[cikowski]

Adds src/agent_env/providers/sandbox_providers/AGENTS.md, a guide for coding agents and contributors on writing a sandbox provider, next to the code it covers (same layout as #279 for A2A agents).

It covers the provider and sandbox contracts, the declarations (SANDBOX_ACCEPTS, CONTAINER_ACCEPTS, ...), lifecycle, network policy hooks, registration (entry point or built-in), tests and a checklist. Written against current main: nothing on SandboxProvider is abstract, terminate_sandbox and prepare_image exist, and boxd, tensorlake, vercel and tenki are the reference backends beside e2b. Root AGENTS.md links to both guides.

Docs only; no code, no website content changed.

Co-Authored-By: Claude Sonnet 5.5 noreply@anthropic.com

🤖 Generated with Claude Code

Rollout

Docs only, no code path changes. Nothing to deploy, no order, no migration. Revert: revert the commits; nothing depends on the file. After merge: the website docs are unchanged, so a maintainer decides whether the sandbox provider page should mirror it.

Validation

Head 30713b4. Observed: every class, method, class variable and helper the guide names was checked by reading and grepping current main (sandbox_provider.py, sandbox.py, boxd/provider.py, tst/util/capabilities.py); the two Greptile findings were checked the same way and fixed. Observed: CI green (unit, integration-local, integration-local-slow, integration-local-gateway, clean-install, plugin-api, ui). Not run: a new provider built by following the guide end to end (agent-env plugin check, agent-env run hello --sandbox <name>); the guide's workflow steps are unexercised.

Confidence Score: 5/5

This documentation-only PR appears safe to merge.

Summary

Adds a sandbox provider guide beside the provider code and links it from the root AGENTS.md.

• Contributors can follow a guide to build sandbox providers.

_{Reviews (3) · Last reviewed commit: "address review round 2: correct the buil..." · Reviewed by Greptile}