features

Features

This section documents the cross-cutting capabilities of Prime Agent that span multiple packages: the web chat surface in web/, the agent runtime in packages/coding-agent, and the LLM layer in packages/ai. Where package pages describe one package's structure and files, feature pages follow a single capability end to end from the browser through the server adapter into the agent loop.

The web chat wire contract is defined in web/protocol (web/protocol/src/chat-protocol.ts) and adapted in web/server (web/server/src/event-mapper.ts, web/server/src/prime-bridge.ts). The agent runtime is packages/coding-agent; the LLM provider abstraction is packages/ai. Feature pages refer to these package pages for the underlying structure.

Feature pages

• streaming-chat: the end-to-end streaming architecture: NDJSON turn stream over POST /api/chat, the SSE push channel with ring-buffer replay, and the client stream state machine.
• tool-cards: the tool-call rendering lifecycle: tool events become ChatToolPart cards with a state machine, dispatched through the tool renderer and registry.
• providers-and-models: how a user authenticates against LLM providers and selects models, from credential storage to the model picker.
• sessions-and-branching: session lifecycle, JSONL transcripts, resume, fork, and branch switching.
• slash-commands: /command interactions in both the TUI and the web client, with autocomplete.
• mcp: Model Context Protocol client support, including OAuth and the server catalog.
• oauth: OAuth login flows for providers such as Anthropic, GitHub Copilot, and OpenAI Codex.

The mcp, oauth, sessions-and-branching, and slash-commands pages are documented alongside this batch; see also session lifecycle and the glossary for term definitions.

How features map to packages

Each feature is a thin slice across a predictable set of packages:

Feature	Wire contract	Server adapter	Client / UI	Runtime
Streaming chat	web/protocol/src/chat-protocol.ts	web/server/src/prime-bridge.ts, web/server/src/event-mapper.ts, web/server/src/ring-buffer.ts	web/app/src/lib/pi/chat-stream-state.ts, web/app/src/lib/pi/use-pi-chat.ts	packages/coding-agent AgentSession
Tool cards	web/protocol/src/chat-types.ts (ChatToolPart)	web/server/src/event-mapper.ts (tool frames)	web/design/src/components/agent-elements/tools/	packages/coding-agent tool execution
Providers and models	web/protocol/src/provider-catalog.ts, model-patterns.ts	web/server/src/handlers/chat-providers.ts, chat-models.ts, chat-models-discover.ts	web/design/src/components/agent-elements/input/model-picker.tsx	packages/ai/src/models.ts, packages/coding-agent/src/core/model-registry.ts, auth-storage.ts, settings-manager.ts
Sessions and branching	web/protocol/src/chat-protocol.ts (session metadata)	web/server/src/handlers/chat-new.ts, chat-resume.ts, chat-sessions.ts	web/app/src/lib/pi/use-pi-chat.ts	packages/coding-agent/src/core/session-manager.ts
Slash commands	web/protocol/src/chat-protocol.ts (commands)	web/server/src/handlers/chat-command.ts, chat-commands.ts	web/app/src/lib/pi/slash-commands.ts	packages/coding-agent/src/core/slash-commands.ts
MCP	(in agent runtime)	web/server custom MCP tool renderers	web/design/src/components/agent-elements/tools/mcp-tool.tsx	packages/ai/src/mcp.ts, packages/ai/src/mcp/
OAuth	web/protocol/src/provider-catalog.ts (authType)	web/server/src/handlers/chat-providers-oauth.ts	web/app/src/routes/api/chat/providers/oauth.ts	packages/ai/src/utils/oauth/, packages/coding-agent/src/core/auth-storage.ts

Related pages

• The web stack packages: web-server, web-app, web-design, web-protocol.
• LLM provider abstraction: packages/ai index.
• Session lifecycle: packages/coding-agent session-runtime.
• HTTP endpoint reference: web-api.
• Term definitions: glossary.