diff --git a/packages/coding-agent/CHANGELOG.md b/packages/coding-agent/CHANGELOG.md
index ee70e90fe..f50d9ffa9 100644
--- a/packages/coding-agent/CHANGELOG.md
+++ b/packages/coding-agent/CHANGELOG.md
@@ -119,6 +119,10 @@
 - Removed the `clearOnShrink` setting and its `PI_CLEAR_ON_SHRINK` environment variable: the rewritten renderer always clears shrunken rows exactly, so the flicker/perf tradeoff the setting controlled no longer exists. Existing config entries are ignored.
 - Removed the prompt-submit native-scrollback reconciliation checkpoint and the eager streaming render mode from the interactive controllers — the renderer's append-only contract made both obsolete.
 
+### Added
+
+- Added `python.interpreter` to pin eval's Python backend to an explicit interpreter and skip automatic runtime discovery ([#1802](https://github.com/can1357/oh-my-pi/issues/1802)).
+
 ## [15.10.9] - 2026-06-09
 
 ### Fixed
diff --git a/packages/coding-agent/src/config/settings-schema.ts b/packages/coding-agent/src/config/settings-schema.ts
index 7e7621a65..fa61ce50f 100644
--- a/packages/coding-agent/src/config/settings-schema.ts
+++ b/packages/coding-agent/src/config/settings-schema.ts
@@ -2100,6 +2100,16 @@ export const SETTINGS_SCHEMA = {
 			description: "Whether to keep IPython kernel alive across calls",
 		},
 	},
+	"python.interpreter": {
+		type: "string",
+		default: "",
+		ui: {
+			tab: "editing",
+			label: "Python Interpreter",
+			description:
+				"Optional path to an exact Python executable. When set, automatic Python runtime discovery is skipped.",
+		},
+	},
 
 	// ────────────────────────────────────────────────────────────────────────
 	// Tools
diff --git a/packages/coding-agent/src/eval/py/kernel.ts b/packages/coding-agent/src/eval/py/kernel.ts
index 3848bd8cc..6e7fbfc80 100644
--- a/packages/coding-agent/src/eval/py/kernel.ts
+++ b/packages/coding-agent/src/eval/py/kernel.ts
@@ -17,7 +17,13 @@ import { Settings } from "../../config/settings";
 import { type KernelDisplayOutput, renderKernelDisplay } from "./display";
 import { PYTHON_PRELUDE } from "./prelude";
 import RUNNER_SCRIPT from "./runner.py" with { type: "text" };
-import { enumeratePythonRuntimes, filterEnv, type PythonRuntime, resolvePythonRuntime } from "./runtime";
+import {
+	enumeratePythonRuntimes,
+	filterEnv,
+	type PythonRuntime,
+	resolveExplicitPythonRuntime,
+	resolvePythonRuntime,
+} from "./runtime";
 import { hostHasInheritableConsole, shouldHideKernelWindow } from "./spawn-options";
 
 export type { KernelDisplayOutput, PythonStatusEvent } from "./display";
@@ -156,7 +162,10 @@ async function probePythonKernelAvailability(cwd: string): Promise<PythonKernelA
 		const settings = await Settings.init();
 		const { env } = settings.getShellConfig();
 		const baseEnv = filterEnv(env);
-		const runtimes = enumeratePythonRuntimes(cwd, baseEnv);
+		const explicitInterpreter = settings.get("python.interpreter")?.trim();
+		const runtimes = explicitInterpreter
+			? [resolveExplicitPythonRuntime(explicitInterpreter, cwd, baseEnv)]
+			: enumeratePythonRuntimes(cwd, baseEnv);
 		if (runtimes.length === 0) {
 			return { ok: false, reason: "Python executable not found on PATH" };
 		}
@@ -250,8 +259,12 @@ export class PythonKernel {
 		// PI_PYTHON_SKIP_CHECK), where no candidate was probed.
 		let runtime = availability.runtime;
 		if (!runtime) {
-			const { env: shellEnv } = (await Settings.init()).getShellConfig();
-			runtime = resolvePythonRuntime(options.cwd, filterEnv(shellEnv));
+			const settings = await Settings.init();
+			const { env: shellEnv } = settings.getShellConfig();
+			const explicitInterpreter = settings.get("python.interpreter")?.trim();
+			runtime = explicitInterpreter
+				? resolveExplicitPythonRuntime(explicitInterpreter, options.cwd, filterEnv(shellEnv))
+				: resolvePythonRuntime(options.cwd, filterEnv(shellEnv));
 		}
 		const spawnEnv: Record<string, string> = {};
 		for (const [key, value] of Object.entries(runtime.env)) {
diff --git a/packages/coding-agent/src/eval/py/runtime.ts b/packages/coding-agent/src/eval/py/runtime.ts
index acc41d075..e5e89d0e0 100644
--- a/packages/coding-agent/src/eval/py/runtime.ts
+++ b/packages/coding-agent/src/eval/py/runtime.ts
@@ -182,6 +182,27 @@ function venvBinDir(venvPath: string): string {
 	return process.platform === "win32" ? path.join(venvPath, "Scripts") : path.join(venvPath, "bin");
 }
 
+function detectExplicitVenv(pythonPath: string): { venvPath: string; binDir: string } | undefined {
+	const binDir = path.dirname(pythonPath);
+	const venvPath = path.dirname(binDir);
+	if (fs.existsSync(path.join(venvPath, "pyvenv.cfg"))) {
+		return { venvPath, binDir };
+	}
+	return undefined;
+}
+
+export function resolveExplicitPythonRuntime(
+	interpreter: string,
+	cwd: string,
+	baseEnv: Record<string, string | undefined>,
+): PythonRuntime {
+	const pythonPath = path.isAbsolute(interpreter) ? interpreter : path.resolve(cwd, interpreter);
+	const venv = detectExplicitVenv(pythonPath);
+	if (venv) {
+		return { pythonPath, env: applyVenvEnv(baseEnv, venv.venvPath, venv.binDir), venvPath: venv.venvPath };
+	}
+	return { pythonPath, env: { ...baseEnv } };
+}
 /**
  * Enumerate candidate Python runtimes in priority order: an active/project venv,
  * the managed `~/.omp/python-env`, then the system interpreter on PATH. Every
diff --git a/packages/coding-agent/test/core/python-kernel-env.test.ts b/packages/coding-agent/test/core/python-kernel-env.test.ts
index 67ef5f162..cc257bb4f 100644
--- a/packages/coding-agent/test/core/python-kernel-env.test.ts
+++ b/packages/coding-agent/test/core/python-kernel-env.test.ts
@@ -1,7 +1,12 @@
 import { afterEach, describe, expect, it, vi } from "bun:test";
 import * as fs from "node:fs";
 import * as path from "node:path";
-import { enumeratePythonRuntimes, filterEnv, resolvePythonRuntime } from "@oh-my-pi/pi-coding-agent/eval/py/runtime";
+import {
+	enumeratePythonRuntimes,
+	filterEnv,
+	resolveExplicitPythonRuntime,
+	resolvePythonRuntime,
+} from "@oh-my-pi/pi-coding-agent/eval/py/runtime";
 import * as piUtils from "@oh-my-pi/pi-utils";
 
 describe("Python gateway environment filtering", () => {
@@ -92,6 +97,35 @@ describe("enumeratePythonRuntimes", () => {
 		expect(resolvePythonRuntime(path.join(path.sep, "work"), {}).pythonPath).toBe(systemPy);
 	});
 
+	it("resolves an explicit interpreter without falling through to discovery", () => {
+		vi.spyOn(piUtils, "getPythonEnvDir").mockReturnValue(managedDir);
+		vi.spyOn(piUtils, "$which").mockImplementation(bin => (bin === "python" ? systemPy : null));
+		vi.spyOn(fs, "existsSync").mockReturnValue(false);
+		const explicitPy = path.join(path.sep, "custom", "python3.13");
+
+		const runtime = resolveExplicitPythonRuntime(explicitPy, path.join(path.sep, "work"), {
+			PATH: path.join(path.sep, "usr", "bin"),
+		});
+
+		expect(runtime.pythonPath).toBe(explicitPy);
+		expect(runtime.venvPath).toBeUndefined();
+		expect(runtime.env.PATH).toBe(path.join(path.sep, "usr", "bin"));
+	});
+
+	it("sets venv env vars for an explicit interpreter inside a virtualenv", () => {
+		const venvDir = path.join(path.sep, "work", ".venv");
+		const binDir = path.join(venvDir, process.platform === "win32" ? "Scripts" : "bin");
+		const explicitPy = path.join(binDir, process.platform === "win32" ? "python.exe" : "python");
+		vi.spyOn(fs, "existsSync").mockImplementation(candidate => candidate === path.join(venvDir, "pyvenv.cfg"));
+
+		const runtime = resolveExplicitPythonRuntime(explicitPy, path.join(path.sep, "work"), {
+			PATH: path.join(path.sep, "usr", "bin"),
+		});
+
+		expect(runtime.venvPath).toBe(venvDir);
+		expect(runtime.env.VIRTUAL_ENV).toBe(venvDir);
+		expect(runtime.env.PATH).toBe(`${binDir}${path.delimiter}${path.join(path.sep, "usr", "bin")}`);
+	});
 	it("throws from resolvePythonRuntime when no interpreter can be found", () => {
 		vi.spyOn(piUtils, "getPythonEnvDir").mockReturnValue(managedDir);
 		vi.spyOn(piUtils, "$which").mockReturnValue(null);