claude-bionify

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claude-bionify bolds the leading part of each word in Claude's streamed replies, giving your eye a fixation point per word. This is the bionic-reading technique, inspired by the eye-movement research showing that we read by fixating a single convenient position toward the start of each word, where its opening letters carry the most information for recognising it (Rayner, 1979; O'Regan et al., 1984).

It only changes how text looks on screen. What gets saved to the transcript and what Claude reads stays the original, unbolded text, which you can reopen any time with the Ctrl+O transcript view.

Features

• ⚡ Faster, calmer reading. Fixation points pull your eye word to word through long answers.
• 🌍 Any language. Unicode-aware, so accents and non-Latin scripts bold correctly, not just English.
• 🎚️ Three boundary modes. fraction, syllable, or log — see Configure.
• 🧩 Markup-aware. Code, links, URLs, paths, and acronyms stay intact (what it touches).
• 🔒 Private, zero-dependency. Nothing to install, no network, no telemetry — it runs entirely on your machine.
• 🪶 Crash-safe. On any error it falls back to the original text.

Install

/plugin marketplace add abullard1/claude-bionify
/plugin install claude-bionify@claude-bionify

claude-bionify is active right away. Turn it off or back on any time with /claude-bionify:off and /claude-bionify:on, or from /plugin.

Configure

When you enable the plugin, Claude Code prompts for these (all optional):

Control it live

Change claude-bionify mid-session without a reload or any config editing. The next reply reflects it right away:

These write a small override file that the hook reads on every message, so changes take effect immediately and persist until you reset.

Themes

claude-bionify also ships seven color palettes for Claude Code's /theme picker (custom:claude-bionify:<name>). They retint Claude Code's interface and are independent of the bolding. Each one also tints diffs, the background behind your messages, and mouse selection in its own colors, and every text-on-background pair meets WCAG AA contrast (4.5:1; 3:1 for the changed-word highlight inside a diff line).

Plugin themes are read-only. Highlight one in /theme and press Ctrl+E to copy it into ~/.claude/themes/ and tweak your own.

How it works

Claude streams a reply ▸ claude-bionify ▸ bolded text in your terminal

As each batch of Claude's reply streams in, claude-bionify bolds it just before it reaches your screen — so only what you see changes, never the text itself.

What it touches

• Bolded: ordinary prose words.
• Left alone: inline `code`, fenced code blocks, markdown link/image targets, URLs, emails, file paths and filenames, ALL-CAPS acronyms, and any text Claude already wrapped in **bold**.
• Never touched: your own input and tool output.

Requirements

• Claude Code 2.1.152 or newer (the release that added the MessageDisplay hook)
• Python 3.10+, reachable as python3 or through the py launcher (see below)
• A terminal that renders markdown bold (any modern terminal)

On macOS, Linux, and WSL the hook runs as python3. Native Windows is different: the python.org installer creates python.exe and py.exe but no python3.exe, and Windows ships a Microsoft Store placeholder named python3.exe that exits without running Python. The hook therefore also launches through the py launcher.

Two consequences there. Bolding works, but the /claude-bionify:* commands do not, because they run through a shell where no fallback syntax suits both Git Bash and PowerShell; installing Git for Windows, or a real python3 on PATH, brings them back. And if your Python came from conda, uv, or pyenv-win, neither name may resolve, so point the hook at your interpreter with a MessageDisplay entry in ~/.claude/settings.json whose command is the absolute path to your python.exe.

If nothing looks bold but /claude-bionify:status reports ON, check the terminal before the plugin: ask Claude to write a plain **word** in a reply. If that is not bold either, the hook is not the problem. Windows Terminal has a per-profile Bold text style setting (intenseTextStyle in its settings.json) which on bright only shifts the foreground colour, invisible in schemes where the normal and bright variant