Spurious <<ccr:XXXXXXXX>> tokens injected into Bash tool output (grep/wc results), not present in source file

During a session, repeated Bash tool calls (grep, wc) against a locally-downloaded HTML file consistently appended a trailing line like:

<<ccr:e559f27762df10227c75e7c3>>

... to the tool output. This happened 6 times across different commands, each time with a different hex suffix, always at the very end of the output.

Verified the string does NOT exist in the source file:

grep -c 'ccr:' file.html # => 0
grep -c '<<' file.html # => 0

So this was injected somewhere between the actual command output and what got surfaced to the model, not present in the file being read. No visible impact on the data returned, but it looks like an internal control/tracking token leaking into user-facing tool output.

Environment: Claude Code CLI, Windows 11, Bash tool (Git Bash), model claude-sonnet-5.

Happy to provide the full transcript/session if useful.