Glossary
Headless agent
Nobody is typing at it, so its output is actions and artefacts rather than replies.
Definition
A headless agent is an AI agent that runs without a user-facing interface. Instead of a person typing into a chat window, it is started by an API call, a webhook, a schedule, a queue message or a database change, and its output is actions and artefacts (a written file, an updated record, a sent message) rather than a conversational reply. The term borrows from headless CMS and headless commerce.
- Term lineage
- Headless CMS, headless commerce
- Trigger
- Event, schedule, queue, API
- Output
- Actions and files, not replies
What headless actually removes
In web architecture, headless means the system has no presentation layer of its own: a headless CMS stores and serves content that some other front end renders. Applied to agents, the head that is missing is the chat interface. The reasoning, tool use and model calls are unchanged; what disappears is the assumption that a human is present to read a response and type the next turn.
That absence changes the engineering. A headless agent has to decide when it is finished without anyone confirming, has to fail in a way an operator can diagnose later, and has to leave a record, because there is no transcript anybody watched.
How headless agents are usually triggered
Four patterns cover most production deployments.
Queue message
A row or message representing a unit of work is claimed by a worker process. The most common pattern where ordering, retries and concurrency limits matter.
Webhook or event
An external system fires on a state change, such as a ticket created, a payment failed or a pull request opened, and the agent handles it.
Schedule
A cron expression runs the agent periodically: a nightly report, a weekly audit, an hourly inbox sweep.
Direct API call
Another program invokes the agent synchronously and consumes its structured result, treating it as a function with judgement.
Commonly confused with
| Term | What it describes | The difference |
|---|---|---|
| Autonomous agent | How much latitude the agent has over its own steps | A property of decision-making, not of interface. An agent can be headless and tightly scripted, or interactive and highly autonomous. |
| Background job | Deferred work executed outside a request cycle | Runs a fixed procedure. A headless agent chooses its steps at run time. |
| Batch processing | Large volumes of records processed on a schedule | Uniform work, no per-item reasoning. |
| Daemon | A long-running system process | Describes process lifetime. A headless agent is usually invoked per unit of work and exits. |
The observability problem
The defining operational fact about headless agents is that nobody saw what happened. Interactive agents get corrected mid-run by the person reading along; headless ones do not. Every serious deployment therefore pairs the agent with a durable record of its steps: tool calls, searches, files produced, and the criteria it believed it satisfied.
Polaris runs its AI workers headless, claiming jobs off a queue with a machine on Fly.io, and pairs each run with a work log and progress comments posted onto the task, so the run can be read after the fact by whoever reviews the delivery.
Related terms
Autonomous agent
Autonomy is a range, and the interesting question is where the boundary sits.
Agent runtime
Not the model, not the framework: the thing that actually runs the job.
Task queue
The thing that lets a request survive the process that made it.
Work log
The record that makes an unwatched run reviewable afterwards.
How long an agent session can run, and what happens when it ends
Every agent runtime has bounds. The useful thing a vendor can do is tell you what they are.
The audit trail behind every agent session
If you cannot reconstruct what happened three weeks later, you do not have an audit trail. You have a feeling.
Questions people ask
+Is a headless agent the same as an autonomous agent?
No, and conflating them is the most common error with this term. Headless describes the interface: no chat window, triggered programmatically. Autonomous describes latitude: the agent chooses its own steps. A headless agent following a rigid script is neither autonomous nor unusual.
+Can a headless agent ask a human a question?
Yes, through an asynchronous channel rather than a live turn. Common patterns are posting a comment and pausing, opening an approval request, or escalating to a queue a person monitors. The agent cannot block on an answer the way an interactive one can, so the design has to handle nobody replying.
+What are headless agents good for?
Work that is triggered by systems rather than people, or that takes longer than someone will sit and watch: overnight research, recurring reports, ticket triage, document generation. Anything requiring rapid back-and-forth clarification is a poor fit.
Related
Autonomous agent
Autonomy is a range, and the interesting question is where the boundary sits.
Agent runtime
Not the model, not the framework: the thing that actually runs the job.
Task queue
The thing that lets a request survive the process that made it.
Work log
The record that makes an unwatched run reviewable afterwards.
Cloud development environment
The compute, filesystem and toolchain live somewhere else, and are usually thrown away afterwards.
How long an agent session can run, and what happens when it ends
Every agent runtime has bounds. The useful thing a vendor can do is tell you what they are.
What keeps running after you close the lid
The honest version: nothing on your laptop survives, so the work has to not be on your laptop.