perf: adopt fat-LTO release profile and a release-fast test profile

.github/PULL_REQUEST_TEMPLATE.md

@@ -23,4 +23,4 @@
 
 - [ ] Ran `make fmt` — clean
 - [ ] Ran `make lint` (clippy with `-D warnings`) — clean
-- [ ] Ran `cargo test --workspace --release` — all passing
+- [ ] Ran `make test` (`cargo test --workspace --profile release-fast`) — all passing

CLAUDE.md

@@ -316,11 +316,17 @@ GENESIS_VALIDATORS:
 
 ### Running Tests
 ```bash
-cargo test --workspace --release                                    # All workspace tests
+cargo test --workspace --profile release-fast                       # All workspace tests
 cargo test -p ethlambda-blockchain --test forkchoice_spectests
 cargo test -p ethlambda-blockchain --test forkchoice_spectests -- --test-threads=1  # Sequential
 ```
 
+Tests run under `release-fast`: release-grade opt-level (needed to avoid stack
+overflows in signature verification/aggregation) but no LTO, parallel codegen,
+incremental, and line-tables-only debuginfo, so rebuilds are much faster than
+`--release`. Artifacts land in `target/release-fast/`, separate from
+`cargo build --release`.
+
 ## Common Gotchas
 
 ### Aggregator Flag Required for Finalization

Cargo.toml

@@ -26,6 +26,32 @@ repository = "https://github.com/lambdaclass/ethlambda"
 rust-version = "1.97.1"
 version = "0.1.0"
 
+# Cross-crate inlining matters here: the hot paths (SSZ encode/decode, hashing,
+# fork choice traversal) are split across workspace crates and their
+# dependencies, so keeping every crate in its own codegen unit leaves inlining
+# opportunities on the table. Fat LTO plus a single codegen unit trades build
+# time for that.
+#
+# Fat rather than thin: on an 8-node devnet, fat cut mean state transition time
+# a further 2.1% over thin (every fat node beat every thin node) at no measurable
+# build-time or image-size cost. ethrex uses thin here; we diverge deliberately.
+[profile.release]
+opt-level = 3
+lto = "fat"
+codegen-units = 1
+
+# Test profile (see the `test` target in the Makefile). Tests need release-grade
+# opt-level: signature verification/aggregation stack-overflows without it. They
+# do not need a whole-program-optimized binary, so this drops LTO, restores
+# parallel codegen, and keeps line tables for backtraces, which makes test
+# rebuilds finish in a fraction of the time of a `release` build.
+[profile.release-fast]
+inherits = "release"
+lto = false
+codegen-units = 16
+debug = "line-tables-only"
+incremental = true
+
 [workspace.dependencies]
 ethlambda-blockchain = { path = "crates/blockchain" }
 ethlambda-fork-choice = { path = "crates/blockchain/fork_choice" }

Makefile

@@ -10,8 +10,9 @@ lint: ## 🔍 Run clippy on all workspace crates
 	cargo clippy --workspace --all-targets -- -D warnings
 
 test: leanSpec/fixtures ## 🧪 Run all tests
-	# Tests need to be run on release to avoid stack overflows during signature verification/aggregation
-	cargo test --workspace --release
+	# release-fast: release-grade opt-level to avoid stack overflows during
+	# signature verification/aggregation, without paying for LTO on every rebuild
+	cargo test --workspace --profile release-fast
 
 GIT_COMMIT=$(shell git rev-parse HEAD)
 GIT_BRANCH=$(shell git rev-parse --abbrev-ref HEAD)