Most teams begin building voice agents on Retell because it removes early friction. You can prototype quickly, test ideas fast, and get a proof-of-concept running in hours.
That’s the same story I’ve heard from founders in real estate, healthcare scheduling, auto services, recruiting, and a dozen other verticals.
But as traffic increases, the cumulative costs and underlying infrastructure problems with Retell inevitably begin to cause issues.
In the last quarter alone, I’ve spoken with more than 40 companies who hit similar ceilings. Their feedback is consistent enough that it’s worth surfacing here, because it explains why we built a direct Retell import flow at Telnyx, and why teams see performance gains without changing a single line of their agent logic.
What teams consistently report about Retell’s limitations
After dozens of interviews, 3 themes come up every time:
1. Latency becomes unpredictable once call volume increases
Teams often describe a pattern – the first demos feel fine, but production traffic exposes jitter, response delays, or barge-in failures.
The root cause is structural. Retell runs on public-cloud GPUs and relies on external telephony providers. Audio leaves the speech path, crosses multiple networks, and hits third-party inference endpoints before returning.
Each hop adds small delays that compound under load.
Developers described it this way:
“It wasn't that Retell was slow; it was that it was inconsistent.”
2. Telephony is the hard part, and Retell doesn’t own it
Multiple teams reported that Retell performed adequately until they encountered issues related to carrier performance, such as spam filtering, regional routing irregularities, connection difficulties, or DTMF inaccuracies.
Because Retell depends on other carriers to deliver calls, they can’t fix these issues at the root.
Teams often heard:
“We escalated it to our carrier partner.”
Which basically means: the problem is outside Retell’s control.
When your AI depends on reliable, real-time audio, “outside our control” is a deal-breaker.
3. Multi-step logic becomes complicated to maintain
Retell's "prompt trees" work for small flows. As complexity increases, such as scheduling handoffs, verifying data, or conditional routing, teams either hit UI constraints or end up writing brittle logic around a single monolithic agent.
One head of engineering put it plainly:
“We needed explicit control over sub-flows. Retell hid too much inside one big prompt.”
When building production agents, transparency and modularity matter.
What changes when teams migrate to Telnyx
Across interviews, teams reported 3 immediate changes after moving their Retell prompts to Telnyx:
1. Latency drops because the network changed.
Telnyx colocates GPU inference with our telephony stack. That removes the cloud-to-cloud hops Retell can’t avoid.
Most teams described a shift from ~400–600ms response loops to sub-500ms with the same TTS, STT, prompts and LLMs.
2. Telephony becomes consistent because Telnyx is the carrier
There are no soft handoffs to partner carriers, opaque routing, and undiagnosable PSTN issues.
With Telnyx owning both the dial tone and the AI, you get one accountable system from start to finish.
3. Complex flows become explicit and maintainable
Multi-step Retell agents import into Telnyx as connected assistants:
- Warm-intro assistant
- Qualifying assistant
- Scheduling assistant
- Callback assistant
Every branch becomes its own assistant with clear handoff rules. Developers finally see the structure they were previously guessing at.
Why Telnyx built a direct Retell import flow
We kept hearing variations of the same line:
“We want to switch, but we don’t want to rebuild everything.”
So we made that unnecessary.
The import flow pulls in:
- system prompts
- tools
- branching logic
- multiprompt structures
- assistant configurations
… and converts them into Telnyx-native agents automatically.
This matters because when teams move from Retell to Telnyx, they aren’t looking for new behavior. They’re looking for the same behavior, just faster and more reliable.
Step-by-step process on how the import works
1. Add your Retell API key
Navigate to Mission Control, go to AI Assistants in AI Storage & Compute, Select Import assistant.
Choose Retell from the drop down and enter your Retell API Key. Paste your key and save it securely.
2. Load available Retell agents
Telnyx fetches your agents, which can be single-prompt or multi-prompt.
3. Select and import
Choose the agents you want and Telnyx recreates them as native assistants.
4. Multi-prompt agents automatically split into a modular agent graph
Each branch becomes its own assistant with a handoff connection.
5. Test immediately
Run a live test call. See full transcripts, STT, TTS, and logic transitions in real time.
The bigger picture
To be clear, Retell isn’t “bad.” It solves an important early-stage problem: speed of experimentation.
But once teams run:
- real inbound support calls
- high-volume outbound campaigns
- regulated workflows
- multi-step business logic
- integrations with CRMs, schedulers, or internal APIs
… they need predictable latency, consistent telephony, and end-to-end visibility.
That’s the gap the market opened.
And that’s the gap the Telnyx import flow closes.
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