{"record":{"id":"5e3ad0b5fbbb7492","repo":"plandex-ai/plandex","slug":"fast-apply-succeeded-but-has-d-syntax-errors","errorCode":null,"errorMessage":"fast apply succeeded, but has %d syntax errors","messagePattern":"fast apply succeeded, but has (.+?) syntax errors","errorType":"http","errorClass":null,"httpStatus":500,"severity":"warning","filePath":"app/server/model/plan/build_race.go","lineNumber":157,"sourceCode":"\t\t\t\tonFail()\n\t\t\t\treturn\n\t\t\t}\n\n\t\t\tif fastApplyRes == \"\" {\n\t\t\t\tlog.Printf(\"buildRace - fast apply isn't defined or failed to run\")\n\t\t\t\tsendErr(nil) // no error, just no fast apply\n\t\t\t\tonFail()\n\t\t\t\treturn\n\t\t\t}\n\n\t\t\t// log.Printf(\"buildRace - fast apply result:\\n\\n%s\", fastApplyRes)\n\n\t\t\tfastApplySyntaxErrors := fileState.validateSyntax(buildCtx, fastApplyRes)\n\t\t\tfileState.builderRun.FastApplySyntaxErrors = fastApplySyntaxErrors\n\n\t\t\tif len(fastApplySyntaxErrors) > 0 {\n\t\t\t\tlog.Printf(\"buildRace - fast apply succeeded, but has %d syntax errors\", len(fastApplySyntaxErrors))\n\t\t\t\tsendErr(fmt.Errorf(\"fast apply succeeded, but has %d syntax errors\", len(fastApplySyntaxErrors)))\n\t\t\t\tonFail()\n\t\t\t\treturn\n\t\t\t}\n\n\t\t\tlog.Printf(\"buildRace - fast apply returned, validating...\t\")\n\t\t\tvalidateResult, err := fileState.buildValidateLoop(buildCtx, buildValidateLoopParams{\n\t\t\t\toriginalFile:    originalFile,\n\t\t\t\tupdated:         fastApplyRes,\n\t\t\t\tproposedContent: proposedContent,\n\t\t\t\tdesc:            desc,\n\t\t\t\treasons:         reasons,\n\n\t\t\t\t// just validate since we're already building replacements in parallel\n\t\t\t\tmaxAttempts:                1,\n\t\t\t\tvalidateOnlyOnFinalAttempt: true,\n\t\t\t\tisInitial:                  false,\n\t\t\t\tsessionId:                  sessionId,\n\t\t\t})","sourceCodeStart":139,"sourceCodeEnd":175,"githubUrl":"https://github.com/plandex-ai/plandex/blob/e2d772072efadbe41d2946d97d79be55532dbab5/app/server/model/plan/build_race.go#L139-L175","documentation":"Fast apply produced output, but fileState.validateSyntax found one or more syntax errors in the result, so the fast-apply leg is rejected. The count of errors is reported in the message and stored on builderRun.FastApplySyntaxErrors. onFail() is then called to start the whole-file build fallback, so the error is informational about the race losing, not a crash.","triggerScenarios":"The fast-apply model output, when parsed by validateSyntax with buildCtx, contains unbalanced braces, invalid tokens, or truncation — i.e. len(fastApplySyntaxErrors) > 0 after a successful fastApplyCh receive.","commonSituations":"Model applying a search/replace patch that corrupts surrounding code; truncated generation at token limits; applying edits to files in languages the syntax parser misconfigures; mixed indentation/encoding breaking the parser.","solutions":["Rely on the fallback: onFail() already triggers the whole-file rebuild, so no user action is strictly needed","Inspect fileState.builderRun.FastApplySyntaxErrors for the specific parse errors","Increase generation limits or improve the fast-apply prompt for large edits","Check that the correct parser/language is configured for the file being edited"],"exampleFix":null,"handlingStrategy":"validation","validationCode":"if err := buildCtx.Err(); err == nil {\n\tif errs := fileState.validateSyntax(buildCtx, fastApplyRes); len(errs) > 0 {\n\t\tlog.Printf(\"fast apply output invalid, using fallback: %v\", errs)\n\t\tonFail()\n\t\treturn\n\t}\n}","typeGuard":"func hasSyntaxErrors(errs []string) bool { return len(errs) > 0 }","tryCatchPattern":"fastApplySyntaxErrors := fileState.validateSyntax(buildCtx, fastApplyRes)\nif hasSyntaxErrors(fastApplySyntaxErrors) {\n\tsendErr(fmt.Errorf(\"fast apply succeeded, but has %d syntax errors\", len(fastApplySyntaxErrors)))\n\tonFail()\n\treturn\n}","preventionTips":["Validate fast-apply output with validateSyntax before accepting it","Keep fast-apply edits small and localized to reduce corruption risk","Configure the correct language parser for the target file","Persist FastApplySyntaxErrors for post-hoc analysis of failure patterns"],"tags":["go","syntax","validation","fast-apply"],"backgroundTag":"syntax-validation-failed","analyzedSha":"e2d772072efadbe41d2946d97d79be55532dbab5","analyzedAt":"2026-09-05T20:56:53.631Z","contentChangedAt":"2026-09-05T20:56:53.631Z","schemaVersion":2},"datasetVersion":"2026-09-14T00:17:10.932Z"}