Themes: Accept a dark/light theme table

.changeset/tidy-hounds-repeat.md

@@ -0,0 +1,5 @@
+---
+"hunkdiff": minor
+---
+
+Accept a `[theme]` table that names one theme per terminal background, so `dark` and `light` terminals each get a theme you chose instead of only Hunk's GitHub defaults. `fallback` covers terminals that never report a background.

docs/themes.md

@@ -18,6 +18,25 @@ Hunk chooses `github-light-default` for light backgrounds and
 `github-dark-default` for dark backgrounds, falling back to
 `github-dark-default` when the terminal does not answer.
 
+To pick the two themes yourself, write `theme` as a table instead of an id:
+
+```toml
+[theme]
+dark = "catppuccin-mocha"    # required
+light = "catppuccin-latte"   # required
+fallback = "github-dark-default"  # optional
+```
+
+Hunk queries the terminal background the same way `auto` does, then draws
+`dark` or `light`. `fallback` covers sessions where Hunk never gets an answer:
+terminals that ignore the query, and captured pager hosts such as LazyGit,
+where Hunk never asks. Without it those sessions use `dark`. Both sides accept
+any built-in id, a custom theme id, and the compatibility aliases.
+
+A `--theme <id>` flag overrides the table for that run, and picking a theme in
+the app (`t`, or `View -> Themes…`) replaces the pair with the single id you
+chose — the save-on-quit prompt shows that before writing anything.
+
 Older theme ids such as `graphite` and `paper` remain accepted as compatibility
 aliases.
 

src/app/startup.test.ts

@@ -641,6 +641,63 @@ describe("startup planning", () => {
     expect(opened).toBe(1);
   });
 
+  test("detects the terminal background for an adaptive theme pair", async () => {
+    const cliInput: CliInput = {
+      kind: "patch",
+      file: "-",
+      options: {
+        theme: { dark: "vitesse-dark", light: "one-light" },
+        pager: true,
+      },
+    };
+    const controllingTerminal = { stdin: {} as never, close: () => {} };
+    let probes = 0;
+
+    const plan = await prepareStartupPlan(["bun", "hunk", "patch", "-"], {
+      parseCliImpl: async () => cliInput as ParsedCliInput,
+      resolveRuntimeCliInputImpl: (input) => input,
+      resolveConfiguredCliInputImpl: (input) => createTestConfigResolution(input),
+      loadAppBootstrapImpl: async (input) => createBootstrap(input),
+      openControllingTerminalImpl: () => controllingTerminal,
+      detectTerminalThemeModeFromBackgroundImpl: async () => {
+        probes += 1;
+        return "light";
+      },
+      stdinIsTTY: false,
+      stdoutIsTTY: true,
+      stdout: { write: () => true } as never,
+    });
+
+    expect(plan).toMatchObject({ kind: "app", bootstrap: { initialThemeMode: "light" } });
+    expect(probes).toBe(1);
+  });
+
+  test("skips the background probe when one theme covers every terminal", async () => {
+    const cliInput: CliInput = {
+      kind: "patch",
+      file: "-",
+      options: { theme: "dracula", pager: true },
+    };
+    let probes = 0;
+
+    await prepareStartupPlan(["bun", "hunk", "patch", "-", "--theme", "dracula"], {
+      parseCliImpl: async () => cliInput as ParsedCliInput,
+      resolveRuntimeCliInputImpl: (input) => input,
+      resolveConfiguredCliInputImpl: (input) => createTestConfigResolution(input),
+      loadAppBootstrapImpl: async (input) => createBootstrap(input),
+      openControllingTerminalImpl: () => ({ stdin: {} as never, close: () => {} }),
+      detectTerminalThemeModeFromBackgroundImpl: async () => {
+        probes += 1;
+        return "dark";
+      },
+      stdinIsTTY: false,
+      stdoutIsTTY: true,
+      stdout: { write: () => true } as never,
+    });
+
+    expect(probes).toBe(0);
+  });
+
   test("opens the controlling terminal for piped patch startup", async () => {
     const cliInput: CliInput = {
       kind: "patch",

src/app/startup.ts

@@ -7,6 +7,7 @@ import type { loadAppBootstrap } from "../core/changeset/loaders";
 import { looksLikePatchInput } from "../core/process/pager";
 import { sanitizeTerminalText } from "../lib/terminalText";
 import { detectTerminalThemeModeFromBackground } from "../core/theme/detection";
+import { themeSelectionNeedsTerminalMode } from "../core/theme/selection";
 import {
   openControllingTerminal,
   resolveRuntimeCliInput,
@@ -485,7 +486,7 @@ export async function prepareStartupPlan(
   }
 
   let initialThemeMode: AppBootstrap["initialThemeMode"];
-  if (cliInput.options.theme === "auto" && stdoutIsTTY) {
+  if (themeSelectionNeedsTerminalMode(cliInput.options.theme) && stdoutIsTTY) {
     const themeInput = controllingTerminal?.stdin ?? (stdinIsTTY ? process.stdin : null);
     if (themeInput) {
       initialThemeMode =

src/core/bootstrap.ts

@@ -17,6 +17,7 @@ import type { CliInput, CursorLine, LayoutMode, SidebarVisibility } from "./run/
 import type { UserKeyBinding } from "./run/config";
 import type { StartupNotice } from "./process/startupNotice";
 import type { TerminalThemeMode } from "./theme/detection";
+import type { ThemeSelection } from "./theme/selection";
 import type { VcsCatalog } from "./vcs/types";
 
 /** Where a review was loaded from, retained so the session can reload and watch it. */
@@ -39,7 +40,7 @@ export interface AppBootstrap<ExtensionState = unknown> {
   reloadContext: ReloadContext;
   changeset: Changeset;
   initialMode: LayoutMode;
-  initialTheme?: string;
+  initialTheme?: ThemeSelection;
   initialThemeMode?: TerminalThemeMode;
   /** Selectable custom themes for this session, in menu order. */
   customThemes?: readonly NamedCustomThemeConfig[];

src/core/run/commandInputs.ts

@@ -14,6 +14,7 @@ import type {
   ExtensionVcsStashShowInput,
 } from "../../extension-api/types";
 import type { InstallSource } from "../install/installSource";
+import type { ThemeSelection } from "../theme/selection";
 
 export type LayoutMode = "auto" | "split" | "stack";
 export type CursorLine = "row" | "number" | "off";
@@ -24,7 +25,7 @@ export interface CommonOptions {
   mode?: LayoutMode;
   cursorLine?: CursorLine;
   vcs?: VcsMode;
-  theme?: string;
+  theme?: ThemeSelection;
   agentContext?: string;
   pager?: boolean;
   watch?: boolean;