[codex] Allow neo TUI sentinel flag forwarding

packages/coding-agent/CHANGELOG.md

@@ -10,6 +10,8 @@
 
 ### Fixed
 
+- Fixed `senpi --neo -- ...` so Rust TUI flags after the sentinel reach the native binary instead of being rejected by the Node CLI parser.
+
 ### Removed
 
 ## [2026.5.24] - 2026-05-24

packages/coding-agent/src/cli/args.ts

@@ -170,6 +170,11 @@ export function parseArgs(args: string[]): Args {
 			result.offline = true;
 		} else if (arg === "--neo") {
 			result.neo = true;
+		} else if (arg === "--") {
+			if (!result.neo) {
+				result.messages.push(...args.slice(i + 1));
+			}
+			break;
 		} else if (arg.startsWith("@")) {
 			result.fileArgs.push(arg.slice(1)); // Remove @ prefix
 		} else if (arg.startsWith("--")) {

packages/coding-agent/test/suite/regressions/neo-tui-arg-forwarding.test.ts

@@ -3,10 +3,9 @@
  * caller to the Rust `senpi-neo-tui` binary via the `--` sentinel.
  *
  * Without the sentinel split, the senpi argparser eats `--theme`,
- * `--demo`, etc. and either errors out (they mean something completely
- * different on the senpi side, e.g. `--theme <path>` loads a theme file)
- * or silently swallows them, so the neo TUI never sees its own flags
- * and `senpi --neo --theme dracula` becomes a lie in the docs.
+ * `--demo`, etc. and either errors out (for unknown Rust-only flags)
+ * or treats them as senpi-side options, so the neo TUI never sees its own
+ * flags and `senpi --neo -- --theme dracula` becomes a lie in the docs.
  *
  * Source of truth: {@link splitNeoArgs} in
  * `packages/coding-agent/src/modes/neo-mode.ts`.

packages/coding-agent/test/suite/regressions/neo-tui-arg-parse.test.ts

@@ -2,9 +2,9 @@
  * Regression: `--neo` flag must round-trip through `parseArgs` cleanly and
  * coexist with the rest of the senpi CLI surface.
  *
- * The flag dispatch into the Rust binary lives in a later wave; this test
- * only locks the arg-parser contract so future renames or accidental
- * removals fail loudly.
+ * The sentinel split into backend args vs Rust TUI args lives in neo-mode;
+ * this file locks the parser contract so forwarded neo flags do not get
+ * rejected before that split can run.
  */
 
 import { describe, expect, test } from "vitest";
@@ -44,4 +44,12 @@ describe("--neo flag", () => {
 		const parsed = parseArgs(["--neo"]);
 		expect(parsed.unknownFlags.has("neo")).toBe(false);
 	});
+
+	test("--neo allows a -- sentinel for Rust TUI flags", () => {
+		const parsed = parseArgs(["--neo", "--", "--list-themes", "--theme", "dracula"]);
+		expect(parsed.neo).toBe(true);
+		expect(parsed.diagnostics).toEqual([]);
+		expect(parsed.unknownFlags.size).toBe(0);
+		expect(parsed.messages).toEqual([]);
+	});
 });