Build agent harnesses
Action playbook from twenty-two AI Engineer talks on agent & harness engineering. Do not summarize talks — pick a workflow and execute it.
Supporting files (read when needed):
- workflows.md — workflows A–L (steps, deliverables, stop conditions)
- source-index.md — src-NNN → talk learnings in ingest-into-skills
Optional deliverables: {SKILL_OUTPUT_DIR}/build-agent-harnesses/ — see skills-i-use OUTPUT.md.
Step 0 — Pick workflow
Use the decision tree below. Open the matching section in workflows.md.
What is the user trying to do?
├─ Define harness vs agent loop + guardrails/verify → A
├─ Decide agent vs workflow for a use case → B
├─ Maturity path: framework → state machine → scale → C
├─ Enterprise: quotas, skills, multi-agent platform → D
├─ Agent evaluation + anti-hype discipline → E
├─ Long-horizon research / deep research harness → F
├─ Coding agent / computer-use / IDE harness → G
├─ Production chat UX: resume, steer, multi-device → H
├─ Operate many parallel coding agents (FOMAT) → I
├─ Regulated / domain-vertical knowledge agents → J
├─ Delete scaffold; maximize LLM compute in backend → K
└─ Post-training / finetune / RL for tool agents → L
Stop summarizing once a workflow is identified — run its checklist.
Install
cp -r skills/build-agent-harnesses ~/.claude/skills/
cp -r skills/build-agent-harnesses ~/.cursor/skills/
cp -r skills/build-agent-harnesses ~/.codex/skills/
From skills-i-use or ingest-into-skills after sync.
Source corpus: ingest-into-skills playlists/agent-harness-engineering-ai-engineer/.
Cross-cutting rules
| Rule | Source |
|---|---|
| Harness = tools + context + guardrails + verify around the model | [src-001 @ 4:36] |
| Do not prompt harder when verify shows failure — fix harness | [src-001 @ 9:37] |
| Agents only when ambiguity/value/error profile justify cost | [src-002 @ 2:57] |
| Every agent is a state machine; prune prompts as models improve | [src-003 @ 4:37] |
| Agent eval needs environments + actions, not I/O strings only | [src-006 @ 7:52] |
| Decouple clients via durable sessions for resume/steer | [src-015 @ 5:25] |
Disputed steps: read talk in source-index.md.
Output to user
- Name the workflow (A–L) and what you are producing
- Save artifacts under
./skill-outputs/build-agent-harnesses/when the user wants files - Do not auto-commit
Invocation examples
@build-agent-harnesses design a harness for our browser agent
agent vs workflow for this support bot?
we need quotas and verify steps for production agents