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Probe has a small vocabulary. Most confusion comes from two words that sound interchangeable and are not: an experiment carries a question, a run carries an execution. Get that one right and the rest follows.

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The spine

Every level can carry artifacts, notes, tags and lineage edges. Nothing above a run is required for a run to exist.

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Workspace

A place to file projects and files. Not an ownership boundary — every member of the team reads every workspace, and that is a product decision, not an omission. What a workspace can restrict is who may edit what is filed in it, through access groups and writer lists. Teams use workspaces the way you would use folders: engineering, wandb-imports, one per external integration. Connecting Weights & Biases or Benchling creates a dedicated workspace and asks you what to call it.

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Project

The top of the data model, and the unit a person thinks in. A project declares a kind, from a closed vocabulary, and the kind decides how its dashboard page is laid out: Kind reaches the project page only. It never restructures an experiment or a run. Projects nest: a phase of a bigger effort is a subproject (probe project create --parent), never a new top-level sibling. Projects can also reference each other laterally — use that when a review informed a training run, or two efforts share a method, where a parent relationship would claim something false.

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Experiment

One question, and the runs that answer it. The question field is the point of the entity; if you cannot write one, you probably want a project-direct run instead. The question is first-write-wins: reopening an experiment never rewrites it. That is deliberate — an experiment whose question drifts to match its results has stopped being an experiment. An experiment can be frozen into an immutable version that pins its current run set (probe experiment freeze), which is what you cite when the numbers go into a paper or a decision.

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Run

One execution. It holds:
  • metric series, each identified by (kind, key, dimensions)
  • artifacts — the files it read and produced
  • spans — a trajectory: rollouts, turns, tool calls
  • a code snapshot — what was on disk when it started
  • lifecycle: running → completed / failed / canceled, plus a heartbeat so a crashed run is reaped rather than left open forever
Runs relate to each other three ways. A child run nests under a parent. A fork continues a source run from a step, leaving the source untouched. A group collects peers — a sweep, an ensemble, the ranks of one distributed job.
Creation rules differ by surface on purpose. The SDK creates projects, experiments and runs freely, because a training script should not fail on a missing row. On the CLI, probe run start never creates — the slug is hand-typed every time, and that is where typos come from. A near-miss of an existing slug is refused, not created.

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Artifact

A file, anchored somewhere. The anchor is what makes artifacts useful rather than a dumping ground: Artifacts are content-addressed and deduplicated by SHA-256, and they version: appending the next version keeps the chain. Versions never supersede by name — two artifacts with the same name coexist and are ordered by creation. Bytes do not have to leave your infrastructure: an artifact can be a reference to an object you keep in your own bucket, with the pointer and checksum recorded in Probe.

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Prose: three homes, deliberately

This is the distinction people get wrong most often.

description

The short identity line. One or two sentences. Shown everywhere the entity is listed.

Overview

summary_markdown — the durable, teammate-facing document, shown below the AI summary on the entity page. Whole-document, last-write-wins.

notes

The operational briefing agents read and write. Supports append, titled sub-notes, and merge-on-push editing.
On top of those there is one team note: a single shared document injected into every agent session on every machine. It is working memory for the whole team, and it has a render budget — a note past it reaches nobody.

Notes in full

Checkout/push editing, sub-notes, the team note, and the rules for writing one.

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Session

A coding-agent conversation. With capture on, sessions stream into the knowledgebase and become searchable: the prompts, the replies, and the shell commands. A session can also be attributed to a run, which is how “why was this run launched” stays answerable.

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Lineage

Edges between entities — run to run, run to artifact, artifact version to artifact version, paper to paper. Lineage is what lets you ask what produced a checkpoint, or which paper led to which.

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Tags

Free-form labels on projects, experiments, runs and papers. Filtering by several tags is AND, not OR.

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The switch

For coding agents there is one more concept: the per-conversation switch. Only the researcher moves it. An agent invoking the skill loads guidance and never changes the state. See the /probe skill.