[Copilot]

Four FFI output paths duplicate serialization and buffer-write handling while requiring distinct failure semantics: -1 for agent/resource labeling, 0 to skip response labeling.

• Shared helper: Route all four paths through serialize_and_write, with an explicit caller-selected error code.
• Preserved behavior: Retain response skip-labeling diagnostics and existing buffer validation.
• Regression coverage: Check serialization and undersized-buffer failures for each export path.

serialize_and_write(&output, output_ptr, output_size, "label_resource", -1)
serialize_and_write(&output, output_ptr, output_size, "label_response/path", 0)

• Fixes [rust-guard] Consolidate duplicated serialize-and-write blocks in FFI exports #15743

[Copilot]

🟢 Approval recommended

The Rust guard FFI serialization and output-handling refactor has no active review issues.

No open issues 🎉

What changed in this PR

Consolidates Rust guard FFI serialization and output handling into a shared helper, addressing #15743 while preserving each export’s failure behavior.

Changes:

• Routes all four output paths through serialize_and_write.
• Preserves -1 errors for agent/resource labeling, 0 skip results for response labeling, and existing buffer validation.
• Adds helper regression tests for serialization and undersized-buffer failures across all four caller configurations.

File	Description
guards/​github-guard/​rust-guard/​src/​lib.rs	Adds the shared helper, replaces duplicated output handling, and tests failure-code preservation.

_{Review effort: Balanced (auto)}

[lpcox]

@copilot merge main and resolve conflicts

[Copilot]

@copilot merge main and resolve conflicts

Merged main and resolved the conflict in rust-guard/src/lib.rs, preserving both test additions. Merge commit: 7fa1599.