# Context Budget Discipline > Use when sessions run long, adding subagents, fetching large files, or planning context-heavy work. SELECT/WRITE/COMPRESS/ISOLATE discipline. - **Type:** Skill - **Install:** `agentstack add skill-redtropig-harness-anchor-context-budget-discipline` - **Verified:** Yes — security-reviewed for prompt injection and unsafe behavior - **Seller:** [Redtropig](https://agentstack.voostack.com/s/redtropig) - **Installs:** 0 - **Category:** [AI & ML](https://agentstack.voostack.com/c/ai-and-ml) - **Latest version:** 0.1.0 - **License:** MIT - **Upstream author:** [Redtropig](https://github.com/Redtropig) - **Source:** https://github.com/Redtropig/harness-anchor/tree/main/skills/context-budget-discipline ## Install ```sh agentstack add skill-redtropig-harness-anchor-context-budget-discipline ``` Requires the [AgentStack CLI](https://agentstack.voostack.com/docs/cli). Works with Claude Code, Cursor, and any MCP-compatible agent. ## About # Context Budget Discipline Context is a finite resource. Every token competes for the model's attention. The "lost-in-the-middle" phenomenon is real — content buried in 50% of the window position is least attended. This skill applies four operations to keep the budget sane. ## The Four Operations ``` SELECT load context just-in-time, not all-at-once WRITE persist to disk; let the filesystem remember, not chat COMPRESS summarize older turns when window fills ISOLATE delegate so child work doesn't pollute parent context ``` ### SELECT — pull, don't push Default behaviour: don't preemptively load files. Wait until they're needed. - ❌ "Let me read all 30 .cpp files to understand the project." - ✅ "I'll consult PROJECT-TOC.md first, then read only the 2 files the task touches." ### WRITE — disk is cheap, context is expensive Anything reusable across turns should live on disk: - Active feature → `feature_list.json` - Decisions / rationale → `progress.md` or `docs/decisions/` - "What I just did" → `session-handoff.md` Anti-pattern: re-explaining the same plan/decision in every reply. ### COMPRESS — summarize old turns when window pressure rises When context usage > 70% of model window, mid-session compaction can help. But per [Anthropic Nov 2025](https://www.anthropic.com/engineering/effective-harnesses-for-long-running-agents): > "Compaction preserves continuity, but doesn't give the agent a clean slate. Context anxiety can still persist." **Flush before you compress.** Before compaction/reset — or when the PostToolUse watermark fires (T1 "Context is filling" = flush now; T2 "Context is heavily filled" = wrap up via /session-end + fresh session) — write chat-only durable memory to disk first: golden-rule stubs (`capturing-golden-rules`), feature status, a milestone `progress.md` entry. After a compaction, do NOT backfill memory from the summary: reconstruct from on-disk evidence (git diff, test output, progress.md) and state uncertainty where evidence is missing. If compaction isn't enough → use `/session-end` to write a rich handoff, then suggest the user start a **fresh context** (context reset > compaction for long runs). ### ISOLATE — child work doesn't bleed up Subagents (`/verify`, `cpp-build-doctor`, etc.) run in **fresh context**. They: - Don't inherit conversational baggage - Return a fixed-structure result (diagnosis / evidence / recommendation) - Don't dump their working notes into your context If you delegate a noisy task, ask for a SUMMARY back, not a transcript. ## Token Budget Reference | Tier | Budget | Source | |---|---|---| | Tier 1 (always loaded) | ~3000 tokens cap; measured at v0.10.0: generic ≈1160 t, C/C++ ≈1580 t | SessionStart hook injection (hard-capped 12000 chars, meta-skill injected slimmed; `${CLAUDE_PLUGIN_ROOT}/scripts/measure-context.sh` re-measures both baselines) | | System prompt + tools | Model-defined | Outside your control | | Working context | Most of remaining window | Your edits + reads accumulate here | ## State-file budgets Hot state files carry fixed budgets. The SessionStart banner warns (warn-only) when one is exceeded; `/session-end` offers deterministic archival via `state-archive.mjs`. | File | Hot window | Sentinel | |---|---|---| | `progress.md` | newest 20 sections | 64KB | | `feature_list.json` | live features + 10 newest `pass` | 32KB | | `golden-rules.md` | prune — never archived | 8KB | | `AGENTS.md` | keep it a map (~80 lines) | 8KB | | `session-handoff.md` | overwritten each session | 4KB | Archives (`progress-archive.md`, `feature_archive.json`) are grep-only — never load whole. ## When to invoke this skill - A session has been going for >2 hours - You notice your replies summarizing already-discussed content (you're losing focus) - About to read a large file (>500 lines) — ask: do I need ALL of it? - About to dispatch a subagent — confirm it returns summary, not log - Context monitor / Claude Code warns about token usage ## Practical moves When budget pressure rises: 1. **Stop and write handoff.** Run `/session-end` if features are in flight. 2. **Hard-truncate reads.** Prefer `head -50`, `grep -A 5`, line range in Read tool — over reading whole files. 3. **Drop tool definitions.** If you have many MCP tools loaded and none are relevant to current work, that's overhead — but you can't control this from inside the session. 4. **Consider context reset.** A fresh session with rich handoff often outperforms continuing a stale one. ## Calibrated estimates You can roughly estimate context use by: - 1 token ≈ 4 chars (English) or 1-2 chars (Chinese) - A 200-line code file ≈ 1500-2500 tokens - A medium SKILL.md ≈ 1000-2000 tokens - Your own multi-paragraph replies ≈ 200-500 tokens each When the user asks "how much room do we have?", be honest about the estimate. ## Looking up context engineering research For specific patterns (e.g., compaction algorithms, attention windowing, RAG indexing strategies) — invoke the `docs-lookup` skill. Pattern names evolve fast in this area; don't rely on memory. Typical entry query: `context engineering 2026` or ` llm`. ## Related - `using-harness-anchor` — Tier 1 injection budget reference - `feature-state-keeper` — what to write to disk - `project-indexing` — TOC as compressed file index ## Source & license This open-source skill is cataloged on AgentStack and links to its original source — we do not rehost the code. - **Author:** [Redtropig](https://github.com/Redtropig) - **Source:** [Redtropig/harness-anchor](https://github.com/Redtropig/harness-anchor) - **License:** MIT Install and usage instructions live in the source repository linked above. ## Pricing - **Free** — Free ## Security capabilities Automated source analysis of v0.1.0 — what this tool can access: - **Network access:** no - **Filesystem access:** no - **Shell / process execution:** no - **Environment & secrets:** no - **Dynamic code execution:** no *"Yes" means the capability is present in the source — more access means more to trust, not that it is unsafe.* ## Versions - **0.1.0** — security scan: passed — Imported from the upstream source. ## Links - Listing page: https://agentstack.voostack.com/l/skill-redtropig-harness-anchor-context-budget-discipline - Seller: https://agentstack.voostack.com/s/redtropig - Browse the marketplace: https://agentstack.voostack.com/browse --- Listed on AgentStack — the marketplace for AI agent skills and MCP servers. Every listing is security-reviewed. Creators keep 70%.