fix: make Transaction.to nullable for contract-creation txs

[rickstaa]

Problem

Contract-creation transactions (e.g. a Tenderize unlock deployed via its constructor) have no recipient, so event.transaction.to is null. Transaction.to was String!, so createOrLoadTransactionFromEvent left it unset and graph-node aborted with missing value for non-nullable field 'to' — deterministically halting the subgraph. First hit 2026-07-18 at block 485100965. See #243.

Fix

Make Transaction.to nullable: String! → String. A creation tx genuinely has no recipient, so null is the correct value — it matches Ethereum/JSON-RPC and graph-ts itself (to: Address | null). No mapping change is needed: the existing conditional assignment already leaves to null for creation txs. Only Transaction.to changes; MintEvent.to stays non-null (it's an event parameter, always present).

Alternative: default to the zero address (#244)

You can instead default to to the zero address (EMPTY_ADDRESS), which avoids the schema change. We prefer nullable because the zero address is less accurate: it reuses a real, valid address (0x0, the burn address) as a stand-in for "no recipient," so a consumer can't distinguish a contract-creation tx from an actual transfer to 0x0. null states what is true.

Testing

yarn codegen and yarn build pass. The Livepeer Explorer does not read Transaction.to, so the nullable change is safe for it.

Deployment

Redeploys with a full resync (grafting is disabled). Republish so subgraph FE63… points at the fixed deployment.

Fixes #243

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Review details

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro

Run ID: baa5d501-c941-4787-9dcf-3e38af36b093

📥 Commits

Reviewing files that changed from the base of the PR and between 4ddaf42 and a9f84af.

📒 Files selected for processing (1)

• schema.graphql

📝 Walkthrough

Walkthrough

The GraphQL Transaction.to field changes from non-nullable String! to nullable String, allowing transactions without recipient addresses to be represented as null.

Changes

Transaction recipient nullability

Layer / File(s)	Summary
Relax Transaction.to nullability schema.graphql	Changes Transaction.to from String! to String while retaining its documentation.

Estimated code review effort: 1 (Trivial) | ~5 minutes

Possibly related PRs

• livepeer/subgraph#244: Updates transaction creation logic to use EMPTY_ADDRESS when the event recipient is null.

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Linked Issues check	✅ Passed	The PR addresses #243 by preventing contract-creation tx saves from failing on a missing to value, which restores indexing.
Out of Scope Changes check	✅ Passed	The changes are limited to the Transaction.to schema nullability needed for the reported indexing failure.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Title check	✅ Passed	The title accurately summarizes the main change: making Transaction.to nullable for contract-creation transactions.
Description check	✅ Passed	The description covers the problem, fix, issue reference, testing, and deployment context, and is mostly complete.

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch fix/transaction-to-nullable

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[github-actions]

🚀 Subgraph Studio preview deployed

Item	Details
Version label	pr-245-7d36a8d-29782918708
Query endpoint	https://api.studio.thegraph.com/query/31909/livepeer-ci/pr-245-7d36a8d-29782918708

curl -H 'Content-Type: application/json' \
  -d '{"query":"{ protocol(id: \"0\") { inflation } }"}' \
  https://api.studio.thegraph.com/query/31909/livepeer-ci/pr-245-7d36a8d-29782918708