PR #58641: Webchat: preserve rewritten stream snapshots

• Repository: openclaw/openclaw
• Author: neeravmakwana
• State: open | merged: False
• Link: https://github.com/openclaw/openclaw/pull/58641

Description (problem / solution / changelog)

Summary

Fix the webchat streaming path so assistant text revisions are treated as replacement snapshots instead of being silently dropped. This keeps rewritten structured replies, including table-like output, visible during streaming and after history refresh.

Repro Steps

1. Use a model that rewrites earlier characters while producing structured output.
2. Request a response with table-like or aligned multiline text.
3. Observe that the streaming path can rewind from an earlier snapshot to a shorter corrected one.
4. Before this change, the agent stream suppressed that correction and the webchat controller also rejected shorter replacement snapshots.

Root Cause

The assistant streaming pipeline assumed visible text only ever grew monotonically.

• src/agents/pi-embedded-subscribe.handlers.messages.ts dropped updates when cleaned text no longer started with the previous cleaned snapshot.
• ui/src/ui/controllers/chat.ts ignored chat deltas when the next visible snapshot was shorter than the current one.
• src/gateway/openresponses-http.ts also needed to keep its accumulated text in sync when replacement snapshots occur.

Behavior Changes

• Emit assistant replacement snapshots instead of suppressing rewritten stream updates.
• Let the webchat controller replace the current stream with shorter corrected snapshots.
• Keep OpenResponses' accumulated text aligned with replacement snapshots.
• Add regressions for the rewind case in both the agent stream and the webchat controller.

Codebase and GitHub Search

• Related issue: #58631
• Code paths reviewed: src/agents/pi-embedded-subscribe.handlers.messages.ts, ui/src/ui/controllers/chat.ts, ui/src/ui/chat/message-extract.ts, ui/src/ui/chat/grouped-render.ts, ui/src/ui/markdown.ts, src/gateway/openresponses-http.ts
• Existing tests reviewed: src/agents/pi-embedded-subscribe.subscribe-embedded-pi-session.subscribeembeddedpisession.e2e.test.ts, ui/src/ui/controllers/chat.test.ts, ui/src/ui/markdown.test.ts

Tests

• Passed: pnpm exec vitest run --config vitest.config.ts src/ui/controllers/chat.test.ts src/ui/chat/message-extract.test.ts src/ui/markdown.test.ts
• Failed outside this change: pnpm check currently reports repo-wide format-check failures across many files.
• Failed outside this change: pnpm build currently fails in vendor/a2ui/renderers/lit/src/0.8/model.test.ts during canvas:a2ui:bundle with missing Node builtin type names.
• Failed outside this change: pnpm exec vitest run --config vitest.e2e.config.ts src/agents/pi-embedded-subscribe.subscribe-embedded-pi-session.subscribeembeddedpisession.e2e.test.ts currently aborts before running tests with getOAuthProviders is not a function.

Manual Testing

Not run locally beyond the targeted automated regression coverage above.

Sign-Off

• Models used: GPT-5.4
• Submitter effort: investigated the reported repro path, implemented a focused fix, and ran targeted validation.
• Agent notes: AI-assisted change; lightly tested with targeted UI regressions and issue/code-path review. lobster-biscuit

Made with Cursor

Changed files

• src/agents/pi-embedded-subscribe.handlers.messages.ts (modified, +9/-5)
• src/agents/pi-embedded-subscribe.subscribe-embedded-pi-session.subscribeembeddedpisession.e2e.test.ts (modified, +7/-2)
• src/gateway/openresponses-http.ts (modified, +8/-4)
• ui/src/ui/controllers/chat.test.ts (modified, +19/-0)
• ui/src/ui/controllers/chat.ts (modified, +2/-5)