starknet_os_runner: add stwo_proving feature gates and compile-safe fallbacks

[avi-starkware]

Summary

• Add stwo_proving Cargo feature gating the proving and server modules behind nightly-only stwo deps.
• Provide a fallback main() that exits with a message when stwo_proving is disabled.
• cfg-gate ProvingError::ProverExecution, related server error handling, and proving imports in virtual_snos_prover.rs.

Stack: 2/4 — reviewable wiring PR; no core proving logic yet, just feature boundaries and error plumbing.

Depends on: #12707

Test plan

• cargo test -p starknet_os_runner (default features, no stwo_proving)
• cargo clippy -p starknet_os_runner --all-targets

🤖 Generated with Claude Code

---

Note

Medium Risk
Introduces feature-flagged code paths that change build/run behavior for starknet_os_runner and alters CI clippy invocation; risk is mainly around conditional compilation and ensuring stable vs nightly builds/tests behave as intended.

Overview
Adds a new stwo_proving Cargo feature to isolate nightly-only in-memory STWO proving support, and conditionally compiles proving/server integration so starknet_os_runner can still build on stable without those deps.

When stwo_proving is disabled, the binary now exits immediately with a clear message, while proving-related error variants, RPC error mapping, and virtual_snos_prover proving entry points are cfg-gated (including unimplemented! fallbacks where proving would run). CI tooling (scripts/run_tests.py) is updated so stable cargo clippy --all-features excludes nightly-feature packages and runs those packages in a separate, feature-limited clippy pass.

^{Written by Cursor Bugbot for commit 5e2331b. This will update automatically on new commits. Configure here.}

[reviewable-StarkWare]

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[cursor]

Cursor Bugbot has reviewed your changes and found 2 potential issues.

[AvivYossef-starkware]

@AvivYossef-starkware reviewed 16 files and all commit messages, and made 5 comments.
Reviewable status: all files reviewed, 3 unresolved discussions (waiting on avi-starkware and Yoni-Starkware).

---

-- commits line 21 at r7:
I`d delete it, one day they'll claim that they own the code

Code quote:

  Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

---

crates/starknet_os_runner/src/main.rs line 5 at r7 (raw file):

#[cfg(not(feature = "stwo_proving"))]
fn main() {
    eprintln!("This binary requires the `stwo_proving` feature.");

Suggestion:

starknet_os_unner

---

crates/starknet_os_runner/src/proving/virtual_snos_prover.rs line 194 at r7 (raw file):

            Ok(VirtualSnosProverOutput { result, os_duration, prove_duration, total_duration })
        }
    }

cant you put in in the same block of

#[cfg(feature = "stwo_proving")]
        let (result, prove_duration) = {
            let prove_start = Instant::now();
            let result = prove_virtual_snos_run(runner_output).await?;
            let prove_duration = prove_start.elapsed();

            info!(
                prove_duration_ms = %prove_duration.as_millis(),
                "Proving completed"
            );
            (result, prove_duration)
        };

?

Code quote:

        #[cfg(feature = "stwo_proving")]
        {
            let total_duration = start_time.elapsed();
            info!(total_duration_ms = %total_duration.as_millis(), "prove_transaction completed");
            Ok(VirtualSnosProverOutput { result, os_duration, prove_duration, total_duration })
        }
    }

---

crates/starknet_os_runner/src/running/classes_provider.rs line 29 at r7 (raw file):

/// - `compiler_version`: Set to empty string
/// - `pythonic_hints`: Set to None
#[allow(dead_code)]

what has changed?

Code quote:

#[allow(dead_code)]

---

scripts/run_tests.py line 69 at r7 (raw file):

                cmds.append(["cargo", "clippy"] + args + ["--all-targets", "--all-features"])
            for p in nightly_crates:
                cmds.append(["cargo", "clippy", "--package", p, "--all-targets"])

Don't you want to check it with the feature?

Code quote:

cmds.append(["cargo", "clippy", "--package", p, "--all-targets"])

[avi-starkware]

@avi-starkware made 3 comments.
Reviewable status: all files reviewed, 3 unresolved discussions (waiting on AvivYossef-starkware and Yoni-Starkware).

---

-- commits line 21 at r7:

Previously, AvivYossef-starkware wrote…

I`d delete it, one day they'll claim that they own the code

I doubt they will make that claim, but I don't mind removing it.

If they ever make that claim people will stop using their products...
They just put it here for marketing

---

crates/starknet_os_runner/src/running/classes_provider.rs line 29 at r7 (raw file):

Previously, AvivYossef-starkware wrote…

what has changed?

I just removed dead_code where it is not necessary. Earlier I added a bunch of dead_code proc macro because my feature gating covered more of the code. Now that I limited feature gating many dead_code proc macros can be removed. Turns out this one can also be removed.

---

scripts/run_tests.py line 69 at r7 (raw file):

Previously, AvivYossef-starkware wrote…

Don't you want to check it with the feature?

No
With the feature, it will fail. (Not in this PR, in the next one #12708)

We need a CI workflow that runs cargo with nightly.
I don't want to hardcode nightly-2025-07-14 here. It will be in a crate-level rust-toolchain.toml, and then running cargo after cd crates/starknet_os_runner will run with the correct nightly toolchain.

[avi-starkware]

@avi-starkware made 2 comments.
Reviewable status: 14 of 16 files reviewed, 3 unresolved discussions (waiting on AvivYossef-starkware and Yoni-Starkware).

---

crates/starknet_os_runner/src/proving/virtual_snos_prover.rs line 194 at r7 (raw file):

Previously, AvivYossef-starkware wrote…

cant you put in in the same block of

#[cfg(feature = "stwo_proving")]
        let (result, prove_duration) = {
            let prove_start = Instant::now();
            let result = prove_virtual_snos_run(runner_output).await?;
            let prove_duration = prove_start.elapsed();

            info!(
                prove_duration_ms = %prove_duration.as_millis(),
                "Proving completed"
            );
            (result, prove_duration)
        };

?

Done.

---

crates/starknet_os_runner/src/main.rs line 5 at r7 (raw file):

#[cfg(not(feature = "stwo_proving"))]
fn main() {
    eprintln!("This binary requires the `stwo_proving` feature.");

Done.

[AvivYossef-starkware]

@AvivYossef-starkware reviewed 2 files and all commit messages, made 1 comment, and resolved 2 discussions.
Reviewable status: all files reviewed, 1 unresolved discussion (waiting on avi-starkware and Yoni-Starkware).

---

scripts/run_tests.py line 69 at r7 (raw file):

Previously, avi-starkware (Avi Cohen) wrote…

No
With the feature, it will fail. (Not in this PR, in the next one #12708)

We need a CI workflow that runs cargo with nightly.
I don't want to hardcode nightly-2025-07-14 here. It will be in a crate-level rust-toolchain.toml, and then running cargo after cd crates/starknet_os_runner will run with the correct nightly toolchain.

Can you add a comment that explains it?

[avi-starkware]

scripts/run_tests.py line 69 at r7 (raw file):

Previously, AvivYossef-starkware wrote…

Can you add a comment that explains it?

There is a comment above the constant definition:

# Packages that have features requiring a nightly Rust toolchain.  These are excluded from the
# main CI clippy run (which uses --all-features on stable) and are instead checked by their own
# dedicated CI workflow with the appropriate toolchain.
NIGHTLY_FEATURES_PACKAGES: Set[str] = {"starknet_os_runner"}

Added another comment here.

[AvivYossef-starkware]

@AvivYossef-starkware reviewed 1 file and all commit messages, made 1 comment, and resolved 1 discussion.
Reviewable status: complete! all files reviewed, all discussions resolved (waiting on Yoni-Starkware).

[AvivYossef-starkware]

@AvivYossef-starkware reviewed all commit messages and made 1 comment.
Reviewable status: 15 of 16 files reviewed, all discussions resolved (waiting on Yoni-Starkware).

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scripts/run_tests.py line 61 at r10 (raw file):

            nightly_crates = (
                crates & NIGHTLY_FEATURES_PACKAGES if crates else NIGHTLY_FEATURES_PACKAGES
            )

Is it documented somewhere that a crate being empty means workspace-wide?

Code quote:

            nightly_crates = (
                crates & NIGHTLY_FEATURES_PACKAGES if crates else NIGHTLY_FEATURES_PACKAGES
            )

[AvivYossef-starkware]

@AvivYossef-starkware reviewed 1 file.
Reviewable status: complete! all files reviewed, all discussions resolved (waiting on Yoni-Starkware).