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Version: 0.2.15

X07 (x07lang)

X07 is the deterministic, certifiable execution substrate for agent-written software. As code generation gets cheap, trust becomes the bottleneck — so X07 makes generated code runnable: deterministic solve worlds with record/replay, explicit resource budgets, capability sandboxing, structured diagnostics with quickfix coverage, spec-first testing (XTAL), and proof-backed certification. It compiles via C to fast native binaries, with a WASM target for portable sandboxed execution.

Most languages optimize for human style flexibility. X07 optimizes for:

  • Canonical representations so the same intent produces the same program shape.
  • Machine-readable diagnostics with stable error codes, did-you-mean suggestions, and machine-applicable fixes.
  • World-based capability modeling so side effects stay explicit and reviewable.
  • Evidence over review-by-reading: budgets, replayable runs, trust reports, and certificates.

The mental model​

Think of X07 as two layers:

  1. A small, stable core (compiler + runtime substrate)
  2. A growing ecosystem of libraries (stdlib + external packages)

Programs are stored and exchanged in a structured AST format (x07AST JSON). Agents and humans can operate on the structured form directly, or read and author through x07text — a lossless text projection (x07 ast to-text / from-text) that always converts back to canonical JSON.

Direct authoring by agents is a supported surface and an explicitly gated bet: a comparative eval (labs/agent-eval/ in the toolchain repo) with a predeclared decision rule determines whether deeper language-surface investment proceeds. See Why X07 for the honest status.

Start here​

If you are a human evaluating X07​

If you are driving through an agent​

Ecosystem at a glance (2026-06 scope)​

The x07 repo is the entrypoint. The active ecosystem was deliberately narrowed in 2026-06 to concentrate on the substrate bet (see the roadmap):

  • Core toolchain: x07 — language, CLI, compiler, stdlib, verification/certification tooling, and the canonical docs source.
  • MCP kit + official MCP server: x07-mcp gives you templates for building MCP servers in X07 and ships the official io.x07/x07lang-mcp server for agent runtimes. Start with MCP kit.
  • WASM: x07-wasm-backend covers WASM modules and WASI components for portable sandboxed execution. Start with WASM tooling.
  • Packages and docs: x07-registry powers package publishing at x07.io, and x07-website serves x07lang.org.
  • MCP server verification: hardproof is the standalone verifier CLI used by the MCP quality flow.

Former ecosystem surfaces — studio/IDE shells, web UI contracts, device hosts, and the lifecycle platform (x07-studio, x07-forge, x07-crewops, x07-tactics, x07-device-host, x07-web-ui, x07-sentinel-reference-stack, x07-platform + contracts/cloud) — were archived in the 2026-06 scope cut (read-only on GitHub). See the roadmap for the rationale and reactivation conditions.

What makes X07 different?​

1) One canonical way (agents don’t get “choice paralysis”)​

Instead of 5 equivalent ways to read a file, split strings, build output, or handle errors, X07 aims for:

  • one canonical API surface per capability,
  • one canonical bytes encoding per data interchange,
  • one canonical failure model per module (stable error code space).

This reduces “LLM confusion” and makes programs and patches more uniform.

2) Policy-gated OS execution​

When you need real OS resources (real network, real disk, real time), use run-os or run-os-sandboxed.

run-os-sandboxed is governed by explicit policy files; X07 defaults to a VM boundary on supported platforms, but it is still not a hardened sandbox if you mount secrets or enable networking.

3) Production worlds are opt-in​

When you need real OS resources (real network, real disk, real time), you switch to OS-backed worlds. Those worlds are never used for deterministic evaluation, and are governed by explicit policies.

Why this matters in practice​

  • For teams running agent-generated code: deterministic runs, budgets, sandbox policies, and certificates turn “should we run this?” from a judgment call into a checkable artifact.
  • For end users: one language and one ecosystem for CLIs, MCP servers, WASM services, and package publishing.
  • For coding agents: the language removes many of the ambiguities that make autonomous edits hard to trust in mainstream languages.

Documentation map (human)​