feat(core): support render stream objects in front-end components

[akumatus]

Close AI-194

Summary by CodeRabbit

• New Features

  • Added support for streaming and displaying structured AI chat responses as "stream objects" (including text deltas, reasoning, tool calls, and tool results) across backend, API, and frontend.
  • Chat messages now include a new field for stream objects, visible in chat panels and GraphQL APIs.
  • Enhanced chat UI to render and style different types of stream objects for richer, incremental feedback.

• Bug Fixes

  • Improved handling of streamed chat responses, ensuring proper fallback to plain text if structured data is invalid.

• Refactor

  • Centralized and modularized backend logic for chat session preparation and streaming.
  • Refactored chat UI code for clearer handling of message content and stream objects.

• Tests

  • Added tests for streaming object responses and validation of structured AI outputs.

• Chores

  • Updated GraphQL schema and queries to support the new stream objects in chat message histories.

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"""

Walkthrough

This change introduces comprehensive support for streaming structured objects ("stream objects") in AI chat sessions. It spans backend schema, provider, and controller updates, GraphQL schema and queries, frontend message handling, rendering, and utilities. The implementation includes new streaming endpoints, parsing/merging logic, and test coverage for stream objects throughout the stack.

Changes

Files/Groups	Change Summary
packages/backend/server/migrations/.../migration.sql, schema.prisma	Add streamObjects JSON column/field to ai_sessions_messages table/model.
src/plugins/copilot/providers/types.ts, ai-chat-messages/type.ts	Define StreamObjectSchema, StreamObject type, and extend schemas for stream objects (backend and frontend).
src/plugins/copilot/providers/provider.ts	Add abstract streamObject method to provider interface.
src/plugins/copilot/providers/openai.ts, anthropic/anthropic.ts, gemini/gemini.ts, mocks/copilot.mock.ts	Implement streamObject method for OpenAI, Anthropic, Gemini, and mock providers.
src/plugins/copilot/providers/anthropic/official.ts, anthropic/vertex.ts, gemini/generative.ts, gemini/vertex.ts, openai.ts	Update provider model capability declarations to include ModelOutputType.Object.
src/plugins/copilot/providers/utils.ts	Add StreamObjectParser and error handling utility for streaming.
src/plugins/copilot/controller.ts	Refactor session preparation, add chatStreamObject SSE endpoint, handle stream object persistence.
src/plugins/copilot/session.ts	Persist and retrieve streamObjects in session message storage and queries.
src/plugins/copilot/resolver.ts, schema.gql, common/graphql/src/schema.ts, copilot-history-list.gql, index.ts	Extend GraphQL schema/types/queries to support streamObjects in messages.
src/__tests__/copilot-provider.spec.ts, copilot.e2e.ts, mocks/copilot.mock.ts, utils/copilot.ts	Add/extend tests for streaming object functionality and validation.
frontend/core/src/blocksuite/ai/chat-panel/chat-panel-messages.ts, ai-chat-input/ai-chat-input.ts, peek-view/chat-block-peek-view.ts	Update streaming message handling to parse, validate, and merge stream objects.
chat-panel/message/assistant.ts	Refactor message rendering to support and style stream objects.
ai/provider/request.ts	Adjust streaming argument to use 'stream-object' when not in workflow mode.
ai/utils/stream-objects.ts	Add mergeStreamObjects utility for merging consecutive stream object chunks.

Sequence Diagram(s)

sequenceDiagram
    participant User
    participant Frontend
    participant Backend
    participant Provider

    User->>Frontend: Sends chat message
    Frontend->>Backend: POST /chatStreamObject (SSE)
    Backend->>Provider: provider.streamObject(...)
    loop Streaming
        Provider-->>Backend: yield StreamObject
        Backend-->>Frontend: SSE event with StreamObject[]
        Frontend->>Frontend: Parse/Merge StreamObject(s)
    end
    Frontend->>User: Render message with streamObjects

Loading

Assessment against linked issues

Objective (Issue)	Addressed	Explanation
Frontend supports rendering stream objects (AI-194)	✅

Assessment against linked issues: Out-of-scope changes

No out-of-scope changes found.

Suggested reviewers

• akumatus

Poem

In the meadow of code, a new stream flows,
With objects that chatter as each message grows.
From backend to frontend, the rabbits all cheer,
For structured replies now magically appear!
Hop, merge, and render—what a clever delight,
Stream objects are hopping into view tonight! 🐇✨
"""

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[codecov]

Codecov Report

Attention: Patch coverage is 63.25088% with 208 lines in your changes missing coverage. Please review.

Project coverage is 55.62%. Comparing base (899ffd1) to head (9a633b9).
Report is 1 commits behind head on feat/ai-stream-objects.

Files with missing lines	Patch %	Lines
...end/server/src/plugins/copilot/providers/openai.ts	41.48%	55 Missing ⚠️
...c/plugins/copilot/providers/anthropic/anthropic.ts	17.74%	51 Missing ⚠️
...ver/src/plugins/copilot/providers/gemini/gemini.ts	17.74%	51 Missing ⚠️
...kend/server/src/plugins/copilot/providers/utils.ts	60.00%	28 Missing ⚠️
...s/backend/server/src/plugins/copilot/controller.ts	91.85%	11 Missing ⚠️
...d/server/src/plugins/copilot/providers/provider.ts	25.00%	9 Missing ⚠️
...backend/server/src/__tests__/mocks/copilot.mock.ts	91.66%	3 Missing ⚠️

Additional details and impacted files

@@                    Coverage Diff                     @@
##           feat/ai-stream-objects   #12842      +/-   ##
==========================================================
- Coverage                   55.93%   55.62%   -0.32%     
==========================================================
  Files                        2658     2658              
  Lines                      125982   126408     +426     
  Branches                    20031    19986      -45     
==========================================================
- Hits                        70474    70320     -154     
- Misses                      53172    53748     +576     
- Partials                     2336     2340       +4     

Flag	Coverage Δ
server-test	78.76% <63.25%> (-0.92%)	⬇️
unittest	31.67% <ø> (+<0.01%)	⬆️

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