diff --git a/packages/opencode/src/cli/cmd/tui/context/theme.tsx b/packages/opencode/src/cli/cmd/tui/context/theme.tsx
index 306c03825e39..9f3e9a308b60 100644
--- a/packages/opencode/src/cli/cmd/tui/context/theme.tsx
+++ b/packages/opencode/src/cli/cmd/tui/context/theme.tsx
@@ -40,6 +40,7 @@ import { useKV } from "./kv"
 import { useRenderer } from "@opentui/solid"
 import { createStore, produce } from "solid-js/store"
 import { Global } from "@opencode-ai/core/global"
+import { loadThemeFile } from "@/config/config"
 import { Filesystem } from "@/util/filesystem"
 import { useTuiConfig } from "./tui-config"
 import { isRecord } from "@/util/record"
@@ -484,6 +485,8 @@ export const { use: useTheme, provider: ThemeProvider } = createSimpleContext({
   },
 })
 
+const CUSTOM_THEME_GLOB = new Bun.Glob("themes/*.{json,jsonc}")
+
 async function getCustomThemes() {
   const directories = [
     Global.Path.config,
@@ -497,15 +500,15 @@ async function getCustomThemes() {
 
   const result: Record<string, ThemeJson> = {}
   for (const dir of directories) {
-    for (const item of await Glob.scan("themes/*.json", {
+    for (const item of await Glob.scan("themes/*.{json,jsonc}", {
       cwd: dir,
       absolute: true,
       dot: true,
       symlink: true,
     })) {
-      const name = path.basename(item, ".json")
-      const theme = await Filesystem.readJson(item)
-      if (isTheme(theme)) result[name] = theme
+      const ext = path.extname(item)
+      const name = path.basename(item, ext)
+      result[name] = await loadThemeFile(item)
     }
   }
   return result
diff --git a/packages/opencode/src/config/config.ts b/packages/opencode/src/config/config.ts
index 3a933f81e967..b37824ae4d55 100644
--- a/packages/opencode/src/config/config.ts
+++ b/packages/opencode/src/config/config.ts
@@ -10,7 +10,14 @@ import { NamedError } from "@opencode-ai/core/util/error"
 import { Flag } from "@opencode-ai/core/flag/flag"
 import { Auth } from "../auth"
 import { Env } from "../env"
-import { applyEdits, modify } from "jsonc-parser"
+import {
+  type ParseError as JsoncParseError,
+  applyEdits,
+  modify,
+  parse as parseJsonc,
+  printParseErrorCode,
+} from "jsonc-parser"
+import type { ThemeJson } from "../cli/cmd/tui/context/theme"
 import { type InstanceContext } from "../project/instance"
 import { InstallationLocal, InstallationVersion } from "@opencode-ai/core/installation/version"
 import { existsSync } from "fs"
@@ -26,6 +33,7 @@ import { zod } from "@/util/effect-zod"
 import { NonNegativeInt, PositiveInt, withStatics, type DeepMutable } from "@/util/schema"
 import { ConfigAgent } from "./agent"
 import { ConfigCommand } from "./command"
+import { JsonError } from "./error"
 import { ConfigFormatter } from "./formatter"
 import { ConfigLayout } from "./layout"
 import { ConfigLSP } from "./lsp"
@@ -311,6 +319,46 @@ function globalConfigFile() {
   return candidates[0]
 }
 
+export async function loadThemeFile(filepath: string): Promise<ThemeJson> {
+  log.info("loading theme", { path: filepath })
+  let text = await Bun.file(filepath)
+    .text()
+    .catch((err) => {
+      if (err.code === "ENOENT") return
+      throw new JsonError({ path: filepath }, { cause: err })
+    })
+  if (!text) {
+    throw new Error("Empty theme file")
+  }
+
+  const errors: JsoncParseError[] = []
+  const data = parseJsonc(text, errors, { allowTrailingComma: true })
+
+  if (errors.length) {
+    const lines = text.split("\n")
+    const errorDetails = errors
+      .map((e) => {
+        const beforeOffset = text.substring(0, e.offset).split("\n")
+        const line = beforeOffset.length
+        const column = beforeOffset[beforeOffset.length - 1].length + 1
+        const problemLine = lines[line - 1]
+
+        const error = `${printParseErrorCode(e.error)} at line ${line}, column ${column}`
+        if (!problemLine) return error
+
+        return `${error}\n   Line ${line}: ${problemLine}\n${"".padStart(column + 9)}^`
+      })
+      .join("\n")
+
+    throw new JsonError({
+      path: filepath,
+      message: `\n--- JSONC Input ---\n${text}\n--- Errors ---\n${errorDetails}\n--- End ---`,
+    })
+  }
+
+  return data as ThemeJson
+}
+
 function patchJsonc(input: string, patch: unknown, path: string[] = []): string {
   if (!isRecord(patch)) {
     const edits = modify(input, path, patch, {
diff --git a/packages/opencode/test/config/theme.test.ts b/packages/opencode/test/config/theme.test.ts
new file mode 100644
index 000000000000..16ebffc56abd
--- /dev/null
+++ b/packages/opencode/test/config/theme.test.ts
@@ -0,0 +1,115 @@
+import { describe, test, expect, beforeAll, afterAll } from "bun:test"
+import { tmpdir } from "os"
+import { join } from "path"
+import { loadThemeFile } from "../../src/config/config"
+import { writeFileSync, mkdirSync, rmSync } from "fs"
+
+describe("Theme Loading", () => {
+  let tempDir: string
+
+  beforeAll(() => {
+    tempDir = join(tmpdir(), "opencode-theme-test")
+    mkdirSync(tempDir, { recursive: true })
+  })
+
+  afterAll(() => {
+    rmSync(tempDir, { recursive: true, force: true })
+  })
+
+  test("should load JSONC theme file with comments", async () => {
+    const themeContent = `{
+  // This is a comment
+  "$schema": "https://opencode.ai/theme.json",
+  "theme": {
+    "primary": "#ff0000",
+    "secondary": "#00ff00"
+  }
+}`
+
+    const themeFile = join(tempDir, "test-theme.jsonc")
+    writeFileSync(themeFile, themeContent)
+
+    const theme = await loadThemeFile(themeFile)
+
+    expect(theme.theme.primary).toBe("#ff0000")
+    expect(theme.theme.secondary).toBe("#00ff00")
+  })
+
+  test("should NOT process environment variables in themes", async () => {
+    process.env.TEST_COLOR = "#00ff00"
+    const themeContent = `{
+  "theme": {
+    "primary": "{env:TEST_COLOR}",
+    "secondary": "#ff0000"
+  }
+}`
+
+    const themeFile = join(tempDir, "test-theme.jsonc")
+    writeFileSync(themeFile, themeContent)
+
+    const theme = await loadThemeFile(themeFile)
+
+    // Environment variable should NOT be processed in themes
+    expect(theme.theme.primary).toBe("{env:TEST_COLOR}")
+    expect(theme.theme.secondary).toBe("#ff0000")
+  })
+
+  test("should NOT process file inclusion in themes", async () => {
+    const colorFile = join(tempDir, "color.txt")
+    writeFileSync(colorFile, "#00ff00")
+
+    const themeContent = `{
+  "theme": {
+    "primary": "{file:color.txt}",
+    "secondary": "#ff0000"
+  }
+}`
+
+    const themeFile = join(tempDir, "test-theme.jsonc")
+    writeFileSync(themeFile, themeContent)
+
+    const theme = await loadThemeFile(themeFile)
+
+    // File inclusion should NOT be processed in themes
+    expect(theme.theme.primary).toBe("{file:color.txt}")
+    expect(theme.theme.secondary).toBe("#ff0000")
+  })
+
+  test("should handle trailing commas in JSONC themes", async () => {
+    const themeContent = `{
+  "theme": {
+    "primary": "#ff0000",
+    "secondary": "#00ff00", // Trailing comma
+  }
+}`
+
+    const themeFile = join(tempDir, "test-theme.jsonc")
+    writeFileSync(themeFile, themeContent)
+
+    const theme = await loadThemeFile(themeFile)
+
+    expect(theme.theme.primary).toBe("#ff0000")
+    expect(theme.theme.secondary).toBe("#00ff00")
+  })
+
+  test("should throw error for invalid JSONC theme", async () => {
+    const themeContent = `{
+  "theme": {
+    "primary": "#ff0000",
+    // Missing closing brace
+    "secondary": "#00ff00",
+  }`
+
+    const themeFile = join(tempDir, "test-theme.jsonc")
+    writeFileSync(themeFile, themeContent)
+
+    expect(loadThemeFile(themeFile)).rejects.toThrow()
+  })
+
+  test("should throw error for empty theme file", async () => {
+    const themeFile = join(tempDir, "empty-theme.jsonc")
+    writeFileSync(themeFile, "")
+
+    expect(loadThemeFile(themeFile)).rejects.toThrow("Empty theme file")
+  })
+})