FalkorDB fulltext query fails on a lone _ token #2142

Bug: FalkorDB fulltext query fails on a lone _ token

Version: graphiti-core 0.31.2, FalkorDB driver

sanitize_falkor_fulltext_query (graphiti_core/driver/falkordb/fulltext.py) replaces separator characters with spaces but keeps _. Inputs such as name _ date or name (_) date therefore yield a token that is only _. RediSearch rejects a token without a letter or digit as a syntax error, so the whole fulltext query fails.

Because build_falkor_fulltext_query is also used inside add_episode (entity/edge dedup search), this crashes ingestion, not just search.

Repro

from graphiti_core.driver.falkordb import fulltext
fulltext.build_falkor_fulltext_query("name (_) date")
# -> ' (name | _ | date)'  -> RediSearch "Syntax error" when executed

We hit it in add_episode with LLM-extracted entity names of the form <name>_<date>.

Related: other symbol-only tokens survive too, e.g. "Report – _2025" -> ' (Report | – | _2025)'.

Suggested fix

After sanitizing, drop tokens that contain no alphanumeric character, e.g.

" ".join(w for w in sanitized.split() if any(c.isalnum() for c in w))

We currently patch the sanitizer at module level as a workaround.