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/engine/core-modules/billing/services/billing-usage.service.ts

@@ -285,7 +285,7 @@ export class BillingUsageService {
     );
   }
 
-  private async warmAvailableCredits(
+  private async warmAvailableCreditsInCache(
     workspaceId: string,
     periodStart: Date | string,
     periodEnd: Date | string,
@@ -421,13 +421,13 @@ export class BillingUsageService {
     return Number(resourceCreditPrice.metadata?.credit_amount ?? 0);
   }
 
-  async decrementAvailableCredits({
+  async decrementAvailableCreditsInCache({
     workspaceId,
     usedCredits,
   }: {
     workspaceId: string;
     usedCredits: number;
-  }): Promise<void> {
+  }): Promise<number> {
     const {
       billingSubscription: { currentPeriodStart, currentPeriodEnd },
     } = await this.workspaceCacheService.getOrRecompute(workspaceId, [
@@ -447,7 +447,7 @@ export class BillingUsageService {
         });
 
     if (!isDefined(cachedAvailableCredits)) {
-      await this.warmAvailableCredits(
+      await this.warmAvailableCreditsInCache(
         workspaceId,
         currentPeriodStart,
         currentPeriodEnd,
@@ -470,9 +470,11 @@ export class BillingUsageService {
         true,
       );
     }
+
+    return decrementedAvailableCredits;
   }
 
-  async invalidateAvailableCredits(
+  async invalidateAvailableCreditsInCache(
     workspaceId: string,
     periodStart: Date,
   ): Promise<void> {
@@ -504,7 +506,7 @@ export class BillingUsageService {
       currentPeriodStart: subscription.currentPeriodStart,
     });
 
-    await this.warmAvailableCredits(
+    await this.warmAvailableCreditsInCache(
       subscription.workspaceId,
       subscription.currentPeriodStart,
       subscription.currentPeriodEnd,

packages/twenty-server/src/engine/core-modules/logic-function/logic-function-executor/logic-function-executor.service.ts

@@ -376,7 +376,7 @@ export class LogicFunctionExecutorService {
 
       periodStart = currentPeriodStart;
 
-      await this.billingUsageService.decrementAvailableCredits({
+      await this.billingUsageService.decrementAvailableCreditsInCache({
         workspaceId,
         usedCredits: 100,
       });