is_regex_pattern only recognized the BRE-escaped form \| and not a bare |,
so a pattern like "Jornak|Silverlake|Orissa" was treated as one literal
string (including the pipe characters) and silently returned no matches.
This contradicted the tool docstring, which explicitly advertises
"error|warn" as an auto-detected regex example, and misled models into
concluding the searched terms were absent from the file.
Checking for a bare | also covers the escaped form, since \| contains |,
and normalize_regex already converts escaped pipes before compilation.
Literal patterns without regex metacharacters are unaffected.
Fixes#26781
When called without attached model knowledge and given a caller-supplied knowledge_id, search_knowledge_files passed it straight to Knowledges.search_files_by_id, which does not enforce ownership on knowledge_id. An authenticated user who happened to know a target UUID could enumerate file metadata (filename, file id, KB id, KB name, updated_at) from any knowledge base, bypassing the AccessGrants permission model.
Mirror the same admin/owner/AccessGrants check the attached-KB branch already uses, matching the sibling query_knowledge_files function.
Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
