fix(agent-core-v2): preserve compaction hook session

packages/agent-core-v2/docs/di-scope-domains.puml

@@ -315,6 +315,7 @@ externalHooks --> config #34495E
 externalHooks --> bootstrap #34495E
 externalHooks --> plugin #34495E
 externalHooks --> contextMemory #34495E
+externalHooks --> session_context #34495E
 sessionExternalHooks --> session_lifecycle #34495E
 sessionExternalHooks --> agent_lifecycle #34495E
 sessionExternalHooks --> config #34495E

packages/agent-core-v2/src/agent/externalHooks/externalHooksService.ts

@@ -10,8 +10,9 @@
  * of its own). The requester-side `SubagentStart` / `SubagentStop` hooks are
  * translated by the Session-scope `SessionExternalHooksService`, which observes
  * the `agentLifecycle` run slots hosted on `IAgentLifecycleService`. Appends
- * UserPromptSubmit hook results
- * and Stop hook continuation prompts through `contextMemory`.
+ * UserPromptSubmit hook results and Stop hook continuation prompts through
+ * `contextMemory`, and passes the current session id from `sessionContext`
+ * into hook runner payloads.
  */
 
 import { IInstantiationService } from '#/_base/di/instantiation';
@@ -42,6 +43,7 @@ import type { ToolDidExecuteContext, ToolWillExecuteContext } from '#/agent/tool
 import { IAgentToolExecutorService } from '#/agent/toolExecutor/toolExecutor';
 import { IAgentTurnService } from '#/agent/turn/turn';
 import { toKimiErrorPayload } from '#/errors';
+import { ISessionContext } from '#/session/sessionContext/sessionContext';
 
 import { IAgentExternalHooksService } from './externalHooks';
 import { IExternalHooksRunnerService } from '#/app/externalHooksRunner/externalHooksRunner';
@@ -66,6 +68,7 @@ export class AgentExternalHooksService extends Disposable implements IAgentExter
     @IAgentContextMemoryService private readonly context: IAgentContextMemoryService,
     @IEventBus private readonly eventBus: IEventBus,
     @IInstantiationService private readonly instantiation: IInstantiationService,
+    @ISessionContext private readonly sessionContext: ISessionContext,
   ) {
     super();
     this.registerListeners();
@@ -82,7 +85,12 @@ export class AgentExternalHooksService extends Disposable implements IAgentExter
     // output), and throwing here would clobber that with a finalize-abort error.
     // The runner mirrors the legacy fire-and-forget behavior.
     try {
-      void this.runner.fireAndForgetTrigger(event, { matcherValue, signal, inputData });
+      void this.runner.fireAndForgetTrigger(event, {
+        matcherValue,
+        signal,
+        sessionId: this.sessionContext.sessionId,
+        inputData,
+      });
     } catch {}
   }
 
@@ -222,6 +230,7 @@ export class AgentExternalHooksService extends Disposable implements IAgentExter
     const block = await this.runner.triggerBlock('PreToolUse', {
       matcherValue: ctx.toolCall.name,
       signal: ctx.signal,
+      sessionId: this.sessionContext.sessionId,
       inputData: {
         toolName: ctx.toolCall.name,
         toolInput,
@@ -260,6 +269,7 @@ export class AgentExternalHooksService extends Disposable implements IAgentExter
     const results = await this.runner.trigger('UserPromptSubmit', {
       matcherValue: input,
       signal,
+      sessionId: this.sessionContext.sessionId,
       inputData: { prompt: input, isSteer: ctx.isSteer },
     });
     signal.throwIfAborted();
@@ -331,6 +341,7 @@ export class AgentExternalHooksService extends Disposable implements IAgentExter
 
     const block = await this.runner.triggerBlock('Stop', {
       signal: ctx.signal,
+      sessionId: this.sessionContext.sessionId,
       inputData: { stopHookActive: false },
     });
     ctx.signal.throwIfAborted();
@@ -343,6 +354,7 @@ export class AgentExternalHooksService extends Disposable implements IAgentExter
     await this.runner.trigger('PreCompact', {
       matcherValue: ctx.trigger,
       signal,
+      sessionId: this.sessionContext.sessionId,
       inputData: {
         trigger: ctx.trigger,
         tokenCount: ctx.tokenCount,

packages/agent-core-v2/test/fullCompaction/full.test.ts

@@ -1,4 +1,4 @@
-import { existsSync, mkdtempSync, readFileSync } from 'node:fs';
+import { existsSync, mkdtempSync, readFileSync, writeFileSync } from 'node:fs';
 import { tmpdir } from 'node:os';
 import { join } from 'pathe';
 
@@ -511,14 +511,14 @@ describe('FullCompaction', () => {
     const [pre, post] = readHookPayloads(hookLog);
     expect(pre).toMatchObject({
       hook_event_name: 'PreCompact',
-      session_id: 'session-hooks',
+      session_id: 'test-session',
       cwd: dir,
       trigger: 'auto',
       token_count: 39,
     });
     expect(post).toMatchObject({
       hook_event_name: 'PostCompact',
-      session_id: 'session-hooks',
+      session_id: 'test-session',
       cwd: dir,
       trigger: 'auto',
       estimated_token_count: ctx.contextData().tokenCount,
@@ -2545,6 +2545,10 @@ function messageText(message: Message | undefined): string {
 }
 
 function hookPayloadLoggerCommand(logPath: string): string {
+  // Write the hook script to a file and run it with node, instead of
+  // `node -e <json>`; cmd.exe on Windows mangles the escaped quotes in the
+  // inline form and corrupts the script before it can run.
+  const scriptPath = `${logPath}.cjs`;
   const script = [
     "const fs = require('node:fs');",
     "let input = '';",
@@ -2553,7 +2557,8 @@ function hookPayloadLoggerCommand(logPath: string): string {
     `  fs.appendFileSync(${JSON.stringify(logPath)}, JSON.stringify(JSON.parse(input)) + '\\n');`,
     '});',
   ].join('');
-  return `node -e ${JSON.stringify(script)}`;
+  writeFileSync(scriptPath, script);
+  return `${process.execPath} ${scriptPath}`;
 }
 
 function readHookPayloads(logPath: string): Array<Record<string, unknown>> {

packages/agent-core-v2/test/harness/agent.ts

@@ -576,7 +576,11 @@ function resolveExternalHooksRunner(
 function isRunnerLike(
   value: Pick<IExternalHooksRunnerService, 'trigger' | 'triggerBlock' | 'fireAndForgetTrigger'>,
 ): value is IExternalHooksRunnerService {
-  return '_serviceBrand' in value;
+  return (
+    typeof value.trigger === 'function' &&
+    typeof value.triggerBlock === 'function' &&
+    typeof value.fireAndForgetTrigger === 'function'
+  );
 }
 
 const noopHookRunner: IExternalHooksRunnerService = {