Add additional_context to beforeSubmitPrompt hook output

[Bogdan_Parhomenko (Богдан Пархоменко)]

Great feature request! Having additional_context available on beforeSubmitPrompt would indeed open up a lot of powerful workflow automations.

However, just a heads-up to @mibogo and the dev team: the additional_context functionality you mentioned for postToolUse is actually completely broken in the current builds (e.g., 3.1.15).

Currently, the postToolUse hook suffers from empty input payloads (no stdin, argv, or env vars), the output context is completely discarded and never reaches the model, and it fires very intermittently.

So while I completely support adding this to beforeSubmitPrompt, the engineering team urgently needs to fix the underlying hook infrastructure first. We are tracking the major bugs with the existing implementation here:

Native postToolUse hooks accept and log additional_context successfully, but the injected context is not surfaced to the model

Adding data points on Cursor 3.1.15 (macOS, 2026-04-21). The postToolUse input side also looks unpopulated, on the same path where the response is discarded — so even fixing the output plumbing wouldn’t be sufficient on its own. Hook script logs process.argv, CURSOR_* env vars, and stdin length on every invocation. Representative entries: [2026-04-21T21:53:59.071Z] spawn pid=25047 argv=[] env= [2026-04-21T21:53:59.077Z] stdin-end bytes=0 [2026-04-21T21:55:37.036Z] spawn pid=26394 argv=[] env…

Once the core plumbing is fixed, expanding it to beforeSubmitPrompt would be amazing!