Neubig splits tool use into five layers: capabilities, mechanics, constraints, interfaces, and systems. A tool call is just tokens the model emits; the harness parses, validates, and matches results back by call ID. Constrained decoding guarantees form, not correctness. MCP's real value is credential brokering. And the same model served by different providers can swing from roughly 15% tool-call errors to under 0.1%.
An agent resends its whole history on every call, so five calls already add up to 80K input tokens; 1,500 OpenHands sessions averaged 78K tokens, 37% of them tool results. Neubig works on two layers: at the model layer, hybrid attention (many local layers, one global) plus length curricula make million-token context possible; at the harness layer, stable prefixes earn cache reads roughly ten times cheaper, and compaction that keeps anchors and externalizes evidence gets past the limit — evaluated by how the agent continues afterwards.
Lecture 4 of CMU 11-768 sorts cross-task experience into episodes, facts, and skills, stored as external artifacts rather than in context or weights. Human-written skills load through SKILL.md and progressive disclosure, lifting the average SkillsBench pass rate from 33.9% to 50.5%. Skills an agent induces itself can be tested before admission when written as code, but break easily on a new website. The hard part is the lifecycle: imperfect judges, over-retrieval, and bloated skill libraries each eat into the gains.
Lecture 5 of CMU 11-768 defines an agent's plan as an explicit, inspectable, revisable representation of intended behavior for this task, and gives four reasons to add planning structure: modularity, environment feedback, long horizons, and control. Fried's own MACU has a manager decompose tasks into a DAG and dispatch parallel sub-agents, raising Odysseys success from 8.5% to 34.0%; on an OSWorld subset, no planning scores 25.0%, an initial DAG with no revisions scores 27.8%, and allowing 10 revisions reaches 58.3%.
Neubig's L6 splits coding agents into three layers: train a model that can code (pre-training, mid-training, infilling, RL from test rewards), wrap it in a localize–edit–verify loop with the right editing tools so it can change a repo, then evaluate and train it in SWE-bench-style executable environments. Fixing bugs is only about 15% of a developer's day; the next frontier is tests, CI, and maintenance in the outer loop.
JY Koh breaks computer use agents into three questions: evaluation has moved from single clicks (ScreenSpot-Pro, Mind2Web) to programmatic end-state checks (WebArena, OSWorld), VLM judges, and long-horizon rubrics (Odysseys, OSWorld 2.0); the model is a VLM reading interleaved screenshots and actions; training runs pre-training for grounding → SFT on human and synthetic trajectories → RL in resettable simulated environments.
Yueqi Song breaks agent SFT into six decisions: compute loss on assistant tokens only (including the stop token); choose trajectories carefully (runs that pass tests can still teach bad habits, and switching teachers or adding new tasks beats sampling more); unify formats with the Agent Data Protocol; watch packing and template drift during training; evaluate in the real harness; and pick the SFT checkpoint for the RL that follows, not for its own best score.
Using a guess-a-number-from-1-to-16 game, Daniel Fried frames RL as an extension of SFT: he names SFT's three gaps (task mismatch, no learning from failures, never seeing its own mistakes), then derives ReST, REINFORCE, baselines, and GRPO/DrGRPO in turn. All four compute log-probabilities of the tokens the agent itself generated; they differ only in the weight each token gets.
Akari Asai's L10 splits deep research agents into three problems: evaluation has to cover four gaps (search difficulty, domain expertise, long-form answer quality, citation support); training runs mid-training → SFT → RL, with DR Tulu's evolving rubrics as the reward for long-form reports; retrieval should let the retriever see the agent's reasoning, which gets AgentIR-4B to 68% on BrowseComp-Plus with Tongyi-DR.
Using a bug-fix coding task, Graham Neubig takes Lecture 9's policy gradient into practice: a critic, GAE, or a PRM to credit individual turns; importance ratios and clipping to handle stale data in async RL; and PPO, GRPO, CISPO, GSPO, and DAPO side by side in one table. The largest share goes to the reward itself — verifier errors, reward hacking, and exploration collapse — before closing with on-policy distillation.
learn-inference.com is an unofficial interactive companion to Philip Kiely's Inference Engineering (256 pages, Baseten Books, free PDF). It follows the book's 8 chapters and 42 sections with rewritten explanations, turns intuition-heavy ideas like TTFT, P99, speculative decoding, and prefix-cache routing into slider-driven simulators, and ships a keyless JSON API and MCP server.
Obscura is a headless browser engine written from scratch in Rust. It embeds V8 and speaks the Chrome DevTools Protocol, so Puppeteer and Playwright scripts connect by changing one endpoint, and it ships an MCP server with 37 tools. The headline numbers (about 30 MB per process, about 85 ms per page load) come from the project's own benchmarks; it passes 83.3% of its core WPT subtests, and long-tail CSS and some Web APIs still differ from Chromium.
Traditional chat only needs text bubbles, but AI Agent conversations must surface thinking, tool calls, citations, and progress — we solved this with 12 Vue components, three DisplayModes, and a unified chatBlocks rendering pipeline.
In H1 2026, OpenAI, Anthropic, Letta, and LangChain independently chose Markdown files + indexes over vector databases; write permissions shifted back to humans; forgetting mechanisms appeared but nobody implemented Ebbinghaus; Penfield Labs caught 6.4% wrong answers in LoCoMo; three vendors simultaneously adopted 'Dreaming' for offline memory consolidation. Five trends, one conclusion: memory is not a feature — it is an architecture decision.
Memory turns prompt injection from a one-shot nuisance into a persistent backdoor: MINJA shows conversation-only injection succeeds >95% of the time, and SpAIware demonstrated continuous data exfiltration via planted memories. The industry's two defensive lines — citation-based verification (Copilot) and human approval inboxes (Gemini CLI / Devin) — each have blind spots.
Agent memory is not one feature — it is at least four distinct engineering problems: working, episodic, semantic, and procedural. This ten-part series walks through the full design space, from taxonomy to coding agent implementations, platform APIs, open-source frameworks, security attack surfaces, and 2026 trend analysis.
CoALA splits agent memory into working, episodic, semantic, and procedural — but the four-cell taxonomy alone doesn't explain why Claude Code uses Markdown files while Mem0 uses vectors. This post adds six independent design axes (read mode, write timing, fidelity, write authority, forgetting, scope) and a file-to-graph spectrum to map the full design space of agent memory systems in 2026.
The previous articles covered evaluation. This one covers another dimension: how to dynamically allocate compute during reasoning. BrowseConf's core insight is that an agent's self-declared 'confidence' can predict answer accuracy. High confidence uses fewer resources; low confidence searches more rounds.
All five major cloud platforms shipped agent memory APIs in 2025–2026, but their design philosophies diverge sharply: OpenAI writes memory as files, Anthropic mounts memory as a directory, Google uses vectors with topic classification, AWS combines events with pluggable strategy pipelines, and Microsoft abstracts memory behind context providers. Pricing ranges from free to $0.75/1K records/month; tenant isolation spans from 'your app handles it' to IAM as a first-class citizen.
Nine coding agents have taken at least four different paths for long-term memory: Claude Code and Codex use Markdown files (agent-written, human-readable), Antigravity CLI inherits Gemini CLI's approval inbox (agent proposes, human decides), and Copilot uses citations with JIT verification (auto-deleted after 28 days unverified). Cursor removed its Memories feature and fell back to human-written Rules. Hermes Agent, OpenClaw, and Letta Code treat memory as a core harness component, not a plugin. Their choices on write timing, forgetting, and cross-team sharing are completely different — and none has published a controlled experiment on whether their memory system actually helps.