{"record":{"id":"2da99c62c5be6854","repo":"deepset-ai/haystack","slug":"couldn-t-deserialize-component-name-of-class","errorCode":null,"errorMessage":"Couldn't deserialize component '{name}' of class '{component_class.__name__}' with the following data:\n{data_str}\n\nOriginal error: {e}","messagePattern":"Couldn't deserialize component '(.+?)' of class '(.+?)' with the following data:\n(.+?)\n\nOriginal error: (.+?)","errorType":"exception","errorClass":"DeserializationError","httpStatus":null,"severity":"error","filePath":"haystack/core/pipeline/base.py","lineNumber":282,"sourceCode":"                try:\n                    instance = component_from_dict(component_class, component_data, name, callbacks)\n                except Exception as e:\n                    # Convert to JSON with indentation, truncate if too long\n                    try:\n                        data_str = json.dumps(component_data, default=str, indent=2)\n                    except Exception:\n                        data_str = str(component_data)\n\n                    max_len = 1000\n                    if len(data_str) > max_len:\n                        data_str = data_str[:max_len] + \"\\n... (truncated)\"\n\n                    msg = (\n                        f\"Couldn't deserialize component '{name}' of class '{component_class.__name__}' \"\n                        f\"with the following data:\\n{data_str}\\n\\n\"\n                        f\"Original error: {e}\"\n                    )\n                    raise DeserializationError(msg) from e\n            pipe.add_component(name=name, instance=instance)\n\n        for connection in data.get(\"connections\", []):\n            if \"sender\" not in connection:\n                raise PipelineError(f\"Missing sender in connection: {connection}\")\n            if \"receiver\" not in connection:\n                raise PipelineError(f\"Missing receiver in connection: {connection}\")\n            pipe.connect(sender=connection[\"sender\"], receiver=connection[\"receiver\"])\n\n        return pipe\n\n    def dumps(self, marshaller: Marshaller = DEFAULT_MARSHALLER) -> str:\n        \"\"\"\n        Returns the string representation of this pipeline according to the format dictated by the `Marshaller` in use.\n\n        :param marshaller:\n            The Marshaller used to create the string representation. Defaults to `YamlMarshaller`.\n        :returns:","sourceCodeStart":264,"sourceCodeEnd":300,"githubUrl":"https://github.com/deepset-ai/haystack/blob/e318778c9bf60a1963e3b5f451359655dd696c30/haystack/core/pipeline/base.py#L264-L300","documentation":"When a component's own from_dict fails during pipeline deserialization, Haystack wraps the original exception in DeserializationError, including the component name, class, the serialized data, and the original error. This separates pipeline-level structure issues from component-level init parameter problems.","triggerScenarios":"from_dict where a component's init_parameters don't match what the component's from_dict expects — wrong/missing keys, invalid values (e.g. bad model name), or a component whose from_dict throws for any reason.","commonSituations":"Hand-edited init_parameters; pipeline dumped with one component version and loaded with another where parameters changed; secrets/env vars expected at load time missing; invalid model identifiers passed to loaders.","solutions":["Read the 'Original error' in the message and fix the offending init_parameters in the pipeline data","Check the component class's from_dict signature for required parameters","Regenerate the pipeline file by dumping it from code with the same library version","Pin matching library versions between dump and load environments"],"exampleFix":"// before\ncomponents:\n  embedder:\n    type: haystack.components.embedders.SentenceTransformersTextEmbedder\n    init_parameters:\n      modle: \"all-MiniLM-L6-v2\"  # typo\n\n// after\ncomponents:\n  embedder:\n    type: haystack.components.embedders.SentenceTransformersTextEmbedder\n    init_parameters:\n      model: \"all-MiniLM-L6-v2\"","handlingStrategy":"try-catch","validationCode":"def safe_component_deserialize(comp_class, init_data: dict) -> bool:\n    try:\n        comp_class.from_dict({\"init_parameters\": init_data})\n        return True\n    except Exception as e:\n        logging.warning(\"Component %s cannot deserialize: %s\", comp_class.__name__, e)\n        return False","typeGuard":null,"tryCatchPattern":"try:\n    pipe = Pipeline.from_dict(data)\nexcept DeserializationError as e:\n    logging.error(\"Component-level deserialization failed: %s\", e)\n    # inspect e.__cause__ for the original error\n    raise","preventionTips":["Match library versions between the dumping and loading environments","Keep init_parameters keys exactly as the component's from_dict expects","Ensure required env vars/secrets are set before from_dict","Test round-trip dumps()/from_dict() for custom components"],"tags":["serialization","deserialization","pipeline","haystack"],"backgroundTag":"deserialization-failed","analyzedSha":"e318778c9bf60a1963e3b5f451359655dd696c30","analyzedAt":"2026-08-30T11:45:20.711Z","schemaVersion":2},"datasetVersion":"2026-08-30T13:17:10.514Z"}