hermes-webui/docs/rfcs/webui-run-state-consistency-contract.md

WebUI Run State Consistency Contract

• Status: Proposed
• Author: @franksong2702
• Created: 2026-05-16
• Tracking issue: #2361
• Related architecture: #1925, hermes-run-adapter-contract.md

Problem

A single WebUI agent turn is represented by several overlapping state layers:

• the visible transcript the user can read,
• the model context / context_messages the agent actually receives,
• pending_user_message and active stream metadata,
• live SSE events and in-memory stream state,
• durable run journal / replay state,
• automatic compression summaries and active-task handoff text,
• the browser's live timeline DOM/cache,
• sidebar ordering, unread state, and updated_at metadata.

Those layers are not independent. When they drift apart, the user sees failures that look unrelated: a prompt is visible but missing from recovered model context, a live run loses or reorders thinking/tool cards after switching sessions, cleanup makes old sessions look newly active, replay duplicates content, or automatic compression reference material appears inside the active turn.

This RFC defines a consistency contract for those layers. It complements the larger run adapter direction in #1925 by documenting what must remain coherent while WebUI still has multiple overlapping state stores.

Goals

• Define the state layers involved in active and recovered WebUI turns.
• Make the source-of-truth expectations explicit for each layer.
• Give reviewers a checklist for streaming, replay, compression, recovery, model-context, and sidebar changes.
• Map recent real issues to reusable invariants so future fixes do not solve the same class of bug one symptom at a time.

Non-goals

• Do not implement a runner process, sidecar, or new runtime boundary here.
• Do not replace #1925 or the run adapter contract.
• Do not rewrite the streaming protocol in this RFC.
• Do not reopen already-fixed narrow bugs.
• Do not make this a catch-all for unrelated UI polish.

State Layers

Layer	Purpose	Source-of-truth expectation	Must not do
Visible transcript	Shows what the user and assistant said	Session transcript plus live replay should produce one chronological user-visible story	Hide the user turn that started active work, or show internal recovery text as current user intent
Model context / context_messages	Supplies conversation state to the agent	Must include the current visible user turn unless deliberately excluded with a user-visible reason	Let the agent resume from context that contradicts what the user can see
Pending turn metadata	Bridges submitted-but-not-yet-finalized user input	Must identify the user turn and stream that own active work	Become a permanent duplicate transcript row after recovery
Live stream / SSE	Delivers active runtime events to the browser	Must remain an observation path, not the only durable truth for already-emitted events	Lose the visible scene on refresh, reconnect, or session switch
Run journal / replay	Rebuilds emitted runtime events after reconnect or restart	Must be cursor-safe and idempotent	Duplicate assistant text, thinking text, tool cards, or compression cards
Compression summary / handoff	Gives the agent recovery context after automatic compression	Must remain agent-facing recovery material unless explicitly rendered as history	Pollute the active turn or become implicit current user intent
Live UI scene/cache	Preserves expanded rows, in-progress cards, local scroll, and transient grouping	May optimize presentation but must be rebuildable or degradable from transcript/replay	Become the only place where chronological ordering exists
Sidebar/session metadata	Helps the user find active and recent sessions	Must reflect meaningful user or assistant activity	Treat background cleanup as a fresh user-facing update

Core Invariants

1. Visible current turns enter model context. If the user can see a current prompt and WebUI asks the model to continue that work, the prompt must be in the reconstructed model context unless WebUI shows an explicit reason it was excluded.
2. Active turn UI keeps its owner. The user turn that started active work must remain visible before assistant text, thinking cards, tool cards, or activity groups that belong to that work.
3. Reattach preserves order or degrades clearly. Refresh, reconnect, and session switch must preserve chronological live-scene order. If WebUI cannot restore the exact live scene, it should downgrade to an explicit structured replay state instead of silently reordering content.
4. Maintenance is not activity. Runtime maintenance such as stale-stream cleanup, orphan repair, or background compression must not refresh sidebar ordering, unread markers, or active-session affordances as if the user or assistant just acted.
5. Replay is idempotent. Replaying a run from a cursor must not duplicate transcript rows, thinking content, interim assistant text, tool cards, or compression cards.
6. Compression is not current intent. Automatic compression summaries and reference cards are recovery/handoff material. They must not be treated as a new user request, active-turn content, or the default visible explanation for the current answer.
7. Observation has a degraded path. Long-running or many-session observation should expose enough heartbeat/degraded status that the UI does not appear silent and ordinary APIs do not stall behind active streams.
8. Every mutation names its layer. A PR touching streaming, recovery, context reconstruction, compression, replay, or sidebar metadata should state which layer it changes and what regression proves the invariant still holds.

Review Checklist

Use this checklist for PRs that touch run state, streaming, replay, compression, context reconstruction, or session metadata:

• Which state layers does this PR read or write?
• Which layer is the source of truth after this change?
• Can the visible transcript and model context diverge? If yes, is that deliberate and user-visible?
• What happens after browser refresh, session switch, SSE reconnect, and WebUI restart?
• Does replay rebuild the same scene without duplicates?
• Can this change move a session in the sidebar without meaningful user or assistant activity?
• Can automatic compression or recovery text become visible active-turn content?
• What test or manual evidence proves the invariant?

Existing Issue Map

Example	State boundary exposed	Relevant invariant
#2341 / #2342	Active reattach could show agent activity without the pending user turn that started it	2
#2344 / #2347	Session switching could lose or reorder the live thinking/tool/interim timeline	3, 5
#2345 / #2349	Stale stream cleanup could mutate updated_at and resurface old sessions	4
#2346 / #2348	Thinking cards could repeat interim assistant progress text	5
#2353 / #2354	Recovered pending user turns could be visible but missing from model context	1
#2355 / #2357	Auto-compression rotation could leave reference-only cards in the active conversation tail	3, 6
#2308 / #2309	Compressed sessions could resume stale agent tasks when the user starts an ordinary fresh chat	6
#2283	Run event journal replay provides the foundation for ordered recovery	5

These references are evidence for the contract. This RFC does not make the linked implementation PRs dependent on this document, and it does not close the tracking issue by itself.

Relationship To The Run Adapter RFC

The run adapter RFC defines the longer-term event/control boundary for WebUI and Hermes runtime ownership. This RFC defines the consistency rules that the current WebUI and any future adapter-backed implementation must preserve.

The two documents should be read together:

• The adapter contract answers: "Where should execution ownership live?"
• This consistency contract answers: "How do transcript, context, streams, replay, compression, and UI metadata stay coherent while execution is active or being recovered?"

Rollout Plan

1. Land this RFC as a reviewable draft and refine it through PR discussion.
2. Link future streaming/recovery/compression/sidebar PRs back to the invariant they intentionally preserve or change.
3. Convert recurring checklist items into focused regression tests where practical.
4. If #1925 introduces a new adapter-backed runtime layer, update this RFC or replace it with the accepted implementation contract so these invariants do not live only in historical discussion.