feat(turn): select the managed Turn host explicitly

docs/integrations/deepseek-harness-connector.md

@@ -131,6 +131,46 @@ continuity or an outer wake/timer. See the adapter README for the home and
 classification precedence, plus the hermetic verification smoke
 (`examples/loopx-turn-dsh-builtin-host-e2e-smoke.py`).
 
+## Host Selection And Managed Executor Readback
+
+The Turn host is **selected, never inferred**. `dsh` is the shipped default
+because it is the managed execution unit the steward drives; `LOOPX_TURN_HOST`
+re-points that default, and an explicit `--host` (or `--host-adapter-command-json`)
+wins over both. A configured `DEEPSEEK_API_KEY` only *authenticates* the selected
+host: discovering a credential never changes where a Turn runs.
+
+Both `loopx turn plan` and `loopx turn run-once` report a `managed_executor`
+block, so a caller reads the planned executor instead of inferring it from a
+host id:
+
+```json
+{
+  "schema_version": "managed_executor_binding_v0",
+  "executor": "dsh",
+  "executor_kind": "managed",
+  "credential_env": "DEEPSEEK_API_KEY",
+  "endpoint_env": "DEEPSEEK_BASE_URL",
+  "operator_credential_bound": true,
+  "available": true,
+  "unavailable_reason": null
+}
+```
+
+`executor_kind` names where the Turn's model work is billed and bounded:
+`managed` for a host bound to an operator credential, `individual` for a host
+that runs on one person's own CLI login, and `generic` for a caller-supplied
+adapter command. `operator_credential_bound` is the narrower claim: it is `true`
+only when the operator credential or an explicit injected runner hook is
+configured. `available` is `false` only when LoopX can prove the planned host
+cannot launch here, and `null` for executors this projection does not probe
+rather than an unproven claim. Only the credential variable *name* is reported;
+the value is never read back.
+
+`run-once --execute` fails closed on that verdict: status `unavailable`, no host
+invocation, no journal write, and no quota spend, with
+`dsh_runtime_unavailable` or `operator_credential_unconfigured` naming the
+missing fact. `plan` reports the same verdict without refusing.
+
 ## Boundaries
 
 - LoopX keeps the durable goal, todo, claim, gate, quota, evidence, and

docs/reference/protocols/loopx-turn-v0.md

@@ -97,6 +97,45 @@ terminal failures reach the Turn Journal. The module/subprocess invocation with
 `--host generic-cli` remains the compatibility and rollback path.
 See [DeepSeek Harness connector](../../integrations/deepseek-harness-connector.md).
 
+### Host Selection
+
+The Turn host is **selected, never inferred**. `loopx turn plan` and
+`loopx turn run-once` default to the managed `dsh` host, the operator may
+re-point that default with `LOOPX_TURN_HOST` or one explicit `--host`, and a
+configured operator credential only *authenticates* the host that was already
+selected. Discovering `DEEPSEEK_API_KEY` must never re-point a Turn by itself.
+
+| surface | value |
+| --- | --- |
+| shipped default host | `dsh` (managed executor) |
+| explicit default selector | `LOOPX_TURN_HOST` |
+| per-command override | `--host codex-cli\|claude-code\|dsh\|generic-cli` (plan), `codex-cli\|dsh\|generic-cli` (run-once) |
+| authenticating credential | `DEEPSEEK_API_KEY`, optional endpoint `DEEPSEEK_BASE_URL` |
+
+This is a default behavior change for the affected lanes: `run-once` moved from
+`generic-cli` to `dsh`, and `plan` from `codex-cli` to `dsh`. `--host
+generic-cli` and `--host codex-cli` remain the explicit compatibility and
+rollback paths, and a machine that wants the former default should set
+`LOOPX_TURN_HOST=generic-cli` (or `codex-cli`) once instead of relying on the
+ambient environment.
+
+`plan` and `run-once` payloads carry the executor readback `managed_executor`
+(`managed_executor_binding_v0`): the executor and its kind (`managed`,
+`individual`, `generic`), the credential env var *name* (never its value), the
+endpoint env var name, whether the executor is operator-credential-bound, and
+whether it can launch here. When it cannot, `available` is `false` and
+`unavailable_reason` names the missing fact:
+
+| `unavailable_reason` | meaning | remediation |
+| --- | --- | --- |
+| `dsh_runtime_unavailable` | the DeepSeek Harness runtime is not importable and no explicit runner hook was supplied | install the released runtime, pass its runner hook, or select `--host codex-cli` |
+| `operator_credential_unconfigured` | the managed host is selected but no operator credential or runner hook would authenticate it | set `DEEPSEEK_API_KEY`, or select `--host codex-cli` explicitly |
+
+`run-once --execute` fails closed on that verdict: status `unavailable`, no host
+invocation, no Journal write, and no quota slot spend. An explicitly selected
+individual host (`--host codex-cli`, `--host claude-code`) is billed to that
+individual CLI login and makes no launchability claim (`available: null`).
+
 ### Five Questions For Any Agent CLI
 
 Before wiring Trae CLI, Codex CLI, or another host, answer these five questions:

examples/control_plane/cli-output-probe-runner.py

@@ -108,6 +108,9 @@ def _receipt_row(
         "reward_memory_outcome_prompt_revision": (
             semantics.reward_memory_outcome_prompt_revision(text)
         ),
+        "managed_executor_binding_revision": (
+            semantics.managed_executor_binding_revision(text)
+        ),
         "guided_todo_delta_schema_versions": (
             semantics.guided_todo_delta_schema_versions(payload)
             if isinstance(payload, dict)