[GH-ISSUE #154] runDerivedOperation does not catch synchronous compute exceptions in derived MCP tools #102

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opened 2026-10-15 18:21:11 +00:00 by bsakaguchi · 0 comments

bsakaguchi commented

2026-10-15 18:21:11 +00:00

Owner

Originally created by @morluto on GitHub (Jul 14, 2026).
Original GitHub issue: https://github.com/morluto/rea/issues/154

Problem

The runDerivedOperation helper executes the compute callback directly and returns an uncaught rejection when that callback throws. Several MCP handlers rely on runDerivedOperation to return a Result, but thrown values bypass toCallToolResult and surface as transport errors instead of structured MCP error content.

Evidence

Uncaught sync throw path

src/server/runDerivedOperation.ts:39

Call sites without local try/catch

src/server/registerArtifactComparisonTool.ts:34-36 (compareArtifacts)
src/server/registerBundleComparisonTool.ts:67-75 (compareBundles)
src/server/registerFunctionComparisonTool.ts:36-37 (compareFunctions)
src/server/registerInvestigationTools.ts:201-203 (findChangedBehavior)
src/server/registerInvestigationTools.ts:263-265 (buildCallPath)
src/server/registerInvestigationTools.ts:329-331 (correlateStaticAndRuntime)
src/server/registerInvestigationTools.ts:408-414 (verifyReconstruction)

Throwing comparators/parsers used in these flows

src/domain/changedBehavior.ts throws in parseComparisonEvidence and parseResult (TypeError) for invalid evidence contracts and malformed payloads.
src/domain/functionComparison.ts calls parseFunctionEvidence, which throws TypeError on malformed function Evidence.
src/domain/artifactComparison.ts and src/domain/artifactInventoryEvidence.ts throw for malformed artifact Evidence and pagination/graph mismatch cases.
src/domain/bundleComparison.ts throws for invalid explicit pair references and entity bounds via TypeError.

Impact

Malformed user-provided Evidence or edge-case comparison input can crash the tool handler path instead of producing a deterministic MCP tool error, reducing diagnosability and resilience of MCP/CLI behavior.

Repro sketch

Supply invalid comparison Evidence to a derive tool such as compare_artifacts or compare_functions (e.g., mismatched provider/predicate or malformed evidence structure).
The comparison callback may throw and the request is handled through an unguarded runDerivedOperation call.

Proposed outcome

Ensure synchronous compute exceptions are converted to error Results and then translated through toCallToolResult, or catch in each affected handler.
Keep cancellation semantics from AnalysisCancelledError unchanged.

Notes

registerProcessComparisonTool currently wraps runDerivedOperation in try/catch; this issue is specifically for the non-protected derived-tool paths above.

Originally created by @morluto on GitHub (Jul 14, 2026). Original GitHub issue: https://github.com/morluto/rea/issues/154 ## Problem The runDerivedOperation helper executes the compute callback directly and returns an uncaught rejection when that callback throws. Several MCP handlers rely on runDerivedOperation to return a `Result`, but thrown values bypass toCallToolResult and surface as transport errors instead of structured MCP error content. ## Evidence ### Uncaught sync throw path - src/server/runDerivedOperation.ts:39 ### Call sites without local try/catch - src/server/registerArtifactComparisonTool.ts:34-36 (compareArtifacts) - src/server/registerBundleComparisonTool.ts:67-75 (compareBundles) - src/server/registerFunctionComparisonTool.ts:36-37 (compareFunctions) - src/server/registerInvestigationTools.ts:201-203 (findChangedBehavior) - src/server/registerInvestigationTools.ts:263-265 (buildCallPath) - src/server/registerInvestigationTools.ts:329-331 (correlateStaticAndRuntime) - src/server/registerInvestigationTools.ts:408-414 (verifyReconstruction) ### Throwing comparators/parsers used in these flows - src/domain/changedBehavior.ts throws in parseComparisonEvidence and parseResult (TypeError) for invalid evidence contracts and malformed payloads. - src/domain/functionComparison.ts calls parseFunctionEvidence, which throws TypeError on malformed function Evidence. - src/domain/artifactComparison.ts and src/domain/artifactInventoryEvidence.ts throw for malformed artifact Evidence and pagination/graph mismatch cases. - src/domain/bundleComparison.ts throws for invalid explicit pair references and entity bounds via TypeError. ## Impact Malformed user-provided Evidence or edge-case comparison input can crash the tool handler path instead of producing a deterministic MCP tool error, reducing diagnosability and resilience of MCP/CLI behavior. ## Repro sketch 1. Supply invalid comparison Evidence to a derive tool such as compare_artifacts or compare_functions (e.g., mismatched provider/predicate or malformed evidence structure). 2. The comparison callback may throw and the request is handled through an unguarded runDerivedOperation call. ## Proposed outcome - Ensure synchronous compute exceptions are converted to error Results and then translated through toCallToolResult, or catch in each affected handler. - Keep cancellation semantics from AnalysisCancelledError unchanged. ## Notes - registerProcessComparisonTool currently wraps runDerivedOperation in try/catch; this issue is specifically for the non-protected derived-tool paths above.

bsakaguchi

2026-10-15 18:21:11 +00:00