{"slug": "benchmarking-affaan-m-ecc-in-cursor-agent-harness-rules-without-context", "title": "Benchmarking affaan-m/ECC in Cursor: Agent Harness Rules Without Context Exhaustion", "summary": "A developer documented a modular setup for running the affaan-m/ECC agent harness inside Cursor, symlinking only common and TypeScript rules into .cursor/rules/ and registering ECC's MCP servers via .cursor/mcp.json to avoid context bloat. The writeup claims that routing Cursor through B-Lost's proxy endpoint, which offers gateway-level prompt caching, cut heavy multi-turn context costs by roughly 80-90% without losing chat history or degrading reasoning fidelity.", "body_md": "When evaluating **affaan-m/ECC** (v2.0, *The Agent Harness Operating System*), the main attraction is standardization. Instead of manually copying fragmented `.cursorrules`, skill prompts, and MCP configurations between Claude Code, Codex, and Cursor, ECC packages skills, instincts, and execution policies into a unified harness.\n\nHowever, bringing an enterprise-grade agent harness into Cursor introduces a familiar bottleneck: **context bloat**. Stacking dense instinct files, language-specific rules, and MCP tool schemas into your agent's system prompt burns tokens rapidly. In deep multi-turn refactoring loops, this degrades model reasoning and inflates per-turn API latency.\n\nHere is how we set up ECC modularly inside Cursor and stabilized multi-turn session costs.\n\nAvoid dumping all ECC skills into Cursor's root prompt. Instead, install the repository and link only the target language rules into `.cursor/rules/`:\n\n```\n# Clone the ECC repository\ngit clone https://github.com/affaan-m/ECC.git ~/.config/ecc\n\n# Target workspace configuration: symlink common + TypeScript rules only\nmkdir -p .cursor/rules\ncp ~/.config/ecc/rules/common/*.mdc .cursor/rules/\ncp ~/.config/ecc/rules/typescript/*.mdc .cursor/rules/\n```\n\nThis keeps your baseline context lightweight, injecting language rules only when matching files are active.\n\nECC defines modular MCP servers for test runners and filesystem inspections. Add them to your project's `.cursor/mcp.json`:\n\n```\n{\n  \"mcpServers\": {\n    \"ecc-harness\": {\n      \"command\": \"npx\",\n      \"args\": [\"-y\", \"@ecc/harness-mcp@latest\"]\n    }\n  }\n}\n```\n\nEvery time Cursor executes an agentic cycle (read file → invoke MCP → patch code), it resends the entire conversation history along with ECC's static rules. On vanilla endpoints, you pay full token rates on every re-evaluation.\n\nIn our tests, switching Cursor to B-Lost's fast proxy endpoint resolved this bottleneck. Because B-Lost provides native prompt caching at the gateway layer, static harness rules and accumulated turn history are cached automatically. This cut heavy multi-turn context costs by ~80-90% without losing chat history or degrading reasoning fidelity.\n\n```\n// ~/.cursor/settings.json (Custom Model Override)\n{\n  \"cursor.customModel.override\": true,\n  \"cursor.customModel.baseUrl\": \"https://api.b-lost.com/v1\",\n  \"cursor.customModel.model\": \"claude-3-7-sonnet-20250219\"\n}\n```\n\naffaan-m/ECC provides a disciplined framework for managing agent instincts. The key to running it inside Cursor without slowdowns is modular rule scoping combined with gateway-level prompt caching.", "url": "https://wpnews.pro/news/benchmarking-affaan-m-ecc-in-cursor-agent-harness-rules-without-context", "canonical_source": "https://dev.to/sloves/benchmarking-affaan-mecc-in-cursor-agent-harness-rules-without-context-exhaustion-4k6k", "published_at": "2026-09-16 21:11:12+00:00", "updated_at": "2026-09-16 21:23:19.312521+00:00", "lang": "en", "topics": ["ai-agents", "agent-protocols", "developer-tools", "ai-tools"], "entities": ["affaan-m/ECC", "Cursor", "B-Lost", "Claude Code", "Codex", "Anthropic"], "alternates": {"html": "https://wpnews.pro/news/benchmarking-affaan-m-ecc-in-cursor-agent-harness-rules-without-context", "markdown": "https://wpnews.pro/news/benchmarking-affaan-m-ecc-in-cursor-agent-harness-rules-without-context.md", "text": "https://wpnews.pro/news/benchmarking-affaan-m-ecc-in-cursor-agent-harness-rules-without-context.txt", "jsonld": "https://wpnews.pro/news/benchmarking-affaan-m-ecc-in-cursor-agent-harness-rules-without-context.jsonld"}}