feat(daemon): refactor session init endpoints

[baxen]

add new API endpoints for session lifecycle management:

• POST /sessions/create: Create and initialize a new session with provider, model, recipe, and extensions in a single call
• POST /sessions/{id}/open: Open an existing session and setup agent
• POST /sessions/{id}/extensions: Add extensions to an active session

Consolidates both new window and load from history to use the same extension management and show the toast in both cases

Part 1 of #6251

Screen.Recording.2025-12-23.at.10.26.29.AM.mov

[baxen]

to simplify the diff on this one only adds the new endpoints and uses them in a followup pr for #6251 will cleanup unused methods

[Copilot]

Pull request overview

This PR refactors session initialization endpoints to provide cleaner separation of concerns and consolidate extension loading. It introduces three new REST endpoints (POST /sessions, POST /sessions/{id}/open, POST /sessions/{id}/extensions) and replaces the old startAgent/resumeAgent paradigm with createSession/openSession. The refactor also extracts extension loading logic into a shared utility that handles progressive loading with toast notifications, ensuring consistent behavior whether creating a new session or switching to an existing one.

Key changes:

• New session lifecycle endpoints with proper separation between creating and opening sessions
• Consolidated extension loading logic now shared between new windows and session history switching
• Backend setup_agent_for_session helper centralizes provider/model/recipe setup for both create and open flows

Reviewed changes

Copilot reviewed 9 out of 9 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
ui/desktop/src/utils/extensionUtils.ts	New shared utility for progressive extension loading with toast notifications
ui/desktop/src/hooks/useChatStream.ts	Updated to use openSession endpoint; removed legacy updateFromSession call
ui/desktop/src/hooks/useAgent.ts	Refactored to use createSession/openSession APIs instead of startAgent/resumeAgent
ui/desktop/src/components/BaseChat.tsx	Added onSessionLoaded callback to trigger extension loading when switching sessions
ui/desktop/src/api/types.gen.ts	Generated TypeScript types for new API request/response schemas
ui/desktop/src/api/sdk.gen.ts	Generated SDK client functions for new endpoints
ui/desktop/openapi.json	OpenAPI schema definitions for new session management endpoints
crates/goose-server/src/routes/session.rs	Implemented create_session, open_session, and add_session_extension endpoints with shared setup_agent_for_session helper
crates/goose-server/src/openapi.rs	Registered new endpoint handlers and request/response types in OpenAPI schema

[Copilot]

Pull request overview

Copilot reviewed 11 out of 11 changed files in this pull request and generated 1 comment.

[DOsinga]

I think if we move this to routes/agents.rs and then hook it up to agent/start and agent/resume you get the same effect, but less duplication

[baxen]

yes agree! it's on the next pr #6260

[michaelneale]

yep this looks ok to me - I like it so far. Doesn't break anything yet! over to you @DOsinga

[alexhancock]

this and #6260 LGTM

@DOsinga what do you think?