diff --git a/gitnexus/src/core/ingestion/languages/c/import-target.ts b/gitnexus/src/core/ingestion/languages/c/import-target.ts
index 0cb9c2fb4..495846030 100644
--- a/gitnexus/src/core/ingestion/languages/c/import-target.ts
+++ b/gitnexus/src/core/ingestion/languages/c/import-target.ts
@@ -1,5 +1,54 @@
 import { dirname, join } from 'path';
 
+/**
+ * A workspace file path pre-decomposed for the suffix-match fallback:
+ * `original` is returned verbatim (preserving the prior `bestMatch = filePath`
+ * contract); `normalized` and `depth` are precomputed so the hot path does no
+ * per-element regex/`split`.
+ */
+interface CSuffixCandidate {
+  original: string;
+  normalized: string;
+  depth: number;
+}
+
+/**
+ * Per-pass memo: workspace paths bucketed by basename (last path segment),
+ * keyed on the `allFilePaths` set identity.
+ *
+ * `resolveCImportTarget` is called once per (quoted) C/C++ `#include` with the
+ * same `allFilePaths` set per pass (the augmented set is itself memoized in
+ * the C resolver). The old suffix-match fallback scanned ALL workspace paths
+ * per include — with a per-element `.replace`/`.split` and no early exit
+ * (the fewest-path-components tie-break forces a full scan) — i.e.
+ * O(R_suffix × (F+H)). A path can satisfy `endsWith('/'+target)` (or equal
+ * the target) ONLY IF its basename equals the target's last segment, so we
+ * pre-bucket by basename once (O(F+H), `normalized`/`depth` precomputed) and
+ * the fallback inspects a single small bucket → O(F+H) build + ~O(1)/include.
+ * `WeakMap`-keyed so it is reclaimed with the pass (no cross-pass staleness).
+ * Shared by C and C++ (`resolveCppImportTarget` delegates here).
+ */
+const suffixIndexByPaths = new WeakMap<ReadonlySet<string>, Map<string, CSuffixCandidate[]>>();
+
+function suffixIndex(allFilePaths: ReadonlySet<string>): Map<string, CSuffixCandidate[]> {
+  let index = suffixIndexByPaths.get(allFilePaths);
+  if (index === undefined) {
+    index = new Map<string, CSuffixCandidate[]>();
+    for (const original of allFilePaths) {
+      const normalized = original.replace(/\\/g, '/');
+      const basename = normalized.slice(normalized.lastIndexOf('/') + 1);
+      let bucket = index.get(basename);
+      if (bucket === undefined) {
+        bucket = [];
+        index.set(basename, bucket);
+      }
+      bucket.push({ original, normalized, depth: normalized.split('/').length });
+    }
+    suffixIndexByPaths.set(allFilePaths, index);
+  }
+  return index;
+}
+
 /**
  * Resolve a C #include path to a file in the workspace.
  *
@@ -41,21 +90,31 @@ export function resolveCImportTarget(
   // Exact match (path as-is in the workspace)
   if (allFilePaths.has(normalizedTarget)) return normalizedTarget;
 
-  // Suffix match: find files ending with /targetRaw or equal to targetRaw
+  // Suffix match: find files ending with /targetRaw or equal to targetRaw.
+  // A path can only match `=== normalizedTarget` or `endsWith('/'+target)` if
+  // its basename equals the target's last segment, so we inspect only that
+  // basename bucket (built once per pass) instead of scanning every workspace
+  // path. Match condition + tie-break (fewest path components, then
+  // lexicographic on the normalized path) are byte-identical to the prior scan.
   const suffix = '/' + normalizedTarget;
+  const targetBasename = normalizedTarget.slice(normalizedTarget.lastIndexOf('/') + 1);
+  const bucket = suffixIndex(allFilePaths).get(targetBasename);
+  if (bucket === undefined) return null;
+
   let bestMatch: string | null = null;
   let bestDepth = Infinity;
   let bestNormalized = '';
 
-  for (const filePath of allFilePaths) {
-    const normalized = filePath.replace(/\\/g, '/');
-    if (normalized === normalizedTarget || normalized.endsWith(suffix)) {
+  for (const cand of bucket) {
+    if (cand.normalized === normalizedTarget || cand.normalized.endsWith(suffix)) {
       // Prefer shortest path (closest match)
-      const depth = normalized.split('/').length;
-      if (depth < bestDepth || (depth === bestDepth && normalized < bestNormalized)) {
-        bestDepth = depth;
-        bestMatch = filePath;
-        bestNormalized = normalized;
+      if (
+        cand.depth < bestDepth ||
+        (cand.depth === bestDepth && cand.normalized < bestNormalized)
+      ) {
+        bestDepth = cand.depth;
+        bestMatch = cand.original;
+        bestNormalized = cand.normalized;
       }
     }
   }
diff --git a/gitnexus/src/core/ingestion/languages/c/scope-resolver.ts b/gitnexus/src/core/ingestion/languages/c/scope-resolver.ts
index d2e0e17f7..cb4a6424f 100644
--- a/gitnexus/src/core/ingestion/languages/c/scope-resolver.ts
+++ b/gitnexus/src/core/ingestion/languages/c/scope-resolver.ts
@@ -9,6 +9,42 @@ import { scanHeaderFiles } from './header-scan.js';
 import { expandCWildcardNames, isStaticName, clearStaticNames } from './static-linkage.js';
 import { applyCStaticLinkageSideChannel } from './capture-side-channel.js';
 
+/**
+ * Per-pass memo of the augmented `#include`-resolution file set
+ * (`allFilePaths` ∪ header `.h` paths), keyed on the two stable source sets.
+ *
+ * `resolveImportTarget` is called once per C `#include`; the old code rebuilt
+ * a fresh ~F-entry `Set` on EVERY call (O(R × (F+H)) inserts + GC churn) and,
+ * worse, defeated `resolveCImportTarget`'s own per-set suffix-index memo by
+ * handing it a new set identity each time. Both `allFilePaths` (built once in
+ * scope-resolution `run.ts`) and the header set (`loadResolutionConfig`
+ * result) are stable per pass, so the union is built once and reused.
+ * `WeakMap`-keyed → reclaimed with the pass (no cross-pass staleness).
+ */
+const augmentedPathsByPass = new WeakMap<
+  ReadonlySet<string>,
+  WeakMap<ReadonlySet<string>, ReadonlySet<string>>
+>();
+
+function augmentedFilePaths(
+  allFilePaths: ReadonlySet<string>,
+  headerPaths: ReadonlySet<string>,
+): ReadonlySet<string> {
+  let byHeaders = augmentedPathsByPass.get(allFilePaths);
+  if (byHeaders === undefined) {
+    byHeaders = new WeakMap();
+    augmentedPathsByPass.set(allFilePaths, byHeaders);
+  }
+  let augmented = byHeaders.get(headerPaths);
+  if (augmented === undefined) {
+    const set = new Set(allFilePaths);
+    for (const h of headerPaths) set.add(h);
+    augmented = set;
+    byHeaders.set(headerPaths, augmented);
+  }
+  return augmented;
+}
+
 /**
  * C `ScopeResolver` registered in `SCOPE_RESOLVERS` and consumed by
  * the generic `runScopeResolution` orchestrator (RFC #909 Ring 3).
@@ -55,9 +91,11 @@ export const cScopeResolver: ScopeResolver = {
     // targets .h files classified as C++ in language detection.
     const headerPaths = resolutionConfig as ReadonlySet<string> | undefined;
     if (headerPaths !== undefined && headerPaths.size > 0) {
-      const augmented = new Set(allFilePaths);
-      for (const h of headerPaths) augmented.add(h);
-      return resolveCImportTarget(targetRaw, fromFile, augmented);
+      return resolveCImportTarget(
+        targetRaw,
+        fromFile,
+        augmentedFilePaths(allFilePaths, headerPaths),
+      );
     }
     return resolveCImportTarget(targetRaw, fromFile, allFilePaths);
   },
diff --git a/gitnexus/src/core/ingestion/languages/c/static-linkage.ts b/gitnexus/src/core/ingestion/languages/c/static-linkage.ts
index df02c3312..2cc195205 100644
--- a/gitnexus/src/core/ingestion/languages/c/static-linkage.ts
+++ b/gitnexus/src/core/ingestion/languages/c/static-linkage.ts
@@ -46,6 +46,41 @@ export function clearStaticNames(): void {
   staticNames.clear();
 }
 
+/**
+ * Per-pass memo: `moduleScope` → owning `ParsedFile`, keyed on the
+ * `parsedFiles` array identity.
+ *
+ * The shared finalize Phase-4 loop calls `expandsWildcardTo`
+ * (→ `expandCWildcardNames`) ONCE PER RESOLVED `#include` edge, every time
+ * with the SAME `parsedFiles` reference (wired at scope-resolution
+ * `run.ts` — `allFilePaths`/`parsedFiles` are built once per pass). The old
+ * `parsedFiles.find(...)` therefore did a full O(F) scan per edge →
+ * O(R_include × F) overall; at Linux-kernel scale (F ≈ 63k C files, tens of
+ * thousands of resolved includes) that is ~10^10+ comparisons on a single
+ * thread — the dominant term in the scope-resolution finalize grind.
+ *
+ * Building the lookup once collapses it to O(R_include + F). `WeakMap`-keyed
+ * on the array so the index is reclaimed with the pass — no cross-pass
+ * staleness (mirrors the {@link clearStaticNames} discipline for server-mode
+ * / multi-repo reuse), and a fresh array transparently rebuilds.
+ */
+const moduleScopeIndexByPass = new WeakMap<readonly ParsedFile[], Map<ScopeId, ParsedFile>>();
+
+function moduleScopeIndex(parsedFiles: readonly ParsedFile[]): Map<ScopeId, ParsedFile> {
+  let index = moduleScopeIndexByPass.get(parsedFiles);
+  if (index === undefined) {
+    index = new Map<ScopeId, ParsedFile>();
+    // First-wins to preserve `Array.find` semantics (returns the first match).
+    // `moduleScope` is unique per file in practice, so collisions are absent;
+    // the guard only formalises identical behaviour to the prior `.find`.
+    for (const p of parsedFiles) {
+      if (!index.has(p.moduleScope)) index.set(p.moduleScope, p);
+    }
+    moduleScopeIndexByPass.set(parsedFiles, index);
+  }
+  return index;
+}
+
 /**
  * Return the names visible through a C wildcard import (`#include`).
  * All module-scope defs from the target file are visible EXCEPT those
@@ -55,7 +90,7 @@ export function expandCWildcardNames(
   targetModuleScope: ScopeId,
   parsedFiles: readonly ParsedFile[],
 ): readonly string[] {
-  const target = parsedFiles.find((p) => p.moduleScope === targetModuleScope);
+  const target = moduleScopeIndex(parsedFiles).get(targetModuleScope);
   if (target === undefined) return [];
 
   const seen = new Set<string>();
diff --git a/gitnexus/src/core/ingestion/languages/cpp/file-local-linkage.ts b/gitnexus/src/core/ingestion/languages/cpp/file-local-linkage.ts
index 09461d134..c6b383bf0 100644
--- a/gitnexus/src/core/ingestion/languages/cpp/file-local-linkage.ts
+++ b/gitnexus/src/core/ingestion/languages/cpp/file-local-linkage.ts
@@ -276,11 +276,37 @@ export function isCppDefGloballyVisible(filePath: string, nodeId: string): boole
  * does, mirror this filter or harden registration so class/namespace
  * members never enter `localDefs` unqualified.
  */
+/**
+ * Per-pass memo: `moduleScope` → owning `ParsedFile`, keyed on the
+ * `parsedFiles` array identity. The shared finalize Phase-4 loop calls
+ * `expandsWildcardTo` (→ this) ONCE PER RESOLVED `#include` edge with the same
+ * `parsedFiles` reference; the old `parsedFiles.find(...)` was therefore O(F)
+ * per edge → O(R·F) overall (at kernel scale the ~25–30k `.h` headers are
+ * classified C++, so this fires hard — the C twin in `c/static-linkage.ts`).
+ * Building the lookup once collapses it to O(R+F). `WeakMap`-keyed so it is
+ * reclaimed with the pass (no cross-pass staleness; mirrors
+ * {@link clearFileLocalNames}).
+ */
+const moduleScopeIndexByPass = new WeakMap<readonly ParsedFile[], Map<ScopeId, ParsedFile>>();
+
+function moduleScopeIndex(parsedFiles: readonly ParsedFile[]): Map<ScopeId, ParsedFile> {
+  let index = moduleScopeIndexByPass.get(parsedFiles);
+  if (index === undefined) {
+    index = new Map<ScopeId, ParsedFile>();
+    // First-wins to preserve `Array.find` semantics (returns the first match).
+    for (const p of parsedFiles) {
+      if (!index.has(p.moduleScope)) index.set(p.moduleScope, p);
+    }
+    moduleScopeIndexByPass.set(parsedFiles, index);
+  }
+  return index;
+}
+
 export function expandCppWildcardNames(
   targetModuleScope: ScopeId,
   parsedFiles: readonly ParsedFile[],
 ): readonly string[] {
-  const target = parsedFiles.find((p) => p.moduleScope === targetModuleScope);
+  const target = moduleScopeIndex(parsedFiles).get(targetModuleScope);
   if (target === undefined) return [];
 
   // Build nodeId → owning Scope map from the structural scope tree.
diff --git a/gitnexus/src/core/ingestion/languages/cpp/scope-resolver.ts b/gitnexus/src/core/ingestion/languages/cpp/scope-resolver.ts
index 725106c3d..5e24e292d 100644
--- a/gitnexus/src/core/ingestion/languages/cpp/scope-resolver.ts
+++ b/gitnexus/src/core/ingestion/languages/cpp/scope-resolver.ts
@@ -43,6 +43,40 @@ import {
   populateCppUserDefinedConversions,
 } from './user-defined-conversions.js';
 
+/**
+ * Per-pass memo of the augmented `#include`-resolution file set
+ * (`allFilePaths` ∪ header paths), keyed on the two stable source sets.
+ * `resolveImportTarget` is called once per C++ `#include`; the old code rebuilt
+ * a fresh ~F-entry `Set` on every call AND defeated the shared
+ * `resolveCImportTarget` suffix-index memo (in `c/import-target.ts`) by handing
+ * it a new set identity each time. Both inputs are stable per pass, so the
+ * union is built once and reused. `WeakMap`-keyed → reclaimed with the pass.
+ * (Twin of the C resolver's `augmentedFilePaths`.)
+ */
+const augmentedPathsByPass = new WeakMap<
+  ReadonlySet<string>,
+  WeakMap<ReadonlySet<string>, ReadonlySet<string>>
+>();
+
+function augmentedFilePaths(
+  allFilePaths: ReadonlySet<string>,
+  headerPaths: ReadonlySet<string>,
+): ReadonlySet<string> {
+  let byHeaders = augmentedPathsByPass.get(allFilePaths);
+  if (byHeaders === undefined) {
+    byHeaders = new WeakMap();
+    augmentedPathsByPass.set(allFilePaths, byHeaders);
+  }
+  let augmented = byHeaders.get(headerPaths);
+  if (augmented === undefined) {
+    const set = new Set(allFilePaths);
+    for (const h of headerPaths) set.add(h);
+    augmented = set;
+    byHeaders.set(headerPaths, augmented);
+  }
+  return augmented;
+}
+
 /**
  * C++ `ScopeResolver` registered in `SCOPE_RESOLVERS` and consumed by
  * the generic `runScopeResolution` orchestrator (RFC #909 Ring 3).
@@ -79,9 +113,11 @@ export const cppScopeResolver: ScopeResolver = {
     // detection but are importable from .cpp files via #include.
     const headerPaths = resolutionConfig as ReadonlySet<string> | undefined;
     if (headerPaths !== undefined && headerPaths.size > 0) {
-      const augmented = new Set(allFilePaths);
-      for (const h of headerPaths) augmented.add(h);
-      return resolveCppImportTarget(targetRaw, fromFile, augmented);
+      return resolveCppImportTarget(
+        targetRaw,
+        fromFile,
+        augmentedFilePaths(allFilePaths, headerPaths),
+      );
     }
     return resolveCppImportTarget(targetRaw, fromFile, allFilePaths);
   },