Terminal copy/paste: UTF-8 mojibake (— becomes ‚Äî) and blockquote gutter glyphs included in selection

Summary

Selecting and copying assistant output from the Claude Code terminal UI, then pasting into another app (macOS Messages), produced mojibake for non-ASCII characters and included blockquote-gutter glyphs in the copied text.

What happened

Assistant output contained em-dashes (—, U+2014) inside a markdown blockquote. The user highlighted the rendered text in the terminal, copied, and pasted into Messages. The paste came out as:

 1. Chargebacks — what's the intended way ...
▎ 2. Idempotency — is there an idempotency key ...

Two distinct problems:

1. Encoding: — is the UTF-8 byte sequence for — (E2 80 94) decoded as Mac Roman/CP1252 — somewhere in the copy→clipboard→paste chain the UTF-8 text was re-interpreted in a legacy encoding.
2. UI glyphs in selection: ‚ñé is the UTF-8 sequence for ▎ (U+258E, left one-quarter block) — the blockquote gutter bar rendered by the terminal UI was included in the text selection and copied along with the content.

Environment

• Claude Code CLI on macOS (Darwin 25.3.0), default Terminal setup
• Paste target: macOS Messages
• Model session: interactive terminal (not IDE extension)

Expected

• Copied text should paste as clean UTF-8 (em-dashes survive)
• Rendering-only glyphs (blockquote bars, borders) should not be part of the copyable text selection

Workaround

Avoiding non-ASCII punctuation in text meant for copy-paste; not viable long-term since assistant output naturally contains typographic characters.