fix(billing): Skip billing on streamed workflows with byok

[TheodoreSpeaks]

Summary

BYOK users were incorrectly billed when using the streamed response. This was because the byok check is skipped for streamed responses because they're streamed live to the user. Added helper method zeroCostForBYOK to zero out cost from the execution stream, while keeping tool costs.

Also added tool cost to the execution log cost summary so that the total lines up.

Also upgraded logging byok so we can see the logic in prod.

Type of Change

• Bug fix
• New feature
• Breaking change
• Documentation
• Other: ___________

Testing

• Replicated bug locally, validated that model costs are 0 after change was applied.
• Validated non-byok users are billed both for streaming and non-streaming

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)

Screenshots/Videos

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Project	Deployment	Actions	Updated (UTC)
docs	Ready	Preview, Comment	Apr 8, 2026 11:08pm

[cursor]

PR Summary

Medium Risk
Touches provider execution/billing paths for streaming responses by intercepting and freezing execution.output.cost, which could affect downstream cost reporting if assumptions about mutability differ. UI and tokenization changes are low risk but depend on the new cost.pricing sentinel behavior.

Overview
Fixes incorrect billing for BYOK users on streaming executions by intercepting StreamingExecution responses and forcing model cost to remain zero via zeroCostForBYOK, while still allowing tool costs to accumulate.

Updates streaming tokenization to not recalculate/overwrite cost when the billing layer has already set output.cost.pricing (used as a sentinel for explicit billing decisions), and adjusts log details UI to display aggregated tool usage cost and clarify that totals include model + tool usage.

^{Reviewed by Cursor Bugbot for commit 3792e01. Bugbot is set up for automated code reviews on this repo. Configure here.}

[greptile-apps]

Greptile Summary

This PR fixes a billing bug where BYOK (Bring Your Own Key) users were incorrectly charged when using streamed workflow responses. It introduces zeroCostForBYOK, which intercepts cost writes on the streaming output object via Object.defineProperty, and also upgrades several logger.debug calls to logger.info for better production visibility.

Confidence Score: 3/5

The fix addresses the core billing bug for streaming BYOK users, but two reliability gaps could allow incorrect billing to slip through in edge cases.

The ZERO_COST constant uses updatedAt: '' inconsistently with the synchronous path, and the zeroCostForBYOK guard silently exits without logging when output is absent, making it impossible to detect provider-specific gaps in production. These are correctness risks in the billing path that warrant attention before merging.

apps/sim/providers/index.ts — specifically ZERO_COST.pricing.updatedAt and the early-return path in zeroCostForBYOK

Vulnerabilities

No security concerns identified. The BYOK billing fix correctly prevents cost attribution for user-supplied keys. The new logger.info call logging workspaceId is standard practice for backend service tracing and does not expose user-facing secrets or credentials.

Important Files Changed

Filename	Overview
apps/sim/providers/index.ts	Adds zeroCostForBYOK to intercept streaming cost writes for BYOK users; has a minor updatedAt: '' inconsistency vs the synchronous zero-cost path, and a potential gap if providers replace output entirely during streaming rather than mutating it in-place.

Flowchart

%%{init: {'theme': 'neutral'}}%%
flowchart TD
    A[executeProviderRequest] --> B{workspaceId present?}
    B -->|Yes| C[getApiKeyWithBYOK]
    C --> D[isBYOK set]
    B -->|No| E[isBYOK = false]
    D --> F[provider.executeRequest]
    E --> F
    F --> G{Response type?}
    G -->|StreamingExecution| H{isBYOK?}
    H -->|Yes| I[zeroCostForBYOK\nObject.defineProperty cost trap]
    I --> J[Return StreamingExecution]
    H -->|No| J
    G -->|ReadableStream| K[Return stream\n⚠️ No BYOK check]
    G -->|ProviderResponse| L{shouldBillModelUsage AND not isBYOK?}
    L -->|Yes| M[calculateCost → response.cost]
    L -->|No| N[Zero cost → response.cost]
    M --> O[Return response]
    N --> O

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