agent brief/2025-11-29

Opus 4.5 takes the lead.

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Anthropic has aggressively redefined the agent landscape with the release of Opus 4.5, which now dominates benchmarks like SWE-Bench with an 87% success rate using sub-agents. Beyond raw performance, the model introduces a 3x cost reduction and persistent memory features, making long-horizon, autonomous engineering workflows commercially viable for the first time. Parallel to this, DeepSeek-Math-V2 is proving that architectural innovation rivals scale. By utilizing a generator-verifier loop and reinforcement learning, it achieved the first open-source Gold on the IMO, showcasing a reasoning pattern that is likely to become standard for reliable agentic thought processes. However, as capabilities scale, so do the attack vectors. Security expert Simon Willison issued a critical clarification this week distinguishing prompt injection from jailbreaking, noting that tool-using agents (such as those on MCP servers) face unique risks of data exfiltration that current guardrails cannot reliably stop. The industry is moving fast: agents are becoming smarter and cheaper, but the security layer remains dangerously thin.

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