diff --git a/packages/lint/src/rules/media.test.ts b/packages/lint/src/rules/media.test.ts
index e5664c8cf3..fcdf3d0317 100644
--- a/packages/lint/src/rules/media.test.ts
+++ b/packages/lint/src/rules/media.test.ts
@@ -695,6 +695,31 @@ describe("media rules", () => {
     expect(findings.every((finding) => finding.fixHint?.includes("data-var-src"))).toBe(true);
   });
 
+  it.each([
+    {
+      script: `const target = document.getElementById("clip"); { const target = document.getElementById("poster"); target.src = "b.png"; } target.src = "b.mp4";`,
+      expected: ["clip"],
+    },
+    {
+      script: `const target = document.getElementById("clip"); function update(target) { target.src = "b.png"; }`,
+      expected: [],
+    },
+    {
+      script: `function updateVideo() { const target = document.getElementById("clip"); target.src = "b.mp4"; } function updateImage() { const target = document.getElementById("poster"); target.src = "b.png"; }`,
+      expected: ["clip"],
+    },
+  ])("checks the media source write in its own scope ($expected)", async ({ script, expected }) => {
+    const html = `<html><body><div data-composition-id="c1" data-width="1920" data-height="1080">
+      <video id="clip" src="a.mp4"></video><img id="poster" src="a.png">
+      <script>${script}</script></div></body></html>`;
+    const result = await lintHyperframeHtml(html);
+    expect(
+      result.findings
+        .filter((finding) => finding.code === "media_runtime_src_mutation")
+        .map((finding) => finding.elementId),
+    ).toEqual(expected);
+  });
+
   it("does not flag img or script src mutations", async () => {
     const html = `
 <html><body>
diff --git a/packages/parsers/src/mediaSrcMutation.test.ts b/packages/parsers/src/mediaSrcMutation.test.ts
new file mode 100644
index 0000000000..be5db2bc95
--- /dev/null
+++ b/packages/parsers/src/mediaSrcMutation.test.ts
@@ -0,0 +1,113 @@
+import { describe, expect, it } from "vitest";
+import { extractMediaSrcMutations } from "./mediaSrcMutation.js";
+
+describe("extractMediaSrcMutations", () => {
+  it.each([
+    {
+      label: "block",
+      script: `const media = document.getElementById("video"); { const media = document.getElementById("image"); media.src = "image.png"; } media.src = "new.mp4";`,
+    },
+    {
+      label: "sibling functions",
+      script: `function updateImage() { const media = document.getElementById("image"); media.src = "image.png"; } function updateVideo() { const media = document.getElementById("video"); media.src = "new.mp4"; }`,
+    },
+    {
+      label: "arrow function",
+      script: `const media = document.getElementById("video"); const updateImage = () => { const media = document.getElementById("image"); media.src = "image.png"; }; media.src = "new.mp4";`,
+    },
+  ])("keeps $label bindings separate", ({ script }) => {
+    expect(extractMediaSrcMutations(script).map((mutation) => mutation.selector)).toEqual([
+      "#image",
+      "#video",
+    ]);
+  });
+
+  it.each([
+    {
+      label: "parameter",
+      script: `const media = document.getElementById("video"); function update(media) { media.src = "image.png"; } media.src = "new.mp4";`,
+    },
+    {
+      label: "destructured parameter",
+      script: `const media = document.getElementById("video"); function update({ media }) { media.src = "image.png"; } media.src = "new.mp4";`,
+    },
+    {
+      label: "unknown local",
+      script: `const media = document.getElementById("video"); { const media = findImage(); media.src = "image.png"; } media.src = "new.mp4";`,
+    },
+    {
+      label: "destructured local",
+      script: `const media = document.getElementById("video"); { const { media } = assets; media.src = "image.png"; } media.src = "new.mp4";`,
+    },
+    {
+      label: "catch parameter",
+      script: `const media = document.getElementById("video"); try { update(); } catch(media) { media.src = "image.png"; } media.src = "new.mp4";`,
+    },
+    {
+      label: "loop variable",
+      script: `const media = document.getElementById("video"); for (const media of images) { media.src = "image.png"; } media.src = "new.mp4";`,
+    },
+  ])("does not inherit an outer target through a $label", ({ script }) => {
+    expect(extractMediaSrcMutations(script)).toEqual([
+      { selector: "#video", operation: "src_assignment", raw: `media.src = "new.mp4"` },
+    ]);
+  });
+
+  it("resolves a closure and its scoped aliases", () => {
+    const script = `const media = document.getElementById("video"); { const alias = media; function update() { alias.setAttribute("src", "new.mp4"); } }`;
+    expect(extractMediaSrcMutations(script)).toEqual([
+      {
+        selector: "#video",
+        operation: "set_attribute",
+        raw: `alias.setAttribute("src", "new.mp4")`,
+      },
+    ]);
+  });
+
+  it("keeps var declarations in their enclosing function", () => {
+    const script = `function update() { { var media = document.getElementById("video"); } media.src = "new.mp4"; }`;
+    expect(extractMediaSrcMutations(script).map((mutation) => mutation.selector)).toEqual([
+      "#video",
+    ]);
+  });
+
+  it("retains a parameter that is redeclared and initialized with var", () => {
+    const script = `function update(media) { var media = document.getElementById("video"); media.src = "new.mp4"; }`;
+    expect(extractMediaSrcMutations(script).map((mutation) => mutation.selector)).toEqual([
+      "#video",
+    ]);
+  });
+
+  it("does not inherit an outer target through a named class expression", () => {
+    const script = `const media = document.getElementById("video"); const View = class media { update() { media.src = "not-a-video"; } }; media.src = "new.mp4";`;
+    expect(extractMediaSrcMutations(script).map((mutation) => mutation.selector)).toEqual([
+      "#video",
+    ]);
+  });
+
+  it("does not leak block declarations outside their scope", () => {
+    const script = `{ const media = document.getElementById("video"); } media.src = "new.mp4";`;
+    expect(extractMediaSrcMutations(script)).toEqual([]);
+  });
+
+  it("retains direct and computed DOM lookups", () => {
+    const script = `document["getElementById"]("video")["src"] = "new.mp4"; document.querySelector("#audio").setAttribute("SRC", "new.wav");`;
+    expect(extractMediaSrcMutations(script).map((mutation) => mutation.selector)).toEqual([
+      "#video",
+      "#audio",
+    ]);
+  });
+
+  it("keeps module parsing and rejects malformed scripts", () => {
+    expect(
+      extractMediaSrcMutations(
+        `export const media = document.getElementById("video"); media.src = "new.mp4";`,
+      ),
+    ).toHaveLength(1);
+    expect(extractMediaSrcMutations("const media = ;")).toEqual([]);
+  });
+
+  it("does not recurse through circular aliases", () => {
+    expect(extractMediaSrcMutations(`let a = b; let b = a; a.src = "new.mp4";`)).toEqual([]);
+  });
+});
diff --git a/packages/parsers/src/mediaSrcMutation.ts b/packages/parsers/src/mediaSrcMutation.ts
index 23812f8374..942ecfd437 100644
--- a/packages/parsers/src/mediaSrcMutation.ts
+++ b/packages/parsers/src/mediaSrcMutation.ts
@@ -7,7 +7,17 @@ export interface MediaSrcMutation {
   raw: string;
 }
 
-function parseProgram(script: string): any {
+interface Binding {
+  initializer: acorn.Expression | null;
+  scope: Scope;
+}
+
+interface Scope {
+  parent?: Scope;
+  bindings: Map<string, Binding>;
+}
+
+function parseProgram(script: string): acorn.Program {
   try {
     return acorn.parse(script, { ecmaVersion: "latest", sourceType: "script" });
   } catch {
@@ -15,28 +25,183 @@ function parseProgram(script: string): any {
   }
 }
 
-function literalString(node: any): string | undefined {
+function literalString(node: acorn.AnyNode | null | undefined): string | undefined {
   if (node?.type === "Literal" && typeof node.value === "string") return node.value;
-  if (node?.type === "TemplateLiteral" && node.expressions?.length === 0) {
-    return node.quasis?.[0]?.value?.cooked;
+  if (node?.type === "TemplateLiteral" && node.expressions.length === 0) {
+    return node.quasis[0]?.value.cooked ?? undefined;
   }
   return undefined;
 }
 
-function memberName(node: any): string | undefined {
+function memberName(node: acorn.AnyNode | null | undefined): string | undefined {
   if (node?.type !== "MemberExpression") return undefined;
-  if (!node.computed && node.property?.type === "Identifier") return node.property.name;
+  if (!node.computed && node.property.type === "Identifier") return node.property.name;
   return literalString(node.property);
 }
 
-function lookupSelector(node: any, bindings: ReadonlyMap<string, string>): string | undefined {
-  if (node?.type === "Identifier") return bindings.get(node.name);
-  if (node?.type !== "CallExpression" || node.callee?.type !== "MemberExpression") {
+function isFunctionScope(node: acorn.AnyNode): boolean {
+  return (
+    node.type === "Program" ||
+    node.type === "FunctionDeclaration" ||
+    node.type === "FunctionExpression" ||
+    node.type === "ArrowFunctionExpression" ||
+    node.type === "StaticBlock"
+  );
+}
+
+function isScope(node: acorn.AnyNode): boolean {
+  return (
+    isFunctionScope(node) ||
+    node.type === "BlockStatement" ||
+    node.type === "CatchClause" ||
+    node.type === "ForStatement" ||
+    node.type === "ForInStatement" ||
+    node.type === "ForOfStatement" ||
+    node.type === "SwitchStatement" ||
+    node.type === "ClassDeclaration" ||
+    node.type === "ClassExpression"
+  );
+}
+
+function declarePattern(
+  pattern: acorn.Pattern,
+  initializer: acorn.Expression | null,
+  scope: Scope,
+  initializerScope = scope,
+): void {
+  switch (pattern.type) {
+    case "Identifier":
+      if (initializer || !scope.bindings.has(pattern.name)) {
+        scope.bindings.set(pattern.name, { initializer, scope: initializerScope });
+      }
+      break;
+    case "RestElement":
+      declarePattern(pattern.argument, null, scope);
+      break;
+    case "AssignmentPattern":
+      declarePattern(pattern.left, null, scope);
+      break;
+    case "ArrayPattern":
+    case "ObjectPattern":
+      declarePatterns(destructuredPatterns(pattern), scope);
+      break;
+  }
+}
+
+function declarePatterns(patterns: readonly acorn.Pattern[], scope: Scope): void {
+  for (const pattern of patterns) declarePattern(pattern, null, scope);
+}
+
+function destructuredPatterns(pattern: acorn.ObjectPattern | acorn.ArrayPattern): acorn.Pattern[] {
+  if (pattern.type === "ObjectPattern") {
+    return pattern.properties.map((property) =>
+      property.type === "RestElement" ? property.argument : property.value,
+    );
+  }
+  return pattern.elements.filter((element): element is acorn.Pattern => element !== null);
+}
+
+function declareOptionalPattern(pattern: acorn.Pattern | null | undefined, scope: Scope): void {
+  if (pattern) declarePattern(pattern, null, scope);
+}
+
+function declareScopedName(node: acorn.AnyNode, scope: Scope): void {
+  switch (node.type) {
+    case "FunctionExpression":
+    case "FunctionDeclaration":
+      declareOptionalPattern(node.id, scope);
+      declarePatterns(node.params, scope);
+      break;
+    case "ArrowFunctionExpression":
+      declarePatterns(node.params, scope);
+      break;
+    case "ClassDeclaration":
+    case "ClassExpression":
+      declareOptionalPattern(node.id, scope);
+      break;
+    case "CatchClause":
+      declareOptionalPattern(node.param, scope);
+      break;
+    case "ImportDeclaration":
+      declarePatterns(
+        node.specifiers.map((specifier) => specifier.local),
+        scope,
+      );
+      break;
+  }
+}
+
+function lookupBinding(name: string, scope: Scope): Binding | undefined {
+  for (let current: Scope | undefined = scope; current; current = current.parent) {
+    const binding = current.bindings.get(name);
+    if (binding) return binding;
+  }
+  return undefined;
+}
+
+function collectBindings(
+  ast: acorn.Program,
+): (ancestors: readonly acorn.AnyNode[], functionOnly?: boolean) => Scope {
+  const root: Scope = { bindings: new Map() };
+  const scopes = new WeakMap<acorn.AnyNode, Scope>([[ast, root]]);
+  const scopeAt = (ancestors: readonly acorn.AnyNode[], functionOnly = false): Scope => {
+    let parent = root;
+    let selected = root;
+    for (const node of ancestors) {
+      if (!isScope(node)) continue;
+      let scope = scopes.get(node);
+      if (!scope) {
+        scope = { parent, bindings: new Map() };
+        scopes.set(node, scope);
+      }
+      parent = scope;
+      if (!functionOnly || isFunctionScope(node)) selected = scope;
+    }
+    return selected;
+  };
+
+  acornWalk.fullAncestor(ast, (node, _state, ancestors) => {
+    const scope = scopeAt(ancestors);
+    if (node.type === "VariableDeclarator") {
+      const declaration = ancestors.at(-2);
+      const bindingScope = scopeAt(
+        ancestors,
+        declaration?.type === "VariableDeclaration" && declaration.kind === "var",
+      );
+      declarePattern(node.id, node.init ?? null, bindingScope, scope);
+      return;
+    }
+    if ((node.type === "FunctionDeclaration" || node.type === "ClassDeclaration") && node.id) {
+      declarePattern(node.id, null, scopeAt(ancestors.slice(0, -1)));
+    }
+    declareScopedName(node, scope);
+  });
+  return scopeAt;
+}
+
+function lookupSelector(
+  node: acorn.Expression | acorn.Super | null | undefined,
+  scope: Scope,
+  seen = new Set<Binding>(),
+): string | undefined {
+  if (node?.type === "Identifier") {
+    const binding = lookupBinding(node.name, scope);
+    if (!binding || seen.has(binding)) return undefined;
+    seen.add(binding);
+    return lookupSelector(binding.initializer, binding.scope, seen);
+  }
+  return selectorFromDomLookup(node);
+}
+
+function selectorFromDomLookup(
+  node: acorn.Expression | acorn.Super | null | undefined,
+): string | undefined {
+  if (node?.type !== "CallExpression" || node.callee.type !== "MemberExpression") {
     return undefined;
   }
   const method = memberName(node.callee);
   if (method !== "getElementById" && method !== "querySelector") return undefined;
-  const value = literalString(node.arguments?.[0]);
+  const value = literalString(node.arguments[0]);
   if (!value) return undefined;
   return method === "getElementById" ? `#${value}` : value;
 }
@@ -45,20 +210,17 @@ function lookupSelector(node: any, bindings: ReadonlyMap<string, string>): strin
 export function extractMediaSrcMutations(script: string): MediaSrcMutation[] {
   try {
     const ast = parseProgram(script);
-    const bindings = new Map<string, string>();
-    acornWalk.simple(ast, {
-      VariableDeclarator(node: any) {
-        if (node.id?.type !== "Identifier") return;
-        const selector = lookupSelector(node.init, bindings);
-        if (selector) bindings.set(node.id.name, selector);
-      },
-    });
-
+    const scopeAt = collectBindings(ast);
     const mutations: MediaSrcMutation[] = [];
-    acornWalk.simple(ast, {
-      AssignmentExpression(node: any) {
-        if (node.operator !== "=" || memberName(node.left) !== "src") return;
-        const selector = lookupSelector(node.left.object, bindings);
+    acornWalk.ancestor(ast, {
+      AssignmentExpression(node, _state, ancestors) {
+        if (
+          node.operator !== "=" ||
+          node.left.type !== "MemberExpression" ||
+          memberName(node.left) !== "src"
+        )
+          return;
+        const selector = lookupSelector(node.left.object, scopeAt(ancestors));
         if (!selector) return;
         mutations.push({
           selector,
@@ -66,10 +228,11 @@ export function extractMediaSrcMutations(script: string): MediaSrcMutation[] {
           raw: script.slice(node.start, node.end),
         });
       },
-      CallExpression(node: any) {
-        if (memberName(node.callee) !== "setAttribute") return;
-        if (literalString(node.arguments?.[0])?.toLowerCase() !== "src") return;
-        const selector = lookupSelector(node.callee.object, bindings);
+      CallExpression(node, _state, ancestors) {
+        if (node.callee.type !== "MemberExpression" || memberName(node.callee) !== "setAttribute")
+          return;
+        if (literalString(node.arguments[0])?.toLowerCase() !== "src") return;
+        const selector = lookupSelector(node.callee.object, scopeAt(ancestors));
         if (!selector) return;
         mutations.push({
           selector,
diff --git a/packages/producer/src/services/render/stages/probeStage.test.ts b/packages/producer/src/services/render/stages/probeStage.test.ts
index cbd1a105d0..57e791e152 100644
--- a/packages/producer/src/services/render/stages/probeStage.test.ts
+++ b/packages/producer/src/services/render/stages/probeStage.test.ts
@@ -1034,6 +1034,45 @@ describe("runProbeStage — forceScreenshot threading", () => {
     expect(mediaPreflightComposition).toBe(input.composition);
   });
 
+  it("probes a video source write after an inner binding shadows its variable", async () => {
+    resetRetryMocks();
+    capturedCfgs.length = 0;
+    const { runProbeStage } = await import("./probeStage.js");
+    const input = makeProbeInput({});
+    input.composition.duration = 5;
+    input.composition.videos.push({
+      id: "clip",
+      src: "a.mp4",
+      start: 0,
+      end: 5,
+      mediaStart: 0,
+      loop: false,
+      hasAudio: false,
+    });
+    input.compiled.html = `<video id="clip" src="a.mp4"></video><img id="poster" src="a.png">
+      <script>const target = document.getElementById("clip");
+      { const target = document.getElementById("poster"); target.src = "b.png"; }
+      target.src = "b.mp4";</script>`;
+    browserMediaResults = [
+      {
+        id: "clip",
+        tagName: "video",
+        src: "b.mp4",
+        start: 0,
+        end: 5,
+        duration: 5,
+        mediaStart: 0,
+        loop: false,
+        hasAudio: false,
+        volume: 1,
+        muted: true,
+      },
+    ];
+    await runProbeStage(input);
+    expect(capturedCfgs.length).toBeGreaterThan(0);
+    expect(input.composition.videos[0]?.src).toBe("b.mp4");
+  });
+
   it("does not probe for img or script src mutations", async () => {
     resetRetryMocks();
     capturedCfgs.length = 0;