Wire serde_2026 serialization into chia_rs

[richardkiss]

Summary

Wire the serde_2026 serialization format into chia_rs as a foundation for the post-HF2 INTERNED_GENERATOR cost model. This PR ships the producer/consumer surface only — nothing here changes consensus behavior until #1438 wires it into validation.

Depends on clvmr ≥ 0.18.0 (serde_2026 shipped to crates.io in June), which main already uses — no Cargo.toml changes.

Changes

• chia_consensus::serde_2026::node_from_bytes_auto: deserialize CLVM bytes, auto-detecting classic / backrefs / serde_2026 by magic prefix. Callers supply the max blob size; the per-atom cap (1 MiB) is fixed. Accepts non-minimal encodings (strict = false) — rationale documented inline: post-HF2, identity and cost come from the interned tree, so overlong varints only hurt their sender.
• chia_consensus::serde_2026::max_canonical_blob_size(max_cost, cost_per_byte): the provable upper bound on the canonical serde_2026 wire size of any within-cost generator (max_cost / cost_per_byte + 5 + prefix). The proof is in its doc comment; at mainnet constants the bound is 916,677 bytes. This is what callers should derive the node_from_bytes_auto size cap from — the limit is a property of the cost constants, not a hardcoded number. How much headroom to allow for non-minimal encodings is caller policy (input welcome).
• solution_generator_2026(): builds a generator using serialize_2026, at a named SERDE_2026_COMPRESSION_LEVEL (level 0; levels are producer-side only, all decodable by the one deserializer).
• Python bindings: solution_generator_2026() and SERDE_2026_MAGIC_PREFIX, stub generator updated.

Tests

• Unit tests for auto-dispatch (all three formats), size-cap boundary, and solution_generator_2026 round-trip through node_from_bytes_auto.
• The size bound is tested at its adversarial tight shapes (max-length atom — exactly tight, slack 0; >63 distinct atom lengths; >4096 unique pairs; doubling DAG) and shown general across arbitrary cost constants, from (0, 7) to (u64::MAX, u64::MAX) — not just mainnet's 11e9 / 12,000.
• New fuzz target serde-2026-size-bound: arbitrary trees and arbitrary cost constants per run; asserts the encoding bound, the derived cap for affordable trees, and round-trip identity. A deterministic seed generator (gen_serde_2026_fuzz_seeds example) produces corpus entries at 0.98–0.999 of the bound so mutation starts at the boundary. Fuzzing already earned its keep: it caught an integer overflow in the bound function at extreme constants (fixed with saturation).

Depends on

#1436 (InternedBlockBuilder) — merged; this PR is based on current main.

Follow-up (#1438 / FullBlock #1456)

Arvid's merged FullBlock format (#1456) adds v1 blocks that store the generator as a raw length-prefixed Vec<u8> (transactions_generator_buffer), giving a place to inspect bytes for SERDE_2026_MAGIC_PREFIX before HF2 and reject serde_2026 generators while INTERNED_GENERATOR is inactive — without parsing CLVM first. This PR does not wire that guard; #1438 adds check_generator_quote / consensus-path checks, applying the prefix check to both legacy Program bytes and the v1 raw buffer path.

Test plan

• fmt / clippy / full test suite pass locally
• from chia_rs import solution_generator_2026, SERDE_2026_MAGIC_PREFIX works
• solution_generator_2026(...) output starts with SERDE_2026_MAGIC_PREFIX (unit-tested)
• Fuzz target: ~750k executions clean
• CI green on current head

---

Note

Medium Risk
New deserialization and provable size-bound logic touch generator wire format and pre-charge decoding limits; behavior is not yet on the consensus path but mistakes here would matter for the HF2 follow-up.

Overview
Adds serde_2026 as a producer/consumer surface ahead of post-HF2 interned-generator work, without changing live consensus validation in this PR.

New chia_consensus::serde_2026 exposes node_from_bytes_auto (magic-prefix dispatch to classic/backrefs/serde_2026 with caller-supplied max_blob_size, non-minimal encodings allowed via strict = false), max_canonical_blob_size (cost-derived wire cap, ~916 677 bytes at mainnet constants), and SERDE_2026_COMPRESSION_LEVEL. solution_generator_2026 builds generators with serialize_2026.

Python chia_rs gains solution_generator_2026 and SERDE_2026_MAGIC_PREFIX (stubs updated). Coverage includes unit tests on tight encoding shapes and format dispatch, a serde-2026-size-bound fuzz target, and gen_serde_2026_fuzz_seeds to seed near-bound corpora.

^{Reviewed by Cursor Bugbot for commit 2cd665e. Bugbot is set up for automated code reviews on this repo. Configure here.}

[Copilot]

Pull request overview

This PR wires the new serde_2026 serialization format into chia_rs/chia-consensus to support upcoming post-HF2 INTERNED_GENERATOR work, including a new generator serializer and Python-facing APIs/constants.

Changes:

• Add solution_generator_2026() (Rust + Python binding) that serializes generators via serialize_2026.
• Introduce chia_consensus::serde_2026::node_from_bytes_auto() with consensus-oriented caps and a program_bytes re-export for downstream consumers.
• Pin clvmr to a specific git revision (via [patch.crates-io]) to access the new serde_2026 functionality, and expose SERDE_2026_MAGIC_PREFIX to Python.

Reviewed changes

Copilot reviewed 8 out of 9 changed files in this pull request and generated 4 comments.

Show a summary per file

File	Description
wheel/src/api.rs	Adds Python binding for solution_generator_2026() and exports SERDE_2026_MAGIC_PREFIX.
wheel/python/chia_rs/chia_rs.pyi	Updates Python type stubs for the new function and magic-prefix constant.
wheel/generate_type_stubs.py	Updates stub generator to include the new solution_generator_2026() function.
crates/chia-consensus/src/solution_generator.rs	Adds Rust solution_generator_2026() using serialize_2026.
crates/chia-consensus/src/serde_2026.rs	Adds consensus-tuned auto-deserializer dispatching between classic/backrefs/serde_2026.
crates/chia-consensus/src/program_bytes.rs	Re-exports node_from_bytes_auto() for easier cross-crate consumption.
crates/chia-consensus/src/lib.rs	Exposes the new program_bytes and serde_2026 modules.
Cargo.toml	Adds a [patch.crates-io] pin for clvmr to the serde_2026 git revision.
Cargo.lock	Reflects clvmr being sourced from the pinned git revision.

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.

[coveralls-official]

Coverage Report for CI Build 29473136351

Coverage decreased (-0.08%) to 81.815%

Details

• Coverage decreased (-0.08%) from the base build.
• Patch coverage: 51 uncovered changes across 2 files (141 of 192 lines covered, 73.44%).
• No coverage regressions found.

Uncovered Changes

File	Changed	Covered	%
crates/chia-consensus/examples/gen_serde_2026_fuzz_seeds.rs	43	0	0.0%
wheel/src/api.rs	11	3	27.27%
Total (4 files)	192	141	73.44%

Coverage Regressions

No coverage regressions found.

---

Coverage Stats

Relevant Lines:	19884
Covered Lines:	16268
Line Coverage:	81.81%
Coverage Strength:	11726295.61 hits per line

---

💛 - Coveralls

[cursor]

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

^{❌ Bugbot Autofix is OFF. To automatically fix reported issues with cloud agents, enable autofix in the Cursor dashboard.}

Want reviews to match your repository better? Bugbot Learning can learn team-specific rules from PR activity. A team admin can enable Learning in the Cursor dashboard.

^{Reviewed by Cursor Bugbot for commit 1d716da. Configure here.}