[Cedric921]

What

Unit tests for system_memory.available_bytes() and its readers, against recorded output:

• Linux reads MemAvailable, not MemFree, in kB, and falls back to the sysconf total when the line is missing (kernels before 3.14) or /proc/meminfo cannot be read.
• macOS counts free plus inactive pages at the page size vm_stat reports (16 KiB on Apple Silicon; assuming 4 KiB would read a quarter). It falls back to total when vm_stat fails or reports nothing reclaimable, never zero.
• An unknown platform reads the total.

No production code changes.

Why

docs/architecture/local-models/fit.md listed "system_memory.available_bytes() has no test" under Known gaps. That figure is what separates PARTIAL from TOO_BIG on a discrete card, and a wrong unit or page size would badge models wrongly without any error. The sentence is removed from the gap, and the Host memory section now points at the tests.

The other half of that line, Device.reports_live_memory never being read, is left as it is. Deciding what a budget should do with a device that restates its total is a design question, not a test, so it is not guessed at here.

Fixes

No issue. This narrows the Known gaps line in docs/architecture/local-models/fit.md.

How to test

cd surfsense_local/backend
uv run pytest tests/unit/llm/hardware -q
uv run ruff check tests/unit/llm/hardware
python ../../scripts/check_docs.py

7 new tests; tests/unit/llm/hardware: 55 passed, 7 skipped.

High-level PR Summary

This PR adds comprehensive unit tests for the system_memory.available_bytes() function and its platform-specific readers (Linux and macOS). The tests use recorded OS output to verify that the system correctly reads available memory from /proc/meminfo on Linux (using MemAvailable in kB) and vm_stat on macOS (counting free plus inactive pages at the reported page size), with appropriate fallbacks to total memory when these sources are unavailable. The changes include documentation updates to reference the new tests and remove a known gap item. No production code is modified.

⏱️ Estimated Review Time: 5-15 minutes

💡 Review Order Suggestion

Order	File Path
1	docs/architecture/local-models/fit.md
2	surfsense_local/backend/tests/unit/llm/hardware/test_system_memory.py

Summary by CodeRabbit

• Documentation
  • Clarified how available memory is reported across Linux, macOS, and Windows, including fallback behavior. Updated test-coverage references and the documented coverage gap.
• Tests
  • Added coverage for available-memory reporting and fallback behavior across supported and unknown platforms, including cases where system readings fail or are unavailable.

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📚 Code guidelines (1)

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ℹ️ Recent review info

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• Run ID: 36acf128-299a-4e66-8047-b48418743d7d

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Reviewing files that changed from the base of the PR and between 744e50f and aede598.

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• surfsense_local/backend/tests/unit/llm/hardware/test_system_memory.py

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📝 Walkthrough

Walkthrough

Adds tests for Linux, macOS, and Windows system-memory readers, total-memory calculation, and fallback behavior. Updates architecture documentation to describe platform memory sources and test coverage, and removes a statement that system_memory.available_bytes() lacked a test.

Changes

System memory reader coverage

Layer / File(s)	Summary
Platform memory reader tests and documentation surfsense_local/backend/tests/unit/llm/hardware/test_system_memory.py, docs/architecture/local-models/fit.md	Adds tests for Linux MemAvailable, macOS free and inactive pages, Windows available physical memory, total-memory calculation, and fallback paths. Updates the documentation to describe the platform memory sources and test coverage, and removes the statement that system_memory.available_bytes() has no test.

Priority: ⬇️ Low

Estimated code review effort: 2 (Simple) | ~10 minutes

Change: Other

Merge Risk: 🔵 Low · up to aede5

The guide overstates the Windows fallback: an API failure returns zero, which can limit context widening. This is a small documentation follow-up, not a production-code change.

🚥 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 title clearly describes the main change: adding tests for how the local system reads host memory from the OS.
Docstring Coverage	✅ Passed	Docstring coverage is 80.00% which is sufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 20 functions across 1 files.
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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[MODSetter]

Reviewed this. The Linux and macOS readers are tested well: /proc/meminfo and vm_stat are faked rather than read from the CI machine, the assertions catch reading MemFree, a lost ×1024 or the wrong page size, and both fallbacks are pinned. One thing before it can merge.

The Windows reader has no test, but the docs now say every reader does

_windows() (modules/llm/hardware/system_memory.py:58-65) runs in no test, and CI's desktop Backend job runs only on Linux. Yet fit.md:196 now says "Each reader and its fallbacks are tested", and the Known gaps sentence is deleted. On Windows _total() is 0, since there is no os.sysconf, so _windows() is the only thing that keeps the reading off 0.

What to change

• Add test_windows_reads_available_physical_memory and test_windows_reads_zero_when_the_call_fails: patch in a stand-in with monkeypatch.setattr(system_memory.ctypes, "windll", stand_in, raising=False), whose kernel32.GlobalMemoryStatusEx(ref) checks ref._obj.dwLength == ctypes.sizeof(ref._obj), sets ref._obj.ullAvailPhys = 6 * GIB and returns 1 (0 in the second test); assert _windows() returns 6 * GIB, then 0.
• In fit.md, name ullAvailPhys from GlobalMemoryStatusEx as the Windows reader, and say the tests use sample /proc/meminfo and vm_stat output and a stand-in GlobalMemoryStatusEx; the samples are hand-made, so "recorded" overstates them.

Not blocking: every test replaces _total(), so its sysconf calculation never runs, and only a missing vm_stat is tested, not a hung one (subprocess.SubprocessError).

Push the fix to this branch and it will be reviewed again.

[Cedric921]

Done in the latest push.

• Windows reader: I added test_windows_reads_available_physical_memory and test_windows_reads_zero_when_the_call_fails as you described. A stand-in windll is patched onto system_memory.ctypes, and its GlobalMemoryStatusEx asserts dwLength == sizeof, writes ullAvailPhys = 6 GiB, and returns 1, or 0 in the second test.
• fit.md: it names ullAvailPhys from GlobalMemoryStatusEx as the Windows reader, and says the tests use sample /proc/meminfo and vm_stat output and a stand-in GlobalMemoryStatusEx. The module docstring says "sample" rather than "recorded" too.
• Non-blocking items, also done:
  • _total() now has its own tests: pages × page size from sysconf, and 0 with no sysconf.
  • A hung vm_stat (TimeoutExpired, a SubprocessError) falls back to total.

test_system_memory.py: 12 passed. Ruff and check_docs.py are clean.

[coderabbitai]

Actionable comments posted: 1

---

• 🪄 Fix CodeRabbit comments on this PR

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Inline comments:
Review comments at
@surfsense_local/backend/tests/unit/llm/hardware/test_system_memory.py:
- Around line 118-119: Update the `hung` stand-in in the `_darwin()` test to
assert that `subprocess.run` receives `timeout=5` before raising
`TimeoutExpired`, so the test fails if `_darwin()` omits or changes the timeout.

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• Configuration used: Repository: MODSetter/SurfSense/.coderabbit.yaml
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Reviewing files that changed from the base of the PR and between be6342a and 744e50f.

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• docs/architecture/local-models/fit.md
• surfsense_local/backend/tests/unit/llm/hardware/test_system_memory.py

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