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AI Daily Brief — 11 March 2025

March 11 belonged almost entirely to OpenAI. The lab unified its agent platform with a single coordinated launch — the Responses API as the new primitive, an open-source Agents SDK to orchestrate them, and three hosted tools (web search, file search, computer use) baked in. Celestial AI’s $250M round provided the day’s infrastructure counterweight.

Top stories

  • OpenAI launches Responses API as the new agent primitive. A new HTTP API combining Chat Completions’ simplicity with the Assistants API’s stateful tool-use, powering the same stack behind Deep Research and Operator. Available to all developers at standard token rates. The Assistants API was simultaneously placed on a deprecation path. via OpenAI
  • Agents SDK open-sourced, successor to Swarm. Production-grade framework for multi-agent workflows with built-in tracing, guardrails, handoffs and sessions — supersedes the experimental Swarm framework from October 2024 and supports non-OpenAI models including Anthropic, Google, DeepSeek, Qwen, Mistral and Llama. via VentureBeat
  • Web search tool ships in the API with dedicated models. Two fine-tuned variants — gpt-4o-search-preview and gpt-4o-mini-search-preview — landed in both Chat Completions and Responses APIs. Pricing: $30 per 1,000 queries (full) and $25 per 1,000 (mini). via OpenAI
  • File search built-in tool with hosted retrieval. Priced at $2.50 per 1,000 queries plus $0.10/GB/day storage (first GB free), it brings RAG-style document retrieval into agent workflows without external vector DBs. via InfoQ
  • Computer-Using Agent (CUA) model debuts in the API. The model powering Operator surfaced as a research preview for tier 3-5 developers at $3 per million input tokens and $12 per million output tokens — autonomous browser/desktop control as a callable hosted tool. via OpenAI
  • Celestial AI raises $250M Series C1 at $2.5B. The photonic-interconnect startup’s round was led by Fidelity, with BlackRock, Tiger Global, Maverick Silicon and Lip-Bu Tan as new investors; AMD Ventures, Temasek/Xora and Porsche SE returned. Total funding now exceeds $515M; mass production of Photonic Fabric targeted for 2027. via BusinessWire

Who shipped

OpenAI ran the day end-to-end: Responses API as the new agent primitive, open-source Agents SDK as the orchestrator, three hosted tools (search, files, computer use) as the building blocks, and a public Assistants API deprecation path. Celestial AI closed the infra side.

Open-source pulse

The Agents SDK shipped open-source from day one, with first-class support for Anthropic, Google, DeepSeek, Qwen, Mistral and Llama models — an unusually broad multi-vendor stance from OpenAI, signalling that orchestration is now the moat, not the underlying model.

Money, infra & hardware

Celestial AI’s $250M Series C1 intensified the optical-interconnect race ahead of NVIDIA GTC, where silicon photonics was expected to feature heavily. via SiliconANGLE Competitors Ayar Labs and Lightmatter are working the same problem: replacing copper interconnects in hyperscale training fabrics.

Quiet corners

No major Anthropic, xAI, Meta or Microsoft launches surfaced for the date — all eyes on OpenAI’s coordinated push. No notable arxiv landmark for March 11.

By the numbers

  • 5 — distinct OpenAI products announced in one day
  • $30 / $25 / $2.50 / $3 / $12 — per-1K-query and per-Mtoken prices across the new tools
  • $250M — Celestial AI raise; $2.5B valuation
  • $515M+ — Celestial AI total funding to date
  • Most-mentioned company: OpenAI

Compiled by AI Feed’s editor from verified web sources for 11 March 2025.