75 lines
2.4 KiB
Markdown
75 lines
2.4 KiB
Markdown
---
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phase: P9
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component: kebab-rag + kebab-app
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task_id: p9-fb-15
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title: "RAG multi-turn — history-aware prompt + token budget"
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status: completed
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depends_on: []
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unblocks: [p9-fb-16, p9-fb-17, p9-fb-18]
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contract_source: ../../docs/superpowers/specs/2026-04-27-kebab-final-form-design.md
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contract_sections: [§7 RAG]
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source_feedback: p9-dogfooding-feedback.md item 13
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---
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# p9-fb-15 — RAG multi-turn core
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## Goal
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`kebab-rag` 가 conversation history (`Vec<Turn>`) 를 받아 prompt 빌드. token budget 안에서 retrieval k 와 history truncation 정책으로 fit.
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## Allowed dependencies
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- 기존 kebab-rag deps.
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- `tiktoken-rs` 또는 LLM family-specific tokenizer (gemma 토큰화). 우선 char 기반 ÷4 근사 (cheap & 의존 X).
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## Public surface
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```rust
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pub struct Turn {
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pub question: String,
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pub answer: String,
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pub citations: Vec<Citation>,
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pub ts: OffsetDateTime,
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}
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pub fn ask_with_history(
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cfg: &Config,
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new_question: &str,
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history: &[Turn],
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stream: Sender<RagEvent>,
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) -> anyhow::Result<Answer>;
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```
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`kebab-app` 도 `ask_with_config_and_history(cfg, q, history, stream)` 추가.
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## Behavior contract
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- prompt 구조: `system_prompt + history_serialized + retrieved_chunks + new_question`. 형식 (roles 또는 plain text) 는 `prompt_template_version` bump (`rag-v1` → `rag-v2`).
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- token budget: `cfg.rag.max_context_tokens`.
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- 우선순위: system + new_question 항상 포함.
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- 다음: retrieved chunks (k=cfg.search.default_k 부터, budget 초과시 k 감소).
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- 마지막: history. budget 남은 만큼 newest turn 부터 포함, 부족하면 oldest turn drop. 최소 0 turn 까지 가능.
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- retrieval query: `new_question + " " + last_turn.answer.first_N_chars(200)` concat (cheap query expansion). LLM 기반 standalone question rewriting 은 P+.
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- streaming: `RagEvent::Token(s)` / `RagEvent::Done(answer)` / `RagEvent::Error(e)`.
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## Test plan
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| kind | description |
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|------|-------------|
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| unit | history 5 turn → token budget 초과 시 oldest 부터 drop |
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| unit | retrieved_chunks vs history 의 priority |
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| integration | 가짜 history (Q1/A1) + new Q2 → prompt 에 Q1/A1 포함 (snapshot) |
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## DoD
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- [ ] `cargo test -p kebab-rag -p kebab-app` 통과
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- [ ] `prompt_template_version` bump (`rag-v2`)
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- [ ] HOTFIXES X (신규)
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- [ ] frozen design §7 RAG 절 갱신 (multi-turn 정책)
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## Out of scope
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- LLM 기반 question rewriting (P+)
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- conversation 영속화 (p9-fb-17)
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- UI (p9-fb-16, p9-fb-18)
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