[REA-6854] Close a session when it reaches its steps

[Dere-Wah]

Why

A session started with steps is meant to run that many steps and end, and there may be no client there to stop it. With step reports in place, the runtime can close the session itself.

What Changed

The step that brings a running session to its steps stops it with a normal stop: reason stopped and the close reason "Session ended: the requested steps are complete.", which connected clients are told before their connections close. The model keeps stepping until the session end reaches it, so a step reported after the stop is journalled with its number and stops nothing. A session without steps never stops on its own.

A step report carries the session it began in, as the model's count of session starts, and the runner keeps the same count of the starts it posts. A report from an earlier session, one that a model finishes after a quick stop and restart, is dropped: it is neither journalled nor counted, so it cannot close the session that followed.

The contract suite now runs the whole flow on a model with no client connected, with the orphan timeout set short so a client-less timeout would show up if it fired:

start_session       ready -> waiting
connection_opened   {"conn_id": 0, "system": true}
command             {"name": "set_speed", "args": {"speed": 2.0}, "conn_id": 0}
step_completed      {"step": 1, "saved": false, "error": null}
step_completed      {"step": 2, "saved": false, "error": null}
stop_session        {"reason": "stopped", "close_reason": "Session ended: the requested steps are complete."}
cleanup_complete    closing -> ready

A second contract test starts a session with steps: 2 whose starting input names an image the caller uploads 200 ms after the start. The journal shows the starting command before the first step_completed, so a session cannot reach its steps before its setup arrives.

The same flow against examples/starter with steps: 5 and no client ran five steps, stopped, and returned to ready; one more step was reported before the session end reached the model, and it was journalled without effect.

[github-actions]

[codex-review] - [P1] src/reactor_runtime/runner/runner.py: A late completion from the prior session can incorrectly count toward and stop the next session.

Scope: full (9af1f4c..dcb5538).

View workflow run.

[Dere-Wah]

• [REA-6855] Serve saved step folders over HTTP #239
• [REA-6855] Save each reported step as a folder of files #238
• [REA-6855] Write one step's output as a single MP4 file #237
• [REA-6855] Read the runtime.step_results block from the manifest #236
• [REA-6854] Close a session when it reaches its steps #235 👈 (View in Graphite)
• [REA-6854] Report each finished step to the runtime with complete_step() #234
• [REA-6854] Apply a session's starting input, sent by a system client #233
• [REA-6854] Read starting_input and steps from the start body #232
• [REA-6854] Deliver commands and reactor events to the model in posted order #231
• main

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[tempusfrangit]

Reviewed completion counting, stop notifications, and default-loop session stamping. The regression coverage verifies that an earlier session's report cannot stop a later session.

[Dere-Wah]

Merge activity

• Oct 5, 6:07 PM UTC: A user started a stack merge that includes this pull request via Graphite.
• Oct 5, 6:21 PM UTC: Graphite rebased this pull request as part of a merge.
• Oct 5, 6:22 PM UTC: @Dere-Wah merged this pull request with Graphite.