diff --git a/apps/web/components/shared/markdown-components.test.tsx b/apps/web/components/shared/markdown-components.test.tsx
index 40fa6d9661..ab4e0fc1b2 100644
--- a/apps/web/components/shared/markdown-components.test.tsx
+++ b/apps/web/components/shared/markdown-components.test.tsx
@@ -1,8 +1,22 @@
 import type { ReactNode } from "react";
 import ReactMarkdown from "react-markdown";
 import { renderToStaticMarkup } from "react-dom/server";
-import { describe, expect, it, vi } from "vitest";
-import { markdownComponents, normalizeMarkdown, remarkPlugins } from "./markdown-components";
+import { fireEvent, render, screen } from "@testing-library/react";
+import { afterEach, describe, expect, it, vi } from "vitest";
+
+const openFile = vi.hoisted(() => vi.fn());
+const appState = vi.hoisted(() => ({
+  value: {
+    tasks: { activeSessionId: "session-1" },
+    taskSessions: {
+      items: {
+        "session-1": {
+          worktree_path: "/root/.kandev/tasks/example/kandev",
+        },
+      },
+    },
+  },
+}));
 
 vi.mock("@/components/shared/mermaid-block", () => ({
   MermaidBlock: ({ code }: { code: string }) => <div data-kind="mermaid">{code}</div>,
@@ -20,6 +34,16 @@ vi.mock("@/components/task/chat/messages/inline-code", () => ({
   InlineCode: ({ children }: { children: ReactNode }) => <code data-kind="inline">{children}</code>,
 }));
 
+vi.mock("@/hooks/use-panel-actions", () => ({
+  usePanelActions: () => ({ openFile }),
+}));
+
+vi.mock("@/components/state-provider", () => ({
+  useAppStore: (selector: (state: typeof appState.value) => unknown) => selector(appState.value),
+}));
+
+import { markdownComponents, normalizeMarkdown, remarkPlugins } from "./markdown-components";
+
 function renderMarkdown(source: string): string {
   return renderToStaticMarkup(
     <ReactMarkdown remarkPlugins={remarkPlugins} components={markdownComponents}>
@@ -28,7 +52,19 @@ function renderMarkdown(source: string): string {
   );
 }
 
+function Markdown({ children }: { children: string }) {
+  return (
+    <ReactMarkdown remarkPlugins={remarkPlugins} components={markdownComponents}>
+      {children}
+    </ReactMarkdown>
+  );
+}
+
 describe("markdownComponents", () => {
+  afterEach(() => {
+    openFile.mockClear();
+  });
+
   it("keeps mermaid keywords in inline code as inline code", () => {
     const html = renderMarkdown("Metadata comes from `kanban`, `kanbanMulti`, repositories.");
 
@@ -52,6 +88,40 @@ describe("markdownComponents", () => {
     expect(html).toContain("const source");
     expect(html).not.toContain('data-kind="mermaid"');
   });
+
+  it("opens absolute worktree file links in the editor", () => {
+    render(
+      <Markdown>
+        {"[spec.md](/root/.kandev/tasks/example/kandev/docs/specs/native/spec.md)"}
+      </Markdown>,
+    );
+
+    fireEvent.click(screen.getByRole("link", { name: "spec.md" }));
+
+    expect(openFile).toHaveBeenCalledWith("docs/specs/native/spec.md");
+  });
+
+  it("opens relative file links in the editor", () => {
+    render(<Markdown>{"[plan.md](docs/specs/native/plan.md)"}</Markdown>);
+
+    const link = screen.getByRole("link", { name: "plan.md" });
+    expect(link.getAttribute("target")).toBe("_self");
+
+    fireEvent.click(link);
+
+    expect(openFile).toHaveBeenCalledWith("docs/specs/native/plan.md");
+  });
+
+  it("does not treat bare domains as relative file links", () => {
+    render(<Markdown>{"[service](api.service.com)"}</Markdown>);
+
+    const link = screen.getByRole("link", { name: "service" });
+    link.addEventListener("click", (event) => event.preventDefault());
+    fireEvent.click(link);
+
+    expect(openFile).not.toHaveBeenCalled();
+    expect(link.getAttribute("target")).toBe("_blank");
+  });
 });
 
 describe("normalizeMarkdown", () => {
diff --git a/apps/web/components/shared/markdown-components.tsx b/apps/web/components/shared/markdown-components.tsx
index c912a7836b..47f8b38c91 100644
--- a/apps/web/components/shared/markdown-components.tsx
+++ b/apps/web/components/shared/markdown-components.tsx
@@ -1,6 +1,6 @@
 "use client";
 
-import { isValidElement, type ReactNode } from "react";
+import { createContext, isValidElement, useContext, type MouseEvent, type ReactNode } from "react";
 import remarkGfm from "remark-gfm";
 import remarkBreaks from "remark-breaks";
 import remarkGemoji from "remark-gemoji";
@@ -8,6 +8,8 @@ import { InlineCode } from "@/components/task/chat/messages/inline-code";
 import { CodeBlock } from "@/components/task/chat/messages/code-block";
 import { MermaidBlock } from "@/components/shared/mermaid-block";
 import { isMermaidContent } from "@/components/editors/tiptap/tiptap-mermaid-extension";
+import { usePanelActions } from "@/hooks/use-panel-actions";
+import { useAppStore } from "@/components/state-provider";
 
 /** Shared remark plugins used by all markdown renderers */
 // eslint-disable-next-line @typescript-eslint/no-explicit-any
@@ -49,10 +51,130 @@ type MarkdownCodeProps = {
   children?: ReactNode;
 };
 
+export type MarkdownFileLinkContextValue = {
+  worktreePath?: string | null;
+  onOpenFile?: (path: string) => void;
+};
+
+export const MarkdownFileLinkContext = createContext<MarkdownFileLinkContextValue>({});
+
 function isBlockCode(rawContent: string, hasLanguage: boolean): boolean {
   return hasLanguage || rawContent.includes("\n");
 }
 
+const WEB_TLD_EXTENSIONS = new Set(["ai", "app", "cloud", "co", "com", "dev", "io", "net", "org"]);
+
+function looksLikeFilePath(path: string): boolean {
+  const lastSegment = path.split("/").pop() ?? "";
+  if (!lastSegment.includes(".") || path.endsWith("/")) return false;
+  const extension = lastSegment.split(".").pop() ?? "";
+  if (!/^[a-z0-9]{1,8}$/i.test(extension)) return false;
+  return !WEB_TLD_EXTENSIONS.has(extension.toLowerCase());
+}
+
+function isExternalHref(href: string): boolean {
+  return /^[a-z][a-z\d+.-]*:/i.test(href) || href.startsWith("//");
+}
+
+function stripHashAndQuery(href: string): string {
+  return href.split(/[?#]/, 1)[0] ?? "";
+}
+
+function decodeHrefPath(href: string): string | null {
+  try {
+    return decodeURIComponent(stripHashAndQuery(href));
+  } catch {
+    return null;
+  }
+}
+
+function hasParentTraversal(path: string): boolean {
+  return path.split("/").includes("..");
+}
+
+function resolveMarkdownFileHref(
+  href: string | undefined,
+  worktreePath: string | null | undefined,
+) {
+  if (!href || href.startsWith("#") || isExternalHref(href)) return null;
+
+  const path = decodeHrefPath(href);
+  if (!path || path.startsWith("~/") || hasParentTraversal(path)) return null;
+
+  if (path.startsWith("/")) {
+    const normalizedRoot = worktreePath?.replace(/\\/g, "/").replace(/\/$/, "");
+    const normalizedPath = path.replace(/\\/g, "/");
+    if (!normalizedRoot || !normalizedPath.startsWith(`${normalizedRoot}/`)) return null;
+    const relativePath = normalizedPath.slice(normalizedRoot.length + 1);
+    return looksLikeFilePath(relativePath) ? relativePath : null;
+  }
+
+  const normalizedPath = path.replace(/\\/g, "/").replace(/^\.\//, "");
+  if (normalizedPath.startsWith("../")) return null;
+  return looksLikeFilePath(normalizedPath) ? normalizedPath : null;
+}
+
+type MarkdownLinkProps = {
+  href?: string;
+  children?: ReactNode;
+};
+
+function MarkdownFileAnchor({
+  href,
+  children,
+  worktreePath,
+  openFile,
+}: MarkdownLinkProps & {
+  worktreePath: string | null | undefined;
+  openFile: (path: string) => void;
+}) {
+  const filePath = resolveMarkdownFileHref(href, worktreePath);
+  const isInternal = !!filePath || href?.startsWith("/") || href?.startsWith("#");
+
+  const handleClick = filePath
+    ? (event: MouseEvent<HTMLAnchorElement>) => {
+        event.preventDefault();
+        openFile(filePath);
+      }
+    : undefined;
+
+  return (
+    <a
+      href={href}
+      target={isInternal ? "_self" : "_blank"}
+      rel={isInternal ? undefined : "noopener noreferrer"}
+      onClick={handleClick}
+    >
+      {children}
+    </a>
+  );
+}
+
+function MarkdownFallbackLink(props: MarkdownLinkProps) {
+  const { openFile } = usePanelActions();
+  const worktreePath = useAppStore((state) => {
+    const sessionId = state.tasks.activeSessionId;
+    if (!sessionId) return null;
+    return state.taskSessions.items[sessionId]?.worktree_path ?? null;
+  });
+
+  return <MarkdownFileAnchor {...props} worktreePath={worktreePath} openFile={openFile} />;
+}
+
+function MarkdownLink(props: MarkdownLinkProps) {
+  const linkContext = useContext(MarkdownFileLinkContext);
+  if (linkContext.onOpenFile) {
+    return (
+      <MarkdownFileAnchor
+        {...props}
+        worktreePath={linkContext.worktreePath}
+        openFile={linkContext.onOpenFile}
+      />
+    );
+  }
+  return <MarkdownFallbackLink {...props} />;
+}
+
 /**
  * Shared markdown component overrides for ReactMarkdown.
  * Element styles (headings, lists, inline code, etc.) are handled by
@@ -74,18 +196,7 @@ export const markdownComponents = {
     }
     return <InlineCode>{content}</InlineCode>;
   },
-  a: ({ href, children }: { href?: string; children?: ReactNode }) => {
-    const isInternal = href?.startsWith("/") || href?.startsWith("#");
-    return (
-      <a
-        href={href}
-        target={isInternal ? "_self" : "_blank"}
-        rel={isInternal ? undefined : "noopener noreferrer"}
-      >
-        {children}
-      </a>
-    );
-  },
+  a: MarkdownLink,
   table: ({ children }: { children?: ReactNode }) => (
     <div className="overflow-x-auto">
       <table>{children}</table>
diff --git a/apps/web/components/shared/memoized-markdown.test.tsx b/apps/web/components/shared/memoized-markdown.test.tsx
index 1b25558199..b94cdcf7a8 100644
--- a/apps/web/components/shared/memoized-markdown.test.tsx
+++ b/apps/web/components/shared/memoized-markdown.test.tsx
@@ -1,4 +1,4 @@
-import { useState } from "react";
+import { createContext, useState } from "react";
 import { fireEvent, render } from "@testing-library/react";
 import { afterEach, describe, expect, it, vi } from "vitest";
 
@@ -13,6 +13,7 @@ vi.mock("react-markdown", () => ({
 
 // Stub the component overrides so the test stays light (no shiki / mermaid).
 vi.mock("@/components/shared/markdown-components", () => ({
+  MarkdownFileLinkContext: createContext({}),
   markdownComponents: {},
   remarkPlugins: [],
 }));
diff --git a/apps/web/components/shared/memoized-markdown.tsx b/apps/web/components/shared/memoized-markdown.tsx
index 3aedf0002c..d2a3423e98 100644
--- a/apps/web/components/shared/memoized-markdown.tsx
+++ b/apps/web/components/shared/memoized-markdown.tsx
@@ -1,23 +1,40 @@
 "use client";
 
-import { memo } from "react";
+import { memo, useMemo } from "react";
 import ReactMarkdown from "react-markdown";
-import { markdownComponents, remarkPlugins } from "@/components/shared/markdown-components";
+import {
+  MarkdownFileLinkContext,
+  markdownComponents,
+  remarkPlugins,
+  type MarkdownFileLinkContextValue,
+} from "@/components/shared/markdown-components";
 import { normalizeCached } from "@/lib/markdown/normalize-cache";
 
 /**
  * Markdown renderer behind a `memo` boundary keyed on the `content` string.
  *
- * `content` is a primitive, so React compares it by value. Object-ref churn
- * from a message refetch can therefore never trigger a re-parse: an identical
- * string bails out of the memo and re-uses the previously parsed element tree.
- * The normalized string itself is also cached (LRU) so two messages with the
- * same content share a single normalize pass.
+ * `content` is a primitive, so React compares it by value. Keep optional
+ * file-link props stable at the caller when possible; identical props bail out
+ * of the memo and re-use the previously parsed element tree. The normalized
+ * string itself is also cached (LRU) so two messages with the same content
+ * share a single normalize pass.
  */
-export const MemoizedMarkdown = memo(function MemoizedMarkdown({ content }: { content: string }) {
+type MemoizedMarkdownProps = MarkdownFileLinkContextValue & {
+  content: string;
+};
+
+export const MemoizedMarkdown = memo(function MemoizedMarkdown({
+  content,
+  worktreePath,
+  onOpenFile,
+}: MemoizedMarkdownProps) {
+  const fileLinkContext = useMemo(() => ({ worktreePath, onOpenFile }), [worktreePath, onOpenFile]);
+
   return (
-    <ReactMarkdown remarkPlugins={remarkPlugins} components={markdownComponents}>
-      {normalizeCached(content)}
-    </ReactMarkdown>
+    <MarkdownFileLinkContext.Provider value={fileLinkContext}>
+      <ReactMarkdown remarkPlugins={remarkPlugins} components={markdownComponents}>
+        {normalizeCached(content)}
+      </ReactMarkdown>
+    </MarkdownFileLinkContext.Provider>
   );
 });
diff --git a/apps/web/components/task/chat/__evals__/render-cost.test.tsx b/apps/web/components/task/chat/__evals__/render-cost.test.tsx
index be0c1f8770..a37b852a20 100644
--- a/apps/web/components/task/chat/__evals__/render-cost.test.tsx
+++ b/apps/web/components/task/chat/__evals__/render-cost.test.tsx
@@ -7,7 +7,7 @@
  * update pattern. Wave 1 owns the parse-count assertions; Wave 2/3 extend the
  * row-render assertions once callbacks + store identity are stabilized.
  */
-import { memo, useState } from "react";
+import { createContext, memo, useState } from "react";
 import { act, fireEvent, render } from "@testing-library/react";
 import { beforeEach, describe, expect, it, vi } from "vitest";
 
@@ -16,6 +16,7 @@ vi.mock("react-markdown", () => ({
 }));
 
 vi.mock("@/components/shared/markdown-components", () => ({
+  MarkdownFileLinkContext: createContext({}),
   markdownComponents: {},
   remarkPlugins: [],
 }));
diff --git a/apps/web/components/task/chat/message-renderer.tsx b/apps/web/components/task/chat/message-renderer.tsx
index faa5a59d93..4b56f669b7 100644
--- a/apps/web/components/task/chat/message-renderer.tsx
+++ b/apps/web/components/task/chat/message-renderer.tsx
@@ -95,11 +95,15 @@ function TaskDescriptionMessage({
   comment,
   taskId,
   sessionId,
+  worktreePath,
+  onOpenFile,
   onScrollToMessage,
 }: {
   comment: Message;
   taskId?: string;
   sessionId?: string;
+  worktreePath?: string;
+  onOpenFile?: (path: string) => void;
   onScrollToMessage?: (messageId: string) => void;
 }) {
   const sessionState = useSessionStateValue(sessionId);
@@ -113,6 +117,8 @@ function TaskDescriptionMessage({
         className="bg-muted/40 text-foreground border-border/60"
         showRichBlocks={comment.type === "message" || comment.type === "content" || !comment.type}
         sessionId={sessionId}
+        worktreePath={worktreePath}
+        onOpenFile={onOpenFile}
         onScrollToMessage={onScrollToMessage}
       />
     );
@@ -126,6 +132,8 @@ function TaskDescriptionMessage({
         label="You"
         className="bg-primary/10 text-foreground border-primary/30"
         sessionId={sessionId}
+        worktreePath={worktreePath}
+        onOpenFile={onOpenFile}
         onScrollToMessage={onScrollToMessage}
       />
       {showStartButton && <TaskDescriptionStartButton taskId={taskId!} sessionId={sessionId!} />}
@@ -305,6 +313,8 @@ const adapters: MessageAdapter[] = [
             comment={comment}
             taskId={ctx.taskId}
             sessionId={ctx.sessionId}
+            worktreePath={ctx.worktreePath}
+            onOpenFile={ctx.onOpenFile}
             onScrollToMessage={ctx.onScrollToMessage}
           />
         );
@@ -316,6 +326,8 @@ const adapters: MessageAdapter[] = [
             label="You"
             className="bg-primary/10 text-foreground border-primary/30"
             sessionId={ctx.sessionId}
+            worktreePath={ctx.worktreePath}
+            onOpenFile={ctx.onOpenFile}
             onScrollToMessage={ctx.onScrollToMessage}
           />
         );
@@ -327,6 +339,8 @@ const adapters: MessageAdapter[] = [
           className="bg-muted/40 text-foreground border-border/60"
           showRichBlocks={comment.type === "message" || comment.type === "content" || !comment.type}
           sessionId={ctx.sessionId}
+          worktreePath={ctx.worktreePath}
+          onOpenFile={ctx.onOpenFile}
           onScrollToMessage={ctx.onScrollToMessage}
         />
       );
diff --git a/apps/web/components/task/chat/messages/chat-message.test.tsx b/apps/web/components/task/chat/messages/chat-message.test.tsx
index fb363cb81f..812763e234 100644
--- a/apps/web/components/task/chat/messages/chat-message.test.tsx
+++ b/apps/web/components/task/chat/messages/chat-message.test.tsx
@@ -203,6 +203,30 @@ describe("ChatMessage sender badge", () => {
 });
 
 describe("ChatMessage agent session config metadata", () => {
+  it("opens markdown file links with the provided chat file opener", () => {
+    const onOpenFile = vi.fn();
+    const Wrapper = wrapper([]);
+
+    render(
+      <Wrapper>
+        <ChatMessage
+          comment={userMessage({
+            author_type: "agent",
+            content: "[spec.md](/root/.kandev/tasks/example/kandev/docs/specs/native/spec.md)",
+          })}
+          label="Message"
+          className=""
+          worktreePath="/root/.kandev/tasks/example/kandev"
+          onOpenFile={onOpenFile}
+        />
+      </Wrapper>,
+    );
+
+    fireEvent.click(screen.getByRole("link", { name: "spec.md" }));
+
+    expect(onOpenFile).toHaveBeenCalledWith("docs/specs/native/spec.md");
+  });
+
   it("shows session config options next to the model", () => {
     renderAgentMessageWithSession({
       agent_profile_snapshot: {
diff --git a/apps/web/components/task/chat/messages/chat-message.tsx b/apps/web/components/task/chat/messages/chat-message.tsx
index bbadc6d55d..c8762b1c4f 100644
--- a/apps/web/components/task/chat/messages/chat-message.tsx
+++ b/apps/web/components/task/chat/messages/chat-message.tsx
@@ -23,6 +23,8 @@ type ChatMessageProps = {
   className: string;
   showRichBlocks?: boolean;
   sessionId?: string | null;
+  worktreePath?: string;
+  onOpenFile?: (path: string) => void;
   onScrollToMessage?: (messageId: string) => void;
 };
 
@@ -70,20 +72,32 @@ function renderContentWithFileRefs(content: string): React.ReactNode[] {
 
 // ── Markdown component overrides imported from shared/markdown-components ─────
 
-function renderUserMessageBody(
-  hasContent: boolean,
-  showRaw: boolean,
-  hasAttachments: boolean,
-  content: string,
-  rawContent?: string,
-): React.ReactNode {
+type UserMessageBodyOptions = {
+  hasContent: boolean;
+  showRaw: boolean;
+  hasAttachments: boolean;
+  content: string;
+  rawContent?: string;
+  worktreePath?: string;
+  onOpenFile?: (path: string) => void;
+};
+
+function renderUserMessageBody({
+  hasContent,
+  showRaw,
+  hasAttachments,
+  content,
+  rawContent,
+  worktreePath,
+  onOpenFile,
+}: UserMessageBodyOptions): React.ReactNode {
   if (hasContent && showRaw) {
     return <pre className="whitespace-pre-wrap font-mono text-xs">{rawContent || content}</pre>;
   }
   if (hasContent) {
     return (
       <div className="markdown-body markdown-body-user max-w-none">
-        <MemoizedMarkdown content={content} />
+        <MemoizedMarkdown content={content} worktreePath={worktreePath} onOpenFile={onOpenFile} />
       </div>
     );
   }
@@ -100,6 +114,8 @@ type UserMessageProps = {
   showRaw: boolean;
   onToggleRaw: () => void;
   sessionId?: string | null;
+  worktreePath?: string;
+  onOpenFile?: (path: string) => void;
   onScrollToMessage?: (messageId: string) => void;
 };
 
@@ -194,6 +210,8 @@ function UserMessageContent({
   showRaw,
   onToggleRaw,
   sessionId,
+  worktreePath,
+  onOpenFile,
   onScrollToMessage,
 }: UserMessageProps) {
   const userNavigation = useUserMessageNavigation(sessionId ?? null, comment.id);
@@ -242,13 +260,15 @@ function UserMessageContent({
               ))}
             </div>
           )}
-          {renderUserMessageBody(
+          {renderUserMessageBody({
             hasContent,
             showRaw,
             hasAttachments,
-            comment.content,
-            comment.raw_content,
-          )}
+            content: comment.content,
+            rawContent: comment.raw_content,
+            worktreePath,
+            onOpenFile,
+          })}
         </div>
         <MessageActions
           message={comment}
@@ -282,9 +302,18 @@ type AgentMessageProps = {
   showRaw: boolean;
   onToggleRaw: () => void;
   showRichBlocks?: boolean;
+  worktreePath?: string;
+  onOpenFile?: (path: string) => void;
 };
 
-function AgentMessageContent({ comment, showRaw, onToggleRaw, showRichBlocks }: AgentMessageProps) {
+function AgentMessageContent({
+  comment,
+  showRaw,
+  onToggleRaw,
+  showRichBlocks,
+  worktreePath,
+  onOpenFile,
+}: AgentMessageProps) {
   return (
     <div className="flex items-start gap-2 sm:gap-3 w-full group">
       <div className="flex-1 min-w-0">
@@ -294,7 +323,11 @@ function AgentMessageContent({ comment, showRaw, onToggleRaw, showRichBlocks }:
           </pre>
         ) : (
           <div className="markdown-body max-w-none">
-            <MemoizedMarkdown content={comment.content || "(empty)"} />
+            <MemoizedMarkdown
+              content={comment.content || "(empty)"}
+              worktreePath={worktreePath}
+              onOpenFile={onOpenFile}
+            />
             {showRichBlocks ? <RichBlocks comment={comment} /> : null}
           </div>
         )}
@@ -321,6 +354,8 @@ export const ChatMessage = memo(function ChatMessage({
   className,
   showRichBlocks,
   sessionId,
+  worktreePath,
+  onOpenFile,
   onScrollToMessage,
 }: ChatMessageProps) {
   const [showRaw, setShowRaw] = useState(false);
@@ -353,6 +388,8 @@ export const ChatMessage = memo(function ChatMessage({
         showRaw={showRaw}
         onToggleRaw={toggleRaw}
         sessionId={sessionId}
+        worktreePath={worktreePath}
+        onOpenFile={onOpenFile}
         onScrollToMessage={onScrollToMessage}
       />
     );
@@ -364,6 +401,8 @@ export const ChatMessage = memo(function ChatMessage({
       showRaw={showRaw}
       onToggleRaw={toggleRaw}
       showRichBlocks={showRichBlocks}
+      worktreePath={worktreePath}
+      onOpenFile={onOpenFile}
     />
   );
 });
diff --git a/apps/web/hooks/use-file-editors.build-state.test.ts b/apps/web/hooks/use-file-editors.build-state.test.ts
index d0ea66a9eb..108b31f201 100644
--- a/apps/web/hooks/use-file-editors.build-state.test.ts
+++ b/apps/web/hooks/use-file-editors.build-state.test.ts
@@ -47,7 +47,9 @@ describe("buildFileEditorState", () => {
 });
 
 describe("fetchFileEditorState", () => {
-  beforeEach(() => vi.clearAllMocks());
+  beforeEach(() => {
+    vi.clearAllMocks();
+  });
 
   it("returns the built state (with repo) when the session is unchanged", async () => {
     mockRequestFileContent.mockResolvedValueOnce(RESPONSE);