diff --git a/packages/coding-agent/CHANGELOG.md b/packages/coding-agent/CHANGELOG.md
index de6bd9b0f..7a51caad1 100644
--- a/packages/coding-agent/CHANGELOG.md
+++ b/packages/coding-agent/CHANGELOG.md
@@ -11,6 +11,7 @@
 - `pi update` now lists each updated package with its npm version or git commit change, for example `npm:foo 1.2.0 -> 1.3.0`, and prints `Packages are already up to date` when nothing changed. When nothing changed but an update printed a warning, for example because npm left the old version installed after resolving stale registry metadata, it prints `No packages were updated, see the warnings above` instead; in offline mode it prints `Skipped package updates (offline mode)`. `PackageManager.update()` reports each changed package as a new `result` progress event whose `message` holds that line ([#11707](https://github.com/earendil-works/pi/pull/11707), [#11711](https://github.com/earendil-works/pi/pull/11711))
 - Anthropic sessions now use message threads: each request sends only the new messages and the server continues from the previous reply, falling back to the full request when the conversation changed (for example after compaction or a tool list change). On by default for the `anthropic` provider on `api.anthropic.com`; set `compat.supportsMessageThreads` in `models.json` to enable it for gateways that forward the `thread` field, or to turn it off. Cache warming does not touch the session's thread ([#11545](https://github.com/earendil-works/pi/pull/11545))
 - `pi.registerMarkdownTransformer()` takes an optional `{ messageTypes }` that selects the Markdown surfaces a transformer runs on. Besides user, assistant, and thinking Markdown, transformers can now opt into `custom` (custom messages and skill blocks), `summary` (branch and compaction summaries), and `changelog` (What's New, `/changelog`, the Extension Updates notice, and the Update Available note). Without options a transformer runs on user, assistant, and thinking Markdown as before. The built-in Mermaid renderer now also draws diagrams in expanded branch and compaction summaries
+- `pi auth login <provider>` logs in to a provider from the shell without starting a session, for example `pi auth login radius`. It signs in with an account in the browser and exits; `--api-key` saves an API key instead, and `--no-browser` uses device code or copy-code sign-in instead. Logging in to Radius also configures the Radius MCP server. `pi auth logout <provider>` removes the stored credentials, like `/logout`
 
 ### Changed
 
diff --git a/packages/coding-agent/docs/cli.md b/packages/coding-agent/docs/cli.md
index 8861d22ad..216289ac9 100644
--- a/packages/coding-agent/docs/cli.md
+++ b/packages/coding-agent/docs/cli.md
@@ -12,6 +12,8 @@ pi uninstall <source> [options]
 pi update [target] [options]
 pi list
 pi config [options]
+pi auth login <provider> [--api-key] [--no-browser]
+pi auth logout <provider>
 pi auth <check|print-api-key|print-bearer-token> [options]
 pi mcp <add|remove|list|login|logout> [options]
 ```
@@ -302,11 +304,22 @@ export PI_SELF_UPDATE_COMMAND="mise use -g npm:{packageName}@{version}"
 
 ## Credential commands
 
+`pi auth login <provider>` logs in to a provider in the terminal and exits, without starting a session. It signs in with an account and opens the browser, like `/login <provider>`. Providers without account sign-in ask for an API key. Logging in to Radius also adds the Radius MCP server to `~/.pi/agent/mcp.json` when no global server uses that login yet. It requires an interactive terminal.
+
+| Option | Description |
+|---|---|
+| `--api-key` | Save an API key instead of signing in with an account; the key is read without echoing it |
+| `--no-browser` | Do not open a browser; use the provider's other sign-in method, such as a device code, for example over SSH. Asks when there are several. Not allowed with `--api-key` |
+
+`pi auth logout <provider>` removes the credentials that `pi auth login` or `/login` stored, like `/logout`. Environment variables and `models.json` config are unchanged. It exits with status `0` when nothing is stored, so it is safe to repeat.
+
 ```sh
+pi auth login radius
+pi auth logout radius
 pi auth check --provider openai --json
 ```
 
-Authentication commands require `--provider <provider>` or `--model <model>`. See [Providers](providers.md) for supported methods.
+The other authentication commands require `--provider <provider>` or `--model <model>`. See [Providers](providers.md) for supported methods.
 
 | Command | Description |
 |---|---|
diff --git a/packages/coding-agent/src/cli/args.ts b/packages/coding-agent/src/cli/args.ts
index 4bcd28dc2..8de8441c4 100644
--- a/packages/coding-agent/src/cli/args.ts
+++ b/packages/coding-agent/src/cli/args.ts
@@ -293,7 +293,7 @@ ${chalk.bold("Commands:")}
   ${APP_NAME} update [source|self|pi]   Update pi, extensions, or model catalogs
   ${APP_NAME} list                      List installed extensions from settings
   ${APP_NAME} config [-l]               Open TUI to enable/disable package resources (Tab switches scope)
-  ${APP_NAME} auth <command>            Print credentials or check provider readiness
+  ${APP_NAME} auth <command>            Log in or out, print credentials, or check provider readiness
   ${APP_NAME} mcp <command>             Manage MCP servers
   ${APP_NAME} <command> --help          Show help for install/remove/uninstall/update/list/config/auth/mcp
 
diff --git a/packages/coding-agent/src/cli/auth-command.ts b/packages/coding-agent/src/cli/auth-command.ts
index 9ee804602..687e5dbd5 100644
--- a/packages/coding-agent/src/cli/auth-command.ts
+++ b/packages/coding-agent/src/cli/auth-command.ts
@@ -38,11 +38,35 @@ export function isAuthCommandHelp(args: string[]): boolean {
 
 export function printAuthCommandHelp(): void {
 	console.log(`Usage:
+  pi auth login <provider> [--api-key] [--no-browser]
+  pi auth logout <provider>
   pi auth print-api-key [--provider <provider>] [--model <model>]
   pi auth print-bearer-token [--provider <provider>] [--model <model>] [--min-expiry <duration>]
   pi auth check [--provider <provider>] [--model <model>] [--json] [--credentials] [--no-refresh]
 
-Auth commands require at least one of --provider or --model. Checks refresh expired OAuth credentials by default; --no-refresh prevents this. --credentials emits the credential, or includes it in JSON output.`);
+Log in to and out of model providers, print their credentials for external clients, or check that they are ready.
+Credentials are stored in ~/.pi/agent/auth.json.
+
+Commands:
+  login <provider>        Sign in with an account in the browser, or save an API key, then exit
+  logout <provider>       Remove the stored credentials; environment variables and models.json stay
+  print-api-key           Print the resolved API key
+  print-bearer-token      Print a resolved OAuth bearer token (refreshes if expired)
+  check                   Print ready, not_ready, or invalid; exit with 0, 1, or 2
+
+Options for print-api-key, print-bearer-token, and check (at least one is required):
+  --provider <provider>   Resolve credentials for a provider
+  --model <model>         Resolve credentials from a model
+
+Options for login:
+  --api-key               Save an API key instead of signing in with an account
+  --no-browser            Do not open a browser; use another sign-in method, e.g. device code
+
+Other options:
+  --min-expiry <duration> Minimum remaining token lifetime for print-bearer-token, e.g. 30m or 1h
+  --json                  Print the check result as JSON
+  --credentials           Emit the credential from check, or include it in JSON output
+  --no-refresh            Do not refresh expired OAuth credentials during check`);
 }
 
 export function parseAuthCommand(args: string[]): AuthCommand | undefined {
@@ -58,7 +82,7 @@ export function parseAuthCommand(args: string[]): AuthCommand | undefined {
 					: undefined;
 	if (!kind) {
 		throw new AuthCommandError(
-			`Unknown auth command "${args[1] ?? ""}". Use "${APP_NAME} auth print-api-key", "${APP_NAME} auth print-bearer-token", or "${APP_NAME} auth check".`,
+			`Unknown auth command "${args[1] ?? ""}". Use "${APP_NAME} auth login", "${APP_NAME} auth logout", "${APP_NAME} auth print-api-key", "${APP_NAME} auth print-bearer-token", or "${APP_NAME} auth check".`,
 		);
 	}
 
diff --git a/packages/coding-agent/src/cli/auth-login.ts b/packages/coding-agent/src/cli/auth-login.ts
new file mode 100644
index 000000000..d0729be5d
--- /dev/null
+++ b/packages/coding-agent/src/cli/auth-login.ts
@@ -0,0 +1,277 @@
+import type { AuthInteraction, AuthPrompt, AuthType, Provider } from "@earendil-works/pi-ai";
+import { replaceControlCharacters } from "@earendil-works/pi-tui";
+import { APP_NAME, getAuthPath } from "../config.ts";
+import { CredentialSynchronizationError, type ModelRuntime } from "../core/model-runtime.ts";
+import { findMatchingProviders } from "../core/provider-matching.ts";
+import { RADIUS_PROVIDER_ID } from "../core/radius.ts";
+import { planRadiusMcpServer } from "../core/radius-mcp.ts";
+import { addMcpServerConfig } from "../extensions/mcp/config.ts";
+import { displayUrl, webUrl } from "../utils/web-url.ts";
+
+import type { LoginTerminal } from "./auth-terminal.ts";
+
+/** Dependencies of `runAuthLogin`, injected so tests can script the terminal. */
+export interface AuthLoginOptions {
+	modelRuntime: ModelRuntime;
+	terminal: LoginTerminal;
+	agentDir: string;
+	cwd: string;
+	getDeviceId: () => string;
+	/** Aborts the login, e.g. on Ctrl+C. */
+	signal: AbortSignal;
+}
+
+const AUTH_LOGIN_USAGE = `${APP_NAME} auth login <provider> [--api-key] [--no-browser]`;
+
+/** Parsed `pi auth login` arguments. */
+interface LoginRequest {
+	providerRef: string;
+	/** Log in with an API key instead of an account. */
+	apiKey: boolean;
+	/** Open the browser and take the browser sign-in method without asking. */
+	browser: boolean;
+}
+
+/** Run `pi auth login <provider>` in the terminal and return the process exit code. */
+export async function runAuthLogin(args: string[], options: AuthLoginOptions): Promise<number> {
+	const { modelRuntime, terminal, signal } = options;
+	const parsed = parseLoginRequest(args);
+	if (parsed.type === "invalid") {
+		terminal.error(parsed.message);
+		return 1;
+	}
+	const { request } = parsed;
+	const { providerRef } = request;
+
+	const provider = findMatchingProviders(modelRuntime.getProviders(), providerRef)[0];
+	if (!provider) {
+		const loginProviders = modelRuntime
+			.getProviders()
+			.filter((candidate) => candidate.auth.oauth || candidate.auth.apiKey?.login)
+			.map((candidate) => candidate.id)
+			.sort();
+		terminal.error(`Unknown provider "${replaceControlCharacters(providerRef)}".`);
+		terminal.error(`Providers: ${loginProviders.join(", ")}`);
+		return 1;
+	}
+	if (!terminal.interactive) {
+		terminal.error(`"${AUTH_LOGIN_USAGE}" requires an interactive terminal`);
+		return 1;
+	}
+
+	const authType = selectAuthType(provider, request.apiKey);
+	if (authType.type === "unavailable") {
+		terminal.error(authType.message);
+		return 1;
+	}
+	try {
+		await modelRuntime.login(
+			provider.id,
+			authType.type,
+			createLoginInteraction(provider.id, authType.type, request, terminal, signal),
+			{ getDeviceId: options.getDeviceId },
+		);
+	} catch (error: unknown) {
+		const message = error instanceof Error ? error.message : String(error);
+		if (error instanceof CredentialSynchronizationError) {
+			terminal.error(`Logged in to ${provider.name}, but local model state could not be synchronized: ${message}`);
+		} else if (signal.aborted || message === "Login cancelled") {
+			terminal.error("Login cancelled.");
+		} else {
+			terminal.error(`Failed to log in to ${provider.name}: ${message}`);
+		}
+		return 1;
+	}
+
+	terminal.write(
+		`${authType.type === "oauth" ? `Logged in to ${provider.name}` : `Saved API key for ${provider.name}`}. Credentials saved to ${getAuthPath()}`,
+	);
+	await refreshProviderCatalog(provider, modelRuntime, terminal, signal);
+	if (provider.id === RADIUS_PROVIDER_ID) configureRadiusMcpServer(provider, options);
+	return 0;
+}
+
+function parseLoginRequest(
+	args: string[],
+): { type: "valid"; request: LoginRequest } | { type: "invalid"; message: string } {
+	const usage = { type: "invalid", message: `Usage: ${AUTH_LOGIN_USAGE}` } as const;
+	const request: LoginRequest = { providerRef: "", apiKey: false, browser: true };
+	for (const arg of args) {
+		if (arg === "--api-key") request.apiKey = true;
+		else if (arg === "--no-browser") request.browser = false;
+		else if (arg.startsWith("-") || request.providerRef) return usage;
+		else request.providerRef = arg;
+	}
+	if (!request.providerRef) return usage;
+	if (request.apiKey && !request.browser) {
+		return { type: "invalid", message: "--no-browser only applies to account sign-in; omit it with --api-key." };
+	}
+	return { type: "valid", request };
+}
+
+/**
+ * Account login unless `apiKey` asks for an API key. Providers without account login use their API key login, since
+ * that is the only way in.
+ */
+function selectAuthType(
+	provider: Provider,
+	apiKey: boolean,
+): { type: AuthType } | { type: "unavailable"; message: string } {
+	const hasApiKeyLogin = provider.auth.apiKey?.login !== undefined;
+	if (!apiKey && provider.auth.oauth) return { type: "oauth" };
+	if (hasApiKeyLogin) return { type: "api_key" };
+	if (apiKey && provider.auth.oauth) {
+		return { type: "unavailable", message: `${provider.name} has no API key login. Omit --api-key to sign in.` };
+	}
+	const method = provider.auth.apiKey?.name ?? "ambient credentials";
+	return { type: "unavailable", message: `${provider.name} is configured outside ${APP_NAME} (${method}).` };
+}
+
+/** Adapt provider prompts and events to the command's selected sign-in method. */
+function createLoginInteraction(
+	providerId: string,
+	authType: AuthType,
+	request: LoginRequest,
+	terminal: LoginTerminal,
+	signal: AbortSignal,
+): AuthInteraction {
+	// Account logins list the browser sign-in first, as /login; API key setup asks every selection.
+	const methodChoice = authType === "api_key" ? "ask" : request.browser ? "browser" : "other";
+	let skippedMethods: string[] = [];
+
+	async function selectMethod(prompt: Extract<AuthPrompt, { type: "select" }>, promptSignal: AbortSignal) {
+		const [first, ...others] = prompt.options;
+		if (methodChoice === "ask" || !first) {
+			return selectInTerminal(prompt.message, prompt.options, terminal, promptSignal);
+		}
+		if (methodChoice === "browser") {
+			skippedMethods = others.map((option) => option.label);
+			return first.id;
+		}
+		const [onlyOther, ...moreOthers] = others;
+		// A provider whose only method is the browser sign-in still gets it, without opening the browser.
+		if (!onlyOther) return first.id;
+		if (moreOthers.length > 0) return selectInTerminal(prompt.message, others, terminal, promptSignal);
+		terminal.write(`${prompt.message} ${onlyOther.label}`);
+		return onlyOther.id;
+	}
+
+	return {
+		signal,
+		prompt(prompt) {
+			// The browser callback can finish a step before the pasted code, cancelling just that prompt.
+			const promptSignal = prompt.signal ? AbortSignal.any([signal, prompt.signal]) : signal;
+			if (prompt.type === "select") return selectMethod(prompt, promptSignal);
+			const placeholder = prompt.placeholder ? ` (${prompt.placeholder})` : "";
+			const message = `${prompt.message}${placeholder}: `;
+			return prompt.type === "secret"
+				? terminal.secret(message, promptSignal)
+				: terminal.question(message, promptSignal);
+		},
+		notify(event) {
+			if (event.type === "auth_url") {
+				terminal.write(`Open this URL to sign in:\n  ${displayUrl(event.url)}`);
+				if (event.instructions) terminal.write(event.instructions);
+				const target = webUrl(event.url);
+				if (target !== undefined && request.browser) terminal.openUrl(target);
+				// Providers without a method choice have nothing else to offer, so they get no hint.
+				const rerun = `"${APP_NAME} auth login ${providerId} --no-browser"`;
+				const [onlyMethod, ...moreMethods] = skippedMethods;
+				if (onlyMethod !== undefined && moreMethods.length === 0) {
+					terminal.write(`To use "${onlyMethod}" instead, run ${rerun}`);
+				} else if (onlyMethod !== undefined) {
+					const labels = skippedMethods.map((label) => `"${label}"`).join(", ");
+					terminal.write(`Other sign-in methods: ${labels}. Run ${rerun} to choose one.`);
+				}
+			} else if (event.type === "device_code") {
+				terminal.write(`Open ${displayUrl(event.verificationUri)} and enter code: ${event.userCode}`);
+				const target = webUrl(event.verificationUri);
+				if (target !== undefined && request.browser && event.openBrowserOnConfirm !== false) {
+					terminal.openUrl(target);
+				}
+				terminal.write("Waiting for authentication...");
+			} else if (event.type === "info") {
+				terminal.write(event.message);
+				for (const link of event.links ?? []) {
+					terminal.write(`  ${link.label ? `${link.label}: ` : ""}${displayUrl(link.url)}`);
+				}
+			} else {
+				terminal.write(event.message);
+			}
+		},
+	};
+}
+
+async function selectInTerminal(
+	message: string,
+	options: readonly { id: string; label: string; description?: string }[],
+	terminal: LoginTerminal,
+	signal: AbortSignal,
+): Promise<string> {
+	terminal.write(message);
+	options.forEach((option, index) => {
+		terminal.write(`  ${index + 1}. ${option.label}${option.description ? ` - ${option.description}` : ""}`);
+	});
+	while (true) {
+		const answer = (await terminal.question(`Select 1-${options.length}: `, signal)).trim();
+		const option = /^\d+$/u.test(answer) ? options[Number(answer) - 1] : undefined;
+		if (option) return option.id;
+		terminal.write(`Enter a number from 1 to ${options.length}.`);
+	}
+}
+
+/** Fetch the provider's model catalog now, since dynamic catalogs stay empty until the first authenticated refresh. */
+async function refreshProviderCatalog(
+	provider: Provider,
+	modelRuntime: ModelRuntime,
+	terminal: LoginTerminal,
+	signal: AbortSignal,
+) {
+	// The login is saved by now, so Ctrl+C only skips the refresh.
+	const cancelled = () => {
+		terminal.write(`Skipped the ${provider.name} model catalog refresh; ${APP_NAME} refreshes it on next start.`);
+	};
+	try {
+		const result = await modelRuntime.refresh({
+			providers: [provider.id],
+			signal: AbortSignal.any([signal, AbortSignal.timeout(15_000)]),
+		});
+		if (signal.aborted) {
+			cancelled();
+		} else if (result.aborted) {
+			terminal.write(
+				`The ${provider.name} model catalog refresh timed out; ${APP_NAME} refreshes it on next start.`,
+			);
+		} else if (result.errors.size > 0) {
+			terminal.write(
+				`The ${provider.name} model catalog could not be refreshed; ${APP_NAME} retries on next start.`,
+			);
+		}
+	} catch (error: unknown) {
+		if (signal.aborted) {
+			cancelled();
+			return;
+		}
+		terminal.write(
+			`The ${provider.name} model catalog could not be refreshed: ${error instanceof Error ? error.message : String(error)}`,
+		);
+	}
+}
+
+/**
+ * Point the Radius MCP server in the global mcp.json at the Radius login without asking, since the login is what the
+ * server needs; /login asks instead. Nothing changes when a global server already uses this login.
+ */
+function configureRadiusMcpServer(provider: Provider, options: AuthLoginOptions): void {
+	const { terminal } = options;
+	const plan = planRadiusMcpServer(provider.id, options.agentDir, options.cwd);
+	if (!plan) return;
+	try {
+		const replaced = addMcpServerConfig(plan.mcpPath, plan.name, plan.config);
+		terminal.write(
+			`${replaced ? "Updated" : "Added"} MCP server "${plan.name}" in ${plan.mcpPath} to use the ${provider.name} login.`,
+		);
+	} catch (error: unknown) {
+		terminal.error(`Could not update ${plan.mcpPath}: ${error instanceof Error ? error.message : String(error)}`);
+	}
+}
diff --git a/packages/coding-agent/src/cli/auth-logout.ts b/packages/coding-agent/src/cli/auth-logout.ts
new file mode 100644
index 000000000..59a201440
--- /dev/null
+++ b/packages/coding-agent/src/cli/auth-logout.ts
@@ -0,0 +1,72 @@
+import type { CredentialInfo } from "@earendil-works/pi-ai";
+import { replaceControlCharacters } from "@earendil-works/pi-tui";
+import { APP_NAME } from "../config.ts";
+import { CredentialSynchronizationError, type ModelRuntime } from "../core/model-runtime.ts";
+import { findMatchingProviders } from "../core/provider-matching.ts";
+import type { AuthOutput } from "./auth-terminal.ts";
+
+/** Dependencies of `runAuthLogout`, injected so tests can capture the output. */
+export interface AuthLogoutOptions {
+	modelRuntime: ModelRuntime;
+	terminal: AuthOutput;
+	signal: AbortSignal;
+}
+
+const AUTH_LOGOUT_USAGE = `${APP_NAME} auth logout <provider>`;
+
+/**
+ * Run `pi auth logout <provider>`: remove the credential `pi auth login` or /login stored, and return the exit code.
+ * Environment variables and models.json config stay, as with /logout.
+ */
+export async function runAuthLogout(args: string[], options: AuthLogoutOptions): Promise<number> {
+	const { modelRuntime, terminal, signal } = options;
+	const [providerRef, ...rest] = args;
+	if (providerRef === undefined || providerRef.startsWith("-") || rest.length > 0) {
+		terminal.error(`Usage: ${AUTH_LOGOUT_USAGE}`);
+		return 1;
+	}
+
+	let stored: readonly CredentialInfo[];
+	try {
+		stored = await modelRuntime.listCredentials({ signal });
+	} catch (error: unknown) {
+		terminal.error(`Could not read stored credentials: ${error instanceof Error ? error.message : String(error)}`);
+		return 1;
+	}
+	const provider = findMatchingProviders(modelRuntime.getProviders(), providerRef)[0];
+	// Providers registered by extensions are not loaded here, so their stored credentials match by id alone.
+	const credential = stored.find((candidate) => candidate.providerId === (provider?.id ?? providerRef));
+	if (!provider && !credential) {
+		terminal.error(`Unknown provider "${replaceControlCharacters(providerRef)}".`);
+		const storedIds = stored.map((credential) => credential.providerId).sort();
+		terminal.error(`Stored credentials: ${storedIds.join(", ") || "none"}`);
+		return 1;
+	}
+	const providerName = provider?.name ?? providerRef;
+	if (!credential) {
+		terminal.write(
+			`No stored credentials for ${providerName}. Environment variables and models.json config are unchanged.`,
+		);
+		return 0;
+	}
+
+	try {
+		await modelRuntime.logout(credential.providerId, { signal });
+	} catch (error: unknown) {
+		const message = error instanceof Error ? error.message : String(error);
+		if (error instanceof CredentialSynchronizationError) {
+			terminal.error(
+				`Credentials removed for ${providerName}, but local model state could not be synchronized: ${message}`,
+			);
+		} else {
+			terminal.error(`Logout failed: ${message}`);
+		}
+		return 1;
+	}
+	terminal.write(
+		credential.type === "oauth"
+			? `Logged out of ${providerName}.`
+			: `Removed stored API key for ${providerName}. Environment variables and models.json config are unchanged.`,
+	);
+	return 0;
+}
diff --git a/packages/coding-agent/src/cli/auth-terminal.ts b/packages/coding-agent/src/cli/auth-terminal.ts
new file mode 100644
index 000000000..a11a09e40
--- /dev/null
+++ b/packages/coding-agent/src/cli/auth-terminal.ts
@@ -0,0 +1,78 @@
+import { openBrowser } from "../utils/open-browser.ts";
+import { questionTerminal } from "../utils/terminal-question.ts";
+
+/** Output shared by the terminal authentication commands. */
+export interface AuthOutput {
+	write(line: string): void;
+	error(line: string): void;
+}
+
+/** Line-based terminal I/O for `pi auth login`. Prompts reject when `signal` aborts. */
+export interface LoginTerminal extends AuthOutput {
+	/** Whether stdin and stdout are a terminal; login prompts need one. */
+	interactive: boolean;
+	question(message: string, signal: AbortSignal): Promise<string>;
+	/** Read a line without echoing it. */
+	secret(message: string, signal: AbortSignal): Promise<string>;
+	openUrl(url: string): void;
+}
+
+/** Terminal I/O on stdin and stdout. `onInterrupt` runs on Ctrl+C or EOF in a question, or Ctrl+C in a secret. */
+export function createProcessLoginTerminal(onInterrupt: () => void): LoginTerminal {
+	return {
+		interactive: process.stdin.isTTY === true && process.stdout.isTTY === true,
+		write: (line) => process.stdout.write(`${line}\n`),
+		error: (line) => process.stderr.write(`${line}\n`),
+		question: (message, signal) => questionTerminal(message, { signal, output: process.stdout, onInterrupt }),
+		secret: (message, signal) => readSecret(message, signal, onInterrupt),
+		openUrl: openBrowser,
+	};
+}
+
+function readSecret(message: string, signal: AbortSignal, onInterrupt: () => void): Promise<string> {
+	const stdin = process.stdin;
+	return new Promise((resolve, reject) => {
+		if (signal.aborted) {
+			reject(new Error("Login cancelled"));
+			return;
+		}
+		let value = "";
+		const finish = () => {
+			stdin.off("data", onData);
+			signal.removeEventListener("abort", onAbort);
+			stdin.setRawMode(false);
+			stdin.pause();
+			process.stdout.write("\n");
+		};
+		const onAbort = () => {
+			finish();
+			reject(new Error("Login cancelled"));
+		};
+		const onData = (data: Buffer) => {
+			const chunk = data.toString("utf8");
+			// Ignore escape sequences such as arrow keys.
+			if (chunk.startsWith("\u001b")) return;
+			for (const char of chunk) {
+				if (char === "\r" || char === "\n") {
+					finish();
+					resolve(value);
+					return;
+				}
+				if (char === "\u0003") {
+					onInterrupt();
+					return;
+				}
+				if (char === "\u007f" || char === "\b") {
+					value = Array.from(value).slice(0, -1).join("");
+				} else if (char >= " ") {
+					value += char;
+				}
+			}
+		};
+		process.stdout.write(message);
+		stdin.setRawMode(true);
+		stdin.resume();
+		stdin.on("data", onData);
+		signal.addEventListener("abort", onAbort, { once: true });
+	});
+}
diff --git a/packages/coding-agent/src/core/provider-matching.ts b/packages/coding-agent/src/core/provider-matching.ts
new file mode 100644
index 000000000..26b94d563
--- /dev/null
+++ b/packages/coding-agent/src/core/provider-matching.ts
@@ -0,0 +1,11 @@
+/** Match provider IDs and display names exactly, ignoring case and surrounding whitespace in the reference. */
+export function findMatchingProviders<T extends { id: string; name: string }>(
+	providers: readonly T[],
+	providerRef: string,
+): T[] {
+	const normalized = providerRef.trim().toLowerCase();
+	if (!normalized) return [];
+	return providers.filter(
+		(provider) => provider.id.toLowerCase() === normalized || provider.name.toLowerCase() === normalized,
+	);
+}
diff --git a/packages/coding-agent/src/core/radius-mcp.ts b/packages/coding-agent/src/core/radius-mcp.ts
new file mode 100644
index 000000000..13a9751e6
--- /dev/null
+++ b/packages/coding-agent/src/core/radius-mcp.ts
@@ -0,0 +1,44 @@
+import path from "node:path";
+import { mcpNamespace } from "@earendil-works/pi-mcp";
+import { loadMcpConfig } from "../extensions/mcp/config.ts";
+import type { McpHttpServerConfig } from "./mcp-servers.ts";
+import { RADIUS_MCP_URL } from "./radius.ts";
+
+/** Change to the global mcp.json that points the Radius MCP server at a Radius login. */
+export interface RadiusMcpServerPlan {
+	mcpPath: string;
+	name: string;
+	config: McpHttpServerConfig;
+}
+
+/**
+ * The global mcp.json entry that makes the Radius MCP server use the login of `providerId`, adding the server when
+ * missing, or undefined when a global server already uses that login.
+ */
+export function planRadiusMcpServer(
+	providerId: string,
+	agentDir: string,
+	cwd: string,
+): RadiusMcpServerPlan | undefined {
+	const normalizeUrl = (url: string) => url.replace(/\/+$/u, "");
+	const { servers } = loadMcpConfig({ agentDir, cwd, projectTrusted: false });
+	const existing = servers.find(
+		(server) => "url" in server.config && normalizeUrl(server.config.url) === normalizeUrl(RADIUS_MCP_URL),
+	);
+	if (existing && "url" in existing.config && existing.config.auth?.provider === providerId) return undefined;
+
+	let name = existing?.name ?? "radius";
+	if (!existing) {
+		const namespaces = new Set(servers.map((server) => mcpNamespace(server.name)));
+		for (let suffix = 1; namespaces.has(mcpNamespace(name)); suffix++) {
+			name = suffix === 1 ? "radius-mcp" : `radius-mcp-${suffix}`;
+		}
+	}
+	const config: McpHttpServerConfig =
+		existing && "url" in existing.config
+			? { ...existing.config, auth: { provider: providerId } }
+			: { url: RADIUS_MCP_URL, auth: { provider: providerId } };
+	// `auth` replaces the MCP OAuth sign-in.
+	delete config.oauth;
+	return { mcpPath: path.join(agentDir, "mcp.json"), name, config };
+}
diff --git a/packages/coding-agent/src/extensions/mcp/cli.ts b/packages/coding-agent/src/extensions/mcp/cli.ts
index 9dba82a84..c55bc8002 100644
--- a/packages/coding-agent/src/extensions/mcp/cli.ts
+++ b/packages/coding-agent/src/extensions/mcp/cli.ts
@@ -7,13 +7,13 @@
 
 import { existsSync } from "node:fs";
 import { join } from "node:path";
-import { createInterface } from "node:readline/promises";
 import chalk from "chalk";
 import { APP_NAME, CONFIG_DIR_NAME } from "../../config.ts";
 import { validateMcpServerConfig } from "../../core/mcp-servers.ts";
 import { ModelRuntime } from "../../core/model-runtime.ts";
 import { ProjectTrustStore } from "../../core/trust-manager.ts";
 import { openBrowser } from "../../utils/open-browser.ts";
+import { questionTerminal } from "../../utils/terminal-question.ts";
 import {
 	addMcpServerConfig,
 	getMcpToolExposure,
@@ -285,7 +285,7 @@ export async function runMcpCommand(args: string[], options: McpCommandOptions):
 			const authProvider = getAuthProvider(entry);
 			if (authProvider) {
 				error(
-					`MCP server "${name}" uses the credentials of provider "${authProvider}". Run /${command} ${authProvider} in ${APP_NAME}.`,
+					`MCP server "${name}" uses the credentials of provider "${authProvider}". Run "${APP_NAME} auth ${command} ${authProvider}".`,
 				);
 				return 1;
 			}
@@ -659,21 +659,19 @@ async function login(
 
 /**
  * The pasted redirect URL in a terminal; otherwise only the browser callback can finish the sign-in.
- * Resolves to undefined when `signal` aborts: the callback arrived, or the sign-in timed out.
+ * Resolves to undefined on cancellation or EOF, or when the callback arrives or the sign-in times out.
  */
 async function waitForRedirectUrl(signal: AbortSignal, interactive: boolean): Promise<string | undefined> {
 	if (!interactive) {
 		if (!signal.aborted) await new Promise((resolve) => signal.addEventListener("abort", resolve, { once: true }));
 		return undefined;
 	}
-	const readline = createInterface({ input: process.stdin, output: process.stderr });
 	try {
-		return await readline.question("If the browser cannot reach this machine, paste the URL it was redirected to: ", {
+		return await questionTerminal("If the browser cannot reach this machine, paste the URL it was redirected to: ", {
 			signal,
+			output: process.stderr,
 		});
 	} catch {
 		return undefined;
-	} finally {
-		readline.close();
 	}
 }
diff --git a/packages/coding-agent/src/main.ts b/packages/coding-agent/src/main.ts
index 34111cca6..080ac0f0f 100644
--- a/packages/coding-agent/src/main.ts
+++ b/packages/coding-agent/src/main.ts
@@ -26,6 +26,9 @@ import {
 	printAuthCommandHelp,
 	validateAuthCommandArgs,
 } from "./cli/auth-command.ts";
+import { runAuthLogin } from "./cli/auth-login.ts";
+import { runAuthLogout } from "./cli/auth-logout.ts";
+import { createProcessLoginTerminal } from "./cli/auth-terminal.ts";
 import { resolveCredentialForPrint } from "./cli/credential-print.ts";
 import { processFileArguments } from "./cli/file-processor.ts";
 import { buildInitialMessage } from "./cli/initial-message.ts";
@@ -130,11 +133,55 @@ function isPlainRuntimeMetadataCommand(parsed: Args): boolean {
 	return !parsed.print && parsed.mode === undefined && (parsed.help === true || parsed.listModels !== undefined);
 }
 
+async function runAuthLoginCommand(args: string[]): Promise<number> {
+	const cwd = process.cwd();
+	const agentDir = getAgentDir();
+	const settingsManager = SettingsManager.create(cwd, agentDir, { projectTrusted: false });
+	applyHttpProxySettings(settingsManager.getGlobalSettings().httpProxy);
+	configureHttpDispatcher(settingsManager.getHttpIdleTimeoutMs());
+	const modelRuntime = await ModelRuntime.create({ allowModelNetwork: false, signal: AbortSignal.timeout(15_000) });
+
+	const controller = new AbortController();
+	const interrupt = () => controller.abort();
+	process.on("SIGINT", interrupt);
+	try {
+		return await runAuthLogin(args, {
+			modelRuntime,
+			terminal: createProcessLoginTerminal(interrupt),
+			agentDir,
+			cwd,
+			getDeviceId: () => settingsManager.getOrCreateDeviceId(),
+			signal: controller.signal,
+		});
+	} finally {
+		process.off("SIGINT", interrupt);
+	}
+}
+
+async function runAuthLogoutCommand(args: string[]): Promise<number> {
+	const signal = AbortSignal.timeout(15_000);
+	const modelRuntime = await ModelRuntime.create({ allowModelNetwork: false, signal });
+	return runAuthLogout(args, {
+		modelRuntime,
+		terminal: { write: (line) => console.log(line), error: (line) => console.error(line) },
+		signal,
+	});
+}
+
 async function runAuthCommand(args: string[]): Promise<boolean> {
 	if (isAuthCommandHelp(args)) {
 		printAuthCommandHelp();
 		return true;
 	}
+	if (args[0] === "auth" && args[1] === "login") {
+		// main() already applied --offline.
+		process.exitCode = await runAuthLoginCommand(args.slice(2).filter((arg) => arg !== "--offline"));
+		return true;
+	}
+	if (args[0] === "auth" && args[1] === "logout") {
+		process.exitCode = await runAuthLogoutCommand(args.slice(2).filter((arg) => arg !== "--offline"));
+		return true;
+	}
 
 	let command: AuthCommand | undefined;
 	try {
diff --git a/packages/coding-agent/src/modes/interactive/components/login-dialog.ts b/packages/coding-agent/src/modes/interactive/components/login-dialog.ts
index 95e676803..0172c0042 100644
--- a/packages/coding-agent/src/modes/interactive/components/login-dialog.ts
+++ b/packages/coding-agent/src/modes/interactive/components/login-dialog.ts
@@ -13,30 +13,12 @@ import {
 } from "@earendil-works/pi-tui";
 import { copyToClipboard } from "../../../utils/clipboard.ts";
 import { openBrowser } from "../../../utils/open-browser.ts";
+import { displayUrl, webUrl } from "../../../utils/web-url.ts";
 import { theme } from "../theme/theme.ts";
 import { AuthUrlComponent } from "./auth-url.ts";
 import { DynamicBorder } from "./dynamic-border.ts";
 import { keyHint } from "./keybinding-hints.ts";
 
-/**
- * The `http:` or `https:` URL `value` names, normalized, or undefined. The shared launcher also opens files and custom
- * protocols, so login only opens web URLs. Normalizing percent-encodes control characters, which would otherwise end a
- * terminal hyperlink early.
- */
-function webUrl(value: string): string | undefined {
-	if (!URL.canParse(value)) return undefined;
-	const url = new URL(value);
-	return url.protocol === "https:" || url.protocol === "http:" ? url.href : undefined;
-}
-
-/**
- * `value` normalized as a web URL, else with control characters replaced: an untrusted string printed as is could end a
- * hyperlink early or send its own escape sequences to the terminal.
- */
-function displayUrl(value: string): string {
-	return webUrl(value) ?? replaceControlCharacters(value);
-}
-
 /** `text` as a terminal hyperlink to `url` when that is a web URL, else plain `text`. */
 function webLink(text: string, url: string): string {
 	const target = webUrl(url);
diff --git a/packages/coding-agent/src/modes/interactive/interactive-mode.ts b/packages/coding-agent/src/modes/interactive/interactive-mode.ts
index 999e1640d..c65c40c2a 100644
--- a/packages/coding-agent/src/modes/interactive/interactive-mode.ts
+++ b/packages/coding-agent/src/modes/interactive/interactive-mode.ts
@@ -96,7 +96,6 @@ import type {
 import { FooterDataProvider, type ReadonlyFooterDataProvider } from "../../core/footer-data-provider.ts";
 import { configureHttpDispatcher, formatHttpIdleTimeoutMs } from "../../core/http-dispatcher.ts";
 import { type AppKeybinding, KeybindingsManager } from "../../core/keybindings.ts";
-import type { McpHttpServerConfig } from "../../core/mcp-servers.ts";
 import { createCompactionSummaryMessage, createCustomMessage } from "../../core/messages.ts";
 import {
 	defaultModelPerProvider,
@@ -105,7 +104,9 @@ import {
 } from "../../core/model-resolver.ts";
 import { CredentialSynchronizationError } from "../../core/model-runtime.ts";
 import { DefaultPackageManager } from "../../core/package-manager.ts";
-import { RADIUS_MCP_URL, RADIUS_PROVIDER_ID } from "../../core/radius.ts";
+import { findMatchingProviders } from "../../core/provider-matching.ts";
+import { RADIUS_PROVIDER_ID } from "../../core/radius.ts";
+import { planRadiusMcpServer } from "../../core/radius-mcp.ts";
 import type { ResourceDiagnostic } from "../../core/resource-loader.ts";
 import { formatMissingSessionCwdPrompt, MissingSessionCwdError } from "../../core/session-cwd.ts";
 import {
@@ -122,7 +123,7 @@ import { withBuiltInRenderers } from "../../core/tools/renderers/index.ts";
 import type { TruncationResult } from "../../core/tools/truncate.ts";
 import { hasTrustRequiringProjectResources, ProjectTrustStore } from "../../core/trust-manager.ts";
 import { getUsageCostBreakdown } from "../../core/usage-totals.ts";
-import { addMcpServerConfig, loadMcpConfig } from "../../extensions/mcp/config.ts";
+import { addMcpServerConfig } from "../../extensions/mcp/config.ts";
 import { getChangelogPath, getNewEntries, normalizeChangelogLinks, parseChangelog } from "../../utils/changelog.ts";
 import { copyToClipboard, readClipboardFilePaths, readClipboardText } from "../../utils/clipboard.ts";
 import { extensionForImageMimeType, readClipboardImage } from "../../utils/clipboard-image.ts";
@@ -5980,26 +5981,13 @@ export class InteractiveMode {
 			.sort((a, b) => a.name.localeCompare(b.name));
 	}
 
-	private findLoginProviderOptions(providerRef: string): AuthSelectorProvider[] {
-		const normalizedProviderRef = providerRef.trim().toLowerCase();
-		if (!normalizedProviderRef) {
-			return [];
-		}
-
-		return this.getLoginProviderOptions().filter(
-			(provider) =>
-				provider.id.toLowerCase() === normalizedProviderRef ||
-				provider.name.toLowerCase() === normalizedProviderRef,
-		);
-	}
-
 	private async handleLoginCommand(providerRef?: string): Promise<void> {
 		if (!providerRef) {
 			this.showLoginAuthTypeSelector();
 			return;
 		}
 
-		const providerOptions = this.findLoginProviderOptions(providerRef);
+		const providerOptions = findMatchingProviders(this.getLoginProviderOptions(), providerRef);
 		if (providerOptions.length === 1) {
 			await this.startProviderLogin(providerOptions[0]!);
 			return;
@@ -6520,26 +6508,9 @@ export class InteractiveMode {
 	 * when missing. Nothing is asked when a global server already uses this login.
 	 */
 	private offerRadiusMcpServer(providerId: string, providerName: string): void {
-		const mcpPath = path.join(getAgentDir(), "mcp.json");
-		const normalizeUrl = (url: string) => url.replace(/\/+$/u, "");
-		const { servers } = loadMcpConfig({
-			agentDir: getAgentDir(),
-			cwd: this.sessionManager.getCwd(),
-			projectTrusted: false,
-		});
-		const existing = servers.find(
-			(server) => "url" in server.config && normalizeUrl(server.config.url) === normalizeUrl(RADIUS_MCP_URL),
-		);
-		if (existing && "url" in existing.config && existing.config.auth?.provider === providerId) return;
-
-		let name = existing?.name ?? "radius";
-		if (!existing && servers.some((server) => server.name === name)) name = "radius-mcp";
-		const config: McpHttpServerConfig =
-			existing && "url" in existing.config
-				? { ...existing.config, auth: { provider: providerId } }
-				: { url: RADIUS_MCP_URL, auth: { provider: providerId } };
-		// `auth` replaces the MCP OAuth sign-in.
-		delete config.oauth;
+		const plan = planRadiusMcpServer(providerId, getAgentDir(), this.sessionManager.getCwd());
+		if (!plan) return;
+		const { mcpPath, name, config } = plan;
 
 		this.showSelector((done) => {
 			const selector = new ExtensionSelectorComponent(
diff --git a/packages/coding-agent/src/utils/terminal-question.ts b/packages/coding-agent/src/utils/terminal-question.ts
new file mode 100644
index 000000000..138c06d9b
--- /dev/null
+++ b/packages/coding-agent/src/utils/terminal-question.ts
@@ -0,0 +1,29 @@
+import { createInterface } from "node:readline/promises";
+
+/** Read one line from stdin, rejecting on abort, Ctrl+C, or EOF and always closing readline. */
+export async function questionTerminal(
+	message: string,
+	options: {
+		output: NodeJS.WritableStream;
+		signal: AbortSignal;
+		/** Called on Ctrl+C or EOF, not when the caller aborts just this prompt. */
+		onInterrupt?: () => void;
+	},
+): Promise<string> {
+	const readline = createInterface({ input: process.stdin, output: options.output });
+	const interrupted = new AbortController();
+	// EOF closes readline without settling its pending question; Ctrl+C normally only pauses it.
+	const onInterrupt = () => interrupted.abort();
+	readline.on("SIGINT", onInterrupt);
+	readline.on("close", onInterrupt);
+	try {
+		return await readline.question(message, { signal: AbortSignal.any([options.signal, interrupted.signal]) });
+	} catch (error) {
+		if (interrupted.signal.aborted) options.onInterrupt?.();
+		throw error;
+	} finally {
+		readline.off("close", onInterrupt);
+		readline.off("SIGINT", onInterrupt);
+		readline.close();
+	}
+}
diff --git a/packages/coding-agent/src/utils/web-url.ts b/packages/coding-agent/src/utils/web-url.ts
new file mode 100644
index 000000000..f4e75e607
--- /dev/null
+++ b/packages/coding-agent/src/utils/web-url.ts
@@ -0,0 +1,20 @@
+import { replaceControlCharacters } from "@earendil-works/pi-tui";
+
+/**
+ * The `http:` or `https:` URL `value` names, normalized, or undefined. The shared launcher also opens files and custom
+ * protocols, so login only opens web URLs. Normalizing percent-encodes control characters, which would otherwise end a
+ * terminal hyperlink early.
+ */
+export function webUrl(value: string): string | undefined {
+	if (!URL.canParse(value)) return undefined;
+	const url = new URL(value);
+	return url.protocol === "https:" || url.protocol === "http:" ? url.href : undefined;
+}
+
+/**
+ * `value` normalized as a web URL, else with control characters replaced: an untrusted string printed as is could end a
+ * hyperlink early or send its own escape sequences to the terminal.
+ */
+export function displayUrl(value: string): string {
+	return webUrl(value) ?? replaceControlCharacters(value);
+}
diff --git a/packages/coding-agent/test/auth-login.test.ts b/packages/coding-agent/test/auth-login.test.ts
new file mode 100644
index 000000000..77d73f324
--- /dev/null
+++ b/packages/coding-agent/test/auth-login.test.ts
@@ -0,0 +1,481 @@
+import { mkdtempSync, readFileSync, rmSync, writeFileSync } from "node:fs";
+import { tmpdir } from "node:os";
+import { join } from "node:path";
+import { InMemoryModelsStore, type Model, type Provider } from "@earendil-works/pi-ai";
+import { describe, expect, test, vi } from "vitest";
+import { runAuthLogin } from "../src/cli/auth-login.ts";
+import type { LoginTerminal } from "../src/cli/auth-terminal.ts";
+import { AuthStorage } from "../src/core/auth-storage.ts";
+import { CredentialSynchronizationError, ModelRuntime } from "../src/core/model-runtime.ts";
+
+const PROVIDER_ID = "login-test";
+
+interface ScriptedTerminal extends LoginTerminal {
+	lines: string[];
+	errors: string[];
+	questions: string[];
+	opened: string[];
+}
+
+/** Answers prompts in order; `secret` and `question` share one answer queue. */
+function scriptedTerminal(answers: string[], interactive = true): ScriptedTerminal {
+	const lines: string[] = [];
+	const errors: string[] = [];
+	const questions: string[] = [];
+	const opened: string[] = [];
+	const answer = async (message: string, signal: AbortSignal) => {
+		questions.push(message);
+		if (signal.aborted) throw new Error("Login cancelled");
+		const next = answers.shift();
+		if (next === undefined) throw new Error(`Unexpected prompt: ${message}`);
+		return next;
+	};
+	return {
+		interactive,
+		lines,
+		errors,
+		questions,
+		opened,
+		write: (line) => lines.push(line),
+		error: (line) => errors.push(line),
+		question: answer,
+		secret: answer,
+		openUrl: (url) => opened.push(url),
+	};
+}
+
+function testModel(providerId: string): Model<"openai-completions"> {
+	return {
+		id: "test-model",
+		name: "test-model",
+		api: "openai-completions",
+		provider: providerId,
+		baseUrl: "https://example.test/v1",
+		reasoning: false,
+		input: ["text"],
+		cost: { input: 0, output: 0, cacheRead: 0, cacheWrite: 0 },
+		contextWindow: 1000,
+		maxTokens: 100,
+	};
+}
+
+function testProvider(auth: Provider["auth"], providerId: string): Provider {
+	const unused = () => {
+		throw new Error("unused");
+	};
+	return {
+		id: providerId,
+		name: "Login Test",
+		auth,
+		getModels: () => [testModel(providerId)],
+		stream: unused,
+		streamSimple: unused,
+	};
+}
+
+const bothMethods: Provider["auth"] = {
+	oauth: {
+		name: "Login Test account",
+		login: async (interaction) => {
+			const method = await interaction.prompt({
+				type: "select",
+				message: "Sign in to Login Test:",
+				options: [
+					{ id: "browser", label: "Sign in with browser" },
+					{ id: "device", label: "Sign in with device code" },
+				],
+			});
+			if (method === "device") {
+				interaction.notify({
+					type: "device_code",
+					userCode: "ABCD-1234",
+					verificationUri: "https://example.test/device",
+				});
+				return { type: "oauth", access: "access-device", refresh: "refresh", expires: Date.now() + 3_600_000 };
+			}
+			interaction.notify({
+				type: "auth_url",
+				url: "https://example.test/authorize",
+				instructions: "Finish in the browser",
+			});
+			const code = await interaction.prompt({ type: "manual_code", message: "Paste the code" });
+			return { type: "oauth", access: `access-${code}`, refresh: "refresh", expires: Date.now() + 3_600_000 };
+		},
+		refresh: async (credential) => credential,
+		toAuth: async (credential) => ({ apiKey: credential.access }),
+	},
+	apiKey: {
+		name: "Login Test API key",
+		login: async (interaction) => ({
+			type: "api_key",
+			key: await interaction.prompt({ type: "secret", message: "Enter Login Test API key" }),
+		}),
+		resolve: async () => undefined,
+	},
+};
+
+async function setup(auth: Provider["auth"], providerId = PROVIDER_ID) {
+	const credentials = AuthStorage.inMemory();
+	const modelRuntime = await ModelRuntime.create({
+		credentials,
+		modelsPath: null,
+		modelsStore: new InMemoryModelsStore(),
+		allowModelNetwork: false,
+	});
+	modelRuntime.registerNativeProvider(testProvider(auth, providerId));
+	return { credentials, modelRuntime };
+}
+
+function run(
+	args: string[],
+	modelRuntime: ModelRuntime,
+	terminal: LoginTerminal,
+	signal = new AbortController().signal,
+	agentDir = "/nonexistent-agent-dir",
+) {
+	return runAuthLogin(args, {
+		modelRuntime,
+		terminal,
+		agentDir,
+		cwd: "/nonexistent-cwd",
+		getDeviceId: () => "device",
+		signal,
+	});
+}
+
+describe("pi auth login", () => {
+	const usage = "Usage: pi auth login <provider> [--api-key] [--no-browser]";
+
+	test("requires exactly one provider and known options", async () => {
+		const { modelRuntime } = await setup(bothMethods);
+		for (const args of [[], ["--api-key"], ["--provider", PROVIDER_ID], [PROVIDER_ID, "extra"]]) {
+			const terminal = scriptedTerminal([]);
+			expect(await run(args, modelRuntime, terminal)).toBe(1);
+			expect(terminal.errors).toEqual([usage]);
+		}
+	});
+
+	test("rejects --no-browser with --api-key", async () => {
+		const { modelRuntime } = await setup(bothMethods);
+		const terminal = scriptedTerminal([]);
+		expect(await run([PROVIDER_ID, "--api-key", "--no-browser"], modelRuntime, terminal)).toBe(1);
+		expect(terminal.errors).toEqual(["--no-browser only applies to account sign-in; omit it with --api-key."]);
+	});
+
+	test("rejects an unknown provider and lists the providers with a login flow", async () => {
+		const { modelRuntime } = await setup(bothMethods);
+		const terminal = scriptedTerminal([]);
+		expect(await run(["nope"], modelRuntime, terminal)).toBe(1);
+		expect(terminal.errors[0]).toBe('Unknown provider "nope".');
+		expect(terminal.errors[1]).toContain(PROVIDER_ID);
+	});
+
+	test("requires an interactive terminal after checking the arguments", async () => {
+		const { modelRuntime } = await setup(bothMethods);
+		const terminal = scriptedTerminal([], false);
+		expect(await run([PROVIDER_ID], modelRuntime, terminal)).toBe(1);
+		expect(terminal.errors).toEqual([
+			'"pi auth login <provider> [--api-key] [--no-browser]" requires an interactive terminal',
+		]);
+	});
+
+	test("signs in with an account in the browser without asking for a method", async () => {
+		const { credentials, modelRuntime } = await setup(bothMethods);
+		const terminal = scriptedTerminal(["the-code"]);
+		// Matches the provider name as well as the id.
+		expect(await run(["login test"], modelRuntime, terminal)).toBe(0);
+		expect(terminal.questions).toEqual(["Paste the code: "]);
+		expect(terminal.lines).toContain("Open this URL to sign in:\n  https://example.test/authorize");
+		expect(terminal.lines).toContain("Finish in the browser");
+		expect(terminal.opened).toEqual(["https://example.test/authorize"]);
+		expect(terminal.lines).toContain(
+			'To use "Sign in with device code" instead, run "pi auth login login-test --no-browser"',
+		);
+		expect(await credentials.read(PROVIDER_ID)).toMatchObject({ type: "oauth", access: "access-the-code" });
+		expect(terminal.lines.some((line) => line.startsWith("Logged in to Login Test."))).toBe(true);
+	});
+
+	test("lists several other sign-in methods", async () => {
+		const { modelRuntime } = await setup({
+			oauth: {
+				...bothMethods.oauth!,
+				login: async (interaction) => {
+					await interaction.prompt({
+						type: "select",
+						message: "Sign in to Login Test:",
+						options: [
+							{ id: "browser", label: "Browser" },
+							{ id: "device", label: "Device code" },
+							{ id: "copy", label: "Copy code" },
+						],
+					});
+					interaction.notify({ type: "auth_url", url: "https://example.test/authorize" });
+					return { type: "oauth", access: "access", refresh: "refresh", expires: Date.now() + 3_600_000 };
+				},
+			},
+		});
+		const terminal = scriptedTerminal([]);
+		expect(await run([PROVIDER_ID], modelRuntime, terminal)).toBe(0);
+		expect(terminal.lines).toContain(
+			'Other sign-in methods: "Device code", "Copy code". Run "pi auth login login-test --no-browser" to choose one.',
+		);
+	});
+
+	test("offers no other sign-in methods when the provider has no method choice", async () => {
+		const { credentials, modelRuntime } = await setup({
+			oauth: {
+				...bothMethods.oauth!,
+				login: async (interaction) => {
+					interaction.notify({ type: "auth_url", url: "https://example.test/authorize" });
+					const code = await interaction.prompt({ type: "manual_code", message: "Paste the code" });
+					return { type: "oauth", access: `access-${code}`, refresh: "refresh", expires: Date.now() + 3_600_000 };
+				},
+			},
+		});
+		const terminal = scriptedTerminal(["the-code"]);
+		expect(await run([PROVIDER_ID], modelRuntime, terminal)).toBe(0);
+		expect(terminal.opened).toEqual(["https://example.test/authorize"]);
+		expect(terminal.lines.some((line) => line.includes("--no-browser"))).toBe(false);
+		expect(await credentials.read(PROVIDER_ID)).toMatchObject({ type: "oauth", access: "access-the-code" });
+	});
+
+	test("--no-browser takes the only other sign-in method and opens nothing", async () => {
+		const { credentials, modelRuntime } = await setup(bothMethods);
+		const terminal = scriptedTerminal([]);
+		expect(await run([PROVIDER_ID, "--no-browser"], modelRuntime, terminal)).toBe(0);
+		expect(terminal.questions).toEqual([]);
+		expect(terminal.lines[0]).toBe("Sign in to Login Test: Sign in with device code");
+		expect(terminal.lines).toContain("Open https://example.test/device and enter code: ABCD-1234");
+		expect(terminal.opened).toEqual([]);
+		expect(terminal.lines.some((line) => line.includes("--no-browser"))).toBe(false);
+		expect(await credentials.read(PROVIDER_ID)).toMatchObject({ type: "oauth", access: "access-device" });
+	});
+
+	test("--no-browser asks among several other sign-in methods and re-asks on an invalid selection", async () => {
+		const { credentials, modelRuntime } = await setup({
+			oauth: {
+				...bothMethods.oauth!,
+				login: async (interaction) => {
+					const method = await interaction.prompt({
+						type: "select",
+						message: "Sign in to Login Test:",
+						options: [
+							{ id: "browser", label: "Browser" },
+							{ id: "device", label: "Device code" },
+							{ id: "copy", label: "Copy code" },
+						],
+					});
+					return {
+						type: "oauth",
+						access: `access-${method}`,
+						refresh: "refresh",
+						expires: Date.now() + 3_600_000,
+					};
+				},
+			},
+		});
+		const terminal = scriptedTerminal(["7", "2"]);
+		expect(await run(["--no-browser", PROVIDER_ID], modelRuntime, terminal)).toBe(0);
+		expect(terminal.lines.slice(0, 3)).toEqual(["Sign in to Login Test:", "  1. Device code", "  2. Copy code"]);
+		expect(terminal.lines).toContain("Enter a number from 1 to 2.");
+		expect(await credentials.read(PROVIDER_ID)).toMatchObject({ type: "oauth", access: "access-copy" });
+	});
+
+	test("--no-browser keeps a provider's only sign-in method without opening the browser", async () => {
+		const { credentials, modelRuntime } = await setup({
+			oauth: {
+				...bothMethods.oauth!,
+				login: async (interaction) => {
+					const method = await interaction.prompt({
+						type: "select",
+						message: "Sign in to Login Test:",
+						options: [{ id: "browser", label: "Browser" }],
+					});
+					interaction.notify({ type: "auth_url", url: "https://example.test/authorize" });
+					return {
+						type: "oauth",
+						access: `access-${method}`,
+						refresh: "refresh",
+						expires: Date.now() + 3_600_000,
+					};
+				},
+			},
+		});
+		const terminal = scriptedTerminal([]);
+		expect(await run([PROVIDER_ID, "--no-browser"], modelRuntime, terminal)).toBe(0);
+		expect(terminal.questions).toEqual([]);
+		expect(terminal.opened).toEqual([]);
+		expect(await credentials.read(PROVIDER_ID)).toMatchObject({ type: "oauth", access: "access-browser" });
+	});
+
+	test("asks for selections during API key setup", async () => {
+		const { credentials, modelRuntime } = await setup({
+			apiKey: {
+				...bothMethods.apiKey!,
+				login: async (interaction) => ({
+					type: "api_key",
+					key: await interaction.prompt({
+						type: "select",
+						message: "Choose credentials:",
+						options: [
+							{ id: "first", label: "First" },
+							{ id: "second", label: "Second", description: "Other credentials" },
+						],
+					}),
+				}),
+			},
+		});
+		const terminal = scriptedTerminal(["2"]);
+		expect(await run([PROVIDER_ID, "--api-key"], modelRuntime, terminal)).toBe(0);
+		expect(terminal.questions).toEqual(["Select 1-2: "]);
+		expect(terminal.lines).toContain("  2. Second - Other credentials");
+		expect(await credentials.read(PROVIDER_ID)).toMatchObject({ type: "api_key", key: "second" });
+	});
+
+	test("cancels a pending prompt without cancelling the login when the browser callback wins", async () => {
+		const promptController = new AbortController();
+		const { credentials, modelRuntime } = await setup({
+			oauth: {
+				...bothMethods.oauth!,
+				login: async (interaction) => {
+					const pending = interaction.prompt({
+						type: "manual_code",
+						message: "Paste the code",
+						placeholder: "redirect URL",
+						signal: promptController.signal,
+					});
+					promptController.abort();
+					await expect(pending).rejects.toBe(promptController.signal.reason);
+					expect(interaction.signal.aborted).toBe(false);
+					return { type: "oauth", access: "callback", refresh: "refresh", expires: Date.now() + 3_600_000 };
+				},
+			},
+		});
+		const terminal = scriptedTerminal([]);
+		terminal.question = vi.fn(
+			(_message: string, signal: AbortSignal) =>
+				new Promise<string>((_resolve, reject) => {
+					signal.addEventListener("abort", () => reject(signal.reason), { once: true });
+				}),
+		);
+		expect(await run([PROVIDER_ID], modelRuntime, terminal)).toBe(0);
+		expect(terminal.question).toHaveBeenCalledWith("Paste the code (redirect URL): ", expect.any(AbortSignal));
+		expect(await credentials.read(PROVIDER_ID)).toMatchObject({ type: "oauth", access: "callback" });
+	});
+
+	test("reports a committed login separately from a failed login", async () => {
+		const { modelRuntime } = await setup(bothMethods);
+		vi.spyOn(modelRuntime, "login").mockRejectedValue(
+			new CredentialSynchronizationError(
+				PROVIDER_ID,
+				"login",
+				{ type: "api_key", key: "saved" },
+				{ cause: new Error("snapshot failed") },
+			),
+		);
+		const terminal = scriptedTerminal([]);
+		expect(await run([PROVIDER_ID], modelRuntime, terminal)).toBe(1);
+		expect(terminal.errors[0]).toContain("Logged in to Login Test, but local model state could not be synchronized:");
+	});
+
+	test("--api-key saves an API key", async () => {
+		const { credentials, modelRuntime } = await setup(bothMethods);
+		const terminal = scriptedTerminal(["sk-test"]);
+		expect(await run([PROVIDER_ID, "--api-key"], modelRuntime, terminal)).toBe(0);
+		expect(terminal.questions).toEqual(["Enter Login Test API key: "]);
+		expect(await credentials.read(PROVIDER_ID)).toMatchObject({ type: "api_key", key: "sk-test" });
+		expect(terminal.lines.some((line) => line.startsWith("Saved API key for Login Test."))).toBe(true);
+	});
+
+	test("uses the API key login of providers without account sign-in", async () => {
+		const { modelRuntime } = await setup({ apiKey: bothMethods.apiKey });
+		const terminal = scriptedTerminal(["sk-test"]);
+		expect(await run([PROVIDER_ID], modelRuntime, terminal)).toBe(0);
+		expect(terminal.questions).toEqual(["Enter Login Test API key: "]);
+	});
+
+	test("--api-key fails for providers without API key login", async () => {
+		const { modelRuntime } = await setup({ oauth: bothMethods.oauth });
+		const terminal = scriptedTerminal([]);
+		expect(await run([PROVIDER_ID, "--api-key"], modelRuntime, terminal)).toBe(1);
+		expect(terminal.errors).toEqual(["Login Test has no API key login. Omit --api-key to sign in."]);
+	});
+
+	test("reports providers configured outside pi", async () => {
+		const { modelRuntime } = await setup({ apiKey: { name: "AWS profile", resolve: async () => undefined } });
+		const terminal = scriptedTerminal([]);
+		expect(await run([PROVIDER_ID], modelRuntime, terminal)).toBe(1);
+		expect(terminal.errors).toEqual(["Login Test is configured outside pi (AWS profile)."]);
+	});
+
+	test("Ctrl+C during the catalog refresh skips it and keeps the login", async () => {
+		const { credentials, modelRuntime } = await setup({ apiKey: bothMethods.apiKey });
+		const controller = new AbortController();
+		// A refresh that only ends when aborted, interrupted as soon as it starts.
+		vi.spyOn(modelRuntime, "refresh").mockImplementation(
+			({ signal } = {}) =>
+				new Promise((resolve) => {
+					signal?.addEventListener("abort", () => resolve({ aborted: true, errors: new Map() }));
+					controller.abort();
+				}),
+		);
+		const terminal = scriptedTerminal(["sk-test"]);
+		expect(await run([PROVIDER_ID], modelRuntime, terminal, controller.signal)).toBe(0);
+		expect(terminal.lines).toContain("Skipped the Login Test model catalog refresh; pi refreshes it on next start.");
+		expect(await credentials.read(PROVIDER_ID)).toMatchObject({ type: "api_key", key: "sk-test" });
+	});
+
+	test("reports cancellation", async () => {
+		const { credentials, modelRuntime } = await setup({ apiKey: bothMethods.apiKey });
+		const controller = new AbortController();
+		controller.abort();
+		const terminal = scriptedTerminal(["sk-test"]);
+		expect(await run([PROVIDER_ID], modelRuntime, terminal, controller.signal)).toBe(1);
+		expect(terminal.errors).toEqual(["Login cancelled."]);
+		expect(await credentials.read(PROVIDER_ID)).toBeUndefined();
+	});
+
+	test.each(["radius-mcp", "radius_mcp"])("keeps unrelated MCP servers when %s is occupied", async (fallback) => {
+		const agentDir = mkdtempSync(join(tmpdir(), "pi-auth-login-"));
+		try {
+			const { modelRuntime } = await setup({ apiKey: bothMethods.apiKey }, "radius");
+			const mcpPath = join(agentDir, "mcp.json");
+			const servers = {
+				radius: { command: "original-one" },
+				[fallback]: { command: "original-two" },
+				"radius-mcp-2": { command: "original-three" },
+			};
+			writeFileSync(mcpPath, JSON.stringify({ mcpServers: servers }));
+			const terminal = scriptedTerminal(["sk-test"]);
+			expect(await run(["radius"], modelRuntime, terminal, undefined, agentDir)).toBe(0);
+			expect(JSON.parse(readFileSync(mcpPath, "utf8")).mcpServers).toEqual({
+				...servers,
+				"radius-mcp-3": { url: "https://radius.pi.dev/mcp", auth: { provider: "radius" } },
+			});
+			expect(terminal.lines).toContain(`Added MCP server "radius-mcp-3" in ${mcpPath} to use the Login Test login.`);
+		} finally {
+			rmSync(agentDir, { recursive: true, force: true });
+		}
+	});
+
+	test("configures the Radius MCP server without asking, once", async () => {
+		const agentDir = mkdtempSync(join(tmpdir(), "pi-auth-login-"));
+		try {
+			const { modelRuntime } = await setup({ apiKey: bothMethods.apiKey }, "radius");
+			const mcpPath = join(agentDir, "mcp.json");
+			const first = scriptedTerminal(["sk-test"]);
+			expect(await run(["radius"], modelRuntime, first, undefined, agentDir)).toBe(0);
+			expect(first.questions).toEqual(["Enter Login Test API key: "]);
+			expect(first.lines).toContain(`Added MCP server "radius" in ${mcpPath} to use the Login Test login.`);
+			expect(JSON.parse(readFileSync(mcpPath, "utf8")).mcpServers.radius).toMatchObject({
+				auth: { provider: "radius" },
+			});
+
+			const second = scriptedTerminal(["sk-test"]);
+			expect(await run(["radius"], modelRuntime, second, undefined, agentDir)).toBe(0);
+			expect(second.lines.some((line) => line.includes("MCP server"))).toBe(false);
+		} finally {
+			rmSync(agentDir, { recursive: true, force: true });
+		}
+	});
+});
diff --git a/packages/coding-agent/test/auth-logout.test.ts b/packages/coding-agent/test/auth-logout.test.ts
new file mode 100644
index 000000000..5f050e07e
--- /dev/null
+++ b/packages/coding-agent/test/auth-logout.test.ts
@@ -0,0 +1,99 @@
+import { type Credential, InMemoryModelsStore } from "@earendil-works/pi-ai";
+import { describe, expect, test, vi } from "vitest";
+import { runAuthLogout } from "../src/cli/auth-logout.ts";
+import { AuthStorage } from "../src/core/auth-storage.ts";
+import { CredentialSynchronizationError, ModelRuntime } from "../src/core/model-runtime.ts";
+
+async function setup(data: Record<string, Credential>) {
+	const credentials = AuthStorage.inMemory(data);
+	const modelRuntime = await ModelRuntime.create({
+		credentials,
+		modelsPath: null,
+		modelsStore: new InMemoryModelsStore(),
+		allowModelNetwork: false,
+	});
+	const lines: string[] = [];
+	const errors: string[] = [];
+	const run = (args: string[]) =>
+		runAuthLogout(args, {
+			modelRuntime,
+			terminal: { write: (line) => lines.push(line), error: (line) => errors.push(line) },
+			signal: new AbortController().signal,
+		});
+	return { credentials, modelRuntime, lines, errors, run };
+}
+
+const oauthCredential = {
+	type: "oauth",
+	access: "access",
+	refresh: "refresh",
+	expires: Date.now() + 3_600_000,
+} as const;
+
+describe("pi auth logout", () => {
+	test("requires exactly one provider", async () => {
+		const { errors, run } = await setup({});
+		for (const args of [[], ["--api-key"], ["radius", "extra"]]) {
+			errors.length = 0;
+			expect(await run(args)).toBe(1);
+			expect(errors).toEqual(["Usage: pi auth logout <provider>"]);
+		}
+	});
+
+	test("removes a stored account login", async () => {
+		const { credentials, lines, run } = await setup({ radius: oauthCredential });
+		expect(await run(["radius"])).toBe(0);
+		expect(lines).toEqual(["Logged out of Radius."]);
+		expect(await credentials.read("radius")).toBeUndefined();
+	});
+
+	test("removes a stored API key by provider name and keeps other credentials", async () => {
+		const { credentials, lines, run } = await setup({
+			openai: { type: "api_key", key: "sk-test" },
+			radius: oauthCredential,
+		});
+		expect(await run(["OpenAI"])).toBe(0);
+		expect(lines).toEqual([
+			"Removed stored API key for OpenAI. Environment variables and models.json config are unchanged.",
+		]);
+		expect(await credentials.read("openai")).toBeUndefined();
+		expect(await credentials.read("radius")).toMatchObject({ type: "oauth" });
+	});
+
+	test("succeeds when nothing is stored, so it can be repeated", async () => {
+		const { lines, run } = await setup({});
+		expect(await run(["radius"])).toBe(0);
+		expect(lines).toEqual([
+			"No stored credentials for Radius. Environment variables and models.json config are unchanged.",
+		]);
+	});
+
+	test("removes credentials of providers that are not loaded, matched by id", async () => {
+		const { credentials, lines, run } = await setup({ "extension-provider": oauthCredential });
+		expect(await run(["extension-provider"])).toBe(0);
+		expect(lines).toEqual(["Logged out of extension-provider."]);
+		expect(await credentials.read("extension-provider")).toBeUndefined();
+	});
+
+	test("reports credential removal failures", async () => {
+		const { modelRuntime, errors, run } = await setup({ radius: oauthCredential });
+		vi.spyOn(modelRuntime, "logout").mockRejectedValue(new Error("storage failed"));
+		expect(await run(["radius"])).toBe(1);
+		expect(errors).toEqual(["Logout failed: storage failed"]);
+	});
+
+	test("reports committed credential removal separately from a failed logout", async () => {
+		const { modelRuntime, errors, run } = await setup({ radius: oauthCredential });
+		vi.spyOn(modelRuntime, "logout").mockRejectedValue(
+			new CredentialSynchronizationError("radius", "logout", undefined, { cause: new Error("snapshot failed") }),
+		);
+		expect(await run(["radius"])).toBe(1);
+		expect(errors[0]).toContain("Credentials removed for Radius, but local model state could not be synchronized:");
+	});
+
+	test("rejects an unknown provider and lists the stored credentials", async () => {
+		const { errors, run } = await setup({ radius: oauthCredential });
+		expect(await run(["nope"])).toBe(1);
+		expect(errors).toEqual(['Unknown provider "nope".', "Stored credentials: radius"]);
+	});
+});
diff --git a/packages/coding-agent/test/auth-terminal.test.ts b/packages/coding-agent/test/auth-terminal.test.ts
new file mode 100644
index 000000000..b433234d7
--- /dev/null
+++ b/packages/coding-agent/test/auth-terminal.test.ts
@@ -0,0 +1,63 @@
+import { PassThrough } from "node:stream";
+import { afterEach, describe, expect, test, vi } from "vitest";
+import { createProcessLoginTerminal } from "../src/cli/auth-terminal.ts";
+
+const inputs: PassThrough[] = [];
+
+afterEach(() => {
+	vi.restoreAllMocks();
+	for (const input of inputs) input.destroy();
+	inputs.length = 0;
+});
+
+function setup() {
+	const input = new PassThrough();
+	inputs.push(input);
+	// Readline only needs the readable stream; the test does not exercise TTY detection or raw mode.
+	vi.spyOn(process, "stdin", "get").mockReturnValue(input as unknown as typeof process.stdin);
+	vi.spyOn(process.stdout, "write").mockReturnValue(true);
+	const controller = new AbortController();
+	const interrupt = vi.fn(() => controller.abort());
+	const terminal = createProcessLoginTerminal(interrupt);
+	return { input, controller, interrupt, terminal };
+}
+
+describe("auth terminal questions", () => {
+	test("rejects and cancels the login when stdin closes before an answer", async () => {
+		const { input, controller, interrupt, terminal } = setup();
+		const answer = terminal.question("Enter domain: ", controller.signal);
+		const rejected = expect(answer).rejects.toMatchObject({ name: "AbortError" });
+		input.end();
+		await rejected;
+		expect(interrupt).toHaveBeenCalledOnce();
+		expect(controller.signal.aborted).toBe(true);
+	});
+
+	test("normal cleanup does not cancel the login after an answer", async () => {
+		const { input, controller, interrupt, terminal } = setup();
+		const answer = terminal.question("Enter domain: ", controller.signal);
+		input.write("example.com\n");
+		await expect(answer).resolves.toBe("example.com");
+		expect(interrupt).not.toHaveBeenCalled();
+		expect(controller.signal.aborted).toBe(false);
+	});
+
+	test("keeps an answer delivered immediately before EOF", async () => {
+		const { input, controller, interrupt, terminal } = setup();
+		const answer = terminal.question("Enter domain: ", controller.signal);
+		input.end("example.com\n");
+		await expect(answer).resolves.toBe("example.com");
+		expect(interrupt).not.toHaveBeenCalled();
+	});
+
+	test("prompt cancellation does not cancel the whole login", async () => {
+		const { controller, interrupt, terminal } = setup();
+		const prompt = new AbortController();
+		const answer = terminal.question("Paste code: ", AbortSignal.any([controller.signal, prompt.signal]));
+		const rejected = expect(answer).rejects.toMatchObject({ name: "AbortError" });
+		prompt.abort();
+		await rejected;
+		expect(interrupt).not.toHaveBeenCalled();
+		expect(controller.signal.aborted).toBe(false);
+	});
+});
diff --git a/packages/coding-agent/test/mcp-command.test.ts b/packages/coding-agent/test/mcp-command.test.ts
index 5f09b37eb..c3d55471f 100644
--- a/packages/coding-agent/test/mcp-command.test.ts
+++ b/packages/coding-agent/test/mcp-command.test.ts
@@ -110,7 +110,7 @@ describe("pi mcp", () => {
 			for (const command of ["login", "logout"]) {
 				expect(await run([command, "radius"], radius)).toMatchObject({
 					exitCode: 1,
-					output: `MCP server "radius" uses the credentials of provider "radius". Run /${command} radius in pi.`,
+					output: `MCP server "radius" uses the credentials of provider "radius". Run "pi auth ${command} radius".`,
 				});
 			}
 		} finally {
diff --git a/packages/coding-agent/test/provider-matching.test.ts b/packages/coding-agent/test/provider-matching.test.ts
new file mode 100644
index 000000000..5ab3b1b15
--- /dev/null
+++ b/packages/coding-agent/test/provider-matching.test.ts
@@ -0,0 +1,35 @@
+import { describe, expect, test } from "vitest";
+import { findMatchingProviders } from "../src/core/provider-matching.ts";
+
+const providers = [
+	{ id: "first", name: "Shared Name", authType: "oauth" },
+	{ id: "first", name: "Shared Name", authType: "api_key" },
+	{ id: "other", name: "FIRST", authType: "api_key" },
+	{ id: "second", name: "Second Provider", authType: "oauth" },
+];
+
+describe("provider reference matching", () => {
+	test("matches IDs and display names case-insensitively with surrounding whitespace", () => {
+		expect(findMatchingProviders(providers, "  sEcOnD  ")).toEqual([providers[3]]);
+		expect(findMatchingProviders(providers, "\tSECOND PROVIDER\n")).toEqual([providers[3]]);
+	});
+
+	test("keeps all matching providers and auth methods in input order", () => {
+		const matched = findMatchingProviders(providers, "first");
+		expect(matched).toEqual(providers.slice(0, 3));
+		expect(matched[0]).toBe(providers[0]);
+		expect(matched[1]?.authType).toBe("api_key");
+		expect(findMatchingProviders(providers, "shared name")).toEqual(providers.slice(0, 2));
+	});
+
+	test("does not fuzzy-match unknown or partial references", () => {
+		expect(findMatchingProviders(providers, "unknown")).toEqual([]);
+		expect(findMatchingProviders(providers, "sec")).toEqual([]);
+		expect(findMatchingProviders([], "first")).toEqual([]);
+	});
+
+	test("never matches an empty reference, even against empty display names", () => {
+		expect(findMatchingProviders([{ id: "unnamed", name: "" }], "")).toEqual([]);
+		expect(findMatchingProviders(providers, " \t ")).toEqual([]);
+	});
+});
diff --git a/packages/coding-agent/test/terminal-question.test.ts b/packages/coding-agent/test/terminal-question.test.ts
new file mode 100644
index 000000000..67dc26e5f
--- /dev/null
+++ b/packages/coding-agent/test/terminal-question.test.ts
@@ -0,0 +1,79 @@
+import { PassThrough } from "node:stream";
+import { afterEach, describe, expect, test, vi } from "vitest";
+import { questionTerminal } from "../src/utils/terminal-question.ts";
+
+const streams: PassThrough[] = [];
+
+afterEach(() => {
+	vi.restoreAllMocks();
+	for (const stream of streams) stream.destroy();
+	streams.length = 0;
+});
+
+function setup() {
+	const input = new PassThrough();
+	const output = new PassThrough();
+	streams.push(input, output);
+	// Readline only needs the stream; real terminal capabilities are added by the Ctrl+C test below.
+	vi.spyOn(process, "stdin", "get").mockReturnValue(input as unknown as typeof process.stdin);
+	const controller = new AbortController();
+	const onInterrupt = vi.fn();
+	return { input, output, controller, onInterrupt };
+}
+
+describe("terminal questions", () => {
+	test("writes to the selected output and cleans up after an answer", async () => {
+		const { input, output, controller, onInterrupt } = setup();
+		const answer = questionTerminal("Paste URL: ", { output, signal: controller.signal, onInterrupt });
+		expect(output.read()?.toString()).toBe("Paste URL: ");
+		input.write("https://example.test/callback\n");
+		await expect(answer).resolves.toBe("https://example.test/callback");
+		expect(onInterrupt).not.toHaveBeenCalled();
+		expect(input.listenerCount("data")).toBe(0);
+		expect(input.isPaused()).toBe(true);
+	});
+
+	test("rejects on EOF without requiring an interrupt callback", async () => {
+		const { input, output, controller } = setup();
+		const answer = questionTerminal("Paste URL: ", { output, signal: controller.signal });
+		const rejected = expect(answer).rejects.toMatchObject({ name: "AbortError" });
+		input.end();
+		await rejected;
+		expect(input.listenerCount("data")).toBe(0);
+	});
+
+	test("Ctrl+C rejects the question and reports an interrupt", async () => {
+		const { input, output, controller, onInterrupt } = setup();
+		const setRawMode = vi.fn();
+		Object.assign(input, { setRawMode });
+		Object.assign(output, { isTTY: true });
+		const answer = questionTerminal("Paste URL: ", { output, signal: controller.signal, onInterrupt });
+		const rejected = expect(answer).rejects.toMatchObject({ name: "AbortError" });
+		input.write("\u0003");
+		await rejected;
+		expect(onInterrupt).toHaveBeenCalledOnce();
+		expect(input.listenerCount("keypress")).toBe(0);
+		expect(output.listenerCount("resize")).toBe(0);
+		expect(setRawMode).toHaveBeenLastCalledWith(false);
+	});
+
+	test("caller cancellation does not report an interrupt", async () => {
+		const { input, output, controller, onInterrupt } = setup();
+		const answer = questionTerminal("Paste URL: ", { output, signal: controller.signal, onInterrupt });
+		const rejected = expect(answer).rejects.toMatchObject({ name: "AbortError" });
+		controller.abort();
+		await rejected;
+		expect(onInterrupt).not.toHaveBeenCalled();
+		expect(input.listenerCount("data")).toBe(0);
+	});
+
+	test("rejects an already-aborted prompt and cleans up", async () => {
+		const { input, output, controller, onInterrupt } = setup();
+		controller.abort();
+		await expect(
+			questionTerminal("Paste URL: ", { output, signal: controller.signal, onInterrupt }),
+		).rejects.toMatchObject({ name: "AbortError" });
+		expect(onInterrupt).not.toHaveBeenCalled();
+		expect(input.listenerCount("data")).toBe(0);
+	});
+});