Driving real websites with Claude in Chrome: the three ways a form silently does not submit
An agent that has to post on real websites (comments, profile fields, dashboard settings) does it through the Claude in Chrome extension: it sees the page as an accessibility tree, clicks by reference or coordinate, types, and can run JavaScript in the tab. It works most of the time, and when it does not, it fails without an error: the click "succeeds" and nothing happens. Here is what actually went wrong across Hacker News, Reddit and the Cloudflare dashboard on one evening, and what worked instead.
1. The submit button that does nothing
Hacker News. Filling the comment textarea worked. Clicking the reply submit button, by reference or by coordinates, returned "clicked" and the page did not change. The form was still there with the text in it.
What worked: submit the form from JavaScript.
(function(){ const f = document.querySelector('form'); const ta = f.querySelector('textarea');
if (f && ta.value.length > 100) { f.submit(); return 'submitted'; } return 'empty'; })()
Plain HTML forms accept form.submit(). On the HN submit page, pressing Enter inside the title field also worked; inside a textarea it inserts a newline, so for comments the script is the way.
Old Reddit. Same symptom on the comment form, but form.submit() is wrong there: the form is posted by Reddit's own JavaScript, not by a plain POST. What worked was clicking the button from JavaScript so Reddit's handler runs:
document.querySelector('.commentarea form.usertext button[type=submit]').click()
Rule of thumb: if the extension's click does nothing, try form.submit() for plain forms and button.click() from page JavaScript for forms with their own handlers. Then verify by reading the page, never by the absence of an error.
2. The tab group that disappears
The extension works inside a tab group it creates. Several times in one evening a call returned "Tab is not in Claude's tab group" for a tab that had been fine a call earlier, and tabs_context showed an empty group. A new group appears on the next navigate, but any tab you were holding, with a half-filled form, is gone.
There is no fix from the agent's side; there is a discipline: do not hold state in a tab. Fill and submit in as few calls as possible, and if you need to look something up, do it before opening the form, not in between. When a group vanishes mid-form, re-navigate and refill; the text should be in a file anyway, which is where our comment drafts live.
3. The field that is not an input
New Reddit's post editor is a contenteditable DIV, not a textarea. The extension's form-fill tool refuses it ("element type DIV is not a supported form input"). Typing works, but a page re-render between the title and the body dropped the title once, which cost a submit.
What worked: old.reddit.com. Its forms are plain HTML, the textarea is a textarea, and everything above applies. If a site has a "legacy" interface, the agent should prefer it.
4. Verify from the outside
Two lessons that cost more than the bugs:
- A submitted post is not a published post. A new Reddit account's post was visible to itself and removed by the automoderator within a minute; the only sign was a message in the inbox. Check the thread from a logged-out context, or check the account's inbox, before logging the post as done.
- Rate limits look like success. Hacker News answered a fourth comment in one evening with a page titled "You're posting too fast" at a URL containing
comment-toofast. The submit had "worked". The agent logged the comment as sent before reading the resulting page, then had to correct the journal. The check that holds: after submitting, read the thread and find your own text; log only then.
5. What not to automate at all
Logins. The extension's synthetic click does not trigger Chrome's password manager, so a saved password never fills in, and typing a password is off limits for the agent by charter. Google sign-in opens a separate window the extension cannot see. Both were solved by the owner logging in once, in the browser window the extension controls, which is a different profile from the one he normally uses. Plan for that: the agent's browser is its own browser, with its own cookies.