docs: backfill docstrings on public backend/app API

[div0rce]

Milestone

Standalone documentation-quality PR (not a roadmap milestone) — public-API docstring backfill

Summary

CodeRabbit's "Docstring Coverage" pre-merge check measures repo-wide production docstring coverage (it was ~65–75%, threshold 80%). This documents every remaining public production definition in backend/app that lacked a docstring — closing the real gaps the check flags, in line with CLAUDE.md's house rule ("docstrings on public functions"). It is docstring-only: no behaviour, signature, or logic change.

Together with PR #18 (which documents eval/), the repository's entire public production API is documented (0 public-API gaps). Private helpers remain undocumented by the same CLAUDE.md convention.

What changed (22 public definitions documented)

• Provider impls: FakeEmbedder.dim/embed, OpenAIEmbedder.dim/embed, GeminiEmbedder.dim, ClaudeClient.model_name/complete, FakeLLM.complete, GeminiClient.model_name (the base Protocols carry the full contract; these get concise impl-level docstrings).
• CLI / middleware: ingest.main, RequestIdMiddleware.dispatch.
• Repositories: chunks.get, extractions.get, workflow_items.get.
• Router response models (Pydantic): VolumeResponse, CategoryPoint, CategoryResponse, ConfidenceResponse, SlaResponse, KpiResponse, ReviewQueueResponse, ReviewDecisionResponse.

Definition of Done

• make check passes — 222 backend pytest, 7 frontend Vitest + build, ruff/ruff-format/mypy clean
• Zero public-API docstring gaps remaining in backend/app
• Docstring-only — no behaviour change; no test outcomes affected
• Private helpers intentionally left undocumented per CLAUDE.md

Notes

• Scoped to backend/app and kept separate from the eval refactor (refactor(eval): restructure harness to Code Health 10.0 #18) for clean, reviewable diffs.
• This is the honest path to higher docstring coverage — real documentation of public API, not threshold-lowering or padding intentionally-private/test functions.

[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: 3297ce15-33cb-490b-b5a1-615cb07e346e

📥 Commits

Reviewing files that changed from the base of the PR and between 8fc2eac and 6d7678a.

📒 Files selected for processing (13)

• backend/app/embeddings/fake.py
• backend/app/embeddings/gemini_provider.py
• backend/app/embeddings/openai_provider.py
• backend/app/ingest.py
• backend/app/llm/claude.py
• backend/app/llm/fake.py
• backend/app/llm/gemini.py
• backend/app/observability.py
• backend/app/repositories/chunks.py
• backend/app/repositories/extractions.py
• backend/app/repositories/workflow_items.py
• backend/app/routers/dashboard.py
• backend/app/routers/review.py

📜 Recent review details

🧰 Additional context used

📓 Path-based instructions (4)

**/*.py

📄 CodeRabbit inference engine (CLAUDE.md)

**/*.py: Use type hints everywhere; mypy must pass cleanly with no errors
Write docstrings on public functions; comments should explain why, not what
Use ruff for linting and formatting in Python; maintain ruff check and ruff format --check compliance

Files:

• backend/app/embeddings/gemini_provider.py
• backend/app/observability.py
• backend/app/llm/claude.py
• backend/app/routers/review.py
• backend/app/ingest.py
• backend/app/repositories/chunks.py
• backend/app/llm/fake.py
• backend/app/repositories/workflow_items.py
• backend/app/embeddings/openai_provider.py
• backend/app/repositories/extractions.py
• backend/app/embeddings/fake.py
• backend/app/routers/dashboard.py
• backend/app/llm/gemini.py

backend/app/**/*.py

📄 CodeRabbit inference engine (CLAUDE.md)

Use Pydantic models for all I/O boundaries in the FastAPI backend

Files:

• backend/app/embeddings/gemini_provider.py
• backend/app/observability.py
• backend/app/llm/claude.py
• backend/app/routers/review.py
• backend/app/ingest.py
• backend/app/repositories/chunks.py
• backend/app/llm/fake.py
• backend/app/repositories/workflow_items.py
• backend/app/embeddings/openai_provider.py
• backend/app/repositories/extractions.py
• backend/app/embeddings/fake.py
• backend/app/routers/dashboard.py
• backend/app/llm/gemini.py

backend/app/embeddings/**/*.py

📄 CodeRabbit inference engine (CLAUDE.md)

Support swappable embeddings providers (text-embedding-3-small, gemini-embedding-2, or voyage-3-lite) via EMBEDDINGS_PROVIDER environment variable

Files:

• backend/app/embeddings/gemini_provider.py
• backend/app/embeddings/openai_provider.py
• backend/app/embeddings/fake.py

backend/app/llm/**/*.py

📄 CodeRabbit inference engine (CLAUDE.md)

backend/app/llm/**/*.py: Implement LLM provider abstraction in backend/app/llm/ and embeddings provider abstraction in backend/app/embeddings/ to keep both swappable and mockable for tests
Support swappable LLM providers (Anthropic Claude or Google Gemini) via LLM_PROVIDER environment variable

Files:

• backend/app/llm/claude.py
• backend/app/llm/fake.py
• backend/app/llm/gemini.py

🔇 Additional comments (13)

backend/app/embeddings/fake.py (1)

33-33: LGTM!

Also applies to: 37-37

backend/app/embeddings/gemini_provider.py (1)

63-63: LGTM!

backend/app/embeddings/openai_provider.py (1)

46-46: LGTM!

Also applies to: 50-51

backend/app/llm/fake.py (1)

38-39: LGTM!

backend/app/observability.py (1)

100-101: LGTM!

backend/app/ingest.py (1)

197-198: LGTM!

backend/app/llm/claude.py (1)

44-44: LGTM!

Also applies to: 55-55

backend/app/llm/gemini.py (1)

49-49: LGTM!

backend/app/repositories/chunks.py (1)

59-59: LGTM!

backend/app/repositories/extractions.py (1)

38-38: LGTM!

backend/app/repositories/workflow_items.py (1)

73-73: LGTM!

backend/app/routers/dashboard.py (1)

37-38: LGTM!

Also applies to: 44-45, 51-52, 68-69, 82-83, 109-110

backend/app/routers/review.py (1)

42-43: LGTM!

Also applies to: 55-56

---

📝 Walkthrough

Walkthrough

Docstrings and inline documentation are added across backend embeddings, LLM client providers, repository data access helpers, API response schemas, and infrastructure modules. No functional logic, API signatures, or validation constraints changed—only behavioral documentation clarifying return semantics, endpoint behavior, and contract descriptions.

Changes

Backend Documentation Updates

Layer / File(s)	Summary
Embeddings provider documentation backend/app/embeddings/fake.py, backend/app/embeddings/gemini_provider.py, backend/app/embeddings/openai_provider.py	dim property and embed method docstrings added across all embeddings providers, clarifying output vector dimension semantics and embedding behavior including endpoint details, ordering preservation, and vector validation.
LLM client documentation backend/app/llm/claude.py, backend/app/llm/fake.py, backend/app/llm/gemini.py	model_name property and complete method docstrings added to ClaudeClient, FakeLLM, and GeminiClient, describing model identifiers, endpoint routing (Anthropic/Gemini), and deterministic response construction for testing.
Repository helper documentation backend/app/repositories/chunks.py, backend/app/repositories/extractions.py, backend/app/repositories/workflow_items.py	get(session, id) method docstrings added to each repository module clarifying return of the requested entity or None when the record does not exist.
API response schema documentation backend/app/routers/dashboard.py, backend/app/routers/review.py	Docstrings added to dashboard response models (VolumeResponse, CategoryResponse, ConfidenceResponse, SlaResponse, KpiResponse) and review response models (ReviewQueueResponse, ReviewDecisionResponse), describing response shape and payload semantics.
Infrastructure and entry point documentation backend/app/observability.py, backend/app/ingest.py	Docstring added to RequestIdMiddleware.dispatch describing request ID assignment, structlog binding, and response echo behavior; docstring added to ingest main() describing its role as the seed/ingest command entry point.

🎯 1 (Trivial) | ⏱️ ~3 minutes

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly and concisely describes the main change: adding docstrings to public API definitions in the backend/app module.
Description check	✅ Passed	The description comprehensively covers all required template sections: Milestone, Summary (4 sentences), Definition of Done (with all items checked), and Notes explaining scope and strategy.
Docstring Coverage	✅ Passed	Docstring coverage is 94.12% 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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[div0rce]

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