[MODEL] @-include instructions followed with lower reliability than inline CLAUDE.md content (re: #34043)

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Type of Behavior Issue

Claude ignored my instructions or configuration

What You Asked Claude to Do

~/.claude/CLAUDE.md includes @~/.claude/AGENTS.md and states "Follow all rules in AGENTS.md above." The model confirms it sees AGENTS.md content when asked.

What Claude Actually Did

Instructions defined inline in CLAUDE.md are consistently followed. Identical instructions in @-included files are selectively ignored under the same conditions. Moving an instruction verbatim from AGENTS.md into CLAUDE.md improves compliance immediately, with no other change.

Observed examples (both instructions were already in AGENTS.md before being added to CLAUDE.md):

• "Always branch from origin/<target>" — ignored from AGENTS.md; followed after adding to CLAUDE.md
• "NEVER add Co-Authored-By trailers referencing Claude or Anthropic" — ignored from AGENTS.md; followed after adding to CLAUDE.md

Expected Behavior

Instructions in @-included files should carry the same authority as inline instructions, especially when the including file explicitly states they must be followed.

Why This Is Not a Duplicate of #28158

#28158 reports intermittent general non-compliance suspected to be caused by model substitution or load balancing, with Opus 4.6 on the direct API.

This issue is a controlled differential experiment: the same instruction, moved verbatim from an @-included file into inline CLAUDE.md, is followed reliably every time with no other variable changed. The failure mode is not "instructions ignored generally" but specifically that @-included content is treated with lower authority than inline content. This points to a defect in how @-include context is weighted or surfaced, not a general compliance regression.

#34043 was incorrectly auto-closed as a duplicate of #28158 and cannot be re-opened (external repo). This issue continues that report.

Can You Reproduce This?

Yes, every time with the same prompt

Claude Model

Sonnet 4.6

Claude Code Version

2.1.74 (Claude Code)

Platform

AWS Bedrock