[codex] Render streaming assistant deltas

[neubig]

Summary

• add a StreamingDeltaEvent frontend type and guard
• render streaming text deltas as a provisional assistant bubble during a run
• merge consecutive deltas and reconcile them against the final persisted assistant message without moving streamed text to the end of the conversation
• keep the normal optimistic user-message behavior unchanged; the experimental optimistic-message anchoring/queued-state changes were reverted

Root Cause

The agent-server can publish transient StreamingDeltaEvents, but agent-canvas treated unknown base-shaped events as non-renderable. After the first UI fix, final-message reconciliation could remove the provisional streaming deltas from their original location and leave the completed text at the end. The current branch keeps streamed content anchored where it originally appeared.

Human Validation

HUMAN: I tested this and confirmed that it is working.

Before

After

Validation

• npm test -- --run __tests__/utils/handle-event-for-ui.test.ts __tests__/components/conversation-events/chat/event-content-helpers/should-render-event.test.ts
• npm run typecheck
• npm run build

Companion SDK/server PR: OpenHands/software-agent-sdk#3376

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🐳 Docker images for this PR

• GHCR package: https://github.com/OpenHands/agent-canvas/pkgs/container/agent-canvas

Component	Value
Image	ghcr.io/openhands/agent-canvas
Architectures	amd64, arm64
Agent Server	ghcr.io/openhands/agent-server:1.23.0-python
Automation	openhands-automation==1.0.0a3
Commit	f01811659173f3f1e68760c2834542c1cdaf5c51

Pull (multi-arch manifest)

# Multi-arch manifest — Docker automatically pulls the correct architecture
docker pull ghcr.io/openhands/agent-canvas:sha-f018116

Run

docker run -it --rm \
  -p 8000:8000 \
  ghcr.io/openhands/agent-canvas:sha-f018116

All tags pushed for this build

ghcr.io/openhands/agent-canvas:sha-f018116-amd64
ghcr.io/openhands/agent-canvas:codex-acp-streaming-deltas-ui-amd64
ghcr.io/openhands/agent-canvas:pr-753-amd64
ghcr.io/openhands/agent-canvas:sha-f018116-arm64
ghcr.io/openhands/agent-canvas:codex-acp-streaming-deltas-ui-arm64
ghcr.io/openhands/agent-canvas:pr-753-arm64
ghcr.io/openhands/agent-canvas:sha-f018116
ghcr.io/openhands/agent-canvas:codex-acp-streaming-deltas-ui
ghcr.io/openhands/agent-canvas:pr-753

About Multi-Architecture Support

• Each tag (e.g., sha-f018116) is a multi-arch manifest supporting both amd64 and arm64
• Docker automatically pulls the correct architecture for your platform
• Individual architecture tags (e.g., sha-f018116-amd64) are also available if needed

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Project	Deployment	Actions	Updated (UTC)
agent-canvas	Ready	Preview, Comment	May 24, 2026 5:53pm

[neubig]

Pushed f018116 to stabilize the home page visual snapshot setup: mocked the workspaces API and increased the home-screen visibility wait. Local verification: npm run typecheck, focused Vitest suites (30 passed), and the home-page snapshot test now reaches the screenshot assertion locally instead of timing out on home-screen.\n\n_This comment was generated by an AI agent (OpenHands) on behalf of neubig._

[github-actions]

📸 Snapshot Test Report

✅ All snapshots match the main branch baselines.

Category	Count
🔴 Changed	0
🆕 New	0
✅ Unchanged	73
Total	73

✅ Unchanged snapshots (73)

archived-conversation

• conversation-panel-with-archived-badges
• conversation-view-archived
• conversation-view-sandbox-error

automations

• automations-delete-modal
• automations-list-active-inactive
• automations-no-automations
• automations-search-no-results

backends-extended

• backend-add-blank-disabled
• backend-add-cloud-advanced-open
• backend-add-cloud-no-key-disabled
• backend-add-cloud-with-key-enabled
• backend-add-form-partially-filled
• backend-add-invalid-url-disabled
• backend-add-local-ready
• backend-add-name-only-disabled
• backend-add-two-column-layout
• backend-add-whitespace-host-disabled
• backend-after-switch
• backend-cancel-nothing-saved
• backend-dropdown-two-backends
• backend-edit-prefilled
• backend-manage-after-removal
• backend-manage-two-listed
• backend-remove-cancelled
• backend-remove-confirmation
• backend-switch-overlay

backends

• backend-add-modal
• backend-manage-modal
• backend-selector-open

changes-tab

• changes-deleted-file
• changes-diff-viewer
• changes-empty

collapsible-thinking

• reasoning-content-collapsed
• reasoning-content-expanded
• think-action-collapsed
• think-action-expanded

mcp-page

• mcp-custom-server-1-editor-open
• mcp-custom-server-2-url-filled
• mcp-custom-server-3-all-filled
• mcp-custom-server-4-installed
• mcp-custom-server-editor
• mcp-empty-installed
• mcp-search-filtered
• mcp-slack-install-1-marketplace
• mcp-slack-install-2-modal
• mcp-slack-install-3-filled
• mcp-slack-install-4-installed

onboarding

• onboarding-step-0-choose-agent
• onboarding-step-1-check-backend
• onboarding-step-2-setup-llm
• onboarding-step-3-say-hello

projects-workspace-browser

• projects-workspace-browser

settings-page

• add-backend-modal
• analytics-consent-modal
• home-screen
• settings-app-page
• settings-page

settings-secrets

• secrets-add-form-filled
• secrets-add-form
• secrets-after-save
• secrets-delete-confirm
• secrets-list

settings-verification

• condenser-settings
• verification-settings-off
• verification-settings-on

sidebar

• sidebar-collapsed
• sidebar-conversation-panel
• sidebar-filter-menu

skills-page

• skills-empty
• skills-loaded
• skills-no-match
• skills-search-filtered
• skills-type-filter

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Generated by the Snapshot Tests workflow. This comment was created by an AI agent (OpenHands) on behalf of the repo maintainers.