fix(vertexai): support timeout in ImageBytesLoader URL fetches#1826
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`ImageBytesLoader._bytes_from_url` in `langchain-google-vertexai` called `requests.get(url)` without a timeout, so a slow or stalled remote URL could block request preparation indefinitely. This mirrors the bug in `langchain-google-genai` that PR langchain-ai#1693 addresses with the same fix shape. - Add a `timeout` constructor argument to `ImageBytesLoader` (keyword-only, default `None` for backward compatibility) and use it in `_bytes_from_url` when set. - Add unit-test coverage for both paths (timeout reaches `requests.get`; default behavior calls `requests.get` without a `timeout` kwarg). Callers within the package (`vision_models`, `_anthropic_utils`, `utils`, `chat_models`) are not yet wired to pass a `timeout` through; that plumbing is intentionally out of scope here and matches the genai PR's approach of landing the loader-side change first.
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Description
`ImageBytesLoader._bytes_from_url` in `libs/vertexai/langchain_google_vertexai/_image_utils.py` calls `requests.get(url)` without a `timeout=`, so a slow or stalled remote URL can block request preparation indefinitely before any Vertex API call is issued. The user-visible symptom matches the genai-side bug fixed in #1693: an image URL in a message can hang the whole turn.
This PR adds a `timeout` constructor argument to `ImageBytesLoader` (keyword-only, default `None` for backward compatibility) and threads it into the `requests.get` call. The shape mirrors PR #1693 exactly so the two packages stay in step.
Caller plumbing (`vision_models`, `_anthropic_utils`, `utils`, `chat_models`) is intentionally not included — the genai PR landed the same staged approach (loader first, callers later). Existing call sites (`ImageBytesLoader(project=self.project)`) continue to work unchanged.
Relevant issues
The langchain-google-genai analog — same code path, same `requests.get(url)` without timeout — is tracked as #1692 and being fixed in PR #1693. No vertexai-specific issue was open at the time of writing; this PR closes the parallel gap so both packages share the API.
Type
🐛 Bug Fix
Changes
Testing
```
$ uv run pytest libs/vertexai/tests/unit_tests/test_image_utils.py -v
... 6 passed in 9.82s
```
Reverting only the `_image_utils.py` branch while keeping the new tests makes `test_image_bytes_loader_url_fetch_passes_timeout` fail (mock_get called without `timeout=2.5`), confirming the regression coverage pins the buggy behavior.
`ruff check` and `ruff format --check` pass on both files.
Note
`timeout` is keyword-only per the `CLAUDE.md` guidance for adding new public-API parameters. The existing positional `project` argument is preserved. No deps added.
Disclaimer: this PR was prepared with the assistance of an AI agent (Claude Code). All code and test changes were reviewed by the author before submission.