fix cli shorthand trailing backslash param parsing

Author: highruned

ANALYSIS.md

@@ -182,3 +182,10 @@
   - Updated shorthand argv reconstruction in `index.ts` to include `--params` only when parsed params are present.
   - Added regression coverage in `test/parsing.test.ts` (`shorthand parser with empty parens omits params flag`).
 - Practical impact: no-arg shorthand exec now serializes cleanly as `params: []` in live CLI↔cerebro-link websocket calls.
+
+## 2026-02-21 slot-11 follow-up (13:3x PT)
+- Rationale: shorthand parameter parsing dropped a terminal escape marker when params ended with a backslash (for example `Gon.ask(hello\\)`), which can corrupt path-like inputs and silently alter user intent.
+- Change scope:
+  - Updated `parseParamsString(...)` in `index.ts` to retain a trailing literal backslash when an escape sequence is unfinished at end-of-input.
+  - Added regression coverage in `test/parsing.test.ts` (`shorthand parser preserves trailing backslash in params`).
+- Practical impact: shorthand `cerebro.exec` calls now preserve terminal backslashes in parameter payloads instead of truncating them.

index.ts

@@ -393,6 +393,11 @@ export function createCli<R extends AnyRouter>({
       }
     }
 
+    if (escape) {
+      currentParam += '\\';
+      sawParamToken = true;
+    }
+
     if (sawParamToken || currentParam.trim().length > 0 || paramsString.trimEnd().endsWith(',')) {
       pushCurrentParam();
     }

test/parsing.test.ts

@@ -637,6 +637,26 @@ test("shorthand parser accepts hyphenated agent and method names", async () => {
   );
 });
 
+test("shorthand parser preserves trailing backslash in params", async () => {
+  const router = t.router({
+    "cerebro.exec": t.procedure
+      .input(
+        z.object({
+          agent: z.string(),
+          method: z.string(),
+          params: z.array(z.string()),
+        })
+      )
+      .query(({ input }) => JSON.stringify(input)),
+  });
+
+  const result = await run(router, ["cerebro.exec", "Gon.ask(hello\\\\)"]);
+
+  expect(result).toMatchInlineSnapshot(
+    `"{\"agent\":\"Gon\",\"method\":\"ask\",\"params\":[\"hello\\\\\"]}"`
+  );
+});
+
 test("boolean array input", async () => {
   const router = t.router({
     test: t.procedure