diff --git a/.changeset/afraid-garlics-visit.md b/.changeset/afraid-garlics-visit.md
new file mode 100644
index 0000000..1f82b95
--- /dev/null
+++ b/.changeset/afraid-garlics-visit.md
@@ -0,0 +1,6 @@
+---
+"@smoothtml/vite-plugin-sri": patch
+---
+
+Decode percent-encoded asset URLs before bundle lookup so encoded paths resolve
+correctly
diff --git a/.changeset/many-beans-cross.md b/.changeset/many-beans-cross.md
new file mode 100644
index 0000000..1633aec
--- /dev/null
+++ b/.changeset/many-beans-cross.md
@@ -0,0 +1,6 @@
+---
+"@smoothtml/vite-plugin-sri": minor
+---
+
+Add SRI hashes to elements that already have an `integrity` attribute,
+preserving existing hashes.
diff --git a/src/hash.ts b/src/hash.ts
new file mode 100644
index 0000000..296cdf4
--- /dev/null
+++ b/src/hash.ts
@@ -0,0 +1,14 @@
+// SPDX-FileCopyrightText: 2026 Rishvic Pushpakaran
+//
+// SPDX-License-Identifier: Apache-2.0
+
+const HASH_ORDER = ["sha256", "sha384", "sha512"] as const;
+export type HashAlgorithm = (typeof HASH_ORDER)[number];
+
+export function compareHash(a: HashAlgorithm, b: HashAlgorithm) {
+  return HASH_ORDER.indexOf(a) - HASH_ORDER.indexOf(b);
+}
+
+export function getComponentAlgo(component: string): HashAlgorithm | undefined {
+  return HASH_ORDER.find((h) => component.startsWith(`${h}-`));
+}
diff --git a/src/html-infra.ts b/src/html-infra.ts
new file mode 100644
index 0000000..3d10a9b
--- /dev/null
+++ b/src/html-infra.ts
@@ -0,0 +1,17 @@
+// SPDX-FileCopyrightText: 2026 Rishvic Pushpakaran
+//
+// SPDX-License-Identifier: Apache-2.0
+
+export const toAsciiLowercase = (s: string) =>
+  s.replace(/[A-Z]/g, (c) => c.toLowerCase());
+
+export const splitAsciiWhitespace = (s: string) =>
+  s.split(/[\t\n\f\r ]+/).filter(Boolean);
+
+type AttrDqUnsafeChar = '"' | "&";
+const ATTR_DQ_ESCAPES: Record<AttrDqUnsafeChar, string> = {
+  '"': "&quot;",
+  "&": "&amp;",
+};
+export const escapeAttribute = (s: string) =>
+  `"${s.replace(/["&]/g, (c) => ATTR_DQ_ESCAPES[c as AttrDqUnsafeChar])}"`;
diff --git a/src/inject.ts b/src/inject.ts
index 1b96aad..1899e76 100644
--- a/src/inject.ts
+++ b/src/inject.ts
@@ -6,12 +6,18 @@ import { createHash } from "crypto";
 import path from "path";
 import MagicString from "magic-string";
 import colors from "picocolors";
+import { compareHash, getComponentAlgo, type HashAlgorithm } from "./hash.ts";
 import { nodeIsElement, traverseHtml } from "./html.ts";
+import {
+  escapeAttribute,
+  splitAsciiWhitespace,
+  toAsciiLowercase,
+} from "./html-infra.ts";
 import type { OutputBundle } from "rolldown";
 import type { Logger } from "vite";
 
 export interface InjectSriOptions {
-  hashAlgorithm: "sha256" | "sha384" | "sha512";
+  hashAlgorithm: HashAlgorithm;
   bundle: OutputBundle;
   filename: string;
   htmlPath: string;
@@ -44,11 +50,6 @@ export async function injectSri(
       return;
     }
 
-    // Skip elements with integrity attribute present.
-    if (attrs.some((attr) => attr.name === "integrity")) {
-      return;
-    }
-
     const sourceAttrName = nodeName === "script" ? "src" : "href";
     const sourceAttr = attrs.find((attr) => attr.name === sourceAttrName);
     if (!sourceAttr) {
@@ -65,10 +66,26 @@ export async function injectSri(
     }
 
     // Sanitize empty pathnames, so paths are always absolute.
-    const basePath = baseUrl.pathname || "/";
-    const assetPath = assetUrl.pathname || "/";
+    let basePath: string, assetPath: string;
+    try {
+      basePath = decodeURI(baseUrl.pathname) || "/";
+      assetPath = decodeURI(assetUrl.pathname) || "/";
+    } catch (e) {
+      if (e instanceof URIError) {
+        opts.warn(
+          colors.yellow(
+            `\nInvalid URI (base: ${baseUrl.pathname}, asset: ${assetUrl.pathname}), skipping...`,
+          ),
+        );
+        return;
+      }
+      // Unknown error, rethrow.
+      throw new Error("Error while decoding base URL and asset URL", {
+        cause: e,
+      });
+    }
 
-    const assetFilePath = path.relative(basePath, assetPath);
+    const assetFilePath = path.posix.relative(basePath, assetPath);
     const asset = opts.bundle[assetFilePath];
     if (!asset) {
       opts.warn(
@@ -82,20 +99,69 @@ export async function injectSri(
     const hash = createHash(opts.hashAlgorithm);
     hash.update(data);
     const digest = hash.digest("base64");
+    const integrityComponent = `${opts.hashAlgorithm}-${digest}`;
 
-    const startTagEndOffset = sourceCodeLocation?.startTag?.endOffset;
-    if (startTagEndOffset === undefined) {
-      opts.warn(
-        colors.yellow(
-          `Unable to find source code location of <${nodeName} ${sourceAttrName}="${sourceAttr.value}">`,
-        ),
+    const integrityAttr = attrs.find((attr) => attr.name === "integrity");
+    if (!integrityAttr) {
+      const startTagEndOffset = sourceCodeLocation?.startTag?.endOffset;
+      if (startTagEndOffset === undefined) {
+        throw new Error(
+          "[vite-plugin-sri] internal error, no location set for start tag in element",
+        );
+      }
+      const appendOffset = html[startTagEndOffset - 2] === "/" ? 2 : 1;
+      s.appendRight(
+        startTagEndOffset - appendOffset,
+        ` integrity=${escapeAttribute(integrityComponent)}`,
+      );
+      return;
+    }
+
+    const components = splitAsciiWhitespace(integrityAttr.value);
+
+    // Skip when our hash is already present, or when a stronger algorithm is.
+    // Per the SRI spec the browser validates against the strongest algorithm in
+    // the set and ignores the rest, so appending a weaker hash alongside a
+    // stronger one would have no effect.
+    if (
+      components.some((c) => {
+        if (c === integrityComponent) {
+          return true;
+        }
+        const h = getComponentAlgo(c);
+        return h !== undefined && compareHash(h, opts.hashAlgorithm) > 0;
+      })
+    ) {
+      return;
+    }
+
+    const integritySourceCodeLocation =
+      node.sourceCodeLocation?.attrs?.["integrity"];
+    if (!integritySourceCodeLocation) {
+      throw new Error(
+        "[vite-plugin-sri] internal error, no location set for integrity attribute in element",
+      );
+    }
+
+    const updatedIntegrityValue = components
+      .concat([integrityComponent])
+      .join(" ");
+    const integrityString = s.slice(
+      integritySourceCodeLocation.startOffset,
+      integritySourceCodeLocation.endOffset,
+    );
+    const equalOffset = integrityString.search(/=/);
+    if (equalOffset < 0) {
+      s.appendRight(
+        integritySourceCodeLocation.endOffset,
+        `=${escapeAttribute(updatedIntegrityValue)}`,
       );
       return;
     }
-    const appendOffset = html[startTagEndOffset - 2] === "/" ? 2 : 1;
-    s.appendRight(
-      startTagEndOffset - appendOffset,
-      ` integrity="${opts.hashAlgorithm}-${digest}"`,
+    s.update(
+      integritySourceCodeLocation.startOffset + equalOffset + 1,
+      integritySourceCodeLocation.endOffset,
+      escapeAttribute(updatedIntegrityValue),
     );
   });
 
@@ -112,10 +178,7 @@ export async function injectSri(
  */
 export function isSriEligibleRel(rel: string) {
   const acceptedKeywords = ["stylesheet", "preload", "modulepreload"];
-  return rel
-    .split(/[\t\n\f\r ]+/)
-    .filter(Boolean)
-    .some((v) =>
-      acceptedKeywords.includes(v.replace(/[A-Z]/g, (c) => c.toLowerCase())),
-    );
+  return splitAsciiWhitespace(rel).some((v) =>
+    acceptedKeywords.includes(toAsciiLowercase(v)),
+  );
 }