refactor(billing): drop the seat 410 stop-gap; PR 2 ships in the same release

The readable-copy branch only served the window where the seat-era plans
page was live without PR 2's replacement. PR 1 and PR 2 ship as one release,
so that window is zero: the typed 410 error, the classify branch, and their
tests go, leaving the PR with no seat-API changes at all (auto-provisioning
already fails soft on any create error).

Generated-By: PostHog Code
Task-Id: 1039ea23-9930-44e2-9888-b05cf8b129ec

Author: adboio

packages/api-client/src/posthog-client.ts

@@ -133,14 +133,6 @@ export class SeatPaymentFailedError extends Error {
   }
 }
 
-/** Seat creation/upgrades/reactivation return 410 Gone: seats are retired. */
-export class SeatProductRetiredError extends Error {
-  constructor() {
-    super("PostHog Code seats have been retired");
-    this.name = "SeatProductRetiredError";
-  }
-}
-
 export class SandboxCustomImagesDisabledError extends Error {
   constructor(message?: string) {
     super(message ?? "Custom sandbox images are not enabled");
@@ -4597,9 +4589,6 @@ export class PostHogAPIClient {
     const parsed = this.parseFetcherError(error);
 
     if (parsed) {
-      if (parsed.status === 410) {
-        throw new SeatProductRetiredError();
-      }
       if (
         parsed.status === 400 &&
         typeof parsed.body.redirect_url === "string"

packages/core/src/billing/seatErrors.ts

@@ -8,16 +8,6 @@ export function classifySeatError(error: unknown): ClassifiedSeatError {
     return { error: "An unexpected error occurred", redirectUrl: null };
   }
 
-  // Seats are retired (410 Gone); the seat-era UI that can hit this goes
-  // away at cutover, so readable copy is the only handling.
-  if (error.name === "SeatProductRetiredError") {
-    return {
-      error:
-        "PostHog Code seat plans have been retired — usage is now billed to your organization.",
-      redirectUrl: null,
-    };
-  }
-
   if (error.name === "SeatSubscriptionRequiredError") {
     const redirectUrl =
       "redirectUrl" in error && typeof error.redirectUrl === "string"

packages/core/src/billing/seatService.test.ts

@@ -62,13 +62,6 @@ class SeatPaymentFailedError extends Error {
   }
 }
 
-class SeatProductRetiredError extends Error {
-  constructor() {
-    super("PostHog Code seats have been retired");
-    this.name = "SeatProductRetiredError";
-  }
-}
-
 beforeEach(() => {
   vi.clearAllMocks();
 });
@@ -285,27 +278,3 @@ describe("error classification", () => {
     expect(result.error).toBe("Card declined");
   });
 });
-
-// The seat API 410s creation/upgrades/reactivation once Code seats are
-// retired in favor of usage-based billing (reads keep working).
-describe("seat product retired (410 Gone)", () => {
-  it("treats a retired auto-provision as seatless instead of erroring", async () => {
-    const client = makeClient({
-      createSeat: vi.fn().mockRejectedValue(new SeatProductRetiredError()),
-    });
-    const result = await new SeatService(client, logger).fetchSeat({
-      autoProvision: true,
-    });
-    expect(result.seat).toBeNull();
-    expect(result.error).toBeNull();
-  });
-
-  it("surfaces retirement as a clear error on an explicit upgrade", async () => {
-    const client = makeClient({
-      createSeat: vi.fn().mockRejectedValue(new SeatProductRetiredError()),
-    });
-    const result = await new SeatService(client, logger).upgradeToPro();
-    expect(result.error).toContain("retired");
-    expect(result.redirectUrl).toBeNull();
-  });
-});

packages/core/src/billing/usageLimitContent.ts

@@ -3,15 +3,13 @@ import type { GatewayLimitCause } from "@posthog/shared";
 export interface UsageLimitContent {
   title: string;
   description: string;
-  /** Primary action label; null renders only the dismiss button. */
   actionLabel: string | null;
   dismissLabel: string;
 }
 
 export function usageLimitContent(args: {
   cause: GatewayLimitCause | null;
   resetLabel: string | null;
-  /** usage.code_usage_billed — absent means unknown, not free. */
   billed: boolean | undefined;
 }): UsageLimitContent {
   const { cause, resetLabel, billed } = args;

packages/core/src/llm-gateway/llm-gateway.ts

@@ -26,7 +26,6 @@ import {
 // the cheapest model rather than the gateway default.
 export const HELPER_GATEWAY_MODEL = "claude-haiku-4-5";
 
-// Unbilled orgs can only use the free tier; helpers degrade to it silently.
 export const FREE_TIER_GATEWAY_MODEL = "@cf/zai-org/glm-5.2";
 
 export class LlmGatewayError extends Error {
@@ -58,8 +57,6 @@ export class LlmGatewayService {
   private readonly endpoints: LlmGatewayEndpoints;
   private readonly log: LlmGatewayLogger;
 
-  // Learned from this service's own usage fetches; null until the gateway
-  // has said either way.
   private lastKnownCodeUsageBilled: boolean | null = null;
 
   async prompt(
@@ -80,8 +77,6 @@ export class LlmGatewayService {
     } = {},
   ): Promise<PromptOutput> {
     const requested = options.model ?? this.endpoints.defaultModel;
-    // Helper-only traffic (the agent session rides the SDK, not this
-    // service): known-unbilled orgs go straight to the free-tier model.
     const model =
       this.lastKnownCodeUsageBilled === false
         ? FREE_TIER_GATEWAY_MODEL
@@ -94,8 +89,6 @@ export class LlmGatewayService {
         error.statusCode === 403 &&
         classifyGatewayLimitError(error.message) === "model_gate";
       if (!isModelGate || model === FREE_TIER_GATEWAY_MODEL) throw error;
-      // Cold start / stale bit: the gate is authoritative that the org is
-      // unbilled — remember it and degrade this call instead of failing.
       this.lastKnownCodeUsageBilled = false;
       this.log.warn("Model gated for free tier, retrying on free-tier model", {
         model,

packages/core/src/llm-gateway/schemas.ts

@@ -55,7 +55,6 @@ export interface AnthropicErrorResponse {
     type: string;
     code?: string;
   };
-  // Some gateway 403s carry a bare FastAPI `detail` instead of the envelope.
   detail?: unknown;
 }
 

packages/core/src/sessions/sessionService.ts

@@ -2715,8 +2715,6 @@ export class SessionService {
 
       const limitCause = classifyGatewayLimitError(errorMessage, errorDetails);
 
-      // Billing denials from the gateway leave the session healthy — surface
-      // the upgrade gate, not an error state.
       if (
         limitCause === "model_gate" ||
         isRateLimitError(errorMessage, errorDetails)

packages/core/src/usage/schemas.ts

@@ -11,12 +11,9 @@ export const usageOutput = z.object({
   user_id: z.number(),
   sustained: usageBucketSchema,
   burst: usageBucketSchema,
-  // Org credit bucket (named ai_credits on the wire): free allocation or
-  // billing limit exhausted.
   ai_credits: z.object({ exhausted: z.boolean() }).optional(),
   is_rate_limited: z.boolean(),
   is_pro: z.boolean(),
-  // Absent on older gateways — absence means unknown, never "free".
   code_usage_billed: z.boolean().optional(),
   billing_period_end: z.string().datetime().nullable().optional(),
 });

packages/shared/src/analytics-events.ts

@@ -983,7 +983,6 @@ export type UpgradePromptClickedSurface =
   | "plan_page_card"
   | "upgrade_dialog";
 
-/** Which gateway denial put the prompt on screen (usage-based billing). */
 export type UpgradePromptCause = "model_gate" | "org_limit";
 
 export interface UpgradePromptShownProperties {

packages/shared/src/errors.ts

@@ -74,23 +74,12 @@ const RATE_LIMIT_PATTERNS = [
   "[429]",
 ] as const;
 
-/**
- * Billing denials from the PostHog LLM gateway, matched on the prose in
- * `error.message` (agent-SDK surfaces often reduce the body to that string,
- * so the gateway's structured `code` can't be relied on here). Kept in sync
- * with services/llm-gateway in posthog/posthog:
- * - "model_gate" (403): org isn't billed for Code usage and requested a
- *   model outside the free tier.
- * - "org_limit" (429): the org's credit bucket is exhausted — free
- *   allocation used up, or the org's billing limit reached.
- */
 export type GatewayLimitCause = "model_gate" | "org_limit";
 
 const MODEL_GATE_PATTERNS = ["needs a paid posthog plan"] as const;
 
 const ORG_LIMIT_PATTERNS = [
   "reached its posthog code usage limit",
-  // Gateway fallback wording for a credit bucket without a mapped message.
   "reached its usage limit for this billing period",
 ] as const;
 
@@ -168,8 +157,6 @@ export function isFatalSessionError(
 ): boolean {
   if (isRateLimitError(errorMessage, errorDetails)) return false;
   if (isTransientUpstreamError(errorMessage, errorDetails)) return false;
-  // A model-gate 403 arrives wrapped as "Internal error: API Error: 403 …"
-  // but the session is healthy — it must never trigger teardown.
   if (classifyGatewayLimitError(errorMessage, errorDetails) === "model_gate") {
     return false;
   }