[CHIA-3823] Add INTERNED_GENERATOR consensus path + serde_2026 prefix guard

[richardkiss]

Summary

Implement the INTERNED_GENERATOR consensus path in run_block_generator2.

We also tweak check_generator_quote to skip checking serde_2026-serialized generators because it's more difficult to tell if they start with a q. We still check in check_generator_node.

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Note

High Risk
This is consensus-critical generator serialization and validation; a mismatch with network rules would fork or reject valid blocks.

Overview
With INTERNED_GENERATOR, block generators are serde_2026-only: InternedBlockBuilder::finalize now writes serialize_2026 instead of backrefs, and run_block_generator2 / trusted-block coinspend helpers decode via node_from_bytes_2026 with a max_canonical_blob_size cap, then charge byte cost from the interned tree instead of raw wire length.

check_generator_quote no longer inspects the [0xff, 0x01] prefix when the interned flag is set (serde_2026 bytes are not quote-shaped on the wire); simple-generator “quoted” shape is still enforced in check_generator_node after decode. Pre-fork behavior is unchanged: serde_2026 blobs fail parse or quote checks without the flag, and classic generators fail once INTERNED_GENERATOR is on.

Adds node_from_bytes_2026 in serde_2026, fuzz round-trip coverage with INTERNED_GENERATOR, and unit tests for cross-encoding acceptance/rejection.

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[Copilot]

Pull request overview

This PR updates consensus-critical generator validation/execution to support the post-HF2 INTERNED_GENERATOR path and adds an explicit pre-activation guard rejecting serde_2026-prefixed generators unless INTERNED_GENERATOR is enabled. It also introduces a dedicated validation error code for invalid generator encoding and adds unit tests covering the relevant flag/prefix combinations.

Changes:

• Add InvalidTransactionsGeneratorEncoding (mapped to error code 150) and use it to explicitly reject serde_2026 generators before INTERNED_GENERATOR activation.
• Implement the INTERNED_GENERATOR execution path in run_block_generator2 by deserializing via node_from_bytes_auto, interning the tree, and computing base cost via total_cost_from_tree.
• Switch trusted-block generator parsing to node_from_bytes_auto and add targeted tests for check_generator_quote / check_generator_node.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
crates/chia-consensus/src/validation_error.rs	Adds a new consensus error code for invalid transactions generator encoding and maps it to numeric code 150.
crates/chia-consensus/src/run_block_generator.rs	Adds serde_2026 prefix guarding, implements INTERNED_GENERATOR handling in run_block_generator2, updates trusted parsing to auto-detect serialization, and adds tests.

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[coveralls-official]

Coverage Report for CI Build 30489236762

Coverage increased (+0.08%) to 81.894%

Details

• Coverage increased (+0.08%) from the base build.
• Patch coverage: 7 uncovered changes across 2 files (123 of 130 lines covered, 94.62%).
• No coverage regressions found.

Uncovered Changes

File	Changed	Covered	%
crates/chia-consensus/src/run_block_generator.rs	119	113	94.96%
crates/chia-consensus/src/serde_2026.rs	10	9	90.0%
Total (3 files)	130	123	94.62%

Coverage Regressions

No coverage regressions found.

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Coverage Stats

Relevant Lines:	20010
Covered Lines:	16387
Line Coverage:	81.89%
Coverage Strength:	11650890.35 hits per line

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💛 - Coveralls

[arvidn]

the SIMPLE_GENERATOR flag was part of the 2.7.0 soft fork, and has activated. Since we used generator programs in the initial version of block compression we can't require simple generators throughout the whole chain, so we still need this flag to validate early blocks.

We don't need to support (and maybe even should fail) the combination INTERNED_GENERATOR set and SIMPLE_GENERATOR not set. If there's any opportunity to simplify anything.

One crazy idea is that the interned serialization could have an implicit quote around the whole expression.

[richardkiss]

the SIMPLE_GENERATOR flag was part of the 2.7.0 soft fork, and has activated. Since we used generator programs in the initial version of block compression we can't require simple generators throughout the whole chain, so we still need this flag to validate early blocks.

We don't need to support (and maybe even should fail) the combination INTERNED_GENERATOR set and SIMPLE_GENERATOR not set. If there's any opportunity to simplify anything.

One crazy idea is that the interned serialization could have an implicit quote around the whole expression.

We discussed this with Bram on the weekly architecture call a while back and he agreed to dropping the (q . X) wrapper — writing just X and so not running it at all, so the block is no longer a generator but carries a list of spends.

I'd propose that as a separate change on top of this one: it deletes the quote checks for this path entirely and changes what the generator tree hash commits to, so it touches the builders too. At the same time we could rename the flag to something like SERDE_2026_TX_LIST since it's no longer a generator, and the interning is just how the cost is computed.

Or I can do it all in this change if you prefer, since the interaction is a bit intricate. Let me know.

I can make INTERNED_GENERATOR without SIMPLE_GENERATOR a hard failure in this PR.

[cursor]

Cursor Bugbot has reviewed your changes and found 1 potential issue.

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