feat(cli): preserve --tui and other flags across internal relaunches

Extract all os.execvp('hermes', ...) calls into a utility so flags like
--tui, --dev, --profile, --model, --provider, et al. survive session
resume and post-setup relaunch.

- resolve_hermes_bin: prefers sys.argv[0] when callable, then PATH,
  then falls back to '${sys.executable} -m hermes_cli.main' (fixes nix
run relaunches)
- build_relaunch_argv: allowlists critical flags so they carry over
- cmd_sessions browse now calls relaunch(['--resume', <id>])
- _apply_profile_override skips redundant work when HERMES_HOME is
  already set (child inherits parent profile)
- setup.py replaces _resolve_hermes_chat_argv with relaunch_chat()
- added comprehensive tests for flag extraction and binary resolution

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

tests/hermes_cli/test_relaunch.py

@@ -0,0 +1,140 @@
+"""Tests for hermes_cli.relaunch — unified self-relaunch utility."""
+
+import sys
+
+import pytest
+
+from hermes_cli import relaunch as relaunch_mod
+
+
+class TestResolveHermesBin:
+    def test_prefers_absolute_argv0_when_executable(self, monkeypatch):
+        fake = "/nix/store/abc/bin/hermes"
+        monkeypatch.setattr(sys, "argv", [fake])
+        monkeypatch.setattr(relaunch_mod.os.path, "isfile", lambda p: p == fake)
+        monkeypatch.setattr(relaunch_mod.os, "access", lambda p, mode: p == fake)
+        assert relaunch_mod.resolve_hermes_bin() == fake
+
+    def test_resolves_relative_argv0(self, monkeypatch, tmp_path):
+        fake = tmp_path / "hermes"
+        fake.write_text("#!/bin/sh\n")
+        fake.chmod(0o755)
+        monkeypatch.setattr(sys, "argv", [str(fake.name)])
+        monkeypatch.chdir(tmp_path)
+        # Ensure we don't accidentally match a real 'hermes' on PATH
+        monkeypatch.setattr(relaunch_mod.shutil, "which", lambda _name: None)
+        assert relaunch_mod.resolve_hermes_bin() == str(fake)
+
+    def test_falls_back_to_path_which(self, monkeypatch):
+        monkeypatch.setattr(sys, "argv", ["-c"])  # not a real path
+        monkeypatch.setattr(
+            relaunch_mod.shutil, "which", lambda name: "/usr/bin/hermes" if name == "hermes" else None
+        )
+        assert relaunch_mod.resolve_hermes_bin() == "/usr/bin/hermes"
+
+    def test_returns_none_when_unresolvable(self, monkeypatch):
+        monkeypatch.setattr(sys, "argv", ["-c"])
+        monkeypatch.setattr(relaunch_mod.shutil, "which", lambda _name: None)
+        assert relaunch_mod.resolve_hermes_bin() is None
+
+
+class TestExtractCriticalFlags:
+    def test_extracts_tui_and_dev(self):
+        argv = ["--tui", "--dev", "chat"]
+        assert relaunch_mod._extract_critical_flags(argv) == ["--tui", "--dev"]
+
+    def test_extracts_profile_with_value(self):
+        argv = ["--profile", "work", "chat"]
+        assert relaunch_mod._extract_critical_flags(argv) == ["--profile", "work"]
+
+    def test_extracts_short_p_with_value(self):
+        argv = ["-p", "work"]
+        assert relaunch_mod._extract_critical_flags(argv) == ["-p", "work"]
+
+    def test_extracts_equals_form(self):
+        argv = ["--profile=work", "--model=anthropic/claude-sonnet-4"]
+        assert relaunch_mod._extract_critical_flags(argv) == [
+            "--profile=work",
+            "--model=anthropic/claude-sonnet-4",
+        ]
+
+    def test_skips_unknown_flags(self):
+        argv = ["--foo", "bar", "--tui"]
+        assert relaunch_mod._extract_critical_flags(argv) == ["--tui"]
+
+    def test_does_not_consume_flag_like_value(self):
+        argv = ["--tui", "--resume", "abc123"]
+        assert relaunch_mod._extract_critical_flags(argv) == ["--tui"]
+
+    def test_preserves_multiple_skills(self):
+        argv = ["-s", "foo", "-s", "bar", "--tui"]
+        assert relaunch_mod._extract_critical_flags(argv) == ["-s", "foo", "-s", "bar", "--tui"]
+
+
+class TestBuildRelaunchArgv:
+    def test_uses_bin_when_available(self, monkeypatch):
+        monkeypatch.setattr(relaunch_mod, "resolve_hermes_bin", lambda: "/usr/bin/hermes")
+        argv = relaunch_mod.build_relaunch_argv(["--resume", "abc"])
+        assert argv[0] == "/usr/bin/hermes"
+
+    def test_falls_back_to_python_module(self, monkeypatch):
+        monkeypatch.setattr(relaunch_mod, "resolve_hermes_bin", lambda: None)
+        argv = relaunch_mod.build_relaunch_argv(["--resume", "abc"])
+        assert argv == [sys.executable, "-m", "hermes_cli.main", "--resume", "abc"]
+
+    def test_preserves_critical_flags(self, monkeypatch):
+        monkeypatch.setattr(relaunch_mod, "resolve_hermes_bin", lambda: "/usr/bin/hermes")
+        original = ["--tui", "--dev", "--profile", "work", "sessions", "browse"]
+        argv = relaunch_mod.build_relaunch_argv(["--resume", "abc"], original_argv=original)
+        assert "--tui" in argv
+        assert "--dev" in argv
+        assert "--profile" in argv
+        assert "work" in argv
+        assert "--resume" in argv
+        assert "abc" in argv
+        # The original subcommand should not survive
+        assert "sessions" not in argv
+        assert "browse" not in argv
+
+    def test_can_disable_preserve(self, monkeypatch):
+        monkeypatch.setattr(relaunch_mod, "resolve_hermes_bin", lambda: "/usr/bin/hermes")
+        original = ["--tui", "chat"]
+        argv = relaunch_mod.build_relaunch_argv(
+            ["--resume", "abc"], preserve_critical=False, original_argv=original
+        )
+        assert "--tui" not in argv
+        assert argv == ["/usr/bin/hermes", "--resume", "abc"]
+
+
+class TestRelaunch:
+    def test_calls_execvp(self, monkeypatch):
+        calls = []
+
+        def fake_execvp(path, argv):
+            calls.append((path, argv))
+            raise SystemExit(0)
+
+        monkeypatch.setattr(relaunch_mod.os, "execvp", fake_execvp)
+        monkeypatch.setattr(relaunch_mod, "resolve_hermes_bin", lambda: "/usr/bin/hermes")
+
+        with pytest.raises(SystemExit):
+            relaunch_mod.relaunch(["--resume", "abc"])
+
+        assert calls == [("/usr/bin/hermes", ["/usr/bin/hermes", "--resume", "abc"])]
+
+
+class TestRelaunchChat:
+    def test_appends_chat(self, monkeypatch):
+        calls = []
+
+        def fake_execvp(path, argv):
+            calls.append((path, argv))
+            raise SystemExit(0)
+
+        monkeypatch.setattr(relaunch_mod.os, "execvp", fake_execvp)
+        monkeypatch.setattr(relaunch_mod, "resolve_hermes_bin", lambda: "/usr/bin/hermes")
+
+        with pytest.raises(SystemExit):
+            relaunch_mod.relaunch_chat()
+
+        assert calls == [("/usr/bin/hermes", ["/usr/bin/hermes", "chat"])]