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GAP-PERF-001: Prompt Caching (Ephemeral) overview
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GAP-PERF-001: Prompt Caching (Ephemeral)
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GAP-PERF-001: Prompt Caching (Ephemeral)
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docs/harness-features-backlog/gaps/performance/gap-perf-001
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# GAP-PERF-001: Prompt Caching (Ephemeral)
| Field | Value |
|-------|-------|
| Category | performance |
| Priority | Critical |
| Effort | L |
| Status | Missing |
## Description
Implement prompt caching so that stable prompt segments are reused across orchestration iterations, avoiding redundant token processing on every harness invocation.
## Current State
Each harness invocation via `invokeHarness()` spawns a fresh CLI process with no mechanism to carry prompt cache state between invocations. Every iteration pays full prompt processing cost.
## Target State
Stable prompt strata are cached between iterations. Cache hit rate is measurable via `tokens:stats`. For a 20-iteration run with a 50K-token system prompt, redundant processing is eliminated.
## Dependencies
- [GAP-PROMPT-001](../prompt-engineering/GAP-PROMPT-001.md) -- strata separation identifies cacheable segments
## Key Files
| Component | Path |
|-----------|------|
| Harness invoker | `packages/sdk/src/harness/invoker.ts` |
| Prompts module | `packages/sdk/src/prompts/` |
| Token stats CLI | `packages/sdk/src/cli/` |
## Recommendation
Phase 2 implementation. Options: direct API integration bypassing harness CLI (highest savings), session-persistent prompt prefix with harness session binding, or harness-side prompt prefix caching with TTL.
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- page:docs-harness-features-backlog·PageHarness Features Backlog: Gap Analysis (Restructured)