diff --git a/framework/IO/Util/TStreamHelper.php b/framework/IO/Util/TStreamHelper.php
index 3adab446a..e5f687866 100644
--- a/framework/IO/Util/TStreamHelper.php
+++ b/framework/IO/Util/TStreamHelper.php
@@ -16,8 +16,14 @@
  * TStreamHelper class.
  *
  * Static utilities over a PSR-7 {@see StreamInterface}, for operations the interface itself
- * does not provide: copying one stream into another, hashing a stream's contents, and reading
- * a single line.  They work on any StreamInterface, not just {@see \Prado\IO\TStream}.
+ * does not provide: copying a stream into a string or another stream, hashing a stream's
+ * contents, and reading a single line.  They work on any StreamInterface, not just
+ * {@see \Prado\IO\TStream}.
+ *
+ * The copies and the hash move {@see CHUNK_SIZE} bytes per pass, so a body larger than
+ * memory streams through without materializing.  Mapping a file name or extension to its
+ * media type is {@see \Prado\Web\TMediaType::mimeTypeFromFilename()}, with the media
+ * types themselves.
  *
  * @author Brad Anderson <belisoful@icloud.com>
  * @since 4.4.0
@@ -27,12 +33,37 @@ class TStreamHelper
 	/** @var int The chunk size used when copying and hashing. */
 	public const CHUNK_SIZE = 8192;
 
+	/**
+	 * Reads a stream from its current position into a string, optionally size-bounded.
+	 * @param StreamInterface $stream The stream to read.
+	 * @param int $maxLength The maximum number of bytes to read, or -1 for all remaining. Default -1.
+	 * @return string The bytes read.
+	 */
+	public static function copyToString(StreamInterface $stream, int $maxLength = -1): string
+	{
+		$buffer = '';
+		while (!$stream->eof()) {
+			$want = $maxLength === -1 ? static::CHUNK_SIZE : min(static::CHUNK_SIZE, $maxLength - strlen($buffer));
+			if ($want <= 0) {
+				break;
+			}
+			$chunk = $stream->read($want);
+			if ($chunk === '') {
+				break;
+			}
+			$buffer .= $chunk;
+		}
+		return $buffer;
+	}
+
 	/**
 	 * Copies bytes from one stream to another, reading from the source's current position and
-	 * writing at the destination's current position.
+	 * writing at the destination's current position.  Each chunk is written completely,
+	 * looping over short writes, so the destination never receives a torn copy.
 	 * @param StreamInterface $source The stream to read from.
 	 * @param StreamInterface $dest The stream to write to.
 	 * @param int $maxLength The maximum number of bytes to copy, or -1 for all remaining. Default -1.
+	 * @throws \RuntimeException When the destination stops accepting bytes mid-copy.
 	 * @return int The number of bytes copied.
 	 */
 	public static function copyToStream(StreamInterface $source, StreamInterface $dest, int $maxLength = -1): int
@@ -47,7 +78,16 @@ public static function copyToStream(StreamInterface $source, StreamInterface $de
 			if ($chunk === '') {
 				break;
 			}
-			$copied += $dest->write($chunk);
+			$offset = 0;
+			$length = strlen($chunk);
+			while ($offset < $length) {
+				$written = $dest->write($offset === 0 ? $chunk : substr($chunk, $offset));
+				if ($written <= 0) {
+					throw new \RuntimeException('copyToStream destination stopped accepting bytes at ' . ($copied + $offset));
+				}
+				$offset += $written;
+			}
+			$copied += $length;
 		}
 		return $copied;
 	}
diff --git a/framework/Web/TMediaType.php b/framework/Web/TMediaType.php
index bcb7e71ef..9bf3e944e 100644
--- a/framework/Web/TMediaType.php
+++ b/framework/Web/TMediaType.php
@@ -58,7 +58,8 @@
  *
  * *Application:* {@see JSON}, {@see JSON_LD}, {@see XML}, {@see XHTML},
  * {@see FORM}, {@see OCTET_STREAM}, {@see PDF}, {@see ZIP},
- * {@see GZIP}, {@see TAR}, {@see BZIP2}, {@see XZ}, {@see RTF}, {@see WASM}
+ * {@see GZIP}, {@see TAR}, {@see BZIP2}, {@see XZ}, {@see SEVEN_ZIP},
+ * {@see RAR}, {@see ZSTD}, {@see RTF}, {@see WASM}, {@see EPUB}
  *
  * *Multipart:* {@see MULTIPART}
  *
@@ -70,18 +71,28 @@
  * *CSP / Reporting API:* {@see CSP_REPORT}, {@see REPORTS_JSON}
  *
  * *Image:* {@see PNG}, {@see JPEG}, {@see GIF}, {@see WEBP}, {@see AVIF},
- * {@see SVG}, {@see ICON}, {@see BMP}, {@see TIFF}
+ * {@see SVG}, {@see ICON}, {@see BMP}, {@see TIFF}, {@see APNG}
  *
  * *Audio:* {@see AUDIO_MPEG}, {@see AUDIO_OGG}, {@see AUDIO_WAV},
- * {@see AUDIO_WEBM}, {@see AUDIO_AAC}
+ * {@see AUDIO_WEBM}, {@see AUDIO_AAC}, {@see AUDIO_FLAC}
  *
- * *Video:* {@see VIDEO_MP4}, {@see VIDEO_WEBM}, {@see VIDEO_OGG}
+ * *Video:* {@see VIDEO_MP4}, {@see VIDEO_WEBM}, {@see VIDEO_OGG},
+ * {@see VIDEO_MPEG}, {@see VIDEO_QUICKTIME}, {@see VIDEO_AVI}, {@see VIDEO_MATROSKA}
  *
- * *Font:* {@see WOFF}, {@see WOFF2}, {@see TTF}, {@see OTF}
+ * *Font:* {@see WOFF}, {@see WOFF2}, {@see TTF}, {@see OTF}, {@see EOT}
  *
  * *Defaults:* {@see DEFAULT_TYPE} (`'text'`), {@see DEFAULT_SUBTYPE} (`'html'`) —
  * override in a subclass to change the no-argument default.
  *
+ * **File extension lookup.** {@see mimeTypeFromFilename()} and
+ * {@see mimeTypeFromExtension()} map a file name or extension to its media type
+ * string through {@see EXTENSION_MIME_TYPES}:
+ *
+ * ```php
+ * TMediaType::mimeTypeFromFilename('report.pdf');   // 'application/pdf'
+ * new TMediaType(TMediaType::mimeTypeFromExtension('json') ?? TMediaType::OCTET_STREAM);
+ * ```
+ *
  * **ArrayAccess.** Parameters are also accessible via array syntax via
  * {@see THeaderParametersTrait}, making `TMediaType` a transparent pipe to
  * its parameter map:
@@ -174,6 +185,15 @@ class TMediaType implements \ArrayAccess
 	/** `application/x-xz` — XZ/LZMA-compressed data (`.xz`, `.tar.xz`, `.txz`). */
 	public const XZ = 'application/x-xz';
 
+	/** `application/x-7z-compressed` — 7-Zip archive (`.7z`). */
+	public const SEVEN_ZIP = 'application/x-7z-compressed';
+
+	/** `application/vnd.rar` — RAR archive (`.rar`). */
+	public const RAR = 'application/vnd.rar';
+
+	/** `application/zstd` — Zstandard-compressed data (`.zst`, `.tar.zst`). */
+	public const ZSTD = 'application/zstd';
+
 	/** `application/ld+json` — JSON-LD structured data. */
 	public const JSON_LD = 'application/ld+json';
 
@@ -183,6 +203,9 @@ class TMediaType implements \ArrayAccess
 	/** `application/rtf` — Rich Text Format document. */
 	public const RTF = 'application/rtf';
 
+	/** `application/epub+zip` — EPUB electronic publication (`.epub`). */
+	public const EPUB = 'application/epub+zip';
+
 	// ---- Multipart ----
 
 	/** `multipart/form-data` — Multipart form upload (HTML forms with file input). */
@@ -271,6 +294,9 @@ class TMediaType implements \ArrayAccess
 	/** `image/tiff` — TIFF image. */
 	public const TIFF = 'image/tiff';
 
+	/** `image/apng` — Animated Portable Network Graphics (`.apng`). */
+	public const APNG = 'image/apng';
+
 	// ---- Audio ----
 
 	/** `audio/mpeg` — MP3 and other MPEG audio. */
@@ -288,6 +314,9 @@ class TMediaType implements \ArrayAccess
 	/** `audio/aac` — AAC audio. */
 	public const AUDIO_AAC = 'audio/aac';
 
+	/** `audio/flac` — Free Lossless Audio Codec (`.flac`). */
+	public const AUDIO_FLAC = 'audio/flac';
+
 	// ---- Video ----
 
 	/** `video/mp4` — MP4 video. */
@@ -299,6 +328,18 @@ class TMediaType implements \ArrayAccess
 	/** `video/ogg` — Ogg video. */
 	public const VIDEO_OGG = 'video/ogg';
 
+	/** `video/mpeg` — MPEG-1/2 video (`.mpeg`, `.mpg`). */
+	public const VIDEO_MPEG = 'video/mpeg';
+
+	/** `video/quicktime` — QuickTime video (`.mov`). */
+	public const VIDEO_QUICKTIME = 'video/quicktime';
+
+	/** `video/x-msvideo` — Audio Video Interleave (`.avi`). */
+	public const VIDEO_AVI = 'video/x-msvideo';
+
+	/** `video/x-matroska` — Matroska multimedia container (`.mkv`). */
+	public const VIDEO_MATROSKA = 'video/x-matroska';
+
 	// ---- Font ----
 
 	/** `font/woff` — Web Open Font Format. */
@@ -313,6 +354,9 @@ class TMediaType implements \ArrayAccess
 	/** `font/otf` — OpenType font. */
 	public const OTF = 'font/otf';
 
+	/** `application/vnd.ms-fontobject` — Embedded OpenType font (`.eot`). */
+	public const EOT = 'application/vnd.ms-fontobject';
+
 	// ---- Defaults ----
 
 	/**
@@ -329,6 +373,77 @@ class TMediaType implements \ArrayAccess
 	 */
 	public const DEFAULT_SUBTYPE = 'html';
 
+	/**
+	 * The lowercased file extension to media type map, used by
+	 * {@see mimeTypeFromExtension()} and {@see mimeTypeFromFilename()}. Entries reference
+	 * the named constants above where one exists, so each media type string is defined once.
+	 * @var array<string, string>
+	 */
+	protected const EXTENSION_MIME_TYPES = [
+		'7z' => self::SEVEN_ZIP,
+		'aac' => self::AUDIO_AAC,
+		'apng' => self::APNG,
+		'avi' => self::VIDEO_AVI,
+		'avif' => self::AVIF,
+		'bmp' => self::BMP,
+		'bz2' => self::BZIP2,
+		'css' => self::CSS,
+		'csv' => self::CSV,
+		'doc' => self::DOC,
+		'docx' => self::DOCX,
+		'eot' => self::EOT,
+		'epub' => self::EPUB,
+		'flac' => self::AUDIO_FLAC,
+		'gif' => self::GIF,
+		'gz' => self::GZIP,
+		'htm' => self::HTML,
+		'html' => self::HTML,
+		'ico' => self::ICON,
+		'ics' => self::CALENDAR,
+		'jpeg' => self::JPEG,
+		'jpg' => self::JPEG,
+		'js' => self::JAVASCRIPT,
+		'json' => self::JSON,
+		'jsonld' => self::JSON_LD,
+		'md' => self::MARKDOWN,
+		'mjs' => self::JAVASCRIPT,
+		'mkv' => self::VIDEO_MATROSKA,
+		'mov' => self::VIDEO_QUICKTIME,
+		'mp3' => self::AUDIO_MPEG,
+		'mp4' => self::VIDEO_MP4,
+		'mpeg' => self::VIDEO_MPEG,
+		'oga' => self::AUDIO_OGG,
+		'ogg' => self::AUDIO_OGG,
+		'ogv' => self::VIDEO_OGG,
+		'otf' => self::OTF,
+		'pdf' => self::PDF,
+		'png' => self::PNG,
+		'ppt' => self::PPT,
+		'pptx' => self::PPTX,
+		'rar' => self::RAR,
+		'rtf' => self::RTF,
+		'svg' => self::SVG,
+		'tar' => self::TAR,
+		'tif' => self::TIFF,
+		'tiff' => self::TIFF,
+		'ttf' => self::TTF,
+		'txt' => self::PLAIN,
+		'wasm' => self::WASM,
+		'wav' => self::AUDIO_WAV,
+		'weba' => self::AUDIO_WEBM,
+		'webm' => self::VIDEO_WEBM,
+		'webp' => self::WEBP,
+		'woff' => self::WOFF,
+		'woff2' => self::WOFF2,
+		'xhtml' => self::XHTML,
+		'xls' => self::XLS,
+		'xlsx' => self::XLSX,
+		'xml' => self::XML,
+		'xz' => self::XZ,
+		'zip' => self::ZIP,
+		'zst' => self::ZSTD,
+	];
+
 	// =========================================================================
 	// Backing fields
 	// =========================================================================
@@ -380,6 +495,30 @@ public function __construct(?string $mediaType = null)
 		}
 	}
 
+	// =========================================================================
+	// File extension lookup
+	// =========================================================================
+
+	/**
+	 * Maps a file name to its media type string by extension.
+	 * @param string $filename the file name or path.
+	 * @return ?string the media type string, or `null` when the extension is unknown.
+	 */
+	public static function mimeTypeFromFilename(string $filename): ?string
+	{
+		return static::mimeTypeFromExtension(pathinfo($filename, PATHINFO_EXTENSION));
+	}
+
+	/**
+	 * Maps a file extension to its media type string via {@see EXTENSION_MIME_TYPES}.
+	 * @param string $extension the extension, with or without a leading dot, any case.
+	 * @return ?string the media type string, or `null` when the extension is unknown.
+	 */
+	public static function mimeTypeFromExtension(string $extension): ?string
+	{
+		return static::EXTENSION_MIME_TYPES[strtolower(ltrim($extension, '.'))] ?? null;
+	}
+
 	// =========================================================================
 	// Type / Subtype / MimeType
 	// =========================================================================
diff --git a/tests/unit/IO/Util/TStreamHelperTest.php b/tests/unit/IO/Util/TStreamHelperTest.php
index fdcd822cf..a69df0dce 100644
--- a/tests/unit/IO/Util/TStreamHelperTest.php
+++ b/tests/unit/IO/Util/TStreamHelperTest.php
@@ -1,5 +1,7 @@
 <?php
 
+use Prado\IO\Stream\TFnStream;
+use Prado\IO\Stream\TPumpStream;
 use Prado\IO\TStream;
 use Prado\IO\Util\TStreamHelper;
 
@@ -66,4 +68,70 @@ public function testReadLineRespectsMaxLength()
 		$s = TStream::fromString("abcdef\n");
 		self::assertSame('abc', TStreamHelper::readLine($s, 4), 'Reads up to maxLength - 1 bytes.');
 	}
+
+	public function testReadLineOnANonSeekableStreamDoesNotOvershoot()
+	{
+		$pump = new TPumpStream(function (int $n) {
+			static $data = "line1\nline2\n";
+			$chunk = substr($data, 0, $n);
+			$data = substr($data, $n);
+			return $chunk;
+		});
+		self::assertSame("line1\n", TStreamHelper::readLine($pump));
+		self::assertSame("line2\n", TStreamHelper::readLine($pump), 'Byte-wise reads leave the next line intact.');
+	}
+
+	// ---- copyToString ---------------------------------------------------------
+
+	public function testCopyToStringReadsAllAndSpansChunks()
+	{
+		$data = random_bytes(3 * TStreamHelper::CHUNK_SIZE + 123);
+		self::assertSame($data, TStreamHelper::copyToString(TStream::fromString($data)));
+	}
+
+	public function testCopyToStringHonorsMaxLengthAndPosition()
+	{
+		$s = TStream::fromString('hello helper world');
+		self::assertSame('hello', TStreamHelper::copyToString($s, 5));
+		self::assertSame(' helper', TStreamHelper::copyToString($s, 7), 'The copy resumes at the stream position.');
+		self::assertSame(' world', TStreamHelper::copyToString($s), 'Unbounded reads the remainder.');
+	}
+
+	// ---- copy/hash robustness -------------------------------------------------
+
+	public function testCopyToStreamLoopsOverShortWrites()
+	{
+		// A destination accepting one byte per call; the copy must still land completely.
+		$sink = '';
+		$dest = new TFnStream([
+			'isWritable' => fn () => true,
+			'write' => function (string $bytes) use (&$sink) {
+				$sink .= $bytes[0];
+				return 1;
+			},
+		]);
+		self::assertSame(6, TStreamHelper::copyToStream(TStream::fromString('abcdef'), $dest));
+		self::assertSame('abcdef', $sink, 'Short writes are retried until the chunk lands.');
+	}
+
+	public function testCopyToStreamThrowsWhenTheDestinationStops()
+	{
+		$dest = new TFnStream([
+			'isWritable' => fn () => true,
+			'write' => fn () => 0,
+		]);
+		self::expectException(\RuntimeException::class);
+		TStreamHelper::copyToStream(TStream::fromString('abc'), $dest);
+	}
+
+	public function testHashNonSeekableFromCurrentPosition()
+	{
+		$parts = ['alpha', 'beta', ''];
+		$i = 0;
+		$pump = new TPumpStream(function () use (&$parts, &$i) {
+			return $parts[$i++] ?? '';
+		});
+		self::assertSame(hash('crc32b', 'alphabeta'), TStreamHelper::hash($pump, 'crc32b'), 'A non-seekable stream hashes from its current position.');
+	}
+
 }
diff --git a/tests/unit/Web/TMediaTypeTest.php b/tests/unit/Web/TMediaTypeTest.php
index 4dc52baa6..50ddb4093 100644
--- a/tests/unit/Web/TMediaTypeTest.php
+++ b/tests/unit/Web/TMediaTypeTest.php
@@ -366,7 +366,7 @@ public function testSubclassDefaultsUsedWhenNoArgConstructed(): void
 	{
 		// A subclass that overrides both DEFAULT_TYPE and DEFAULT_SUBTYPE must have
 		// its constants picked up via static:: in the constructor.
-		$sub = new class extends TMediaType {
+		$sub = new class () extends TMediaType {
 			public const DEFAULT_TYPE = 'application';
 			public const DEFAULT_SUBTYPE = 'json';
 		};
@@ -378,7 +378,7 @@ public function testSubclassDefaultsUsedWhenNoArgConstructed(): void
 	public function testSubclassDefaultTypeOverrideAlone(): void
 	{
 		// Only DEFAULT_TYPE overridden — DEFAULT_SUBTYPE falls back to the base value.
-		$sub = new class extends TMediaType {
+		$sub = new class () extends TMediaType {
 			public const DEFAULT_TYPE = 'image';
 		};
 		$this->assertSame('image', $sub->getType());
@@ -388,7 +388,7 @@ public function testSubclassDefaultTypeOverrideAlone(): void
 	public function testSubclassExplicitArgOverridesDefaults(): void
 	{
 		// When an explicit media type is passed, it must win over the subclass defaults.
-		$sub = new class('text/plain') extends TMediaType {
+		$sub = new class ('text/plain') extends TMediaType {
 			public const DEFAULT_TYPE = 'application';
 			public const DEFAULT_SUBTYPE = 'json';
 		};
@@ -398,7 +398,7 @@ public function testSubclassExplicitArgOverridesDefaults(): void
 
 	public function testSubclassNoArgConstructorHasNoParameters(): void
 	{
-		$sub = new class extends TMediaType {
+		$sub = new class () extends TMediaType {
 			public const DEFAULT_TYPE = 'application';
 			public const DEFAULT_SUBTYPE = 'xml';
 		};
@@ -1439,4 +1439,90 @@ public function testOffsetSetCoercesIntegerValueToString(): void
 		$mt['charset'] = 42;
 		$this->assertSame('42', $mt->getCharset());
 	}
+
+	// -----------------------------------------------------------------------
+	// File extension lookup
+	// -----------------------------------------------------------------------
+
+	public function testMimeTypeFromExtension(): void
+	{
+		$this->assertSame(TMediaType::PDF, TMediaType::mimeTypeFromExtension('pdf'));
+		$this->assertSame(TMediaType::JPEG, TMediaType::mimeTypeFromExtension('.JPG'), 'A leading dot and any case are accepted.');
+		$this->assertSame(TMediaType::GZIP, TMediaType::mimeTypeFromExtension('gz'));
+		$this->assertNull(TMediaType::mimeTypeFromExtension('nope'));
+		$this->assertNull(TMediaType::mimeTypeFromExtension(''));
+	}
+
+	public function testMimeTypeFromFilename(): void
+	{
+		$this->assertSame(TMediaType::HTML, TMediaType::mimeTypeFromFilename('/var/www/index.html'));
+		$this->assertSame(TMediaType::ZIP, TMediaType::mimeTypeFromFilename('archive.tar.zip'), 'The last extension decides.');
+		$this->assertNull(TMediaType::mimeTypeFromFilename('README'));
+	}
+
+	public function testExtensionLookupConstructsAMediaType(): void
+	{
+		$mt = new TMediaType(TMediaType::mimeTypeFromFilename('data.json'));
+		$this->assertSame('application', $mt->getType());
+		$this->assertSame('json', $mt->getSubtype());
+	}
+
+	// -----------------------------------------------------------------------
+	// Named constants — extension-lookup additions
+	// -----------------------------------------------------------------------
+
+	public function testConstantSevenZip(): void
+	{
+		$this->assertSame('application/x-7z-compressed', TMediaType::SEVEN_ZIP);
+	}
+
+	public function testConstantRar(): void
+	{
+		$this->assertSame('application/vnd.rar', TMediaType::RAR);
+	}
+
+	public function testConstantZstd(): void
+	{
+		$this->assertSame('application/zstd', TMediaType::ZSTD);
+	}
+
+	public function testConstantEpub(): void
+	{
+		$this->assertSame('application/epub+zip', TMediaType::EPUB);
+	}
+
+	public function testConstantApng(): void
+	{
+		$this->assertSame('image/apng', TMediaType::APNG);
+	}
+
+	public function testConstantAudioFlac(): void
+	{
+		$this->assertSame('audio/flac', TMediaType::AUDIO_FLAC);
+	}
+
+	public function testConstantVideoMpeg(): void
+	{
+		$this->assertSame('video/mpeg', TMediaType::VIDEO_MPEG);
+	}
+
+	public function testConstantVideoQuicktime(): void
+	{
+		$this->assertSame('video/quicktime', TMediaType::VIDEO_QUICKTIME);
+	}
+
+	public function testConstantVideoAvi(): void
+	{
+		$this->assertSame('video/x-msvideo', TMediaType::VIDEO_AVI);
+	}
+
+	public function testConstantVideoMatroska(): void
+	{
+		$this->assertSame('video/x-matroska', TMediaType::VIDEO_MATROSKA);
+	}
+
+	public function testConstantEot(): void
+	{
+		$this->assertSame('application/vnd.ms-fontobject', TMediaType::EOT);
+	}
 }