diff --git a/javascript/packages/analysis/src/index.ts b/javascript/packages/analysis/src/index.ts
index d3f509e06..f79042853 100644
--- a/javascript/packages/analysis/src/index.ts
+++ b/javascript/packages/analysis/src/index.ts
@@ -3,3 +3,4 @@ export * from "./partial-callers"
 export * from "./partial-resolution"
 export * from "./render-expression"
 export * from "./ancestor-attributes"
+export * from "./template-dependencies"
diff --git a/javascript/packages/analysis/src/render-call-collector.ts b/javascript/packages/analysis/src/render-call-collector.ts
new file mode 100644
index 000000000..78012a6d3
--- /dev/null
+++ b/javascript/packages/analysis/src/render-call-collector.ts
@@ -0,0 +1,62 @@
+import { Visitor, isERBRenderNode, isERBStrictLocalsNode, isRubyParameterNode, isRubyRenderLocalNode } from "@herb-tools/core"
+
+import type { ERBRenderNode, ERBStrictLocalsNode, Node } from "@herb-tools/core"
+
+export interface RenderCallDependency {
+  partial: string
+  locals: Record<string, string>
+  collection?: string
+}
+
+export class RenderCallCollector extends Visitor {
+  readonly renderCalls: RenderCallDependency[] = []
+  readonly localsReceived: Record<string, string> = {}
+  readonly localsDeclared = new Set<string>()
+
+  override visitChildNodes(node: Node): void {
+    if (isERBRenderNode(node)) this.collectRender(node)
+    if (isERBStrictLocalsNode(node)) this.collectDeclared(node)
+
+    super.visitChildNodes(node)
+  }
+
+  private collectRender(node: ERBRenderNode): void {
+    const keywords = node.keywords
+    if (!keywords) return
+
+    const locals: Record<string, string> = {}
+
+    for (const local of keywords.locals) {
+      if (!isRubyRenderLocalNode(local)) continue
+
+      const name = local.name?.value
+      const raw = local.value?.content
+
+      if (!name || raw === undefined || raw === null) continue
+
+      const value = raw === `${name}:` ? name : String(raw)
+
+      this.localsReceived[name] = value
+      locals[name] = value
+    }
+
+    const partial = keywords.partial?.value
+    if (!partial) return
+
+    this.renderCalls.push({
+      partial: String(partial).replace(/^["']|["']$/g, ""),
+      locals,
+      ...(keywords.collection?.value ? { collection: String(keywords.collection.value) } : {}),
+    })
+  }
+
+  private collectDeclared(node: ERBStrictLocalsNode): void {
+    for (const local of node.locals) {
+      if (!isRubyParameterNode(local)) continue
+
+      const name = local.name?.value
+
+      if (name) this.localsDeclared.add(name)
+    }
+  }
+}
diff --git a/javascript/packages/analysis/src/ruby-dependency-collector.ts b/javascript/packages/analysis/src/ruby-dependency-collector.ts
new file mode 100644
index 000000000..245a5ff7a
--- /dev/null
+++ b/javascript/packages/analysis/src/ruby-dependency-collector.ts
@@ -0,0 +1,68 @@
+import { PrismVisitor } from "@herb-tools/core"
+
+import type * as PrismNodes from "@ruby/prism/src/nodes.js"
+
+export class RubyDependencyCollector extends PrismVisitor {
+  readonly instanceVariables = new Set<string>()
+  readonly constants = new Set<string>()
+  readonly knownLocals = new Set<string>()
+  readonly bareCalls = new Set<string>()
+
+  override visitInstanceVariableReadNode(node: PrismNodes.InstanceVariableReadNode): void {
+    this.instanceVariables.add(String(node.name))
+
+    this.visitChildNodes(node)
+  }
+
+  override visitLocalVariableReadNode(node: PrismNodes.LocalVariableReadNode): void {
+    this.knownLocals.add(String(node.name))
+
+    this.visitChildNodes(node)
+  }
+
+  override visitLocalVariableWriteNode(node: PrismNodes.LocalVariableWriteNode): void {
+    this.bind(node.name, node)
+  }
+
+  override visitLocalVariableOrWriteNode(node: PrismNodes.LocalVariableOrWriteNode): void {
+    this.bind(node.name, node)
+  }
+
+  override visitLocalVariableAndWriteNode(node: PrismNodes.LocalVariableAndWriteNode): void {
+    this.bind(node.name, node)
+  }
+
+  override visitLocalVariableOperatorWriteNode(node: PrismNodes.LocalVariableOperatorWriteNode): void {
+    this.bind(node.name, node)
+  }
+
+  override visitBlockParameterNode(node: PrismNodes.BlockParameterNode): void {
+    if (node.name) this.knownLocals.add(String(node.name))
+
+    this.visitChildNodes(node)
+  }
+
+  override visitRequiredParameterNode(node: PrismNodes.RequiredParameterNode): void {
+    this.knownLocals.add(String(node.name))
+
+    this.visitChildNodes(node)
+  }
+
+  override visitCallNode(node: PrismNodes.CallNode): void {
+    const name = String(node.name)
+
+    if (node.receiver === null) {
+      this.bareCalls.add(name)
+    } else if (node.receiver.constructor.name === "ConstantReadNode") {
+      this.constants.add(`${String((node.receiver as PrismNodes.ConstantReadNode).name)}.${name}`)
+    }
+
+    this.visitChildNodes(node)
+  }
+
+  private bind(name: unknown, node: PrismNodes.Node): void {
+    this.knownLocals.add(String(name))
+
+    this.visitChildNodes(node)
+  }
+}
diff --git a/javascript/packages/analysis/src/template-dependencies.ts b/javascript/packages/analysis/src/template-dependencies.ts
new file mode 100644
index 000000000..dbda9f99b
--- /dev/null
+++ b/javascript/packages/analysis/src/template-dependencies.ts
@@ -0,0 +1,69 @@
+import { helperExists } from "@herb-tools/core"
+
+import { RubyDependencyCollector } from "./ruby-dependency-collector"
+import { RenderCallCollector } from "./render-call-collector"
+
+import type { DocumentNode, HerbBackend } from "@herb-tools/core"
+import type { RenderCallDependency } from "./render-call-collector"
+
+const PARSER_OPTIONS = { render_nodes: true, strict_locals: true, prism_nodes: true, prism_program: true, track_whitespace: true }
+
+export interface TemplateDependencies {
+  file: string
+  instanceVariables: string[]
+  constants: string[]
+  localsDeclared: string[]
+  localsReceived: Record<string, string>
+  renderCalls: RenderCallDependency[]
+  helperCalls: string[]
+  unknownCalls: string[]
+}
+
+export interface DependencyOptions {
+  customHelpers?: Iterable<string>
+}
+
+export function collectTemplateDependencies(backend: HerbBackend, file: string, source: string, options: DependencyOptions = {}): TemplateDependencies {
+  const custom = new Set(options.customHelpers ?? [])
+  const parsed = backend.parse(source, PARSER_OPTIONS)
+  const document = parsed.value as DocumentNode
+
+  const renders = new RenderCallCollector()
+  renders.visit(document)
+
+  const ruby = new RubyDependencyCollector()
+  const program = document.prismNode
+
+  if (program) {
+    ruby.visit(program)
+  }
+
+  const helperCalls = new Set<string>()
+  const unknownCalls = new Set<string>()
+
+  for (const name of ruby.bareCalls) {
+    if (helperExists(name) || custom.has(name)) {
+      helperCalls.add(name)
+
+      continue
+    }
+
+    if (name === "render") continue
+    if (ruby.knownLocals.has(name)) continue
+    if (name in renders.localsReceived) continue
+    if (renders.localsDeclared.has(name)) continue
+
+    unknownCalls.add(name)
+  }
+
+  return {
+    file,
+    instanceVariables: [...ruby.instanceVariables].sort(),
+    constants: [...ruby.constants].sort(),
+    localsDeclared: [...renders.localsDeclared].sort(),
+    localsReceived: renders.localsReceived,
+    renderCalls: renders.renderCalls,
+    helperCalls: [...helperCalls].sort(),
+    unknownCalls: [...unknownCalls].sort(),
+  }
+}
diff --git a/javascript/packages/analysis/test/template-dependencies.test.ts b/javascript/packages/analysis/test/template-dependencies.test.ts
new file mode 100644
index 000000000..4653bdf17
--- /dev/null
+++ b/javascript/packages/analysis/test/template-dependencies.test.ts
@@ -0,0 +1,141 @@
+import { describe, test, expect, beforeAll } from "vitest"
+
+import { Herb } from "@herb-tools/node-wasm"
+
+import { collectTemplateDependencies } from "../src/template-dependencies"
+
+import type { DependencyOptions, TemplateDependencies } from "../src/template-dependencies"
+
+describe("collectTemplateDependencies", () => {
+  beforeAll(async () => {
+    await Herb.load()
+  })
+
+  function analyze(source: string, options: DependencyOptions = {}): TemplateDependencies {
+    return collectTemplateDependencies(Herb, "app/views/posts/show.html.erb", source, options)
+  }
+
+  describe("instance variables", () => {
+    test("detects instance variables", () => {
+      const result = analyze(`<h1><%= @post.title %></h1><p><%= @user.name %></p>`)
+
+      expect(result.instanceVariables).toContain("@post")
+      expect(result.instanceVariables).toContain("@user")
+    })
+
+    test("detects instance variables in conditionals", () => {
+      expect(analyze(`<% if @admin %><p>Admin</p><% end %>`).instanceVariables).toContain("@admin")
+    })
+
+    test("detects instance variables inside string interpolation", () => {
+      expect(analyze(`<%= "Hello #{@name}" %>`).instanceVariables).toContain("@name")
+    })
+
+    test("detects multiple instance variables in a ternary", () => {
+      const result = analyze(`<%= @admin ? @admin_name : @guest_name %>`)
+
+      expect(result.instanceVariables).toEqual(expect.arrayContaining(["@admin", "@admin_name", "@guest_name"]))
+    })
+
+    test("deduplicates instance variables", () => {
+      expect(analyze(`<%= @post.title %><%= @post.body %>`).instanceVariables).toEqual(["@post"])
+    })
+  })
+
+  describe("constants", () => {
+    test("detects constants with method calls", () => {
+      const result = analyze(`<%= Current.user %><%= Post.count %>`)
+
+      expect(result.constants).toContain("Current.user")
+      expect(result.constants).toContain("Post.count")
+    })
+
+    test("detects constants in conditionals", () => {
+      expect(analyze(`<% if Current.user %><p>Logged in</p><% end %>`).constants).toContain("Current.user")
+    })
+  })
+
+  describe("locals", () => {
+    test("detects strict locals", () => {
+      const result = collectTemplateDependencies(Herb, "app/views/posts/_card.html.erb",
+        `<%# locals: (title:, body:) %>\n<h1><%= title %></h1>`)
+
+      expect(result.localsDeclared).toContain("title")
+      expect(result.localsDeclared).toContain("body")
+    })
+
+    test("does not flag declared locals as unknown", () => {
+      const result = collectTemplateDependencies(Herb, "app/views/posts/_card.html.erb",
+        `<%# locals: (title:) %>\n<%= title %>`)
+
+      expect(result.unknownCalls).toEqual([])
+      expect(result.localsDeclared).toContain("title")
+    })
+
+    test("detects locals passed to render calls", () => {
+      expect(analyze(`<%= render "shared/header", title: @post.title %>`).localsReceived.title).toBe("@post.title")
+    })
+
+    test("tracks instance variables from render local values", () => {
+      const result = analyze(`<%= render "shared/header", user: @current_user %>`)
+
+      expect(result.instanceVariables).toContain("@current_user")
+      expect(result.localsReceived.user).toBe("@current_user")
+    })
+  })
+
+  describe("helper and unknown calls", () => {
+    test("detects known Action View helpers", () => {
+      expect(analyze(`<%= link_to "Home", "/" %>`).helperCalls).toContain("link_to")
+    })
+
+    test("detects custom helpers once they are known", () => {
+      const result = analyze(`<%= markdown(@post.body) %>`, { customHelpers: ["markdown"] })
+
+      expect(result.helperCalls).toContain("markdown")
+      expect(result.unknownCalls).not.toContain("markdown")
+    })
+
+    test("flags unknown method calls", () => {
+      expect(analyze(`<%= current_user.name %>`).unknownCalls).toContain("current_user")
+    })
+
+    test("does not flag template defined locals as unknown", () => {
+      expect(analyze(`<% total = 1 %><%= total %>`).unknownCalls).not.toContain("total")
+    })
+
+    test("does not flag block parameters as unknown", () => {
+      expect(analyze(`<% @posts.each do |post| %><%= post.title %><% end %>`).unknownCalls).not.toContain("post")
+    })
+
+    test("does not flag nested block parameters as unknown", () => {
+      const source = `<% @posts.each do |post| %><% post.tags.each do |tag| %><%= tag.name %><% end %><% end %>`
+
+      expect(analyze(source).unknownCalls).not.toContain("tag")
+    })
+
+    test("conditional assignment registers as a local", () => {
+      expect(analyze(`<% total ||= 0 %><%= total %>`).unknownCalls).not.toContain("total")
+    })
+
+    test("operator assignment registers as a local", () => {
+      expect(analyze(`<% count = 0 %><% count += 1 %><%= count %>`).unknownCalls).not.toContain("count")
+    })
+  })
+
+  describe("render calls", () => {
+    test("tracks render calls with partials and locals", () => {
+      const [call] = analyze(`<%= render "shared/header", title: @post.title %>`).renderCalls
+
+      expect(call.partial).toBe("shared/header")
+      expect(call.locals.title).toBe("@post.title")
+    })
+
+    test("detects collection expression dependencies", () => {
+      const [call] = analyze(`<%= render partial: "posts/post", collection: @posts %>`).renderCalls
+
+      expect(call.partial).toBe("posts/post")
+      expect(call.collection).toBe("@posts")
+    })
+  })
+})