diff --git a/test/dev-206-windows-gbrain.test.ts b/test/dev-206-windows-gbrain.test.ts
index f44d0deab..37a093f5c 100644
--- a/test/dev-206-windows-gbrain.test.ts
+++ b/test/dev-206-windows-gbrain.test.ts
@@ -1,7 +1,7 @@
 import { describe, expect, test } from "bun:test";
 import { chmodSync, existsSync, mkdirSync, mkdtempSync, readFileSync, rmSync, writeFileSync } from "fs";
 import { tmpdir } from "os";
-import { dirname, join, resolve } from "path";
+import { delimiter, dirname, join, resolve } from "path";
 import { spawnSync } from "child_process";
 
 import codex from "../hosts/codex";
@@ -106,6 +106,18 @@ describe("DEV-206 Windows Codex runtime and GBrain regressions", () => {
     expect(plan.shell).toBe(false);
   });
 
+  test("Windows source registration rejects shell-only launchers", () => {
+    for (const extension of ["cmd", "bat", "ps1"]) {
+      expect(() =>
+        planGbrainSpawn(
+          ["sources", "list", "--json"],
+          `C:\\Program Files\\GBrain\\gbrain.${extension}`,
+          "win32",
+        ),
+      ).toThrow("unsafe Windows gbrain launcher");
+    }
+  });
+
   test("dream capability planning refuses a brain-wide fallback", () => {
     const supported = planSourceScopedDream(
       "gstack-code-test",
@@ -125,4 +137,85 @@ describe("DEV-206 Windows Codex runtime and GBrain regressions", () => {
       expect(brainWideOnly.error).toContain("refusing to widen scope");
     }
   });
+
+  test("dream execution probes capability and never launches a brain-wide fallback", () => {
+    const tmp = mkdtempSync(join(tmpdir(), "gstack-dev-206-dream-"));
+    try {
+      const binDir = join(tmp, "bin");
+      const gbrainHome = join(tmp, ".gbrain");
+      const gstackHome = join(tmp, ".gstack");
+      const logPath = join(tmp, "gbrain-calls.jsonl");
+      mkdirSync(binDir, { recursive: true });
+      mkdirSync(gbrainHome, { recursive: true });
+      mkdirSync(gstackHome, { recursive: true });
+      writeFileSync(
+        join(gbrainHome, "config.json"),
+        JSON.stringify({ engine: "pglite", database_url: "pglite:///synthetic" }),
+      );
+
+      const fakeSource = join(tmp, "fake-gbrain.ts");
+      const fakeBinary = join(binDir, process.platform === "win32" ? "gbrain.exe" : "gbrain");
+      writeFileSync(
+        fakeSource,
+        `import { appendFileSync } from "fs";
+const args = process.argv.slice(2);
+appendFileSync(process.env.FAKE_GBRAIN_LOG!, JSON.stringify(args) + "\\n");
+if (args.join(" ") === "--version") { console.log("gbrain 0.41.0"); process.exit(0); }
+if (args.join(" ") === "sources list --json") { console.log('{"sources":[]}'); process.exit(0); }
+if (args.join(" ") === "dream --help") { console.log("Usage: gbrain dream"); process.exit(0); }
+process.exit(91);
+`,
+      );
+      const built = spawnSync(
+        process.execPath,
+        ["build", fakeSource, "--compile", "--outfile", fakeBinary],
+        { encoding: "utf-8", timeout: 30_000 },
+      );
+      expect(built.status).toBe(0);
+      chmodSync(fakeBinary, 0o755);
+
+      const childEnv: NodeJS.ProcessEnv = { ...process.env };
+      for (const key of Object.keys(childEnv)) {
+        if (key.toUpperCase() === "PATH") delete childEnv[key];
+      }
+      Object.assign(childEnv, {
+        HOME: tmp,
+        GBRAIN_HOME: gbrainHome,
+        GSTACK_HOME: gstackHome,
+        PATH: `${binDir}${delimiter}${process.env.PATH || ""}`,
+        FAKE_GBRAIN_LOG: logPath,
+      });
+
+      const result = spawnSync(
+        process.execPath,
+        [
+          join(ROOT, "bin", "gstack-gbrain-sync.ts"),
+          "--dream",
+          "--no-code",
+          "--no-memory",
+          "--no-brain-sync",
+        ],
+        {
+          cwd: ROOT,
+          encoding: "utf-8",
+          timeout: 15_000,
+          env: childEnv,
+        },
+      );
+      const output = `${result.stdout || ""}${result.stderr || ""}`;
+      expect(result.status).toBe(1);
+      expect(output).toContain("does not support --source");
+      expect(output).toContain("refusing to widen scope");
+
+      const calls = readFileSync(logPath, "utf-8")
+        .trim()
+        .split("\n")
+        .map((line) => JSON.parse(line) as string[]);
+      expect(calls).toContainEqual(["dream", "--help"]);
+      expect(calls).not.toContainEqual(["dream"]);
+      expect(calls.some((call) => call[0] === "dream" && call[1] !== "--help")).toBe(false);
+    } finally {
+      rmSync(tmp, { recursive: true, force: true });
+    }
+  });
 });