Devin Sessions And Planning

Operator creates a Devin session via POST /v1/sessions passing snapshot_id from a prior session to resume on the same VM state.

Pass snapshot_id only when the prior session was NOT terminated — terminate is irreversible and invalidates the snapshot. On 4xx referencing an invalid snapshot, surface to operator with a 'create fresh session' fallback, do not loop the retry. Record the new session_id and persist the snapshot lin…

Operator inspects a long-running Devin session and expects to see Devin's plan BEFORE execution begins so they can intervene on misinterpretation.

Surface the structured plan (milestone list with dependencies) in the session UI / API before file mutations or terminal commands run. Pause-at-plan-confirm is opt-in per playbook; default is execute-after-plan with the plan visible. Do not collapse plan and execute into one opaque step.

Operator sends a follow-up instruction to an active session via POST /v1/sessions/{id}/message ('also add a unit test for the new branch').

Follow-up message appends to the same session — Devin folds the new instruction into the existing plan and amends milestones rather than restarting. Confirm session_id is still in a non-terminal state before sending. On 404 / terminated, prompt operator to create a new session with snapshot_id.