name: ref-downloader
description: >
  Use when the user asks to batch-download academic PDFs with
  ref-downloader — either ALL references of one paper (Mode A: DOI or
  PDF input), OR a custom batch of papers (Mode B: DOI/title/arXiv-PMID
  list, or abstract query like "Author X's recent papers"). Not for
  one-off PDFs, paper search, or Zotero import.

Ref Downloader — Agent Runbook

Slim entry for agent mode. The full 8-step manual runbook with code snippets for Mode A debug + PUBLISHER_MAP extension procedure lives in references/agent-runbook.md. Human users see ../../README.md.

<SKILL_DIR> = this folder (skills/ref-downloader in the source repo, or wherever the user copied this skill — e.g. ~/.claude/skills/ref-downloader/). Python scripts live in <SKILL_DIR>/scripts/; config files (config.example.toml, config.local.toml) live at <SKILL_DIR>/.

Mode router

This skill handles two flows. Pick before running.

• Mode A — Reference-list download (original use case). User provides ONE paper (DOI or local PDF) and wants "all of its references". Pipeline: extract_refs.py → validate_refs.py → download_refs.py.

• Mode B — Custom batch download. User provides their own batch of papers — DOIs, paper titles, non-DOI identifiers (arXiv / PMID / Semantic Scholar IDs), OR an abstract query ("Smith 在 Google Scholar 上的文章" / "Nature Energy 2023 papers"). The agent resolves whatever was given to DOIs, then runs validate_refs.py → download_refs.py directly. Skip the wrapper — run_ref_downloader.py assumes a parent DOI and will fail.

Both modes share install, config, per-publisher strategies, failure modes, output layout, and the CloakBrowser opt-in backend.

Trigger family

User input shape	Mode	Sub-flow
One DOI/PDF + "all refs of" / "全部参考文献" / "把这篇引用都下了"	A	—
≥2 DOIs in input (any wrapping: bare / {} / https://doi.org/… / dx.doi.org/…; ASCII or full-width slashes)	B	B.1 (after canonicalize)
Non-DOI IDs only: arXiv: / PMID: / S2: / corpusId:	B	B.0 normalize → B.1
Title list ("下载这几篇：title1, title2, …")	B	B.2
Abstract query (author / topic / journal+year / "Google Scholar 上 …")	B	B.3
Mixed (DOIs + titles + IDs + queries)	B	run each, merge
Single DOI without "of refs" qualifier	B	B.1 single-item
Title + author + year for ONE paper ("Smith 2024 Nature paper on X")	B	B.2 (specific paper, lookup)
Open-ended query for a corpus ("Smith 2024 之后所有的 Nature 文章")	B	B.3 (discovery)
Insufficient resolvable content ("上次给你的那 5 篇" / pure pronouns)	—	Ask user to repaste / attach file; do NOT guess
Genuinely ambiguous A vs B	—	ask user

Key disambiguators:

• "refs OF a paper" (Mode A) vs "these papers themselves" (Mode B).
• Identifies a specific paper (B.2) vs describes a set to discover (B.3). If user names a specific paper with enough metadata to uniquely identify it (title + author + year), it's B.2 (lookup exact); if they describe a class of papers ("all Smith's 2024 Nature papers"), it's B.3 (discover then filter).

Mode A — Reference-list download

When to invoke

Trigger phrases:

• "帮我下载 [paper / DOI] 的参考文献" / "批量下载引用文献" / "把这篇论文的所有引用下载下来"
• "Download all refs of [paper / DOI]" / "Batch-download every reference"
• User provides a DOI (10.x/y form) or local PDF path and asks for "all references" / "全部参考文献"

Don't invoke for:

• Downloading one arbitrary PDF (not a reference list) → user wants one paper itself, route to Mode B as a single-item B.1
• Generic web scraping
• Paper search / Zotero import — different tools

Primary entry

python "<SKILL_DIR>/scripts/run_ref_downloader.py" <DOI_OR_PDF_PATH>

The wrapper handles DOI resolution (Zotero → fitz fallback), output-dir layout, sequential 3-stage pipeline (extract_refs.py → validate_refs.py → download_refs.py), and end-of-run cleanup.

Useful flags:

• --yes — non-interactive (CI/batch), overwrite prompts default-yes
• --auto — forwarded to download_refs.py: skip "press Enter" confirm + shorter challenge wait + async retry queue for manual_pending refs (60s delay, single retry, max 3 concurrent). Use for CI / overnight runs; not for sessions where you want to drive captchas yourself.
• --fail-fast — terminate after first actionable unresolved ref (useful in CI to surface real failures fast)
• --output-dir <path> — override default output location
• --config <path> — alternate TOML config (overrides config.local.toml)

Pre-flight checklist (confirm before running)

1. DOI correct? Echo back to user: 即将下载参考文献：DOI=<doi>
2. Edge fully closed? All msedge.exe processes killed (Task Manager check). The script claims the user's persistent Edge profile and needs exclusive access. (Cloak backend skips this.)
3. Config set? First-run users need <SKILL_DIR>/config.local.toml with [crossref].mailto. Missing config → wrapper prints a WARNING but continues with placeholder defaults.
4. Output location agreed? Default for DOI input: <cwd>/<project_name>_refs/. For PDF input: <pdf_dir>/<pdf_stem>_refs/. Override with --output-dir.

Mode B — Custom batch download

Input variability is the point. Don't refuse — route. The agent handles whatever shape the user gave (paste, file, prose, BibTeX, RIS, abstract query) and resolves it to a clean DOI list before handing off to the pipeline.

Step 0 — Canonicalize input (always runs first)

Before any extraction or routing, normalize the input string:

1. Unwrap delimiters around DOIs: strip leading/trailing {}, <>, (), [], and quote marks.
2. Strip URL prefixes: https://doi.org/, http://doi.org/, https://dx.doi.org/, http://dx.doi.org/ → bare DOI.
3. Full-width / Unicode punctuation to ASCII:
   • ／ (U+FF0F) → /
   • ： (U+FF1A) → :
   • ． (U+FF0E) → .
   • Smart quotes "" '' → straight " '
4. Trim trailing punctuation: .,;)}"' (note }).

Apply Step 0 BEFORE the regex pass in B.1 AND before the canonical dedupe compare in step 5 of the main flow.

B.0 — Normalize non-DOI identifiers

For each non-DOI identifier the user gave:

Input	Action
arXiv:2401.12345 or bare arXiv ID	Use 10.48550/arXiv.<id> (canonical), but prefer a journal DOI if the agent can discover one via Crossref query.bibliographic=<arXiv_id>
PMID:12345678 or pubmed.ncbi.nlm.nih.gov/12345678	Hit eutils.ncbi.nlm.nih.gov/entrez/eutils/esummary.fcgi?db=pubmed&id=<pmid> → grab articleids[type=doi]
Semantic Scholar paper ID (S2:abc... / corpusId:N)	Hit api.semanticscholar.org/graph/v1/paper/<id>?fields=externalIds → grab externalIds.DOI
Anything else non-DOI shaped	Leave for B.1 regex pass to ignore; if it survives B.1+B.2 unresolved, drop with skipped (unresolvable_identifier) in the confirm table — do NOT auto-fire requests on garbage

Network preflight: before firing B.0 lookups, do one cheap sanity probe (e.g. HEAD https://api.crossref.org/). If it fails, tell the user "no network — Mode B can't resolve non-DOI identifiers or do discovery; only direct DOI extraction will work" and let them decide to proceed with B.1 only.

Semantic Scholar rate limit: unauthenticated ≤ 1 req/sec. Pace batches; on 429 back off 30s then retry once; on second 429, drop the entry with skipped (ss_rate_limited).

B.1 — DOI extraction

After Step 0 canonicalization:

1. Regex 10\.\d{4,9}/[^\s,;<>"'{}]+ on the canonicalized input (or file contents). The character class explicitly excludes {} so wrappers like BibTeX doi = {10.x/y} don't leak braces.
2. Strip trailing punctuation .,;)}"'.
3. Dedupe via canonical lowercase compare (see flow step 5).
4. Fallback rule: if regex yields DOIs for less than 50% of the apparent entries (e.g. BibTeX with 20 @article entries but only 5 have ASCII DOIs), send the remaining entries to B.2 title lookup rather than silently dropping them.

B.2 — Title → DOI lookup

For each title:

1. Query Crossref: GET https://api.crossref.org/works?query.title=<urlencode>&rows=5&mailto=<config crossref.mailto>
2. Pick top by score. Note: Crossref score is unbounded relevance, NOT 0–100 — absolute thresholds across queries don't compare. Use relative + content rules:
   • If top1.score / top2.score < 1.5 → ambiguous; show user top 3.
   • Always sanity-check matched_title vs input_title by token overlap (or Levenshtein). If overlap < 50%, mark low-confidence regardless of score ratio.
3. If user gave an author or year ("Smith 2024"), cross-check against the candidate's author[].family and issued.date-parts.
4. Each B.2 result enters the confirm table as one of:
   • confidence=high (top1, ratio ≥ 1.5, overlap ≥ 50%, any author/year match consistent) — included by default.
   • confidence=low (any of: ratio < 1.5, overlap < 50%, no author match) — excluded by default; user must explicitly pick.
   • unresolved (0 candidates or all rejected) — dropped with skipped (no_match).

B.3 — Discovery from abstract description

Triggered by queries like "Smith 在 Google Scholar 上的文章", "topic Y top 20", "Nature Energy 2023". Do NOT scrape Google Scholar (anti-bot + ToS). Interpret "Scholar" semantically and use the ladder below.

Tool ladder (try in order, use what's available):

1. Crossref (api.crossref.org/works?query.author= / query.bibliographic= / query.container-title=) — always available, no auth.
2. OpenAlex (api.openalex.org/works?search= or ?filter=author.id:A...) — free, no auth, broader coverage than Crossref author search, returns DOIs directly.
3. Semantic Scholar (api.semanticscholar.org/graph/v1/paper/search?query=...) — better for topic / abstract search. Rate limit ~1 req/sec unauthenticated; pace requests, on 429 back off 30s then drop the query on a second 429.
4. PubMed (bio-research:pubmed MCP) — if biomedical AND the MCP is loaded in the host framework.
5. WebSearch / Tavily / Exa — last-resort if a web-search-* skill is loaded. Highest hallucination risk; agent MUST round-trip every candidate through Crossref or OpenAlex to verify the DOI exists before accepting.

After discovery: present candidates as a numbered list with title + first-author + year + DOI + source (which API found it). Default top 20; ask if user wants more. User strikes out / picks subset → final list locked.

Open-ended-query clarifier: if the agent's discovery would return more than 50 candidates (e.g. user said "Smith 的所有文章" and the author has 200+ publications), confirm scope with user BEFORE returning — "found 200+; you want all of them, top 20 most cited, or filter by year?".

Mode B flow (after sub-flow resolution)

1. Resolve input via Step 0 → B.0 → B.1 → B.2 (leftovers + B.1 fallback) → B.3 (for queries).
2. Consolidate + dedupe. Canonicalize EVERY DOI (lowercase, strip wrappers, no URL prefix, ASCII slash) BEFORE comparing. 10.X/ABC} and 10.x/abc must collapse to one entry.
3. Confirm with user — FULL TABLE, not just first 5:

   找到 N 个唯一 DOI（去重后）。完整列表：
   
     [ 1] doi=10.xxxx/yyy  source=B.1   confidence=high
          title= ...  author= ...  year= ...
     [ 2] doi=10.zzzz/www  source=B.2   confidence=high
          matched_title= ...  (input: "...")
     [ 3] doi=10.aaaa/bbb  source=B.3   confidence=high
          via=Crossref  (query: "...")
     [ 4] doi=10.cccc/ddd  source=B.2   confidence=LOW
          matched_title= ...  (input: "...")  ← excluded; pick to include
     [ 5] (unresolvable)   source=B.0   from: "PMID:99999"
          ← dropped
     ...
   
   开始下载吗？(y=accept all high-confidence / n=cancel /
   include 4 / exclude 1,3 / show <N> / ...)
   

   Default: download confidence=high rows only. confidence=low excluded unless user explicitly includes. Unresolvables dropped.
4. Propose project name (context-aware: "组会文献" → groupmtg_<date>; "Smith 综述补充" → smith_review_extras; nothing topical → custom_<date>). Ask user confirm.
5. Append vs new — if <OUTPUT_DIR>/<project_name>/refs_raw.json exists, ask append / new / rename (default: ask again on any other input — DO NOT default-append). Append rules:
   • Canonicalize new DOIs (Step 0) BEFORE compare.
   • Drop new DOIs already present in existing entries (case-insensitive canonical-form compare).
   • New ids start at id = max(existing_ids) + 1.
   • Never renumber existing entries — validate_refs.py keys its incremental skip on id, renumbering re-assigns prior verified metadata to the wrong DOI. Only verified rows are skipped; failed/pending rows revalidate on re-run.
6. Build refs_raw.json (heredoc the agent runs):

   import json
   from datetime import datetime
   dois = [...]  # finalized canonical-lowercase list
   start_id = 1  # or max(existing_ids)+1 in append mode
   data = {
     "parent_doi": "",  # empty string for clean report labels;
                        # validate_refs.py reads as raw JSON, null
                        # would also work but "" is preferred.
     "parent_title": f"Custom batch — {user_label}",
     "extracted_at": datetime.now().isoformat(timespec="seconds"),
     "total": len(dois),
     "with_doi": len(dois),
     "without_doi": 0,
     "references": [
       {"id": i, "doi": d,
        "key": "", "unstructured": "",
        "author": "", "year": "", "journal": "",
        "volume": "", "first_page": ""}
       for i, d in enumerate(dois, start=start_id)
     ],
   }
   with open(f"{project_name}/refs_raw.json", "w", encoding="utf-8") as f:
       json.dump(data, f, ensure_ascii=False, indent=2)
   

   All metadata fields stay empty — validate_refs.py fills them from Crossref per DOI on success. Rows whose DOI Crossref can't resolve become status=failed with empty metadata (not partially enriched).
7. Run pipeline (skip the wrapper):

   cd <OUTPUT_DIR>
   python <SKILL_DIR>/scripts/validate_refs.py <project_name>
   python <SKILL_DIR>/scripts/download_refs.py <project_name> [--auto] [--fail-fast]
   

Mode B pre-flight checklist

1. Full confirm table approved? User saw EVERY row, not just top 5.
2. Total count + estimated runtime? Roughly: 0.35s × N for validate, ~30-90s per ref for download (publisher-dependent).
3. Project name + new/append decided? First-write = new project; second-write = append OR rename.
4. Edge fully closed? (Edge backend only — cloak skips.)
5. Config set? [crossref].mailto for polite-pool latency.
6. Network reachable? (api.crossref.org HEAD probe).

Compatibility with v0.4 flags

• --auto: works with Mode B (manual_pending refs go to async retry queue same as Mode A).
• --fail-fast: works with Mode B (stops on first actionable unresolved ref).
• [user].verified_no_si_dois: works with Mode B (matches by lowercase DOI — independent of how refs_raw.json was produced).
• CloakBrowser backend (REF_DOWNLOADER_BROWSER=cloak): works with Mode B (browser backend is decided by env var, independent of input mode).

Install prerequisites (before first invocation)

The skill protocol can't manage Python deps. If python -c "import playwright" fails, the user needs:

cd "<SKILL_DIR>"
pip install playwright pymupdf
playwright install msedge          # downloads Edge driver
cp config.example.toml config.local.toml   # then user edits [crossref].mailto

If the user is developing from the source repo instead of an installed skill copy, they can also install from the repo root with pip install -r requirements.txt -r requirements-dev.txt.

Alternative backend: CloakBrowser (Cloudflare-heavy sites)

Default backend is Microsoft Edge. For sites that keep blocking ordinary Playwright (Cloudflare Turnstile, Radware, persistent Just a moment / 安全验证 pages), switch to the CloakBrowser stealth Chromium backend.

What CloakBrowser is. Third-party MIT-licensed Python package by CloakHQ (github.com/CloakHQ/CloakBrowser, pypi:cloakbrowser). Ships a patched Chromium build with anti-fingerprint changes. Its launch_persistent_context_async() is Playwright-API-compatible, which is why ref-downloader can swap it in with one env var. NOT a dependency of ref-downloader — if the user doesn't pip install cloakbrowser, it's never imported and the default Edge path runs as normal. Beta software; user installs it at their own discretion.

# One-time setup (separate from ref-downloader's `pip install playwright pymupdf`)
pip install cloakbrowser

# Switch backend (env vars; no CLI flag changes)
$env:REF_DOWNLOADER_BROWSER = "cloak"
$env:REF_DOWNLOADER_CLOAK_HUMAN_PRESET = "careful"   # optional: slower mouse/scroll
# Optional overrides:
# $env:REF_DOWNLOADER_CLOAK_PROFILE = "<custom path>"  # default: ~/.local/cloakbrowser/profiles/ref-downloader
# $env:REF_DOWNLOADER_CLOAK_PROXY = "http://..."
# $env:REF_DOWNLOADER_CLOAK_GEOIP = "1"
# $env:CLOAKBROWSER_PYTHONPATH = "<dev source>"      # sys.path hint if cloakbrowser is checked out, not pip-installed

python "<SKILL_DIR>/scripts/download_refs.py" <PROJECT_NAME>

Caveats:

• cloakbrowser uses its own Chromium with a separate profile — Edge does NOT need to be closed.
• The separate profile means your institutional cookies are NOT carried — best for open-Cloudflare sites, less useful for paywalled refs your institution licenses.
• A fresh cloak profile may still show Cloudflare/security-verification pages on first visit; warm it manually by opening the target site once with the same REF_DOWNLOADER_CLOAK_PROFILE and finishing any verification before running the downloader.
• human_preset=careful lowers behavior-detection trigger rates but is not a captcha solver.

Output layout

Same for both modes:

<OUTPUT_DIR>/
├── <PROJECT_NAME>/
│   ├── refs_raw.json           # extract_refs.py output (Mode A) or
│   │                           # hand-built JSON (Mode B)
│   ├── refs_validated.json     # validate_refs.py output
│   ├── download_report.csv     # per-ref status (only on graceful
│   │                           # completion; OVERWRITTEN each run —
│   │                           # NOT historical truth)
│   ├── *.pdf                   # reference PDFs
│   └── *_SI.pdf                # supplementary files (where supported)
└── runs/<timestamp>-round-03/
    └── events.jsonl            # full event trace per ref
                                # (append-only across runs;
                                #  THIS is the authoritative history)

Interruption note: if the run is interrupted (Ctrl+C / Edge crash / VPN drop), the root download_report.csv may be stale. Trust the latest runs/<timestamp>/events.jsonl + actual files in <PROJECT_NAME>/.

Common failure modes

Status / symptom	Meaning	Action
manual_pending (auth_redirect)	Bounced to institution SSO	User signs in via live Edge tab; re-run (incremental skips done refs)
manual_pending (challenge_timeout)	Cloudflare / publisher challenge unsolved in time	Re-run interactively; solve captcha when prompted
manual_pending (elsevier_crasolve_shell)	Elsevier viewer stuck in transition	In --auto mode the async retry queue picks it up ~60s later; in interactive mode the hot-session retry usually catches it, else manual click in live page
failed (auto)	Generic auto path failed	Check events.jsonl for that ref; may need a publisher-specific patch
ignored (ignored_institution_access)	DOI listed in [institution].ignored_access_dois	Skip-by-design; remove from config to retry
Edge won't launch	Background msedge.exe still holding profile	Kill all msedge.exe in Task Manager, re-run (cloak backend skips this)
ModuleNotFoundError: playwright	Install prereqs not done	See "Install prerequisites" section above
WARNING: crossref.mailto is the placeholder	First-run config uncustomized	Edit <SKILL_DIR>/config.local.toml → set [crossref].mailto to a real email (Crossref polite pool)
Mode B: Step 0 left full-width slash unconverted	Canonicalization bug	Verify Step 0 ran before regex; flag for design fix
Mode B: BibTeX doi = {10.x/y} left trailing } in refs_raw.json	Step 0 bypassed	Step 0 MUST run before B.1 regex
Mode B: Crossref title query 0 hits for a B.2 row	Title couldn't match	Drop entry as unresolved; suggest user provide author/year/journal
Mode B: B.3 abstract query returns 0 across all ladder steps	No matches found	Suggest user narrow (add author / year / journal); or accept that no papers match
Mode B: B.3 discovery returns 200+ candidates	Query too broad	Ask user to scope (year range / top-N by citations / specific journal) BEFORE listing
Mode B: run_ref_downloader.py invoked accidentally	It assumes parent DOI — will fail	Direct validate_refs.py + download_refs.py invocation only
Mode B: Semantic Scholar 429	Unauthenticated rate limit hit	Back off 30s, retry once; on second 429, drop with skipped (ss_rate_limited)
Mode B: PMID lookup returns no articleids[type=doi]	PubMed has no DOI for this entry	Entry has no DOI; tell user, suggest alternative identifier
Mode B: Input is purely conversational ("上次那 5 篇")	No resolvable content	Refuse; ask user to repaste / attach file
Mode B: No network reachable	B.0 / B.2 / B.3 all need network	Tell user before starting; only B.1 viable

Manual / debug mode

If the wrapper fails partway (Mode A), run the 3 scripts standalone for partial re-execution:

python <SKILL_DIR>/scripts/extract_refs.py <DOI>           # → refs_raw.json
python <SKILL_DIR>/scripts/validate_refs.py <PROJECT>      # → refs_validated.json
python <SKILL_DIR>/scripts/download_refs.py <PROJECT>      # → PDFs + download_report.csv

Mode B uses the same standalone invocation, just skipping extract_refs.py (the agent builds refs_raw.json directly).

Full 8-step manual flow with code snippets, DOI-resolution fallback chain (Zotero query → fitz text → user prompt), and the procedure for extending PUBLISHER_MAP when encountering an unknown DOI prefix → references/agent-runbook.md.

See also

• ../../README.md — human-facing setup, install, usage examples
• references/agent-runbook.md — full manual runbook with code snippets (Mode A debug)
• ../../docs/SUPPORTED_PUBLISHERS.md — publisher tier matrix
• ../../docs/plans/2026-05-28-mode-b-custom-batch-design.md — Mode B design (this revision)
• ../../CONTRIBUTING.md — adding new publisher / institution SSO
• ../../SECURITY.md — Edge profile cookie risk
• config.example.toml — full config schema