diff --git a/apps/cli/src/lib/history-session-catalog-client.ts b/apps/cli/src/lib/history-session-catalog-client.ts
index 2ae409bbe..476f6a466 100644
--- a/apps/cli/src/lib/history-session-catalog-client.ts
+++ b/apps/cli/src/lib/history-session-catalog-client.ts
@@ -24,6 +24,8 @@ import {
   type ACPSessionId,
   getLocalProjectHistoryProviderKey,
   type LocalProjectHistoryProvider,
+  type CustomAcpLaunchSpec,
+  type BuiltinRuntimeOverrides,
 } from '@lody/shared';
 import { LODY_EXTENSION_METHODS } from 'acp-extension-core';
 
@@ -126,19 +128,33 @@ type ResolvedHistoryACPProcessLaunch = Omit<ResolvedACPProcessLaunch, 'env'> & {
   env: NodeJS.ProcessEnv;
 };
 
+export type HistoryLaunchProvider = LocalProjectHistoryProvider & {
+  customAcp?: CustomAcpLaunchSpec;
+  runtimeOverrides?: BuiltinRuntimeOverrides;
+  env?: NodeJS.ProcessEnv;
+};
+
 export async function resolveHistoryACPProcessLaunch(args: {
-  provider: LocalProjectHistoryProvider;
+  provider: HistoryLaunchProvider;
   env?: NodeJS.ProcessEnv;
 }): Promise<ResolvedHistoryACPProcessLaunch> {
-  const launch = await resolveACPProcessLaunchAsync(args.provider);
+  const launch = await resolveACPProcessLaunchAsync({
+    cliType: args.provider.cliType,
+    agentType: args.provider.agentType,
+    customAcp: args.provider.customAcp,
+    runtimeOverrides: args.provider.runtimeOverrides,
+  });
   return {
     ...launch,
-    env: mergeACPProcessEnv(launch, args.env ?? process.env),
+    env: mergeACPProcessEnv(launch, {
+      ...(args.env ?? process.env),
+      ...(args.provider.env ?? {}),
+    }),
   };
 }
 
 async function createHistoryAcpConnection(args: {
-  provider: LocalProjectHistoryProvider;
+  provider: HistoryLaunchProvider;
   workdir: string;
   logger: Logger;
 }): Promise<HistoryAcpConnection> {
@@ -327,7 +343,7 @@ export function dedupeHistorySessionsById(sessions: SessionInfo[]): SessionInfo[
 }
 
 export async function listHistorySessionsForLocalProject(args: {
-  provider: LocalProjectHistoryProvider;
+  provider: HistoryLaunchProvider;
   rootPath: string;
   logger: Logger;
   requiredSessionIds?: readonly string[];
@@ -376,7 +392,7 @@ export async function listHistorySessionsForLocalProject(args: {
 }
 
 export async function loadHistorySessionReplay(args: {
-  provider: LocalProjectHistoryProvider;
+  provider: HistoryLaunchProvider;
   rootPath: string;
   acpSessionId: ACPSessionId;
   logger: Logger;
diff --git a/apps/cli/src/lib/local-project-history-sync-service.ts b/apps/cli/src/lib/local-project-history-sync-service.ts
index cb75527fc..3e6b573fd 100644
--- a/apps/cli/src/lib/local-project-history-sync-service.ts
+++ b/apps/cli/src/lib/local-project-history-sync-service.ts
@@ -35,8 +35,10 @@ import {
 
 import type { LoroDocumentManager, SessionDocument } from '@/lib/loro/doc';
 import { readMachineLocalProjects, upsertMachineLocalProject } from '@/lib/local-project-meta';
+import { listMergedAgentConfigs } from '@/lib/agent-config-machine-flock';
 import {
   listHistorySessionsForLocalProject,
+  type HistoryLaunchProvider,
   loadHistorySessionReplay,
   MAX_LOCAL_PROJECT_HISTORY_CATALOG_SESSIONS,
 } from './history-session-catalog-client';
@@ -546,6 +548,7 @@ function buildExternalHistoryMeta(args: {
 export class LocalProjectHistorySyncService {
   private readonly provider: LocalProjectHistoryProvider;
   private readonly providerKey: string;
+  private launchProvider: HistoryLaunchProvider;
 
   constructor(
     private readonly manager: LoroDocumentManager,
@@ -559,6 +562,29 @@ export class LocalProjectHistorySyncService {
   ) {
     this.provider = provider;
     this.providerKey = getLocalProjectHistoryProviderKey(provider);
+    this.launchProvider = provider;
+  }
+
+  private async resolveLaunchProvider(): Promise<HistoryLaunchProvider> {
+    if (this.provider.cliType !== 'custom') {
+      return this.provider;
+    }
+    const configs = await listMergedAgentConfigs(this.manager.repo, this.context.workspaceId, [
+      this.context.machineId,
+    ]);
+    const config = configs.find(
+      (candidate) =>
+        candidate.machineId === this.context.machineId &&
+        candidate.cliType === this.provider.cliType &&
+        candidate.agentType === this.provider.agentType
+    );
+    const resolved = {
+      ...this.provider,
+      customAcp: config?.customAcp,
+      env: config?.env,
+    };
+    this.launchProvider = resolved;
+    return resolved;
   }
 
   async syncLocalProject(args: {
@@ -585,7 +611,8 @@ export class LocalProjectHistorySyncService {
     localProjectId: LocalProjectId;
     rootPath: string;
   }): Promise<LocalProjectHistoryCatalogResult> {
-    const snapshot = await this.listCatalogSnapshot(args);
+    this.launchProvider = await this.resolveLaunchProvider();
+    const snapshot = await this.listCatalogSnapshot(args, this.launchProvider);
     return await this.writeCatalogResult({
       localProjectId: args.localProjectId,
       sessions: snapshot.sessions,
@@ -644,6 +671,7 @@ export class LocalProjectHistorySyncService {
     const summary = emptySummary();
     const selectedIds = [...new Set(args.acpSessionIds)];
     summary.listed = selectedIds.length;
+    this.launchProvider = await this.resolveLaunchProvider();
     const snapshot = await this.listCatalogSnapshot({
       ...args,
       requiredSessionIds: selectedIds,
@@ -672,7 +700,7 @@ export class LocalProjectHistorySyncService {
           snapshot.existingByImportKey.get(importKey);
         if (!existing) {
           const replayNotifications = await loadHistorySessionReplay({
-            provider: this.provider,
+            provider: this.launchProvider,
             rootPath: args.rootPath,
             acpSessionId,
             logger: this.logger,
@@ -730,6 +758,7 @@ export class LocalProjectHistorySyncService {
     sessionId: SessionId;
     acpSessionId: string;
   }): Promise<LocalProjectHistoryConflictResolveResult> {
+    this.launchProvider = await this.resolveLaunchProvider();
     const snapshot = await this.listCatalogSnapshot({
       ...args,
       requiredSessionIds: [args.acpSessionId],
@@ -812,7 +841,7 @@ export class LocalProjectHistorySyncService {
 
     const acpSessionId = args.acpSessionId as unknown as ACPSessionId;
     const replayNotifications = await loadHistorySessionReplay({
-      provider: this.provider,
+      provider: this.launchProvider,
       rootPath: args.rootPath,
       acpSessionId,
       logger: this.logger,
@@ -906,13 +935,16 @@ export class LocalProjectHistorySyncService {
     });
   }
 
-  private async listCatalogSnapshot(args: {
-    localProjectId: LocalProjectId;
-    rootPath: string;
-    requiredSessionIds?: readonly string[];
-  }): Promise<HistoryCatalogSnapshot> {
+  private async listCatalogSnapshot(
+    args: {
+      localProjectId: LocalProjectId;
+      rootPath: string;
+      requiredSessionIds?: readonly string[];
+    },
+    provider: HistoryLaunchProvider = this.launchProvider
+  ): Promise<HistoryCatalogSnapshot> {
     const catalog = await listHistorySessionsForLocalProject({
-      provider: this.provider,
+      provider,
       rootPath: args.rootPath,
       logger: this.logger,
       requiredSessionIds: args.requiredSessionIds,
@@ -1124,7 +1156,7 @@ export class LocalProjectHistorySyncService {
     }
 
     const replayNotifications = await loadHistorySessionReplay({
-      provider: this.provider,
+      provider: this.launchProvider,
       rootPath: args.rootPath,
       acpSessionId: args.acpSessionId,
       logger: this.logger,
diff --git a/apps/cli/tests/history-session-catalog-client.test.ts b/apps/cli/tests/history-session-catalog-client.test.ts
index a03c29990..f7d4c4d14 100644
--- a/apps/cli/tests/history-session-catalog-client.test.ts
+++ b/apps/cli/tests/history-session-catalog-client.test.ts
@@ -217,6 +217,47 @@ describe('resolveHistoryACPProcessLaunch', () => {
     expect(historyLaunch.env.PATH).toBe('/usr/bin');
   });
 
+  it('resolves a custom ACP launch from the provider launch spec', async () => {
+    const historyLaunch = await resolveHistoryACPProcessLaunch({
+      provider: {
+        cliType: 'custom',
+        agentType: 'my-agent',
+        customAcp: {
+          command: process.execPath,
+          args: ['custom-acp-server.mjs', '--stdio'],
+        },
+      },
+      env: { PATH: '/usr/bin' },
+    });
+
+    expect(historyLaunch.command).toBe(process.execPath);
+    expect(historyLaunch.args).toEqual(['custom-acp-server.mjs', '--stdio']);
+    expect(historyLaunch.env.PATH).toBe('/usr/bin');
+  });
+
+  it('merges the authoritative custom ACP environment before spawning history', async () => {
+    const historyLaunch = await resolveHistoryACPProcessLaunch({
+      provider: {
+        cliType: 'custom',
+        agentType: 'my-agent',
+        customAcp: { command: process.execPath },
+        env: {
+          ACP_API_KEY: 'config-secret',
+          ACP_BASE_URL: 'https://config.example.test',
+          PATH: '/config/bin',
+        },
+      },
+      env: {
+        ACP_API_KEY: 'caller-secret',
+        PATH: '/caller/bin',
+      },
+    });
+
+    expect(historyLaunch.env.ACP_API_KEY).toBe('config-secret');
+    expect(historyLaunch.env.ACP_BASE_URL).toBe('https://config.example.test');
+    expect(historyLaunch.env.PATH).toBe('/config/bin');
+  });
+
   it('uses the same registry Interactive Claude npx launch as normal sessions', async () => {
     const provider = { cliType: 'registry', agentType: 'claude-p' } as const;
     const sessionLaunch = resolveACPProcessLaunch(provider);
diff --git a/packages/shared/src/node/local-project-control.ts b/packages/shared/src/node/local-project-control.ts
index f103379ef..9eeda6deb 100644
--- a/packages/shared/src/node/local-project-control.ts
+++ b/packages/shared/src/node/local-project-control.ts
@@ -39,7 +39,7 @@ function isStringArray(value: unknown): value is string[] {
 function isLocalProjectHistoryProvider(value: unknown): boolean {
   return (
     isObjectRecord(value) &&
-    (value.cliType === 'builtin' || value.cliType === 'registry') &&
+    (value.cliType === 'builtin' || value.cliType === 'registry' || value.cliType === 'custom') &&
     typeof value.agentType === 'string' &&
     value.agentType.trim().length > 0
   );
diff --git a/packages/shared/tests/local-project-control.test.ts b/packages/shared/tests/local-project-control.test.ts
index c58614b5d..4cf6c44a0 100644
--- a/packages/shared/tests/local-project-control.test.ts
+++ b/packages/shared/tests/local-project-control.test.ts
@@ -10,6 +10,10 @@ import {
 
 const codexProvider = { cliType: 'builtin', agentType: 'codex' } as const;
 const claudeProvider = { cliType: 'builtin', agentType: 'claude' } as const;
+const customProvider = {
+  cliType: 'custom',
+  agentType: 'custom-agent',
+} as const;
 
 describe('local project control request schema', () => {
   it('parses add request', () => {
@@ -198,6 +202,28 @@ describe('local project control request schema', () => {
     });
   });
 
+  it('parses custom provider history sync requests', () => {
+    const parsed = safeParseLocalProjectControlRequest(
+      JSON.stringify({
+        type: 'local-project/sync-history',
+        machineId: 'machine-1',
+        workspaceId: 'workspace-1',
+        localProjectId: 'project-1',
+        provider: customProvider,
+      })
+    );
+
+    expect(parsed.success).toBe(true);
+    if (!parsed.success) {
+      return;
+    }
+    if (parsed.data.type !== 'local-project/sync-history') {
+      throw new Error(`Unexpected request type: ${parsed.data.type}`);
+    }
+
+    expect(parsed.data.provider).toEqual(customProvider);
+  });
+
   it('parses Codex provider history import request with selected sessions', () => {
     const parsed = safeParseLocalProjectControlRequest(
       JSON.stringify({