From 6c01ac1c1bc91d7b839cb207c92f2a45627ee544 Mon Sep 17 00:00:00 2001
From: Harvmaster <hzuccon@gmail.com>
Date: Mon, 11 May 2026 10:41:41 +0000
Subject: [PATCH] Add currency settings, Settings service, and dialog to select
 fiat currency. Add support for non Official currencies like DOGE when using
 rates.

---
 src/cli/README.md                             |  18 +-
 src/cli/autocomplete/complete.ts              |  11 +-
 src/cli/autocomplete/completions.ts           |   5 +
 src/cli/autocomplete/scripts/bash.sh          |  11 +
 src/cli/autocomplete/scripts/fish.fish        |   1 +
 src/cli/autocomplete/scripts/zsh.zsh          |  11 +
 src/cli/commands/index.ts                     |   1 +
 src/cli/commands/settings.ts                  | 131 ++++++++++++
 src/cli/index.ts                              |  36 +++-
 src/services/app.ts                           |  14 +-
 src/services/rates.ts                         |  28 ++-
 src/services/settings.ts                      | 194 ++++++++++++++++++
 .../components/CurrencySelectionDialog.tsx    | 188 +++++++++++++++++
 src/tui/components/VariableInputField.tsx     |   2 +-
 src/tui/hooks/useSatoshisConversion.tsx       |  37 +++-
 src/tui/screens/WalletState.tsx               | 121 ++++++++++-
 .../action-wizard/steps/InputsStep.tsx        |   2 +-
 .../action-wizard/steps/ReviewStep.tsx        |   2 +-
 .../screens/invitations/InvitationScreen.tsx  |   2 +-
 .../steps/InputsSelectStep.tsx                |   2 +-
 .../steps/PreviewInvitationStep.tsx           |   2 +-
 .../invitation-import/steps/ReviewStep.tsx    |   2 +-
 src/utils/paths.ts                            |  11 +-
 src/utils/rates/base-rates.ts                 |  29 ++-
 src/utils/rates/rates-oracles.ts              |  70 ++++++-
 tests/cli/commands/settings.test.ts           |  83 ++++++++
 tests/cli/rates-format.test.ts                |  40 ++++
 tests/cli/settings.test.ts                    |  96 +++++++++
 28 files changed, 1102 insertions(+), 48 deletions(-)
 create mode 100644 src/cli/commands/settings.ts
 create mode 100644 src/services/settings.ts
 create mode 100644 src/tui/components/CurrencySelectionDialog.tsx
 create mode 100644 tests/cli/commands/settings.test.ts
 create mode 100644 tests/cli/rates-format.test.ts
 create mode 100644 tests/cli/settings.test.ts

diff --git a/src/cli/README.md b/src/cli/README.md
index 9da17ef..cfcaeb7 100644
--- a/src/cli/README.md
+++ b/src/cli/README.md
@@ -15,7 +15,7 @@ Wallet state lives under **`~/.config/xo-cli/`** (XDG-style), so you can run com
 | ----------------------------- | ----------------------------------------------------------------------- |
 | `~/.config/xo-cli/mnemonics/` | Mnemonic files (`mnemonic-*`)                                           |
 | `~/.config/xo-cli/data/`      | Engine DB (`xo-wallet.db`) and invitation storage (`xo-invitations.db`) |
-| `~/.config/xo-cli/.wallet`    | Last-used mnemonic reference (so `-m` can be omitted)                   |
+| `~/.config/xo-cli/.wallet`    | JSON settings (`default-mnemonic`, `currency`)                          |
 
 **Local to your shell’s current directory:** template JSON paths, invitation JSON you create/import, and any path you pass explicitly (e.g. `-m /abs/path/to/file`).
 
@@ -67,7 +67,10 @@ xo-cli mnemonic list
 
 ### Wallet Persistence
 
-The first time you pass `-m <name>`, that reference is saved to `~/.config/xo-cli/.wallet`. Later runs can omit `-m`.
+The first time you pass `-m <name>`, that reference is saved as
+`default-mnemonic` in `~/.config/xo-cli/.wallet`. Later runs can omit `-m`.
+
+`currency` controls the fiat unit used when showing BCH/sats conversions in the TUI.
 
 Mnemonic resolution order:
 
@@ -85,6 +88,7 @@ xo-cli resource list
 | Flag                           | Description                                         |
 | ------------------------------ | --------------------------------------------------- |
 | `-m`, `--mnemonic-file <file>` | Mnemonic file (basename, cwd-relative, or absolute) |
+| `--currency <code>`            | Fiat display currency (e.g. `USD`, `AUD`)            |
 | `-o`, `--output <filename>`    | Output filename (used by `mnemonic create`/`import`) |
 | `-v`, `--verbose`              | Verbose output                                      |
 | `-h`, `--help`                 | Help                                                |
@@ -126,6 +130,16 @@ xo-cli resource unreserve <txhash:vout>
 xo-cli resource unreserve-all
 ```
 
+### `settings` — Manage Persisted Settings
+
+```bash
+xo-cli settings show
+xo-cli settings get currency
+xo-cli settings get default-mnemonic
+xo-cli settings set currency AUD
+xo-cli settings set default-mnemonic mnemonic-nuclear
+```
+
 ### `receive` — Generate a Receiving Address
 
 ```bash
diff --git a/src/cli/autocomplete/complete.ts b/src/cli/autocomplete/complete.ts
index cd3bcdb..7e7e969 100644
--- a/src/cli/autocomplete/complete.ts
+++ b/src/cli/autocomplete/complete.ts
@@ -23,7 +23,7 @@
  *   1 - Error (no output, fails silently for shell integration)
  */
 
-import { existsSync, readdirSync, readFileSync } from "node:fs";
+import { existsSync, readdirSync } from "node:fs";
 import { join } from "node:path";
 import { createHash } from "node:crypto";
 
@@ -34,6 +34,7 @@ import {
 } from "../../utils/paths.js";
 import { loadMnemonic } from "../mnemonic.js";
 import { Storage } from "../../services/storage.js";
+import { SettingsService } from "../../services/settings.js";
 import { COMMAND_TREE } from "./completions.js";
 
 // Lazy-loaded modules (only loaded when needed for dynamic completions)
@@ -103,12 +104,8 @@ function listSubcommands(command: string, prefix?: string): void {
  */
 function getCurrentMnemonic(): string | null {
   try {
-    const walletConfigPath = getWalletConfigPath();
-    if (!existsSync(walletConfigPath)) {
-      return null;
-    }
-
-    const mnemonicFile = readFileSync(walletConfigPath, "utf8").trim();
+    const settings = new SettingsService(getWalletConfigPath());
+    const mnemonicFile = settings.getDefaultMnemonic();
     if (!mnemonicFile) {
       return null;
     }
diff --git a/src/cli/autocomplete/completions.ts b/src/cli/autocomplete/completions.ts
index 24fcb1f..01d1ebe 100644
--- a/src/cli/autocomplete/completions.ts
+++ b/src/cli/autocomplete/completions.ts
@@ -37,6 +37,7 @@ import { homedir } from "node:os";
  * - template.ts: import, list, inspect, set-default
  * - invitation.ts: create, append, sign, broadcast, requirements, import, inspect, list
  * - resource.ts: list, unreserve, unreserve-all
+ * - settings.ts: show, get, set
  */
 
 /** Subcommands for the mnemonic command */
@@ -56,6 +57,8 @@ const INVITATION_SUBS = [
 ];
 /** Subcommands for the resource command */
 const RESOURCE_SUBS = ["list", "unreserve", "unreserve-all"];
+/** Subcommands for the settings command */
+const SETTINGS_SUBS = ["show", "get", "set"];
 /** Subcommands for the completions command */
 const COMPLETIONS_SUBS = ["bash", "zsh", "fish"];
 
@@ -65,6 +68,7 @@ export const COMMAND_TREE = {
   invitation: INVITATION_SUBS,
   receive: [],
   resource: RESOURCE_SUBS,
+  settings: SETTINGS_SUBS,
   help: [],
   completions: COMPLETIONS_SUBS,
 } as const;
@@ -77,6 +81,7 @@ const GLOBAL_OPTIONS = [
   "--verbose",
   "-m",
   "--mnemonic-file",
+  "--currency",
   "-o",
   "--output",
 ];
diff --git a/src/cli/autocomplete/scripts/bash.sh b/src/cli/autocomplete/scripts/bash.sh
index 7c12ef4..45ad873 100644
--- a/src/cli/autocomplete/scripts/bash.sh
+++ b/src/cli/autocomplete/scripts/bash.sh
@@ -201,6 +201,17 @@ _{{FUNC_NAME}}_completions() {
       fi
       ;;
 
+    settings)
+      if [[ -z "${subcmd}" ]]; then
+        COMPREPLY=($(compgen -W "show get set" -- "${cur}"))
+      elif [[ "${subcmd}" == "get" || "${subcmd}" == "set" ]]; then
+        local pos=$((cword - subcmd_idx))
+        if [[ $pos -eq 1 ]]; then
+          COMPREPLY=($(compgen -W "currency default-mnemonic" -- "${cur}"))
+        fi
+      fi
+      ;;
+
     receive)
       # receive <template> [output]
       # Template is the first positional argument after `receive`.
diff --git a/src/cli/autocomplete/scripts/fish.fish b/src/cli/autocomplete/scripts/fish.fish
index 9a04311..b0c3bc6 100644
--- a/src/cli/autocomplete/scripts/fish.fish
+++ b/src/cli/autocomplete/scripts/fish.fish
@@ -35,6 +35,7 @@ complete -c {{BIN_NAME}} -s v -d "Verbose output"
 complete -c {{BIN_NAME}} -l verbose -d "Verbose output"
 complete -c {{BIN_NAME}} -s o -d "Output file"
 complete -c {{BIN_NAME}} -l output -d "Output file"
+complete -c {{BIN_NAME}} -l currency -d "Set fiat display currency"
 
 # Dynamic completion for `-m/--mnemonic-file`.
 complete -c {{BIN_NAME}} -s m -l mnemonic-file -xa '(__{{FUNC_NAME}}_complete_dynamic mnemonics)'
diff --git a/src/cli/autocomplete/scripts/zsh.zsh b/src/cli/autocomplete/scripts/zsh.zsh
index 61e080f..a11989f 100644
--- a/src/cli/autocomplete/scripts/zsh.zsh
+++ b/src/cli/autocomplete/scripts/zsh.zsh
@@ -180,6 +180,17 @@ _{{FUNC_NAME}}_completions() {
       fi
       ;;
 
+    settings)
+      if [[ -z "${subcmd}" ]]; then
+        compadd -- show get set
+      elif [[ "${subcmd}" == "get" || "${subcmd}" == "set" ]]; then
+        local pos=$((CURRENT - subcmd_idx))
+        if [[ $pos -eq 1 ]]; then
+          compadd -- currency default-mnemonic
+        fi
+      fi
+      ;;
+
     receive)
       # receive <template> [output]
       local pos=$((CURRENT - cmd_idx))
diff --git a/src/cli/commands/index.ts b/src/cli/commands/index.ts
index d729aa7..bf27939 100644
--- a/src/cli/commands/index.ts
+++ b/src/cli/commands/index.ts
@@ -1,4 +1,5 @@
 export { handleMnemonicCommand, printMnemonicHelp } from "./mnemonic.js";
+export { handleSettingsCommand, printSettingsHelp } from "./settings.js";
 export { handleTemplateCommand, printTemplateHelp } from "./template.js";
 export { handleInvitationCommand, printInvitationHelp } from "./invitation.js";
 export { handleReceiveCommand, printReceiveHelp } from "./receive.js";
diff --git a/src/cli/commands/settings.ts b/src/cli/commands/settings.ts
new file mode 100644
index 0000000..0b4fbff
--- /dev/null
+++ b/src/cli/commands/settings.ts
@@ -0,0 +1,131 @@
+import { SettingsService } from "../../services/settings.js";
+import { formatObject } from "../utils.js";
+import type { BaseCommandDependencies, CommandIO } from "./types.js";
+import { CommandError } from "./types.js";
+
+/**
+ * Prints help text for the settings command.
+ */
+export const printSettingsHelp = (io: CommandIO): void => {
+  io.out(`Settings Command Help:
+Commands:
+  settings show
+  settings get <currency|default-mnemonic>
+  settings set <currency|default-mnemonic> <value>
+
+Examples:
+  xo-cli settings show
+  xo-cli settings get currency
+  xo-cli settings set currency AUD
+  xo-cli settings set default-mnemonic mnemonic-main`);
+};
+
+/**
+ * Supported settings keys exposed on the CLI.
+ */
+type SettingsKey = "currency" | "default-mnemonic";
+
+/**
+ * Normalizes user input to one of the supported settings keys.
+ */
+function parseSettingsKey(input: string | undefined): SettingsKey | null {
+  if (!input) {
+    return null;
+  }
+
+  const normalized = input.trim().toLowerCase();
+  if (normalized === "currency") {
+    return "currency";
+  }
+  if (normalized === "default-mnemonic" || normalized === "defaultMnemonic") {
+    return "default-mnemonic";
+  }
+  return null;
+}
+
+/**
+ * Handles `xo-cli settings` commands.
+ *
+ * This command intentionally does not require wallet initialization so users can
+ * configure currency/default mnemonic without passing `-m`.
+ */
+export const handleSettingsCommand = async (
+  deps: BaseCommandDependencies,
+  args: string[],
+  options: Record<string, string>,
+): Promise<Record<string, unknown>> => {
+  const settings = new SettingsService(deps.paths.walletConfigPath);
+
+  // settings show (default if no subcommand)
+  const subCommand = args[0] ?? "show";
+  if (subCommand === "help" || options["help"] === "true") {
+    printSettingsHelp(deps.io);
+    return {};
+  }
+
+  switch (subCommand) {
+    case "show": {
+      const snapshot = settings.getSettings();
+      deps.io.out(formatObject(snapshot));
+      return snapshot;
+    }
+
+    case "get": {
+      const key = parseSettingsKey(args[1]);
+      if (!key) {
+        printSettingsHelp(deps.io);
+        throw new CommandError(
+          "settings.get.key_missing",
+          'Missing or invalid key. Expected "currency" or "default-mnemonic".',
+        );
+      }
+
+      const value =
+        key === "currency"
+          ? settings.getCurrency()
+          : settings.getDefaultMnemonic() ?? "";
+      deps.io.out(value);
+      return { key, value };
+    }
+
+    case "set": {
+      const key = parseSettingsKey(args[1]);
+      if (!key) {
+        printSettingsHelp(deps.io);
+        throw new CommandError(
+          "settings.set.key_missing",
+          'Missing or invalid key. Expected "currency" or "default-mnemonic".',
+        );
+      }
+
+      const rawValue = args.slice(2).join(" ").trim();
+      if (!rawValue) {
+        printSettingsHelp(deps.io);
+        throw new CommandError(
+          "settings.set.value_missing",
+          "Missing value for settings set command.",
+        );
+      }
+
+      if (key === "currency") {
+        settings.setCurrency(rawValue);
+        const currency = settings.getCurrency();
+        deps.io.out(`Updated currency: ${currency}`);
+        return { key, value: currency };
+      }
+
+      settings.setDefaultMnemonic(rawValue);
+      const defaultMnemonic = settings.getDefaultMnemonic() ?? "";
+      deps.io.out(`Updated default-mnemonic: ${defaultMnemonic}`);
+      return { key, value: defaultMnemonic };
+    }
+
+    default: {
+      printSettingsHelp(deps.io);
+      throw new CommandError(
+        "settings.subcommand.unknown",
+        `Unknown settings command: ${subCommand}`,
+      );
+    }
+  }
+};
diff --git a/src/cli/index.ts b/src/cli/index.ts
index 04874b5..ce272ef 100644
--- a/src/cli/index.ts
+++ b/src/cli/index.ts
@@ -35,10 +35,10 @@
  * -m --mnemonic-file <mnemonic-file>
  */
 
-import { existsSync, readFileSync, writeFileSync } from "fs";
 import { join } from "path";
 
 import { AppService } from "../services/app.js";
+import { SettingsService } from "../services/settings.js";
 import { convertArgsToObject } from "./arguments.js";
 import { bold, dim, formatObject } from "./utils.js";
 import { listGlobalMnemonicFiles, loadMnemonic } from "./mnemonic.js";
@@ -54,6 +54,7 @@ import {
   type CommandPaths,
   CommandError,
   handleMnemonicCommand,
+  handleSettingsCommand,
   handleTemplateCommand,
   handleInvitationCommand,
   handleReceiveCommand,
@@ -115,6 +116,7 @@ async function main(): Promise<void> {
     walletConfigPath: getWalletConfigPath(),
     workingDir: process.cwd(),
   };
+  const settings = new SettingsService(paths.walletConfigPath);
 
   // Early handling for completions command
   if (command === "completions") {
@@ -134,10 +136,26 @@ async function main(): Promise<void> {
     }
   }
 
-  // Resolve mnemonic file: explicit flag > persisted config > error.
+  if (command === "settings") {
+    try {
+      await handleSettingsCommand({ io, paths }, subArgs, options);
+      process.exit(0);
+    } catch (error) {
+      if (error instanceof CommandError) {
+        process.exit(error.code);
+      }
+      throw error;
+    }
+  }
+
+  // Resolve mnemonic file: explicit flag > persisted settings > error.
   let mnemonicFile = options["mnemonicFile"];
-  if (!mnemonicFile && existsSync(paths.walletConfigPath)) {
-    mnemonicFile = readFileSync(paths.walletConfigPath, "utf8").trim();
+  let didUsePersistedMnemonic = false;
+  if (!mnemonicFile) {
+    mnemonicFile = settings.getDefaultMnemonic();
+    didUsePersistedMnemonic = Boolean(mnemonicFile);
+  }
+  if (didUsePersistedMnemonic && mnemonicFile) {
     io.verbose(`Using persisted wallet: ${mnemonicFile}`);
   }
   if (!mnemonicFile) {
@@ -152,7 +170,11 @@ async function main(): Promise<void> {
   }
 
   // Persist the choice so subsequent commands can omit -m.
-  writeFileSync(paths.walletConfigPath, mnemonicFile);
+  settings.setDefaultMnemonic(mnemonicFile);
+  if (options["currency"]) {
+    settings.setCurrency(options["currency"]);
+    io.verbose(`Using configured currency: ${settings.getCurrency()}`);
+  }
 
   const mnemonic = loadMnemonic(paths.mnemonicsDir, mnemonicFile);
   io.verbose(`Loaded mnemonic from file: ${mnemonicFile} ${mnemonic}`);
@@ -168,7 +190,7 @@ async function main(): Promise<void> {
     invitationStoragePath:
       options["invitationStoragePath"] ??
       join(paths.dataDir, "xo-invitations.db"),
-  });
+  }, settings);
   io.verbose("App instance created");
 
   // Start the app
@@ -255,12 +277,14 @@ Commands:
   invitation  ${dim("Manage invitations")}
   receive     ${dim("Generate a single-use receiving address")}
   resource    ${dim("Manage resources")}
+  settings    ${dim("Manage persisted wallet settings")}
   completions ${dim("Generate shell completion scripts (bash, zsh, fish)")}
   help        ${dim("Show this help message")}
 
 Options:
   -h, --help    ${dim("Show this help message")}
   -m, --mnemonic-file <mnemonic-file>  ${dim("Use a specific mnemonic file")}
+  --currency <currency-code>  ${dim("Set fiat display currency (e.g. USD, AUD)")}
   -v, --verbose   ${dim("Show verbose output")}`,
   );
   return {};
diff --git a/src/services/app.ts b/src/services/app.ts
index e5e12b5..70d07a6 100644
--- a/src/services/app.ts
+++ b/src/services/app.ts
@@ -12,6 +12,7 @@ import { SyncServer } from "../utils/sync-server.js";
 import { HistoryService } from "./history.js";
 import { type BlockchainService, ElectrumService } from "./electrum.js";
 import { RatesService } from "./rates.js";
+import { SettingsService } from "./settings.js";
 
 import { EventEmitter } from "../utils/event-emitter.js";
 
@@ -49,6 +50,7 @@ export class AppService extends EventEmitter<AppEventMap> {
   public history: HistoryService;
   public electrum: BlockchainService;
   public rates: RatesService;
+  public settings: SettingsService;
 
   public invitations: Invitation[] = [];
   private invitationEventCleanup = new Map<
@@ -59,7 +61,11 @@ export class AppService extends EventEmitter<AppEventMap> {
     }
   >();
 
-  static async create(seed: string, config: AppConfig): Promise<AppService> {
+  static async create(
+    seed: string,
+    config: AppConfig,
+    settings: SettingsService = new SettingsService(),
+  ): Promise<AppService> {
     // Because of a bug that lets wallets read the unspents of other wallets, we are going to manually namespace the storage paths for the app.
     // We are going to do this by computing a hash of the seed and prefixing the storage paths with it.
     const seedHash = createHash("sha256").update(seed).digest("hex");
@@ -110,9 +116,9 @@ export class AppService extends EventEmitter<AppEventMap> {
       host: config.electrumHost,
       applicationIdentifier: config.electrumApplicationIdentifier,
     });
-    const rates = await RatesService.create();
+    const rates = await RatesService.create(settings);
 
-    return new AppService(engine, walletStorage, config, electrum, rates);
+    return new AppService(engine, walletStorage, config, electrum, rates, settings);
   }
 
   constructor(
@@ -121,6 +127,7 @@ export class AppService extends EventEmitter<AppEventMap> {
     config: AppConfig,
     electrum: BlockchainService,
     rates: RatesService,
+    settings: SettingsService,
   ) {
     super();
 
@@ -129,6 +136,7 @@ export class AppService extends EventEmitter<AppEventMap> {
     this.config = config;
     this.electrum = electrum;
     this.rates = rates;
+    this.settings = settings;
     this.history = new HistoryService(engine, this.invitations);
   }
 
diff --git a/src/services/rates.ts b/src/services/rates.ts
index eb5d45f..2d4719a 100644
--- a/src/services/rates.ts
+++ b/src/services/rates.ts
@@ -3,6 +3,7 @@ import {
   type RatesEventMap,
 } from '../utils/rates/base-rates.js';
 import { RatesOracle } from '../utils/rates/rates-oracles.js';
+import { SettingsService } from './settings.js';
 
 /**
  * Event map emitted by {@link RatesService}.
@@ -52,13 +53,15 @@ export interface RatesAdapter {
  */
 export class RatesService extends EventEmitter<RatesServiceEventMap> {
   private readonly adapter: RatesAdapter;
+  private readonly settings: SettingsService;
   private readonly ratesByPair = new Map<string, CachedRate>();
   private unsubscribeFromAdapter: (() => void) | null = null;
   private started = false;
 
-  constructor(adapter: RatesAdapter) {
+  constructor(adapter: RatesAdapter, settings: SettingsService) {
     super();
     this.adapter = adapter;
+    this.settings = settings;
   }
 
   /**
@@ -66,9 +69,12 @@ export class RatesService extends EventEmitter<RatesServiceEventMap> {
    *
    * If no adapter is passed, this defaults to the Oracle-backed adapter.
    */
-  public static async create(adapter?: RatesAdapter): Promise<RatesService> {
-    const resolvedAdapter = adapter ?? (await RatesOracle.from());
-    return new RatesService(resolvedAdapter);
+  public static async create(
+    settings: SettingsService,
+    adapter?: RatesAdapter,
+  ): Promise<RatesService> {
+    const resolvedAdapter = adapter ?? (await RatesOracle.from(undefined, settings));
+    return new RatesService(resolvedAdapter, settings);
   }
 
   /**
@@ -162,6 +168,20 @@ export class RatesService extends EventEmitter<RatesServiceEventMap> {
     return this.adapter.formatCurrency(amount, currencyCode.toUpperCase());
   }
 
+  /**
+   * Lists available market pairs in NUMERATOR/DENOMINATOR format.
+   */
+  public async listPairs(): Promise<Set<string>> {
+    return this.adapter.listPairs();
+  }
+
+  /**
+   * Returns the fiat currency currently configured in settings.
+   */
+  public getConfiguredCurrency(): string {
+    return this.settings.getCurrency();
+  }
+
   /**
    * Handles normalized updates from the underlying adapter.
    */
diff --git a/src/services/settings.ts b/src/services/settings.ts
new file mode 100644
index 0000000..19c3523
--- /dev/null
+++ b/src/services/settings.ts
@@ -0,0 +1,194 @@
+import { existsSync, readFileSync, writeFileSync } from "node:fs";
+
+import { EventEmitter } from "../utils/event-emitter.js";
+import { getSettingsPath } from "../utils/paths.js";
+
+/**
+ * Supported persisted settings keys.
+ */
+export type SettingsData = {
+  "default-mnemonic"?: string;
+  currency: string;
+};
+
+/**
+ * Event payloads emitted by {@link SettingsService}.
+ */
+export type SettingsServiceEventMap = {
+  "settings-updated": {
+    key: keyof SettingsData;
+    value: string | undefined;
+    settings: SettingsData;
+  };
+};
+
+/**
+ * Runtime defaults for settings that should always exist in memory.
+ */
+const DEFAULT_SETTINGS: SettingsData = {
+  currency: "USD",
+};
+
+/**
+ * Handles loading, migrating, and persisting wallet settings.
+ *
+ * The backing file is `~/.config/xo-cli/.wallet`. Historically it stored a raw
+ * mnemonic reference string. This service migrates that legacy format to JSON:
+ * `{ "default-mnemonic": "<value>", "currency": "USD" }`.
+ */
+export class SettingsService extends EventEmitter<SettingsServiceEventMap> {
+  private readonly settingsPath: string;
+  private settings: SettingsData;
+
+  /**
+   * Creates a new settings service instance.
+   *
+   * @param settingsPath - Optional custom settings file path (useful for tests)
+   */
+  constructor(settingsPath: string = getSettingsPath()) {
+    super();
+    this.settingsPath = settingsPath;
+    this.settings = this.loadSettings();
+  }
+
+  /**
+   * Returns the current settings snapshot.
+   */
+  public getSettings(): SettingsData {
+    return { ...this.settings };
+  }
+
+  /**
+   * Returns the currently selected default mnemonic reference.
+   */
+  public getDefaultMnemonic(): string | undefined {
+    return this.settings["default-mnemonic"];
+  }
+
+  /**
+   * Updates the default mnemonic reference and persists it to disk.
+   */
+  public setDefaultMnemonic(mnemonicRef: string): void {
+    const normalizedMnemonicRef = mnemonicRef.trim();
+    if (normalizedMnemonicRef.length === 0) {
+      throw new Error("default-mnemonic cannot be empty");
+    }
+
+    this.settings["default-mnemonic"] = normalizedMnemonicRef;
+    this.persistSettings();
+
+    this.emit("settings-updated", {
+      key: "default-mnemonic",
+      value: normalizedMnemonicRef,
+      settings: this.getSettings(),
+    });
+  }
+
+  /**
+   * Returns the selected fiat currency code (ISO-like uppercase).
+   */
+  public getCurrency(): string {
+    return this.settings.currency;
+  }
+
+  /**
+   * Updates the selected fiat currency and persists it to disk.
+   */
+  public setCurrency(currencyCode: string): void {
+    const normalizedCurrency = this.normalizeCurrency(currencyCode);
+    if (this.settings.currency === normalizedCurrency) {
+      return;
+    }
+
+    this.settings.currency = normalizedCurrency;
+    this.persistSettings();
+
+    this.emit("settings-updated", {
+      key: "currency",
+      value: normalizedCurrency,
+      settings: this.getSettings(),
+    });
+  }
+
+  /**
+   * Reads and normalizes the settings file from disk.
+   *
+   * If the file contains the old legacy format (raw mnemonic string), the
+   * migrated JSON shape is written back immediately.
+   */
+  private loadSettings(): SettingsData {
+    if (!existsSync(this.settingsPath)) {
+      return { ...DEFAULT_SETTINGS };
+    }
+
+    const rawContents = readFileSync(this.settingsPath, "utf8").trim();
+    if (rawContents.length === 0) {
+      return { ...DEFAULT_SETTINGS };
+    }
+
+    try {
+      const parsed = JSON.parse(rawContents);
+      const normalized = this.normalizeSettings(parsed);
+      return normalized;
+    } catch {
+      const migrated = this.normalizeSettings({
+        "default-mnemonic": rawContents,
+      });
+      this.persistSettings(migrated);
+      return migrated;
+    }
+  }
+
+  /**
+   * Writes the given settings object to disk as pretty JSON.
+   *
+   * @param nextSettings - Optional explicit value, defaults to in-memory state
+   */
+  private persistSettings(nextSettings?: SettingsData): void {
+    if (nextSettings) {
+      this.settings = nextSettings;
+    }
+
+    writeFileSync(
+      this.settingsPath,
+      `${JSON.stringify(this.settings, null, 2)}\n`,
+      "utf8",
+    );
+  }
+
+  /**
+   * Coerces unknown input into a safe settings object.
+   */
+  private normalizeSettings(input: unknown): SettingsData {
+    const normalized: SettingsData = {
+      ...DEFAULT_SETTINGS,
+    };
+
+    if (!input || typeof input !== "object") {
+      return normalized;
+    }
+
+    const maybeMnemonic = (input as Record<string, unknown>)["default-mnemonic"];
+    if (typeof maybeMnemonic === "string" && maybeMnemonic.trim().length > 0) {
+      normalized["default-mnemonic"] = maybeMnemonic.trim();
+    }
+
+    const maybeCurrency = (input as Record<string, unknown>).currency;
+    if (typeof maybeCurrency === "string" && maybeCurrency.trim().length > 0) {
+      normalized.currency = this.normalizeCurrency(maybeCurrency);
+    }
+
+    return normalized;
+  }
+
+  /**
+   * Ensures currency values stay uppercase and non-empty.
+   */
+  private normalizeCurrency(currencyCode: string): string {
+    const normalizedCurrency = currencyCode.trim().toUpperCase();
+    if (normalizedCurrency.length === 0) {
+      throw new Error("currency cannot be empty");
+    }
+    return normalizedCurrency;
+  }
+}
\ No newline at end of file
diff --git a/src/tui/components/CurrencySelectionDialog.tsx b/src/tui/components/CurrencySelectionDialog.tsx
new file mode 100644
index 0000000..b5e7859
--- /dev/null
+++ b/src/tui/components/CurrencySelectionDialog.tsx
@@ -0,0 +1,188 @@
+import React, { useEffect, useId, useMemo, useState } from "react";
+import { Box, Text } from "ink";
+
+import { ScrollableList, type ListItemData } from "./List.js";
+import TextInput from "./TextInput.js";
+import { DialogWrapper } from "./Dialog.js";
+import { useInputLayer, useLayeredInput } from "../hooks/useInputLayer.js";
+import { colors } from "../theme.js";
+
+/**
+ * Props for the currency selection dialog.
+ */
+interface CurrencySelectionDialogProps {
+  /** Current wallet currency from persisted settings. */
+  currentCurrency: string;
+  /** Available fiat numerator symbols that can be paired with BCH. */
+  currencies: string[];
+  /** True while the dialog is loading available pairs. */
+  isLoading: boolean;
+  /** Optional loading/error message for pair discovery. */
+  errorMessage: string | null;
+  /** Called when the user chooses a currency and confirms. */
+  onSelectCurrency: (currencyCode: string) => void;
+  /** Called when the dialog should close without applying changes. */
+  onCancel: () => void;
+}
+
+/**
+ * Currency picker dialog.
+ *
+ * UX requirements:
+ * - Arrow keys move the highlighted item.
+ * - Typing immediately filters results.
+ * - Enter applies current selection.
+ * - Escape closes without saving.
+ */
+export function CurrencySelectionDialog({
+  currentCurrency,
+  currencies,
+  isLoading,
+  errorMessage,
+  onSelectCurrency,
+  onCancel,
+}: CurrencySelectionDialogProps): React.ReactElement {
+  const layerId = useId();
+  const [filterText, setFilterText] = useState("");
+  const [selectedIndex, setSelectedIndex] = useState(0);
+
+  // Mount this as a capturing input layer so background screens stop handling keys.
+  useInputLayer(layerId);
+
+  /**
+   * Applies the currently selected filtered result.
+   */
+  const applySelection = (): void => {
+    const selectedCurrency = filteredCurrencies[selectedIndex];
+    if (!selectedCurrency) {
+      return;
+    }
+    onSelectCurrency(selectedCurrency);
+  };
+
+  useLayeredInput(layerId, (_input, key) => {
+    if (key.escape) {
+      onCancel();
+      return;
+    }
+
+    if (key.upArrow) {
+      setSelectedIndex((prev) =>
+        prev <= 0 ? Math.max(filteredCurrencies.length - 1, 0) : prev - 1,
+      );
+      return;
+    }
+
+    if (key.downArrow) {
+      setSelectedIndex((prev) =>
+        filteredCurrencies.length === 0
+          ? 0
+          : prev >= filteredCurrencies.length - 1
+            ? 0
+            : prev + 1,
+      );
+      return;
+    }
+
+  });
+
+  /**
+   * Filter currencies as the user types.
+   */
+  const filteredCurrencies = useMemo(() => {
+    const normalizedFilter = filterText.trim().toUpperCase();
+    if (!normalizedFilter) {
+      return currencies;
+    }
+    return currencies.filter((currencyCode) =>
+      currencyCode.toUpperCase().includes(normalizedFilter),
+    );
+  }, [currencies, filterText]);
+
+  /**
+   * Keep selected index valid whenever filtering shrinks the result set.
+   */
+  useEffect(() => {
+    if (filteredCurrencies.length === 0) {
+      setSelectedIndex(0);
+      return;
+    }
+
+    if (selectedIndex >= filteredCurrencies.length) {
+      setSelectedIndex(filteredCurrencies.length - 1);
+    }
+  }, [filteredCurrencies, selectedIndex]);
+
+  /**
+   * When the dialog opens or the list updates, default to current currency.
+   */
+  useEffect(() => {
+    if (filterText.trim().length > 0) {
+      return;
+    }
+
+    const currentIndex = filteredCurrencies.findIndex(
+      (currencyCode) => currencyCode.toUpperCase() === currentCurrency.toUpperCase(),
+    );
+    if (currentIndex >= 0) {
+      setSelectedIndex(currentIndex);
+    }
+  }, [filteredCurrencies, currentCurrency, filterText]);
+
+  const listItems: ListItemData<string>[] = filteredCurrencies.map(
+    (currencyCode) => ({
+      key: currencyCode,
+      label: currencyCode,
+      description:
+        currencyCode.toUpperCase() === currentCurrency.toUpperCase()
+          ? "(current)"
+          : undefined,
+      value: currencyCode,
+    }),
+  );
+
+  return (
+    <DialogWrapper title="Select Fiat Currency" borderColor={colors.info} width={64}>
+      <Text color={colors.textMuted}>
+        Available BCH quote pairs are loaded from the live rates adapter.
+      </Text>
+
+      <Box marginTop={1}>
+        <Text color={colors.primary}>Filter:</Text>
+      </Box>
+      <Box borderStyle="single" borderColor={colors.focus} paddingX={1}>
+        <TextInput
+          value={filterText}
+          onChange={setFilterText}
+          onSubmit={() => applySelection()}
+          placeholder="Type currency code (e.g. USD, AUD)..."
+          focus
+        />
+      </Box>
+
+      <Box marginTop={1} flexDirection="column">
+        {isLoading ? (
+          <Text color={colors.textMuted}>Loading available pairs...</Text>
+        ) : errorMessage ? (
+          <Text color={colors.error}>{errorMessage}</Text>
+        ) : (
+          <ScrollableList
+            items={listItems}
+            selectedIndex={selectedIndex}
+            onSelect={setSelectedIndex}
+            onActivate={() => applySelection()}
+            focus={false}
+            maxVisible={8}
+            emptyMessage="No BCH quote pairs match this filter."
+          />
+        )}
+      </Box>
+
+      <Box marginTop={1}>
+        <Text color={colors.textMuted}>
+          Type to filter • ↑↓ navigate • Enter apply • Esc cancel
+        </Text>
+      </Box>
+    </DialogWrapper>
+  );
+}
diff --git a/src/tui/components/VariableInputField.tsx b/src/tui/components/VariableInputField.tsx
index 7d5227b..b087434 100644
--- a/src/tui/components/VariableInputField.tsx
+++ b/src/tui/components/VariableInputField.tsx
@@ -68,7 +68,7 @@ export function VariableInputField({
   focusColor,
 }: VariableInputFieldProps): React.ReactElement {
   const { currencyCode, formattedFiatPerBchRate, formatSatoshisToFiat } =
-    useSatoshisConversion("USD");
+    useSatoshisConversion();
   const satoshisValue = useMemo(
     () => parseSatoshis(variable.value),
     [variable.value],
diff --git a/src/tui/hooks/useSatoshisConversion.tsx b/src/tui/hooks/useSatoshisConversion.tsx
index c934ff5..7630a7d 100644
--- a/src/tui/hooks/useSatoshisConversion.tsx
+++ b/src/tui/hooks/useSatoshisConversion.tsx
@@ -1,4 +1,4 @@
-import { useCallback, useMemo } from 'react';
+import { useCallback, useMemo, useSyncExternalStore } from 'react';
 import { useAppContext } from './useAppContext.js';
 import { useBchToFiatRate } from './useRates.js';
 
@@ -9,9 +9,40 @@ import { useBchToFiatRate } from './useRates.js';
  * component using it will re-render automatically when the selected pair
  * receives a new quote.
  */
-export function useSatoshisConversion(targetCurrency: string = 'USD') {
+export function useSatoshisConversion(targetCurrency?: string) {
   const { appService } = useAppContext();
-  const currencyCode = useMemo(() => targetCurrency.toUpperCase(), [targetCurrency]);
+  const subscribeToCurrency = useCallback(
+    (callback: () => void) => {
+      if (!appService || targetCurrency) {
+        return () => {};
+      }
+
+      return appService.settings.on('settings-updated', (event) => {
+        if (event.key === 'currency') {
+          callback();
+        }
+      });
+    },
+    [appService, targetCurrency],
+  );
+
+  const getCurrencySnapshot = useCallback(() => {
+    if (targetCurrency) {
+      return targetCurrency.toUpperCase();
+    }
+
+    if (!appService) {
+      return 'USD';
+    }
+
+    return appService.settings.getCurrency();
+  }, [appService, targetCurrency]);
+
+  const currencyCode = useSyncExternalStore(
+    subscribeToCurrency,
+    getCurrencySnapshot,
+    getCurrencySnapshot,
+  );
   const fiatPerBchRate = useBchToFiatRate(currencyCode);
 
   const formattedFiatPerBchRate = useMemo(() => {
diff --git a/src/tui/screens/WalletState.tsx b/src/tui/screens/WalletState.tsx
index f0662a0..d65a98c 100644
--- a/src/tui/screens/WalletState.tsx
+++ b/src/tui/screens/WalletState.tsx
@@ -11,6 +11,7 @@ import React, { useState, useEffect, useCallback, useMemo } from 'react';
 import { Box, Text } from 'ink';
 import { ScrollableList, type ListItemData } from '../components/List.js';
 import { QRCode } from '../components/QRCode.js';
+import { CurrencySelectionDialog } from '../components/CurrencySelectionDialog.js';
 import { useNavigation } from '../hooks/useNavigation.js';
 import { useAppContext, useStatus } from '../hooks/useAppContext.js';
 import { useSatoshisConversion } from '../hooks/useSatoshisConversion.js';
@@ -60,6 +61,7 @@ const menuItems: ListItemData<string>[] = [
   { key: 'import', label: 'Import Invitation', value: 'import' },
   { key: 'invitations', label: 'View Invitations', value: 'invitations' },
   { key: 'new-address', label: 'Generate New Address', value: 'new-address' },
+  { key: 'set-currency', label: 'Set Fiat Currency', value: 'set-currency' },
   { key: 'unreserve-all', label: 'Unreserve All Resources', value: 'unreserve-all' },
   { key: 'refresh', label: 'Refresh', value: 'refresh' },
 ];
@@ -121,7 +123,7 @@ export function WalletStateScreen(): React.ReactElement {
     fiatPerBchRate,
     formattedFiatPerBchRate,
     formatSatoshisToFiat,
-  } = useSatoshisConversion('USD');
+  } = useSatoshisConversion();
 
   // State
   const [balance, setBalance] = useState<{ totalSatoshis: bigint; utxoCount: number } | null>(null);
@@ -133,6 +135,14 @@ export function WalletStateScreen(): React.ReactElement {
 
   /** Cash address to display in the QR code dialog (null when dialog is hidden). */
   const [qrAddress, setQrAddress] = useState<string | null>(null);
+  /** Whether the fiat currency selection dialog is open. */
+  const [isCurrencyDialogOpen, setCurrencyDialogOpen] = useState(false);
+  /** Loading state for rates pair discovery. */
+  const [isLoadingCurrencyPairs, setLoadingCurrencyPairs] = useState(false);
+  /** Optional error message shown in the currency dialog. */
+  const [currencyPairsError, setCurrencyPairsError] = useState<string | null>(null);
+  /** Available fiat currencies derived from rates pairs in X/BCH format. */
+  const [availableCurrencies, setAvailableCurrencies] = useState<string[]>([]);
 
   /**
    * Refreshes wallet state.
@@ -260,6 +270,89 @@ export function WalletStateScreen(): React.ReactElement {
     }
   }, [appService, setStatus, showError, showInfo, refresh]);
 
+  /**
+   * Loads all available rates pairs, then extracts fiat numerator symbols from
+   * pairs shaped like X/BCH.
+   *
+   * We retry briefly because rates startup is asynchronous and metadata can take
+   * a moment to hydrate right after wallet initialization.
+   */
+  const loadAvailableCurrencies = useCallback(async (): Promise<void> => {
+    if (!appService) {
+      setCurrencyPairsError("AppService not initialized");
+      return;
+    }
+
+    setLoadingCurrencyPairs(true);
+    setCurrencyPairsError(null);
+
+    try {
+      let pairs = new Set<string>();
+
+      // Retry a few times so we can catch late metadata initialization.
+      for (let attempt = 0; attempt < 4; attempt += 1) {
+        pairs = await appService.rates.listPairs();
+        if (pairs.size > 0) {
+          break;
+        }
+        await new Promise((resolve) => setTimeout(resolve, 200));
+      }
+
+      const currencies = Array.from(pairs)
+        .map((pair) => pair.toUpperCase())
+        .filter((pair) => pair.endsWith("/BCH"))
+        .map((pair) => pair.split("/")[0] ?? "")
+        .filter((currency) => currency.length > 0)
+        .sort((a, b) => a.localeCompare(b));
+
+      const uniqueCurrencies = Array.from(new Set(currencies));
+      setAvailableCurrencies(uniqueCurrencies);
+
+      if (uniqueCurrencies.length === 0) {
+        setCurrencyPairsError(
+          "No X/BCH rates are currently available. Try again in a moment.",
+        );
+      }
+    } catch (error) {
+      setCurrencyPairsError(
+        `Failed to load currency pairs: ${error instanceof Error ? error.message : String(error)}`,
+      );
+    } finally {
+      setLoadingCurrencyPairs(false);
+    }
+  }, [appService]);
+
+  /**
+   * Opens the fiat currency dialog and triggers pair discovery.
+   */
+  const openCurrencyDialog = useCallback(() => {
+    setCurrencyDialogOpen(true);
+    void loadAvailableCurrencies();
+  }, [loadAvailableCurrencies]);
+
+  /**
+   * Applies the selected fiat currency to persisted settings.
+   */
+  const applyCurrencySelection = useCallback(
+    (currencyCode: string) => {
+      if (!appService) {
+        showError("AppService not initialized");
+        return;
+      }
+
+      try {
+        appService.settings.setCurrency(currencyCode);
+        setStatus(`Fiat currency updated to ${currencyCode}`);
+        setCurrencyDialogOpen(false);
+      } catch (error) {
+        showError(
+          `Failed to update currency: ${error instanceof Error ? error.message : String(error)}`,
+        );
+      }
+    },
+    [appService, setStatus, showError],
+  );
+
   /**
    * Handles menu action.
    */
@@ -277,6 +370,9 @@ export function WalletStateScreen(): React.ReactElement {
       case 'new-address':
         generateNewAddress();
         break;
+      case 'set-currency':
+        openCurrencyDialog();
+        break;
       case 'unreserve-all':
         unreserveAll();
         break;
@@ -284,7 +380,7 @@ export function WalletStateScreen(): React.ReactElement {
         refresh();
         break;
     }
-  }, [navigate, generateNewAddress, unreserveAll, refresh]);
+  }, [navigate, generateNewAddress, openCurrencyDialog, unreserveAll, refresh]);
 
   /**
    * Handle menu item activation.
@@ -543,6 +639,27 @@ export function WalletStateScreen(): React.ReactElement {
           onClose={() => setQrAddress(null)}
         />
       )}
+
+      {/* Fiat currency selection dialog overlay */}
+      {isCurrencyDialogOpen && (
+        <Box
+          position="absolute"
+          flexDirection="column"
+          alignItems="center"
+          justifyContent="center"
+          width="100%"
+          height="100%"
+        >
+          <CurrencySelectionDialog
+            currentCurrency={currencyCode}
+            currencies={availableCurrencies}
+            isLoading={isLoadingCurrencyPairs}
+            errorMessage={currencyPairsError}
+            onSelectCurrency={applyCurrencySelection}
+            onCancel={() => setCurrencyDialogOpen(false)}
+          />
+        </Box>
+      )}
     </Box>
   );
 }
diff --git a/src/tui/screens/action-wizard/steps/InputsStep.tsx b/src/tui/screens/action-wizard/steps/InputsStep.tsx
index 9402dd1..9d45c95 100644
--- a/src/tui/screens/action-wizard/steps/InputsStep.tsx
+++ b/src/tui/screens/action-wizard/steps/InputsStep.tsx
@@ -23,7 +23,7 @@ export function InputsStep({
   changeAmount,
   focusArea,
 }: Props): React.ReactElement {
-  const { formatSatoshisToFiat } = useSatoshisConversion('USD');
+  const { formatSatoshisToFiat } = useSatoshisConversion();
 
   const getFiatSuffix = (satoshis: bigint): string => {
     const fiatValue = formatSatoshisToFiat(satoshis);
diff --git a/src/tui/screens/action-wizard/steps/ReviewStep.tsx b/src/tui/screens/action-wizard/steps/ReviewStep.tsx
index 57429c4..28d62da 100644
--- a/src/tui/screens/action-wizard/steps/ReviewStep.tsx
+++ b/src/tui/screens/action-wizard/steps/ReviewStep.tsx
@@ -23,7 +23,7 @@ export function ReviewStep({
   changeAmount,
 }: ReviewStepProps): React.ReactElement {
   const selectedUtxos = availableUtxos.filter((u) => u.selected);
-  const { formatSatoshisToFiat } = useSatoshisConversion('USD');
+  const { formatSatoshisToFiat } = useSatoshisConversion();
 
   const getFiatSuffix = (satoshis: bigint): string => {
     const fiatValue = formatSatoshisToFiat(satoshis);
diff --git a/src/tui/screens/invitations/InvitationScreen.tsx b/src/tui/screens/invitations/InvitationScreen.tsx
index 2dcc50f..825efa6 100644
--- a/src/tui/screens/invitations/InvitationScreen.tsx
+++ b/src/tui/screens/invitations/InvitationScreen.tsx
@@ -113,7 +113,7 @@ export function InvitationScreen(): React.ReactElement {
 
   const invitations = useInvitations();
   const { currencyCode, formattedFiatPerBchRate, formatSatoshisToFiat } =
-    useSatoshisConversion('USD');
+    useSatoshisConversion();
 
   // ── UI state ─────────────────────────────────────────────────────────────
   const [selectedIndex, setSelectedIndex] = useState(0);
diff --git a/src/tui/screens/invitations/invitation-import/steps/InputsSelectStep.tsx b/src/tui/screens/invitations/invitation-import/steps/InputsSelectStep.tsx
index d1a8850..0f70a7d 100644
--- a/src/tui/screens/invitations/invitation-import/steps/InputsSelectStep.tsx
+++ b/src/tui/screens/invitations/invitation-import/steps/InputsSelectStep.tsx
@@ -33,7 +33,7 @@ export function InputsSelectStep({
   const [requiredAmount, setRequiredAmount] = useState(0n);
   const [isLoading, setIsLoading] = useState(true);
   const [error, setError] = useState<string | null>(null);
-  const { formatSatoshisToFiat } = useSatoshisConversion('USD');
+  const { formatSatoshisToFiat } = useSatoshisConversion();
 
   const fee = DEFAULT_FEE;
 
diff --git a/src/tui/screens/invitations/invitation-import/steps/PreviewInvitationStep.tsx b/src/tui/screens/invitations/invitation-import/steps/PreviewInvitationStep.tsx
index 5f9e717..2740a07 100644
--- a/src/tui/screens/invitations/invitation-import/steps/PreviewInvitationStep.tsx
+++ b/src/tui/screens/invitations/invitation-import/steps/PreviewInvitationStep.tsx
@@ -42,7 +42,7 @@ export function PreviewInvitationStep({
   onCancel,
   isActive,
 }: PreviewStepProps): React.ReactElement {
-  const { formatSatoshisToFiat } = useSatoshisConversion('USD');
+  const { formatSatoshisToFiat } = useSatoshisConversion();
 
   useLayeredInput('import-flow', (_input, key) => {
     if (key.return) onComplete();
diff --git a/src/tui/screens/invitations/invitation-import/steps/ReviewStep.tsx b/src/tui/screens/invitations/invitation-import/steps/ReviewStep.tsx
index 4acb79a..cf3b290 100644
--- a/src/tui/screens/invitations/invitation-import/steps/ReviewStep.tsx
+++ b/src/tui/screens/invitations/invitation-import/steps/ReviewStep.tsx
@@ -33,7 +33,7 @@ export function ReviewStep({
 }: ReviewStepProps): React.ReactElement {
   const [isSubmitting, setIsSubmitting] = useState(false);
   const [error, setError] = useState<string | null>(null);
-  const { formatSatoshisToFiat } = useSatoshisConversion('USD');
+  const { formatSatoshisToFiat } = useSatoshisConversion();
 
   const fee = DEFAULT_FEE;
   const action = template?.actions?.[invitation.data.actionIdentifier];
diff --git a/src/utils/paths.ts b/src/utils/paths.ts
index fbc9450..b5d25b4 100644
--- a/src/utils/paths.ts
+++ b/src/utils/paths.ts
@@ -35,10 +35,17 @@ export function getDataDir(): string {
 }
 
 /**
- * File storing the last-used mnemonic reference for `-m` omission.
+ * File storing CLI settings (JSON), including the last-used mnemonic reference.
+ */
+export function getSettingsPath(): string {
+  return join(getConfigDir(), ".wallet");
+}
+
+/**
+ * @deprecated Prefer {@link getSettingsPath}.
  */
 export function getWalletConfigPath(): string {
-  return join(getConfigDir(), ".wallet");
+  return getSettingsPath();
 }
 
 /**
diff --git a/src/utils/rates/base-rates.ts b/src/utils/rates/base-rates.ts
index beb5707..739278b 100644
--- a/src/utils/rates/base-rates.ts
+++ b/src/utils/rates/base-rates.ts
@@ -38,19 +38,34 @@ export abstract class BaseRates<
    * @returns The formatted amount.
    */
   public formatCurrency(amount: number, targetCurrency: string): string {
+    const normalizedCurrency = targetCurrency.toUpperCase();
     const minimumFractionDigitsMap: { [currency: string]: number } = {
       AUD: 2,
       BCH: 8,
       USD: 2,
     };
+    const minimumFractionDigits = minimumFractionDigitsMap[normalizedCurrency] ?? 2;
+    const maximumFractionDigits = Math.max(minimumFractionDigits, 8);
 
-    const formatter = new Intl.NumberFormat('en-US', {
-      style: 'currency',
-      currency: targetCurrency,
-      currencyDisplay: 'narrowSymbol',
-      minimumFractionDigits: minimumFractionDigitsMap[targetCurrency] || 0,
-    });
+    try {
+      const formatter = new Intl.NumberFormat('en-US', {
+        style: 'currency',
+        currency: normalizedCurrency,
+        currencyDisplay: 'narrowSymbol',
+        minimumFractionDigits,
+        maximumFractionDigits,
+      });
 
-    return formatter.format(amount);
+      return formatter.format(amount);
+    } catch {
+      // Some numerator symbols from oracle pairs (e.g. DOGE/BCH) are not ISO-4217
+      // fiat currency codes, so Intl currency formatting will throw a RangeError.
+      // In that case we still return a human-readable formatted value.
+      const numericFormatter = new Intl.NumberFormat('en-US', {
+        minimumFractionDigits,
+        maximumFractionDigits,
+      });
+      return `${numericFormatter.format(amount)} ${normalizedCurrency}`;
+    }
   }
 }
diff --git a/src/utils/rates/rates-oracles.ts b/src/utils/rates/rates-oracles.ts
index 43efce1..dc82dda 100644
--- a/src/utils/rates/rates-oracles.ts
+++ b/src/utils/rates/rates-oracles.ts
@@ -6,6 +6,8 @@ import {
 } from '@generalprotocols/oracle-client';
 
 import { type RatesEventMap, BaseRates } from './base-rates.js';
+import { type OffCallback } from '../event-emitter.js';
+import { SettingsService } from '../../services/settings.js';
 
 // Add the Oracle Price Message to our Events for this Adapter.
 export type RatesOracleEventMap = RatesEventMap & {
@@ -22,22 +24,34 @@ export class RatesOracle extends BaseRates<RatesOracleEventMap> {
    * @param client The underlying oracle client. If not provided, a new client will be created.
    * @returns The rates oracle.
    */
-  static async from(client?: OracleClient) {
-    const ratesOracle = new RatesOracle(client ?? (await OracleClient.from()));
+  static async from(
+    client?: OracleClient,
+    settings: SettingsService = new SettingsService(),
+  ) {
+    const ratesOracle = new RatesOracle(
+      client ?? (await OracleClient.from()),
+      settings,
+    );
 
     return ratesOracle;
   }
 
   private client: OracleClient;
+  private settings: SettingsService;
   private oracles: OracleMetadataMap;
 
   private started: boolean = false;
+  private targetNumeratorUnitCode: string;
+  private targetDenominatorUnitCode: string = 'BCH';
+  private unsubscribeFromSettings: OffCallback | null = null;
 
-  private constructor(client: OracleClient) {
+  private constructor(client: OracleClient, settings: SettingsService) {
     super();
 
     this.client = client;
+    this.settings = settings;
     this.oracles = {};
+    this.targetNumeratorUnitCode = settings.getCurrency().toUpperCase();
   }
 
   /**
@@ -48,6 +62,10 @@ export class RatesOracle extends BaseRates<RatesOracleEventMap> {
       return;
     }
     this.started = true;
+    this.unsubscribeFromSettings = this.settings.on(
+      'settings-updated',
+      this.handleSettingsUpdated.bind(this),
+    );
 
     // Create event listeners for the client.
     this.client.setOnMetadataMessage(this.handleMetadataMessage.bind(this));
@@ -71,6 +89,8 @@ export class RatesOracle extends BaseRates<RatesOracleEventMap> {
       return;
     }
     this.started = false;
+    this.unsubscribeFromSettings?.();
+    this.unsubscribeFromSettings = null;
 
     // Remove event listeners by setting them to empty functions.
     this.client.setOnMetadataMessage(() => {});
@@ -85,6 +105,12 @@ export class RatesOracle extends BaseRates<RatesOracleEventMap> {
    * @returns A set of pairs.
    */
   async listPairs() {
+    // If metadata has not arrived yet but the client is running, query once so
+    // callers (like the currency picker) can still discover available pairs.
+    if (Object.keys(this.oracles).length === 0 && this.started) {
+      this.oracles = await this.client.getMetadataMap();
+    }
+
     return new Set(
       Object.values(this.oracles).map((oracle) => {
         return `${oracle.SOURCE_NUMERATOR_UNIT_CODE}/${oracle.SOURCE_DENOMINATOR_UNIT_CODE}`;
@@ -157,14 +183,48 @@ export class RatesOracle extends BaseRates<RatesOracleEventMap> {
       return;
     }
 
+    const sourceNumeratorUnitCode = oracle.SOURCE_NUMERATOR_UNIT_CODE.toUpperCase();
+    const sourceDenominatorUnitCode = oracle.SOURCE_DENOMINATOR_UNIT_CODE.toUpperCase();
+
+    // Only emit the pair currently selected in settings.
+    if (
+      sourceNumeratorUnitCode !== this.targetNumeratorUnitCode ||
+      sourceDenominatorUnitCode !== this.targetDenominatorUnitCode
+    ) {
+      return;
+    }
+
     // Scale the price
     const priceValue = message.priceValue / oracle.ATTESTATION_SCALING;
 
     this.emit('rateUpdated', {
-      numeratorUnitCode: oracle.SOURCE_NUMERATOR_UNIT_CODE,
-      denominatorUnitCode: oracle.SOURCE_DENOMINATOR_UNIT_CODE,
+      numeratorUnitCode: sourceNumeratorUnitCode,
+      denominatorUnitCode: sourceDenominatorUnitCode,
       price: priceValue,
       oraclePriceMessage: message,
     });
   }
+
+  /**
+   * Tracks updates to settings and switches the actively emitted fiat pair.
+   */
+  private handleSettingsUpdated(
+    event: {
+      key: 'currency' | 'default-mnemonic';
+      value: string | undefined;
+    },
+  ) {
+    if (event.key !== 'currency' || !event.value) {
+      return;
+    }
+
+    this.targetNumeratorUnitCode = event.value.toUpperCase();
+
+    // Refresh so listeners get the latest value for the new currency quickly.
+    if (this.started) {
+      this.refreshPrices().catch((error) => {
+        console.error('Error refreshing prices after currency update:', error);
+      });
+    }
+  }
 }
diff --git a/tests/cli/commands/settings.test.ts b/tests/cli/commands/settings.test.ts
new file mode 100644
index 0000000..60a5925
--- /dev/null
+++ b/tests/cli/commands/settings.test.ts
@@ -0,0 +1,83 @@
+/// <reference types="node" />
+
+import { afterEach, beforeEach, describe, expect, test } from "vitest";
+import { mkdtempSync, readFileSync, rmSync } from "node:fs";
+import { tmpdir } from "node:os";
+import path from "node:path";
+
+import { handleSettingsCommand } from "../../../src/cli/commands/settings";
+import { CommandError } from "../../../src/cli/commands/types";
+import { createMockIO, createMockPaths } from "../mocks/command";
+
+describe("settings command", () => {
+  let tempDir: string;
+
+  beforeEach(() => {
+    tempDir = mkdtempSync(path.join(tmpdir(), "xo-cli-settings-command-test-"));
+  });
+
+  afterEach(() => {
+    rmSync(tempDir, { recursive: true, force: true });
+  });
+
+  test("shows default settings when .wallet does not exist", async () => {
+    const { io, capture } = createMockIO();
+    const paths = createMockPaths(tempDir);
+
+    const result = await handleSettingsCommand({ io, paths }, ["show"], {});
+
+    expect(result).toEqual({ currency: "USD" });
+    expect(capture.out.join("\n")).toContain("currency");
+    expect(capture.out.join("\n")).toContain("USD");
+  });
+
+  test("sets and gets currency", async () => {
+    const { io, capture } = createMockIO();
+    const paths = createMockPaths(tempDir);
+
+    await handleSettingsCommand({ io, paths }, ["set", "currency", "aud"], {});
+    const getResult = await handleSettingsCommand(
+      { io, paths },
+      ["get", "currency"],
+      {},
+    );
+
+    expect(getResult).toEqual({ key: "currency", value: "AUD" });
+    expect(capture.out).toContain("Updated currency: AUD");
+    expect(capture.out).toContain("AUD");
+  });
+
+  test("sets default-mnemonic and persists JSON .wallet", async () => {
+    const { io } = createMockIO();
+    const paths = createMockPaths(tempDir);
+
+    await handleSettingsCommand(
+      { io, paths },
+      ["set", "default-mnemonic", "mnemonic-primary"],
+      {},
+    );
+
+    const persisted = JSON.parse(readFileSync(paths.walletConfigPath, "utf8")) as {
+      currency: string;
+      "default-mnemonic"?: string;
+    };
+
+    expect(persisted).toEqual({
+      currency: "USD",
+      "default-mnemonic": "mnemonic-primary",
+    });
+  });
+
+  test("throws command error for unknown subcommand", async () => {
+    const { io } = createMockIO();
+    const paths = createMockPaths(tempDir);
+
+    try {
+      await handleSettingsCommand({ io, paths }, ["unknown"], {});
+      expect.fail("Expected settings command to throw");
+    } catch (error) {
+      expect(error).toBeInstanceOf(CommandError);
+      expect((error as CommandError).event).toBe("settings.subcommand.unknown");
+    }
+  });
+});
diff --git a/tests/cli/rates-format.test.ts b/tests/cli/rates-format.test.ts
new file mode 100644
index 0000000..2fa7145
--- /dev/null
+++ b/tests/cli/rates-format.test.ts
@@ -0,0 +1,40 @@
+/// <reference types="node" />
+
+import { describe, expect, test } from "vitest";
+
+import { BaseRates } from "../../src/utils/rates/base-rates";
+
+/**
+ * Minimal concrete adapter used only for testing BaseRates helpers.
+ */
+class TestRatesAdapter extends BaseRates {
+  public async start(): Promise<void> {
+    return;
+  }
+
+  public async stop(): Promise<void> {
+    return;
+  }
+
+  public async listPairs(): Promise<Set<string>> {
+    return new Set(["USD/BCH", "DOGE/BCH"]);
+  }
+}
+
+describe("BaseRates.formatCurrency", () => {
+  test("formats ISO currency codes with Intl currency style", () => {
+    const rates = new TestRatesAdapter();
+    const formatted = rates.formatCurrency(12.5, "USD");
+
+    expect(formatted).toContain("$");
+    expect(formatted).toContain("12.50");
+  });
+
+  test("formats non-ISO symbols without throwing", () => {
+    const rates = new TestRatesAdapter();
+    const formatted = rates.formatCurrency(12.3456789, "DOGE");
+
+    expect(formatted).toContain("DOGE");
+    expect(formatted).toContain("12.3456789");
+  });
+});
diff --git a/tests/cli/settings.test.ts b/tests/cli/settings.test.ts
new file mode 100644
index 0000000..d727a35
--- /dev/null
+++ b/tests/cli/settings.test.ts
@@ -0,0 +1,96 @@
+/// <reference types="node" />
+
+import { beforeEach, afterEach, describe, expect, test } from "vitest";
+import {
+  existsSync,
+  mkdtempSync,
+  readFileSync,
+  rmSync,
+  writeFileSync,
+} from "node:fs";
+import { join } from "node:path";
+import { tmpdir } from "node:os";
+
+import { SettingsService } from "../../src/services/settings";
+
+/**
+ * Tests for SettingsService persistence and migration behavior.
+ */
+describe("SettingsService", () => {
+  let testDir: string;
+  let settingsPath: string;
+
+  beforeEach(() => {
+    testDir = mkdtempSync(join(tmpdir(), "xo-cli-settings-test-"));
+    settingsPath = join(testDir, ".wallet");
+  });
+
+  afterEach(() => {
+    rmSync(testDir, { recursive: true, force: true });
+  });
+
+  test("returns defaults when settings file does not exist", () => {
+    const settings = new SettingsService(settingsPath);
+
+    expect(settings.getDefaultMnemonic()).toBeUndefined();
+    expect(settings.getCurrency()).toBe("USD");
+    expect(settings.getSettings()).toEqual({ currency: "USD" });
+    expect(existsSync(settingsPath)).toBe(false);
+  });
+
+  test("migrates legacy .wallet plaintext mnemonic to JSON", () => {
+    writeFileSync(settingsPath, "mnemonic-legacy", "utf8");
+
+    const settings = new SettingsService(settingsPath);
+
+    expect(settings.getDefaultMnemonic()).toBe("mnemonic-legacy");
+    expect(settings.getCurrency()).toBe("USD");
+
+    const persisted = JSON.parse(readFileSync(settingsPath, "utf8")) as {
+      "default-mnemonic"?: string;
+      currency: string;
+    };
+    expect(persisted).toEqual({
+      "default-mnemonic": "mnemonic-legacy",
+      currency: "USD",
+    });
+  });
+
+  test("normalizes and persists currency and default-mnemonic", () => {
+    const settings = new SettingsService(settingsPath);
+
+    settings.setDefaultMnemonic("  mnemonic-primary  ");
+    settings.setCurrency("aud");
+
+    expect(settings.getSettings()).toEqual({
+      "default-mnemonic": "mnemonic-primary",
+      currency: "AUD",
+    });
+
+    const persisted = JSON.parse(readFileSync(settingsPath, "utf8")) as {
+      "default-mnemonic"?: string;
+      currency: string;
+    };
+    expect(persisted).toEqual({
+      "default-mnemonic": "mnemonic-primary",
+      currency: "AUD",
+    });
+  });
+
+  test("emits settings-updated events on setting changes", () => {
+    const settings = new SettingsService(settingsPath);
+    const events: Array<{ key: string; value: string | undefined }> = [];
+
+    settings.on("settings-updated", (event) => {
+      events.push({ key: event.key, value: event.value });
+    });
+
+    settings.setCurrency("cad");
+    settings.setDefaultMnemonic("mnemonic-blue");
+
+    expect(events).toEqual([
+      { key: "currency", value: "CAD" },
+      { key: "default-mnemonic", value: "mnemonic-blue" },
+    ]);
+  });
+});