {
+          throw new Error("session creation failed");
+        },
+      },
+    } as unknown as OpencodeClient;
+    const runtime = Object.assign(Object.create(OpencodeRuntimeAdapter.prototype), {
+      clientPromise: null,
+      closeServer: null,
+      ensureClient: async () => client,
+    }) as OpencodeRuntimeAdapter;
+
+    try {
+      await expect(
+        runtime.createSession("chat", {
+          conversationWorkspace: true,
+          workspaceRoot,
+        }),
+      ).rejects.toThrow("session creation failed");
+      expect(await readdir(workspaceRoot)).toEqual([]);
+    } finally {
+      await rm(workspaceRoot, { force: true, recursive: true });
+    }
+  });
+});
+
 describe("OpencodeRuntimeAdapter.warmup", () => {
   it("initializes the project session and model tools before reporting ready", async () => {
     const calls: string[] = [];