improvement(mothership): do not silently re-route missing stream id

[icecrasher321]

Summary

Stream ID must exist

Type of Change

• Bug fix

Testing

Tested manually

Checklist

• Code follows project style guidelines
• Self-reviewed my changes
• Tests added/updated and passing
• No new warnings introduced
• I confirm that I have read and agree to the terms outlined in the Contributor License Agreement (CLA)

[vercel]

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1 Skipped Deployment

Project	Deployment	Actions	Updated (UTC)
docs	Skipped		Apr 24, 2026 11:33pm

[cursor]

PR Summary

Low Risk
Low risk: tightens client-side validation to reject events with missing/empty streamId, which may cause previously accepted malformed events to be dropped but doesn’t alter core processing logic.

Overview
Tightens stream event envelope validation by requiring stream.streamId to be a non-empty string in isStreamRef, preventing events with empty/missing stream IDs from being accepted (and potentially silently re-routed).

^{Reviewed by Cursor Bugbot for commit eb6fa2c. Configure here.}

[greptile-apps]

Greptile Summary

This PR tightens the isStreamRef type guard in the copilot session contract by adding a non-empty length check (value.streamId.length > 0), preventing an empty-string streamId from passing validation and being silently forwarded downstream.

Confidence Score: 5/5

Safe to merge — single-line guard addition with no risk of regression.

The change is a one-liner that adds a logically correct, non-breaking constraint. It only tightens validation for an edge case (empty streamId) that should never be valid. No other P1/P0 findings present.

No files require special attention.

Important Files Changed

Filename	Overview
apps/sim/lib/copilot/request/session/contract.ts	Adds a non-empty string guard on streamId in isStreamRef; change is minimal, correct, and consistent with the rest of the validator.

Flowchart

%%{init: {'theme': 'neutral'}}%%
flowchart TD
    A[Raw stream event JSON] --> B[parsePersistedStreamEventEnvelopeJson]
    B --> C{Valid JSON?}
    C -- No --> D[Return: invalid_json error]
    C -- Yes --> E[parsePersistedStreamEventEnvelope]
    E --> F{isContractEnvelope?}
    F -- Yes --> G[Return: ok=true]
    F -- No --> H{isSyntheticFilePreviewEventEnvelope?}
    H -- Yes --> G
    H -- No --> I[Return: invalid_stream_event error]
    F --> J[isValidEnvelopeShell]
    J --> K[isStreamRef]
    K --> L{streamId is string?}
    L -- No --> M[FAIL]
    L -- Yes --> N{streamId.length > 0?}
    N -- No --> M
    N -- Yes --> O[Continue validation...]

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_{Reviews (1): Last reviewed commit: "improvement(mothership): do not silently..." | Re-trigger Greptile}