docs(solana): document v0/v1 versioned transactions

docs/SUMMARY.md

@@ -50,6 +50,7 @@
     * Local Development
       * [Anchor](how-to-guides/develop-your-own-substreams/solana/local-development/anchor.md)
     * [From Yellowstone to Substreams](how-to-guides/develop-your-own-substreams/solana/migrate-from-yellowstone.md)
+    * [Versioned Transactions (v0 and v1)](how-to-guides/develop-your-own-substreams/solana/versioned-transactions.md)
   * [on Cosmos](how-to-guides/develop-your-own-substreams/cosmos)
     * [Injective](how-to-guides/develop-your-own-substreams/cosmos/injective)
       * [Simple Substreams Example](how-to-guides/develop-your-own-substreams/cosmos/injective/block-stats.md)

docs/how-to-guides/develop-your-own-substreams/solana/versioned-transactions.md

@@ -0,0 +1,57 @@
+# Versioned Transactions (v0 and v1)
+
+Solana introduced [versioned transactions](https://solana.com/docs/core/transactions/versioned-transactions) to let a transaction reference more accounts than fit in a legacy transaction, using [Address Lookup Tables (ALTs)](https://solana.com/news/transaction-v1-and-the-alt-trade-off). Legacy transactions and v0 transactions have been available for a while; v1 transactions are the newest addition.
+
+This page explains what changed on the Substreams side, and who needs to make a change to keep consuming this data.
+
+## What changed
+
+Solana blocks contain transactions tagged with a `version` and a `versioned` flag. A v1 transaction also carries a `transaction_config` field:
+
+```json
+{
+  "transaction_config": {
+    "compute_unit_limit": 1350000,
+    "heap_size": 256000,
+    "loaded_accounts_data_size_limit": 2162688
+  },
+  "version": 1,
+  "versioned": true
+}
+```
+
+A v0 transaction looks the same, minus `transaction_config`:
+
+```json
+{
+  "version": 0,
+  "versioned": true
+}
+```
+
+The Solana Firehose protobuf models expose these fields on `sf.solana.type.v1.Message`. See the [protobuf reference](https://buf.build/streamingfast/firehose-solana/docs/main%3Asf.solana.type.v1#sf.solana.type.v1.Message) for the full schema.
+
+## Do you need to change anything?
+
+For most Substreams users, no. Existing Substreams packages keep working against v0 and v1 transactions without any change, the same way they already work against legacy transactions.
+
+You only need to update your Substreams package if you want to read the new fields, for example to:
+
+- Inspect `transaction_config` (compute unit limit, heap size, loaded accounts data size limit).
+- Branch your logic on whether a transaction is legacy, v0, or v1.
+
+To do that:
+
+1. In your Rust module's `Cargo.toml`, bump the `substreams-solana` dependency to [v0.15.1](https://crates.io/crates/substreams-solana) or later, which decodes these fields.
+2. If your manifest vendors the `sf.solana.type.v1` proto files directly instead of relying on the crate, replace them with the versions linked in [Protobuf reference](https://buf.build/streamingfast/firehose-solana/docs/main%3Asf.solana.type.v1#sf.solana.type.v1.Message) and rerun `substreams protogen` (see [Protobuf](../generic/creating-protobuf-schemas.md)) to regenerate the Rust bindings.
+3. Rebuild your module and redeploy the resulting `.spkg`.
+
+{% hint style="info" %}
+If you consume Solana data through the Solana RPC API instead of Substreams, check the `maxSupportedTransactionVersion` parameter on your `getTransaction`, `getBlock`, or `blockSubscribe` requests. If it's unset or too low, the RPC call fails outright on a v1 transaction (for example, `getTransaction` returns error `-32015`, and one v1 transaction in a block fails the entire `getBlock` response) rather than silently omitting it.
+{% endhint %}
+
+## Related resources
+
+- [Solana: Versioned Transactions](https://solana.com/docs/core/transactions/versioned-transactions)
+- [Solana: Transaction v1 and the ALT trade-off](https://solana.com/news/transaction-v1-and-the-alt-trade-off)
+- [`sf.solana.type.v1.Message` protobuf reference](https://buf.build/streamingfast/firehose-solana/docs/main%3Asf.solana.type.v1#sf.solana.type.v1.Message)

docs/release-notes/change-log.md

@@ -25,6 +25,9 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 
 ### Docs
 
+- Add a Solana how-to on versioned transactions (v0 and v1): what the new `version`,
+  `versioned`, and `transaction_config` fields are, and when a Substreams package
+  needs to rebuild against `substreams-solana` v0.15.1+ to read them.
 - Document `Feed.Delete` on the Remote Feed Hosted Store guide: remote-feed clients can
   hard-delete a batch of keys over gRPC. Missing keys are ignored; later reads return
   `NOT_FOUND`, not a tombstone.