Fix flaky SessionFs workspace metadata E2E test

[stephentoub]

Why

The Should_Write_Workspace_Metadata_Via_SessionFs C# E2E test fails intermittently in CI (e.g. this run) with:

Assert.Contains() Failure: Sub-string not found
String:    ""
Not found: "<session-id>"

Root cause

The test waited only for workspace.yaml to exist before reading it. The runtime writes that file via the SessionFs provider using a truncate-then-write (File.WriteAllTextAsync), so File.Exists returns true the moment the file is created/truncated to 0 bytes, before the content is flushed. The test could read the empty file in that window and fail the assertion. The same race existed in the sibling plan.md test.

Fix

Wait for the expected content (not just existence) before asserting. Since the content-aware wait already throws on timeout, the trailing Assert.Contains calls became redundant and were removed, leaving the wait as the assertion (matching the existing index.md wait-only style in this file).

I checked the equivalent test in every other language suite:

• Python: had the same disk-read race; switched both the workspace.yaml and plan.md tests to the already-present (but unused) wait_for_content helper.
• Go: already robust (waitForFileContent), no change.
• Node: not susceptible; it uses an in-memory provider with atomic writes and reads back through the provider rather than raw disk. No change.
• Rust / Java: no equivalent SessionFs workspace-metadata test exists. No change.

Validation

Both .NET target frameworks (net8.0 + net472) build clean, and ruff check passes on the Python file.

[Copilot]

Pull request overview

This PR reduces intermittent CI failures in the SessionFs workspace-metadata E2E tests by switching from “wait for file existence” to “wait until file contains expected content”, avoiding a race where the runtime truncates/creates the file before content is fully written.

Changes:

• Python: replace wait_for_path + read_text + assert with a single wait_for_content(...) for workspace.yaml and plan.md.
• .NET: update WaitForConditionAsync predicates to require both file existence and expected content before proceeding (removing the follow-up Assert.Contains that could still race on empty reads).

Show a summary per file

File	Description
python/e2e/test_session_fs_e2e.py	Uses wait_for_content for workspace.yaml and plan.md to avoid empty/partial reads immediately after file creation/truncation.
dotnet/test/E2E/SessionFsE2ETests.cs	Waits for workspace.yaml / plan.md to contain expected substrings (session id / plan text) rather than only waiting for the files to exist.

Copilot's findings

• Files reviewed: 2/2 changed files
• Comments generated: 0

[github-actions]

Cross-SDK Consistency Review ✅

I reviewed this PR against all six SDK implementations. The changes are consistent and the PR description's analysis is accurate.

SDK	Status	Notes
.NET	✅ Fixed in this PR	Both workspace.yaml and plan.md tests updated to wait for content, not just existence
Python	✅ Fixed in this PR	Both tests switched to wait_for_content helper
Go	✅ Already robust	Uses waitForFileContent which polls for both file existence and content
Node.js	✅ Not susceptible	Uses MemoryProvider (in-memory); reads go through the provider API, which has atomic semantics — no disk write race
Rust	✅ N/A	No equivalent SessionFs workspace-metadata E2E test exists
Java	✅ N/A	No equivalent SessionFs workspace-metadata E2E test exists

No further changes needed for cross-SDK consistency.

Generated by SDK Consistency Review Agent for issue #1599 · sonnet46 841.6K · ◷