Runtime system-reminder claims to supersede CLAUDE.md project instructions

A system-reminder is injected mid-session (twice appended to tool results, once with no tool call) instructing Co-Authored-By and 'Generated with Claude Code' trailers, prefixed 'this replaces any earlier attribution guidance'. The project CLAUDE.md explicitly forbids attribution trailers and states it overrides harness defaults. Verified locally: no hooks, no MCP servers, no plugins enabled, and the string exists nowhere on disk. The text is model-keyed (Opus 5 in one session, Sonnet 5 in another), so it is generated by the harness. Request: project-level instructions should take precedence over default attribution guidance, and defaults should not assert that they replace them.

Start by reproducing the reported runtime system-reminder with a project CLAUDE.md that forbids attribution trailers and with hooks, MCP servers, and plugins disabled. Then trace where default attribution guidance is assembled or injected in the harness and how it is ordered against project instructions. Done means project-level CLAUDE.md guidance takes precedence and the default reminder no longer claims to replace it.

索引モデルが issue の本文から書いたものです。