Model skips mandatory CLAUDE.md session-start instructions when task context is present

Description

When CLAUDE.md contains a mandatory session-start instruction (e.g. "run /msq-ops IMMEDIATELY at the start of every session, before doing anything else"), the model skips it if the conversation opens with task context that makes it feel like it has "enough" to start working.

Reproduction

1. Add a mandatory startup instruction to CLAUDE.md:

``
## Session Start (MANDATORY)
At the start of every session, load the operational reference by running /msq-ops.
``

1. Reinforce it in auto-memory (MEMORY.md):

``
## RULE #1 - ALWAYS RUN /msq-ops AT SESSION START (NON-NEGOTIABLE)
``

1. Start a new session where the first user message includes task context (e.g. a bug description with file paths and a fix direction)

1. Expected: Model runs the mandatory startup command before doing any work
2. Actual: Model jumps straight into the task, skipping the startup instruction entirely

Impact

In this case, the skipped operational reference contained a "Supabase Query Safety" section documenting the 1000-row default limit. The model then wrote a bare .select() query that hit exactly that limit, causing a bug that took multiple iterations to diagnose. The startup instruction existed specifically to prevent this class of error.

Analysis

The model appears to prioritize "being helpful quickly" over following explicit mandatory instructions. When task context is rich enough to start working, the startup ritual gets deprioritized despite being marked MANDATORY and NON-NEGOTIABLE in two separate files.

This is distinct from the model not knowing about the instruction - when asked, it correctly identified the rule and where it was documented. It simply chose not to follow it.

Environment

• Claude Code CLI
• Model: claude-opus-4-6
• Platform: Windows 11