[FEATURE]

Preflight Checklist

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• [x] This is a single feature request (not multiple features)

Problem Statement

When working in a long Claude Code session, there is no mechanism to ensure a set of persistent instructions are included with every user prompt throughout the conversation. As the context window grows, even instructions defined in CLAUDE.md can be pushed out, requiring the user to constantly re-remind Claude of standing obligations — such as maintaining a changelog, implementation log, or decision log.

This becomes particularly painful in active development sessions where Claude is expected to keep key project documents up to date as work progresses, without explicit prompting on every turn.

Proposed Solution

Introduce a session-level system prompt capability in Claude Code that:

1. Allows the user to define a persistent prompt (inline or via a dedicated file such as CLAUDE.session.md) that is automatically injected into every user message for the duration of the session
2. Is distinct from CLAUDE.md — which is project-wide context — and instead scoped to runtime behavior reminders
3. Survives context window pressure by being re-injected at the infrastructure level, not stored as a conversation turn

Alternative Solutions

_No response_

Priority

Medium - Would be very helpful

Feature Category

Configuration and settings

Use Case Example

Use Case: Maintaining Project Logs During Active Development

A developer is building a new API integration in Claude Code. At the start of the session they define a session prompt:

"After every meaningful change, update CHANGELOG.md with what changed, IMPLEMENTATION.md with technical decisions made, and DECISIONS.md with the reasoning behind key choices."

Step-by-step:

1. Developer asks Claude to scaffold a new service class — Claude creates the file and appends an entry to IMPLEMENTATION.md
2. Developer asks Claude to add error handling — Claude implements it and logs the decision rationale to DECISIONS.md
3. Developer asks Claude to write unit tests — Claude writes the tests and updates CHANGELOG.md
4. Two hours later, context window is large — without session prompt re-injection, Claude stops updating logs silently
5. With this feature: the session prompt is re-injected automatically — logs stay current regardless of conversation length

Result: At the end of the session the developer has a fully up-to-date paper trail of every change, decision, and implementation note — with zero manual reminding.

Additional Context

_No response_