fix(variables): fix variable resolution error and start block outputs

[Sg312]

Summary

Fix variable resolution error surfacing and start block outputs

Type of Change

• Bug fix

Testing

Manual

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)

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1 Skipped Deployment

Project	Deployment	Preview	Comments	Updated (UTC)
docs	Skipped			Nov 7, 2025 11:00pm

[greptile-apps]

Greptile Overview

Greptile Summary

This PR improves error handling in the block executor and fixes variable resolution behavior when blocks haven't executed yet.

Key changes:

• Error handling refactoring: Extracted duplicate error handling logic into a dedicated handleBlockError method that properly catches and surfaces input resolution errors, ensuring errors during variable resolution are now properly logged and handled
• Variable resolution fix: Changed BlockResolver to return undefined instead of throwing an error when a block output isn't found, allowing graceful handling of missing upstream block outputs
• Start block output filtering: Modified start block output generation to exclude empty conversationId fields (setting to undefined instead of empty string) to prevent unnecessary fields in block outputs

Confidence Score: 4/5

• This PR is safe to merge with minor testing considerations
• The refactoring is well-structured and improves error handling. The behavior change for conversationId (empty string to undefined) may require test updates. The variable resolution change is sensible but should be verified with integration tests to ensure no regressions in workflows that depend on this behavior.
• apps/sim/executor/utils/start-block.ts - verify test compatibility with conversationId behavior change

Important Files Changed

File Analysis

Filename	Score	Overview
apps/sim/executor/execution/block-executor.ts	5/5	Refactored error handling to properly catch and surface input resolution errors by extracting error handling logic into a dedicated handleBlockError method
apps/sim/executor/utils/start-block.ts	4/5	Changed conversationId handling to be undefined instead of empty string when not set, may need test updates
apps/sim/executor/variables/resolvers/block.ts	5/5	Changed block output resolution to return undefined instead of throwing error when block state is not found

Sequence Diagram

sequenceDiagram
    participant Executor as BlockExecutor
    participant Resolver as VariableResolver
    participant BlockRes as BlockResolver
    participant State as ExecutionState
    
    Note over Executor: Block Execution Start
    
    Executor->>Resolver: resolveInputs(ctx, nodeId, params, block)
    Resolver->>BlockRes: resolve(reference, context)
    BlockRes->>State: getBlockOutput(blockId, currentNodeId)
    
    alt Block output exists
        State-->>BlockRes: return output
        BlockRes-->>Resolver: return resolved value
        Resolver-->>Executor: return resolvedInputs
        Note over Executor: Continue execution
    else Block output not found (NEW)
        State-->>BlockRes: return undefined
        BlockRes-->>Resolver: return undefined (no error thrown)
        Resolver-->>Executor: return resolvedInputs
        Note over Executor: Handle gracefully
    else Resolution error (NEW)
        BlockRes-->>Resolver: throw error
        Resolver-->>Executor: throw error
        Executor->>Executor: handleBlockError(phase: 'input_resolution')
        Note over Executor: Log error & set error output
    end
    
    alt Has error port
        Executor-->>Executor: Return error output
    else No error port
        Executor-->>Executor: Throw BlockExecutionError
    end

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