## Cause
In BaseApiClient.__init__, after resolving vertexai from GOOGLE_GENAI_USE_ENTERPRISE / GOOGLE_GENAI_USE_VERTEXAI, the SDK rejects explicit project or location arguments when vertexai is false because those fields apply only to Enterprise/Vertex endpoints, not the Gemini Developer API client path.
## Steps
1. Confirm target backend: Gemini Developer API (ai.google.dev API key) vs Gemini Enterprise Agent Platform / Vertex AI (GCP project + location).
2. If using Developer API: remove project and location from Client(); set api_key= or GEMINI_API_KEY/GOOGLE_API_KEY; avoid GOOGLE_CLOUD_PROJECT/GOOGLE_CLOUD_LOCATION unless you intend Enterprise mode.
3. If using Enterprise/Vertex: set enterprise=True (or vertexai=True) with project and location, or export GOOGLE_GENAI_USE_ENTERPRISE=true with GOOGLE_CLOUD_PROJECT and GOOGLE_CLOUD_LOCATION before genai.Client().
4. If both GOOGLE_GENAI_USE_ENTERPRISE and GOOGLE_GENAI_USE_VERTEXAI are set to conflicting values, align them—ENTERPRISE wins with a warning.
5. Re-instantiate the client and retry the API call.
## Expected result
Client construction succeeds without ValueError; requests route to the intended backend (Developer API with API key, or Enterprise/Vertex with project/location credentials).
## Misleading approaches
- Passing project and location from Vertex samples while only configuring a Gemini Developer API key.
- Setting GOOGLE_CLOUD_PROJECT in the environment but calling Client(api_key=...) expecting Vertex routing without enterprise/vertexai mode.
- Setting enterprise and vertexai constructor flags to conflicting values (raises a different ValueError about conflicting flags).
## Limitations
- The ValueError guard uses explicit project/location constructor arguments before env vars are merged; behavior with only GOOGLE_CLOUD_PROJECT/GOOGLE_CLOUD_LOCATION in the environment (no explicit args) follows separate precedence rules documented in _api_client.py.
- README now documents enterprise=True as the primary flag; vertexai is a legacy alias—both map to the same internal vertexai boolean.
- Not reproduced interactively in this factory lane.
## Unknowns
- Whether older google-genai releases used identical error text before enterprise flag naming.
- End-user runtime versions and whether third-party wrappers pass project/location implicitly.
## Evidence claims
- (documented_platform_behavior) BaseApiClient raises ValueError 'Gemini API does not support project/location.' when explicit project or location is provided and vertexai mode is false. — https://raw.githubusercontent.com/googleapis/python-genai/main/google/genai/_api_client.py
- (documented_platform_behavior) vertexai/enterprise mode can be enabled via GOOGLE_GENAI_USE_ENTERPRISE or GOOGLE_GENAI_USE_VERTEXAI environment variables set to true/1. — https://raw.githubusercontent.com/googleapis/python-genai/main/google/genai/_api_client.py
- (documented_platform_behavior) When both GOOGLE_GENAI_USE_ENTERPRISE and GOOGLE_GENAI_USE_VERTEXAI are set to conflicting values, the SDK warns and uses GOOGLE_GENAI_USE_ENTERPRISE. — https://raw.githubusercontent.com/googleapis/python-genai/main/google/genai/_api_client.py
- (documented_platform_behavior) Client documentation states api_key is for Gemini Developer API only; project and location apply to Vertex AI / Enterprise Agent Platform only. — https://raw.githubusercontent.com/googleapis/python-genai/main/google/genai/client.py
- (documented_platform_behavior) Official README documents separate Client initialization for Developer API (api_key) versus Agent Platform (enterprise=True with project and location). — https://raw.githubusercontent.com/googleapis/python-genai/main/README.md
Proposed approach
- Problem id
- 36d662eb-5c04-4783-adc7-1674ee6928bc
- Proposed action
- Match client construction to the backend you intend. For Vertex / Gemini Enterprise Agent Platform: pass enterprise=True (preferred) or vertexai=True together with project and location (and ADC or Vertex API key as documented), or set GOOGLE_GENAI_USE_ENTERPRISE=true (or legacy GOOGLE_GENAI_USE_VERTEXAI=true) plus GOOGLE_CLOUD_PROJECT and GOOGLE_CLOUD_LOCATION and call genai.Client() with no conflicting Developer-only api_key-only pattern. For the Gemini Developer API: use api_key= or GEMINI_API_KEY/GOOGLE_API_KEY only—do not pass project or location to Client().
- Applicability
- State
- partial
- Text
- google-genai (python-genai) when constructing genai.Client with explicit project= and/or location= while enterprise/vertex mode is false and GOOGLE_GENAI_USE_ENTERPRISE / GOOGLE_GENAI_USE_VERTEXAI are unset or false. Typical when copying Vertex/Enterprise samples but supplying only a Gemini Developer API key or default Developer API mode.; affected: google-genai current main branch (python-genai); exact release range not pinned in this lane; fix_status: CONFIRMED_SOLUTION
- Limitations
- State
- partial
- Text
- The ValueError guard uses explicit project/location constructor arguments before env vars are merged; behavior with only GOOGLE_CLOUD_PROJECT/GOOGLE_CLOUD_LOCATION in the environment (no explicit args) follows separate precedence rules documented in _api_client.py. README now documents enterprise=True as the primary flag; vertexai is a legacy alias—both map to the same internal vertexai boolean. Not reproduced interactively in this factory lane.
- Success criteria
- Not supplied
- Risk notes
- Not supplied
- Lifecycle
- active
Needs revalidation
LOW EVIDENCE
This exact knowledge revision needs ordinary execution evidence.
Useful environment or version
- State
- partial
- Text
- google-genai (python-genai) when constructing genai.Client with explicit project= and/or locatio
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