diff --git a/packages/plugin-api/src/index.ts b/packages/plugin-api/src/index.ts
index ff9556e8a..f8570131c 100644
--- a/packages/plugin-api/src/index.ts
+++ b/packages/plugin-api/src/index.ts
@@ -252,4 +252,11 @@ export interface IndexerPlugin {
   resolveFile?(release: PluginReleaseCandidate, config: PluginIndexerConfig, host: PluginHost, signal: AbortSignal): Promise<PluginReleaseFile>;
   /** Sources whose session expires on its own clock, called on a schedule while enabled. */
   keepalive?(config: PluginIndexerConfig, host: PluginHost): Promise<void>;
+  /**
+   * Drop anything held in memory for this indexer, such as a live session. Called when an operator
+   * changes its base URL, credential or private-address setting, so the next call starts from the
+   * stored config. Not awaited, and a failure is logged rather than reported. Never called by hosts
+   * older than the hook.
+   */
+  forget?(indexerId: number): void | Promise<void>;
 }
diff --git a/server/src/modules/book-request/indexers/indexer-config.service.test.ts b/server/src/modules/book-request/indexers/indexer-config.service.test.ts
index 28f3efcfc..000fb26cb 100644
--- a/server/src/modules/book-request/indexers/indexer-config.service.test.ts
+++ b/server/src/modules/book-request/indexers/indexer-config.service.test.ts
@@ -3,6 +3,7 @@ import { DEFAULT_INDEXER_CATEGORIES, INDEXER_COLORS } from '@bookorbit/types';
 
 import type { RequestIndexerManagerRow, RequestIndexerRow } from '../../../db/schema';
 import { IndexerConfigService } from './indexer-config.service';
+import { PluginIndexerAdapter } from './plugins/plugin-host';
 
 function indexerRow(overrides: Partial<RequestIndexerRow> = {}): RequestIndexerRow {
   return {
@@ -493,6 +494,41 @@ describe('IndexerConfigService', () => {
     expect(adapter.forget).not.toHaveBeenCalled();
   });
 
+  /** A plugin's in-memory session otherwise outranks the stored credential until the process restarts. */
+  it('drops a plugin-backed session when its connection details change', async () => {
+    const forget = vi.fn();
+    const adapter = new PluginIndexerAdapter(
+      {
+        apiVersion: 1,
+        type: 'demo-tracker',
+        label: 'Demo Tracker',
+        requiresCredential: true,
+        credentialKind: 'sessionId',
+        mediaKinds: ['ebook'],
+        usesCategories: false,
+        seedsBack: true,
+        search: () => Promise.resolve([]),
+        test: () => Promise.resolve({ success: true }),
+        fetchTorrentFile: () => Promise.resolve(new Uint8Array()),
+        forget,
+      },
+      {} as never,
+    );
+    const { service } = makeService({
+      repo: { findById: vi.fn().mockResolvedValue(indexerRow({ adapterType: 'demo-tracker' })) },
+      registry: { require: vi.fn().mockReturnValue(adapter), find: vi.fn().mockReturnValue(adapter) },
+    });
+
+    await service.update(9, { credential: 'a-new-session' });
+    await service.update(9, { baseUrl: 'http://203.0.113.11:9117' });
+    await service.update(9, { allowPrivateAddress: true });
+    expect(forget.mock.calls).toEqual([[9], [9], [9]]);
+
+    forget.mockClear();
+    await service.update(9, { name: 'renamed', enabled: false });
+    expect(forget).not.toHaveBeenCalled();
+  });
+
   it('falls back to the adapter default categories for a medium left blank', async () => {
     const { service, repo } = makeService();
 
diff --git a/server/src/modules/book-request/indexers/plugins/plugin-host.test.ts b/server/src/modules/book-request/indexers/plugins/plugin-host.test.ts
index 83dd316a9..d6c4e0df2 100644
--- a/server/src/modules/book-request/indexers/plugins/plugin-host.test.ts
+++ b/server/src/modules/book-request/indexers/plugins/plugin-host.test.ts
@@ -18,6 +18,7 @@ vi.mock('dns/promises', async (importOriginal) => ({
 }));
 
 import { lookup } from 'dns/promises';
+import { Logger } from '@nestjs/common';
 
 import type { IndexerCredentialStore } from '../indexer-credential-store';
 import { IndexerSearchException, type ReleaseQuery, type ResolvedIndexerConfig } from '../indexer-adapter';
@@ -616,4 +617,42 @@ describe('PluginIndexerAdapter', () => {
     expect(credentials.rotate).toHaveBeenNthCalledWith(1, 4, 'session-2', 'session-1');
     expect(credentials.rotate).toHaveBeenNthCalledWith(2, 4, 'session-3', 'session-2');
   });
+
+  describe('forget', () => {
+    /** A plugin holding a live session would otherwise keep using it until the process restarts. */
+    it('tells the plugin to drop what it holds for the indexer', () => {
+      const forget = vi.fn();
+      const { adapter } = makeAdapter({ forget });
+
+      adapter.forget(12);
+
+      expect(forget).toHaveBeenCalledWith(12);
+    });
+
+    it('does nothing for a plugin written before the hook', () => {
+      expect(() => makeAdapter().adapter.forget(12)).not.toThrow();
+      expect(() => makeAdapter({ forget: true as never }).adapter.forget(12)).not.toThrow();
+    });
+
+    /** The operator's change is already saved by then, so a broken plugin cannot be allowed to fail it. */
+    it('logs a plugin that throws or rejects instead of failing the save', async () => {
+      const warn = vi.spyOn(Logger.prototype, 'warn').mockImplementation(() => undefined);
+      try {
+        expect(() =>
+          makeAdapter({
+            forget: () => {
+              throw new Error('no session map');
+            },
+          }).adapter.forget(12),
+        ).not.toThrow();
+        makeAdapter({ forget: () => Promise.reject(new Error('cache closed')) }).adapter.forget(13);
+        await new Promise((resolve) => setImmediate(resolve));
+
+        expect(warn).toHaveBeenCalledWith(expect.stringMatching(/indexerId=12 .*no session map/));
+        expect(warn).toHaveBeenCalledWith(expect.stringMatching(/indexerId=13 .*cache closed/));
+      } finally {
+        warn.mockRestore();
+      }
+    });
+  });
 });
diff --git a/server/src/modules/book-request/indexers/plugins/plugin-host.ts b/server/src/modules/book-request/indexers/plugins/plugin-host.ts
index eee20bf85..e14ab256c 100644
--- a/server/src/modules/book-request/indexers/plugins/plugin-host.ts
+++ b/server/src/modules/book-request/indexers/plugins/plugin-host.ts
@@ -152,6 +152,26 @@ export class PluginIndexerAdapter implements IndexerAdapter {
     };
   }
 
+  /**
+   * Runs after the operator's change has already been saved, so nothing a plugin does here may fail
+   * that save: a throw or a rejection is logged and dropped.
+   */
+  forget(indexerId: number): void {
+    if (typeof this.plugin.forget !== 'function') return;
+    try {
+      void Promise.resolve(this.plugin.forget(indexerId)).catch((error: unknown) => this.warnForgetFailed(indexerId, error));
+    } catch (error) {
+      this.warnForgetFailed(indexerId, error);
+    }
+  }
+
+  private warnForgetFailed(indexerId: number, error: unknown): void {
+    const message = error instanceof Error ? error.message : String(error);
+    this.logger.warn(
+      `[request_indexer.plugin] [fail] indexerId=${indexerId} type=${this.type} error="${sanitizeLogValue(message)}" - the plugin threw while forgetting its session`,
+    );
+  }
+
   /**
    * `deadline` is the caller's, where the caller has one. It is applied here rather than handed to
    * the plugin because a plugin can only check a signal between requests, and the request that