diff --git a/openspec/changes/idd-ask-skill/.openspec.yaml b/openspec/changes/idd-ask-skill/.openspec.yaml
new file mode 100644
index 0000000..2c990ac
--- /dev/null
+++ b/openspec/changes/idd-ask-skill/.openspec.yaml
@@ -0,0 +1,3 @@
+schema: spec-driven
+created: 2026-07-18
+created_by: che cheng <kiki830621@gmail.com>
diff --git a/openspec/changes/idd-ask-skill/design.md b/openspec/changes/idd-ask-skill/design.md
new file mode 100644
index 0000000..5a43cdc
--- /dev/null
+++ b/openspec/changes/idd-ask-skill/design.md
@@ -0,0 +1,37 @@
+# Design: idd-ask-skill
+
+## D1 — 與 find 的分工：lookup vs QA（防第 4 員定位稀釋）
+
+| | `idd-find` | `idd-ask` |
+|---|---|---|
+| 問題 | 「有沒有處理過類似 X、在哪」 | 「當時為什麼這樣決定 / X 是怎麼運作的」 |
+| 輸出 | ranked hits（人自己去讀） | **合成答案**（AI 讀完引用回答） |
+| 讀取深度 | metadata + overlay（O(1)/hit） | top-N 命中的**全文**（body + comments） |
+| Token 成本 | 低 | 高（有界：top-N 預設 5、`--limit` 可調） |
+
+ask 的輸出**必附** `### Referenced Issues`，讓人可以 fall through 到 find 式的自行閱讀 — 兩員互補成「先問、不滿意再自己翻」的鏈。
+
+## D2 — Retrieval delegate idd-find backend（family 慣例：不重造唯讀查詢）
+
+Step「搜尋」直接沿用 `idd-find` 的 search backend 契約：`gh search issues`（relevance、`--state all` 全語料）主 + `gh issue list --search` fallback。**引用 idd-find SKILL 的 backend 段落，不內嵌分歧副本**（同 #137 反 typo-drift 紀律）。ask 疊加自己的第二步：對 top-N hits `gh issue view --json body,comments` 抓全文。跨措辭限制同界（詞法檢索），輸出尾端同樣揭露。
+
+## D3 — Grounded 回答契約（spectra-ask 規矩移植）
+
+1. 首行 blockquote 引用使用者原問題
+2. 每個 claim 附來源（`#N` + comment 錨點或區段名）；**語料裡沒有的不寫**（查無 → 誠實說查無 + 建議換 phrasing 或 `/idd-find` 自行翻）
+3. **Source priority**：closed-with-PR > open > orphaned comment。衝突時取高優先源，並標注低優先源的分歧（「#A（closed）採 X；#B（open，進行中）傾向 Y」）
+4. 結尾 `### Referenced Issues`：`#N (title) — URL`，只列實際引用的
+
+## D4 — Decide-to-search gate（不是每個輸入都搜）
+
+greeting / 純 meta-tool 問題（「idd-ask 怎麼用」）→ 不搜，直接答或引導。問題長得像 bug report → **不觸發 diagnose**，回答已知歷史後附一行「要立案 → `/idd-issue`」。無 question 且對話 context 可推 → 確認後搜；推不出 → 要求明確問題。
+
+## D5 — #140 boilerplate checklist 逐項（第 4 員首戰）
+
+Step 0 TaskCreate bootstrap ✓；config-protocol（`--repo` override；group 搜尋 = `--target group:<label>` 依 issue 需求，v1 先單 repo + 註記 group 為 residue）✓；unattended fallback（無互動 gate；decide-to-search 的「確認後搜」在 unattended 下改直接搜 + audit line）✓；bounded output（top-N=5、`--limit` 上限 10；讀全文的 token 成本是 ask 的本質成本，明文揭露）✓；read-only allowed-tools ✓；drift-guard ✓；CLAUDE.md + usecase-routing ✓。`references/surfacing-primitives.md` 成員表 +1（第 3 題弱命中入註記）。
+
+## Alternatives considered
+
+- **塞進 idd-find 當 `--answer` flag**：否 — I/O 形狀不同（hits vs 合成答案）、token 成本量級不同，正是 #139 Option A 拒絕合併的同一論證
+- **建 local cache / embedding index**：否 — 基建成本不符 surfacing primitive 輕量定位；誠實邊界與 find 一致
+- **先只寫 reference 文件（第 3 題弱）**：否 — spectra-ask 同構先例證明 ask 類 skill 的消費者是人，等 skill 消費者出現才開會讓「還原 decision rationale」繼續無入口
diff --git a/openspec/changes/idd-ask-skill/proposal.md b/openspec/changes/idd-ask-skill/proposal.md
new file mode 100644
index 0000000..54bb0f7
--- /dev/null
+++ b/openspec/changes/idd-ask-skill/proposal.md
@@ -0,0 +1,34 @@
+# Proposal: idd-ask-skill
+
+## Why
+
+IDD 的知識庫（issues + comments + linked PRs：diagnoses、decisions、closing summaries）沒有 grounded 問答入口。查歷史只能手動 `gh issue list` + 逐一 view — 三個月後想還原「當時為什麼這樣決定」，AI 沒有 skill 層路徑（#72，鏡像 `/spectra-ask` 的空缺）。`/idd-find`（#139）解了「在哪裡」（query → ranked hits），沒解「為什麼」（question → 有引用的合成答案）。
+
+## What Changes
+
+1. **新 skill `/idd-ask <question>`**：surfacing family **第 4 員** — 自然語言問題 → decide-to-search gate → retrieval（**delegate `idd-find` 的 search backend**，不重造）→ 讀取 top-N 命中 issue 全文（body + comments）→ grounded 回答（首行 blockquote 原問題、每個 claim 附 issue/comment 引用、不腦補）→ `### Referenced Issues` 區段。
+2. **Source priority**（類比 spectra-ask）：closed-with-PR issue > open issue > orphaned comment — 已關已 ship 是 ground truth，open 標注「進行中、可能會變」。
+3. **Read-only 鐵律**：不 create / edit / comment / close；問題長得像 bug report 也**不**觸發 diagnose（引導語提示 `/idd-issue`）。
+4. **#140 增員程序首次實戰**：三題判準記錄 + boilerplate checklist 逐項 + `references/surfacing-primitives.md` 成員表同步（canonical 更新）。
+5. **可發現性**：plugin CLAUDE.md 表 + usecase-routing 情境列；drift-guard suite `scripts/tests/idd-ask/`。
+
+## 增員判準（#140 三題，誠實記錄）
+
+1. **I/O 形狀與現任三員不同？** ✓ — list（filters→triage 表）/ clarify（內文→標注）/ find（query→ranked hits）/ **ask（question→合成答案+引用）**
+2. **唯讀？** ✓（issue 明訂設計約束）
+3. **有 delegate 消費者？** **弱命中** — 主要消費者是人（同 spectra-ask）；潛在 skill 消費者（diagnose 查歷史 rationale）未接線。per family doc 此題弱時「先當 reference 文件」是選項，但本案有使用者裁決 + spectra-ask 同構先例（ask 類 skill 的消費者本來就是人），judgment：開 skill、把第 3 題弱命中記入 family doc 成員表註記。
+
+## Non-Goals
+
+- Embedding 語意搜尋（#72 Residue — `gh search` 詞法檢索是誠實邊界，與 idd-find 同界）
+- Local cache / index 建置（retrieval 成本用 top-N + limit 控，不建基建）
+- 觸發任何 lifecycle step（ask 是純問答）
+
+## Impact
+
+- Affected specs: `idd-ask`（ADDED，新 capability）
+- Affected code: 新 `skills/idd-ask/SKILL.md`、`references/surfacing-primitives.md`（成員表 +1）、plugin `CLAUDE.md`、`references/usecase-routing.md`、新 suite
+
+## Refs
+
+Issue #72（Spectra opt-out → propose；「鏡像 /spectra-ask」定案）；family 契約 #140；retrieval backend 先例 #139
diff --git a/openspec/changes/idd-ask-skill/specs/idd-ask/spec.md b/openspec/changes/idd-ask-skill/specs/idd-ask/spec.md
new file mode 100644
index 0000000..2dd5cbd
--- /dev/null
+++ b/openspec/changes/idd-ask-skill/specs/idd-ask/spec.md
@@ -0,0 +1,35 @@
+## ADDED Requirements
+
+### Requirement: Grounded question-answering over the issue corpus
+
+`/idd-ask <question>` SHALL answer natural-language questions grounded exclusively in the target repo's issue corpus (issues, comments, linked PRs, open and closed): it SHALL retrieve candidates via the `idd-find` search backend contract (lexical relevance, full corpus), read the top-N hits' full body and comments (N default 5, `--limit` capped at 10), and compose an answer in which the first line blockquotes the user's question and every claim carries an issue/comment citation. Content absent from the corpus SHALL NOT be asserted — an empty or insufficient retrieval SHALL be reported honestly with a suggestion to rephrase or fall through to `/idd-find`. The answer SHALL end with a `### Referenced Issues` section listing only the actually-cited issues. Source priority SHALL be closed-with-PR > open > orphaned comment, with conflicts surfaced rather than silently resolved.
+
+#### Scenario: decision-rationale question gets a cited answer
+
+- **WHEN** `/idd-ask "為什麼 idd-verify 的 DA 改成 sequenced spawn？"` runs against a repo whose closed issue #130 records that decision
+- **THEN** the answer opens by blockquoting the question, cites #130's diagnosis/closing content for each claim, and lists #130 under `### Referenced Issues`
+
+#### Scenario: corpus silence is reported, not filled
+
+- **WHEN** the question matches nothing in the corpus
+- **THEN** the skill says so, suggests rephrasing or `/idd-find`, and fabricates no answer
+
+#### Scenario: open-vs-closed conflict is surfaced
+
+- **GIVEN** a closed-with-PR issue records decision X and an open issue is trending toward Y
+- **WHEN** both are retrieved for the same question
+- **THEN** the answer leads with X (higher priority) and explicitly notes the open issue's in-progress divergence
+
+### Requirement: Surfacing-only fourth member obligations
+
+`/idd-ask` SHALL be read-only (no issue create / edit / comment / close; a bug-report-shaped question SHALL NOT trigger any lifecycle step — the answer MAY append a one-line pointer to `/idd-issue`), SHALL follow the surfacing-primitives family boilerplate (Step 0 bootstrap, config-protocol resolution with `--repo`, unattended fallback that searches without the confirm gate and records an audit line, bounded output), and SHALL be registered in the family's canonical member table in `references/surfacing-primitives.md`.
+
+#### Scenario: bug-shaped question stays read-only
+
+- **WHEN** `/idd-ask "idd-edit 是不是會把 body 洗掉？"` runs
+- **THEN** the skill answers from history (e.g., the #150 record) without creating or modifying anything, and at most appends a `/idd-issue` pointer
+
+#### Scenario: family table registers the fourth member
+
+- **WHEN** `references/surfacing-primitives.md` is inspected
+- **THEN** its member table lists idd-ask alongside idd-list / idd-clarify / idd-find with its distinct I/O shape
diff --git a/openspec/changes/idd-ask-skill/tasks.md b/openspec/changes/idd-ask-skill/tasks.md
new file mode 100644
index 0000000..09752e4
--- /dev/null
+++ b/openspec/changes/idd-ask-skill/tasks.md
@@ -0,0 +1,9 @@
+## 1. Tests first (RED)
+
+- [x] 1.1 (Req: Grounded question-answering over the issue corpus; Req: Surfacing-only fourth member obligations) New drift-guard suite plugins/issue-driven-dev/scripts/tests/idd-ask/test.sh: SKILL 存在 + read-only 禁令 + blockquote 原問題 + claim 必附引用 + source priority + `### Referenced Issues` + top-N/limit 界限 + delegate idd-find backend 引用 + 不觸發 diagnose + family 文件成員表含 idd-ask + CLAUDE.md / usecase-routing 可發現性。Run: RED。
+
+## 2. Implementation (GREEN)
+
+- [x] 2.1 (Design D1 — 與 find 的分工; D2 — retrieval delegate idd-find backend; D3 — grounded 回答契約; D4 — decide-to-search gate; D5 — #140 boilerplate checklist 逐項) New skills/idd-ask/SKILL.md（frontmatter read-only allowed-tools、Step 0 bootstrap、gate、retrieval delegate、全文讀取 top-N、回答契約、source priority、unattended 行為、`--repo`/`--limit`、分工表）。
+- [x] 2.2 references/surfacing-primitives.md 成員表 +1（第 3 題弱命中註記）；plugin CLAUDE.md 輔助表加 idd-ask 列；references/usecase-routing.md 加情境列。
+- [x] 2.3 Verify: suite GREEN; full plugin sweep 0 fail; spectra validate clean。
diff --git a/plugins/issue-driven-dev/CLAUDE.md b/plugins/issue-driven-dev/CLAUDE.md
index f885f1e..67b1bfe 100644
--- a/plugins/issue-driven-dev/CLAUDE.md
+++ b/plugins/issue-driven-dev/CLAUDE.md
@@ -51,6 +51,7 @@ skill source tree；既有 `SKILL.md` 可以繼續使用 Claude-native tool cont
 | `idd-update` | Issue body 過時，要讀完所有 comments 才知道現狀 | 同步 body Current Status 區塊 |
 | `idd-list` | 不知道有什麼要做、漏掉卡 verify 的 issue | 列出 open issues 含 IDD phase + 建議 next action |
 | `idd-find` | 重複 diagnose 已解過的問題；忘記舊 fix 在哪 | 語意查找 open+closed 全語料（GitHub relevance + phase/PR overlay）；surfacing-only、read-only（v2.97.0+，#139）|
+| `idd-ask` | 三個月後沒人記得當時為什麼；AI 憑記憶腦補歷史 | issue 知識庫 grounded 問答（top-N 全文 + claim 必附引用 + source priority；鏡像 /spectra-ask）；surfacing-only、read-only（v2.99+，#72）|
 | `idd-report` | 進度不透明，stakeholder 看不到現況 | 產出進度報告到 GitHub Discussions |
 | `idd-comment` | 非流程性決定 / 外部 context 散落在 chat | Template-guided comment（decision/note/question/correction/link/errata）|
 | `idd-edit` | 手動 `gh api PATCH` 容易字串 escape 誤覆蓋 | 編輯既有 comment（append/replace/prepend-note 三種 mode）|
diff --git a/plugins/issue-driven-dev/references/surfacing-primitives.md b/plugins/issue-driven-dev/references/surfacing-primitives.md
index 3b10135..5ec726c 100644
--- a/plugins/issue-driven-dev/references/surfacing-primitives.md
+++ b/plugins/issue-driven-dev/references/surfacing-primitives.md
@@ -8,9 +8,10 @@ IDD 的 skill 分兩類：**lifecycle skills**（issue → diagnose → implemen
 |--------|-----|-----------|
 | `/idd-list`（v2.51+） | structural triage | 「現在有什麼、在哪個 phase、哪個 PR」 |
 | `/idd-clarify`（#135, v2.72+） | terminology / semantic accuracy | 「這個詞用得準不準、誰需要釐清」 |
-| `/idd-find`（#139, v2.97+） | semantic lookup | 「之前是不是處理過類似的問題」 |
+| `/idd-find`（#139, v2.97+） | semantic lookup | 「之前是不是處理過類似的問題、在哪」 |
+| `/idd-ask`（#72, v2.99+） | grounded QA | 「當時為什麼這樣決定 / X 怎麼運作」→ **合成答案**＋引用（鏡像 /spectra-ask） |
 
-三員互補、零重疊：list 吃 filters、find 吃 free-text query、clarify 吃 issue 內文語意 — 輸入/輸出形狀不同是「該開新 skill 而非塞 flag」的判準（#139 Option A 裁決的一般化）。
+四員互補、零重疊：list 吃 filters、find 吃 free-text query → ranked hits、ask 吃 question → 合成答案、clarify 吃 issue 內文語意 — 輸入/輸出形狀不同是「該開新 skill 而非塞 flag」的判準（#139 Option A 裁決的一般化）。ask 的 retrieval delegate find 的 backend（本檔「lifecycle 不重造唯讀查詢」鐵律同樣適用於 primitive 之間）。增員三題的誠實記錄（#72）：第 3 題（delegate 消費者）**弱命中** — ask 類 skill 的消費者本來就是人（spectra-ask 同構先例），以此 judgment 開員；若未來第 3 題弱的候選無同構先例，先當 reference 文件。
 
 ## D12 軸：Surfacing vs Lifecycle
 
diff --git a/plugins/issue-driven-dev/references/usecase-routing.md b/plugins/issue-driven-dev/references/usecase-routing.md
index 52bcb35..ce92a1d 100644
--- a/plugins/issue-driven-dev/references/usecase-routing.md
+++ b/plugins/issue-driven-dev/references/usecase-routing.md
@@ -68,6 +68,7 @@
 | **27** | N 個 unrelated open issues 想一次解（無 emergent 關係，backlog drain）| **`idd-all #A #B #C`**（v2.83.0+ multi-issue batch mode）— conflict-class-**ordered sequential** drain：依 `### Conflict Class` 排序（`E`/`D` 先、同資源 `B`/`C` 相鄰序列化、同檔成組、`A` 不拘），逐一跑完整 idd-all pipeline | （無 — 每 issue 讀 `### Conflict Class`，缺則預設 `D_diagnose_first` surfaced）；**sequential**（真並發 stateful lane = deferred，見 worktree-isolation Case A）；`A` 可選 worktree 隔離供事後手動並行；stop at verified | [parallel-orchestration.md](parallel-orchestration.md)（取代先前「無內建 bulk-solve」註記；conflict-class taxonomy = 並行安全契約；參 parked [#37](https://github.com/PsychQuant/issue-driven-development/issues/37)）|
 | **28** | 使用者回報以 **GitHub Discussion** 形式抵達（Q&A / Ideas），要納入 IDD intake | `idd-list --discussions`（surface actionable）→ 人判斷 → `idd-issue --from-discussion <url>`（seed + provenance + draft-and-confirm 回文）| `--discussions` / `--from-discussion` | [discussions-intake.md](discussions-intake.md) |
 | **29** | 「之前是不是處理過類似的問題？」— 建案前查重、找舊案考古、引用過往結案紀錄（v2.97.0+，#139）| `idd-find "<free-text query>"`（open+closed 全語料，GitHub relevance 排序 + phase / PR overlay；surfacing-only、read-only）| `--repo` / `--limit N`（filter flags 拒收 → 導流 `idd-list`）| [surfacing-primitives.md](surfacing-primitives.md) |
+| **30** | 「當時為什麼這樣決定？」「X 怎麼運作？」— 還原 decision rationale、查歷史脈絡、不想自己翻 issue（v2.99+，#72）| `idd-ask "<自然語言問題>"`（retrieval delegate idd-find backend → top-N 全文 → grounded 合成答案：claim 必附引用 + source priority + `### Referenced Issues`；surfacing-only、read-only、不觸發 diagnose）| `--repo` / `--limit N`（top-N 上限 10）| [surfacing-primitives.md](surfacing-primitives.md) |
 
 > **Chain-solve vs bulk-solve semantic 差異**(per #49 cross-link):
 > - **`/idd-all-chain #N`**(v2.55.0+, row 25, single-root):**hot-chain from active work** — 1 root + auto-emergent spawn(sister bug / verify follow-up / mid-plan tangential / sister concern detected via spawn manifest)。Bounded by hard caps per-root depth=3、global max-issues=10 (v2.60.0+, was 2/5)。Reviewer mental model:「this thread is complete」。
diff --git a/plugins/issue-driven-dev/scripts/tests/idd-ask/test.sh b/plugins/issue-driven-dev/scripts/tests/idd-ask/test.sh
new file mode 100644
index 0000000..c18d0b0
--- /dev/null
+++ b/plugins/issue-driven-dev/scripts/tests/idd-ask/test.sh
@@ -0,0 +1,53 @@
+#!/usr/bin/env bash
+# test.sh — drift-guard for #72 /idd-ask (grounded QA over the issue corpus).
+#
+# WHY A CONTENT DRIFT-GUARD: the skill is prose. The falsifiable equivalent of
+# "answers stay grounded and the skill stays a surfacing primitive" is
+# asserting the SKILL carries the grounding contract verbatim (blockquote the
+# question, cite every claim, source priority, Referenced Issues, honest
+# silence), the family obligations (read-only, no-diagnose-trigger, bounded
+# top-N, idd-find backend delegation — never a diverging retrieval copy), and
+# the three discoverability surfaces. A missing citation-contract line is
+# exactly how grounded QA silently degrades into hallucinated summaries.
+#
+# Usage: bash test.sh   (exit 0 = all pass, 1 = any fail)
+
+set -u
+
+HERE="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+PLUGIN_ROOT="$HERE/../../.."
+SKILL="$PLUGIN_ROOT/skills/idd-ask/SKILL.md"
+FAMILY="$PLUGIN_ROOT/references/surfacing-primitives.md"
+PCLAUDE="$PLUGIN_ROOT/CLAUDE.md"
+ROUTING="$PLUGIN_ROOT/references/usecase-routing.md"
+
+HELPERS="$HERE/../../lib/assert-helpers.sh"
+[ -f "$HELPERS" ] || { echo "✗ missing $HELPERS — cannot run suite" >&2; exit 1; }
+. "$HELPERS"
+
+# ── skill exists with the grounding contract ──
+assert_file_exists "idd-ask SKILL.md exists" "$SKILL"
+assert_output_grep "skill: blockquote the user's question"      "blockquote 引用使用者原問題" "$SKILL"
+assert_output_grep "skill: every claim carries a citation"      "claim 必附引用"        "$SKILL"
+assert_output_grep "skill: source priority order"               "closed-with-PR > open > orphaned comment" "$SKILL"
+assert_output_grep "skill: Referenced Issues section"           "### Referenced Issues" "$SKILL"
+assert_output_grep "skill: honest silence on corpus miss"       "查無"                  "$SKILL"
+assert_output_grep "skill: conflicts surfaced not resolved"     "分歧"                  "$SKILL"
+
+# ── family obligations ──
+assert_output_grep "skill: read-only prohibition"               "不 mutate 任何 state"   "$SKILL"
+assert_output_grep "skill: bug-shaped question never triggers diagnose" "不觸發"        "$SKILL"
+assert_output_grep "skill: bounded top-N"                       "top-N"                 "$SKILL"
+assert_output_grep "skill: delegates idd-find backend (no diverging copy)" '`idd-find` 的 search backend' "$SKILL"
+assert_output_grep "skill: family membership"                   "surfacing-only"        "$SKILL"
+assert_output_grep "skill: cites family canonical"              "references/surfacing-primitives.md" "$SKILL"
+
+# ── family canonical registers the 4th member ──
+assert_output_grep "family: member table lists idd-ask"         "idd-ask"               "$FAMILY"
+assert_output_grep "family: ask's distinct I/O shape recorded"  "合成答案"               "$FAMILY"
+
+# ── discoverability ──
+assert_output_grep "plugin CLAUDE.md lists idd-ask"             "idd-ask"               "$PCLAUDE"
+assert_output_grep "usecase-routing has an ask scenario"        "idd-ask"               "$ROUTING"
+
+print_summary "idd-ask"
diff --git a/plugins/issue-driven-dev/skills/idd-ask/SKILL.md b/plugins/issue-driven-dev/skills/idd-ask/SKILL.md
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+---
+name: idd-ask
+description: |
+  對 issue 知識庫（issues + comments + linked PRs，open+closed）做 grounded 問答 — 鏡像 /spectra-ask。
+  「當時為什麼這樣決定？」「X 是怎麼運作的？」→ 讀 top-N 命中全文、合成有引用的答案。
+  Use when: 想還原 decision rationale、查歷史脈絡、不想自己翻 issue。
+  防止的失敗：三個月後沒人記得當時為什麼；AI 憑記憶腦補歷史。
+argument-hint: "<自然語言問題> [--repo owner/repo] [--limit N]"
+allowed-tools:
+  - Bash(gh search:*)
+  - Bash(gh issue list:*)
+  - Bash(gh issue view:*)
+  - Bash(gh pr view:*)
+  - Read
+  - Grep
+  - TaskCreate
+  - TaskUpdate
+---
+
+# /idd-ask — issue 知識庫問答（surfacing-only）
+
+自然語言問題 → 檢索 issue 語料 → 讀 top-N 命中**全文**（body + comments）→ **grounded 合成答案**（每個 claim 附引用）。回答「為什麼 / 怎麼運作」— 不是 lookup（那是 `idd-find`）、不是 triage（那是 `idd-list`）。
+
+## 核心原則
+
+> **語料裡沒有的不寫。** 答案只引用 issue / comment 內容，不腦補、不憑訓練記憶補歷史。查無就誠實說查無。
+>
+> **Surfacing-only 鐵律**：本 skill **不 mutate 任何 state** — 禁止 `gh issue create` / `edit` / `close` / `comment` / label 操作。family 共同契約見 [`references/surfacing-primitives.md`](../../references/surfacing-primitives.md)。
+
+## 與 find 的分工（防定位稀釋）
+
+| | `idd-find` | `idd-ask` |
+|---|---|---|
+| 問題 | 「有沒有處理過類似 X、在哪」 | 「當時為什麼這樣決定 / X 怎麼運作」 |
+| 輸出 | ranked hits（人自己讀） | **合成答案**＋引用（AI 讀完答） |
+| 讀取深度 | metadata + overlay | top-N 命中**全文** |
+| Token 成本 | 低 | 高（有界：top-N 預設 5，`--limit` 上限 10） |
+
+答案結尾必附 `### Referenced Issues` — 不滿意合成答案時人可 fall through 自行閱讀（ask → find 互補鏈）。
+
+## Configuration
+
+按 [config-protocol](../../references/config-protocol.md) 解析 target repo（`--repo` override → walk-up → git remote fallback）。read-only skill，只用 path / git predicates。group 搜尋（`--target group:<label>`）為 residue，v1 單 repo。
+
+## Execution
+
+### Step 0: Bootstrap Stage Task List（強制）
+
+```
+TaskCreate(name="parse_and_gate", description="解析問題 + --repo/--limit；decide-to-search gate（greeting/meta 不搜；無問題 → 從對話 context 推、推不出要求明確問題）")
+TaskCreate(name="retrieve", description="idd-find backend 檢索（gh search issues 主 + gh issue list --search fallback，--state all 全語料）→ top-N 候選")
+TaskCreate(name="read_full", description="對 top-N 命中 gh issue view --json body,comments 抓全文；linked PR 視需要 gh pr view")
+TaskCreate(name="compose_answer", description="grounded 合成：blockquote 原問題 + claim 必附引用 + source priority + 分歧 surface + ### Referenced Issues")
+```
+
+完成每一步立即 `TaskUpdate → completed`。**靜默完成 = 違規**。
+
+### Step 1: Parse + decide-to-search gate
+
+- 問題 = 去 flags 後的 free text；`--limit N`（top-N，預設 5、**上限 10** — 讀全文是 ask 的本質 token 成本，界限明文）
+- **不是每個輸入都搜**：greeting / 純 meta 問題（「idd-ask 怎麼用」）→ 直接答，不檢索
+- 無問題但對話 context 可推 → 向使用者確認推得的問題後搜；推不出 → 要求明確問題
+- **問題長得像 bug report → 不觸發 `/idd-diagnose`、不建案** — 照常回答已知歷史，答案尾端至多附一行「要立案 → `/idd-issue`」
+- Unattended mode：確認 gate 跳過、直接以推得的問題搜 + audit line（`[idd-ask: inferred question "<q>" under unattended mode]`）
+
+### Step 2: Retrieval（delegate，不重造）
+
+沿用 **`idd-find` 的 search backend** 契約（[`skills/idd-find/SKILL.md`](../idd-find/SKILL.md) Step 2：`gh search issues` relevance 主 + `gh issue list --search` fallback，`--state all` 全語料）— **引用該段，不內嵌分歧副本**。ask 疊加第二步：
+
+```bash
+# top-N 命中抓全文（這是 ask 與 find 的成本分界）
+gh issue view "$N" --repo "$GITHUB_REPO" --json number,title,state,body,comments,url
+```
+
+跨措辭限制與 find 同界（詞法檢索）；輸出尾端同樣揭露。
+
+### Step 3: Grounded 合成（spectra-ask 規矩移植）
+
+1. **首行 blockquote 引用使用者原問題**
+2. **claim 必附引用** — 每個論斷標 `#N`（必要時加 comment 錨點 / 區段名，如「#130 Diagnosis」）。**查無**或語料不足 → 誠實說明 + 建議換 phrasing 或 `/idd-find` 自行翻，不編造
+3. **Source priority**：**closed-with-PR > open > orphaned comment** — 已關已 ship 是 ground truth；open 標注「進行中、可能會變」。同題衝突時取高優先源並 surface **分歧**（「#A（closed）採 X；#B（open）傾向 Y」），不靜默擇一
+4. 結尾 **`### Referenced Issues`**：`#N (title) — URL`，**只列實際引用的**
+
+### 輸出範例
+
+```
+> 為什麼 idd-verify 的 DA 改成 sequenced spawn？
+
+#130（closed）記錄的根因是 polling window 的 socket-crash：DA 用 polling 等其他 4 份
+findings 檔時 …（略）… 因此 v2.92 起 coordinator 在 4 檔就緒後才序列 spawn DA（#130 Closing Summary）。
+
+### Referenced Issues
+- #130 (idd-verify DA sequenced-spawn) — https://github.com/…/issues/130
+```
+
+## 鐵律
+
+- **Read-only** — 問答結束於輸出；任何 state 變更走對應 lifecycle skill
+- **不腦補** — 訓練記憶不是語料；只有 retrieval 讀到的才可引用
+- **查無是合法輸出** — 語料沉默 ≠ 回答失敗