plat 348

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PLAT-348 — Retained completed sessions fan out workflow-open restoration

Field	Value
Status	implemented locally; deployment and live acceptance pending
Priority	P0 production navigation latency
Owner	frontend workflow reconnect / active-session projection
Reported	2026-09-21
Related	PLAT-109, PLAT-343, PLAT-341

Incident

RTS workflow switches displayed Loading conversation… and Loading dashboard… for minutes. During the wait, Chat could briefly render the new-chat guide even though the destination workflow already had durable history. Both panes eventually loaded without a server restart.

Live endpoint timing ruled out backend storage latency. For Workflow/rtssprinttracking and Workflow/rtsprreviweer, chat history, dashboard HTML, Pulse, playbooks and active-session reads completed in 1–55 ms. The active-session response was the outlier in semantics rather than duration: it returned 45 retained sessions, all with terminal completed status. Forty- three were workflow sessions and 42 belonged to rtsprreviweer.

Root cause

The backend intentionally retains terminal coding sessions for 24 hours so a follow-up message can reuse the provider terminal and conversation identity. The workflow-open frontend still treated every row returned by /api/sessions/active as live work. It therefore:

1. performed per-session running-workflow resolution across retained completed turns;
2. allowed previously persisted tabs to enter transcript rehydration; and
3. marked a hydrated tab streaming merely because its retained session ID was present in the response.

On a mature workflow this multiplied one navigation into dozens of lookups and restores. While that asynchronous chain ran, selection was cleared before the durable chat was resolved, so the UI could show a false empty-chat state. The dashboard request itself was fast but competed with the unnecessary navigation fan-out in the same client.

Fix

• Filter the retained runtime index through the canonical live-activity rule before any workflow reconnect lookup or hydration.
• Apply the same live rule before setting a hydrated tab back to streaming.
• Key conversation-resolution state by workflow identity. During a switch, mask the old/empty chat surface with an explicit loading state until the current workflow's durable chat selection settles.
• Keep 24-hour backend retention unchanged; continuity handles and live work remain separate concepts.

Regression coverage

• A 42-session retained-completed fixture produces zero reconnect candidates.
• An authoritative running workflow remains eligible even when its legacy row says completed.
• Non-workflow sessions cannot enter workflow reconnect.
• Focused Vitest suites pass (15 tests), TypeScript project build passes, and git diff --check is clean.

Acceptance

1. Switching among mature workflows does not issue per-completed-turn runtime lookups or transcript restores.
2. Existing durable Chat appears without a false new-chat guide.
3. Dashboard/Pulse loading is independent of retained terminal count.
4. A genuinely live workflow still reconnects and streams normally.
5. RTS interactive switching is verified after deployment.