Five labs shipped frontier LLMs in a fortnight. Our Mac app’s picker added zero new rows.

Anthropic made Claude Opus 4.7 generally available on April 22, 2026 at the same $5 input / $25 output per million tokens as Opus 4.6, with Claude Sonnet 4.6 already the everyday default. OpenAI introduced GPT-5.5 and GPT-5.5 Pro in the API. DeepSeek released its V4 family (V4-Pro and V4-Flash, mixture-of-experts) as open source. Google pushed Gemini 2.5 Pro forward. Meta announced Spark Muse alongside movement around Llama 4. A third Anthropic model, codename Capybara (Claude Mythos), remains gated behind Project Glasswing. In aggregate this is the densest release fortnight since the original GPT-4 launch, and the real cost of "good enough" inference fell roughly 50 percent from January levels.

Most apps react to a new model by adding a row to a Swift enum and shipping a build. Fazm does not own a model catalog. The UI reads a @Published array called availableModels, and that array is filled at runtime by a bundled subprocess that talks to the Claude agent SDK. The picker renders ForEach(shortcutSettings.availableModels) at SettingsPage.swift line 2025, which means adding a new model is a server-side event for us, not a release event. For the user the visible change is: the label behind the Smart button now routes to Opus 4.7 instead of Opus 4.6. Same button. Same keyboard shortcut. No app to update.

Because the labels are not model names. They are usage profiles. Scary = Haiku-class (fastest, cheapest), Fast = Sonnet-class (everyday default), Smart = Opus-class (heaviest reasoning). The Swift map that does the translation has exactly four rows, living at ShortcutSettings.swift line 159: (haiku, Scary, 0), (sonnet, Fast, 1), (opus, Smart, 2), (default, Smart, 2). Any model ID whose string contains one of those substrings collapses to the right label. Opus 4.6 and Opus 4.7 both map to Smart. They are not competing picker rows; they are the same row with a freshened backing.

The else branch at ShortcutSettings.swift line 189 kicks in. If the incoming model ID does not contain haiku, sonnet, opus, or default, the Swift map falls through to the model's raw API name and assigns sort order 99. The model becomes selectable in the picker the same day, just pushed to the bottom with its unfamiliar name. A later build can add a row to the family map to give it a prettier label and a nicer sort position, but the selectability is day zero. This is how the architecture stays open to providers that Fazm does not talk to today.

Not today. The bridge that populates availableModels is the Claude agent SDK's ACP bridge, so the model list you get is whatever Anthropic is exposing through that protocol. For most of April 2026 that was Haiku 4.5, Sonnet 4.6, and Opus 4.7. Adding a non-Anthropic provider is a second bridge with its own emitModelsIfChanged, not a UI change. The UI side of the abstraction is ready for that future without any edit to the picker code. The bridge side is not written yet.

Three files. The picker itself is rendered at Desktop/Sources/MainWindow/Pages/SettingsPage.swift line 2025, inside a ForEach over shortcutSettings.availableModels. The same @Published array is read by AIResponseView.swift line 1131 for the floating bar picker. The population logic is at Desktop/Sources/FloatingControlBar/ShortcutSettings.swift lines 151 through 216, which holds defaultModels (the fallback list shown before the ACP response arrives), modelFamilyMap (the 4-row substring table), and updateModels (the function that runs the substring match and overwrites the @Published array). Every other part of the app reads this state; nothing writes to it except updateModels.

Next app launch. When Fazm starts, the ACP bridge calls session/new for each of the main, floating, and observer sessions. Each session/new response carries the current models.availableModels array. The bridge filters out the default pseudo-model at index.ts line 1274, diffs against lastEmittedModelsJson, and emits one IPC message if the list changed. Swift decodes the message, runs updateModels, and re-publishes availableModels. The keyboard-shortcut list, the floating bar's model dropdown, and the Settings preference pane all re-render in the same tick. Round trip on a warm machine is under a second.

Because the audience that downloads Fazm does not know or care what Opus is. They know that they want something smart for a hard question and something fast for a short one. The version number behind the label is irrelevant to them; by the time they have learned that Opus 4.6 exists, it is already Opus 4.7. The naming choice comes from actual onboarding sessions: when the picker showed real model names, users asked which one to pick; when the picker shows Scary, Fast, Smart, they stop asking. The tradeoff is that experienced users lose per-version control, which is why the full API name is still in the Settings detail view and in the underlying selectedModel string.

Both, a little. The single-source-of-truth picker existed before April. The dynamic population from the agent SDK shipped in Fazm 2.4.0 on April 20, 2026. The changelog line reads, verbatim, "Available AI models now populate dynamically from the agent, so newly released Claude models appear without an app update." That release was two days before Anthropic's own Opus 4.7 GA on April 22. The ordering is not coincidence; the release wave was visible, and the move to delegate the catalog to the SDK was calibrated for it.

updateModels bails at its first line with guard !acpModels.isEmpty else { return }. The @Published availableModels stays whatever it was before, which is either the previous SDK list or the defaultModels fallback defined at ShortcutSettings.swift line 151 (Scary, Fast, Smart pointing at canonical aliases). The user never sees an empty picker. The same holds if the SDK only returns one model (say because the user is rate-limited out of the others): the picker contracts, the saved selectedModel survives the shortLabel fallback chain at line 222, and the visible label stays Fast even if Sonnet is temporarily unavailable.