[Bug] Pasting large/single-line JSON hangs the UI (v0.4.3) #377

Environment

• Deep Code CLI version: 0.4.3
• OS: macOS (Darwin 25.5.0, arm64)
• Node: v22.22.0
• Shell: zsh

Summary

Pasting a moderately large JSON payload (about 1 KB, containing long
base64url lines) into the prompt input causes the UI to hang. New inputs
cannot be submitted until the app is restarted. This may be a regression
or edge case in the large-paste collapsing introduced in PR #102.

Steps to reproduce

1. Start deepcode in any project.
2. Copy the JSON below (or any ~1 KB JSON with a long single-line
   ciphertext field).
3. Paste it into the prompt input with Cmd+V.
4. Observe: the UI freezes; typing and Enter no longer respond.

Sample payload that triggers it

  {
  _id: '7c0c4fe3-b19f-4610-9953-5385b117141d',
  eventId: 'b242b875-8aa3-45aa-9698-b44b91142903',
  epoch: NumberInt('1'),
  cryptoVersion: NumberInt('1'),
  nonce: 'u-h-Hw7cvjDzSe5t',
  ciphertext: 'vTW5glkviFIjhdquhA1SdkSOE1yrVPA0tHWIc9nqBolrllnIgz2dbdx84L0FiTgIp2JiwLQatpGam9yBHDTvzj9kMpLYfRtaFrUOKv1eX7bNh4n9ct1Qh_umW6EzXKWSjnIvNYBNMGDTn2KAOPm0_tRKkB39DelXrOiSNFIyEhjVFhbFVlq0t_XnbrkMtxey-Z2rqSSSeb-1fZsMqisZf2kFrmoOPWiblkBLeLz2eWWxI9o1imUYoTPql8v-3NVPUI93nJCJwk47qAcz6XIa7HzUBtHrCA8Y7KN1RQ7JQPUwkuvwwSxI2KWoO8ljF-c9U2vVQHunSY46QaOPAobYrj69GvpS_EZn4rN0D25Z00oAQPA7VUIIvdGN_fvH76h4EVz6zuvIuBce_k-nIVsOPFda7Re-GctzDzPwwtUDOqdawdZDkV7qjPzqQaeD7KPfzBD2MYcrHqE',
  signature: '9vcimWs_yP7ZRpjv7s2IHn5kL4Ypb8kZ2ecE7gu4aizClfzWjeX_YXONQDK5_X0w1SZQV3gYUip18bekw9KtWw',
  vaultId: '87494ddc-09ba-477c-acdc-5fc2d21c985c',
  deviceId: '15b32b79-0072-4931-b3bc-1a73dae15d88',
  cursor: NumberLong('1'),
  requestDigest: 'AYU9riZ7zF8FDXVAIgINt0Gn9OdXN0LZj8S6NIhO7hk',
  createdAt: ISODate('2026-10-17T18:58:13.684Z')
}

Expected behavior

• Per PR feat(ui): add bracketed paste with large-paste marker collapsing #102, a large paste should collapse to a compact marker
  (e.g. [paste #1 +63 lines]), or the text should simply be inserted.
• The input should remain responsive.

Actual behavior

• The UI hangs during/after the paste. Enter does nothing; the only
  recovery is restarting Deep Code.
• Small pastes work fine.

Workaround

Saving the JSON to a file and asking the agent to read the file path
works reliably, so the bug is specific to the paste path.

Related

• PR feat(ui): add bracketed paste with large-paste marker collapsing #102 (large-paste marker collapsing) — likely regression or
  edge case (very long single-line content)
• 输入框重复堆叠 #151 (input box rendering issues)
• [Bug] 输入框英文单词在行尾被硬截断，应整词换行 #327 (input box text wrapping issues)

Suggested investigation

• Very long single-line pastes may bypass or break the bracketed-paste /
  marker-collapsing path.
• PR feat(ui): add bracketed paste with large-paste marker collapsing #102 notes expand/collapse briefly clears Ink content;
  the hang may be in that render path.

Note: This draft was created with the help of deepcode.