> ## Documentation Index > Fetch the complete documentation index at: https://praison.ai/docs/llms.txt > Use this file to discover all available pages before exploring further. # Chat & Streaming > Send messages, stream replies, and read tool cards in the Desktop app Every reply streams live from your local agent β€” text, reasoning, tool cards, and usage all arrive as typed events over `127.0.0.1`. ```python theme={"theme":{"light":"vitesse-light","dark":"vitesse-dark"}} from praisonaiagents import Agent agent = Agent( name="Assistant", instructions="You are a helpful assistant.", ) # The Desktop app streams this agent's reply token-by-token. agent.start("Write a haiku about the sea", stream=True) ``` ```mermaid theme={"theme":{"light":"vitesse-light","dark":"vitesse-dark"}} graph LR You[πŸ‘€ You] --> Msg[πŸ’¬ Message] Msg --> Engine[🧠 Engine] Engine --> Stream[πŸ“‘ SSE Events] Stream --> Turn[βœ… Rendered Turn] classDef you fill:#8B0000,stroke:#7C90A0,color:#fff classDef msg fill:#6366F1,stroke:#7C90A0,color:#fff classDef engine fill:#189AB4,stroke:#7C90A0,color:#fff classDef stream fill:#F59E0B,stroke:#7C90A0,color:#fff classDef turn fill:#10B981,stroke:#7C90A0,color:#fff class You you class Msg msg class Engine engine class Stream stream class Turn turn ``` ## Quick Start Type in the composer and press `Enter`. The reply streams in as the agent produces it. Text, a live reasoning panel, tool cards, and a usage line all appear in the same turn as they stream. Hover a turn to **Copy**, **Regenerate**, **Fork**, or **Delete** it. *** ## How It Works The Desktop app opens `POST /chat` and streams these 11 event types straight into the turn β€” you write no client code for it. ```python theme={"theme":{"light":"vitesse-light","dark":"vitesse-dark"}} from praisonaiagents import Agent agent = Agent( name="Assistant", instructions="You are a helpful assistant.", ) # The Desktop app opens POST /chat and streams these 11 event types # straight into the turn β€” you write no client code for it. agent.start("Summarize today's notes", stream=True) ``` The engine sends Server-Sent Events on `POST /chat`. ```mermaid theme={"theme":{"light":"vitesse-light","dark":"vitesse-dark"}} sequenceDiagram participant You as πŸ‘€ You participant App as 🌐 App participant Engine as 🧠 Engine participant Agent as πŸ€– Agent You->>App: type message + Enter App->>Engine: POST /chat (prompt) Engine->>Agent: agent.start(stream=True) Agent-->>Engine: chunks Engine-->>App: start / delta / tool_call / usage / end App-->>You: streamed turn ``` Each event maps to one visible piece of the turn: ```mermaid theme={"theme":{"light":"vitesse-light","dark":"vitesse-dark"}} graph LR Send[πŸ’¬ Send] --> Start[🟒 start] Start --> Reason[🧠 reasoning] Reason --> Delta[✍️ delta] Delta --> Draft[πŸ”§ tool_drafting] Draft --> Call[πŸ”¨ tool_call] Call --> Ask[πŸ”‘ approval_request] Ask --> Result[πŸ“¦ tool_result] Result --> Use[πŸ“Š usage] Use --> End[βœ… end] classDef input fill:#6366F1,stroke:#7C90A0,color:#fff classDef middle fill:#F59E0B,stroke:#7C90A0,color:#fff classDef success fill:#10B981,stroke:#7C90A0,color:#fff class Send input class Start,Reason,Delta,Draft,Call,Ask middle class Result,Use,End success ``` Every event carries a `msg_id` that scopes it to a specific assistant message; `start` additionally carries a `run_id` that scopes it to a specific run, so a `POST /approve/{aid}` or `POST /cancel` sent later addresses the right run and not whichever one happens to be pending. The vocabulary is exactly the **11 events** below β€” a `StreamProtocolVocabulary` test in the engine fails CI if a new emitter or a new documented event ever drifts from that list, so this table stays a faithful mirror of the wire. Every event the stream emits (from `engine/server.py`), with the exact payload a client sees on the SSE wire: | Event | Payload | Rendered as | | - | - | - | | `start` | `{msg_id, run_id}` | New assistant turn container | | `reasoning` | `{msg_id, text}` (incremental) | Live "Thinking… Xs" panel (collapses to "Thought for Xs") | | `delta` | `{msg_id, text}` | Streamed text into the current turn | | `tool_drafting` | `{msg_id, name}` | "Preparing tool…" state / argument preview inside a tool card | | `tool_call` | `{msg_id, call_id, name, args}` | Tool card (running dot) | | `tool_result` | `{msg_id, call_id, name, ok, output, seconds}` | Tool card result pane (tail-truncated with **Show all** + **Copy output**) | | `approval_request` | `{msg_id, approval_id, call_id, name, args}` | [Approval card](/docs/features/desktop/approvals) (Allow / Always allow / Deny) β€” human-in-the-loop gate | | `usage` | `{msg_id, chars, seconds, ttft}` | Chars, seconds, time-to-first-token under the reply | | `cancelled` | `{msg_id, run_id}` | "Stopped" indicator | | `error` | `{msg_id, message, kind}` | Typed error card β€” `auth` / `rate_limit` / `no_answer` / `empty` / `internal` | | `end` | `{msg_id, user_index, assistant_index, versions, active}` | Finalizes the turn | Every event carries `msg_id` so the client can address a specific message rather than assuming the last one is live. Clients integrating with the SSE stream should handle **all 11** events β€” a client written against a subset silently ignores the rest, and `approval_request` in particular will block the run invisibly until the 300 s [approval timeout](/docs/features/desktop/approvals) if the client does not render it. Silence is treated as a failure, and the two shapes are reported differently: * **`empty`** β€” nothing at all happened (no text, no tools). Still reported as **"No output"**. * **`no_answer`** β€” the tools ran but the model produced no follow-up answer. Reported as **"The tools ran, but no answer came back"** and lists how many tool calls succeeded above. Tool cards remain rendered even when the answer never arrives β€” the work isn't hidden by a failure banner. *** ## Capabilities When the model emits reasoning, a live "Thinking… Xs" panel shows it and collapses to "Thought for Xs" when the turn ends. Toggle it with **Show reasoning** and **Collapse reasoning by default** in Settings. A `tool_call` opens a card with a running dot; `tool_drafting` previews the arguments; `tool_result` fills the result pane. Long output is tail-truncated with **Show all** and **Copy output**. Tool cards remain visible even if the model produces no follow-up answer β€” a `no_answer` banner then explains what didn't come back. Drop a file and the composer branches on its MIME type β€” images and PDFs reach a vision model as bytes, everything else folds into the prompt as text. ```mermaid theme={"theme":{"light":"vitesse-light","dark":"vitesse-dark"}} graph TB Drop[πŸ“Ž File dropped] --> Mime{MIME type?} Mime -->|image/* or application/pdf| Vision[πŸ–ΌοΈ base64 data: URL
β†’ agent.start attachments=] Mime -->|anything else| Text[πŸ“„ Clip to 100 kB
β†’ fold into prompt] Vision --> Model[🧠 Vision model sees bytes] Text --> Model classDef input fill:#6366F1,stroke:#7C90A0,color:#fff classDef decision fill:#F59E0B,stroke:#7C90A0,color:#fff classDef process fill:#189AB4,stroke:#7C90A0,color:#fff classDef result fill:#10B981,stroke:#7C90A0,color:#fff class Drop input class Mime decision class Vision,Text process class Model result ``` Drag-drop or use the **+** button. Chips show each file's size. Limits: **2 MB max**, up to **5 files**. * **Images (`image/*`) and PDFs** are read as base64 and passed to the agent as `attachments=[...]`, so a vision-capable model (`gpt-4o`, `claude-3-*`, `gemini-*`) sees the image itself β€” not a text description of it. Point the Desktop app at a text-only model and the image is ignored silently. * **Text files** are clipped to **100 kB** of text and folded into the prompt, so long pastes condense into an attachment instead of filling the context. Only text is stored in the turn's history; the image bytes are ephemeral to the turn. Point Desktop at a vision-capable model (`gpt-4o`, `claude-3-7-sonnet-*`, `gemini-2.0-flash`, …) if you want it to actually see dropped images. A text-only model still runs, but the image never reaches it. **Stop** cancels a live run β€” the client is told explicitly with a `cancelled` event rather than inferring it from silence. Cancelling with **Stop** no longer double-reports as "No output" β€” a `cancelled` event is the only banner the user sees. Per-turn hover actions cover **Copy**, **Regenerate**, **Fork** (`POST /fork/{cid}/{idx}`), and **Delete message** (`DELETE /messages/{cid}/{idx}`). *** ## Message Versions Regenerating an answer keeps the previous one as a prior version on the same message, so you can compare without copying anything out. ```mermaid theme={"theme":{"light":"vitesse-light","dark":"vitesse-dark"}} graph LR Answer[πŸ’¬ Answer v1] --> Regen[πŸ” Regenerate] Regen --> V2[πŸ’¬ Answer v2] V2 --> Pick[β—€ 2/2 β–Ά picker] classDef msg fill:#8B0000,stroke:#7C90A0,color:#fff classDef act fill:#189AB4,stroke:#7C90A0,color:#fff classDef pick fill:#10B981,stroke:#7C90A0,color:#fff class Answer,V2 msg class Regen act class Pick pick ``` * **Regenerate** sends `POST /chat` with `regenerate_of` set to the message index, so the new answer is filed as another version instead of a duplicate question. * A `< 1/2 >` picker appears on hover once a message has more than one version, opening at the newest. * Stepping through the picker calls `POST /version/{cid}/{idx}/{n}` and repaints the chosen answer. * In the server payload every assistant row exposes `versions`, `active`, `version_count`, and `version_active`. A message written before versioning has no `versions` key and is its own single version β€” nothing to pick between, so no picker shows. *** ## Message Queue Typing while a turn is running queues your next message instead of interrupting it. * The queued message sends automatically when the current turn finishes. * **Stop** clears the queue rather than sending it β€” cancelling means "not this either". *** ## In-App Confirmation Dialogs Destructive actions β€” delete conversation, delete-all, delete message β€” route through an in-app modal, not the browser's `window.confirm`. `window.confirm` returns `false` immediately in WKWebView, which silently cancelled every destructive action. The in-app dialog is why **Delete conversation** now actually works. The `confirm_delete` setting gates whether the dialog appears at all. *** ## Keyboard Shortcuts | Key | Action | | - | - | | `⌘N` | New chat | | `⌘K` | Search all conversations | | `⌘,` | Open settings | | `Enter` | Send | | `Shift+Enter` | Newline | | `Esc` | Close overlay | *** ## Related How tool calls are approved before they run Fork, delete, projects, and `⌘K` search This documentation is built and hosted on [Mintlify](https://mintlify.com), a developer documentation platform.