docs: add add-tasks skill and link it from add-contest-table-provider

.agents/skills/add-contest-table-provider/SKILL.md

@@ -8,6 +8,6 @@ Add a new contest table provider for: $ARGUMENTS
 
 > When in doubt at any step, use AskUserQuestion before proceeding.
 
-0. **Seed check** — grep `prisma/tasks.ts` for the contest_id(s); report count + task_ids; if absent or incomplete, ask the user to paste the missing rows (source: `https://kenkoooo.com/atcoder/resources/problems.json`). Do not fetch it yourself: atcoder.jp is unreachable, and WebFetch truncates problems.json, so a miss there is not evidence of absence
+0. **Seed check** — grep `prisma/tasks.ts` for the contest_id(s); report count + task_ids; if absent or incomplete, collect them per `add-tasks` [§Collect rows](../add-tasks/instructions.md) (never fetch problems.json yourself)
 1. **Gather requirements** — infer the implementation pattern; confirm per [instructions.md §Requirements](instructions.md)
 2. **Implement** — follow [instructions.md](instructions.md) for the confirmed pattern across 5 layers (TDD)

.agents/skills/add-contest-table-provider/instructions.md

@@ -49,7 +49,7 @@ Step 0 (seed check) is already done. Confirm the following before touching code:
 
 ### Implement
 
-- [ ] `CONTEST_TYPES_BY_ID` or `CLASSIFICATION_RULES` in `src/lib/contests/utils/classification.ts`
+- [ ] `CONTEST_TYPES_BY_ID` or `CLASSIFICATION_RULES` in `src/lib/contests/utils/classification.ts`, or the maps in `prefixes.ts` (exact vs prefix match: see `add-tasks` [§Classify](../add-tasks/instructions.md))
 - [ ] `contestTypePriorities` in `src/lib/contests/utils/priority.ts`
   - After priority insertion, all later entries shift +1 → **update JSDoc numeric ranges** (4 category names are immutable)
   - Fix hardcoded priority-diff expected values in `src/test/lib/utils/task.test.ts` only when they involve a shifted entry (±1 each)

.agents/skills/add-tasks/SKILL.md

@@ -0,0 +1,15 @@
+---
+name: add-tasks
+description: Add tasks of contests that an existing ContestType already covers to prisma/tasks.ts, with classification tests first. Use for "問題を追加しましょう" issues. Hands off to add-contest-table-provider when a new ContestType or provider is needed.
+argument-hint: '<contest_id> [<contest_id> ...]'
+---
+
+Add tasks for: $ARGUMENTS
+
+> When in doubt at any step, use AskUserQuestion before proceeding.
+
+1. **Classify** — decide the ContestType and prefix group per [instructions.md §Classify](instructions.md); a new ContestType or provider → stop and switch to `add-contest-table-provider`
+2. **Collect rows** — grep `prisma/tasks.ts`; ask the user to paste missing rows from problems.json; never fetch it yourself
+3. **Tests first** — add fixture cases per [instructions.md §Tests](instructions.md); confirm **RED**
+4. **Implement** — add the contest name to `prefixes.ts` → **GREEN**; insert rows per [instructions.md §Insert](instructions.md)
+5. **Verify** — `pnpm format` / `pnpm lint` / `pnpm check` / `pnpm test:unit` / `git diff --check`

.agents/skills/add-tasks/instructions.md

@@ -0,0 +1,35 @@
+# Add Tasks — Checklist
+
+---
+
+## Classify
+
+- Groups in `src/lib/contests/utils/prefixes.ts` match differently:
+  - `ABC_LIKE` / `ARC_LIKE`: exact match — a sequel (e.g. `diverta2019-2` next to `diverta2019`) needs its own key
+  - `AGC_LIKE` / `ATCODER_UNIVERSITIES` / `ATCODER_OTHERS`: prefix match — check an existing key does not already swallow the new id with the wrong type
+  - AOJ: regex (`regexForJag`, `regexForAojUniversity`) — no map edit if the id already matches; otherwise widening the regex also affects `getContestNameLabel` and `AojGenerator.canHandle`, so switch to `add-contest-table-provider`
+- Rules are first-match-wins (`CLASSIFICATION_RULES` in `classification.ts`); confirm no earlier rule (`abc\d{3}`, `past`, `joi`, ...) catches the id
+- Use the official contest name; Japanese if one exists
+
+## Collect rows
+
+- Source: `https://kenkoooo.com/atcoder/resources/problems.json`
+- atcoder.jp is unreachable and WebFetch truncates problems.json, so a miss there is not evidence of absence — ask the user to paste the rows
+- Use `id` / `problem_index` / `name` / `title` verbatim; do not derive `id` from contest_id
+
+## Tests
+
+Add cases to the fixtures the contest type exercises (all under `src/lib/contests/fixtures/` unless noted):
+
+- [ ] `contest_type.ts` — always
+- [ ] `contest_name_labels.ts` — when the type has a label generator (OTHERS, UNIVERSITY, AOJ\_\*); ABC_LIKE / ARC_LIKE fall back to the uppercased id, so skip
+- [ ] `contest_name_and_task_index.ts` — AOJ types
+- [ ] `src/test/lib/utils/test_cases/task_url.ts` — AOJ types
+- [ ] `pnpm test:unit src/lib/contests/` — **RED**
+
+## Insert
+
+- [ ] Place rows after the existing block of the same group in `prisma/tasks.ts`
+- [ ] Contests newest first; tasks within a contest in descending index (F → A)
+- [ ] For more than a few rows, generate the entries with a script instead of hand-typing
+- [ ] `grep -c` the new ids to confirm the count

.claude/skills/add-tasks

@@ -0,0 +1 @@
+../../.agents/skills/add-tasks

AGENTS.md

@@ -54,12 +54,13 @@ Before planning or changing a matching path, read the corresponding document und
 
 Use project-specific workflows from `.agents/skills/` when a task matches a skill description. Each `.agents/skills/<name>/instructions.md` is a plain Markdown checklist — read it directly when doing that task by hand, not only when an agent loads it automatically.
 
-| Skill                        | Purpose                                          |
-| ---------------------------- | ------------------------------------------------ |
-| `add-contest-table-provider` | Add a ContestType / ContestTableProvider via TDD |
-| `dep-upgrade`                | Analyze and execute a major dependency upgrade   |
-| `extract-approach`           | Extract learnings from a just-solved problem     |
-| `verify-test-strength`       | Verify test detection power via mutation testing |
+| Skill                        | Purpose                                               |
+| ---------------------------- | ----------------------------------------------------- |
+| `add-contest-table-provider` | Add a ContestType / ContestTableProvider via TDD      |
+| `add-tasks`                  | Add tasks of existing ContestTypes to prisma/tasks.ts |
+| `dep-upgrade`                | Analyze and execute a major dependency upgrade        |
+| `extract-approach`           | Extract learnings from a just-solved problem          |
+| `verify-test-strength`       | Verify test detection power via mutation testing      |
 
 Add a row here whenever a skill is added, renamed, or removed.
 

docs/guides/how-to-add-contest-table-provider.md

@@ -7,7 +7,7 @@
 ## 事前確認
 
 - [ ] `ContestType`（`src/lib/contests/types/contest.ts`）— 既存で対応できるか？複数 contest_id を統一表示するなら複合型
-- [ ] `classifyContest()`（`src/lib/contests/utils/classification.ts`）— 新 contest_id に正しい ContestType を返すか
+- [ ] `classifyContest()`（`src/lib/contests/utils/classification.ts`）— 新 contest_id に正しい ContestType を返すか。`prefixes.ts` の `ABC_LIKE` / `ARC_LIKE` は完全一致、他グループは前方一致なので、続編（例: `diverta2019-2`）は完全一致グループでは個別にキーを追加する
 - [ ] `prisma/tasks.ts` にデータが存在するか（複合型は `prisma/contest_task_pairs.ts` も）
 - [ ] 実装パターン判定（後述4パターン）
 - [ ] JOI: 2026 年より `joi{YYYY}ho` → `joi{YYYY}sf`。regex は `(ho|sf)` 対応済み