build-agent-harnesses

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.

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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.

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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/.

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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.

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Output to user

1. Name the workflow (A–L) and what you are producing
2. Save artifacts under ./skill-outputs/build-agent-harnesses/ when the user wants files
3. Do not auto-commit

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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