Subject routing

Select the subject from the capability the learner wants to build, not from the first technical noun in the request. A biological dataset may need a statistics lesson. A programming example may expose an algebra gap. A historical price series still needs historical source judgment.

Route the learning job

1. State the learner's intended action: derive, predict, implement, interpret, compare, diagnose, or argue from evidence.
2. Name the field that decides whether that action is correct. That is the lead subject.
3. Check the selected guide's prerequisites and distinctions. Add a supporting subject only for a named bottleneck.
4. Keep one lead teacher. A supporting teacher supplies one bounded bridge and returns the lesson to the lead subject.
5. Read the guide's matching subfield section when planning the course and lesson. Course design uses its starting point and likely confusions to order ideas. Lesson design uses its suggested views to explain those ideas.
6. Record the selected subject guide in the topic's skill_routes. Lesson design records media skill routes in lesson.json.

Do not route by vocabulary alone. “Gradient” does not make every optimization question mathematics; the domain subject owns what the objective and variables mean. “Code” does not make a biological inference computer science; CS owns the implementation while biology owns the claim.

Subjects and teachers

Do not invent a persona for a subject without a teacher. Set teacher to null, or assign an existing teacher only when that teacher owns a real supporting method. The subject still owns its evidence and interpretation.

Use the selected guide

Read the selected subject file in full. Its subfield map is a starting structure, not a complete taxonomy. For an unlisted specialty, inspect a primary, official, or academic source before designing a sustained course. Do not imply that an introductory textbook covers every advanced branch.

Read a linked deep reference only when the guide sends you there for detailed prerequisites, sources, examples, or visual patterns. Do not preload every subject reference.

Use python3 skills/subject/scripts/resources.py --subject physics to list curated sources. Add --query vectors to narrow the list. A catalog entry or landing page is not proof that the needed section was inspected.

Bridges

• AI and machine learning: artificial intelligence owns model and evaluation claims; CS owns implementation; math owns the needed linear algebra, probability, derivatives, or optimization.
• Biophysics: biology owns the mechanism when the question is biological; physics owns forces, diffusion, energy, or measurement for the named bridge.
• Economic history: history owns chronology and source context; economics owns an explicitly conditional model. Neither substitutes for the other's evidence.
• Quantitative biology, psychology, economics, or political science: the domain owns the question and interpretation; math owns the statistical tool.
• Chemical engineering: chemical engineering owns the system boundary and process assumptions; physics, math, and CS support transport, equations, and simulation.
• Business and accounting: business owns the operating decision; accounting owns recognition and reconciliation; economics owns the stated market model.

Carry the learner's last sound step, notation, units, and unresolved question through every bridge. Do not stage a panel discussion.

Use subject guidance in the lesson

The subject guide says what the learner must notice, work out, or check in this field. Lesson design uses that advice to choose explanations, examples, practice, and media. Read the guide before choosing blocks. A lesson may use several forms when each helps with a different step of the same idea. Every ready lesson needs at least two distinct teaching forms. The subject guide helps choose a useful pair; it does not assign a fixed pair to every topic. Exercise and feedback blocks are practice, not one of the two forms. There is no upper limit when more forms deepen the explanation. For the current topic, carry three decisions into lesson design: the concrete starting case, the distinction most likely to need explanation, and what the learner could inspect or change to understand it. Use the matching subfield section for its research checks and representation choices. Adapt them to the learner's question. Read deeper references when that section leaves a prerequisite, mechanism, or evidence question unresolved. For a visual block, specify the relation to reveal and the values or sources it must preserve. Use Excalidraw for a fixed sketch and Pinepaper when linked states, a chart tied to a scene, motion, or controls serve that relation. The media skill explains construction and export; the subject guide keeps the science or evidence correct.

For generated images, invoke the host's existing image-generation skill (such as Codex's imagegen) and follow its instructions. Give it the lesson's visual brief and keep the returned image with the course artifacts. Inspect the result before the lesson coordinator registers it. GNOS does not need a separate image-generation skill. If the host has no image-generation capability, report that and revise the representation rather than claiming an image exists.

Image generation and the MCP references use the subject route. Declare skills/subject/SKILL.md and the selected subject guide in the course topic. Declare any media producer in the lesson's skill_routes; use skills/subject/SKILL.md for a generated image block. The host skill is invoked from these instructions, so its installation path does not belong in course.json.

Several forms may explain one idea: text states the claim, a diagram shows its parts, motion shows a change, and practice checks whether the learner can use it. Give each form a distinct job. Do not recreate the same diagram in several tools or add media to meet a quota. Do not omit a useful graph, map, diagram, or control just to keep the lesson short.

For a physics lesson on a pendulum, name the system and make a prediction, draw the forces at one position, show how position and velocity change over time, then let the learner vary the starting angle. Keep the same pendulum, units, and labels throughout. For a history lesson on a policy decision, give the dated choices in prose, show the relevant documents side by side, then ask the learner to explain what each source can and cannot establish. These are examples of different jobs for different forms, not templates for every lesson.

During lesson design, read skills/lesson-design/references/representation-choices.md for the medium choices. Each delegated lesson worker receives the selected subject guide and only the deep workflow reference its block needs.

Source discipline

Read source-use.md for source selection and downloads. The lead subject decides what counts as evidence. A simulation, generated image, or explanatory animation is a model unless it directly and accurately presents a cited source.