Agent Runtime
Also called Durable execution (Durable-execution engines such as Temporal and Inngest), Runtime (Agent infrastructure discussions)
An agent runtime executes agents in production: it keeps long-running sessions alive, persists state across failures and restarts, and enforces resource and security limits.
[LangChain][OpenAI][Credal]In practice · hypothetical example
A coding agent runs for hours. Its process restarts overnight; the runtime restores the session from persisted state, and the agent resumes from its last checkpoint.
[Credal][OpenAI]A little deeper
The runtime sits below the harness. The harness decides what the agent does next; the runtime carries that work out under controlled conditions and reports results back. [Credal][OpenAI]
The label is not standardized. Official documentation applies it to durable-execution platforms, while the OpenAI Agents API announcement describes comparable capabilities as harness and infrastructure without using the word runtime. [LangChain][OpenAI]
Agent runtimes run agents in production with durable execution, streaming, human-in-the-loop oversight, and persistence. LangGraph, Temporal, and Inngest are named examples. [LangChain]
The infrastructure layer where agent work executes: sandboxed code execution, resource limits, network egress controls, credential brokering, checkpointing, and audit logs, typically owned by a platform team. [Credal]
Some platforms ship these capabilities without the label. The OpenAI Agents API describes durable sessions, automatic compaction, recovery, and managed sandboxes as its harness and infrastructure. [OpenAI]
A common mix-up
A product that never says “runtime” does not include one.
Providers name this layer differently. OpenAI presents durable sessions, compaction, recovery, and environments as harness and infrastructure. Judge the capabilities, not the label. [OpenAI][Credal]
The runtime is just another name for the harness.
The harness runs the model loop; the runtime executes that work durably and securely. Bundled products obscure the boundary, but the layers remain distinct. [Credal][LangChain]
Agent runtime refers to one vendor’s API.
The durable-runtime pattern is broader: official documentation names LangGraph, Temporal, and Inngest as agent runtimes. Any single API is one implementation of the pattern. [LangChain]
Similar terms, different emphasis
Compare Agent Harness & Agent Runtime →An agent’s process restarts mid-task. Which layer restores the session so work can resume?
Sources & editorial notes
Evidence: supported. Official LangChain documentation uses the term “agent runtime” for durable-execution platforms. OpenAI’s Agents API announcement supports the capabilities under different names and is presented here as the unnamed-bundle case. Credal’s layer analysis is vendor content, attributed as such.
- Agent Harness vs Agent Runtime: What’s the difference? ↗ (opens in new tab)Credal · 2026-04-21
Relevant section: What is an agent runtime?; How harness and runtime fit together - Runtimes, frameworks, and harnesses ↗ (opens in new tab)LangChain · Publication date unknown
Relevant section: Agent runtimes (like LangGraph); Agent harnesses (like the Deep Agents SDK) - Introducing the Agents API ↗ (opens in new tab)OpenAI · 2026-09-10
Relevant section: Build with an evolving Codex harness; Keep agents working across long sessions
Last editorial review: 2026-09-18 by project-owner.
First observed in this corpus: Unknown.
Revision history
Revision 2 · Created 2026-09-18 · Updated 2026-09-18
Project owner approved the Agent Runtime term for publication after reviewing its definitions, naming caveats, examples, and evidence.