Anthropic April 2026 news, absorbed with zero app updates

The month had five distinct stories. Claude Opus 4.7 went generally available at the same $5 / $25 per MTok pricing as Opus 4.6, with stronger SWE, sharper vision, and more reliable long-running tool use. Claude Mythos was previewed through Project Glasswing, a gated program to a ~50-org partner set that includes Amazon, Microsoft, Nvidia, Apple and JPMorgan, with no public release date. Claude Design launched as a new Anthropic Labs product for designs, prototypes, slides, and one-pagers, powered by Opus 4.7. On April 6 Anthropic expanded its Google Cloud and TPU footprint. In the background, the Long-Term Benefit Trust appointed Vas Narasimhan to the Board of Directors on April 14, and Dario Amodei met with White House Chief of Staff Susie Wiles and Treasury Secretary Scott Bessent about federal access to Mythos after the Pentagon flagged supply-chain-risk concerns. That is the full news bundle.

Nothing on the client side. The ACP bridge does not hard-code model IDs in its model picker. Every time the bridge calls session/new or session/resume against Claude, the response payload includes models.availableModels as an array of { modelId, name, description }. The bridge filters out the default pseudo-model, diffs against the last emitted list, and sends { type: "models_available", models: [...] } as one line of JSON over stdout. The Swift app decodes that and re-renders the model list. This logic lives in emitModelsIfChanged at acp-bridge/src/index.ts lines 1271 through 1281. When Anthropic added Opus 4.7 to the Claude SDK's model catalog, the bridge started listing it on the next session without a single line changing in Fazm.

Yes, literally. The entry for 2.4.0 dated 2026-04-20 in CHANGELOG.json says 'Available AI models now populate dynamically from the agent, so newly released Claude models appear without an app update.' That line describes the emitModelsIfChanged flow above. The same release also upgraded Claude agent protocol to v0.29.2 and added custom MCP server support via ~/.fazm/mcp-servers.json with Settings UI to add, edit, and toggle servers.

Through a single file at ~/.fazm/mcp-servers.json. The format mirrors Claude Code's mcpServers object: { "server-name": { "command": "...", "args": [...], "env": {...}, "enabled": true } }. When the ACP bridge builds the MCP server list for a session it appends anything in that file to the built-in servers (fazm_tools, playwright, macos-use, whatsapp, google-workspace). The load is at acp-bridge/src/index.ts lines 1102 through 1137. The Swift-side manager that reads and writes the same file is MCPServerManager.swift, with the config URL computed on line 42 as FileManager.default.homeDirectoryForCurrentUser.appendingPathComponent(".fazm").appendingPathComponent("mcp-servers.json"). Any MCP server Anthropic or a third party ships this week is one edit away.

Launch Fazm, open the chat, click the model picker in the header, pick Opus 4.7 from the list. That was it. No app update prompt, no re-login, no Settings trip. The bridge surfaced Opus 4.7 automatically the first time a new session was created against the updated SDK. The paywall mechanics are unchanged: the 2.4.0 release note shortened the free trial to 1 day and moved the paywall to after 3 messages for all users including built-in mode, but that is separate from model availability.

No. Mythos is gated behind Project Glasswing. If Anthropic does not expose it in your SDK session, the bridge will not list it. The dynamic mechanism does not unlock anything for you that Anthropic has not already unlocked on the server side; it just removes the client-side lag once they do. For GA models like Opus 4.7 the lag is zero. For Glasswing-restricted models like Mythos the answer is the same it was on April 1, you need to be on that partner list.

Yes, indirectly. Fazm's default model is set on the bridge side at acp-bridge/src/index.ts line 1245 as claude-sonnet-4-6, and Sonnet 4.6 is pre-warmed alongside the user's active model. A user who does not want to touch a new model simply does not pick it in the header. There is no per-model kill switch in the UI yet, but a user with concerns can also edit the bridge source locally since Fazm is MIT-licensed open source and clone it from fazm.ai/gh.

Through Claude Code's ACP layer. Fazm does not embed the Anthropic REST SDK in the Swift app. Instead the app spawns a Node.js subprocess called the ACP bridge (source at acp-bridge/src/index.ts) that speaks Anthropic's Agent Client Protocol and manages the Claude Code SDK connection. The Swift desktop app talks to the bridge over stdin and stdout as JSON lines. That means Fazm inherits Claude Code's model catalog, OAuth flow, rate-limit handling, and tool-call shape for free, and the dynamic model list described above is a byproduct of that architecture.

Most desktop AI clients bake the model list into a dropdown that gets hydrated from a hard-coded array at build time. When Opus 4.7 shipped, those apps needed to cut a release, update an enum somewhere, run QA, submit to a notary or the Mac App Store, and push an update to users. That cycle typically takes days to a week. Fazm's cycle is zero, because the truth lives in the ACP session response, not in the binary. The v2.4.0 release that introduced this behavior shipped on 2026-04-20, after the Opus 4.7 GA and after the Claude Design launch, which are exactly the sort of news items the mechanism is designed for.

Yes, and this is the honest answer: anything that changes Anthropic's wire protocol in a backwards-incompatible way. A new event type on the ACP channel would land as 'unknown message type' in the Swift decoder at ACPBridge.swift around line 1140 and would silently drop. A breaking change to tool-call shape would require a bridge upgrade. The v2.4.0 release bumped to ACP v0.29.2 precisely to stay ahead of those shape changes. For news items that are pure additions, new models, new MCP servers, new Claude Design capabilities accessed through existing tool calls, the client picks them up for free. For shape-breaking changes, a real release is still required.

It is MIT-licensed and on GitHub. The landing page fazm.ai/gh redirects there. The two paths quoted in this article are acp-bridge/src/index.ts (the Node.js bridge) and Desktop/Sources/Chat/ACPBridge.swift plus Desktop/Sources/MCPServerManager.swift (the Swift-side decoders). Line numbers in this article match the current HEAD at time of writing.