The Flow Studio

Flow Studio is a visual editor for governed sessions, served by the ADK Web UI:

cargo run -p gemini-adk-web-rs

It is a design surface over SessionSpec — everything you do on the canvas is the JSON document, and everything in the document is the fluent Rust program. The Studio invents no semantics of its own: the same compiler validates, the same FlowMonitor replays tests, the same codegen prints the program.

Flow Studio click-through: load a cookbook, drag nodes, validate, run the embedded tests, scrub a simulated session on the canvas, read the generated Rust

The canvas

Steps are nodes; after dependencies are edges. Unconditional edges are solid; conditional edges ({step, when}) render dashed with their guard as the label — the dashed is_true(is_emergency) edge below is how the clinic-intake cookbook branches to close on an emergency, merging with an any join. Terminal steps render as stadium outlines. Drag nodes to arrange them, or let Auto layout arrange the DAG; Validate compiles the flow server-side and reports diagnostics in the docked console.

The clinic-intake DAG: identify, triage, schedule, and a terminal close step, with a dashed conditional emergency edge labeled is_true(is_emergency), a green valid badge, and compile diagnostics

Structured editors

Selecting a step opens its editor: posture (the instruction imposed while the step is active), ground template (a state-interpolated fact line), tool allow/deny lists, terminal flag, gate, incoming edges with per-edge conditions, and the completion guard built from the closed Guard vocabulary — is_true, captured, called_ok, resolved, and friends, composable with any/all. Guard editors autocomplete state keys from the spec’s declared state dictionary.

Step editor: posture, ground template, allowed tools, and an any-of completion guard over symptoms_recorded and escalated

The Flow pane edits flow-level constraints (once, never … until, require, reset loops) and temporal patterns; the App pane edits instruction, tools (mock/HTTP/MCP), extraction, phases, watchers, the state dictionary, computed variables, durable memory slots, and runtime tuning. The JSON pane is the document itself, two-way: edit either side.

Tests and Preview — offline, no API key

Every bundled cookbook embeds conformance tests (user / tool / set events with expect assertions). Tests replays them through the real FlowMonitor and reports each script; Preview scrubs one test event-by-event while done and active steps light up on the canvas:

Preview mode scrubbing event 3 of 6: identify and triage marked done, schedule active, the scrubber showing the current tool event

The same replay engine runs in CI: a unit test walks the gallery manifest and requires every cookbook to compile and pass its own embedded tests.

Code — the program the document is

The Code tab shows the generated main.rs and Cargo.toml the document lowers to. Because L2 never invents semantics, generation is pretty-printing — every spec field becomes the corresponding builder call. Generated cookbook apps compile as standalone crates under RUSTFLAGS="-D warnings".

Code tab: the generated main.rs for clinic-intake — tool registration, the flow chain, and the builder calls the JSON document lowers to

Run — a live session against the canvas

Run connects a real session governed by the flow on screen. Active steps light up as the conversation progresses; the Run pane shows admitted and blocked tools, unmet requirements, and each active step’s guard truth tree — exactly which atom a stuck step is waiting on. Posture and ground edits made while connected apply on the next turn boundary (LiveHandle::update_step_posture).

The cookbook gallery

Six industry scenarios ship in the Examples menu, each a complete SessionSpec with mock tools, governance constraints, and embedded tests:

Cookbook	Industry	Highlights
Debt collection	Financial services	compliance gates, `once` payment, declarative extraction
Patient intake	Healthcare	conditional emergency edge + `any` join into close
Line support	Telecom	`reset` loop — a re-test reopens the diagnostic step
Call screening	Front desk	spam-verdict-gated transfer
Returns desk	E-commerce	eligibility-gated single refund
Table booking	Hospitality	ambient memory, computed state

The manifest lives at apps/gemini-adk-web-rs/static/examples/flows/index.json; the JSON documents next to it double as starting points for your own flows — import, edit, re-export.