The AI coach chat lets athletes have a real-time conversation with Rex, Astral’s built-in AI running coach. Rex has full context of an athlete’s activity history, current training plan, and upcoming workouts, so advice is specific to where they are in their training — not generic tips from a search engine. The feature is available to all athletes on the platform.
How it works
The chat runs over a persistent Socket.IO connection. When an athlete sends a message, Rex streams a response back in chunks — you’ll see the reply appear word-by-word rather than waiting for the full answer. This keeps the experience fast even for longer, more detailed responses.
Rex can be invoked two ways:
- Direct chat — the dedicated AI coach chat screen in the app
- @Rex mention — mention
@Rex in any direct message conversation to pull Rex into the thread
Accessing the chat
Open the chat tab
In the Astral app, tap the Chat icon in the bottom navigation bar.
Select the AI coach
Tap Rex at the top of your conversation list. If this is your first time, a new conversation thread opens automatically.
Ask a question
Type your question and tap Send. Rex starts responding immediately.
What Rex knows about you
Rex has access to your training context when generating a response. This includes:
- Your current training plan and upcoming workouts
- Recent activity history (runs, distances, paces)
- Your training level and preferences
This means you can ask questions like “should I run easy today?” and get a meaningful answer based on what’s on your plan and how your recent training has gone.
Sample conversation
Here’s an example of the kind of conversation you can have with Rex:
You: My legs are pretty sore after yesterday's long run. Should I do the
interval session on my plan today or take it easy?
Rex: Given that you ran 22 km yesterday at a solid effort, it makes sense
to be feeling it today. Your plan has 6×800m intervals scheduled, but
with the soreness you're describing, I'd suggest swapping that for a
30-minute easy recovery run instead.
If the soreness is mostly muscular fatigue rather than sharp pain,
the easy run will actually help flush things out without adding more
stress. Save the intervals for Thursday when you'll be fresher — your
fitness won't suffer from one adjusted session.
How does the soreness feel — is it general muscle tiredness or
something more specific?
Mentioning Rex in a DM
If you’re in a direct message conversation — for example, a thread between a coach and an athlete — either party can bring Rex into the conversation by typing @Rex at the start of a message. Rex will respond in that thread with the same context-aware advice.
The @Rex mention is rate-limited to prevent multiple simultaneous AI responses in the same conversation. If a previous Rex response is still being generated, the new mention will be queued.
Rate limits and message length
To keep the experience smooth for everyone:
- Messages have a maximum length limit. Very long messages will be rejected with an error.
- If Rex is already generating a response, sending another message will return an error asking you to wait.
Availability
AI coach chat is available to all athletes — no additional feature tier or subscription is required beyond having an active Astral account.
Coaches can view their athletes’ conversation history with Rex to understand what guidance athletes have been receiving and spot any questions that might need follow-up.
