Files
hermes-agent/tools
Teknium 8bbda8ff33 Port from block/goose#10746: strip invisible Unicode TAG chars from MCP content
Unicode TAG characters (U+E0000-U+E007F) render as nothing in terminals
and chat UIs but are fully visible to LLM tokenizers, making them an
ASCII-smuggling prompt-injection channel for untrusted MCP servers.

- tools/ansi_strip.py: new strip_unicode_tags() with fast path; unlike
  goose we preserve valid emoji tag sequences (U+1F3F4 base + tag spec +
  U+E007F cancel), so regional flags survive.
- tools/mcp_tool.py: applied at every MCP text ingestion point — tool
  result text blocks, embedded resource text, read_resource contents,
  get_prompt message content, and tool descriptions entering the schema.
- tests/tools/test_unicode_tag_strip.py: smuggled-instruction vectors,
  goose's test vector, emoji-tag-sequence preservation, ZWJ untouched.
2026-08-16 22:08:05 -07:00
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