# Harness contract

Contract version: `1.0` (`glas_harness.contract.CONTRACT_VERSION`).

This is the stable boundary between Glas, its consumers, and concrete harness
backends (reins). Glas owns profile resolution and the outer lifecycle; a rein
owns its inner agentic loop. Sand-boxer owns environment provisioning.

## Consumer boundary

`ExecutionRequest` requires an explicit `harness_profile_ref`, repository,
title, and description. It may carry correlation and organizational references
(`assignment_ref`, `role_ref`, `duty_ref`, `goal_refs`, and
`resource_envelope_refs`). Those references link execution evidence to
leadership/workforce records; they do not transfer organizational authority to
Glas.

The gateway returns `GatewayResult` with:

- `ok`, derived from normalized outcome;
- `evidence`, safe for compact State Hub reporting; and
- direct-caller-only `tool_output` and `tool_error`.

Raw prompts, model output, tool output, and credential material are excluded
from the State Hub detail.

## Rein lifecycle

```python
class Rein(ABC):
    def start_session(
        self, profile: HarnessProfile, inputs: dict[str, str], sandbox: SandboxHandle
    ) -> dict[str, Any]: ...

    def dispatch_tool(
        self, session: dict[str, Any], tool_call: ToolCall
    ) -> ToolResult: ...

    def end_session(self, session: dict[str, Any]) -> ExecutionSummary: ...

    def cleanup_session(self, session: dict[str, Any]) -> None: ...
```

```text
Glas                                  rein                 sand-boxer
----                                  ----                 ----------
resolve profile + rein descriptor
create sandbox ------------------------------------------> create
derive workspace + transport from handle
start_session(profile, inputs, handle) -> sandbox-local setup
dispatch_tool(session, call)          -> inner loop across transport
end_session(session)                  -> normalized facts
cleanup_session(session)              -> remove ephemeral task material
destroy sandbox -----------------------------------------> destroy
publish compact ExecutionEvidence
```

After sandbox creation, the caller's source checkout is no longer an execution
path. A same-host descriptor must contain `pid` plus `workspace_dir` and every
rein command is wrapped with `nsenter`; a remote descriptor must contain `ssh`
plus `remote_dir` and every command crosses SSH. Incomplete, mixed, or unknown
reachability refuses at session start. The transport also bounds the outer rein
subprocess with the profile timeout. A host must make the selected rein command
and its dependencies available inside that transport; host-only installation is
not treated as sandbox availability.

There is no production default rein. Direct `Rein` injection remains a narrow
library/test seam but still requires a valid profile so profile, sandbox,
model, tool policy, and evidence are explicit.

## Stability and extension rules

All contract models use Pydantic with unknown fields forbidden. Stable `1.0`
fields are the declared fields in `src/glas_harness/contract.py`. Optional
measurements such as tokens, duration, resolved model, commit, and artifacts
remain `null` when unknown; unsupported tool-event visibility is
`unavailable`, not an empty claim of completeness.

Rein-specific, non-secret additions belong only in declared `metadata` fields.
Adding a required field, changing a field meaning/type, or removing a field
requires a new contract version. Adding an optional field may remain compatible
only when old consumers can safely ignore it and every strict boundary model is
updated together. A profile and rein descriptor must both declare the exact
supported contract version.

Sensitive values are never contract extensions. Profiles may contain
credential-route references, while credential resolution and provider setup
remain rein-local under ADR-002.

## Failure semantics

The gateway returns evidence for every normal refusal/failure path:

- `resolution`: unknown, disabled, ambiguous, incompatible, or unsafe profile;
- `sandbox_create`;
- `session_start`;
- `execution` (including a rein-declared unsuccessful result);
- `session_end`; and
- `teardown`.

Profile resolution happens before sandbox creation. Once a sandbox exists,
rein cleanup and sandbox teardown are attempted on every path. `refused` means
governed execution did not proceed; `failed` means an attempted lifecycle did
not complete successfully.

## Deliberate non-goals

The contract does not schedule work, source blueprints, allocate workers,
resolve leadership, broker credentials, select an unapproved model by price, or
standardize rein internals. Composable rein middleware remains deferred by
ADR-004 until a second concrete need exists.