The `/api/flows/cron` route gated on `supplied !== expected`, which
compares strings byte-by-byte with early exit on first mismatch.
An attacker who can hit the endpoint could in principle recover the
secret one byte at a time by measuring response-time deltas. With
a high-entropy 64-char secret this is mostly theoretical, but the
upgrade is a one-liner.
Switch to crypto.timingSafeEqual with a length pre-check (the
function throws on mismatched lengths; the length itself isn't
sensitive when the expected value is set by the operator).
Not touching the equivalent line in /api/automations/cron in this
PR — one fix per branch keeps the diff easy to review and revert.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
Brings the Flows feature alive end-to-end for beta-opted-in accounts.
Still no UI — flows are defined via direct SQL inserts in v1; the
no-code builder lands in PR 3. Everything in this PR is gated behind
`isFlowsEnabled(profile)` so non-beta accounts behave identically to
before.
What landed:
1. `src/lib/flows/types.ts` — DB row + discriminated-union node
config types, plus the `ParsedInbound` shape and a
`DEFAULT_FALLBACK_POLICY`.
2. `src/lib/flows/fallback.ts` — pure policy resolver. Decides
whether an unknown reply triggers a reprompt (up to N times),
a handoff, or end. 11 unit tests.
3. `src/lib/flows/engine.ts` — `dispatchInboundToFlows()` entry
point. Loads the active run (if any), checks idempotency via
`flow_run_events`, advances the run through a synchronous
auto-advance loop that suspends only at nodes that need
customer input. Each suspending node calls
`engineSendInteractive{Buttons,List}` and persists the new
current_node_key via an optimistic UPDATE with a precondition
on the OLD key — concurrent inbounds collide cleanly.
11 unit tests for the pure-logic helpers.
4. `src/app/api/whatsapp/webhook/route.ts` — invokes the runner
between the broadcast-reply flag and the automation dispatch.
When the runner consumes the inbound (started a flow, advanced
one, applied a fallback), suppresses `new_message_received`
and `keyword_match` automation triggers — the customer is
navigating the bot menu, not throwing a keyword. Relationship
triggers (new_contact_created, first_inbound_message) still
fire regardless.
5. `src/app/api/whatsapp/send/route.ts` — after a successful
agent message, marks any active flow run for that contact as
`paused_by_agent`. Best-effort: a write failure is logged but
doesn't block the send response.
6. `src/app/api/flows/cron/route.ts` — sweeps active runs whose
`last_advanced_at` is older than the flow's
`fallback_policy.on_timeout_hours` (default 24h). Marks them
`timed_out` and writes a `flow_run_events.timeout` row. Re-uses
`AUTOMATION_CRON_SECRET` so operators don't have to provision
a second secret.
Test surface in this PR:
- 142/142 tests pass (added 22 new unit tests across fallback +
engine pure logic)
- typecheck clean
- 0 new lint errors
- build clean
Manual end-to-end verification arrives via the SQL fixture in the
PR description (a 3-node Welcome → buttons → handoff flow).
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
