Double trigger acceleration is the vesting structure requiring two events before unvested shares accelerate: a change of control plus a qualifying termination. The change of control (acquisition, merger, asset sale) plus termination without cause or resignation for good reason within a 12-18 month window means holders accelerate only if the acquirer terminates them or pushes them out, protecting both the holder and the acquirer's retention lever. It is the modern default acceleration structure for founders and executives in venture-backed companies and the structure most aligned with investor preferences.
The mechanic of double trigger: