{"record":{"id":"eedce09741a482ba","repo":"vxcontrol/pentagi","slug":"tar-archive-header-generation-failed-w","errorCode":null,"errorMessage":"tar archive header generation failed: %w","messagePattern":"tar archive header generation failed: %w","errorType":"exception","errorClass":null,"httpStatus":null,"severity":"error","filePath":"backend/pkg/tools/terminal.go","lineNumber":474,"sourceCode":"\t}\n\tif !isRunning {\n\t\treturn fmt.Errorf(\"target container is not operational\")\n\t}\n\n\t// Docker SDK requires TAR format for file transfer\n\ttarBuffer := &bytes.Buffer{}\n\tarchiveWriter := tar.NewWriter(tarBuffer)\n\tdefer archiveWriter.Close()\n\n\tfilename := filepath.Base(path)\n\tfileDescriptor := &tar.Header{\n\t\tName: filename,\n\t\tMode: 0600,\n\t\tSize: int64(len(content)),\n\t}\n\terr = archiveWriter.WriteHeader(fileDescriptor)\n\tif err != nil {\n\t\treturn fmt.Errorf(\"tar archive header generation failed: %w\", err)\n\t}\n\n\t_, err = archiveWriter.Write([]byte(content))\n\tif err != nil {\n\t\treturn fmt.Errorf(\"tar archive content serialization failed: %w\", err)\n\t}\n\n\terr = archiveWriter.Close()\n\tif err != nil {\n\t\treturn fmt.Errorf(\"failed to close tar writer: %w\", err)\n\t}\n\n\tdir := filepath.Dir(path)\n\terr = t.dockerClient.CopyToContainer(ctx, containerName, dir, tarBuffer, client.CopyToContainerOptions{\n\t\tAllowOverwriteDirWithFile: true,\n\t})\n\tif err != nil {\n\t\treturn fmt.Errorf(\"container file transfer failed: %w\", err)","sourceCodeStart":456,"sourceCodeEnd":492,"githubUrl":"https://github.com/vxcontrol/pentagi/blob/ea665308baaff015b226f308438a68d929d0f29b/backend/pkg/tools/terminal.go#L456-L492","documentation":"writeFileToContainer builds an in-memory tar archive before copying the file into the flow's Docker container. This error wraps archiveWriter.WriteHeader failing while emitting the tar.Header for the target file (name=basename, mode 0600, size=len(content)). WriteHeader only fails on programmer-level problems: a nil/invalid header, a negative or unset Size, or an I/O error on the underlying buffer, so it is rare in practice.","triggerScenarios":"Calling WriteFile or EditFile when the tar.Header passed to WriteHeader is invalid (e.g. Size would be negative because content length overflows int, or the header struct is malformed); the bytes.Buffer backing the tar writer returns an I/O error (only possible with an out-of-memory condition).","commonSituations":"Practically only seen with extremely large or corrupted content buffers causing memory allocation failure; a plain memory-constrained host (OOM pressure) during agent file-write operations; virtually never from bad user input.","solutions":["Check host/container memory pressure; retry the WriteFile/EditFile tool call once memory is available","Verify content length is a sane non-negative size and retry the operation","If reproducible, capture the wrapped error (%w cause) and report it — a failing WriteHeader into a bytes.Buffer usually indicates an SDK/library version issue","Pin/upgrade github.com/archive/tar (stdlib) and the Docker SDK to compatible versions and rebuild the backend"],"exampleFix":"// before\nfileDescriptor := &tar.Header{Name: filename, Mode: 0600, Size: int64(len(content))}\nif err := archiveWriter.WriteHeader(fileDescriptor); err != nil {\n    return fmt.Errorf(\"tar archive header generation failed: %w\", err)\n}\n// after\nif len(content) < 0 { // defensive guard\n    return fmt.Errorf(\"content size must be non-negative, got %d\", len(content))\n}\nfileDescriptor := &tar.Header{Name: filename, Mode: 0600, Size: int64(len(content))}\nif err := archiveWriter.WriteHeader(fileDescriptor); err != nil {\n    return fmt.Errorf(\"tar archive header generation failed: %w\", err)\n}","handlingStrategy":"validation","validationCode":"if len(content) > 64<<20 {\n    return fmt.Errorf(\"refusing to write %d bytes: too large\", len(content))\n}","typeGuard":null,"tryCatchPattern":"if _, err := term.WriteFile(ctx, flowID, content, path); err != nil {\n    if strings.Contains(err.Error(), \"tar archive header generation failed\") {\n        // log wrapped cause via errors.Unwrap and retry once\n    }\n}","preventionTips":["Keep write payloads modest; chunk very large content","Monitor backend memory; tar buffering is fully in-memory","Report deterministic WriteHeader failures to maintainers — they indicate library-level issues"],"tags":["docker","tar","file-write"],"backgroundTag":"tar-archive-write-failed","analyzedSha":"ea665308baaff015b226f308438a68d929d0f29b","analyzedAt":"2026-09-01T14:16:31.421Z","contentChangedAt":null,"schemaVersion":2},"datasetVersion":"2026-09-08T10:18:20.063Z"}