test(eval): add compression ratio gate

[KooshaPari]

Summary

• Add a feature-gated zstd fixture compression ratio test with a 65% threshold.
• Document the compression method, threshold policy, and rough token-burn proxy.
• Add a SHA-pinned CI workflow that runs the focused compression evaluation gate.

Test plan

• cargo fmt --all --check
• cargo test -p session-ledger --features compress --test compression_eval --locked

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Review details

⚙️ Run configuration

Configuration used: Organization UI

Review profile: ASSERTIVE

Plan: Pro

Run ID: ce68f858-7399-41e1-a787-c5d8a05205d1

📥 Commits

Reviewing files that changed from the base of the PR and between 002fe51 and cada6c9.

📒 Files selected for processing (3)

• .github/workflows/eval-compression.yml
• docs/ops/eval-compression.md
• tests/compression_eval.rs

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch feat/sl-w12-c08

✨ Simplify code

• Create PR with simplified code
• Commit simplified code in branch feat/sl-w12-c08

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[gemini-code-assist]

Code Review

This pull request introduces a compression evaluation gate, adding documentation and an integration test to verify that the zstd compression ratio of a representative OKF session remains below a specified threshold. Feedback on the integration test highlights a potential integer overflow on 32-bit architectures and a division-by-zero risk if the fixture is empty, suggesting the use of u64 casting and checked_div to perform the calculation safely.

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[gemini-code-assist]

On 32-bit architectures (such as certain WASM targets or 32-bit ARM/x86), usize is 32-bit. If the session fixture or compressed payload grows beyond ~430 KB, the multiplication compressed.len() * 10_000 will overflow u32::MAX, causing a panic during test execution. Additionally, if the fixture is ever empty, this will panic with a division-by-zero error.

Using u64 casting and checked_div prevents both overflow and division-by-zero issues safely.

    let ratio_bps = (compressed.len() as u64 * 10_000)
        .checked_div(FIXTURE.len() as u64)
        .expect("fixture must not be empty") as usize;

[kilo-code-bot]

SUGGESTION: Hardcoded MAX_RATIO_BPS gate is sensitive to zstd library version drift

The compressed byte count depends on the zstd version linked transitively by the zstd/zstd-sys crates. A routine dependency bump that changes zstd's output size at a fixed level can shift ratio_bps across the 6500 boundary and fail this CI gate even with no fixture or code change. Consider documenting this version-dependency in docs/ops/eval-compression.md alongside the existing fixture-change policy, or basing the assertion on a small tolerance band, so unrelated dependency bumps don't break the build.

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Reply with @kilocode-bot fix it to have Kilo Code address this issue.

[kilo-code-bot]

Code Review Summary

Status: 1 Issue Found | Recommendation: Merge with notes (non-blocking)

Overview

Severity	Count
CRITICAL	0
WARNING	0
SUGGESTION	1

Issue Details (click to expand)

SUGGESTION

File	Line	Issue
tests/compression_eval.rs	8	Hardcoded MAX_RATIO_BPS threshold is sensitive to zstd library version drift; an unrelated zstd/zstd-sys dependency bump can shift the ratio across the 6500 boundary and break CI.

Files Reviewed (3 files)

• .github/workflows/eval-compression.yml
• docs/ops/eval-compression.md
• tests/compression_eval.rs

Note: An existing active review comment on tests/compression_eval.rs:19 (32-bit usize overflow / division-by-zero on empty fixture) is already tracked and was not duplicated here.

Fix these issues in Kilo Cloud

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_{Reviewed by hy3:free · Input: 85.8K · Output: 9.1K · Cached: 105.2K}