fix: align theme truecolor detection

packages/coding-agent/src/modes/interactive/theme/theme.ts

@@ -1,6 +1,12 @@
 import * as fs from "node:fs";
 import * as path from "node:path";
-import type { EditorTheme, MarkdownTheme, SelectListTheme } from "@earendil-works/pi-tui";
+import {
+	type EditorTheme,
+	getCapabilities,
+	type MarkdownTheme,
+	type SelectListTheme,
+	type SettingsListTheme,
+} from "@earendil-works/pi-tui";
 import chalk from "chalk";
 import { type Static, Type } from "typebox";
 import { Compile } from "typebox/compile";
@@ -158,33 +164,6 @@ type ColorMode = "truecolor" | "256color";
 // Color Utilities
 // ============================================================================
 
-function detectColorMode(): ColorMode {
-	const colorterm = process.env.COLORTERM;
-	if (colorterm === "truecolor" || colorterm === "24bit") {
-		return "truecolor";
-	}
-	// Windows Terminal supports truecolor
-	if (process.env.WT_SESSION) {
-		return "truecolor";
-	}
-	const term = process.env.TERM || "";
-	// Fall back to 256color for truly limited terminals
-	if (term === "dumb" || term === "" || term === "linux") {
-		return "256color";
-	}
-	// Terminal.app also doesn't support truecolor
-	if (process.env.TERM_PROGRAM === "Apple_Terminal") {
-		return "256color";
-	}
-	// GNU screen doesn't support truecolor unless explicitly opted in via COLORTERM=truecolor.
-	// TERM under screen is typically "screen", "screen-256color", or "screen.xterm-256color".
-	if (term === "screen" || term.startsWith("screen-") || term.startsWith("screen.")) {
-		return "256color";
-	}
-	// Assume truecolor for everything else - virtually all modern terminals support it
-	return "truecolor";
-}
-
 function hexToRgb(hex: string): { r: number; g: number; b: number } {
 	const cleaned = hex.replace("#", "");
 	if (cleaned.length !== 6) {
@@ -585,7 +564,7 @@ function loadThemeJson(name: string): ThemeJson {
 }
 
 function createTheme(themeJson: ThemeJson, mode?: ColorMode, sourcePath?: string): Theme {
-	const colorMode = mode ?? detectColorMode();
+	const colorMode = mode ?? (getCapabilities().trueColor ? "truecolor" : "256color");
 	const resolvedColors = resolveThemeColors(themeJson.colors, themeJson.vars);
 	const fgColors: Record<ThemeColor, string | number> = {} as Record<ThemeColor, string | number>;
 	const bgColors: Record<ThemeBg, string | number> = {} as Record<ThemeBg, string | number>;
@@ -1227,7 +1206,7 @@ export function getEditorTheme(): EditorTheme {
 	};
 }
 
-export function getSettingsListTheme(): import("@earendil-works/pi-tui").SettingsListTheme {
+export function getSettingsListTheme(): SettingsListTheme {
 	return {
 		label: (text: string, selected: boolean) => (selected ? theme.fg("accent", text) : text),
 		value: (text: string, selected: boolean) => (selected ? theme.fg("accent", text) : theme.fg("muted", text)),

packages/coding-agent/test/theme-detection.test.ts

@@ -1,10 +1,16 @@
-import { describe, expect, it } from "vitest";
+import { resetCapabilitiesCache, setCapabilities } from "@earendil-works/pi-tui";
+import { afterEach, describe, expect, it } from "vitest";
 import {
 	detectTerminalBackground,
+	getThemeByName,
 	getThemeForRgbColor,
 	parseOsc11BackgroundColor,
 } from "../src/modes/interactive/theme/theme.js";
 
+afterEach(() => {
+	resetCapabilitiesCache();
+});
+
 describe("detectTerminalBackground", () => {
 	it("uses the COLORFGBG background color index", () => {
 		expect(detectTerminalBackground({ env: { COLORFGBG: "0;15" } })).toMatchObject({
@@ -32,6 +38,22 @@ describe("detectTerminalBackground", () => {
 	});
 });
 
+describe("theme color mode", () => {
+	it("uses terminal capabilities", () => {
+		setCapabilities({ images: null, trueColor: false, hyperlinks: false });
+		const ansi256Theme = getThemeByName("dark");
+		if (!ansi256Theme) throw new Error("dark theme not found");
+		expect(ansi256Theme.getColorMode()).toBe("256color");
+		expect(ansi256Theme.getFgAnsi("accent")).toMatch(/^\x1b\[38;5;\d+m$/);
+
+		setCapabilities({ images: null, trueColor: true, hyperlinks: false });
+		const truecolorTheme = getThemeByName("dark");
+		if (!truecolorTheme) throw new Error("dark theme not found");
+		expect(truecolorTheme.getColorMode()).toBe("truecolor");
+		expect(truecolorTheme.getFgAnsi("accent")).toMatch(/^\x1b\[38;2;\d+;\d+;\d+m$/);
+	});
+});
+
 describe("parseOsc11BackgroundColor", () => {
 	it("parses 16-bit OSC 11 rgb responses", () => {
 		expect(parseOsc11BackgroundColor("\x1b]11;rgb:0000/8000/ffff\x07")).toEqual({ r: 0, g: 128, b: 255 });

packages/tui/src/terminal-image.ts

@@ -43,6 +43,7 @@ export function detectCapabilities(): TerminalCapabilities {
 	const termProgram = process.env.TERM_PROGRAM?.toLowerCase() || "";
 	const term = process.env.TERM?.toLowerCase() || "";
 	const colorTerm = process.env.COLORTERM?.toLowerCase() || "";
+	const hasTrueColorHint = colorTerm === "truecolor" || colorTerm === "24bit";
 
 	// tmux and screen swallow OSC 8 by default (passthrough is opt-in and wraps
 	// sequences differently). Force hyperlinks off whenever we detect them, even
@@ -50,8 +51,7 @@ export function detectCapabilities(): TerminalCapabilities {
 	// also unreliable under tmux/screen, so leave `images: null` for safety.
 	const inTmuxOrScreen = !!process.env.TMUX || term.startsWith("tmux") || term.startsWith("screen");
 	if (inTmuxOrScreen) {
-		const trueColor = colorTerm === "truecolor" || colorTerm === "24bit";
-		return { images: null, trueColor, hyperlinks: false };
+		return { images: null, trueColor: hasTrueColorHint, hyperlinks: false };
 	}
 
 	if (process.env.KITTY_WINDOW_ID || termProgram === "kitty") {
@@ -82,8 +82,7 @@ export function detectCapabilities(): TerminalCapabilities {
 	// text" on terminals that swallow it, which means the URL disappears from
 	// the rendered output. Default to the legacy `text (url)` behavior unless we
 	// have positively identified a hyperlink-capable terminal above.
-	const trueColor = colorTerm === "truecolor" || colorTerm === "24bit";
-	return { images: null, trueColor, hyperlinks: false };
+	return { images: null, trueColor: hasTrueColorHint || !!process.env.WT_SESSION, hyperlinks: false };
 }
 
 export function getCapabilities(): TerminalCapabilities {

packages/tui/test/terminal-image.test.ts

@@ -27,6 +27,7 @@ const ENV_KEYS = [
 	"GHOSTTY_RESOURCES_DIR",
 	"WEZTERM_PANE",
 	"ITERM_SESSION_ID",
+	"WT_SESSION",
 	"CMUX_WORKSPACE_ID",
 ] as const;
 
@@ -271,6 +272,31 @@ describe("detectCapabilities", () => {
 			assert.strictEqual(caps.hyperlinks, true);
 		});
 	});
+
+	it("detects truecolor for Windows Terminal outside multiplexers", () => {
+		withEnv({ WT_SESSION: "session", TERM: "xterm-256color" }, () => {
+			const caps = detectCapabilities();
+			assert.strictEqual(caps.trueColor, true);
+		});
+	});
+
+	it("does not inherit Windows Terminal truecolor through tmux", () => {
+		withEnv({ WT_SESSION: "session", TMUX: "/tmp/tmux-1000/default,1234,0", TERM: "tmux-256color" }, () => {
+			const caps = detectCapabilities();
+			assert.strictEqual(caps.trueColor, false);
+			assert.strictEqual(caps.hyperlinks, false);
+			assert.strictEqual(caps.images, null);
+		});
+	});
+
+	it("trusts explicit truecolor hints through tmux", () => {
+		withEnv({ COLORTERM: "truecolor", TMUX: "/tmp/tmux-1000/default,1234,0", TERM: "tmux-256color" }, () => {
+			const caps = detectCapabilities();
+			assert.strictEqual(caps.trueColor, true);
+			assert.strictEqual(caps.hyperlinks, false);
+			assert.strictEqual(caps.images, null);
+		});
+	});
 });
 
 describe("Kitty image cursor movement", () => {