embeddings: alternation patterns (a|b|c) skip the embedding daemon and fall back to lexical-only

Start in src/hooks/grep-direct.ts and src/shell/grep-interceptor.ts, in patternIsSemanticFriendly and where it decides whether to call the embedding path (searchDeeplakeTables). Verify both copies match and that alternation handling is the same in each file before editing. Run the provided repro command with HIVEMIND_DEBUG=1 and inspect ~/.deeplake/hook-debug.log for summary_embedding <#> ARRAY activity. Completion is when the alternation query uses the embedding branch and the debug log shows embedding hits for paraphrase-style matches.

Severity

Medium-high — limits the embedding feature's main UX (synonym recall is exactly the case embeddings are designed for).

Where

• src/hooks/grep-direct.ts:36-50 — patternIsSemanticFriendly
• src/shell/grep-interceptor.ts:43-50 — same function (duplicated)

Repro

On any workspace with embedding rows, ask Claude Code:

HIVEMIND_DEBUG=1 claude -p 'Search hivemind for sessions about silent data loss or concurrent-writer corruption. Use grep -r over the memory path.'

CC issues a Bash grep -r with an alternation pattern like silent data loss|data loss|concurrent writer|writer corruption|race condition|lost write. The debug log (~/.deeplake/hook-debug.log) shows zero summary_embedding <#> ARRAY[…] queries — only lexical ILIKE matches and path browses. CC's answer is correct only when the literal keywords match a summary; it misses paraphrases.

Root cause

patternIsSemanticFriendly rejects any pattern with more than 1 regex metacharacter, and | counts as a metacharacter:

const meta = pattern.match(/[|()\[\]{}+?^$\\]/g);
if (!meta) return true;
return meta.length <= 1;

When false, the dispatcher skips the embedding daemon call and searchDeeplakeTables runs the lexical-only branch.

But | is exactly the synonym-list use case where embeddings shine — different surface forms of the same concept. The original intent of the filter ("don't waste an embed call on regex like [a-z]+\.com") shouldn't reject synonym alternations.

Proposed fix

Drop | from the metacharacter blacklist + cap the alternative count to guard against pathological inputs:

function patternIsSemanticFriendly(pattern: string, fixedString: boolean): boolean {
  if (!pattern || pattern.length < 2) return false;
  if (fixedString) return true;
  const meta = pattern.match(/[()\[\]{}+?^$\\]/g);  // dropped `|`
  if (meta && meta.length > 1) return false;
  // Still gate on alternative count to avoid 50-element synonym blasts:
  const altCount = pattern.split("|").length;
  return altCount <= 8;
}

Apply to both grep-direct.ts and grep-interceptor.ts (or extract into a shared helper while we're at it).

Acceptance

After fix, the same repro prompt should produce ≥ 1 summary_embedding <#> ARRAY[…] query in the debug log, and CC's answer should include sessions matched by paraphrase (not just literal keyword).

Out of scope

• Recommending Grep tool over Bash grep in the SessionStart prompt (Bash grep already routes through handleGrepDirect, which is the embedding path).
• Removing the duplication between the two patternIsSemanticFriendly definitions (separate refactor).

Found during the embedding_generation branch validation, see commits 4e956fa + f9f10f3.