feat(ai-chat) - Stop ai thinking if credits exhausted (#20526)

Billing is now decremented per-step, not per-turn. The onStepFinish
callback in chat-execution.service.ts calls a new
decrementAndCheckAvailableCredits method on each model step, so Redis is
debited incrementally as the agent runs rather than all at once at the
end.

Credit exhaustion stops the stream mid-run. When a step depletes the
remaining credits, a hasNoMoreAvailableCredits flag is set and passed
into the stopWhen predicate of streamText, causing the agent to halt
before starting the next step.

A new credits-exhausted event is introduced. After the stream drains and
the response is persisted, if credits ran out the job publishes a
dedicated credits-exhausted event to the frontend instead of the normal
message-persisted event.

The frontend handles this new event. useAgentChatSubscription has a new
credits-exhausted case that sets a BILLING_CREDITS_EXHAUSTED-coded error
on the atom, closes the writer, and stops the streaming state —
triggering the existing AiChatCreditsExhaustedMessage UI.

packages/twenty-server/src/modules/workflow/workflow-executor/workflow-actions/ai-agent/ai-agent.workflow-action.ts

@@ -76,18 +76,25 @@ export class AiAgentWorkflowAction implements WorkflowAction {
         ? executionContext.authContext.userWorkspaceId
         : null;
 
-    const { result } = await this.aiAgentExecutionService.executeAgent({
-      agent,
-      userPrompt: resolveInput(prompt, context) as string,
-      actorContext: executionContext.isActingOnBehalfOfUser
-        ? executionContext.initiator
-        : undefined,
-      rolePermissionConfig: executionContext.rolePermissionConfig,
-      authContext: executionContext.authContext,
-      workspaceId,
-      userWorkspaceId,
-      operationType: UsageOperationType.AI_WORKFLOW_TOKEN,
-    });
+    const { result, hasNoMoreAvailableCredits } =
+      await this.aiAgentExecutionService.executeAgent({
+        agent,
+        userPrompt: resolveInput(prompt, context) as string,
+        actorContext: executionContext.isActingOnBehalfOfUser
+          ? executionContext.initiator
+          : undefined,
+        rolePermissionConfig: executionContext.rolePermissionConfig,
+        authContext: executionContext.authContext,
+        workspaceId,
+        userWorkspaceId,
+        operationType: UsageOperationType.AI_WORKFLOW_TOKEN,
+      });
+
+    if (hasNoMoreAvailableCredits) {
+      return {
+        error: 'AI agent stopped: no more available credits.',
+      };
+    }
 
     return {
       result,

packages/twenty-server/src/modules/workflow/workflow-executor/workspace-services/__tests__/workflow-executor.workspace-service.spec.ts

@@ -78,7 +78,7 @@ describe('WorkflowExecutorWorkspaceService', () => {
 
   const mockBillingUsageService = {
     hasAvailableCredits: jest.fn().mockResolvedValue(true),
-    decrementAvailableCredits: jest.fn().mockResolvedValue(undefined),
+    decrementAvailableCreditsInCache: jest.fn().mockResolvedValue(undefined),
   };
 
   const mockExceptionHandlerService = {

packages/twenty-server/src/modules/workflow/workflow-executor/workspace-services/workflow-executor.workspace-service.ts

@@ -375,7 +375,7 @@ export class WorkflowExecutorWorkspaceService {
 
       periodStart = currentPeriodStart;
 
-      await this.billingUsageService.decrementAvailableCredits({
+      await this.billingUsageService.decrementAvailableCreditsInCache({
         workspaceId,
         usedCredits: 100,
       });