Latest AI LLM news, April 2026: the runtime that actually delivers new models to a user's Mac

It looks like a package.json line and a subprocess spawn. Fazm's acp-bridge/package.json pins @agentclientprotocol/claude-agent-acp at ^0.29.2. When the app launches, ACPBridge.swift:343 spawns Node with exactly '--max-old-space-size=256 --max-semi-space-size=16' and hands it the ACP SDK. The SDK owns the conversation, tool calls, context compaction, and the Claude auth handshake. The 'news' (new Claude aliases, new behavior, new rate-limit telemetry shapes) arrives through that subprocess at runtime, not through a Fazm app release.

Because it runs on a user's Mac alongside everything else they have open. Desktop agents that sit resident on a laptop cannot treat RAM the way a cloud runner does. The cap is set at /Users/.../fazm/Desktop/Sources/Chat/ACPBridge.swift line 343: '--max-old-space-size=256 --max-semi-space-size=16 bridgePath'. The April 2026 news cycle is full of models that advertise 2 million token contexts. That context does not live in the Node bridge's heap, it lives on the provider's side. The bridge's job is to shuttle JSON-lines, not to hold context, which is why 256 MB is enough.

Through the ACP session/new response. When the bridge starts a session, the SDK returns an availableModels array with short aliases like 'haiku', 'sonnet', 'opus'. That array flows back through the bridge as a 'models_available' JSON line. In Swift, ACPBridge's onModelsAvailable callback hands the list to ShortcutSettings, which normalizes short aliases to full IDs (claude-haiku-4-5-20251001, claude-sonnet-4-6, claude-opus-4-6) and re-sorts via a family map. When Anthropic publishes a new Sonnet or Opus, the picker picks it up the next time the user opens the app. No Fazm binary needs to change.

Fazm ships 17 of them bundled. Desktop/Sources/BundledSkills/ contains ai-browser-profile.skill.md, canvas-design.skill.md, deep-research.skill.md, doc-coauthoring.skill.md, docx.skill.md, find-skills.skill.md, frontend-design.skill.md, google-workspace-setup.skill.md, pdf.skill.md, pptx.skill.md, social-autoposter.skill.md, social-autoposter-setup.skill.md, telegram.skill.md, travel-planner.skill.md, video-edit.skill.md, web-scraping.skill.md, xlsx.skill.md. SkillInstaller.swift copies them into ~/.claude/skills/ on first launch, compares SHA-256 digests on subsequent launches to detect updates, and also maintains an obsoleteSkills list ('hindsight-memory' currently) that gets removed on every launch. The user never has to run a skill-install command.

Five by default. acp-bridge/src/index.ts buildMcpServers (lines ~992-1100) registers fazm_tools (stdio to a Unix socket, lets Claude call back into Swift), playwright (via @playwright/mcp, with --output-mode file and --image-responses omit), macos-use (native binary for Mac accessibility automation), whatsapp (native Catalyst control via accessibility APIs), and google-workspace (bundled Python MCP for Gmail/Calendar/Drive/Docs/Sheets). User-defined servers from ~/.fazm/mcp-servers.json are appended. The set is rebuilt per session, which is why the April 2026 ecosystem news (Claude Agent SDK, MCP proliferation) actually shows up in the app's runtime rather than on a blog post.

It resizes them in-place. acp-bridge/src/index.ts line 713 sets MAX_SCREENSHOT_DIM = 1920 and watches /tmp/playwright-mcp for new .png or .jpeg files. Any screenshot that comes in larger than 1920 on either dimension gets resized before the ACP SDK ships it to Anthropic's API. The comment on the line calls out 'stay under 2000px API limit'. Retina Macs otherwise produce screenshots over 2000 that the API will reject.

Three tiers, set at acp-bridge/src/index.ts lines 77-79. TOOL_TIMEOUT_INTERNAL_MS is 10 seconds (for ToolSearch and similar internal calls). TOOL_TIMEOUT_MCP_MS is 120 seconds (for anything whose title starts with mcp__). TOOL_TIMEOUT_DEFAULT_MS is 300 seconds (for Bash, Write, Edit, Read, etc.). Users can override globally via FAZM_TOOL_TIMEOUT_SECONDS, surfaced in the app as Settings > Advanced > Tool Timeout. When a timer fires, the bridge synthesizes a 'completed' tool_activity event so the Swift UI unblocks and the model can recover, then emits a visible tool_result_display with the timeout and a fazm://settings/tool-timeouts deep link.

Yes, during a session. acp-bridge/src/index.ts handles session/request_permission by always selecting allow_always (or allow_once when only allow_once is offered). The comment on that branch notes 'matches agent-bridge's bypassPermissions behavior'. The trust model is that the user has already opted in by running Fazm. Gate logic that would otherwise interrupt the user to approve every Bash call or file write lives elsewhere in the product (Ask mode vs Act mode), not at the ACP session/request_permission layer.

Three categories. First, new Claude aliases, because they land in the picker through the models-available callback. Second, ACP SDK version bumps, because they change what the subprocess can do (new sessionUpdate kinds, new rate-limit telemetry shapes). Third, MCP ecosystem changes, because the buildMcpServers function is the ground truth for what the app wires up. Most other April 2026 news (GPT-5 Turbo multimodal, GLM-5.1 open-source MoE, Llama 4 Scout edge model, Gemini 3.1 Pro 2M context GA) does not change the default loop until someone routes a custom endpoint through the Anthropic-shape shim, because the default is Claude.

On a second loop, not through ACP. GeminiAnalysisService.swift uses model 'gemini-pro-latest' (line 67) and records analyzer runs tagged 'gemini-2.5-pro' (line 264). That loop buffers session-recording chunks, sends them for multimodal analysis, and uses function-calling into the local database. It runs independently of whichever Claude tier the chat is using. So when the April 2026 news is about a Gemini release (3.1 Pro GA, Google/Broadcom TPU deal), the part of Fazm that cares is that separate service, not the ACP bridge.

Because the ACP SDK is TypeScript and the fastest way to keep it up with Anthropic's release cadence is to not reimplement it. The bridge is ~2600 lines of TypeScript (acp-bridge/src/index.ts) that translates between ACP's JSON-RPC over stdio and Fazm's own JSON-lines protocol over stdin/stdout. Writing a native Swift port would mean chasing Anthropic's changes by hand. Spawning Node is a pragmatic call: 256 MB heap cap, a Unix socket back to Swift for fazm_tools, and the full ACP SDK riding the wave of Anthropic's April 2026 updates with a version bump instead of a rewrite.

Richer than a single 429. ACPBridge.StatusEvent includes a .rateLimit case with status, resetsAt, rateLimitType, utilization, overageStatus, and overageDisabledReason fields. This shape comes from the ACP SDK and mirrors Claude's expanded rate-limit telemetry, which arrived in the April 2026 cycle. The bridge surfaces utilization warnings before they become rejections, which is why the UI can show a 'your Claude account is at 85% of hourly limit' notice rather than only showing an error after a request fails.