SYSTEM_PROMPT_DYNAMIC_BOUNDARY
- Entity ID:
ent-20260419-2fbd1c4da55c - Type:
concept - Scope:
shared - Status:
active - Aliases: dynamic boundary marker, prompt cache boundary
Description
Marker in Claude Code's system prompt assembly that splits the static cacheable half from the dynamic session-specific half, enabling prompt prefix caching. Estimated to cut inference cost by roughly 80% on long Opus sessions.
Key claims
- SYSTEM_PROMPT_DYNAMIC_BOUNDARY saves ~80% inference cost on long Opus sessions
- Cache Boundary Marker is invisible to the model
- Cache-friendly workflows partially absorb 4.7 tokenizer overhead
- Leak operationalizes prompt structure as a cost-control lever
Relations
- System Prompt Assembly --[uses]--> SYSTEM_PROMPT_DYNAMIC_BOUNDARY
- SYSTEM_PROMPT_DYNAMIC_BOUNDARY --[implements]--> Cache-Prefix-Change-Suffix Principle
- Tokenizer-Effort-Cache Cost-Multiplier Model --[informs]--> SYSTEM_PROMPT_DYNAMIC_BOUNDARY