From a4028f3c8d7b4b5b468f5c7d3bcaac3fe2f8d853 Mon Sep 17 00:00:00 2001
From: himanshupatro-334 <akashpatra.334@gmail.com>
Date: Mon, 12 Oct 2026 23:59:27 +0530
Subject: [PATCH] fix: resolve cross-directory C/C++ quoted includes (#4354)

(cherry picked from commit 97b8c8dbf20b9e2b9200235407a3ec011f8175db)
---
 graphify/extract.py                | 163 ++++++++-
 graphify/extractors/objc.py        |  18 +-
 tests/test_c_include_resolution.py | 516 +++++++++++++++++++++++++++++
 3 files changed, 693 insertions(+), 4 deletions(-)
 create mode 100644 tests/test_c_include_resolution.py

diff --git a/graphify/extract.py b/graphify/extract.py
index 8ec056a36..d31c89326 100644
--- a/graphify/extract.py
+++ b/graphify/extract.py
@@ -1112,7 +1112,7 @@ def _import_c(node, source: bytes, file_nid: str, stem: str, edges: list, str_pa
             module_name = raw.split("/")[-1].split(".")[0]
             if module_name:
                 tgt_nid = _make_id(module_name)
-                edges.append({
+                edge_dict = {
                     "source": file_nid,
                     "target": tgt_nid,
                     "relation": "imports",
@@ -1121,7 +1121,13 @@ def _import_c(node, source: bytes, file_nid: str, stem: str, edges: list, str_pa
                     "source_file": str_path,
                     "source_location": f"L{node.start_point[0] + 1}",
                     "weight": 1.0,
-                })
+                }
+                if child.type != "system_lib_string":
+                    edge_dict["metadata"] = sanitize_metadata({
+                        "raw_include": raw,
+                        "include_kind": "quoted",
+                    })
+                edges.append(edge_dict)
             break
 
 
@@ -6289,6 +6295,150 @@ def _resolve_kotlin_import_targets(
             e["target"] = candidates[0]
 
 
+_C_FAMILY_HEADER_EXTS = frozenset({".h", ".hpp", ".hh", ".hxx", ".cuh", ".inl"})
+
+
+def _resolve_c_include_edges(
+    edges: list[dict],
+    resolution_nodes: list[dict],
+    root: Path | None = None,
+) -> None:
+    """Resolve unresolved quoted C/C++/ObjC include edges to matching header file nodes (#4354).
+
+    When a quoted #include / #import is outside the including file's directory,
+    _resolve_c_include_path cannot resolve it, so per-file extraction emits a
+    fallback edge targeting a bare stem ID with metadata={"raw_include": ..., "include_kind": "quoted"}.
+    This pass runs after canonical node IDs and collision disambiguation are
+    established, but before import-evidence indexing.
+
+    Resolution rules:
+    1. Only processes unresolved quoted includes (metadata.include_kind == "quoted"
+       and metadata.raw_include is present).
+    2. Explicit relative (./ or ../) or absolute paths that failed sibling
+       resolution are never resolved via corpus fallback.
+    3. Matches the full include path as a path suffix, not merely the basename
+       when the include contains directory components.
+    4. Prefers exact-case matches over case-insensitive matches.
+    5. If no exact-case candidate exists, falls back to case-insensitive matching.
+    6. If multiple candidates remain, uses longest-shared-directory-prefix as a
+       tie-breaker. Resolves only when one candidate has a strictly greater score
+       than all others; ties remain unresolved. This is a heuristic and does not
+       claim to reproduce compiler include-order semantics.
+    7. Resolved edges point to the canonical target file node ID.
+    8. Unresolved edges remain untouched for external stub creation.
+    """
+    if not edges or not resolution_nodes:
+        return
+
+    headers_by_basename: dict[str, list[tuple[dict, str]]] = {}
+    headers_by_basename_ci: dict[str, list[tuple[dict, str]]] = {}
+
+    for n in resolution_nodes:
+        if n.get("type") == "namespace" or n.get("file_type") == "rationale":
+            continue
+        sf = n.get("source_file")
+        if not sf:
+            continue
+        sf_str = str(sf)
+        sf_p = Path(sf_str)
+        if sf_p.suffix.lower() not in _C_FAMILY_HEADER_EXTS:
+            continue
+        if n.get("label") != sf_p.name:
+            continue
+        if not n.get("id"):
+            continue
+
+        sf_key = _source_key(sf_str, root) if root else sf_str
+        cand_path = sf_key.replace("\\", "/").rstrip("/")
+        basename = cand_path.split("/")[-1]
+
+        headers_by_basename.setdefault(basename, []).append((n, cand_path))
+        headers_by_basename_ci.setdefault(basename.lower(), []).append((n, cand_path))
+
+    if not headers_by_basename:
+        return
+
+    def _shared_dir_prefix_len(p1_parts: list[str], p2_parts: list[str]) -> int:
+        score = 0
+        for a, b in zip(p1_parts, p2_parts):
+            if a == b:
+                score += 1
+            else:
+                break
+        return score
+
+    for e in edges:
+        if e.get("relation") != "imports":
+            continue
+        md = e.get("metadata")
+        if not isinstance(md, dict):
+            continue
+        if md.get("include_kind") != "quoted":
+            continue
+        raw = md.get("raw_include")
+        if not raw or not isinstance(raw, str):
+            continue
+
+        raw_norm = raw.replace("\\", "/").strip()
+        if not raw_norm:
+            continue
+
+        if raw_norm.startswith(("./", "../", "/")):
+            continue
+        try:
+            if Path(raw).is_absolute():
+                continue
+        except Exception:
+            pass
+
+        target_base = raw_norm.split("/")[-1]
+        if not target_base:
+            continue
+
+        exact_cands = headers_by_basename.get(target_base, [])
+        matches = [
+            (node, cand_path) for node, cand_path in exact_cands
+            if cand_path == raw_norm or cand_path.endswith("/" + raw_norm)
+        ]
+
+        if not matches:
+            ci_cands = headers_by_basename_ci.get(target_base.lower(), [])
+            raw_norm_lower = raw_norm.lower()
+            matches = [
+                (node, cand_path) for node, cand_path in ci_cands
+                if cand_path.lower() == raw_norm_lower or cand_path.lower().endswith("/" + raw_norm_lower)
+            ]
+
+        if not matches:
+            continue
+
+        winner_node: dict | None = None
+        if len(matches) == 1:
+            winner_node = matches[0][0]
+        else:
+            imp_sf = str(e.get("source_file", ""))
+            imp_key = _source_key(imp_sf, root) if root else imp_sf
+            imp_path = imp_key.replace("\\", "/").rstrip("/")
+            imp_parts = imp_path.split("/")[:-1]
+
+            scored: list[tuple[int, dict]] = []
+            for node, cand_path in matches:
+                cand_parts = cand_path.split("/")[:-1]
+                score = _shared_dir_prefix_len(imp_parts, cand_parts)
+                scored.append((score, node))
+
+            max_score = max(s[0] for s in scored)
+            top_matches = [node for score, node in scored if score == max_score]
+            if len(top_matches) == 1:
+                winner_node = top_matches[0]
+            else:
+                winner_node = None
+
+        if winner_node is not None:
+            e["target"] = winner_node["id"]
+            e.pop("target_file", None)
+
+
 def _resolve_csharp_qualified_calls(
     per_file: list[dict],
     all_nodes: list[dict],
@@ -9705,6 +9855,15 @@ def extract(
         resolvers=[_KOTLIN_IMPORT_TARGET_RESOLVER],
     )
 
+    # C/C++/ObjC quoted include resolution (#4354): resolve quoted include edges
+    # outside the including file's directory to canonical header file nodes.
+    # Runs after node-ID disambiguation and before import-evidence indexing.
+    try:
+        _resolve_c_include_edges(all_edges, resolution_nodes, root)
+    except Exception as exc:
+        import logging
+        logging.getLogger(__name__).warning("C include resolution failed, skipping: %s", exc)
+
     # Build evidence index from import edges so cross-file calls backed by an
     # explicit import statement can be promoted from INFERRED to EXTRACTED.
     # Direct symbol imports (`import { foo }` / `const { foo } = require()`) are
diff --git a/graphify/extractors/objc.py b/graphify/extractors/objc.py
index ff583cbb5..2668f0093 100644
--- a/graphify/extractors/objc.py
+++ b/graphify/extractors/objc.py
@@ -4,6 +4,7 @@ from __future__ import annotations
 from graphify.extractors.base import _file_stem, _make_id, _read_source_bytes, _read_text
 from graphify.extractors.engine import _cpp_declarator_name, _semantic_reference_edge
 from graphify.extractors.resolution import _resolve_c_include_path
+from graphify.security import sanitize_metadata
 from pathlib import Path
 from typing import Any
 import re
@@ -123,12 +124,15 @@ def extract_objc(path: Path) -> dict:
 
     def add_edge(src: str, tgt: str, relation: str, line: int,
                  confidence: str = "EXTRACTED", weight: float = 1.0,
-                 context: str | None = None) -> None:
+                 context: str | None = None,
+                 metadata: dict | None = None) -> None:
         edge = {"source": src, "target": tgt, "relation": relation,
                 "confidence": confidence, "source_file": str_path,
                 "source_location": f"L{line}", "weight": weight}
         if context:
             edge["context"] = context
+        if metadata:
+            edge["metadata"] = metadata
         edges.append(edge)
 
     file_nid = _make_id(str(path))
@@ -279,7 +283,17 @@ def extract_objc(path: Path) -> dict:
                             else:
                                 module = raw.split("/")[-1].replace(".h", "")
                                 if module:
-                                    add_edge(file_nid, _make_id(module), "imports", line, context="import")
+                                    add_edge(
+                                        file_nid,
+                                        _make_id(module),
+                                        "imports",
+                                        line,
+                                        context="import",
+                                        metadata=sanitize_metadata({
+                                            "raw_include": raw,
+                                            "include_kind": "quoted",
+                                        }),
+                                    )
             return
 
         if t == "module_import":
diff --git a/tests/test_c_include_resolution.py b/tests/test_c_include_resolution.py
new file mode 100644
index 000000000..a03387c53
--- /dev/null
+++ b/tests/test_c_include_resolution.py
@@ -0,0 +1,516 @@
+"""Focused regression tests for C/C++/ObjC quoted include resolution (#4354).
+
+Covers:
+1. Core/Src/adc.c resolving "adc.h" to Core/Inc/adc.h.
+2. Nested harness resolving headers from another directory.
+3. Directory-qualified include (e.g., "sub/util.h").
+4. Unique longest-shared-directory-prefix winner.
+5. Equally scored candidates remaining unresolved (tie).
+6. Exact-case matches taking precedence over case-insensitive alternatives.
+7. Case-insensitive fallback when no exact match exists.
+8. Failed relative paths (./ or ../) remaining unresolved.
+9. Angle-bracket system includes not binding to local same-named files.
+10. Existing sibling include behavior remaining unchanged.
+11. Correct target IDs after .h/.c collision disambiguation.
+12. Cache consistency and incremental extraction after a header is added or removed.
+13. Objective-C parity for quoted #import / #include outside sibling directory.
+"""
+from __future__ import annotations
+
+import os
+from pathlib import Path
+
+import pytest
+import networkx as nx
+
+from graphify.extract import extract
+from graphify.build import build
+
+
+def _real(tmp_path: Path) -> Path:
+    return Path(os.path.realpath(tmp_path))
+
+
+def test_stm32_core_src_resolves_to_core_inc(tmp_path: Path) -> None:
+    """Core/Src/adc.c resolving "adc.h" to Core/Inc/adc.h."""
+    root = _real(tmp_path)
+    src_dir = root / "Core" / "Src"
+    inc_dir = root / "Core" / "Inc"
+    src_dir.mkdir(parents=True, exist_ok=True)
+    inc_dir.mkdir(parents=True, exist_ok=True)
+
+    adc_h = inc_dir / "adc.h"
+    adc_h.write_text("void adc_init(void);\n", encoding="utf-8")
+
+    adc_c = src_dir / "adc.c"
+    adc_c.write_text('#include "adc.h"\nvoid adc_init(void) {}\n', encoding="utf-8")
+
+    result = extract([adc_c, adc_h], root=root, cache_root=root)
+    assert not result.get("error")
+
+    import_edges = [
+        e for e in result["edges"]
+        if e.get("relation") == "imports" and "adc.c" in str(e.get("source_file", ""))
+    ]
+    assert len(import_edges) == 1
+    edge = import_edges[0]
+
+    header_nodes = [
+        n for n in result["nodes"]
+        if "adc.h" in str(n.get("source_file", "")) and n.get("label") == "adc.h"
+    ]
+    assert len(header_nodes) == 1
+    assert edge["target"] == header_nodes[0]["id"]
+    assert "target_file" not in edge
+
+    # Verify build graph produces 0 external stub nodes for adc.h
+    G = build([result], directed=True, root=root)
+    stubs = [
+        n for n, d in G.nodes(data=True)
+        if d.get("external") and d.get("label") == "adc"
+    ]
+    assert not stubs, f"Expected no stub node for adc, found {stubs}"
+    assert G.has_edge(edge["source"], edge["target"])
+
+
+def test_nested_harness_resolves_headers_from_another_dir(tmp_path: Path) -> None:
+    """A nested test harness resolving headers from another directory."""
+    root = _real(tmp_path)
+    tests_dir = root / "tests" / "harness"
+    app_dir = root / "app"
+    tests_dir.mkdir(parents=True, exist_ok=True)
+    app_dir.mkdir(parents=True, exist_ok=True)
+
+    nfc_h = app_dir / "nfc.h"
+    nfc_h.write_text("void nfc_poll(void);\n", encoding="utf-8")
+
+    harness_c = tests_dir / "harness.c"
+    harness_c.write_text('#include "nfc.h"\nint main(void) { return 0; }\n', encoding="utf-8")
+
+    result = extract([harness_c, nfc_h], root=root, cache_root=root)
+    import_edges = [
+        e for e in result["edges"]
+        if e.get("relation") == "imports" and "harness.c" in str(e.get("source_file", ""))
+    ]
+    assert len(import_edges) == 1
+
+    header_nodes = [
+        n for n in result["nodes"]
+        if "nfc.h" in str(n.get("source_file", "")) and n.get("label") == "nfc.h"
+    ]
+    assert len(header_nodes) == 1
+    assert import_edges[0]["target"] == header_nodes[0]["id"]
+
+
+def test_directory_qualified_include(tmp_path: Path) -> None:
+    """Directory-qualified include such as "sub/util.h"."""
+    root = _real(tmp_path)
+    src_dir = root / "src"
+    inc_sub_dir = root / "include" / "sub"
+    other_dir = root / "other"
+    src_dir.mkdir(parents=True, exist_ok=True)
+    inc_sub_dir.mkdir(parents=True, exist_ok=True)
+    other_dir.mkdir(parents=True, exist_ok=True)
+
+    util_matching = inc_sub_dir / "util.h"
+    util_matching.write_text("int sub_util(void);\n", encoding="utf-8")
+
+    util_unrelated = other_dir / "util.h"
+    util_unrelated.write_text("int other_util(void);\n", encoding="utf-8")
+
+    main_c = src_dir / "main.c"
+    main_c.write_text('#include "sub/util.h"\n', encoding="utf-8")
+
+    result = extract([main_c, util_matching, util_unrelated], root=root, cache_root=root)
+    import_edges = [
+        e for e in result["edges"]
+        if e.get("relation") == "imports" and "main.c" in str(e.get("source_file", ""))
+    ]
+    assert len(import_edges) == 1
+
+    matching_header_node = next(
+        n for n in result["nodes"]
+        if "include" in str(n.get("source_file", "")) and n.get("label") == "util.h"
+    )
+    assert import_edges[0]["target"] == matching_header_node["id"]
+
+
+def test_unique_longest_prefix_winner(tmp_path: Path) -> None:
+    """Unique longest-shared-directory-prefix winner resolves."""
+    root = _real(tmp_path)
+    drv_src = root / "components" / "driver" / "src"
+    drv_inc = root / "components" / "driver" / "include"
+    sen_inc = root / "components" / "sensor" / "include"
+    drv_src.mkdir(parents=True, exist_ok=True)
+    drv_inc.mkdir(parents=True, exist_ok=True)
+    sen_inc.mkdir(parents=True, exist_ok=True)
+
+    drv_h = drv_inc / "adc.h"
+    drv_h.write_text("int driver_adc(void);\n", encoding="utf-8")
+
+    sen_h = sen_inc / "adc.h"
+    sen_h.write_text("int sensor_adc(void);\n", encoding="utf-8")
+
+    importer = drv_src / "adc.c"
+    importer.write_text('#include "adc.h"\n', encoding="utf-8")
+
+    result = extract([importer, drv_h, sen_h], root=root, cache_root=root)
+    import_edges = [
+        e for e in result["edges"]
+        if e.get("relation") == "imports" and "adc.c" in str(e.get("source_file", ""))
+    ]
+    assert len(import_edges) == 1
+
+    drv_header_node = next(
+        n for n in result["nodes"]
+        if "driver" in str(n.get("source_file", "")) and n.get("label") == "adc.h"
+    )
+    assert import_edges[0]["target"] == drv_header_node["id"]
+
+
+def test_equally_scored_candidates_remain_unresolved(tmp_path: Path) -> None:
+    """Equally scored candidates remain unresolved (tie fails closed)."""
+    root = _real(tmp_path)
+    test_dir = root / "test"
+    mod_a = root / "module_a"
+    mod_b = root / "module_b"
+    test_dir.mkdir(parents=True, exist_ok=True)
+    mod_a.mkdir(parents=True, exist_ok=True)
+    mod_b.mkdir(parents=True, exist_ok=True)
+
+    util_a = mod_a / "util.h"
+    util_a.write_text("int util_a(void);\n", encoding="utf-8")
+
+    util_b = mod_b / "util.h"
+    util_b.write_text("int util_b(void);\n", encoding="utf-8")
+
+    harness = test_dir / "harness.c"
+    harness.write_text('#include "util.h"\n', encoding="utf-8")
+
+    result = extract([harness, util_a, util_b], root=root, cache_root=root)
+    import_edges = [
+        e for e in result["edges"]
+        if e.get("relation") == "imports" and "harness.c" in str(e.get("source_file", ""))
+    ]
+    assert len(import_edges) == 1
+    edge = import_edges[0]
+
+    # Target remains the fallback stem
+    assert edge["target"] == "util"
+
+    # Build creates an external stub node because of the tie
+    G = build([result], directed=True, root=root)
+    stub_data = G.nodes.get("util")
+    assert stub_data is not None
+    assert stub_data.get("external") is True
+
+
+def test_exact_case_precedence_over_case_insensitive(tmp_path: Path) -> None:
+    """Exact-case match takes precedence over case-insensitive alternatives."""
+    root = _real(tmp_path)
+    src_dir = root / "src"
+    inc1_dir = root / "inc1"
+    inc2_dir = root / "inc2"
+    src_dir.mkdir(parents=True, exist_ok=True)
+    inc1_dir.mkdir(parents=True, exist_ok=True)
+    inc2_dir.mkdir(parents=True, exist_ok=True)
+
+    exact_h = inc1_dir / "adc.h"
+    exact_h.write_text("int exact_adc(void);\n", encoding="utf-8")
+
+    upper_h = inc2_dir / "ADC.h"
+    upper_h.write_text("int upper_adc(void);\n", encoding="utf-8")
+
+    main_c = src_dir / "main.c"
+    main_c.write_text('#include "adc.h"\n', encoding="utf-8")
+
+    result = extract([main_c, exact_h, upper_h], root=root, cache_root=root)
+    import_edges = [
+        e for e in result["edges"]
+        if e.get("relation") == "imports" and "main.c" in str(e.get("source_file", ""))
+    ]
+    assert len(import_edges) == 1
+
+    exact_node = next(
+        n for n in result["nodes"]
+        if "inc1" in str(n.get("source_file", "")) and n.get("label") == "adc.h"
+    )
+    assert import_edges[0]["target"] == exact_node["id"]
+
+
+def test_case_insensitive_fallback_when_no_exact_match(tmp_path: Path) -> None:
+    """Case-insensitive fallback succeeds when no exact match exists."""
+    root = _real(tmp_path)
+    src_dir = root / "src"
+    inc_dir = root / "inc"
+    src_dir.mkdir(parents=True, exist_ok=True)
+    inc_dir.mkdir(parents=True, exist_ok=True)
+
+    upper_h = inc_dir / "ADC.h"
+    upper_h.write_text("int upper_adc(void);\n", encoding="utf-8")
+
+    main_c = src_dir / "main.c"
+    main_c.write_text('#include "adc.h"\n', encoding="utf-8")
+
+    result = extract([main_c, upper_h], root=root, cache_root=root)
+    import_edges = [
+        e for e in result["edges"]
+        if e.get("relation") == "imports" and "main.c" in str(e.get("source_file", ""))
+    ]
+    assert len(import_edges) == 1
+
+    upper_node = next(
+        n for n in result["nodes"]
+        if "inc" in str(n.get("source_file", "")) and n.get("label") == "ADC.h"
+    )
+    assert import_edges[0]["target"] == upper_node["id"]
+
+
+def test_failed_relative_path_remains_unresolved(tmp_path: Path) -> None:
+    """Failed relative paths (./ or ../) do not bind to unrelated corpus files."""
+    root = _real(tmp_path)
+    src_dir = root / "src"
+    other_dir = root / "other"
+    src_dir.mkdir(parents=True, exist_ok=True)
+    other_dir.mkdir(parents=True, exist_ok=True)
+
+    unrelated_h1 = other_dir / "missing.h"
+    unrelated_h1.write_text("int missing1(void);\n", encoding="utf-8")
+
+    unrelated_h2 = other_dir / "missing_parent.h"
+    unrelated_h2.write_text("int missing2(void);\n", encoding="utf-8")
+
+    other2_dir = root / "other2"
+    other2_dir.mkdir(parents=True, exist_ok=True)
+    unrelated_h1b = other2_dir / "missing.h"
+    unrelated_h1b.write_text("int missing1b(void);\n", encoding="utf-8")
+
+    unrelated_h2b = other2_dir / "missing_parent.h"
+    unrelated_h2b.write_text("int missing2b(void);\n", encoding="utf-8")
+
+    main_c = src_dir / "main.c"
+    main_c.write_text(
+        '#include "./missing.h"\n'
+        '#include "../missing_parent.h"\n'
+        'int main(void) { return 0; }\n',
+        encoding="utf-8",
+    )
+
+    result = extract(
+        [main_c, unrelated_h1, unrelated_h2, unrelated_h1b, unrelated_h2b],
+        root=root,
+        cache_root=root,
+    )
+    import_edges = [
+        e for e in result["edges"]
+        if e.get("relation") == "imports" and "main.c" in str(e.get("source_file", ""))
+    ]
+    assert len(import_edges) == 2
+
+    other_node_ids = {
+        n["id"] for n in result["nodes"]
+        if "other" in str(n.get("source_file", ""))
+    }
+
+    # Neither edge should resolve to any of the "other" files
+    for edge in import_edges:
+        assert edge["target"] not in other_node_ids
+        assert edge["target"] in ("missing", "missing_parent")
+
+    G = build([result], directed=True, root=root)
+    for stub_id in ("missing", "missing_parent"):
+        data = G.nodes.get(stub_id)
+        assert data is not None
+        assert data.get("external") is True
+
+
+def test_angle_bracket_system_includes_not_bound_locally(tmp_path: Path) -> None:
+    """Angle-bracket system includes do not bind to local corpus files."""
+    root = _real(tmp_path)
+    src_dir = root / "src"
+    inc1_dir = root / "include1"
+    inc2_dir = root / "include2"
+    src_dir.mkdir(parents=True, exist_ok=True)
+    inc1_dir.mkdir(parents=True, exist_ok=True)
+    inc2_dir.mkdir(parents=True, exist_ok=True)
+
+    local_stdio1 = inc1_dir / "stdio.h"
+    local_stdio1.write_text("// local fake stdio 1\n", encoding="utf-8")
+
+    local_stdio2 = inc2_dir / "stdio.h"
+    local_stdio2.write_text("// local fake stdio 2\n", encoding="utf-8")
+
+    main_c = src_dir / "main.c"
+    main_c.write_text('#include <stdio.h>\nint main(void) { return 0; }\n', encoding="utf-8")
+
+    result = extract([main_c, local_stdio1, local_stdio2], root=root, cache_root=root)
+    import_edges = [
+        e for e in result["edges"]
+        if e.get("relation") == "imports" and "main.c" in str(e.get("source_file", ""))
+    ]
+    assert len(import_edges) == 1
+    edge = import_edges[0]
+
+    local_stdio_ids = {
+        n["id"] for n in result["nodes"]
+        if "stdio.h" in str(n.get("source_file", ""))
+    }
+    assert edge["target"] not in local_stdio_ids
+    assert edge["target"] == "stdio"
+
+    G = build([result], directed=True, root=root)
+    stub_data = G.nodes.get("stdio")
+    assert stub_data is not None
+    assert stub_data.get("external") is True
+
+
+def test_existing_sibling_include_behavior_unchanged(tmp_path: Path) -> None:
+    """Existing sibling include resolution remains prioritized and unchanged."""
+    root = _real(tmp_path)
+    src_dir = root / "src"
+    other_dir = root / "other"
+    src_dir.mkdir(parents=True, exist_ok=True)
+    other_dir.mkdir(parents=True, exist_ok=True)
+
+    sibling_h = src_dir / "helper.h"
+    sibling_h.write_text("int sibling_helper(void);\n", encoding="utf-8")
+
+    other_h = other_dir / "helper.h"
+    other_h.write_text("int other_helper(void);\n", encoding="utf-8")
+
+    main_c = src_dir / "main.c"
+    main_c.write_text('#include "helper.h"\n', encoding="utf-8")
+
+    result = extract([main_c, sibling_h, other_h], root=root, cache_root=root)
+    import_edges = [
+        e for e in result["edges"]
+        if e.get("relation") == "imports" and "main.c" in str(e.get("source_file", ""))
+    ]
+    assert len(import_edges) == 1
+
+    sibling_node = next(
+        n for n in result["nodes"]
+        if "src" in str(n.get("source_file", "")) and n.get("label") == "helper.h"
+    )
+    assert import_edges[0]["target"] == sibling_node["id"]
+
+
+def test_collision_disambiguated_header_and_c_source(tmp_path: Path) -> None:
+    """Header and C source with identical stem resolve to the header, not source."""
+    root = _real(tmp_path)
+    app_dir = root / "app"
+    test_dir = root / "test"
+    app_dir.mkdir(parents=True, exist_ok=True)
+    test_dir.mkdir(parents=True, exist_ok=True)
+
+    nfc_h = app_dir / "nfc.h"
+    nfc_h.write_text("void nfc_run(void);\n", encoding="utf-8")
+
+    nfc_c = app_dir / "nfc.c"
+    nfc_c.write_text('#include "nfc.h"\nvoid nfc_run(void) {}\n', encoding="utf-8")
+
+    main_c = test_dir / "main.c"
+    main_c.write_text('#include "nfc.h"\n', encoding="utf-8")
+
+    result = extract([main_c, nfc_h, nfc_c], root=root, cache_root=root)
+
+    header_node = next(
+        n for n in result["nodes"]
+        if "nfc.h" in str(n.get("source_file", "")) and n.get("label") == "nfc.h"
+    )
+    source_node = next(
+        n for n in result["nodes"]
+        if "nfc.c" in str(n.get("source_file", "")) and n.get("label") == "nfc.c"
+    )
+
+    # Disambiguation must separate .h and .c
+    assert header_node["id"] != source_node["id"]
+
+    import_edge = next(
+        e for e in result["edges"]
+        if e.get("relation") == "imports" and "main.c" in str(e.get("source_file", ""))
+    )
+    assert import_edge["target"] == header_node["id"]
+
+
+def test_cache_consistency_when_header_added_and_removed(tmp_path: Path) -> None:
+    """Cache consistency: resolution dynamically reacts when header is added or removed."""
+    root = _real(tmp_path)
+    cache_dir = root / ".cache"
+    src_dir = root / "src"
+    inc_dir = root / "inc"
+    src_dir.mkdir(parents=True, exist_ok=True)
+    inc_dir.mkdir(parents=True, exist_ok=True)
+
+    main_c = src_dir / "main.c"
+    main_c.write_text('#include "util.h"\n', encoding="utf-8")
+
+    # Pass 1: No util.h in project
+    r1 = extract([main_c], root=root, cache_root=cache_dir)
+    edge1 = next(e for e in r1["edges"] if e.get("relation") == "imports")
+    assert edge1["target"] == "util"
+
+    # Pass 2: Add inc/util.h. Even with main.c cached, whole-graph pass resolves it!
+    util_h = inc_dir / "util.h"
+    util_h.write_text("int util_func(void);\n", encoding="utf-8")
+
+    r2 = extract([main_c, util_h], root=root, cache_root=cache_dir)
+    edge2 = next(
+        e for e in r2["edges"]
+        if e.get("relation") == "imports" and "main.c" in str(e.get("source_file", ""))
+    )
+    header_node = next(
+        n for n in r2["nodes"]
+        if "util.h" in str(n.get("source_file", "")) and n.get("label") == "util.h"
+    )
+    assert edge2["target"] == header_node["id"]
+
+    # Pass 3: Remove inc/util.h. It should revert to unresolved stem
+    util_h.unlink()
+    r3 = extract([main_c], root=root, cache_root=cache_dir)
+    edge3 = next(e for e in r3["edges"] if e.get("relation") == "imports")
+    assert edge3["target"] == "util"
+
+
+def test_objc_quoted_include_and_import_parity(tmp_path: Path) -> None:
+    """Objective-C parity: quoted #import / #include outside sibling resolves to header."""
+    root = _real(tmp_path)
+    src_dir = root / "App"
+    inc_dir = root / "Shared" / "Headers"
+    src_dir.mkdir(parents=True, exist_ok=True)
+    inc_dir.mkdir(parents=True, exist_ok=True)
+
+    helper_h = inc_dir / "Helper.h"
+    helper_h.write_text(
+        "@interface Helper : NSObject\n"
+        "- (void)help;\n"
+        "@end\n",
+        encoding="utf-8",
+    )
+
+    app_m = src_dir / "AppDelegate.m"
+    app_m.write_text(
+        '#import "Helper.h"\n'
+        '#import <Foundation/Foundation.h>\n'
+        '@implementation AppDelegate\n'
+        '@end\n',
+        encoding="utf-8",
+    )
+
+    result = extract([app_m, helper_h], root=root, cache_root=root)
+    import_edges = [
+        e for e in result["edges"]
+        if e.get("relation") == "imports" and "AppDelegate.m" in str(e.get("source_file", ""))
+    ]
+    assert len(import_edges) == 2
+
+    helper_node = next(
+        n for n in result["nodes"]
+        if "Helper.h" in str(n.get("source_file", "")) and n.get("label") == "Helper.h"
+    )
+
+    helper_edge = next(e for e in import_edges if e["target"] == helper_node["id"])
+    assert helper_edge is not None
+
+    foundation_edge = next(e for e in import_edges if e["target"] == "foundation")
+    assert foundation_edge is not None