This issue has been available for more than 365 days, and should be re-evaluated. Please re-triage this issue.
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Are you really sure this is GoodFirstBug?

> Are you really sure this is GoodFirstBug?
Pretty sure.  I think the problem is localized to the function OmniboxEditModel::OnAfterPossibleChange()
probably this particular block and its helper function call
  // Change to keyword mode if the user is now pressing space after a keyword
  // name.  Note that if this is the case, then even if there was no keyword
  // hint when we entered this function (e.g. if the user has used space to
  // replace some selected text that was adjoined to this keyword), there will
  // be one now because of the call to UpdatePopup() above; so it's safe for
  // MaybeAcceptKeywordBySpace() to look at |keyword_| and |is_keyword_hint_|
  // to determine what keyword, if any, is applicable.
  //
  // If MaybeAcceptKeywordBySpace() accepts the keyword and returns true, that
  // will have updated our state already, so in that case we don't also return
  // true from this function.
  return (state_changes.new_sel_start != user_text_.length()) ||
         !MaybeAcceptKeywordBySpace(user_text_);
https://cs.chromium.org/chromium/src/components/omnibox/browser/omnibox_edit_model.cc?l=1182-1194

I can't seem to reproduce the bug. Any tips on how to reproduce?

I cannot reproduce anymore either.  Perhaps it was fixed as a side effect of one of thomasanderson@'s changes to keyword mode tracking?