Gemini request plumbing duplicated: request() vs request_stream() build the same body in gemini_model.py, and gemini_code_assist.py forks _build_tools/_build_generation_config/_parse_response with real divergences

Severity: Medium (DRY; one divergence is a live bug)

1. Within gemini_model.py: request() and request_stream() duplicate body construction

GeminiModel.request() (gemini_model.py:522-560) and GeminiModel.request_stream() (612-649) each do the identical sequence — _map_messages → body = {"contents": ...} → conditionally attach generationConfig / systemInstruction / tools → _get_client() + url + _get_headers(). jscpd flags 528-544 ↔ 619-635 verbatim.

Divergence between the copies: only the streaming path adds toolConfig.functionCallingConfig (mode: AUTO, streamFunctionCallArguments: True). That may be intentional, but buried inside a 16-line clone it's indistinguishable from drift. Extract:

def _build_request_body(
    self,
    system_instruction, contents,
    model_settings, model_request_parameters,
    *, streaming: bool = False,
) -> dict[str, Any]: ...

so the intentional difference becomes one explicit if streaming: line and both endpoints share the rest.

2. Cross-file: gemini_code_assist.py re-implements the same helpers — and they've drifted into bugs

GeminiCodeAssistModel (gemini_code_assist.py) carries its own _build_tools (231-246), _build_generation_config (248-272), and _parse_response (274-310) that parallel GeminiModel's (gemini_model.py:466-482, 484-520, 561-610). The drift between copies is not cosmetic:

• _build_generation_config in code_assist is dead code. It probes hasattr(model_settings, "temperature") — but ModelSettings is a TypedDict (verified: hasattr(ModelSettings(temperature=0.5), "temperature") → False). So temperature/top_p/max_tokens are silently never sent for Code Assist models. The gemini_model.py copy correctly uses .get() and additionally handles thinking_level/thinkingConfig, which the fork lacks entirely.
• _parse_response drift: gemini_model.py handles ThinkingPart (+thoughtSignature), preserves the API-supplied tool-call id (fc.get("id") or generate_tool_call_id()), tolerates empty candidates, and records provider_response_id. The code_assist copy drops thinking parts, mints str(uuid.uuid4()) for every tool-call id, and raises RuntimeError("No candidates in response") where the other returns an empty TextPart.
• _build_tools drift: gemini_model.py sanitizes schemas via _sanitize_schema_for_gemini and emits key parameters; the fork emits parametersJsonSchema unsanitized — so any schema-compat fix made for vanilla Gemini silently doesn't apply to Code Assist.

Proposed extraction

A shared module (e.g. code_puppy/gemini_common.py) or a base class _GeminiWireFormat holding: _build_tools, _build_generation_config, _parse_candidate_parts (the per-part text/functionCall/thought loop + usageMetadata extraction), and _build_request_body. GeminiModel and GeminiCodeAssistModel keep only their genuine deltas: auth headers, endpoint URLs, the Code Assist {"model": ..., "project": ..., "request": ...} envelope/unwrap (data.get("response", data)), and the thoughtSignature injection on outgoing function calls.

Wire-format knowledge for one upstream API should live in exactly one place; today a Gemini API change means hunting through two files with three forked copies each.

(Related but distinct: #401 covers gemini_code_assist's StreamedResponse/model_name problems; #410 covers GeminiModel's client lifecycle. Neither covers this duplication.)

Filed by Zen Reviewer A (code-puppy-60635a) — DRY review round

Start by comparing the named helpers and request paths in gemini_model.py with _build_tools, _build_generation_config, and _parse_response in gemini_code_assist.py. Trace how request() and request_stream() build bodies, then evaluate a shared wire-format layer while preserving the streaming flag, Code Assist envelope, authentication, and endpoint differences. Done means the duplicated helpers and listed behavioral divergences are consolidated without changing those genuine model-specific deltas.