Remove nest-asyncio dependency

[miguelg719]

Summary by cubic

Removes the nest-asyncio dependency and switches replay metrics fetching to a sync HTTP path when an event loop is running, avoiding loop patching. This unblocks the Python 3.14 upgrade for STG-1374.

• Dependencies

  • Removed nest-asyncio from pyproject.toml.

• Refactors

  • Added _get_replay_metrics_sync and shared _parse_replay_metrics_data in api.py.
  • In main.py, use _get_replay_metrics_sync if a loop is running; otherwise use asyncio.run(_get_replay_metrics()).
  • Removed nest_asyncio import and apply calls.

^{Written for commit d9174e0. Summary will update on new commits. Review in cubic}

[cubic-dev-ai]

cubic analysis

1 issue found across 3 files

Confidence score: 2/5

• There is a clear user-facing regression risk: in stagehand/main.py the async-first code path now returns empty StagehandMetrics() instead of fetching from the API, which can silently drop metrics for most users.
• Given the 7/10 severity and high confidence, this is likely to cause real data loss and should be addressed before merging.
• Pay close attention to stagehand/main.py - async access to .metrics returns empty metrics instead of fetching from the API.

Prompt for AI agents (all issues)

Check if these issues are valid — if so, understand the root cause of each and fix them.


<file name="stagehand/main.py">

<violation number="1" location="stagehand/main.py:784">
P1: Silent data loss: accessing `.metrics` in an async context (the primary usage pattern) now returns empty `StagehandMetrics()` instead of fetching from the API. Since Stagehand is async-first, most users will hit this code path and silently get no data.

At minimum, log a warning so users know metrics aren't being fetched. Ideally, provide an async alternative like `await stagehand.get_metrics()` so users in async contexts can still retrieve API metrics.</violation>
</file>

Status	Acceptance criteria	Notes
✅	Remove nest-asyncio from pyproject.toml dependencies	Removed nest-asyncio entry from pyproject.toml
✅	Remove import of nest_asyncio from code	Deleted 'import nest_asyncio' from stagehand/main.py
✅	Eliminate nest_asyncio.apply() usage to avoid event loop patching	Removed nest_asyncio.apply() call and related handling
✅	When already in an async context, return empty StagehandMetrics instead of patching loop	Returns StagehandMetrics() when asyncio.get_running_loop() succeeds
✅	Use asyncio.run(get_replay_metrics()) only when no running loop	Calls asyncio.run(get_replay_metrics()) in RuntimeError except branch
✅	Add changeset noting removal of nest-asyncio	Added .changeset file referencing removal
⚠️	Unblocks Python 3.14 upgrade (no asyncio-level patching dependency)	Dependency removed but no CI/tests validating Python 3.14 compatibility

Architecture diagram

sequenceDiagram
    participant Client
    participant SH as Stagehand (main.py)
    participant Loop as asyncio
    participant RM as get_replay_metrics()

    Note over SH: Attribute Access Interception (__getattribute__)

    Client->>SH: Access metrics property
    
    SH->>Loop: asyncio.get_running_loop()
    
    alt Loop is already running (Async context)
        Loop-->>SH: Running loop detected
        Note over SH: CHANGED: No longer patches loop with nest-asyncio
        SH-->>Client: NEW: Return empty StagehandMetrics()
    else No loop running (Sync context)
        Loop-->>SH: Raise RuntimeError
        SH->>RM: asyncio.run(get_replay_metrics())
        RM-->>SH: Replay data
        SH-->>Client: Return metrics
    end

    opt Exception during metrics retrieval
        SH-->>Client: Return empty StagehandMetrics()
    end

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Linked issue analysis

Linked issue: STG-1374: [Ramp] Ramp,

Status	Acceptance criteria	Notes
✅	Remove nest-asyncio from pyproject.toml	Removed nest-asyncio entry from pyproject.toml
✅	Remove nest_asyncio import and apply calls in code	nest_asyncio import and apply calls deleted in main.py
✅	Add a synchronous replay metrics fetch path to avoid event loop patching	Added _get_replay_metrics_sync implementation in api.py
✅	Use sync fetch when an event loop is running	main.py detects running loop and calls sync fetch
✅	Preserve async fetch when no loop is running (use asyncio.run)	Retains asyncio.run path for async fetch when no loop
✅	Share parsing logic between async and sync replay metrics paths	Introduced _parse_replay_metrics_data shared parser
✅	Proper error handling and logging in new functions	Try/except and self.logger.error present in both fetchers
✅	Expose Stagehand._get_replay_metrics_sync attribute	Assigned Stagehand._get_replay_metrics_sync at module end
✅	Update module exports (__all__) to include _get_replay_metrics_sync	__all__ updated to include _get_replay_metrics_sync
✅	Ensure no other references to nest_asyncio remain	Removed import and dependency; no other references in diffs
⚠️	Unblock Python 3.14 upgrade (remove nest-asyncio as blocker)	Removal reduces blocker but full compatibility not verified

[miguelg719]

@cubic-dev-ai

[cubic-dev-ai]

@cubic-dev-ai

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[cubic-dev-ai]

cubic analysis

No issues found across 4 files

Confidence score: 5/5

• Automated review surfaced no issues in the provided summaries.
• No files require special attention.

Linked issue analysis

Linked issue: STG-1374: [Ramp] Ramp,

Status	Acceptance criteria	Notes
✅	Remove nest-asyncio from pyproject.toml	Removed nest-asyncio entry from pyproject.toml
✅	Remove nest_asyncio import and apply calls in code	nest_asyncio import and apply calls deleted in main.py
✅	Add a synchronous replay metrics fetch path to avoid event loop patching	Added _get_replay_metrics_sync implementation in api.py
✅	Use sync fetch when an event loop is running	main.py detects running loop and calls sync fetch
✅	Preserve async fetch when no loop is running (use asyncio.run)	Retains asyncio.run path for async fetch when no loop
✅	Share parsing logic between async and sync replay metrics paths	Introduced _parse_replay_metrics_data shared parser
✅	Proper error handling and logging in new functions	Try/except and self.logger.error present in both fetchers
✅	Expose Stagehand._get_replay_metrics_sync attribute	Assigned Stagehand._get_replay_metrics_sync at module end
✅	Update module exports (__all__) to include _get_replay_metrics_sync	__all__ updated to include _get_replay_metrics_sync
✅	Ensure no other references to nest_asyncio remain	Removed import and dependency; no other references in diffs
⚠️	Unblock Python 3.14 upgrade (remove nest-asyncio as blocker)	Removal reduces blocker but full compatibility not verified

Architecture diagram

sequenceDiagram
    participant User as Caller
    participant SH as Stagehand (main.py)
    participant Loop as asyncio Loop
    participant API as API Layer (api.py)
    participant BB as Browserbase API

    User->>SH: Access .metrics property
    SH->>SH: __getattribute__("metrics")
    
    SH->>Loop: asyncio.get_running_loop()
    
    alt Loop is already running (e.g. Notebook, Async App)
        Loop-->>SH: loop instance
        SH->>API: NEW: _get_replay_metrics_sync()
        Note over API,BB: Synchronous HTTP request
        API->>BB: GET /sessions/{id}/replay (Sync)
        BB-->>API: JSON Response
    else No loop running
        Loop-->>SH: RuntimeError
        SH->>Loop: asyncio.run(_get_replay_metrics())
        Note over API,BB: Asynchronous HTTP request
        API->>BB: GET /sessions/{id}/replay (Async)
        BB-->>API: JSON Response
    end

    API->>API: CHANGED: _parse_replay_metrics_data(json)
    Note right of API: Shared parsing logic for<br/>sync and async paths
    
    API-->>SH: StagehandMetrics object
    SH-->>User: Return metrics

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