---
title: "What changed in third-party APIs in September 2026 | Harbyn"
description: "706 changes from 87 of the 170 vendors Harbyn tracks: 83 breaking changes, 17 model retirements, the notice vendors gave, and 71 deadlines due by early January."
canonical: "https://harbyn.com/blog/api-changes-september-2026"
last-updated: 2026-10-11
---

# What changed in third-party APIs in September 2026

Published October 11, 2026 by Harbyn. Tags: data-report, breaking-changes, deprecations, ai-models.

Harbyn's public change feed recorded **706 changes** announced in September 2026, by **87 of the [170 vendors](https://harbyn.com/vendors)** it tracks. **278** of them are changes a developer may have to act on: **83 breaking changes**, **29 retirements** (17 of them AI model retirements), 79 behavior changes, 47 pricing changes and more. Looking ahead from October 11, **71 deadlines** fall in the next 90 days, 23 of them model retirements.

This is the first Harbyn change report. Every number below comes from the feed as it stood on October 11, 2026, and the [method](#method) section says exactly how each one was counted. These are counts for the vendors Harbyn tracks, not for every API in existence.

## The numbers at a glance

| Measure | Value |
|---|---|
| Changes announced in September, at the vendors Harbyn tracks | 706 |
| Of those, changes to act on (not launches or unclassified notes) | 278 |
| Breaking changes | 83 |
| AI model retirements announced | 17, at 12 vendors |
| Median notice before a retirement took effect | 14 days |
| Median notice before a dated breaking change took effect | 0 days |
| Deadlines between October 11, 2026 and January 9, 2027 | 71 |

## Why September and not the whole quarter

Harbyn's feed started publishing on September 21, 2026. Events from earlier in September were recorded from the vendors' own changelogs and deprecation pages, but the feed holds only 24 changes announced in July and August, too few to describe those months. So this report covers changes announced from September 1 to September 30. The first full quarterly report will cover Q4 2026.

## Changes by kind

| Kind | Changes |
|---|---|
| Feature or launch | 353 |
| Breaking change | 83 |
| Behavior change | 79 |
| Unclassified notice | 75 |
| Pricing | 47 |
| Retirement | 29 |
| Deprecation | 17 |
| Rate limit | 9 |
| Policy | 8 |
| Security | 6 |
| **Total** | **706** |

Half of the entries are new things: model launches, new endpoints, new options. Those go to the [Radar](https://harbyn.com/radar) and are left out of everything below. Unclassified notices are changelog entries we have recorded but not yet classified. The remaining **278 changes** are the ones that can break code, change behavior or change a bill.

## Where the changes came from

The 278 changes to act on, by the kind of vendor that announced them:

| Vendor category | Changes |
|---|---|
| AI models and APIs | 111 |
| Payments | 44 |
| Cloud | 34 |
| Developer tools | 29 |
| Commerce | 25 |
| Developer platform | 19 |
| Messaging | 11 |
| Fiscal (Brazil) | 4 |
| ERP | 1 |

AI vendors are 39 of the 170 Harbyn tracks (23%), but they announced 40% of these changes.

## Who shipped the most breaking changes

| Vendor | Breaking changes |
|---|---|
| [Stripe](https://harbyn.com/vendors/stripe) | 29 |
| [Linear API](https://harbyn.com/vendors/linear) | 6 |
| [Shopify](https://harbyn.com/vendors/shopify) | 6 |
| [Neon](https://harbyn.com/vendors/neon) | 5 |
| [Modal](https://harbyn.com/vendors/modal) | 4 |
| [WooCommerce](https://harbyn.com/vendors/woocommerce) | 4 |

The counts depend on how each vendor documents its changes, so they say more about release style than about stability:

- **Stripe**: all 29 belong to one release, the [2026-09-30.endive](https://docs.stripe.com/changelog) API version and the matching Stripe.js version, which Stripe documents one change per entry. Examples: the [payment method types parameter removed from Checkout Sessions](https://harbyn.com/changes/stripe/2026-09-30-endive-removes-the-payment-method-types-parameter-from-checkout-sessions), and the [same parameter removed from Payment Intents and Setup Intents](https://harbyn.com/changes/stripe/2026-09-30-endive-removes-the-payment-method-types-parameter-from-payment-intents-and-setup). Stripe ships breaking changes as new API versions; they reach an integration when it upgrades the version it pins.
- **Linear API**: five new major versions of `@linear/sdk` (93.0.0 to 97.0.0) and one of `@linear/import`. The last one, 97.0.0, [is ESM-only](https://harbyn.com/changes/linear/2026-09-28-linear-97-0-0).
- **Neon**: five releases of `@neon/sdk` with breaking changes, such as [7.0.0 removing snapshot slugs](https://harbyn.com/changes/neon/2026-09-29-neon-sdk-7-0-0).
- **Shopify**: changes across its APIs, app extensions and developer tooling, for example [removing the marketCurrencySettingsUpdate mutation](https://harbyn.com/changes/shopify/2026-09-22-removing-marketcurrencysettingsupdate-mutation).

## AI model retirements announced in September

Seventeen retirements at twelve vendors. The date is when requests to the model stop working (or, where noted, are redirected).

| Vendor | Models | Effective |
|---|---|---|
| [Anthropic](https://harbyn.com/changes/anthropic/2026-09-30-claude-sonnet-4-5-model-retirement) | `claude-sonnet-4-5-20250929` | Nov 30, 2026 |
| [OpenAI](https://harbyn.com/changes/openai/2026-09-11-gpt-5-4-cyber-shutdown) | `gpt-5.4-cyber` | Oct 1, 2026 |
| [Google Gemini API](https://harbyn.com/changes/google-gemini/2026-09-30-veo-3-1-lite-generate-preview-shutdown-2026-10-22) | three `veo-3.1` preview models | Oct 22, 2026 (earliest date, per Google) |
| [Mistral AI](https://harbyn.com/changes/mistral/2026-09-29-ocr-4-0-deprecated-and-scheduled-for-retirement) | `mistral-ocr-4-0` | Sep 30, 2026 |
| [Mistral AI](https://harbyn.com/changes/mistral/2026-09-29-z-ai-glm-5-2-deprecated-and-scheduled-for-retirement) | `zai-glm-5-2` | Oct 31, 2026 |
| [xAI API](https://harbyn.com/changes/xai/2026-09-02-grok-imagine-image-quality-retirement) | `grok-imagine-image-quality`, then served by `grok-imagine-image-2.0` | Nov 2, 2026 |
| [Perplexity API](https://harbyn.com/changes/perplexity/2026-09-25-older-openai-models-retired-october-24-2026) | seven older OpenAI models on the Agent and Router APIs | Oct 24, 2026 |
| [DeepSeek API](https://harbyn.com/changes/deepseek/2026-09-10-previous-generation-v4-flash-models-retired) | V4 Flash and V4 Flash Vision Exp, names routed to V4.1 Flash for now | Sep 10, 2026 |
| [Groq](https://harbyn.com/changes/groq/2026-09-14-qwen-qwen3-6-27b-shutdown) | `qwen/qwen3.6-27b` | Sep 14, 2026 |
| [Together AI](https://harbyn.com/changes/together/2026-09-01-four-serverless-models-removed-september-14-2026) | four serverless models | Sep 14, 2026 |
| [Fireworks AI](https://harbyn.com/changes/fireworks/2026-09-12-upcoming-serverless-deprecation-older-deepseek-glm-muse-and-kimi-models) | older DeepSeek, GLM, Muse and Kimi models on Serverless | Sep 25, 2026 |
| [Cerebras](https://harbyn.com/changes/cerebras/2026-09-03-gemma-4-31b-availability-changes-on-public-endpoints) | `gemma-4-31b` on public endpoints | in effect when announced |
| [OpenRouter](https://harbyn.com/vendors/openrouter) | five expiry notices from its models API | Sep 25 to Dec 31, 2026 |

Across all 25 dated retirements announced in September, of models and of anything else, the median notice was 14 days.

## How much notice vendors gave

For every dated change to act on, we measured the days from the vendor's announcement to the day the change takes effect.

| Kind | Dated changes | Median notice |
|---|---|---|
| Retirement | 25 | 14 days |
| Deprecation | 5 | 168 days |
| Behavior change | 10 | 15.5 days |
| Breaking change | 32 | 0 days |
| All dated changes to act on | 76 | 1 day |

A dated breaking change usually took effect the day it was announced. Many are new SDK major versions or API versions you opt into, so "0 days" often means "when you upgrade", not "today". Retirements are different: when the date arrives, the old model or version stops working or changes behavior whether you upgrade or not, and the median warning was two weeks. The deprecation figure rests on five changes, too few to generalize from.

## Deadlines in the next 90 days

Between October 11, 2026 and January 9, 2027, the feed holds **71 deadlines**: 46 retirements, 9 deprecations, 8 behavior changes, 4 breaking changes, 2 policy changes, 1 rate-limit change and 1 security change. The vendors with the most are Azure OpenAI (13), OpenRouter (8), SEFAZ e-invoicing in Brazil (6) and the Google Gemini API (5). A few with wide reach:

- **Oct 16**: [Shopify API version 2025-10 leaves support](https://harbyn.com/changes/shopify/2026-09-21-api-version-2025-10-unsupported-2026-10-16). Calls that pin it are then served by the oldest supported version, so responses can change with no code change on your side.
- **Oct 20**: [Vertex AI retires gemini-2.5-pro, gemini-2.5-flash and gemini-2.5-flash-lite](https://harbyn.com/changes/vertex-ai/2026-10-09-gemini-2-5-models-scheduled-for-retirement).
- **Oct 23**: [OpenAI removes legacy GPT snapshots](https://harbyn.com/changes/openai/2026-04-22-legacy-gpt-model-snapshots-shutdown), including `gpt-3.5-turbo`, `gpt-4` and `gpt-4-turbo`.
- **Nov 2**: [GitHub Actions retires the macOS 14 runner image](https://harbyn.com/changes/github/2026-10-01-github-actions-macos-14-runner-image-retirement).
- **Nov 30**: [Anthropic retires Claude Sonnet 4.5](https://harbyn.com/changes/anthropic/2026-09-30-claude-sonnet-4-5-model-retirement).
- **Dec 1**: [OpenAI removes three GPT Image models](https://harbyn.com/changes/openai/2026-06-02-gpt-image-model-deprecations-shutdown).
- **Dec 11**: [OpenAI removes the GPT-5 and o3 snapshots](https://harbyn.com/changes/openai/2026-06-11-gpt-5-and-o3-model-deprecations-shutdown).

The current list is on the [deadlines page](https://harbyn.com/deadlines) and in the [calendar feed](https://harbyn.com/calendar.ics).

## Method

- **Source.** Harbyn's change feed, the same data published as signed JSON at [feed.harbyn.com/v1/feed.json](https://feed.harbyn.com/v1/feed.json), as it stood on October 11, 2026. Events added after that day are left out, so the numbers do not drift as the feed grows. Only a feed that passes validation is counted, and retracted events are excluded.
- **Coverage.** 170 vendors (146 global, 24 Brazilian), listed on the [vendors page](https://harbyn.com/vendors). A vendor Harbyn does not track is not counted.
- **Window.** Changes whose vendor announcement date falls between September 1 and September 30, 2026. 66 more entries carry a September date only because they were already on a vendor page the first time we read it, with no date of their own; they could be much older, so they are left out.
- **Changes to act on.** Every kind except features and launches (353) and unclassified notices (75).
- **Notice.** Days from the vendor's announcement to the effective date, for changes to act on that have an effective date (a day, or the first day of a month when the vendor gave only a month), cancelled ones excluded. It uses the same day count as the feed's own lead-time rule.
- **Deadlines ahead.** Dated changes, launches excluded, whose date falls from October 11, 2026 to January 9, 2027, whenever they were announced, cancelled ones excluded.
- **What one count means.** One event is one change as the vendor documents it. A vendor that lists each change of a release separately shows up with more events than one that summarizes them, as Stripe does above.

Harbyn's own record in September, by the same rules: of the 76 dated changes to act on, the feed published 32 before they took effect, a median of 27 days ahead. The other 44 were recorded after they took effect; they are kept as history and never counted as warnings.

## Find these changes in your own code

The counts above are across vendors. What matters for a codebase is which of them touch it.

- `npx harbyn scan` runs the open-source scanner in your repository. It finds the model IDs, API versions, endpoints and SDK versions your code uses, matches them against the feed, and prints the file and line, the deadline and the replacement the vendor names. Nothing about your code leaves your machine. See the [docs](https://harbyn.com/docs).
- The [deadlines page](https://harbyn.com/deadlines), the [calendar feed](https://harbyn.com/calendar.ics) and the signed feed itself are public, with no account.
- Coding agents can ask the same questions through Harbyn's read-only MCP server at `https://api.harbyn.com/mcp`, for example "which OpenAI models are being retired and when". Setup is in the [docs](https://harbyn.com/docs).