Migrate to Sent
Every migration from a major CPaaS provider hits the same five translation problems. Work them in this order, because the first one silently doubles cost and is invisible in tests.
1. Ordered fallback becomes automatic routing
Incumbent platforms express cross-channel delivery through different caller-side arrays, failover objects, messaging-service features, or application-level priority configuration. Do not assume those shapes have a direct Sent request-field equivalent.
Sent's array is a broadcast list. Porting an ordered array produces one message and one charge per recipient-channel pair, which passes tests and multiplies production spend. The correct translation is automatic routing — omit
or send
— which lets the platform select a route and reroute across up to three channel-and-provider pairs on the same
. Details belong to
; the migration rule is simply:
never port an ordered channel list.
2. Status vocabularies do not line up
Incumbent statuses map onto Sent's, but Sent adds two states that have no equivalent and that break naive retry logic.
| Sent status | Closest incumbent analogue | Migration note |
|---|
| Twilio , Sinch | Accepted, not sent |
| no analogue | Route chosen; fires again on reroute |
| Twilio , Sinch | Provider handoff only |
| everywhere | The first proof of handset receipt |
| Twilio , Sinch | WhatsApp and RCS only |
| , | May still reroute; not necessarily final |
| Twilio error 21610 (opt-out) | Policy gate. Never retry |
| account-level errors | Account precondition. Fix the account, then resend |
| no analogue | Quiet-hours parking; resumes automatically |
Two consequences for ported code. Handlers that treat every non-delivered terminal state as retryable will retry consent blocks, which is a compliance failure rather than a bug. And handlers keyed on numeric provider error codes — Twilio's
is the classic — must be rewritten against Sent's string
families.
3. Webhook verification is a rewrite, not a port
No two providers sign the same way, and no Sent SDK ships a verifier.
| Provider | Scheme |
|---|
| Twilio | , base64 HMAC-SHA1 over the full URL plus sorted POST parameters |
| Sinch | HMAC-SHA256 over , four x-sinch-webhook-signature*
|
| Infobip | Basic, HMAC-SHA256 over the raw body, or OAuth on a notification profile; the header name is account-configured |
| Vonage | JWT in , or a legacy parameter |
| MessageBird/Bird | , base64 HMAC-SHA256 over timestamp, URL, and a SHA-256 body hash |
| Sent | x-webhook-signature: v1,{base64}
{x-webhook-id}.{x-webhook-timestamp}.{raw_body}
|
Sent's key is the signing secret with
stripped and the remainder base64-decoded, compared in constant time, with timestamps outside 300 seconds rejected. Because Sent provides no per-event id, dedupe keys must be derived from payload semantics. Build the receiver with
rather than adapting the incumbent's verifier.
4. Opt-out stores must be reconciled, not migrated by copy
Every provider keeps its own suppression list — Twilio Advanced Opt-Out, Infobip Blocklist, Sinch OPT_IN/OPT_OUT events. Sent enforces consent at the platform level before events reach the application, stores it as
on the contact, and applies it
channel-agnostically: a
on SMS suppresses WhatsApp and RCS too.
Reconciliation rules: export the incumbent's suppression list before cutover, treat any opt-out on any incumbent channel as a global Sent opt-out, and never clear
to "clean up" migrated data. Sent's ten default keywords are
,
,
,
,
,
,
,
,
,
, matched only when the entire trimmed body equals the keyword — so incumbent-specific keywords need custom keyword entries. Rewrite any incumbent keyword matcher as an exact local consent mirror and audit mechanism; the matcher must not write consent to Sent again. Consent semantics belong to
.
5. Templates and tenancy are re-registered, not transferred
WhatsApp templates live with the WABA, so the migration question is whether the WABA moves. Positional placeholders (
,
) become
named parameters in Sent, which means every call site that passed an ordered array must pass a named map. Approval is asynchronous and arrives as a
webhook event, so build the template inventory before cutover rather than during it.
Tenancy maps as follows, with the boundary decision owned by
and the API work by
sent-profile-provisioning
:
| Incumbent construct | Sent equivalent |
|---|
| Twilio subaccount | Sender Profile |
| Twilio Messaging Service | routing plus profile configuration, not a caller-side pool |
| Infobip Application or Entity | Sender Profile |
| Sinch Conversation API app | Sender Profile |
| Provider API credential per tenant | Profile-scoped API key, or organization key with |
Migration sequence
- Inventory every send call site, webhook handler, status branch, template, suppression list, and credential. Use
scripts/inventory_scan.py
- Map each item using references/provider-mapping.md, flagging ordered-fallback arrays and numeric error codes as required rewrites.
- Stand up Sent in parallel: credentials, one webhook per environment, verified receiver, templates re-registered and approved.
- Prove equivalence in sandbox with , then with a small live cohort confirmed to .
- Dual-run with a traffic split, comparing delivery rates, latency, and cost per message on the same message classes.
- Cut over by message class — lowest-risk transactional first, marketing last — keeping the incumbent receiver live.
- Decommission only after a full billing cycle of clean data, then revoke incumbent credentials.
Sequencing detail, verification gates, and rollback triggers are in references/cutover-playbook.md.
Mistakes that survive testing
- Porting an ordered channel array. Doubles cost, never errors.
- Treating as retryable. Compliance exposure.
- Reusing the incumbent's signature verifier. Every delivery returns 401.
- Assuming means delivered. Sent acknowledges acceptance only.
- Keeping positional template placeholders. Parameters silently mismatch.
- Retrying on . Ten consecutive auth failures lock the credential with escalating lockout.
- Omitting during dual-run. A timeout retry sends twice.
- Sending with a profile-scoped key. Returns .
- Copying an incumbent's pattern. Sent authenticates with .
Boundaries
This skill owns provider mapping and line-by-line migration planning. Hand the resulting Sent client and resilience work to
, channel semantics to
, receiver construction to
, WhatsApp onboarding to
, and US campaign registration to
.