refactor(grpc): reduce proto-change friction in the Go bindings

[slin1237]

Summary

Two small, targeted fixes that reduce the per-proto-change cost in the gRPC bindings — the recurring friction discussed around the #1747 reasoning-token change. No behavior change.

Changes

• Harden Go proto reconstruction. bindings/golang/src/proto_parse.rs listed every field of GenerateStreamChunk/GenerateComplete explicitly, so adding any field to the generate protos broke the Go binding's compile (this is why feat(grpc): add sglang reasoning token usage #1747 had to touch it). Use ..Default::default() for the fields the bindings don't surface, so new proto fields no longer require a change here.

• De-duplicate reasoning detection. The Go bindings reimplemented the gateway's thinking-toggle logic (should_mark_reasoning_started + extract_thinking_from_kwargs), which could drift. Expose the gateway helpers as pub and have the bindings call them — consistent with how the bindings already reuse smg::routers::grpc::utils::process_chat_messages. The helpers stay in the gateway (request-interpretation lives there); the tokenizer crate is untouched.

Verification

• cargo +nightly fmt --all clean
• cargo check --workspace --all-targets clean
• cargo clippy -p smg -p smg-golang --all-targets -- -D warnings clean
• cargo test -p smg --lib — 1092 passed, 0 failed

Summary by CodeRabbit

• Refactor
  • Centralized reasoning token detection logic for improved code reuse across the gateway and Go language bindings.
  • Simplified proto field initialization to rely on default values, reducing code maintenance overhead.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: ASSERTIVE

Plan: Pro

Run ID: d5df9ab6-d04c-414e-b80f-f97e6d5e8ae7

📥 Commits

Reviewing files that changed from the base of the PR and between 7cb64bf and e21a443.

📒 Files selected for processing (4)

• bindings/golang/src/proto_parse.rs
• bindings/golang/src/utils.rs
• model_gateway/src/routers/grpc/utils/mod.rs
• model_gateway/src/routers/grpc/utils/parsers.rs

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📝 Walkthrough

Walkthrough

Two gateway functions (should_mark_reasoning_started, extract_thinking_from_kwargs) are promoted from pub(crate) to pub and re-exported publicly. The Go bindings then import and call these shared helpers in chat_requires_reasoning, replacing inline logic. Proto struct builders in parse_chunk and parse_complete are updated to use ..Default::default().

Reasoning detection and proto initialization

Layer / File(s)	Summary
Promote reasoning helpers to public API model_gateway/src/routers/grpc/utils/parsers.rs, model_gateway/src/routers/grpc/utils/mod.rs	should_mark_reasoning_started and extract_thinking_from_kwargs are changed from pub(crate) to pub in parsers.rs, and mod.rs splits their re-exports into a separate pub use block with a comment noting they are intended for Go bindings.
Go bindings delegate to shared helpers and use ..Default::default() bindings/golang/src/utils.rs, bindings/golang/src/proto_parse.rs	chat_requires_reasoning removes its inline extraction and branching and instead calls should_mark_reasoning_started(extract_thinking_from_kwargs(...), tokenizer). Proto builders in parse_chunk and parse_complete replace explicit zero/None field initializations with ..Default::default() to avoid breakage when proto structs gain new fields.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~10 minutes

Possibly related PRs

• lightseekorg/smg#1031: Introduced the same extract_thinking_from_kwargs/should_mark_reasoning_started helpers for reasoning parser state overriding, which this PR now exposes publicly.
• lightseekorg/smg#1747: Added the require_reasoning and reasoning_tokens proto fields across the gRPC stack that the Go bindings proto-parse changes here directly relate to.

Suggested labels

grpc, model-gateway

Suggested reviewers

• key4ng

Poem

🐇 Hop, hop! The helpers now shine in the light,
No more inline logic tucked out of sight.
pub is the word, shared across the crate,
Default::default() fills fields — isn't that great?
The bindings and gateway now speak the same tongue,
A tidy refactor, a new song sung! 🎵

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The PR title directly and accurately describes the main refactoring goal: reducing friction from proto changes in Go bindings through better use of defaults and shared utilities.
Docstring Coverage	✅ Passed	Docstring coverage is 100.00% which is sufficient. The required threshold is 80.00%.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch chore/grpc-bindings-proto-friction

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[gemini-code-assist]

Code Review

This pull request refactors the Go bindings and model gateway to reuse reasoning detection logic instead of duplicating it. Specifically, it exposes extract_thinking_from_kwargs and should_mark_reasoning_started as public functions from the gateway and imports them in the Go bindings. Additionally, it updates protobuf parsing in the Go bindings to use ..Default::default() to avoid future breakage when new fields are added. There are no review comments to address, and I have no additional feedback to provide.

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[claude]

👋 The PR description doesn't fully follow
PULL_REQUEST_TEMPLATE.md:

• Missing header: ## Description
• Missing header: ### Problem
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• Missing header: ## Test Plan

Please update the PR description so reviewers have the context they need.

[claude]

Clean refactoring — no issues found. The ..Default::default() change is idiomatic and eliminates the proto-field maintenance burden. The visibility promotion to pub follows the existing pattern used by process_chat_messages and create_stop_decoder, and the de-duplicated reasoning detection keeps the two code paths in sync.