Context Budgeting

Every token in context is a cost you pay every turn. This skill is the discipline that keeps long sessions cheap and coherent.

Token arithmetic

Rough budget on a 200K-context model:

Consumer	Typical	Budget
System prompt + CLAUDE.md	3–8 K	≤ 10 K
Skills frontmatter (all active)	2–6 K	≤ 8 K
MCP tool schemas (passive)	5–25 K	≤ 15 K
Hook definitions	<1 K	<1 K
Conversation history	variable	~120 K
Working headroom	—	≥ 20 K

If passive context (everything before conversation history) exceeds 30 K, optimize.

Three-tier loading (skill-creator canonical)

Tier	What	Size	Loaded
1 — Frontmatter	name + description	~50 tokens	always
2 — Body	SKILL.md after frontmatter	≤ 500 lines	on activation
3 — References	references/*.md, MCP KB artifacts	unlimited	on demand

Rule: if content doesn't change Claude's behavior every session, it belongs in tier 3.

/compact strategy

/compact condenses conversation history when it's filling up. It does NOT touch system prompt, CLAUDE.md, or skills.

When to /compact:

• Conversation > 60 K tokens.
• About to start a new phase (logical break).
• Many long tool outputs in history.

When NOT to /compact:

• Mid-debugging where specific earlier context matters.
• Right before an important decision — the lost nuance might bite.
• After a fresh /clear (nothing to compact).

Anchor preservation: before /compact, save anything you'd lose to engram via mem_save. After compact, the post-compact-context-restoration hook re-loads memory rules and recent context.

/clear vs /compact

Command	What it does
/compact	Summarize history, keep system prompt + CLAUDE.md
/clear	Wipe everything including CLAUDE.md — fresh session

Use /clear between unrelated tasks. Use /compact mid-task.

Subagent delegation for context pressure

When a single subtask would consume too much context (e.g. scanning a huge codebase), delegate to a subagent. The agent gets a fresh window; you only see its report.

Agent({
  description: "Inventory all API endpoints",
  prompt: "Scan src/api/ recursively, list every route with method, auth requirement, and response schema. Report under 500 words."
})

Net: the scan consumes agent tokens; your session only pays for the 500-word summary.

Session analytics

Track cost patterns:

Metric	Target
Passive context (pre-conversation)	≤ 30 K
Cost per turn	≤ $0.05 (Sonnet), ≤ $0.15 (Opus)
Tools loaded but never called per session	0 (prune unused MCPs)
/compact frequency	every 20–30 exchanges on long sessions
Subagent delegation rate	~1 per 5 substantive turns

Session analytics isn't automatic — periodically review what's consuming tokens and trim.

MCP delegation

Need	Tool
Settings schema for compact config	cc_docs_settings_schema
Compact/budget troubleshooting	cc_docs_troubleshoot("context")
Model cost for budgeting	cc_docs_model_recommend(task, budget)

Anti-patterns

• Loading every skill body "just in case" → tier-2 explosion.
• Massive CLAUDE.md with all conventions inline → routing fails + budget bloat.
• Never compacting → session hits wall, Claude forgets the plan.
• Compacting mid-critical-reasoning → loses the thread.
• Global MCPs for project-specific work → 15 K tokens for tools you never call.

Reference

• compact-strategies.md — when to compact, anchor checklist, post-compact recovery