Play has no accumulate handler, and that's a finding, not a gap

purchases.subscriptionsv2.get returns state now, with no per-renewal history -- so a per-renewal counter for Play has no reconcilable effect key and would silently mis-count on replay (D6).

This is one of the things Webhook Durability & Replay already handles. Receive webhooks without losing, duplicating or misordering them when the sender retries.

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Is this you?

Modeling a Google Play renewal as an accumulate-mode effect (count each renewal, like a Stripe invoice payment) looks consistent with how every other provider in the pipeline is handled -- until a replay or backfill needs to recompute latestOrderId for an old SUBSCRIPTION_RENEWED notification, which is unknowable after the fact, because Play's own API only ever returns the subscription's current state, never a renewal history.

Why this one is easy to get wrong

Treating every recurring-billing event the same way (accumulate a count, snapshot a status) is the uniform, easy-to-generalize design, and nothing about Play's notification shape hints that its underlying API is fundamentally different from Stripe's invoice history -- the gap only shows up when a replay tries to reconstruct a value the provider's API was never built to hand back.

What you get instead

D6 models Play entitlement the way Google's own API actually supports it: a snapshot driven by expiryTime and subscriptionState, with no accumulate handler for renewals at all. The general rule this instantiates is stated directly: enrich plus snapshot is safe, enrich plus accumulate is not, because an enriched payload always reflects the present moment, never the moment the original event described.

Source: ARCHITECTURE.md D6 — checkable in the pack you receive

How you actually use this

You don’t install a library or wire up an SDK. Your own coding agent builds the code in your project, and you keep it — no runtime dependency on us.

Step 1
Download and unzip
You get a folder: the docs that tell an agent what to build, a starting skeleton, and the test suite that decides when it's done.
Step 2
Open it in Claude Code or Cursor
Point your coding agent at the folder. Nothing to install, no account with us, no API key.
Step 3
Paste one prompt
The pack contains the exact prompt. Paste it as your first message and leave it alone — it works through the build itself, choosing a cheaper or stronger model per task.
Step 4
Run ./verify.sh
One command. It prints a pass or fail for every check. Green means the build is done — the same script we ran to produce the receipt on this page.

Typical build: about 40 minutes of your agent working, mostly unattended. Then you integrate the working module into your app the way you would any code you’d written yourself.

Why you can believe this

3 of 3 runs passed

We ran this pack from an empty folder 3 times and published exactly what happened — every check, the model, the token cost, the wall time. Not a testimonial, and not our opinion: the same verify.sh you run yourself. Read the full receipt →

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