research-lit — скилл для Claude Code: поиск и разбор научных статей

---
name: research-lit
description: Search and analyze research papers, find related work, summarize key ideas. Use when user says "find papers", "related work", "literature review", "what does this paper say", or needs to understand academic papers.
argument-hint: "[paper-topic-or-url]"
allowed-tools: Bash(*), Read, Glob, Grep, WebSearch, WebFetch, Write, Agent(aris-fanout-leaf), mcp__zotero__*, mcp__obsidian-vault__*
---

# Research Literature Review

Research topic: $ARGUMENTS

## Constants


- **PAPER_LIBRARY** — Local directory containing user's paper collection (PDFs). Check these paths in order:
  1. `papers/` in the current project directory
  2. `literature/` in the current project directory
  3. Custom path specified by user in `CLAUDE.md` under `## Paper Library`
- **MAX_LOCAL_PAPERS = 20** — Maximum number of local PDFs to scan (read first 3 pages each). If more are found, prioritize by filename relevance to the topic.
- **SOURCES = `all`** — Which literature sources to search. Options: `zotero`, `obsidian`, `local`, `web`, `semantic-scholar`, `deepxiv`, `exa`, `gemini`, `openalex`, `all`. Full source table and selection rules: see `## Data Sources` below.
- **ARXIV_DOWNLOAD = false** — When `true`, download top 3-5 most relevant arXiv PDFs to PAPER_LIBRARY after search. When `false` (default), only fetch metadata (title, abstract, authors) via arXiv API — no files are downloaded.
- **ARXIV_MAX_DOWNLOAD = 5** — Maximum number of PDFs to download when `ARXIV_DOWNLOAD = true`.

> 💡 Overrides:
> - `/research-lit "topic" — paper library: ~/my_papers/` — custom local PDF path
> - `/research-lit "topic" — sources: zotero, local` — only search Zotero + local PDFs
> - `/research-lit "topic" — sources: web` — only search the web (skip all local)
> - `/research-lit "topic" — sources: web, semantic-scholar` — also search Semantic Scholar for published venue papers (IEEE, ACM, etc.)
> - `/research-lit "topic" — sources: all, deepxiv` — use default sources plus DeepXiv
> - `/research-lit "topic" — arxiv download: true` — download top relevant arXiv PDFs
> - `/research-lit "topic" — arxiv download: true, max download: 10` — download up to 10 PDFs

## Data Sources

This skill checks multiple sources **in priority order**. All are optional — if a source is not configured or not requested, skip it silently.

### Source Selection

Parse `$ARGUMENTS` for a `— sources:` directive:
- **If `— sources:` is specified**: Only search the listed sources (comma-separated). Valid values: `zotero`, `obsidian`, `local`, `web`, `semantic-scholar`, `deepxiv`, `exa`, `gemini`, `openalex`, `all`.
- **If not specified**: Default to `all` — search every available source in priority order (`semantic-scholar`, `deepxiv`, `exa`, `gemini`, and `openalex` are **excluded** from `all`; they must be explicitly listed).

Examples:
```
/research-lit "diffusion models"                                    → all (default, no S2)
/research-lit "diffusion models" — sources: all                     → all (default, no S2)
/research-lit "diffusion models" — sources: zotero                  → Zotero only
/research-lit "diffusion models" — sources: zotero, web             → Zotero + web
/research-lit "diffusion models" — sources: local                   → local PDFs only
/research-lit "topic" — sources: obsidian, local, web               → skip Zotero
/research-lit "topic" — sources: web, semantic-scholar              → web + S2 API (IEEE/ACM venue papers)
/research-lit "topic" — sources: deepxiv                            → DeepXiv only
/research-lit "topic" — sources: all, deepxiv                       → default sources + DeepXiv
/research-lit "topic" — sources: all, semantic-scholar              → all + S2 API
/research-lit "topic" — sources: exa                               → Exa only (broad web + content extraction)
/research-lit "topic" — sources: all, exa                          → default sources + Exa web search
/research-lit "topic" — sources: gemini                            → Gemini only (AI-powered broad discovery)
/research-lit "topic" — sources: all, gemini                       → default sources + Gemini discovery
/research-lit "topic" — sources: gemini, semantic-scholar           → Gemini + S2 (broad discovery + venue metadata)
/research-lit "topic" — sources: openalex                          → OpenAlex only (open citation graph + institutions)
/research-lit "topic" — sources: semantic-scholar, openalex         → S2 + OpenAlex (complementary metadata)
```

### Source Table

| Priority | Source | ID | How to detect | What it provides |
|----------|--------|----|---------------|-----------------|
| 1 | **Zotero** (via MCP) | `zotero` | Try calling any `mcp__zotero__*` tool — if unavailable, skip | Collections, tags, annotations, PDF highlights, BibTeX, semantic search |
| 2 | **Obsidian** (via MCP) | `obsidian` | Try calling any `mcp__obsidian-vault__*` tool — if unavailable, skip | Research notes, paper summaries, tagged references, wikilinks |
| 3 | **Local PDFs** | `local` | `Glob: papers/**/*.pdf, literature/**/*.pdf` | Raw PDF content (first 3 pages) |
| 4 | **Web search** | `web` | Always available (WebSearch) | arXiv, Semantic Scholar, Google Scholar |
| 5 | **Semantic Scholar API** | `semantic-scholar` | `$S2_FETCHER` resolves (canonical name `semantic_scholar_fetch.py`, per integration-contract §2) | Published venue papers (IEEE, ACM, Springer) with structured metadata: citation counts, venue info, TLDR. **Only runs when explicitly requested** via `— sources: semantic-scholar` or `— sources: web, semantic-scholar` |
| 6 | **DeepXiv CLI** | `deepxiv` | `$DEEPXIV_FETCHER` resolves (canonical name `deepxiv_fetch.py`, per integration-contract §2) **and** `deepxiv` CLI present (`command -v deepxiv`) | Progressive paper retrieval: search, brief, head, section, trending, web search. **Only runs when explicitly requested** via `— sources: deepxiv` or `— sources: all, deepxiv` |
| 7 | **Exa Search** | `exa` | `$EXA_FETCHER` resolves (canonical name `exa_search.py`, per integration-contract §2); fetcher handles `exa-py` SDK + API key internally | AI-powered broad web search with content extraction (highlights, text, summaries). Covers blogs, docs, news, companies, and research papers beyond arXiv/S2. **Only runs when explicitly requested** via `— sources: exa` or `— sources: all, exa` |
| 8 | **Gemini** (MCP / CLI) | `gemini` | `mcp__gemini-cli__ask-gemini` tool available, or `gemini` CLI installed | AI-powered broad literature discovery — decomposes topics into sub-problems, aliases, and variants for wider retrieval. Prefers MCP, falls back to CLI. **Only runs when explicitly requested** via `— sources: gemini` or `— sources: all, gemini` |
| 9 | **OpenAlex** | `openalex` | `$OPENALEX_FETCHER` resolves (canonical name `openalex_fetch.py`, per integration-contract §2) **and** Python `requests` module importable | Open citation graph with institutional affiliations, funding data, and comprehensive metadata across 250M+ works. Fully open API. **Only runs when explicitly requested** via `— sources: openalex` or `— sources: all, openalex` |

> **Graceful degradation**: If no MCP servers are configured, the skill works exactly as before (local PDFs + web search). Zotero and Obsidian are pure additions.

## Workflow

### Step 0a: Search Zotero Library (if available)

**Skip this step entirely if Zotero MCP is not configured.**

Try calling a Zotero MCP tool (e.g., search). If it succeeds:

1. **Search by topic**: Use the Zotero search tool to find papers matching the research topic
2. **Read collections**: Check if the user has a relevant collection/folder for this topic
3. **Extract annotations**: For highly relevant papers, pull PDF highlights and notes — these represent what the user found important
4. **Export BibTeX**: Get citation data for relevant papers (useful for `/paper-write` later)
5. **Compile results**: For each relevant Zotero entry, extract:
   - Title, authors, year, venue
   - User's annotations/highlights (if any)
   - Tags the user assigned
   - Which collection it belongs to

> 📚 Zotero annotations are gold — they show what the user personally highlighted as important, which is far more valuable than generic summaries.

### Step 0b: Search Obsidian Vault (if available)

**Skip this step entirely if Obsidian MCP is not configured.**

Try calling an Obsidian MCP tool (e.g., search). If it succeeds:

1. **Search vault**: Search for notes related to the research topic
2. **Check tags**: Look for notes tagged with relevant topics (e.g., `#diffusion-models`, `#paper-review`)
3. **Read research notes**: For relevant notes, extract the user's own summaries and insights
4. **Follow links**: If notes link to other relevant notes (wikilinks), follow them for additional context
5. **Compile results**: For each relevant note:
   - Note title and path
   - User's summary/insights
   - Links to other notes (research graph)
   - Any frontmatter metadata (paper URL, status, rating)

> 📝 Obsidian notes represent the user's **processed understanding** — more valuable than raw paper content for understanding their perspective.

### Step 0c: Scan Local Paper Library

Before searching online, check if the user already has relevant papers locally:

1. **Locate library**: Check PAPER_LIBRARY paths for PDF files
   ```
   Glob: papers/**/*.pdf, literature/**/*.pdf
   ```

2. **De-duplicate against Zotero**: If Step 0a found papers, skip any local PDFs already covered by Zotero results (match by filename or title).

3. **Filter by relevance**: Match filenames and first-page content against the research topic. Skip clearly unrelated papers.

4. **Summarize relevant papers**: For each relevant local PDF (up to MAX_LOCAL_PAPERS):
   - Read first 3 pages (title, abstract, intro)
   - Extract: title, authors, year, core contribution, relevance to topic
   - Flag papers that are directly related vs tangentially related

5. **Build local knowledge base**: Compile summaries into a "papers you already have" section. This becomes the starting point — external search fills the gaps.

> 📚 If the user has a comprehensive local collection, the external search can be more targeted (focus on what's missing).
>
> ⚠️ **If all three PAPER_LIBRARY paths miss, say so before moving on** — do not skip silently. A user whose PDFs live in a reference manager (Zotero, Mendeley, ...) otherwise assumes `— sources: all` covered them. Emit:
>
> `WARN: local contributed nothing — no PDFs found in papers/, literature/, or a configured paper library. To include yours, add a "## Paper Library" heading to CLAUDE.md followed by the directory path.`
>
> Then continue to Step 1.

### Step 1: Search (external)
- Use WebSearch to find recent papers on the topic
- Check arXiv, Semantic Scholar, Google Scholar
- Focus on papers from last 2 years unless studying foundational work
- **De-duplicate**: Skip papers already found in Zotero, Obsidian, or local library

**arXiv API search** (runs when `— sources:` is unset, contains `web` or `all`; no download by default — arXiv API is part of the Priority-4 Web tier, see Source Table above):

**Policy D2 tracking discipline (orchestrator-managed)**: the
executor (you, the LLM) maintains an in-context list of contributing
sources. For **helper-backed bash sources** (arxiv, semantic-scholar,
deepxiv, exa, openalex), a source contributes iff its bash block
ran its helper successfully (helper resolved AND invocation exited 0;
note: the helper exiting 0 with an empty result list still counts as
"ran" — downstream relevance ranking is what decides whether the user
actually sees content). For **non-helper sources** (zotero / obsidian /
local PDF / WebSearch / Gemini), the contribution rule is stated in
the Step-1 finalization block below — these are tracked separately
because they don't emit `D2 contribution:` log lines from bash. Sources
that were not requested via `— sources:` do not count. At the end of
Step 1 (before "Optional PDF download"), if zero sources contributed,
surface a D2 empty-aggregate error and stop. (See
integration-contract.md §2 Policy D2 — the in-context tracking
replaces a shared bash accumulator because SKILL bash blocks are
executed as separate shells; state does not survive.)

Resolve `$ARXIV_FETCHER` via the canonical chain (Policy D2 — this
source contributes to the multi-source aggregate; warn-and-continue
on failure, never abort the whole aggregate):

```bash
# Canonical strict-safe resolver (see shared-references/integration-contract.md §2).
cd "$(git rev-parse --show-toplevel 2>/dev/null || pwd)" || exit 1
if [ -z "${ARIS_REPO:-}" ] && [ -f .aris/installed-skills.txt ]; then
    ARIS_REPO=$(awk -F'\t' '$1=="repo_root"{print $2; exit}' .aris/installed-skills.txt 2>/dev/null) || true
fi
if [ -z "${ARIS_REPO:-}" ] && [ -f "$HOME/.aris/repo" ]; then
    ARIS_REPO=$(cat "$HOME/.aris/repo" 2>/dev/null) || true
fi
ARXIV_FETCHER=".aris/tools/arxiv_fetch.py"
[ -f "$ARXIV_FETCHER" ] || ARXIV_FETCHER="tools/arxiv_fetch.py"
[ -f "$ARXIV_FETCHER" ] || { [ -n "${ARIS_REPO:-}" ] && ARXIV_FETCHER="$ARIS_REPO/tools/arxiv_fetch.py"; }
[ -f "$ARXIV_FETCHER" ] || ARXIV_FETCHER=""

if [ -n "$ARXIV_FETCHER" ]; then
  # Search arXiv API for structured results (title, abstract, authors, categories).
  # Wrap with if/then/else so set -e doesn't abort the SKILL.
  if python3 "$ARXIV_FETCHER" search "QUERY" --max 10; then
    echo "D2 contribution: arxiv (helper invocation exit 0)" >&2
  else
    echo "WARN: arxiv_fetch.py invocation failed; D2 aggregate continues with WebSearch results." >&2
  fi
else
  echo "WARN: arxiv_fetch.py not resolved; falling back to WebSearch for arXiv hits." >&2
fi
```

> **Record-keeping**: track the `D2 contribution: …` lines emitted by
> each source's bash block. They form the contributing-source list
> the orchestrator uses for the Step-1 finalization gate below.
> WebSearch (Priority 4) is treated as having contributed iff
> WebSearch was requested (no `— sources:` filter, or the list
> contains `web` or `all`) AND was actually invoked; the orchestrator
> records that separately. (The finalization block below restates
> this rule canonically — both lines must stay in sync.)

If `$ARXIV_FETCHER` is empty (D2 graceful degradation), fall back to WebSearch for arXiv (same as before).

The arXiv API returns structured metadata (title, abstract, full author list, categories, dates) — richer than WebSearch snippets. Merge these results with WebSearch findings and de-duplicate.

**Semantic Scholar API search** (only when `semantic-scholar` is in sources):

When the user explicitly requests `— sources: semantic-scholar` (or `— sources: web, semantic-scholar`), search for published venue papers beyond arXiv:

```bash
# Re-resolve $ARIS_REPO (SKILL bash blocks may run in separate shells).
cd "$(git rev-parse --show-toplevel 2>/dev/null || pwd)" || exit 1
if [ -z "${ARIS_REPO:-}" ] && [ -f .aris/installed-skills.txt ]; then
    ARIS_REPO=$(awk -F'\t' '$1=="repo_root"{print $2; exit}' .aris/installed-skills.txt 2>/dev/null) || true
fi
if [ -z "${ARIS_REPO:-}" ] && [ -f "$HOME/.aris/repo" ]; then
    ARIS_REPO=$(cat "$HOME/.aris/repo" 2>/dev/null) || true
fi
# Resolve $S2_FETCHER (Policy D2 — warn-and-skip on missing).
S2_FETCHER=".aris/tools/semantic_scholar_fetch.py"
[ -f "$S2_FETCHER" ] || S2_FETCHER="tools/semantic_scholar_fetch.py"
[ -f "$S2_FETCHER" ] || { [ -n "${ARIS_REPO:-}" ] && S2_FETCHER="$ARIS_REPO/tools/semantic_scholar_fetch.py"; }
[ -f "$S2_FETCHER" ] || S2_FETCHER=""

if [ -n "$S2_FETCHER" ]; then
  # Search for published CS/Engineering papers with quality filters.
  # Wrap with if/then/else so set -e doesn't abort the SKILL.
  if python3 "$S2_FETCHER" search "QUERY" --max 10 \
      --fields-of-study "Computer Science,Engineering" \
      --publication-types "JournalArticle,Conference"; then
    echo "D2 contribution: semantic_scholar (helper invocation exit 0)" >&2
  else
    echo "WARN: semantic_scholar_fetch.py invocation failed; D2 aggregate continues with remaining sources." >&2
  fi
fi
```

If `$S2_FETCHER` is empty (canonical chain exhausted), skip silently — D2 multi-source aggregate continues with the remaining resolved sources.

**Why use Semantic Scholar?** Many IEEE/ACM journal papers are NOT on arXiv. S2 fills the gap for published venue-only papers with citation counts and venue metadata.

**De-duplication between arXiv and S2**: Match by arXiv ID (S2 returns `externalIds.ArXiv`):
- If a paper appears in both: check S2's `venue`/`publicationVenue` — if it has been published in a journal/conference (e.g. IEEE TWC, JSAC), use S2's metadata (venue, citationCount, DOI) as the authoritative version, since the published version supersedes the preprint. Keep the arXiv PDF link for download.
- If the S2 match has no venue (still just a preprint indexed by S2): keep the arXiv version as-is.
- S2 results without `externalIds.ArXiv` are **venue-only papers** not on arXiv — these are the unique value of this source.

**DeepXiv search** (only when `deepxiv` is in sources):

When the user explicitly requests `— sources: deepxiv` (or includes `deepxiv` in a combined source list), use the DeepXiv adapter for progressive retrieval:

```bash
# Re-resolve $ARIS_REPO (SKILL bash blocks may run in separate shells).
cd "$(git rev-parse --show-toplevel 2>/dev/null || pwd)" || exit 1
if [ -z "${ARIS_REPO:-}" ] && [ -f .aris/installed-skills.txt ]; then
    ARIS_REPO=$(awk -F'\t' '$1=="repo_root"{print $2; exit}' .aris/installed-skills.txt 2>/dev/null) || true
fi
if [ -z "${ARIS_REPO:-}" ] && [ -f "$HOME/.aris/repo" ]; then
    ARIS_REPO=$(cat "$HOME/.aris/repo" 2>/dev/null) || true
fi
# Resolve $DEEPXIV_FETCHER (Policy D2 — warn-and-skip on missing).
DEEPXIV_FETCHER=".aris/tools/deepxiv_fetch.py"
[ -f "$DEEPXIV_FETCHER" ] || DEEPXIV_FETCHER="tools/deepxiv_fetch.py"
[ -f "$DEEPXIV_FETCHER" ] || { [ -n "${ARIS_REPO:-}" ] && DEEPXIV_FETCHER="$ARIS_REPO/tools/deepxiv_fetch.py"; }
[ -f "$DEEPXIV_FETCHER" ] || DEEPXIV_FETCHER=""

if [ -n "$DEEPXIV_FETCHER" ] && command -v deepxiv >/dev/null 2>&1; then
  # Wrap each adapter call so set -e doesn't abort the SKILL.
  if python3 "$DEEPXIV_FETCHER" search "QUERY" --max 10; then
    echo "D2 contribution: deepxiv (helper invocation exit 0)" >&2

    # Then deepen only for the most relevant papers (sub-calls don't change D2 aggregate count):
    python3 "$DEEPXIV_FETCHER" paper-brief ARXIV_ID \
      || echo "WARN: deepxiv_fetch.py paper-brief failed; skipping deepen step." >&2
    python3 "$DEEPXIV_FETCHER" paper-head ARXIV_ID \
      || echo "WARN: deepxiv_fetch.py paper-head failed; skipping deepen step." >&2
    python3 "$DEEPXIV_FETCHER" paper-section ARXIV_ID "Experiments" \
      || echo "WARN: deepxiv_fetch.py paper-section failed; skipping deepen step." >&2
  else
    echo "WARN: deepxiv_fetch.py search invocation failed; D2 aggregate continues with remaining sources." >&2
  fi
fi
```

If `$DEEPXIV_FETCHER` is empty or the `deepxiv` CLI is unavailable, skip this source gracefully and continue with the remaining requested sources (Policy D2 graceful degradation).

**Why use DeepXiv?** It is useful when a broad search should be followed by staged reading rather than immediate full-paper loading. This reduces unnecessary context while still surfacing structure, TLDRs, and the most relevant sections.

**De-duplication against arXiv and S2**:
- Match by arXiv ID first, DOI second, normalized title third
- If DeepXiv and arXiv refer to the same preprint, keep one canonical paper row and record `deepxiv` as an additional source
- If DeepXiv overlaps with S2 on a published paper, prefer S2 venue/citation metadata in the final table, but keep DeepXiv-derived section notes when they add value

**Exa search** (only when `exa` is in sources):

When the user explicitly requests `— sources: exa` (or includes `exa` in a combined source list), use the Exa tool for broad AI-powered web search with content extraction:

```bash
# Re-resolve $ARIS_REPO (SKILL bash blocks may run in separate shells).
cd "$(git rev-parse --show-toplevel 2>/dev/null || pwd)" || exit 1
if [ -z "${ARIS_REPO:-}" ] && [ -f .aris/installed-skills.txt ]; then
    ARIS_REPO=$(awk -F'\t' '$1=="repo_root"{print $2; exit}' .aris/installed-skills.txt 2>/dev/null) || true
fi
if [ -z "${ARIS_REPO:-}" ] && [ -f "$HOME/.aris/repo" ]; then
    ARIS_REPO=$(cat "$HOME/.aris/repo" 2>/dev/null) || true
fi
# Resolve $EXA_FETCHER (Policy D2 — warn-and-skip on missing).
EXA_FETCHER=".aris/tools/exa_search.py"
[ -f "$EXA_FETCHER" ] || EXA_FETCHER="tools/exa_search.py"
[ -f "$EXA_FETCHER" ] || { [ -n "${ARIS_REPO:-}" ] && EXA_FETCHER="$ARIS_REPO/tools/exa_search.py"; }
[ -f "$EXA_FETCHER" ] || EXA_FETCHER=""

if [ -n "$EXA_FETCHER" ]; then
  # Search for research papers with highlights.
  # Wrap with if/then/else so set -e doesn't abort the SKILL.
  exa_contributed=false
  if python3 "$EXA_FETCHER" search "QUERY" --max 10 --category "research paper" --content highlights; then
    exa_contributed=true
  else
    echo "WARN: exa_search.py research-paper invocation failed; D2 aggregate continues." >&2
  fi
  # Search for broader web content (blogs, docs, news)
  if python3 "$EXA_FETCHER" search "QUERY" --max 10 --content highlights; then
    exa_contributed=true
  else
    echo "WARN: exa_search.py broad-web invocation failed; D2 aggregate continues." >&2
  fi
  [ "$exa_contributed" = "true" ] && echo "D2 contribution: exa (at least one invocation exit 0)" >&2
fi
```

If `$EXA_FETCHER` is empty or the `exa-py` SDK is unavailable, skip this source gracefully and continue with the remaining requested sources (Policy D2 graceful degradation).

**Why use Exa?** Exa provides AI-powered search across the broader web (blogs, documentation, news, company pages) with built-in content extraction. It fills a gap between academic databases (arXiv, S2) and generic WebSearch by returning richer content with each result.

**De-duplication against arXiv, S2, and DeepXiv**:
- Match by URL first, then normalized title
- If Exa returns an arXiv paper already found by arXiv/S2, prefer the structured metadata from those sources
- Exa results from non-academic domains (blogs, docs, news) are unique value not covered by other sources

**Gemini search** (only when `gemini` is in sources):

When the user explicitly requests `— sources: gemini` (or includes `gemini` in a combined source list), use Gemini for AI-powered broad literature discovery.

**Priority 1 — Gemini MCP** (preferred): Call `mcp__gemini-cli__ask-gemini` with the search prompt:

```
mcp__gemini-cli__ask-gemini({
  prompt: 'You are a research literature scout. Search comprehensively for papers on: "QUERY"

IMPORTANT CONSTRAINTS:
1. Search from MULTIPLE angles — decompose the topic into sub-problems, aliases, neighboring tasks, and common benchmark/settings variants.
2. Prefer papers that are genuinely relevant, not merely keyword-adjacent.
3. Include top venues, journals, surveys, recent preprints, and papers with code when available.
4. Focus on papers from 2022 onward unless older foundational work is necessary.

For EACH paper found, provide ALL of the following:
- Title: [exact title]
- Authors: [full author list]
- Year: [publication year]
- Venue: [exact conference/journal name + year, or "arXiv preprint"]
- arXiv ID: [format 2401.12345, or "N/A"]
- DOI: [if available, or "N/A"]
- Code URL: [GitHub/GitLab link if available, or "No code"]
- Summary: [one-sentence core contribution]

Find at least 15 papers.',
  model: 'auto-gemini-3'
})
```

**Priority 2 — Gemini CLI fallback** (if MCP unavailable): Use `gemini -p "...same prompt..." 2>/dev/null` via Bash (timeout: 120s).

If both MCP and CLI are unavailable, skip this source gracefully and continue with the remaining requested sources.

**Why use Gemini?** Gemini provides AI-driven discovery that goes beyond keyword matching — it decomposes topics, explores naming variants, and surfaces papers that traditional API-based searches (arXiv, S2) may miss. It fills a different retrieval niche from structured database queries.

**De-duplication against arXiv, S2, DeepXiv, and Exa**:
- Match by arXiv ID first, DOI second, normalized title third
- If Gemini returns a paper already found by S2, prefer S2's citation count and venue metadata
- If Gemini returns a paper already found by arXiv, prefer arXiv's structured metadata
- Gemini's unique value is discovering papers that other keyword-based indexes did not surface
- **Do not use Gemini-reported citation counts** — they may be inaccurate. Use S2 for authoritative citation data.

**OpenAlex search** (only when `openalex` is in sources):

When the user explicitly requests `— sources: openalex` (or includes `openalex` in a combined source list), use OpenAlex API for comprehensive academic metadata:

```bash
# Re-resolve $ARIS_REPO (SKILL bash blocks may run in separate shells).
cd "$(git rev-parse --show-toplevel 2>/dev/null || pwd)" || exit 1
if [ -z "${ARIS_REPO:-}" ] && [ -f .aris/installed-skills.txt ]; then
    ARIS_REPO=$(awk -F'\t' '$1=="repo_root"{print $2; exit}' .aris/installed-skills.txt 2>/dev/null) || true
fi
if [ -z "${ARIS_REPO:-}" ] && [ -f "$HOME/.aris/repo" ]; then
    ARIS_REPO=$(cat "$HOME/.aris/repo" 2>/dev/null) || true
fi
# Resolve $OPENALEX_FETCHER (Policy D2 — warn-and-skip on missing).
OPENALEX_FETCHER=".aris/tools/openalex_fetch.py"
[ -f "$OPENALEX_FETCHER" ] || OPENALEX_FETCHER="tools/openalex_fetch.py"
[ -f "$OPENALEX_FETCHER" ] || { [ -n "${ARIS_REPO:-}" ] && OPENALEX_FETCHER="$ARIS_REPO/tools/openalex_fetch.py"; }
[ -f "$OPENALEX_FETCHER" ] || OPENALEX_FETCHER=""

# Preflight: skip OpenAlex silently if the helper is unresolved OR the
# `requests` Python package is missing. Both checks must pass before
# the script is invoked, so users without `requests` installed never see
# a stack trace from a default `/research-lit` run.
if [ -z "$OPENALEX_FETCHER" ] || ! python3 -c "import requests" >/dev/null 2>&1; then
  echo "OpenAlex source not available (openalex_fetch.py unresolved or 'requests' module missing); skipping." >&2
else
  # Search for papers with comprehensive metadata.
  # Wrap with if/then/else so set -e doesn't abort the SKILL.
  if python3 "$OPENALEX_FETCHER" search "QUERY" --max 10 \
      --year "2022-" \
      --type article \
      --sort relevance; then
    echo "D2 contribution: openalex (helper invocation exit 0)" >&2
  else
    echo "WARN: openalex_fetch.py invocation failed; D2 aggregate continues with remaining sources." >&2
  fi
fi
```

If `openalex_fetch.py` is not found or `requests` module is missing, skip this source gracefully and continue with the remaining requested sources.

**Why use OpenAlex?** Fully open citation graph (no API key required), institutional affiliations, funding data (NSF, NIH), comprehensive topic/keyword metadata, and coverage across all disciplines (not just CS).

**De-duplication against arXiv, S2, DeepXiv, Exa, and Gemini**:
- Match by DOI first (OpenAlex has DOI for most works), then arXiv ID, then normalized title
- If OpenAlex and S2 both have the same paper:
  - Prefer S2 for citation counts (more up-to-date)
  - Prefer S2 for venue metadata (more accurate for CS/AI papers)
  - Use OpenAlex for institutional affiliations and funding data (unique value)
  - Merge both into a richer record
- If OpenAlex and arXiv overlap, prefer arXiv's PDF link and metadata, but keep OpenAlex's citation/institution data
- OpenAlex's unique value: institutional affiliations, funding sources, comprehensive topic classification, and cross-discipline coverage

**D2 aggregate finalization** (per integration-contract §2 Policy D2):

The orchestrator (you, the LLM) maintains an in-context list of
contributing sources by reading the `D2 contribution: <name>` log
lines emitted by each source's bash block above, plus:

- `zotero` if Step 0a returned non-empty Zotero hits.
- `obsidian` if Step 0b returned non-empty Obsidian hits.
- `local` if Step 0c found at least one relevant local PDF.
- `web` if WebSearch (Priority 4) was requested (either no `— sources:`
  filter, or the list contains `web` or `all`) AND was actually invoked.
  Note: `— sources: all` covers the default-on tier (zotero, obsidian,
  local, web) — it does **NOT** include the opt-in fetchers
  (semantic-scholar, deepxiv, exa, gemini, openalex). To enable those,
  add them explicitly (e.g. `— sources: all, semantic-scholar, openalex`),
  matching the existing convention at L42-43 / L51-63 of this SKILL.
- `gemini` if Gemini MCP / CLI returned at least one paper.

If the resulting contributing-source list has zero entries, surface:

> **ERROR**: D2 aggregate empty — every requested source either was
> unresolved, not invoked, failed, or (for MCP / local PDF / Gemini
> sources) returned no usable result. (Note: WebSearch contributes
> when requested and invoked, even if the result set is empty.) The
> multi-source aggregate cannot proceed. Suggest the user retry with
> a wider `— sources:` list (e.g. `web, local`) or check helper
> resolution and SDK installation.

Then stop before Step 1.5. Otherwise log the contributing-source
list to the user (e.g. "Sources contributed: arxiv, semantic_scholar,
web") and proceed.

**Optional PDF download** (only when `ARXIV_DOWNLOAD = true`):

After all sources are searched and papers are ranked by relevance:
```bash
# Re-resolve $ARXIV_FETCHER (SKILL bash blocks may run in separate shells).
cd "$(git rev-parse --show-toplevel 2>/dev/null || pwd)" || exit 1
if [ -z "${ARIS_REPO:-}" ] && [ -f .aris/installed-skills.txt ]; then
    ARIS_REPO=$(awk -F'\t' '$1=="repo_root"{print $2; exit}' .aris/installed-skills.txt 2>/dev/null) || true
fi
if [ -z "${ARIS_REPO:-}" ] && [ -f "$HOME/.aris/repo" ]; then
    ARIS_REPO=$(cat "$HOME/.aris/repo" 2>/dev/null) || true
fi
ARXIV_FETCHER=".aris/tools/arxiv_fetch.py"
[ -f "$ARXIV_FETCHER" ] || ARXIV_FETCHER="tools/a...