refactor: improve PDF extraction, error handling, and proxy configuration

app/exceptions.py

@@ -23,13 +23,5 @@ class ValidationError(AppError):
     """请求参数校验失败（400）。"""
 
 
-class ExternalAPIError(AppError):
-    """外部 API 调用失败（502）。"""
-
-
-class PdfProcessError(AppError):
-    """PDF 处理错误（500）。"""
-
-
 class ConflictError(AppError):
     """资源冲突（409）— 如锁冲突、并发任务冲突。"""

app/main.py

@@ -13,9 +13,7 @@ from app.config import settings
 from app.exceptions import (
     AppError,
     ConflictError,
-    ExternalAPIError,
     NotFoundError,
-    PdfProcessError,
     ValidationError,
 )
 from app.database import engine, init_db
@@ -87,14 +85,6 @@ def create_app() -> FastAPI:
     async def _validation_handler(request, exc):
         return JSONResponse(status_code=400, content={"error": exc.message})
 
-    @app.exception_handler(ExternalAPIError)
-    async def _external_api_handler(request, exc):
-        return JSONResponse(status_code=502, content={"error": exc.message})
-
-    @app.exception_handler(PdfProcessError)
-    async def _pdf_process_handler(request, exc):
-        return JSONResponse(status_code=500, content={"error": exc.message})
-
     @app.exception_handler(ConflictError)
     async def _conflict_handler(request, exc):
         return JSONResponse(status_code=409, content={"error": exc.message})

app/services/claude_backend.py

@@ -41,7 +41,8 @@ async def call_claude(
         fix_errors: 上一轮验证错误列表（用于重试）
     """
     if session_id is None:
-        session_id = f"claude-summary-{uuid.uuid4().hex[:8]}"
+        # claude CLI 的 --session-id 要求合法 UUID；非 UUID 会被拒绝（Invalid session ID）
+        session_id = str(uuid.uuid4())
 
     cmd = [settings.CLAUDE_BIN, "-p", "--output-format", "text"]
 
@@ -51,22 +52,22 @@ async def call_claude(
     else:
         cmd += ["--session-id", session_id]
 
-    cmd.append(prompt)
-
     logger.info(
         "Calling claude (session=%s, fix=%s)",
         session_id,
         bool(fix_errors),
     )
 
+    # prompt 走 stdin，避免长文本（论文 PDF 动辄数十 KB）超出系统 ARG_MAX
     proc = await asyncio.create_subprocess_exec(
         *cmd,
+        stdin=asyncio.subprocess.PIPE,
         stdout=asyncio.subprocess.PIPE,
         stderr=asyncio.subprocess.PIPE,
     )
     try:
         stdout, stderr = await asyncio.wait_for(
-            proc.communicate(),
+            proc.communicate(input=prompt.encode("utf-8")),
             timeout=settings.SUMMARY_TIMEOUT_SECONDS,
         )
     except asyncio.TimeoutError:
@@ -77,8 +78,10 @@ async def call_claude(
         )
 
     if proc.returncode != 0:
-        raise ClaudeProcessError(
+        # claude CLI 把 API 错误输出到 stdout（stderr 常为空），优先用有内容的
-            proc.returncode, stderr.decode("utf-8", errors="replace")
+        detail = stderr.decode("utf-8", errors="replace")
-        )
+        if not detail.strip():
+            detail = stdout.decode("utf-8", errors="replace")
+        raise ClaudeProcessError(proc.returncode, detail)
 
     return stdout.decode("utf-8", errors="replace"), session_id

app/services/embedder.py

@@ -140,7 +140,7 @@ def _get_embedding(text: str) -> list[float] | None:
     }
 
     try:
-        with make_http_client(sync=True) as client:
+        with make_http_client(sync=True, use_proxy=False) as client:
             resp = client.post(url, json=payload, headers=headers)
             resp.raise_for_status()
             data = resp.json()

app/services/pdf_image_extractor.py

@@ -36,12 +36,18 @@ _CLUSTER_GAP = 15
 _MIN_BOX_AREA = 2000
 # caption 文本块与 figure/table 内容块的最大垂直距离（单位: pt）
 _CAPTION_MATCH_DISTANCE = 120
-# 方向不符（figure 标题在上 / table 标题在下）的配对惩罚分（仍允许，兜底异常排版）
+# 游离碎片（配不到 caption）并入紧邻已配 cluster 的最大垂直间距（单位: pt）
-_CAPTION_WRONG_SIDE_PENALTY = 300
+# 容下多面板图的 "(a)/(b)" 子图标占位（实测 Figure 4 两面板间距 36pt）
+_ABSORB_GAP = 60
 # caption 开头标记：Figure 3 / Fig. 3 / Table C1 / Figure 3.5 等（大小写均可）
-# 编号 = 数字开头 或 字母+数字（附录 C1）；行首匹配，规避正文 "see Table 3" 引用
+# 编号 = 数字开头 或 字母+数字（附录 C1）；行首匹配，规避正文 "see Table 3" 引用。
+# 否定前瞻再排除多图引用型正文 —— "Figure 14 and 15 show..." / "Figure 1 to 3" /
+# "Table 2, 3" 这类引用多张图表的句子不是独立标题，真标题从不引用多个编号。
 _CAPTION_HEAD_RE = re.compile(
-    r"^\s*(Figure|Fig\.?|Table)\b\.?\s+([0-9][0-9A-Za-z.]*|[A-Z]\d[0-9A-Za-z.]*)",
+    r"^\s*(Figure|Fig\.?|Table)\b\.?\s+([0-9][0-9A-Za-z.]*|[A-Z]\d[0-9A-Za-z.]*)"
+    r"(?![0-9A-Za-z.])"  # 编号须是完整 token，防止 "Figure 14" 回溯成 "Figure 1" 逃逸
+    r"(?!\s*(?:and|to|through|vs\.?|&)\s+\d)"  # "Figure 3 and 4" / "Figure 1 to 3"
+    r"(?!\s*,\s*\d)",  # "Figure 3, 4"
     re.IGNORECASE,
 )
 
@@ -142,8 +148,8 @@ def _find_caption_blocks(page) -> list[_CaptionBlock]:
             "".join(span.get("text", "") for span in line.get("spans", []))
             for line in lines
         ]
-        first_line = next((t for t in line_texts if t.strip()), "")
+        joined = " ".join(t.strip() for t in line_texts if t.strip())
-        m = _CAPTION_HEAD_RE.match(first_line)
+        m = _CAPTION_HEAD_RE.match(joined)
         if not m:
             continue
         kind_word, num = m.group(1), m.group(2)
@@ -151,7 +157,7 @@ def _find_caption_blocks(page) -> list[_CaptionBlock]:
         bbox = block.get("bbox")
         if not bbox or len(bbox) != 4:
             continue
-        full_text = " ".join(t.strip() for t in line_texts if t.strip())
+        full_text = joined
         results.append(
             _CaptionBlock(
                 id=f"{'Table' if is_table else 'Figure'} {num}",
@@ -166,18 +172,25 @@ def _find_caption_blocks(page) -> list[_CaptionBlock]:
 def _pair_caption_blocks(
     content_clusters: list[_BoxCluster],
     caption_blocks: list[_CaptionBlock],
-) -> dict[int, _CaptionBlock]:
+) -> dict[int, list[int]]:
-    """每个内容块配方向上最近的同类型标题块。
+    """每个 caption 配对其垂直 span 内的所有同类型 cluster（支持复合图/子表）。
 
-    figure 标题惯例在下方、table 标题在上方；方向相符优先，不符加惩罚兜底
+    不预设标题在内容上方还是下方 —— figure 惯例标题在下、table 惯例标题在上，
-    （跨页 / 异常排版）。按 (距离+惩罚) 升序贪心匹配，每个内容块与标题块唯一配对。
+    但不少论文反向排版（table 标题在表下方）；用方向作硬约束或加错向惩罚会把
+    "同页相邻两张表" 错并（标题居中的那张吞掉邻居）。改为上下两侧平等地按垂直
+    距离打分，每个 cluster 唯一归属最近的同类 caption，但一个 caption 可被多个
+    cluster 共享 —— 这样一张被 DocLayout 切成多个稀疏子框的复合图/复合表，能
+    整体配到它的主标题（而非只截其中一个子图/子表）。
+
+    Returns:
+        caption_idx → [cluster_idx, ...]，按 cluster 在页面上的位置排序，
+        保证合并/渲染顺序稳定。
     """
     candidates: list[tuple[float, int, int]] = []
     for c_idx, content in enumerate(content_clusters):
-        want_below = content.boxclass == "picture"  # figure 标题在下
+        cluster_kind = "figure" if content.boxclass == "picture" else "table"
-        want_kind = "figure" if want_below else "table"
         for b_idx, cap in enumerate(caption_blocks):
-            if cap.kind != want_kind:
+            if cap.kind != cluster_kind:  # 类型过滤：防 figure↔table 串台
                 continue
             cx0, cy0, cx1, cy1 = cap.bbox
             h_overlap = min(content.x1, cx1) - max(content.x0, cx0)
@@ -185,24 +198,87 @@ def _pair_caption_blocks(
             if min_width <= 0 or h_overlap < min_width * 0.25:
                 continue
             if cy1 <= content.y0:  # 标题在内容上方
-                side_below, v_gap = False, content.y0 - cy1
+                v_gap = content.y0 - cy1
             elif cy0 >= content.y1:  # 标题在内容下方
-                side_below, v_gap = True, cy0 - content.y1
+                v_gap = cy0 - content.y1
             else:
                 continue  # 重叠，跳过
             if v_gap > _CAPTION_MATCH_DISTANCE:
                 continue
-            penalty = 0.0 if side_below == want_below else _CAPTION_WRONG_SIDE_PENALTY
+            candidates.append((v_gap, c_idx, b_idx))
-            candidates.append((v_gap + penalty, c_idx, b_idx))
 
-    matches: dict[int, _CaptionBlock] = {}
+    # cluster 唯一归属最近的 caption；caption 可被多个 cluster 共享（复合图/子图）
-    used: set[int] = set()
+    cluster_to_caption: dict[int, int] = {}
     for _score, c_idx, b_idx in sorted(candidates):
-        if c_idx in matches or b_idx in used:
+        if c_idx in cluster_to_caption:
             continue
-        matches[c_idx] = caption_blocks[b_idx]
+        cluster_to_caption[c_idx] = b_idx
-        used.add(b_idx)
+
-    return matches
+    # 聚合 caption → clusters，按页面位置排序保证稳定的合并/渲染顺序
+    caption_to_clusters: dict[int, list[int]] = {}
+    for c_idx, b_idx in cluster_to_caption.items():
+        caption_to_clusters.setdefault(b_idx, []).append(c_idx)
+    for b_idx in caption_to_clusters:
+        caption_to_clusters[b_idx].sort(
+            key=lambda i: (content_clusters[i].y0, content_clusters[i].x0)
+        )
+    return caption_to_clusters
+
+
+def _absorb_stragglers(
+    clusters: list[_BoxCluster],
+    caption_blocks: list[_CaptionBlock],
+    caption_matches: dict[int, list[int]],
+) -> None:
+    """把配不到 caption、却紧邻某已配 cluster 的同类型游离碎片并入该 cluster 所属 caption。
+
+    多面板图常把主 caption 只放在最下方，离 caption 过远（> _CAPTION_MATCH_DISTANCE）
+    的上方面板会被正常配对漏掉（如 Figure 4 的 (a) 子图距主标题 270pt）。这里把它们
+    并入紧邻的、已归属某 caption 的同类型 cluster，两道护栏避免误并：
+
+      1. 垂直紧邻（≤ _ABSORB_GAP）且水平重叠（同一列）——排除不同列的无关图；
+      2. 两者之间不得夹其他 caption ——有 caption 即另一张图/表的边界（如 Table 7/8
+         之间夹 Table 7 标题），不并，从而不破坏表格的独立配对。
+    """
+    # cluster_idx → caption_idx（已配 cluster 的反向索引）
+    cluster_to_cap: dict[int, int] = {}
+    for cap_idx, idxs in caption_matches.items():
+        for c_idx in idxs:
+            cluster_to_cap[c_idx] = cap_idx
+
+    # 多趟扫描直到稳定：游离面板可能链式排列（上图→中图→下图→caption），
+    # 单趟只能吸收紧邻已配 cluster 的那一层；中图被并入后才轮到上图，故需重复。
+    changed = True
+    while changed:
+        changed = False
+        for u_idx, u in enumerate(clusters):
+            if u_idx in cluster_to_cap:
+                continue  # 已配，无需吸收
+            best_cap: int | None = None
+            best_gap: float | None = None
+            for p_idx, cap_idx in cluster_to_cap.items():
+                p = clusters[p_idx]
+                if p.boxclass != u.boxclass:
+                    continue  # 类型不同（figure vs table）不并
+                gap = max(0.0, max(u.y0, p.y0) - min(u.y1, p.y1))
+                if gap > _ABSORB_GAP:
+                    continue  # 护栏 1：垂直不紧邻
+                if min(u.x1, p.x1) - max(u.x0, p.x0) <= 0:
+                    continue  # 护栏 1：水平不重叠，非同一列
+                # 护栏 2：u 与 p 之间的垂直区间不得夹任何 caption
+                between_lo = min(u.y1, p.y1)
+                between_hi = max(u.y0, p.y0)
+                if any(
+                    not (cb.bbox[3] < between_lo or cb.bbox[1] > between_hi)
+                    for cb in caption_blocks
+                ):
+                    continue
+                if best_gap is None or gap < best_gap:
+                    best_gap, best_cap = gap, cap_idx
+            if best_cap is not None:
+                caption_matches[best_cap].append(u_idx)
+                cluster_to_cap[u_idx] = best_cap  # 标记已并入，供后续趟链式吸收
+                changed = True
 
 
 # ── Phase 1: 检测 + 渲染 ──────────────────────────────────────────────
@@ -259,6 +335,7 @@ def _process_page(
     """处理单页：检测内容 box → 文本定位 caption → 只渲染配到标题的。
 
     配到 Figure/Table caption 的 box 用 caption 自带 ID 命名（figure_3.jpg）；
+    同一 caption 的多个 cluster（复合图/子图被 DocLayout 切散）合并 bbox 整张截取；
     没配到标题的（Algorithm 伪代码、无编号附录表、误检碎片）一律过滤，不输出。
     """
     page = doc[page_idx]
@@ -280,38 +357,46 @@ def _process_page(
     # 聚类：将同一 figure/table 的碎片 box 合并；用 PDF 文本定位 caption
     clusters = _cluster_boxes(raw_boxes)
     caption_blocks = _find_caption_blocks(page)
+    # caption_idx → [cluster_idx, ...]；一个 caption 可含多个子图 cluster（复合图）
     caption_matches = _pair_caption_blocks(clusters, caption_blocks)
+    # 把距主 caption 过远的游离面板（如多面板图上方的 (a) 子图）并入紧邻的已配 cluster
+    _absorb_stragglers(clusters, caption_blocks, caption_matches)
 
     extracted = 0
-    for cluster_idx, cluster in enumerate(clusters):
+    for cap_idx, cluster_indices in caption_matches.items():
-        cap_match = caption_matches.get(cluster_idx)
+        cap = caption_blocks[cap_idx]
-        if cap_match is None:
+        if cap.id in seen_labels:
-            continue  # 无 Figure/Table 标题 → 过滤（Algorithm、无编号表、误检碎片）
-        if cap_match.id in seen_labels:
             continue  # 同一图表被 DocLayout 切成多块重复检测，跳过后续
-        seen_labels.add(cap_match.id)
+        seen_labels.add(cap.id)
 
-        filename = f"{cap_match.id.replace(' ', '_').lower()}.jpg"
+        # 同一 caption 的所有 cluster 合并 bbox，复合图/子图整张截取
+        members = [clusters[i] for i in cluster_indices]
+        merged = _BoxCluster(members)
+
+        filename = f"{cap.id.replace(' ', '_').lower()}.jpg"
         if not _render_box(
             page,
-            cluster,
+            merged,
             images_dest,
             filename,
-            cap_match.kind,
+            cap.kind,
             page_num,
-            caption_bbox=cap_match.bbox,
+            caption_bbox=cap.bbox,
         ):
             continue
 
-        manifest[filename] = {
+        info = {
             "page": page_num,
-            "type": cap_match.kind,
+            "type": cap.kind,
-            "label": cap_match.id,
+            "label": cap.id,
-            "box": _cluster_to_box(cluster),
+            "box": _cluster_to_box(merged),
-            "caption_text": cap_match.text[:500],
+            "caption_text": cap.text[:500],
-            "caption_box": cap_match.bbox,
+            "caption_box": cap.bbox,
             "caption_source": "text",
         }
+        if len(members) > 1:
+            info["subfigure_count"] = len(members)
+        manifest[filename] = info
         extracted += 1
 
     return extracted
@@ -458,19 +543,31 @@ def link_figures_with_images(
     if not unmatched:
         return figures
 
+    # 已被策略 1（精确匹配）占用的图片不参与兜底，否则会把已正确归属的图复用给
+    # 别的条目（如缺失的 Table 4 误链到 Table 1 的截图）。
+    assigned_urls = {f["image_url"] for f in figures if f.get("image_url")}
+
     # 按类型分流：Figure vs Table
     fig_type_unmatched = [f for f in unmatched if _is_figure_type(f.get("id", ""))]
     table_type_unmatched = [
         f for f in unmatched if not _is_figure_type(f.get("id", ""))
     ]
 
-    # 提取的图片按类型分流，按文件名中的编号排序
+    # 剩余未占用图片按类型分流，按文件名中的编号排序
     fig_images = sorted(
-        [img for img in images if "table" not in img["name"].lower()],
+        [
+            img
+            for img in images
+            if "table" not in img["name"].lower() and img["url"] not in assigned_urls
+        ],
         key=lambda img: _image_sort_key(img["name"]),
     )
     table_images = sorted(
-        [img for img in images if "table" in img["name"].lower()],
+        [
+            img
+            for img in images
+            if "table" in img["name"].lower() and img["url"] not in assigned_urls
+        ],
         key=lambda img: _image_sort_key(img["name"]),
     )
 

app/utils.py

@@ -93,13 +93,14 @@ def release_lock(db, lock) -> None:
 
 
 def make_http_client(
-    *, sync: bool = False, follow_redirects: bool = False, **kwargs
+    *, sync: bool = False, follow_redirects: bool = False, use_proxy: bool = True, **kwargs
 ) -> httpx.AsyncClient | httpx.Client:
     """创建带 proxy 和默认配置的 httpx 客户端。
 
     Args:
         sync: True 返回同步 Client，False 返回 AsyncClient
         follow_redirects: 是否跟随重定向
+        use_proxy: 是否使用 HF_PROXY 代理（默认 True；国内 API 如 embedder 应传 False）
         **kwargs: 覆盖默认参数
     """
     defaults: dict = {
@@ -107,7 +108,7 @@ def make_http_client(
         "headers": {"User-Agent": settings.HTTP_USER_AGENT},
         "follow_redirects": follow_redirects,
     }
-    if settings.http_proxy:
+    if use_proxy and settings.http_proxy:
         defaults["transport"] = (
             httpx.HTTPTransport(proxy=settings.http_proxy)
             if sync

tests/test_pdf_image_extractor.py

@@ -1,5 +1,6 @@
 from __future__ import annotations
 
+import json
 from unittest.mock import MagicMock
 
 import pymupdf
@@ -168,3 +169,286 @@ def test_process_page_filters_uncaptioned(tmp_path):
 
     assert extracted == 0
     assert manifest == {}
+
+
+def test_process_page_merges_subfigure_clusters(tmp_path):
+    """复合图被切成多个稀疏子图框时，配到同一主 caption 后合并成一张截图。"""
+    images_dest = tmp_path / "images"
+    images_dest.mkdir()
+    manifest: dict[str, dict] = {}
+
+    pix = MagicMock()
+    pix.tobytes.return_value = b"jpeg"
+
+    page = MagicMock()
+    page.rect.width = 600
+    page.rect.height = 800
+    page.get_pixmap.return_value = pix
+    # 主 caption 覆盖整张复合图宽度，在内容下方
+    page.get_text.return_value = {
+        "blocks": [_caption_block((95, 410, 455, 425), "Figure 3: Composite figure.")]
+    }
+
+    doc = MagicMock()
+    doc.__getitem__.return_value = page
+
+    # 两个子图框左右排列，间距 50pt（> _CLUSTER_GAP=15，不被 _cluster_boxes 合并）
+    boxes = [
+        LayoutBox(100, 100, 250, 300, "picture"),
+        LayoutBox(300, 100, 450, 300, "picture"),
+    ]
+
+    extracted = mod._process_page(
+        doc,
+        0,
+        boxes,
+        images_dest=images_dest,
+        manifest=manifest,
+        seen_labels=set(),
+        arxiv_id="2401.00003",
+    )
+
+    assert extracted == 1  # 两子图合并成一张
+    info = manifest["figure_3.jpg"]
+    assert info["label"] == "Figure 3"
+    assert info["subfigure_count"] == 2
+    # 合并 bbox = union 两子图 = [100,100,450,300]
+    assert info["box"] == [100.0, 100.0, 450.0, 300.0]
+
+
+def test_process_page_two_tables_captions_below_not_merged(tmp_path):
+    """同页相邻两张表、标题都在表下方时，各自配对自己的内容框，不互相吞并。
+
+    回归 2606.19926：Table 3/4 同页、两标题均在表下方。旧逻辑（table 标题
+    必在上的错向惩罚）会让 Table 3 吞掉 Table 4 的内容框、Table 4 缺图。
+    """
+    images_dest = tmp_path / "images"
+    images_dest.mkdir()
+    manifest: dict[str, dict] = {}
+
+    pix = MagicMock()
+    pix.tobytes.return_value = b"jpeg"
+
+    page = MagicMock()
+    page.rect.width = 600
+    page.rect.height = 800
+    page.get_pixmap.return_value = pix
+    # 两个 table 标题都在各自内容下方（本文实际排版）
+    page.get_text.return_value = {
+        "blocks": [
+            _caption_block((80, 324, 460, 346), "Table 3 Pass@1 success rate."),
+            _caption_block((80, 503, 460, 547), "Table 4 Core gold-context metrics."),
+        ]
+    }
+
+    doc = MagicMock()
+    doc.__getitem__.return_value = page
+
+    boxes = [
+        LayoutBox(80, 77, 460, 321, "table"),  # Table 3 内容（上）
+        LayoutBox(80, 420, 460, 494, "table"),  # Table 4 内容（下）
+    ]
+
+    extracted = mod._process_page(
+        doc,
+        0,
+        boxes,
+        images_dest=images_dest,
+        manifest=manifest,
+        seen_labels=set(),
+        arxiv_id="2606.19926",
+    )
+
+    assert extracted == 2
+    assert "table_3.jpg" in manifest
+    assert "table_4.jpg" in manifest
+    # 各自只含自己的内容框，未被合并成一张大图
+    assert manifest["table_3.jpg"]["box"] == [80.0, 77.0, 460.0, 321.0]
+    assert manifest["table_4.jpg"]["box"] == [80.0, 420.0, 460.0, 494.0]
+    assert "subfigure_count" not in manifest["table_3.jpg"]
+    assert "subfigure_count" not in manifest["table_4.jpg"]
+
+
+def test_caption_regex_rejects_multi_reference_body_text():
+    """多图引用型正文（"Figure 14 and 15 show..."）不应被当作独立 caption。
+
+    回归 2606.24597：第 35 页正文 "Figure 14 and 15 show..." 被误判为 caption，
+    与真标题 "Figure 14:" 竞争 seen_labels 去重，导致 Figure 14 截成另一张图。
+    """
+    re_ = mod._CAPTION_HEAD_RE
+    # 真标题：编号后接标题文字 / 冒号 / 子图编号，均应命中
+    assert re_.match("Figure 14: Interaction examples.")
+    assert re_.match("Figure 1 Context efficiency.")
+    assert re_.match("Table 1 Zero-shot results.")
+    assert re_.match("Figure 3.5 Sub-figure detail.")
+    # 多图引用正文：编号后紧跟 "and/to/, + 另一编号" → 拒绝
+    assert not re_.match("Figure 14 and 15 show representative examples.")
+    assert not re_.match("Figure 1 to 3 illustrate the pipeline.")
+    assert not re_.match("Table 2, 3 compare methods.")
+
+
+def test_link_figures_fallback_excludes_assigned_images(tmp_path, monkeypatch):
+    """序号兜底不复用已被精确匹配（策略 1）占用的图片。
+
+    回归 2606.19926：Table 4 在 manifest 缺图 → 兜底误取 table_1.jpg（已属 Table 1）。
+    """
+    monkeypatch.setattr(mod, "PAPERS_DIR", tmp_path)
+    images_dir = tmp_path / "x" / "images"
+    images_dir.mkdir(parents=True)
+    # manifest 只命中 Table 1 → table_1.jpg；Table 4 无精确匹配，走兜底
+    (images_dir / "manifest.json").write_text(
+        json.dumps({"table_1.jpg": {"label": "Table 1"}})
+    )
+
+    figures = [{"id": "Table 1"}, {"id": "Table 4"}]
+    images = [
+        {"name": "table_1.jpg", "url": "/papers/x/images/table_1.jpg"},
+        {"name": "table_2.jpg", "url": "/papers/x/images/table_2.jpg"},
+    ]
+
+    out = mod.link_figures_with_images(figures, images, "x")
+    by_id = {f["id"]: f for f in out}
+
+    assert by_id["Table 1"]["image_url"] == "/papers/x/images/table_1.jpg"
+    # 兜底只能拿到未被占用的 table_2.jpg，不能再复用 table_1.jpg
+    assert by_id["Table 4"]["image_url"] == "/papers/x/images/table_2.jpg"
+
+
+def test_process_page_absorbs_far_subfigure_panel(tmp_path):
+    """多面板图主 caption 只在最下方时，距 caption 过远的上方面板被吸收进来。
+
+    回归 2606.24597 Figure 4：(a) 子图距主标题 270pt（> _CAPTION_MATCH_DISTANCE），
+    原本被丢弃；(b) 子图距 46pt 正常配对。吸收后两面板合并成一张含 (a)(b)。
+    """
+    images_dest = tmp_path / "images"
+    images_dest.mkdir()
+    manifest: dict[str, dict] = {}
+
+    pix = MagicMock()
+    pix.tobytes.return_value = b"jpeg"
+    page = MagicMock()
+    page.rect.width = 600
+    page.rect.height = 800
+    page.get_pixmap.return_value = pix
+    # 主 caption 在最下方 y=479，距上方 (a) 面板 270pt、距 (b) 面板 46pt
+    page.get_text.return_value = {
+        "blocks": [
+            _caption_block((80, 479, 520, 500), "Figure 4: Representative examples.")
+        ]
+    }
+    doc = MagicMock()
+    doc.__getitem__.return_value = page
+    boxes = [
+        LayoutBox(80, 73, 520, 209, "picture"),  # (a) 面板，距 caption 270pt
+        LayoutBox(80, 245, 520, 433, "picture"),  # (b) 面板，距 caption 46pt
+    ]
+
+    extracted = mod._process_page(
+        doc,
+        0,
+        boxes,
+        images_dest=images_dest,
+        manifest=manifest,
+        seen_labels=set(),
+        arxiv_id="2606.24597",
+    )
+
+    assert extracted == 1
+    info = manifest["figure_4.jpg"]
+    # 合并后含两面板：y 从 73 到 433
+    assert info["box"] == [80.0, 73.0, 520.0, 433.0]
+    assert info["subfigure_count"] == 2
+
+
+def test_process_page_absorbs_chained_panels_multipass(tmp_path):
+    """链式排列的多面板（上图→中图→下图→caption）需多趟吸收才能全部并入。
+
+    回归 2606.24597 Figure 15：3 个面板纵排、主 caption 只在最下方，中图被并入后
+    上图才能链上。单趟扫描会漏掉最上图。
+    """
+    images_dest = tmp_path / "images"
+    images_dest.mkdir()
+    manifest: dict[str, dict] = {}
+
+    pix = MagicMock()
+    pix.tobytes.return_value = b"jpeg"
+    page = MagicMock()
+    page.rect.width = 600
+    page.rect.height = 800
+    page.get_pixmap.return_value = pix
+    # 主 caption 在最下方 y=710，仅下图（y505-669）在其 120pt 内
+    page.get_text.return_value = {
+        "blocks": [
+            _caption_block((80, 710, 520, 730), "Figure 15: Text-based domains.")
+        ]
+    }
+    doc = MagicMock()
+    doc.__getitem__.return_value = page
+    boxes = [
+        LayoutBox(80, 73, 520, 217, "picture"),  # 上图，距 caption 493pt
+        LayoutBox(80, 256, 520, 467, "picture"),  # 中图，距 caption 243pt
+        LayoutBox(80, 505, 520, 669, "picture"),  # 下图，距 caption 41pt（配得上）
+    ]
+
+    extracted = mod._process_page(
+        doc,
+        0,
+        boxes,
+        images_dest=images_dest,
+        manifest=manifest,
+        seen_labels=set(),
+        arxiv_id="2606.24597",
+    )
+
+    assert extracted == 1
+    info = manifest["figure_15.jpg"]
+    # 三面板全并入：y 从 73 到 669
+    assert info["box"] == [80.0, 73.0, 520.0, 669.0]
+    assert info["subfigure_count"] == 3
+
+
+def test_absorb_stragglers_respects_caption_boundary(tmp_path):
+    """两图之间夹着（异类）标题时，漏配的上图不并入下图（吸收护栏 2）。
+
+    上图距下图标题 160pt（>120）漏配；下图正常配对。两图间夹一个 Table 标题
+    （异类，上图不会配它）→ 护栏判定有 caption 边界，不吸收上图。
+    """
+    images_dest = tmp_path / "images"
+    images_dest.mkdir()
+    manifest: dict[str, dict] = {}
+
+    pix = MagicMock()
+    pix.tobytes.return_value = b"jpeg"
+    page = MagicMock()
+    page.rect.width = 600
+    page.rect.height = 800
+    page.get_pixmap.return_value = pix
+    page.get_text.return_value = {
+        "blocks": [
+            _caption_block(
+                (80, 160, 460, 175), "Table 9 Some table."
+            ),  # 夹中间的表标题
+            _caption_block((80, 310, 520, 330), "Figure 5 Some figure."),  # 下图标题
+        ]
+    }
+    doc = MagicMock()
+    doc.__getitem__.return_value = page
+    boxes = [
+        LayoutBox(80, 73, 520, 150, "picture"),  # 上图，距 Figure 5 标题 160pt → 漏配
+        LayoutBox(80, 185, 520, 300, "picture"),  # 下图，距 Figure 5 标题 10pt → 配上
+    ]
+
+    extracted = mod._process_page(
+        doc,
+        0,
+        boxes,
+        images_dest=images_dest,
+        manifest=manifest,
+        seen_labels=set(),
+        arxiv_id="2606.24597",
+    )
+
+    # 上图未被并入下图 → 仅下图输出，box 不含上图、无 subfigure_count
+    assert extracted == 1
+    assert manifest["figure_5.jpg"]["box"] == [80.0, 185.0, 520.0, 300.0]
+    assert "subfigure_count" not in manifest["figure_5.jpg"]