Injection Timing Overview

NOTE

Each configuration file has a defined "when" and "how" it gets injected into the LLM's context window. Understanding this mechanism reveals principles that apply to other LLM tools (Cursor, Cline, Copilot, etc.).

Injection Timing Inventory

Layer	Target	Injection Timing	Context Consumption
Resident	System Prompt	Session start	Always (every turn)
Resident	CLAUDE.md	Session start	Always (every turn)
Conditional	`.claude/rules/`	Glob pattern match	Only when conditions match
On-Demand	Skills	User call or LLM decision	Only when invoked
On-Demand	Agents	Agent() tool invocation	Separate context (no main consumption)
Tool Definition	MCP Tools	Session start	Always (as tool definitions)
Accumulated	Conversation history	Added each turn	Cumulative (compressible via /compact)
Outside Context	settings.json	-	None
Outside Context	Hooks	-	None (except Prompt Hook)

Four Injection Patterns

1. Resident Injection (Always Loaded)

Loaded at session start and consumed every turn.

Session start → Inject System Prompt + CLAUDE.md
Turn 1: [System Prompt][CLAUDE.md][User Input 1]
Turn 2: [System Prompt][CLAUDE.md][User Input 1][Response 1][User Input 2]
...

Because it's always resident, the impact on context budget is largest. → This is the basis for the 200-line limit in CLAUDE.md

2. Conditional Injection

Injected only when specific conditions (glob pattern match) are met.

Edit *.component.ts → component-rules are injected
Edit *.spec.ts → testing-rules are injected
Edit *.cs → the above rules are not injected

→ Countermeasure for Priority Saturation. Inject needed rules only when needed.

3. On-Demand Injection

Injected via user invocation or LLM's automatic decision.

Skills are deployed within the main context (equivalent to import). Agents execute in independent context (equivalent to separate process).

4. Outside Context (Runtime Layer)

Never enters the LLM's context window. Claude Code's runtime handles it.

settings.json → Permission control, environment variables Hooks → Execute shell commands on lifecycle events

Design Decision Flowchart

When adding new rules or information, decide in the following order.

Previous: What the LLM Sees in the Context Window

Next: Context Budget as a Concept

Injection Timing Overview ​

Injection Timing Inventory ​

Four Injection Patterns ​

1. Resident Injection (Always Loaded) ​

2. Conditional Injection ​

3. On-Demand Injection ​

4. Outside Context (Runtime Layer) ​

Design Decision Flowchart ​