Rust SDK

The Rust crate is ctxmesh. It is a plane client — every launcher route reachable with typed clients and a typed Error — over the localhost plane the platform serves beside your agent.

It holds no credentials. Endpoints and identity arrive in the environment the launcher injects.

Install

cargo add ctxmesh

cargo add selects the current pre-release while no stable exists. See Compatibility for the version.

Constructing a client

use ctxmesh::{Client, Entry};

let cx = Client::from_env()?;     // reads MEMORY_PORT, CONVERSATION_ID, DELEGATE_PORT, …

from_env returns Result, so a binary run outside a pod reports why rather than panicking. Client::with_config takes an explicit config for tests.

Memory, knowledge, skills

cx.memory_append(&Entry { role: "user".into(), content: "what changed?".into() }, None)?;
let history = cx.memory_get(None)?;
let hits = cx.memory_search("deploy", None, Some(capability))?;

cx.remember("prefers terse answers", None)?;          // long-term
let facts = cx.search_agent("contact preference", 5, 0.0)?;

let chunks = cx.knowledge_search("rollback procedure", Some("runbooks"), 5)?;

let skills = cx.skills()?;
let body = cx.skill_load("deploy")?;

Feedback and agent-to-agent

cx.feedback(&trace_id, "helpfulness", 1.0, Some("clear"))?;
let reply = cx.call_agent("billing-agent", serde_json::json!({"q": "invoice 42"}))?;

Delegation and handoff

let d = cx.delegate("research-agent", "step-1", "call-1", capability,
                    serde_json::json!({"topic": "pricing"}))?;
let h = cx.handoff("escalation-agent", capability, Some("over to you"), true)?;

Both reach the delegate listener (DELEGATE_PORT, default 2994), not the memory port. step and call_id are the idempotency key and are required — the crate refuses locally if either is empty.

Errors

Error distinguishes a transport failure from Error::Invalid (a required argument missing) and from a route the platform has not wired for this agent, so a configuration gap does not present as a network problem.

What this tier does not include

The managed agent loop, tool dispatch, the model-gateway client, serve, prompt spotlighting and record/replay are authoring tier and live in the Python and TypeScript SDKs only (ADR 0139). You write your own loop and call the model gateway over plain HTTP at $MODEL_GATEWAY_URL.

That is not a gap so much as the tier’s premise: every capability here is a localhost HTTP endpoint, so this package is convenience, never a requirement. An agent in any language is fully governed and traced without it.

The run capability

delegate, handoff, per-user session memory and per-user knowledge each need the caller’s run capability — the X-Ctxmesh-Run-Capability header. It is an explicit per-call parameter rather than client state, because a capability is minted for one run and a field on a long-lived client would outlive it.

Where the route requires it, the SDK refuses locally with a typed error instead of sending a request the launcher will reject. Session memory is the one that fails quietly: omit the capability there and the launcher falls back to the agent-wide bucket with no error, so the parameter is visible on every memory call for exactly that reason.