diff --git a/src/modules/editor/lib/dotenv.test.ts b/src/modules/editor/lib/dotenv.test.ts
new file mode 100644
index 000000000..66e2a6823
--- /dev/null
+++ b/src/modules/editor/lib/dotenv.test.ts
@@ -0,0 +1,76 @@
+import { StringStream } from "@codemirror/language";
+import { describe, expect, it } from "vitest";
+import { dotenv } from "./dotenv";
+
+function tokenizeLine(line: string): Array<[string, string]> {
+  const state = dotenv.startState?.(2);
+  if (!state) throw new Error("dotenv parser has no start state");
+
+  const stream = new StringStream(line, 2, 2);
+  const tokens: Array<[string, string]> = [];
+
+  while (!stream.eol()) {
+    stream.start = stream.pos;
+    const style = dotenv.token(stream, state);
+    if (stream.pos === stream.start) {
+      throw new Error(`Parser did not advance at ${stream.pos}`);
+    }
+    if (style) tokens.push([stream.current(), style]);
+  }
+
+  return tokens;
+}
+
+describe("dotenv tokenizer", () => {
+  it("highlights exports, keys, values, and comments", () => {
+    expect(tokenizeLine("export API_URL=https://example.com # public")).toEqual(
+      [
+        ["export", "keyword"],
+        ["API_URL", "variableName.definition"],
+        ["=", "operator"],
+        ["https://example.com", "string"],
+        ["# public", "comment"],
+      ],
+    );
+  });
+
+  it("highlights variables inside double quoted values", () => {
+    const variableRef = "$" + "{DB_HOST}";
+
+    expect(
+      tokenizeLine(`DATABASE_URL="postgres://${variableRef}:5432/app"`),
+    ).toEqual([
+      ["DATABASE_URL", "variableName.definition"],
+      ["=", "operator"],
+      ['"', "string"],
+      ["postgres://", "string"],
+      [variableRef, "variableName.special"],
+      [":5432/app", "string"],
+      ['"', "string"],
+    ]);
+  });
+
+  it("keeps hashes inside unquoted values", () => {
+    expect(tokenizeLine("PASSWORD=abc#123")).toEqual([
+      ["PASSWORD", "variableName.definition"],
+      ["=", "operator"],
+      ["abc#123", "string"],
+    ]);
+  });
+
+  it("keeps hashes at the start of unquoted values", () => {
+    expect(tokenizeLine("KEY=#hash")).toEqual([
+      ["KEY", "variableName.definition"],
+      ["=", "operator"],
+      ["#hash", "string"],
+    ]);
+  });
+
+  it("highlights comments after empty values", () => {
+    expect(tokenizeLine("KEY= #comment")).toEqual([
+      ["KEY", "variableName.definition"],
+      ["=", "operator"],
+      ["#comment", "comment"],
+    ]);
+  });
+});
diff --git a/src/modules/editor/lib/dotenv.ts b/src/modules/editor/lib/dotenv.ts
new file mode 100644
index 000000000..0adb3d1c1
--- /dev/null
+++ b/src/modules/editor/lib/dotenv.ts
@@ -0,0 +1,146 @@
+import type { StreamParser, StringStream } from "@codemirror/language";
+
+type DotenvState = {
+  mode: "start" | "afterExport" | "afterKey" | "value";
+  quote: "'" | '"' | null;
+  valueStarted: boolean;
+  afterValueSpace: boolean;
+};
+
+function resetLine(state: DotenvState): void {
+  state.mode = "start";
+  state.quote = null;
+  state.valueStarted = false;
+  state.afterValueSpace = false;
+}
+
+function tokenVariable(stream: StringStream): string | null {
+  if (stream.next() !== "$") return null;
+
+  if (stream.eat("{")) {
+    stream.eatWhile(/[A-Za-z0-9_]/);
+    stream.eat("}");
+    return "variableName.special";
+  }
+
+  if (!stream.eat(/[A-Za-z_]/)) return "operator";
+  stream.eatWhile(/[A-Za-z0-9_]/);
+  return "variableName.special";
+}
+
+function tokenQuotedValue(
+  stream: StringStream,
+  state: DotenvState,
+): string | null {
+  if (stream.peek() === state.quote) {
+    stream.next();
+    state.quote = null;
+    state.mode = "value";
+    return "string";
+  }
+
+  if (state.quote === '"' && stream.peek() === "$") {
+    return tokenVariable(stream);
+  }
+
+  while (!stream.eol()) {
+    const ch = stream.peek();
+    if (ch === state.quote || (state.quote === '"' && ch === "$")) break;
+    stream.next();
+  }
+
+  return "string";
+}
+
+export const dotenv: StreamParser<DotenvState> = {
+  name: "dotenv",
+
+  startState() {
+    return {
+      mode: "start",
+      quote: null,
+      valueStarted: false,
+      afterValueSpace: false,
+    };
+  },
+
+  token(stream, state) {
+    if (stream.sol()) resetLine(state);
+    if (stream.eol()) return null;
+
+    if (state.quote) return tokenQuotedValue(stream, state);
+
+    if (stream.eatSpace()) {
+      if (state.mode === "value") {
+        state.afterValueSpace = true;
+      }
+      return null;
+    }
+
+    if (state.mode !== "value" && stream.peek() === "#") {
+      stream.skipToEnd();
+      return "comment";
+    }
+
+    if (
+      state.mode === "start" &&
+      stream.match(/^export(?=\s+[A-Za-z_])/, true)
+    ) {
+      state.mode = "afterExport";
+      return "keyword";
+    }
+
+    if (state.mode === "start" || state.mode === "afterExport") {
+      if (stream.match(/^[A-Za-z_][A-Za-z0-9_]*/, true)) {
+        state.mode = "afterKey";
+        return "variableName.definition";
+      }
+
+      stream.skipToEnd();
+      return "invalid";
+    }
+
+    if (state.mode === "afterKey") {
+      if (stream.eat("=")) {
+        state.mode = "value";
+        return "operator";
+      }
+
+      stream.skipToEnd();
+      return "invalid";
+    }
+
+    if (stream.peek() === "'" || stream.peek() === '"') {
+      state.quote = stream.next() as "'" | '"';
+      state.valueStarted = true;
+      state.afterValueSpace = false;
+      return "string";
+    }
+
+    if (stream.peek() === "$") {
+      state.valueStarted = true;
+      state.afterValueSpace = false;
+      return tokenVariable(stream);
+    }
+
+    if (state.afterValueSpace && stream.peek() === "#") {
+      stream.skipToEnd();
+      return "comment";
+    }
+
+    while (!stream.eol()) {
+      const ch = stream.peek();
+      if (ch === "$" || /\s/.test(ch ?? "")) break;
+      stream.next();
+    }
+
+    state.valueStarted = true;
+    state.afterValueSpace = false;
+    return "string";
+  },
+
+  languageData: {
+    closeBrackets: { brackets: ["'", '"'] },
+    commentTokens: { line: "#" },
+  },
+};
diff --git a/src/modules/editor/lib/languageResolver.ts b/src/modules/editor/lib/languageResolver.ts
index 2d4a67920..188755c19 100644
--- a/src/modules/editor/lib/languageResolver.ts
+++ b/src/modules/editor/lib/languageResolver.ts
@@ -6,6 +6,9 @@ type LanguageLoader = () => Promise<LoaderResult>;
 const rubyLoader: LanguageLoader = () =>
   import("@codemirror/legacy-modes/mode/ruby").then((m) => m.ruby);
 
+const dotenvLoader: LanguageLoader = () =>
+  import("./dotenv").then((m) => m.dotenv);
+
 const jsonLoader: LanguageLoader = () =>
   import("@codemirror/lang-json").then((m) => m.json());
 
@@ -53,6 +56,7 @@ const loaders: Record<string, LanguageLoader> = {
   rs: () => import("@codemirror/lang-rust").then((m) => m.rust()),
   go: () => import("@codemirror/lang-go").then((m) => m.go()),
   py: () => import("@codemirror/lang-python").then((m) => m.python()),
+  env: dotenvLoader,
   json: jsonLoader,
   jsonc: jsonLoader,
   json5: jsonLoader,
@@ -134,6 +138,11 @@ const filenameOverrides: Record<string, LanguageLoader> = {
   brewfile: rubyLoader,
 };
 
+function filenameLoader(base: string): LanguageLoader | undefined {
+  if (base === ".env" || base.startsWith(".env.")) return dotenvLoader;
+  return filenameOverrides[base];
+}
+
 function extOf(name: string): string | null {
   const lower = name.toLowerCase();
   const dot = lower.lastIndexOf(".");
@@ -154,7 +163,7 @@ const cache = new Map<string, Extension | null>();
 function cacheKey(filename: string): string | null {
   const lower = filename.toLowerCase();
   const base = lower.split("/").pop() ?? lower;
-  if (filenameOverrides[base]) return `name:${base}`;
+  if (filenameLoader(base)) return `name:${base}`;
   const ext = extOf(base);
   return ext ? `ext:${ext}` : null;
 }
@@ -174,7 +183,7 @@ export async function resolveLanguage(
 
   const lower = filename.toLowerCase();
   const base = lower.split("/").pop() ?? lower;
-  const loader = filenameOverrides[base] ?? loaders[extOf(base) ?? ""];
+  const loader = filenameLoader(base) ?? loaders[extOf(base) ?? ""];
   if (!loader) {
     cache.set(key, null);
     return null;