Fatal panic: Unicode boundary error with hourglass emoji (⏳)

Description

Claude Code crashed with a fatal panic due to improper UTF-8 string slicing when handling the hourglass emoji (⏳).

Error Output

thread '<unnamed>' (24243) panicked at /rustc/ed61e7d7e242494fb7057f2657300d9e77bb4fcb/library/core/src/str/mod.rs:833:21:
byte index 2 is not a char boundary; it is inside '⏳' (bytes 0..3) of `⏳`
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
fatal runtime error: failed to initiate panic, error 5, aborting
[1]    2455 abort      claude --strict-mcp-config --mcp-config ~/.claude/mcp-profiles/dev.json

Environment

• Claude Code version: 2.0.76
• Platform: macOS (Darwin 25.2.0)
• MCP config: ~/.claude/mcp-profiles/dev.json
• Command: claude --strict-mcp-config --mcp-config ~/.claude/mcp-profiles/dev.json

Context

The crash occurred while Claude was autonomously working on a project. The user was not actively involved at the time of the crash.

Root Cause

The error indicates that Rust code attempted to slice a UTF-8 string at byte index 2, which falls inside the multi-byte emoji character '⏳'. This emoji is 3 bytes in UTF-8 encoding (bytes 0..3), so slicing at byte 2 is invalid and violates character boundaries.

Expected Behavior

String operations should respect UTF-8 character boundaries when slicing/indexing strings containing multi-byte Unicode characters.

Additional Notes

This appears to be a Unicode handling bug in Claude Code's Rust codebase, likely in code that processes or displays status indicators or emoji.