Voice fails. The message still lands.

ChimeFlow is a workbench for teams building agentic conversations on AWS Communication Developer Services. Design a flow across Amazon Chime SDK voice, AWS End User Messaging and Amazon SES, break a carrier on purpose, and watch the guardrails hold.

Open the failover bench Press a keypad

Live output of the same engine that powers the bench. Here the clinic reminder call times out twice, text takes over, and the recipient asks for a nurse.

The workbench needs JavaScript. It runs entirely in your browser with no network calls, so there is nothing to wait for. Enable scripts to use the failover bench, the message inspector, the keypad simulator and the AWS exporters.

Without scripts, this page still tells you what ChimeFlow checks: SMS encoding and segment math (GSM-7 and UCS-2), Luhn-verified card masking, TCPA quiet hours from 8:00 AM to 9:00 PM recipient local time, and Chime SDK, End User Messaging and SES payload shapes. The source and the tests are on GitHub.

Failover bench

Pick a scenario, set the recipient clock, then break channels. The engine replays the conversation deterministically and shows every attempt, every blocked channel and the reason.

Scenario

Recipient clock

Send time in UTC

Recipient time zone

Break a channel

Chime PSTN voice

Chime in-app audio

SMS

Guardrails

Recipient already sent STOP by SMS

Safety-critical quiet hours override

The override only applies to scenarios flagged safety critical. Whether you may use one is a question for your counsel, not this tool.

Recipient replies

Comma separated. Use digits, plain words, or the word timeout. Words like "chest pain" trigger a red flag escalation.

Step by step

Message inspector

Type any agent reply. The inspector counts encoding units the way carriers do, masks sensitive values before anything leaves the step, and prices ten thousand sends from rates you control.

Agent reply

Masked preview

What was masked

Rates

Dollars per segment

Carrier fee per segment

These two defaults are placeholders, not AWS prices. Replace them with the rates on your own bill.

Opt-out tester

Inbound reply from the recipient

Call and message simulator

Run the scenario from the bench as a live conversation. When the prompt is a voice call, press the keypad. Each key plays its real dual tone, a low and a high sine wave added together, and the state machine branches on the digit.

Waiting for a key.

Reply in words

Play keypad tones

State machine

Conversation log

AWS export

Templates for the selected scenario, built from the documented request shapes. Each tab is checked against the required fields in the docs before it is shown. Nothing here has been deployed or sent.

What this is, and what it is not

Planning model, not a measurement. Latencies, costs and the response delay are editable fixtures. They show how a flow behaves, not what your carriers will do.
Templates, not deployments. The exporters follow the request shapes in the AWS documentation. They have not been sent to a live account.
Policy gate, not legal advice. The 8:00 AM to 9:00 PM check is a conservative engineering rule. Which rules bind your messages depends on who you are texting and why.
Fictional organisations. The clinic, utility, airline and credit union are made up. There are no customers and no telemetry.
Redaction is pattern based. It catches the formats it knows, such as Luhn-valid card numbers and checksummed routing numbers. It will miss a name written in a sentence.