feat(auth): add TWITTER_BROWSER env var to specify browser preference

Add TWITTER_BROWSER environment variable to allow users to control
which browser's cookies are prioritized during extraction.

Example: TWITTER_BROWSER=chrome twitter feed

Supported values: arc, chrome, edge, firefox, brave.
The specified browser is moved to the front of the extraction order.

Also adds AGENTS.md developer guide for AI coding assistants.

Co-authored-by: Agassi <413855+agassiyzh@users.noreply.github.com>

AGENTS.md

@@ -0,0 +1,70 @@
+# AGENTS.md — Agent Developer Guide for twitter-cli
+
+This file provides context for AI agents working in this repository.
+
+## Project Overview
+
+- **Project**: twitter-cli — A CLI for Twitter/X (read timelines, bookmarks, search, post, reply, etc.)
+- **Language**: Python 3.10+
+- **Package Manager**: uv (recommended) / pip
+- **Repository**: https://github.com/jackwener/twitter-cli
+
+## Build, Lint, and Test Commands
+
+```bash
+# Install all dependencies (including dev)
+uv sync --extra dev
+
+# Run ruff linter
+uv run ruff check .
+
+# Run mypy type checker
+uv run mypy twitter_cli
+
+# Run all tests (excludes smoke tests by default)
+uv run pytest -q
+
+# Run a single test
+uv run pytest tests/test_cli.py::test_feed_command -v
+
+# Run tests matching pattern
+uv run pytest -k "test_parse" -v
+```
+
+## Code Style
+
+- **Line length**: 100 characters
+- **Python version**: 3.10+
+- Use `from __future__ import annotations` at top of all .py files
+- **Functions/variables**: `snake_case`, **Classes**: `PascalCase`, **Constants**: `UPPER_SNAKE_CASE`
+- Private functions: prefix with `_`
+- Use `@dataclass` for data models (in `models.py`)
+- Use Click framework for CLI commands
+- Custom exceptions in `exceptions.py`, base: `TwitterError(RuntimeError)`
+
+## Project Structure
+
+```
+twitter_cli/
+├── cli.py               # Click CLI entry point
+├── client.py            # Twitter API client (HTTP)
+├── auth.py              # Cookie extraction & auth
+├── graphql.py           # GraphQL query IDs
+├── parser.py            # Tweet/User parsing
+├── models.py            # Dataclass models
+├── formatter.py         # Rich table formatting
+├── serialization.py     # YAML/JSON output
+├── output.py            # Structured output helpers
+├── config.py            # Config loading
+├── filter.py            # Tweet ranking/scoring
+├── constants.py         # Constants
+├── exceptions.py        # Custom exceptions
+├── cache.py             # Tweet caching
+├── search.py            # Search utilities
+└── timeutil.py          # Time utilities
+```
+
+## CI
+
+- GitHub Actions: Python 3.10, 3.11, 3.12
+- CI validates: ruff check + mypy + pytest

SKILL.md

@@ -49,6 +49,7 @@ If `AUTH_NEEDED`, proceed to guide the user:
 
 Ensure user is logged into x.com in one of: Arc, Chrome, Edge, Firefox, Brave. twitter-cli auto-extracts cookies.
 All Chrome profiles are scanned automatically. To specify a profile: `TWITTER_CHROME_PROFILE="Profile 2" twitter feed`.
+To prioritize a specific browser: `TWITTER_BROWSER=chrome twitter feed` (supported: arc, chrome, edge, firefox, brave).
 
 ```bash
 twitter whoami

tests/test_auth.py

@@ -135,7 +135,7 @@ def test_extract_via_subprocess_script_includes_arc(monkeypatch) -> None:
     cookies, diagnostics = auth._extract_via_subprocess()
 
     assert cookies is None
-    assert '("arc", browser_cookie3.arc)' in seen["script"]
+    assert '"arc": browser_cookie3.arc' in seen["script"]
 
 
 def test_extract_via_subprocess_retries_uv_when_current_env_has_no_output(monkeypatch) -> None:

twitter_cli/auth.py

@@ -193,6 +193,20 @@ _CHROMIUM_BASE_DIRS: Dict[str, str] = {
     "brave": os.path.join("BraveSoftware", "Brave-Browser"),
 }
 
+# Default browser order for cookie extraction
+_DEFAULT_BROWSER_ORDER = ["arc", "chrome", "edge", "firefox", "brave"]
+
+
+def _get_browser_order() -> List[str]:
+    """Return browser extraction order, respecting TWITTER_BROWSER env var."""
+    env = os.environ.get("TWITTER_BROWSER", "").strip().lower()
+    if not env:
+        return _DEFAULT_BROWSER_ORDER
+    if env not in {"arc", "chrome", "edge", "firefox", "brave"}:
+        logger.warning("TWITTER_BROWSER='%s' is invalid, using default order", env)
+        return _DEFAULT_BROWSER_ORDER
+    return [env] + [b for b in _DEFAULT_BROWSER_ORDER if b != env]
+
 
 def _iter_chrome_cookie_files(browser_name: str) -> List[str]:
     """Return cookie file paths for all Chrome profiles.
@@ -262,17 +276,18 @@ def _extract_in_process() -> Tuple[Optional[Dict[str, str]], List[str]]:
         logger.debug("browser_cookie3 not installed, skipping in-process extraction")
         return None, ["browser-cookie3 not installed"]
 
-    browsers = [
-        ("arc", browser_cookie3.arc),
-        ("chrome", browser_cookie3.chrome),
-        ("edge", browser_cookie3.edge),
-        ("firefox", browser_cookie3.firefox),
-        ("brave", browser_cookie3.brave),
-    ]
+    browser_fns = {
+        "arc": browser_cookie3.arc,
+        "chrome": browser_cookie3.chrome,
+        "edge": browser_cookie3.edge,
+        "firefox": browser_cookie3.firefox,
+        "brave": browser_cookie3.brave,
+    }
     attempts: List[str] = []
     diagnostics: List[str] = []
 
-    for name, fn in browsers:
+    for name in _get_browser_order():
+        fn = browser_fns[name]
         if name in _CHROMIUM_BASE_DIRS:
             # Chromium-based: iterate all profiles
             cookie_files = _iter_chrome_cookie_files(name)
@@ -398,16 +413,23 @@ def extract_from_jar(jar, name, profile=""):
         return result
     return None
 
-browsers = [
-    ("arc", browser_cookie3.arc),
-    ("chrome", browser_cookie3.chrome),
-    ("edge", browser_cookie3.edge),
-    ("firefox", browser_cookie3.firefox),
-    ("brave", browser_cookie3.brave),
-]
+DEFAULT_ORDER = ["arc", "chrome", "edge", "firefox", "brave"]
+env_browser = os.environ.get("TWITTER_BROWSER", "").strip().lower()
+if env_browser in {"arc", "chrome", "edge", "firefox", "brave"}:
+    browser_order = [env_browser] + [b for b in DEFAULT_ORDER if b != env_browser]
+else:
+    browser_order = DEFAULT_ORDER
+browser_fns = {
+    "arc": browser_cookie3.arc,
+    "chrome": browser_cookie3.chrome,
+    "edge": browser_cookie3.edge,
+    "firefox": browser_cookie3.firefox,
+    "brave": browser_cookie3.brave,
+}
 attempts = []
 
-for name, fn in browsers:
+for name in browser_order:
+    fn = browser_fns[name]
     if name in CHROMIUM_BASE_DIRS:
         cookie_files = iter_cookie_files(name)
         if not cookie_files: