fix: persist google oauth pkce for headless auth

Store the pending OAuth state and code verifier between --auth-url and --auth-code so the manual headless flow can reuse Flow.fetch_token() without disabling PKCE.

skills/productivity/google-workspace/SKILL.md

@@ -102,7 +102,9 @@ This prints a URL. **Send the URL to the user** and tell them:
 ### Step 4: Exchange the code
 
 The user will paste back either a URL like `http://localhost:1/?code=4/0A...&scope=...`
-or just the code string. Either works:
+or just the code string. Either works. The `--auth-url` step stores a temporary
+pending OAuth session locally so `--auth-code` can complete the PKCE exchange
+later, even on headless systems:
 
 ```bash
 $GSETUP --auth-code "THE_URL_OR_CODE_THE_USER_PASTED"
@@ -119,6 +121,7 @@ Should print `AUTHENTICATED`. Setup is complete — token refreshes automaticall
 ### Notes
 
 - Token is stored at `~/.hermes/google_token.json` and auto-refreshes.
+- Pending OAuth session state/verifier are stored temporarily at `~/.hermes/google_oauth_pending.json` until exchange completes.
 - To revoke: `$GSETUP --revoke`
 
 ## Usage

skills/productivity/google-workspace/scripts/setup.py

@@ -31,6 +31,7 @@ from pathlib import Path
 HERMES_HOME = Path(os.getenv("HERMES_HOME", Path.home() / ".hermes"))
 TOKEN_PATH = HERMES_HOME / "google_token.json"
 CLIENT_SECRET_PATH = HERMES_HOME / "google_client_secret.json"
+PENDING_AUTH_PATH = HERMES_HOME / "google_oauth_pending.json"
 
 SCOPES = [
     "https://www.googleapis.com/auth/gmail.readonly",
@@ -141,6 +142,58 @@ def store_client_secret(path: str):
     print(f"OK: Client secret saved to {CLIENT_SECRET_PATH}")
 
 
+def _save_pending_auth(*, state: str, code_verifier: str):
+    """Persist the OAuth session bits needed for a later token exchange."""
+    PENDING_AUTH_PATH.write_text(
+        json.dumps(
+            {
+                "state": state,
+                "code_verifier": code_verifier,
+                "redirect_uri": REDIRECT_URI,
+            },
+            indent=2,
+        )
+    )
+
+
+def _load_pending_auth() -> dict:
+    """Load the pending OAuth session created by get_auth_url()."""
+    if not PENDING_AUTH_PATH.exists():
+        print("ERROR: No pending OAuth session found. Run --auth-url first.")
+        sys.exit(1)
+
+    try:
+        data = json.loads(PENDING_AUTH_PATH.read_text())
+    except Exception as e:
+        print(f"ERROR: Could not read pending OAuth session: {e}")
+        print("Run --auth-url again to start a fresh OAuth session.")
+        sys.exit(1)
+
+    if not data.get("state") or not data.get("code_verifier"):
+        print("ERROR: Pending OAuth session is missing PKCE data.")
+        print("Run --auth-url again to start a fresh OAuth session.")
+        sys.exit(1)
+
+    return data
+
+
+def _extract_code_and_state(code_or_url: str) -> tuple[str, str | None]:
+    """Accept either a raw auth code or the full redirect URL pasted by the user."""
+    if not code_or_url.startswith("http"):
+        return code_or_url, None
+
+    from urllib.parse import parse_qs, urlparse
+
+    parsed = urlparse(code_or_url)
+    params = parse_qs(parsed.query)
+    if "code" not in params:
+        print("ERROR: No 'code' parameter found in URL.")
+        sys.exit(1)
+
+    state = params.get("state", [None])[0]
+    return params["code"][0], state
+
+
 def get_auth_url():
     """Print the OAuth authorization URL. User visits this in a browser."""
     if not CLIENT_SECRET_PATH.exists():
@@ -154,11 +207,13 @@ def get_auth_url():
         str(CLIENT_SECRET_PATH),
         scopes=SCOPES,
         redirect_uri=REDIRECT_URI,
+        autogenerate_code_verifier=True,
     )
-    auth_url, _ = flow.authorization_url(
+    auth_url, state = flow.authorization_url(
         access_type="offline",
         prompt="consent",
     )
+    _save_pending_auth(state=state, code_verifier=flow.code_verifier)
     # Print just the URL so the agent can extract it cleanly
     print(auth_url)
 
@@ -169,26 +224,23 @@ def exchange_auth_code(code: str):
         print("ERROR: No client secret stored. Run --client-secret first.")
         sys.exit(1)
 
+    pending_auth = _load_pending_auth()
+    code, returned_state = _extract_code_and_state(code)
+    if returned_state and returned_state != pending_auth["state"]:
+        print("ERROR: OAuth state mismatch. Run --auth-url again to start a fresh session.")
+        sys.exit(1)
+
     _ensure_deps()
     from google_auth_oauthlib.flow import Flow
 
     flow = Flow.from_client_secrets_file(
         str(CLIENT_SECRET_PATH),
         scopes=SCOPES,
-        redirect_uri=REDIRECT_URI,
+        redirect_uri=pending_auth.get("redirect_uri", REDIRECT_URI),
+        state=pending_auth["state"],
+        code_verifier=pending_auth["code_verifier"],
     )
 
-    # The code might come as a full redirect URL or just the code itself
-    if code.startswith("http"):
-        # Extract code from redirect URL: http://localhost:1/?code=CODE&scope=...
-        from urllib.parse import urlparse, parse_qs
-        parsed = urlparse(code)
-        params = parse_qs(parsed.query)
-        if "code" not in params:
-            print("ERROR: No 'code' parameter found in URL.")
-            sys.exit(1)
-        code = params["code"][0]
-
     try:
         flow.fetch_token(code=code)
     except Exception as e:
@@ -198,6 +250,7 @@ def exchange_auth_code(code: str):
 
     creds = flow.credentials
     TOKEN_PATH.write_text(creds.to_json())
+    PENDING_AUTH_PATH.unlink(missing_ok=True)
     print(f"OK: Authenticated. Token saved to {TOKEN_PATH}")
 
 
@@ -229,6 +282,7 @@ def revoke():
         print(f"Remote revocation failed (token may already be invalid): {e}")
 
     TOKEN_PATH.unlink(missing_ok=True)
+    PENDING_AUTH_PATH.unlink(missing_ok=True)
     print(f"Deleted {TOKEN_PATH}")