Skill Injection

Per-turn skill delivery is how packs deliver domain knowledge to agents without bloating every turn with all possible context.

Source: packages/pack-core/src/tools/read_skill.ts, packages/harness/src/runtime/runner.ts

How It Works (v5 — pull-based, #1070)

The main LLM is the router. Every turn, the runner:

1. Lists every skill whose appliesTo glob matches the active agent in the system prompt under the heading ## Available Skills (call core.read_skill(id) to load the full body). Each entry is a one-line - **id**: description bullet.
2. Registers core.read_skill(id) on the agent as a harness-provided universal tool (not in any pack's toolAllowlist — policy exception).
3. When the model calls core.read_skill({ id }), the harness:
   • Re-checks matchesSkill(agent, skill) (fail-closed allowlist).
   • Enforces a per-turn byte cap (default 50 KiB; KICKSTART_SKILL_READ_MAX_BYTES_PER_TURN).
   • Returns { ok: true, id, body, tokenCount } on success, or a structured { ok: false, error, message } on failure (never throws).
   • Records the id in session.skillsPulled for D12 telemetry.

The model chooses which skills matter based on full conversation context. Repeated reads of the same id within a turn return the cached body without re-charging the byte budget.

Security note for pack authors: SKILL.md bodies are LLM-visible whenever the model reads them via core.read_skill. Do not embed secrets, API keys, or customer data in skill content.

Skill Authoring

Skills live in SKILL.md files inside pack skills/ directories:

---
name: AKS Node Pool Sizing
appliesTo: "aks.*"
keywords:
  - node pool
  - vm size
  - cluster scaling
priority: 80
---

When recommending node pool sizes for AKS Automatic, prefer ...

Frontmatter field	Required	Description
name	✅	Human-readable skill name
appliesTo	✅	Agent name glob — which agents receive this skill
keywords	✅	Currently unused by the pull model (reserved; #1070 v5)
priority	optional	Currently unused by the pull model (reserved; #1070 v5)

Where Skills Live

Pack	Skills directory
pack-core	packages/pack-core/src/skills/
pack-azure	packages/pack-azure/src/skills/
pack-aks-automatic	packages/pack-aks-automatic/src/skills/
pack-github	packages/pack-github/src/skills/

Skills are loaded at pack registration time by the SKILL.md loader in packages/harness/src/runtime/loader-skill.ts.