diff --git a/__tests__/dead-code.test.ts b/__tests__/dead-code.test.ts
index d946c463d..c0fd98f81 100644
--- a/__tests__/dead-code.test.ts
+++ b/__tests__/dead-code.test.ts
@@ -20,7 +20,7 @@
  * Every one of those must be OFF the list, and the reason must be counted.
  */
 
-import { describe, it, expect, beforeAll, afterAll } from 'vitest';
+import { describe, it, expect, beforeAll, afterAll, beforeEach, afterEach } from 'vitest';
 import * as http from 'http';
 import * as fs from 'fs';
 import * as os from 'os';
@@ -483,3 +483,52 @@ describe('GET /api/map — generated files and islands', () => {
     }
   });
 });
+
+describe('an ancestor outside the index (#1973)', () => {
+  let root: string;
+  let graph: CodeGraph;
+
+  beforeEach(async () => {
+    root = fs.mkdtempSync(path.join(os.tmpdir(), 'cg-deadcode-external-'));
+    write(
+      root,
+      'src/clock.tsx',
+      `import React from 'react';
+import { Transform } from 'stream';
+import { OnModuleInit } from '@nestjs/common';
+export class Clock extends React.Component { componentDidMount() {} render() { return null; } }
+export class Upper extends Transform { _transform(c, e, cb) { cb(null, c); } }
+export class Boot implements OnModuleInit { onModuleInit() {} }
+export class Ticker extends Clock { componentDidUpdate() {} }
+export class Third extends Ticker { componentWillUnmount() {} componentDidCatch() {} }
+export class Plain { neverCalledMember() {} }
+function reallyUnused() {}
+`
+    );
+    write(root, 'src/main.ts', `import { Clock, Upper, Boot, Ticker, Third, Plain } from './clock';\nexport const all = [Clock, Upper, Boot, Ticker, Third, Plain];\n`);
+    graph = CodeGraph.initSync(root, { config: { include: ['src/**/*.ts', 'src/**/*.tsx'], exclude: [] } });
+    await graph.indexAll();
+  }, 60_000);
+
+  afterEach(() => {
+    graph?.close();
+    if (root) fs.rmSync(root, { recursive: true, force: true });
+  });
+
+  it('does not list members a framework base class calls', () => {
+    const report = buildDeadCodeReport(graph);
+    for (const name of ['componentDidMount', 'componentWillUnmount', 'render', '_transform', 'onModuleInit']) {
+      expect(names(report)).not.toContain(name);
+    }
+    // A project class whose own ancestor extends an external base inherits the doubt.
+    expect(names(report)).not.toContain('componentDidUpdate');
+    expect(names(report)).not.toContain('componentDidCatch');
+    expect(report.excluded.overriding).toBeGreaterThanOrEqual(7);
+  });
+
+  it('still lists what nothing reaches outside such a class', () => {
+    const report = buildDeadCodeReport(graph);
+    expect(names(report)).toContain('reallyUnused');
+    expect(names(report)).toContain('neverCalledMember');
+  });
+});
diff --git a/__tests__/unresolved-supertype-query.test.ts b/__tests__/unresolved-supertype-query.test.ts
new file mode 100644
index 000000000..6042d09d5
--- /dev/null
+++ b/__tests__/unresolved-supertype-query.test.ts
@@ -0,0 +1,49 @@
+import { describe, it, expect, beforeEach, afterEach } from 'vitest';
+import * as fs from 'fs';
+import * as os from 'os';
+import * as path from 'path';
+import { DatabaseConnection } from '../src/db';
+import { QueryBuilder } from '../src/db/queries';
+import type { Node } from '../src/types';
+
+function node(id: string): Node {
+  return { id, kind: 'class', name: id, qualifiedName: id, filePath: 'fixture.ts',
+    language: 'typescript', startLine: 1, endLine: 1, startColumn: 0, endColumn: 0, updatedAt: Date.now() };
+}
+
+describe('getUnresolvedSupertypeSourcesAmong (#1973)', () => {
+  let root: string;
+  let db: DatabaseConnection;
+  let queries: QueryBuilder;
+
+  beforeEach(() => {
+    root = fs.mkdtempSync(path.join(os.tmpdir(), 'cg-supertype-query-'));
+    db = DatabaseConnection.initialize(path.join(root, 'test.db'));
+    queries = new QueryBuilder(db.getDb());
+  });
+
+  afterEach(() => {
+    db?.close();
+    fs.rmSync(root, { recursive: true, force: true });
+  });
+
+  it('selects only requested inheritance sources, including pending and failed refs', () => {
+    for (const [id, kind] of [['base', 'extends'], ['contract', 'implements'], ['call', 'calls'], ['other', 'extends']] as const) {
+      queries.insertNode(node(id));
+      queries.insertUnresolvedRef({ fromNodeId: id, referenceName: 'External', referenceKind: kind, line: 1, column: 0 });
+    }
+    queries.markReferencesFailed([{ fromNodeId: 'contract', referenceName: 'External', referenceKind: 'implements' }]);
+    expect(queries.getUnresolvedSupertypeSourcesAmong(['base', 'contract', 'call', 'missing', 'base']))
+      .toEqual(new Set(['base', 'contract']));
+    expect(queries.getUnresolvedSupertypeSourcesAmong([])).toEqual(new Set());
+  });
+
+  it('keeps sources across chunk boundaries', () => {
+    const ids = Array.from({ length: 1001 }, (_, i) => `class-${i}`);
+    for (const id of [ids[0], ids[500], ids[1000]]) {
+      queries.insertNode(node(id));
+      queries.insertUnresolvedRef({ fromNodeId: id, referenceName: 'External', referenceKind: 'extends', line: 1, column: 0 });
+    }
+    expect(queries.getUnresolvedSupertypeSourcesAmong(ids)).toEqual(new Set([ids[0], ids[500], ids[1000]]));
+  });
+});
diff --git a/src/db/queries.ts b/src/db/queries.ts
index 2b240c094..62fe46476 100644
--- a/src/db/queries.ts
+++ b/src/db/queries.ts
@@ -2124,6 +2124,31 @@ export class QueryBuilder {
     return found;
   }
 
+  /**
+   * Which of `nodeIds` extend or implement a type the resolver could not follow.
+   * An ancestor outside the index (`React.Component`, `stream.Transform`, a
+   * framework interface) leaves no edge, only this `extends` / `implements`
+   * row, so it is the one record that such an ancestor exists (#1973).
+   * Chunked probe over `idx_unresolved_from_node`.
+   */
+  getUnresolvedSupertypeSourcesAmong(nodeIds: Iterable<string>): Set<string> {
+    const unique = [...new Set(nodeIds)];
+    const found = new Set<string>();
+    for (let i = 0; i < unique.length; i += SQLITE_PARAM_CHUNK_SIZE) {
+      const chunk = unique.slice(i, i + SQLITE_PARAM_CHUNK_SIZE);
+      const placeholders = chunk.map(() => '?').join(',');
+      const rows = this.db
+        .prepare(
+          `SELECT DISTINCT from_node_id AS id FROM unresolved_refs
+            WHERE from_node_id IN (${placeholders})
+              AND reference_kind IN ('extends', 'implements')`
+        )
+        .all(...chunk) as Array<{ id: string }>;
+      for (const row of rows) found.add(row.id);
+    }
+    return found;
+  }
+
   /**
    * Which of `names` are carried by MORE THAN ONE symbol, at least one of which
    * something points at.
diff --git a/src/graph/dead-code.ts b/src/graph/dead-code.ts
index 1d724c5d7..5dce8f6db 100644
--- a/src/graph/dead-code.ts
+++ b/src/graph/dead-code.ts
@@ -797,6 +797,13 @@ function containersOf(cg: CodeGraph, nodes: readonly Node[]): Map<string, Node>
  * only choice that keeps the list's promise; the alternative puts every
  * implementation of every signature-only interface at the top of a screen that
  * says "nothing reaches this".
+ *
+ * An ancestor **outside the index** is opaque in the same way, and more so: a
+ * class that extends `React.Component` or `stream.Transform`, or implements a
+ * framework interface, has lifecycle methods the framework calls, and the
+ * ancestor leaves no edge to walk at all — only the resolver's failed
+ * `extends` / `implements` row. A container with such a row, or a project
+ * ancestor of one that has it, counts as having an opaque ancestor (#1973).
  */
 function overrideCandidates(
   cg: CodeGraph,
@@ -811,7 +818,7 @@ function overrideCandidates(
   // level rather than one per container. `reach` maps an ancestor back to the
   // containers it is an ancestor of.
   const reach = new Map<string, Set<string>>();
-  const seen = new Set<string>(containerIds);
+  const seen = new Map(containerIds.map((id) => [id, new Set([id])]));
   let frontier = containerIds.map((id) => ({ id, roots: new Set<string>([id]) }));
 
   for (let depth = 0; depth < MAX_OVERRIDE_ANCESTOR_DEPTH && frontier.length > 0; depth++) {
@@ -826,21 +833,32 @@ function overrideCandidates(
       const roots = rootsOf.get(edge.source);
       if (!roots) continue;
       const merged = next.get(edge.target) ?? new Set<string>();
-      for (const root of roots) merged.add(root);
-      next.set(edge.target, merged);
+      const visited = seen.get(edge.target) ?? new Set<string>();
       const known = reach.get(edge.target) ?? new Set<string>();
-      for (const root of roots) known.add(root);
-      reach.set(edge.target, known);
+      // An ancestor may already be a candidate root. Only skip pairs we have
+      // propagated, so later descendants still reach all of its ancestors.
+      for (const root of roots) {
+        if (visited.has(root)) continue;
+        visited.add(root);
+        merged.add(root);
+        known.add(root);
+      }
+      seen.set(edge.target, visited);
+      if (merged.size > 0) next.set(edge.target, merged);
+      if (known.size > 0) reach.set(edge.target, known);
     }
     frontier = [];
     for (const [id, roots] of next) {
-      if (seen.has(id)) continue;
-      seen.add(id);
       frontier.push({ id, roots });
     }
   }
 
-  if (reach.size === 0) return dropped;
+  const opaqueContainers = new Set<string>();
+  const externalBased = cg.getUnresolvedSupertypeSourcesAmong([...containerIds, ...reach.keys()]);
+  for (const id of containerIds) if (externalBased.has(id)) opaqueContainers.add(id);
+  for (const [ancestorId, roots] of reach) {
+    if (externalBased.has(ancestorId)) for (const root of roots) opaqueContainers.add(root);
+  }
 
   // What each ancestor declares, and whether it declares anything at all.
   const ancestorIds = [...reach.keys()];
@@ -855,7 +873,6 @@ function overrideCandidates(
 
   /** Member names an ancestor declares, and whether it declares none we can read. */
   const namesByContainer = new Map<string, Set<string>>();
-  const opaqueContainers = new Set<string>();
   for (const [ancestorId, roots] of reach) {
     const names: string[] = [];
     for (const memberId of memberIdsByAncestor.get(ancestorId) ?? []) {
diff --git a/src/index.ts b/src/index.ts
index b27035748..c1226fc7f 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -1479,6 +1479,14 @@ export class CodeGraph {
     return this.queries.getUnresolvedNamesAmong(names);
   }
 
+  /**
+   * Which of the given symbols extend or implement a type outside the index —
+   * an ancestor the resolver could not follow, so it has no edge (#1973).
+   */
+  getUnresolvedSupertypeSourcesAmong(nodeIds: Iterable<string>): Set<string> {
+    return this.queries.getUnresolvedSupertypeSourcesAmong(nodeIds);
+  }
+
   /**
    * The symbols with the most distinct dependents, most first — the index's
    * hubs. Distinct dependents, not edges: a helper called forty times from one