[BUG] Fullscreen TUI: failed Bash tool output is empty when expanded

Still a problem on 2.1.186 on linux as well

Still broken on v2.1.185 (macOS, Ghostty, fullscreen TUI). Worse than the original repro: the ⎿ result row is completely absent — not just empty when expanded, but the entire row is missing. Successful Bash calls render normally.

Workaround via PostToolUseFailure hook using systemMessage

The hook fires after the tool result is captured, and systemMessage renders visibly in the TUI even when the ⎿ row is dropped. Wire it up in ~/.claude/settings.json:

{
  "hooks": {
    "PostToolUseFailure": [
      {
        "hooks": [
          {
            "type": "command",
            "command": "bun /path/to/posttool-failure-hook.ts"
          }
        ]
      }
    ]
  }
}

#!/usr/bin/env bun
// posttool-failure-hook.ts — surfaces failed Bash output via systemMessage
const hookData = JSON.parse(await Bun.stdin.text());
const error = typeof hookData.error === "string" ? hookData.error : "";
console.log(JSON.stringify({
  suppressOutput: false,
  systemMessage: error ? `Tool failed — output: ${error}` : "Tool failed",
  hookSpecificOutput: { hookEventName: "PostToolUseFailure" },
}));
process.exit(0);

The error field in the hook payload contains the combined stdout+stderr of the failed tool. This renders as a visible banner in fullscreen TUI until the renderer bug is fixed.

Stronger forensic refile of this surface: #77778

On fullscreen TUI the failure is worse than “empty when expanded” for us: the entire ⎿ result row is absent (not just blank on expand). stdout+stderr are present in the session JSONL tool_result and the model receives them — only the fullscreen paint path drops the body. Success path + classic TUI (/tui default) still render correctly.

Includes end-to-end controls, JSONL excerpt, and a working PostToolUseFailure → systemMessage workaround until the renderer is fixed.

https://github.com/anthropics/claude-code/issues/77778

I don't believe this is exclusive to fullscreen mode