Changelog

0.3.7 — 2026-04-18

CanvasMiddleware — opt-in LangChain agent middleware that injects canvas tools and report-building guidance into any create_deep_agent call. Downstream users enable the canvas feature via middleware=[CanvasMiddleware()] without touching tool lists or system prompts.
Canvas section item type (add_canvas_section(title, level=1)) — structural headings that render as h1–h6 in the UI for report organization.
reorder_canvas(item_ids) tool — rewrite canvas items in a new order.
Provenance: canvas items now record source_cell and execution_count from the most recent notebook cell execution; surfaced as a “cell N” pill in the UI.
Tab visibility controls: show_canvas / show_files on CoworkApp, --show-canvas/--no-show-canvas and --show-files/--no-show-files CLI flags, DEEPAGENT_SHOW_CANVAS / DEEPAGENT_SHOW_FILES env vars. Canvas tab defaults to auto-detect (on when CanvasMiddleware is attached, off otherwise); files tab defaults to on.
agent_uses_canvas_middleware(agent) helper for downstream detection.
Integration tests for the SSE streaming pipe (tests/test_sse_adapter.py) using a conformant fake agent — catches API drift in langgraph-stream-parser before it hangs the UI.
API contract guards for prepare_agent_input and create_resume_input signatures.
demo/plain_agent.py — minimal example of a custom agent without canvas middleware.

Agent streaming hung silently when prepare_agent_input() was called with an unsupported context_parts= kwarg. Context is now prepended to the user message directly.
CanvasMiddleware.awrap_model_call async variant — the sync-only wrap_model_call crashed with NotImplementedError under agent.astream().
run_agent_stream / run_interrupt_response now wrap the full function body in a try/except and emit error events for uncaught exceptions instead of dying silently in the background task.

Canvas tools are no longer baked into AGENT_TOOLS — they are injected exclusively via CanvasMiddleware to avoid double-registration.
Default-agent system prompt no longer embeds canvas guidance; the prompt is appended at call time by CanvasMiddleware.

Dead NotebookState._canvas_items list and get_canvas_items / clear_canvas_items methods (never populated; replaced by file-backed canvas state).
Dead create_session_agent factory that imported a non-existent cowork_dash.backends module.

Replace WebSocket streaming with Server-Sent Events (SSE) for reliable operation behind reverse proxies and with host=0.0.0.0
Frontend useAgentStream hook now uses EventSource + fetch() instead of WebSocket
Session manager uses async event queues instead of WebSocket references
Authentication middleware simplified (no more WebSocket-specific handling)

GET /api/stream SSE endpoint with 30s keepalive and X-Accel-Buffering: no header for nginx compatibility
POST /api/chat endpoint to send user messages
POST /api/chat/interrupt endpoint to respond to HITL interrupts
POST /api/chat/cancel endpoint to cancel running streams

Custom CSS theming support via --custom-css CLI flag, custom_css Python API param, or DEEPAGENT_CUSTOM_CSS env var
/api/custom-css endpoint serves theme file at runtime; frontend injects it dynamically
POST /api/session/{id}/inject REST endpoint for fire-and-forget message injection from external apps
GET /api/sessions endpoint to list all sessions with connection status
inject.py convenience script for programmatic message injection
Theme reference documentation (docs/CUSTOM_THEME_REFERENCE.md)

Dark mode text color in canvas markdown content (.markdown-content missing base color)
Interrupt dialog diagnostics for empty action_requests

/create-workflow slash command with two-step text input flow for creating workflows from scratch
create_workflow_prompt configurable via Python API, CLI (--create-workflow-prompt), and env var (DEEPAGENT_CREATE_WORKFLOW_PROMPT)
README documentation for slash commands, authentication, and workflow prompt configuration

Refactored slash command hasArg boolean to secondStep union type ("none" | "file-picker" | "text") for extensibility
Generalized tryExecute and handleInputChange to work with any command definition

Print/export conversation via browser Print dialog with print-optimized CSS
/save-workflow slash command to capture conversations as reusable workflow markdown files
/run-workflow slash command with autocomplete dropdown listing .md files from ./workflows/
Configurable workflow prompts via Python API (save_workflow_prompt, run_workflow_prompt), CLI flags, and env vars

Optional HTTP Basic Auth (Dash-style) — enable with DEEPAGENT_AUTH_PASSWORD env var, --auth-password CLI flag, or auth_password Python kwarg
Username defaults to admin when only password is set; customize via DEEPAGENT_AUTH_USERNAME
Protects all HTTP and WebSocket endpoints with timing-safe credential comparison

Session persistence across page refresh (messages, todos, token usage saved to localStorage)
HITL interrupt tests for single and multi-interrupt serialization

Fix HITL interrupt dialog showing blank (no tool name or args displayed)
Fix interrupt approval sending empty decisions ({"decisions": []})
Fix Decision type for edit case to use edited_action matching backend format
Fix display_inline crash and blank screen rendering (records vs data format mismatch)
Add error boundary around inline display to prevent white-screen crashes
Rename display_inline parameter from content to file_path to clarify filepath-only usage

Fix wheel build to include frontend static assets
Inline HTML and Plotly chart rendering via sandboxed iframes
Icon customization, agent name inference, auto theme, favicon
Streaming improvements: cancel support, tool previews, scroll anchoring, message timing
Token usage chart with per-turn breakdown
File browser, canvas, todo panel, and dark mode style polish

Initial release of cowork-dash.

Chat interface with real-time token streaming via WebSocket
Tool call visualization with inline display of arguments, results, duration, and status
Rich inline content rendering: HTML, Plotly charts, images, DataFrames, PDFs, JSON
Canvas panel for persistent visualizations (Plotly, matplotlib, Mermaid diagrams, DataFrames, Markdown, images)
File browser with syntax-highlighted viewer and live file change detection
Task tracking sidebar with progress bar, synced with agent write_todos calls
Human-in-the-loop interrupt dialog for reviewing and approving agent actions
Token usage counter with per-turn breakdown chart
Light, dark, and system-auto theming
Customizable title, subtitle, welcome message, agent name, and icon
CLI (cowork-dash run) and Python API (CoworkApp, run_app)
Configuration via Python args, CLI flags, or environment variables