Ctxfw – In-memory Tree-sitter AST compactor that cuts coding tokens by 72% CTXFW, an open-core context firewall and Model Context Protocol gatekeeper from HeuristicoLab, compacts peripheral code in coding-agent context windows by 72.4% by replacing distance-1 and distance-2+ module implementations with interface signatures, type definitions, and functional stubs. The tool reports a 59.5% net context reduction in an internal benchmark against 16 dependencies, cutting 49,096 tokens to 20,014 tokens and eliminating 29,222 tokens, with AST compaction latency of 1,407.96 ms and engine compaction overhead under 5.0 ms. CTXFW installs via pip or pipx and registers as a stdio MCP server in clients including Claude Desktop, Cursor, Windsurf, and Antigravity, and is listed with Grade A compliance on the Glama MCP registry. The deterministic boundary between probabilistic LLM hallucination and production infrastructure. Installation installation • Benchmarks ast-pruning-benchmarks • Diagnostic system-diagnostics • Architecture architecture • Enterprise Governance enterprise-governance Autonomous coding agents Claude, Gemini, Cursor, Antigravity consume massive context windows with bloated peripheral dependencies, triggering token exhaustion, context drift, and security degradation. CTXFW is an open-core context firewall and Model Context Protocol MCP gatekeeper. It combines an in-memory polyglot AST pruner with a deterministic axiomatic intake sieve : 1. Compacts Peripheral Code 72.4% token reduction : Replaces distance-1 and distance-2+ module implementations with clean interface signatures, type definitions, and functional stubs. 2. Enforces Axiomatic Integrity ACI : Rejects ungrounded or deficient architecture briefs missing negative invariants $\ge$ 0.9000 $N \ge 5$ , bounded variable domains, deterministic state machines, or formal error taxonomies. 3. Zero Telemetry Egress : Guaranteed local execution with zero network telemetry leakage on standard operating mode. CTXFW operates directly at the syntax tree layer using native polyglot grammars: | Benchmark Dimension | Raw Context Ingestion | CTXFW Topological Compactor | Performance Gain / Impact | |---|---|---|---| | Token Consumption | 100% Raw Files | 27.6% Interface Stubs | 72.4% Bloat Eliminated | | Engine Compaction Overhead | — | Native in-memory parser | < 5.0 ms | | Warm Cache Hit Overhead | — | SQLite WAL semantic cache | < 0.8 ms | | Stdio Telemetry Egress | Unsanitized stdout | Pure isolated JSON-RPC | Zero Egress 100% Isolated | | Axiom Verification Latency | — | Sieve evaluation | < 12.0 ms | | CI/CD Pre-Commit Latency | — | Headless git sentry | < 85.0 ms | Empirical context reduction metrics generated via ctxfw.resolve context bundle running against 16 internal dependencies: | Dimension | Raw Context Ingestion | CTXFW Topological Sieve | Performance Delta | |---|---|---|---| | Total Context Size | 49,096 tokens | 20,014 tokens | -59.5% Net Reduction | | Tokens Eliminated | 0 tokens | 29,222 tokens | 29,222 bloat tokens pruned | | Transitive Deps | 7,275 tokens | 4,763 tokens | Up to 91.9% reduction | | FinOps Cost Impact | Base Cost | Reduced by $0.0877 USD / prompt | ~$87.70 USD saved per 1K calls | | AST Compaction Latency | — | 1,407.96 ms | In-memory Tree-Sitter parsing | | Attestation Integrity | None | SHA-256 sealed | Strict interface preservation | Topological Hierarchy Breakdown: - ctxfw/cli.py : 100% Full Implementation preserved.$D 0$ Target - gatekeeper.py , mcp.py : Implementation truncated to typed stubs $D 1$ Direct Deps e.g. ... . Token savings: 73% – 86% . - polyglot.py : Nominal symbols only. Token savings:$D {2+}$ Transitive Deps e.g. 91.9% . Install via pip or isolated environment manager: pip install ctxfw Or for global CLI availability using pipx : pipx install ctxfw Register the stdio server directly in your IDE or client configuration claude desktop config.json , Cursor, Windsurf, or Antigravity : { "mcpServers": { "ctxfw": { "command": "ctxfw", "args": "mcp" } } } CTXFW is indexed and verified with Grade A compliance on the official Glama MCP registry: Direct access to tool inspection, schemas, and live diagnostic telemetry on Glama https://glama.ai/mcp/servers/heuristicolab/ctxfw . Validate local environment readiness, stdio isolation purity, SQLite WAL concurrency, and Tree-Sitter grammars with a single command: ctxfw doctor ======================================================================== CTXFW DOCTOR // HIGH-ASSURANCE HEALTH & ISOLATION DIAGNOSTIC ======================================================================== PASS Python Package & sys.path ctxfw v3.5.0 loaded cleanly. PASS MCP stdio Stream Isolation 100% pure JSON-RPC on stdout. Diagnostic logs isolated to stderr. PASS Global CLI Executable PATH Binary 'ctxfw' found in PATH. PASS Axiomatic Sieve Engine Evaluation verified ACI: 1.0000, Invariants: 5 . PASS SQLite WAL Cache & Concurrency Journal mode: WAL, Busy timeout: 5000ms. PASS Polyglot Tree-Sitter Grammars Initialized language parsers typescript, go, java . ------------------------------------------------------------------------ Overall Verdict: HEALTHY ATTESTED Perimeter defense operational. ======================================================================== CTXFW // 72.4% AST Bloat Eliminated. Zero Telemetry Egress. Need team-wide budget circuit breakers or multi-node proxy governance? Control Plane & Enterprise Licensing: https://ctxfw.heuristicolab.com ======================================================================== CTXFW enforces a strict deterministic perimeter dividing probabilistic agent code from the core codebase: PROBABILISTIC DOMAIN DETERMINISTIC PERIMETER ┌───────────────────────┐ ┌────────────────────────────────────────┐ │ Autonomous AI Agent │ │ CTXFW ENGINE │ │ Claude / Gemini / │ │ │ │ Cursor / Antigravity│ │ ┌──────────────────────────────────┐ │ └───────────┬───────────┘ │ │ Polyglot AST Topological Engine│ │ │ │ │ - Python ast │ │ │ Target Context / Brief │ │ - TypeScript / Go / Java CST │ │ ▼ │ │ - Multi-Depth Interface Stubs │ │ ┌───────────────────────┐ │ └────────────────┬─────────────────┘ │ │ MCP Stdio Interceptor ├─────────────────►│ │ │ └───────────────────────┘ │ ┌────────────────┴─────────────────┐ │ │ │ SQLite WAL High-Concurrency │ │ │ │ Semantic Cache <5ms warm hit │ │ │ └────────────────┬─────────────────┘ │ │ ▼ │ │ ACI = 0.9000? │ │ / \ │ │ YES NO │ │ │ │ │ │ ▼ ▼ │ │ ┌──────────────┐ ┌─────────────────┐ │ │ │ VERIFIED │ │ QUARANTINED │ │ │ │ SHA-256 Seal │ │ Execution Halt │ │ │ └──────┬───────┘ └────────┬────────┘ │ └────────┼────────────────────┼──────────┘ │ │ ▼ ▼ Code Generation Forensic Report & Git Permitted Pre-Commit Abort 1. Polyglot Tree-Sitter Pruner : - Compiles topological dependency trees. Distance 0 target file is preserved in full; Distance 1 dependencies retain signatures and docstrings while pruning implementation logic; Distance 2+ dependencies are reduced to compact type stubs. - Built-in support for Python , TypeScript/JavaScript , Go , and Java . 2. SQLite WAL High-Concurrency Semantic Cache : - Atomic multi-process caching configured with Write-Ahead Logging PRAGMA journal mode=WAL and busy timeout=5000ms , delivering sub-millisecond warm cache hits. 3. Atomic multi-process caching configured with Write-Ahead Logging 4. Axiomatic Sieve Engine : - Formal specification gatekeeper evaluating requirements against 5 negative invariants shall never , explicit mathematical bounds, deterministic state machines, and a 4-class error taxonomy. 5. Formal specification gatekeeper evaluating requirements against 5 negative invariants Inject perimeter rules, MCP server declarations, and pre-commit sentinels into your workspace: ctxfw init --global Automatically configures Google Antigravity, Cursor, and Claude Desktop. ctxfw init --repo . Deploys .git/hooks/pre-commit to prevent uncertified code commits lacking an attested specification brief. For distributed engineering teams requiring centralized policy controls: - Team-wide LLM budget circuit breakers : Hard token and dollar thresholds with automatic killswitches. - Multi-node reverse proxy governance : Centralized firewall gateways supporting OpenAI and Anthropic streaming SSE endpoints. - FinOps Telemetry Ledger : Aggregate tokens saved, cost elusion analytics, and tamper-evident audit trails. Control Plane & Enterprise Licensing: https://ctxfw.heuristicolab.com https://ctxfw.heuristicolab.com