feat: remove an address from an HD wallet, behind a confirmation (closes #162)

Address rows on Home now carry an [x] control on wallets that derive their
addresses from an extended key and hold more than one; it opens a confirmation
screen before anything is removed.

Removing an address destroys nothing: it stays derivable from key material the
wallet still holds, and any funds at it stay where they are. That is also why
the screen is not password-gated, unlike delete-wallet — a password gates the
disclosure or destruction of a secret, and this does neither.

Getting the address back into the list is another matter, and the copy states
it exactly rather than promising a route the app refuses. "+" derives the next
unused index, because the derivation counter is a high-water mark and is not
rewound, and re-importing the wallet's key material is rejected as a duplicate
for as long as the wallet is present — which it always is here, since a wallet
never gives up its last address. What works is deleting the whole wallet in
Settings, which asks for the password and destroys the stored secret, then
importing again: the scan that follows rediscovers the address only if it has
on-chain activity, and an address that was never used does not come back at
all. The text is built by recoveryPathText() rather than sitting in index.html
so it can name the wallet's own kind of key material, an xprv wallet having no
recovery phrase to re-import.

A balance is surfaced as a warning, never a refusal, and holding something
means any ERC-20 as well as ETH, at any size: an address with no ETH and a
stablecoin position must not get a blank line on the screen whose job is to
warn. The warning names no figure of its own, because the balance lines round
to four decimals and a sentence built from a rounded number would report
0.0000 ETH for an address holding real money; the amounts come from the same
balanceLinesForAddress() and getAddressValueUsd() every other screen uses.

The state transition lives next to the wallet one in
src/shared/walletDelete.js and shares its address comparison, site-permission
cleanup and broadcast, so the rules match one level down: the last address of
a wallet is never removable, the selection moves only when it was the address
removed, an index after the splice is decremented, a selection in another
wallet is untouched, and AUTISTMASK_ACTIVE_CHANGED is broadcast when the
active address moves so a connected site stops being told about an address the
user removed.

README.md

@@ -123,18 +123,20 @@ unavailable). The suite lives in `tests/e2e/` and is driven by
 `playwright-core`, whose version must stay matched to the container's Playwright
 version — the browsers ship inside the image.
 
-It covers popup load, wallet creation through the UI, the Add Token screen, the
+It covers popup load, WebAssembly compilation under the shipped CSP (see
-transaction detail screen for an ERC-20 transfer, and the recovery phrase screen
+[Content Security Policy](#content-security-policy)), wallet creation through
-— which wallet types are offered it, that it holds nothing before the password
+the UI, the Add Token screen, the transaction detail screen for an ERC-20
-is accepted, that a wrong password reveals nothing, that leaving it by either
+transfer, and the recovery phrase screen — which wallet types are offered it,
-route wipes it — including a leave taken while the decrypt is still running —
+that it holds nothing before the password is accepted, that a wrong password
-and that reopening the popup does not land on it. It also covers address
+reveals nothing, that leaving it by either route wipes it — including a leave
-removal: which wallets offer the control at all, that leaving the confirmation
+taken while the decrypt is still running — and that reopening the popup does not
-removes nothing, and that confirming it does. All outbound network is
+land on it. It also covers address removal: which wallets offer the control at
-intercepted at the browser level and served from fixtures in
+all, that the confirmation states the route back rather than showing an empty
-`tests/e2e/network.js`, so the run is deterministic and fully offline;
+paragraph, that leaving the confirmation removes nothing, and that confirming it
-unrecognised outbound requests are reported as failures rather than silently
+does. All outbound network is intercepted at the browser level and served from
-allowed.
+fixtures in `tests/e2e/network.js`, so the run is deterministic and fully
+offline; unrecognised outbound requests are reported as failures rather than
+silently allowed.
 
 That reporting has one bound worth knowing. Observation ends when the browser
 context is torn down, and nothing can watch traffic after that, so the run keeps
@@ -445,9 +447,9 @@ The core hierarchy is **Wallets → Addresses**:
 Which tokens an address shows is decided by `fetchTokenBalances()` in
 `src/shared/balances.js`, from the Blockscout `token-balances` response, so
 tokens do appear without the user adding them. An ERC-20 is shown when its
-balance is nonzero and it is in the bundled top-250 token list, is tracked by
+balance is nonzero and it is in the bundled known-token list, is tracked by the
-the user, or has 1,000 or more holders; a token claiming a symbol from the
+user, or has 1,000 or more holders; a token claiming a symbol from the bundled
-bundled list from any other contract address is always dropped. That filter is
+list from any other contract address is always dropped. That filter is
 unconditional — the "Hide tokens with fewer than 1,000 holders" setting governs
 the transaction history and the send-screen token selector, not this list.
 Tracked tokens with a zero balance are listed as well while "Show tracked tokens
@@ -656,16 +658,26 @@ of it.
     - To: blockie + color dot + full address + etherscan link + ENS name
     - Amount: value + symbol (USD in parentheses)
     - Your balance: value + symbol (USD in parentheses)
-    - Estimated network fee: "Estimating..." then the ETH amount (USD in
+    - Network fee: "Estimating..." then two lines, or "Unable to estimate",
-      parentheses) or "Unable to estimate", fetched async
+      fetched async. The first line is what the transfer is expected to cost,
+      `gasLimit * gasPrice` (USD in parentheses); the second is the
+      `gasLimit * maxFeePerGas` reserve the node requires, which is what the
+      balance check gates on. The second line is omitted on a network with no
+      type-2 pricing, where the two are the same number, but its space is
+      reserved either way
     - Warnings: inline warnings from the local checks (scam address, self-send)
       plus four reserved warning boxes made visible by the async checks —
       recipient with no transaction history, recipient is a contract, burn
       address, and an Etherscan phishing/scam label
-    - Errors (insufficient balance)
+    - Errors (insufficient balance), plus three reserved error boxes — the
+      amount plus the fee exceeds the balance (ETH transfers), not enough ETH to
+      pay the fee for the transfer (ERC-20 transfers), and the fee could not be
+      estimated. The first two are mutually exclusive per transfer type, so only
+      the applicable one holds space
     - Password: an inline field on this screen, not a modal, with its own error
       line
-    - "Sign & Send" button (disabled if errors)
+    - "Sign & Send" button (disabled if errors, and while the network fee
+      estimate is pending or unavailable)
 - **Transitions**:
     - "Sign & Send" (correct password) → broadcast tx → **WaitTx**
     - "Sign & Send" (correct password) → broadcast fails → **ErrorTx**
@@ -884,10 +896,25 @@ of it.
     - The full address (color dot, etherscan link, tap to copy), with the ENS
       name above it if resolved
     - Explanation that this only stops the wallet tracking the address: nothing
-      is destroyed, no key is deleted, funds stay where they are, and the
+      is destroyed, no key is deleted, and funds stay where they are
-      address comes back by importing the recovery phrase again
+    - The route back, stated with its limit, because the obvious two are both
-    - A line naming the address's ETH balance when it holds one, stating that
+      refused: "+" derives the next unused index (`nextIndex` is a high-water
-      removal moves and spends nothing. A balance is a warning, never a refusal.
+      mark), and re-importing the wallet's key material is rejected as a
+      duplicate by `findWalletByXpub` while the wallet is still present. What
+      works is deleting the whole wallet in Settings — password-gated, and it
+      destroys the stored secret — then importing again, whereupon
+      `scanForAddresses()` rediscovers the address **only if it has on-chain
+      activity**. An address that was never used does not come back. The text is
+      written by `recoveryPathText()` rather than sitting in `index.html`, so it
+      can name the wallet's own kind of key material: an xprv wallet has no
+      recovery phrase to re-import.
+    - A warning when the address holds anything, ETH or any tracked ERC-20,
+      followed by the holdings themselves via `balanceLinesForAddress()` and the
+      USD total via `getAddressValueUsd()`. The sentence names no figure of its
+      own: the lines round to four decimals, so a sentence built from a rounded
+      number would report `0.0000 ETH` for an address holding real money. The
+      predicate is `addressHoldsFunds()` in `src/popup/views/helpers.js`,
+      unrounded and token-aware. A balance is a warning, never a refusal.
     - The rule that a wallet always keeps at least one address, and that
       removing the last one means deleting the wallet from Settings
     - Error line
@@ -1036,7 +1063,7 @@ communicates with three external services to function as a wallet:
 What the extension does NOT do:
 
 - No analytics or telemetry services
-- No token list APIs (the top-250 token list is bundled at build time)
+- No token list APIs (the known-token list is bundled at build time)
 - No Infura/Alchemy dependency (any JSON-RPC endpoint works)
 - No backend servers operated by the developer
 
@@ -1096,6 +1123,36 @@ battle-tested.
 Exceptions require explicit authorization in a code comment referencing this
 policy, but as of now there are none.
 
+### Content Security Policy
+
+Both manifests declare the same policy for extension pages —
+`script-src 'self' 'wasm-unsafe-eval'; object-src 'self'` — as an object under
+`content_security_policy.extension_pages` in `manifest/chrome.json` (MV3) and as
+a bare string in `manifest/firefox.json` (MV2).
+
+`'wasm-unsafe-eval'` is there for one reason: libsodium. It ships a WebAssembly
+build and a `wasm2js` translation of it in one file, tries WASM first, and
+silently falls back to the translation if instantiation throws. Under a plain
+`script-src 'self'` the fallback was taken on every popup load, announced by
+nothing but an uncaught `CompileError`. Measured on the same Argon2id parameters
+the vault uses (`OPSLIMIT_INTERACTIVE`, `MEMLIMIT_INTERACTIVE`), WASM derives a
+key in 141-198ms and `wasm2js` in 3204-3660ms. The work factor is identical — it
+is set by the ops and memory parameters, not by wall time — so the fallback
+bought nothing and cost about three and a half seconds on every operation that
+asks for the password, which is every signature.
+
+The keyword permits compiling WebAssembly and nothing else: not `eval()` of
+strings, not inline script, not remote script. Using it requires already
+executing script in an extension page, which is complete compromise on its own.
+`'unsafe-eval'` is a different proposition and is not granted.
+
+The grant is pinned in both directions. `tests/manifest.test.js` asserts the
+exact token set in both manifests, so dropping `'wasm-unsafe-eval'` (a silent
+20x regression on the key derivation) and adding anything beyond it both fail
+`make check`. `tests/vaultBackend.test.js` asserts the unit tests run the WASM
+backend, and `make test-e2e` compiles a WebAssembly module inside the real popup
+under the real manifest.
+
 ### DEBUG Mode Policy
 
 The `DEBUG` constant in the popup JS enables a red "DEBUG / INSECURE" banner and
@@ -1164,8 +1221,8 @@ hardcoded test phrase.
 - Add multiple addresses within an HD wallet
 - Manage multiple wallets simultaneously
 - View ETH balance per address
-- View ERC-20 token balances (bundled top-250 tokens, tokens with 1,000 or more
+- View ERC-20 token balances (tokens on the bundled known-token list, tokens
-  holders, and tokens the user adds by contract address)
+  with 1,000 or more holders, and tokens the user adds by contract address)
 - Send ETH to an address
 - Send ERC-20 tokens to an address
 - Receive ETH/tokens (display address, copy to clipboard, QR code)
@@ -1223,26 +1280,30 @@ indexes it as a real token transfer.
   address. Users should always verify the full address on the confirmation
   screen before signing or sending.
 
-- **Known token symbol verification**: AutistMask ships a hardcoded list of the
+- **Known token symbol verification**: AutistMask ships a hardcoded list of
-  top 250 ERC-20 tokens with their legitimate contract addresses and symbols.
+  high-market-cap ERC-20 tokens with their legitimate contract addresses and
-  Any token transfer claiming a symbol from this list (e.g. "ETH", "USDT",
+  symbols. The list is a point-in-time snapshot of the highest-market-cap
-  "USDC") but originating from an unrecognized contract address is identified as
+  Ethereum mainnet ERC-20s taken from the CoinGecko API, with decimals verified
-  a spoof and filtered from display. The fake "Ethereum" token in the attack
+  on-chain and addresses EIP-55 checksummed; `TOKENS` in
-  above used symbol "ETH" from contract
+  `src/shared/tokenList.js` is the authoritative set. It is bundled at build
-  `0xD05339f9Ea5ab9d9F03B9d57F671d2abD1F55c82`, which does not match the known
+  time and only changes when that file is regenerated. Any token transfer
-  WETH contract — so it would be caught by this check. Detecting a spoof is also
+  claiming a symbol from this list (e.g. "ETH", "USDT", "USDC") but originating
-  what adds a contract to the fraud contract blocklist below; that is the only
+  from an unrecognized contract address is identified as a spoof and filtered
-  thing that populates it. In the transaction history the check is the "Hide
+  from display. The fake "Ethereum" token in the attack above used symbol "ETH"
-  fake tokens impersonating a known symbol" setting, on by default; with it off,
+  from contract `0xD05339f9Ea5ab9d9F03B9d57F671d2abD1F55c82`, which does not
-  spoofed transfers are shown and no new blocklist entries are learned from
+  match the known WETH contract — so it would be caught by this check. Detecting
-  them. The send-screen token selector applies the same check unconditionally,
+  a spoof is also what adds a contract to the fraud contract blocklist below;
-  because it decides which tokens the user can act on rather than what the
+  that is the only thing that populates it. In the transaction history the check
-  history displays. The balance list applies it unconditionally too, but not
+  is the "Hide fake tokens impersonating a known symbol" setting, on by default;
-  identically: it exempts symbols that `KNOWN_SYMBOLS` maps to `null`, and
+  with it off, spoofed transfers are shown and no new blocklist entries are
-  `"ETH"` is the only one. So the fake "Ethereum" token above is filtered from
+  learned from them. The send-screen token selector applies the same check
-  the transaction history and from the send selector, but a fake-`ETH` ERC-20
+  unconditionally, because it decides which tokens the user can act on rather
-  that clears the balance list's own 1,000-holder floor — or that the user
+  than what the history displays. The balance list applies it unconditionally
-  tracked manually — is still shown in the balance list.
+  too, but not identically: it exempts symbols that `KNOWN_SYMBOLS` maps to
+  `null`, and `"ETH"` is the only one. So the fake "Ethereum" token above is
+  filtered from the transaction history and from the send selector, but a
+  fake-`ETH` ERC-20 that clears the balance list's own 1,000-holder floor — or
+  that the user tracked manually — is still shown in the balance list.
 
 - **Low-holder token filtering**: Token transfers from ERC-20 contracts with
   fewer than 1,000 holders are hidden from transaction history by default.

TODO.md

@@ -44,11 +44,27 @@ undefined identifiers, which is how
 
 # Completed Steps
 
-- 2026-08-11: An address can be removed from an HD or xprv wallet behind a
+- 2026-08-12: An address can be removed from an HD or xprv wallet behind a
   confirmation screen that states nothing is destroyed, sharing the deletion
   state transitions with wallet deletion so the selection, site permissions and
   active-address broadcast follow the same rules
   ([#162](https://git.eeqj.de/sneak/AutistMask/issues/162)).
+- 2026-08-12: An unreported `holders_count` is now parsed as `null` rather than
+  `0`, so the low-holder rule declines to judge an unknown count instead of
+  hiding a legitimate token as spam, in both the transaction history and the
+  Send token selector ([#230](https://git.eeqj.de/sneak/AutistMask/issues/230)).
+- 2026-08-12: Bundled token list documentation no longer states a count. The
+  four "top 250" claims in `README.md` and the "roughly 500" claim in
+  `docs/README.md` are replaced with a description of how the list is actually
+  selected — a point-in-time CoinGecko snapshot of the highest-market-cap
+  Ethereum mainnet ERC-20s — with `TOKENS` in `src/shared/tokenList.js` named as
+  the authoritative set
+  ([#239](https://git.eeqj.de/sneak/AutistMask/issues/239)).
+- 2026-08-11: libsodium runs on WebAssembly in the shipped builds —
+  `'wasm-unsafe-eval'` added to both manifest CSPs after measuring the wasm2js
+  fallback at 20x the Argon2id cost, pinned in both directions by
+  `tests/manifest.test.js` and observed in the real popup by the e2e suite
+  ([#182](https://git.eeqj.de/sneak/AutistMask/issues/182)).
 - 2026-08-11: Known-symbol spoof verification became a Settings toggle
   (`hideSpoofedSymbols`), on by default, governing the transaction-history
   filter and the fraud-contract learning it feeds
@@ -60,6 +76,11 @@ undefined identifiers, which is how
 - 2026-08-11: UTC Timestamps checkbox moved from the Token Spam Protection well
   into Display, next to the theme selector
   ([#212](https://git.eeqj.de/sneak/AutistMask/issues/212)).
+- 2026-08-11: Network fee counted in the confirmation-screen balance check for
+  both ETH and ERC-20 sends, reserving what the node actually charges a type-2
+  transaction, with the arithmetic in a pure, unit-tested
+  `src/shared/txValidation.js`
+  ([#154](https://git.eeqj.de/sneak/AutistMask/issues/154)).
 - 2026-08-11: A dust threshold of `0` now means "hide nothing" instead of
   falling back to the 100,000 gwei default, and every address comparison in
   `src/shared/transactions.js` goes through one case-normalising helper so a

docs/README.md

@@ -269,7 +269,10 @@ The confirmation screen shows:
 - **From and To addresses** with identicons and Etherscan links
 - **Amount** with USD estimate
 - **Your current balance** with USD estimate
-- **Estimated network fee** in ETH with USD estimate
+- **Network fee** — what the transfer is expected to cost, in ETH with a USD
+  estimate, and below it the larger amount reserved until it confirms. The
+  reserve is what the network requires up front and what the balance check gates
+  on; the refund of the difference is why the two differ
 - **Warnings** if the recipient is a contract, a burn address, one of your own
   addresses, on the bundled scam-address list, or labelled as a phisher on
   Etherscan
@@ -324,17 +327,19 @@ individually removed to reset their permissions.
 AutistMask includes several defenses against common Ethereum scams, all enabled
 by default:
 
-**Known token symbol verification.** AutistMask ships a list of roughly 500
+**Known token symbol verification.** AutistMask ships a bundled list of
-legitimate ERC-20 tokens with their contract addresses. If a transaction or
+high-market-cap ERC-20 tokens with their legitimate contract addresses — a
-balance claims to involve a known symbol (like "ETH" or "USDT") but comes from
+point-in-time snapshot of the highest-market-cap Ethereum mainnet ERC-20s, fixed
-an unrecognized contract, it is identified as a spoof and hidden. In your
+at build time and updated only when a new release ships a newer snapshot. If a
-transaction history this is the "Hide fake tokens impersonating a known symbol"
+transaction or balance claims to involve a known symbol (like "ETH" or "USDT")
-setting, which you can switch off; doing so also stops new entries being added
+but comes from an unrecognized contract, it is identified as a spoof and hidden.
-to the fraud contract blocklist below, since detecting a spoof is what fills it.
+In your transaction history this is the "Hide fake tokens impersonating a known
-The send token list always applies the check. Your balances apply it too, with
+symbol" setting, which you can switch off; doing so also stops new entries being
-one exception: a token claiming the symbol "ETH" is not filtered there, so a
+added to the fraud contract blocklist below, since detecting a spoof is what
-fake "ETH" token can still show up in your balance list even though it is hidden
+fills it. The send token list always applies the check. Your balances apply it
-from your transaction history and from the send token list.
+too, with one exception: a token claiming the symbol "ETH" is not filtered
+there, so a fake "ETH" token can still show up in your balance list even though
+it is hidden from your transaction history and from the send token list.
 
 **Low-holder token filtering.** Tokens with fewer than 1,000 holders are hidden
 from transaction history and the send token list, and are left out of your

manifest/chrome.json

@@ -5,6 +5,9 @@
     "description": "Minimal Ethereum wallet for Chrome",
     "permissions": ["storage", "activeTab", "alarms"],
     "host_permissions": ["<all_urls>"],
+    "content_security_policy": {
+        "extension_pages": "script-src 'self' 'wasm-unsafe-eval'; object-src 'self'"
+    },
     "action": {
         "default_popup": "src/popup/index.html"
     },

manifest/firefox.json

@@ -4,6 +4,7 @@
     "version": "0.1.0",
     "description": "Minimal Ethereum wallet for Firefox",
     "permissions": ["storage", "activeTab", "alarms", "<all_urls>"],
+    "content_security_policy": "script-src 'self' 'wasm-unsafe-eval'; object-src 'self'",
     "browser_action": {
         "default_popup": "src/popup/index.html"
     },

src/popup/index.html

@@ -584,10 +584,18 @@
                     <div id="confirm-balance" class="text-xs"></div>
                 </div>
                 <div id="confirm-fee" class="mb-3" style="visibility: hidden">
-                    <div class="text-xs text-muted mb-1">
+                    <div class="text-xs text-muted mb-1">Network fee</div>
-                        Estimated network fee
-                    </div>
                     <div id="confirm-fee-amount" class="text-xs"></div>
+                    <!-- Holds its one line of space from the first paint, so
+                    the reserve appearing when the estimate lands moves
+                    nothing. The placeholder is never seen. -->
+                    <div
+                        id="confirm-fee-reserve"
+                        class="text-xs text-muted"
+                        style="visibility: hidden"
+                    >
+                        reserve pending
+                    </div>
                 </div>
                 <div
                     id="confirm-warnings"
@@ -649,6 +657,31 @@
                     class="mb-2 border border-border border-dashed p-2"
                     style="visibility: hidden; min-height: 1.25rem"
                 ></div>
+                <div
+                    id="confirm-amount-fee-error"
+                    class="mb-2 border border-border border-dashed p-2 text-xs"
+                    style="visibility: hidden"
+                >
+                    Your balance does not cover this amount plus the network
+                    fee. Please go back and send a smaller amount.
+                </div>
+                <div
+                    id="confirm-gas-error"
+                    class="mb-2 border border-border border-dashed p-2 text-xs"
+                    style="visibility: hidden"
+                >
+                    You do not have enough ETH to pay the network fee for this
+                    transfer. Please add ETH to this address and try again.
+                </div>
+                <div
+                    id="confirm-fee-unknown-error"
+                    class="mb-2 border border-border border-dashed p-2 text-xs"
+                    style="visibility: hidden"
+                >
+                    The network fee could not be estimated, so this transaction
+                    cannot be checked against your balance. Please go back and
+                    try again.
+                </div>
                 <div class="mb-2">
                     <label class="block mb-1 text-xs">Password</label>
                     <input
@@ -1132,14 +1165,19 @@
                 >
                     This only stops this wallet from tracking the address.
                     Nothing is destroyed and no key is deleted. Any funds at the
-                    address stay exactly where they are, the address remains
+                    address stay exactly where they are, and the address remains
-                    yours, and it can be brought back at any time by importing
+                    yours. Any site permissions granted to this address are
-                    this wallet's recovery phrase again. Any site permissions
+                    forgotten.
-                    granted to this address are forgotten.
                 </div>
+                <!-- Filled by src/popup/views/deleteAddress.js: the route
+                     back names the wallet's own kind of key material. -->
+                <div
+                    id="delete-address-recovery"
+                    class="text-xs mb-2 border border-border border-dashed p-2"
+                ></div>
                 <div
                     id="delete-address-balance"
-                    class="text-xs mb-2 min-h-[1.25rem]"
+                    class="text-xs mb-2 min-h-[1.25rem] pointer-events-none"
                 >
                     &nbsp;
                 </div>

src/popup/views/confirmTx.js

@@ -32,11 +32,24 @@ const {
     getFullWarnings,
 } = require("../../shared/addressWarnings");
 const { ERC20_ABI, isBurnAddress } = require("../../shared/constants");
+const {
+    CODES,
+    FEE_PENDING,
+    FEE_KNOWN,
+    FEE_UNAVAILABLE,
+    feeReserveWei,
+    feeEstimateWei,
+    validateTransfer,
+} = require("../../shared/txValidation");
 const { log } = require("../../shared/log");
 const makeBlockie = require("ethereum-blockies-base64");
 const txStatus = require("./txStatus");
 
 let pendingTx = null;
+// Network fee for the transaction currently on screen. Reset by show() and
+// filled in by estimateGas() when the estimate resolves or fails.
+let feeStatus = FEE_PENDING;
+let feeWei = null;
 
 function restore() {
     const d = state.viewData;
@@ -67,6 +80,8 @@ function valueWithUsd(text, usdAmount) {
 
 function show(txInfo) {
     pendingTx = txInfo;
+    feeStatus = FEE_PENDING;
+    feeWei = null;
 
     const isErc20 = txInfo.token !== "ETH";
     const symbol = isErc20 ? txInfo.tokenSymbol || "?" : "ETH";
@@ -153,50 +168,14 @@ function show(txInfo) {
         warningsEl.style.visibility = "hidden";
     }
 
-    // Check for errors
+    // The two fee messages are mutually exclusive per transaction type, and
-    const errors = [];
+    // the type is known here, before the first paint. Drop the one that can
-    if (isErc20) {
+    // never apply and reserve the space of the one that can, so the async
-        const tokenBal = parseFloat(txInfo.tokenBalance || "0");
+    // estimate landing later never moves anything.
-        if (parseFloat(txInfo.amount) > tokenBal) {
+    $("confirm-amount-fee-error").classList.toggle("hidden", isErc20);
-            errors.push(
+    $("confirm-gas-error").classList.toggle("hidden", !isErc20);
-                "Insufficient " +
-                    symbol +
-                    " balance. You have " +
-                    txInfo.tokenBalance +
-                    " " +
-                    symbol +
-                    " but are trying to send " +
-                    txInfo.amount +
-                    " " +
-                    symbol +
-                    ".",
-            );
-        }
-    } else if (parseFloat(txInfo.amount) > parseFloat(txInfo.balance)) {
-        errors.push(
-            "Insufficient balance. You have " +
-                txInfo.balance +
-                " ETH but are trying to send " +
-                txInfo.amount +
-                " ETH.",
-        );
-    }
 
-    const errorsEl = $("confirm-errors");
+    renderValidation(txInfo);
-    const sendBtn = $("btn-confirm-send");
-    if (errors.length > 0) {
-        errorsEl.innerHTML = errors
-            .map((e) => `<div class="text-xs">${e}</div>`)
-            .join("");
-        errorsEl.style.visibility = "visible";
-        sendBtn.disabled = true;
-        sendBtn.classList.add("text-muted");
-    } else {
-        errorsEl.innerHTML = "";
-        errorsEl.style.visibility = "hidden";
-        sendBtn.disabled = false;
-        sendBtn.classList.remove("text-muted");
-    }
 
     // Reset password field and error
     $("confirm-tx-password").value = "";
@@ -205,6 +184,7 @@ function show(txInfo) {
     // Gas estimate — show placeholder then fetch async
     $("confirm-fee").style.visibility = "visible";
     $("confirm-fee-amount").textContent = "Estimating...";
+    setVisible("confirm-fee-reserve", false);
     state.viewData = { pendingTx: txInfo };
     showView("confirm-tx");
     attachCopyHandlers("view-confirm-tx");
@@ -224,11 +204,101 @@ function show(txInfo) {
     checkRecipientHistory(txInfo);
 }
 
+// Render the balance check for the transaction on screen. Called once during
+// show() and again when the fee estimate resolves or fails. Every element it
+// touches already occupies its space, so re-running it never moves anything.
+function renderValidation(txInfo) {
+    const isErc20 = txInfo.token !== "ETH";
+    const symbol = isErc20 ? txInfo.tokenSymbol || "?" : "ETH";
+
+    const { canSend, codes } = validateTransfer({
+        isErc20,
+        amount: txInfo.amount,
+        ethBalance: txInfo.balance,
+        tokenBalance: txInfo.tokenBalance,
+        feeStatus,
+        feeWei,
+    });
+
+    // Messages carrying the user's own numbers are built here; the fixed
+    // sentences live in the reserved elements in index.html.
+    const messages = [];
+    if (codes.includes(CODES.AMOUNT_INVALID)) {
+        messages.push("Please enter a valid amount to send.");
+    }
+    if (codes.includes(CODES.INSUFFICIENT_TOKEN)) {
+        messages.push(
+            "Insufficient " +
+                symbol +
+                " balance. You have " +
+                txInfo.tokenBalance +
+                " " +
+                symbol +
+                " but are trying to send " +
+                txInfo.amount +
+                " " +
+                symbol +
+                ".",
+        );
+    }
+    if (codes.includes(CODES.INSUFFICIENT_ETH)) {
+        messages.push(
+            "Insufficient balance. You have " +
+                txInfo.balance +
+                " ETH but are trying to send " +
+                txInfo.amount +
+                " ETH.",
+        );
+    }
+
+    const errorsEl = $("confirm-errors");
+    if (messages.length > 0) {
+        errorsEl.innerHTML = messages
+            .map((m) => `<div class="text-xs">${escapeHtml(m)}</div>`)
+            .join("");
+        errorsEl.style.visibility = "visible";
+    } else {
+        errorsEl.innerHTML = "";
+        errorsEl.style.visibility = "hidden";
+    }
+
+    setVisible(
+        "confirm-amount-fee-error",
+        codes.includes(CODES.INSUFFICIENT_ETH_WITH_FEE),
+    );
+    setVisible(
+        "confirm-gas-error",
+        codes.includes(CODES.INSUFFICIENT_ETH_FOR_FEE),
+    );
+    setVisible(
+        "confirm-fee-unknown-error",
+        codes.includes(CODES.FEE_UNAVAILABLE),
+    );
+
+    // While the estimate is in flight there is no error to show — the fee
+    // line already reads "Estimating..." — but sending stays blocked so a
+    // transaction the fee would break cannot be signed in the meantime.
+    const sendBtn = $("btn-confirm-send");
+    sendBtn.disabled = !canSend;
+    sendBtn.classList.toggle("text-muted", !canSend);
+}
+
+function setVisible(id, visible) {
+    $(id).style.visibility = visible ? "visible" : "hidden";
+}
+
+// A fee in wei as an ETH string, truncated to 6 decimal places.
+function formatFeeEth(wei) {
+    const parts = formatEther(wei).split(".");
+    const dec =
+        parts.length > 1 ? parts[1].slice(0, 6).replace(/0+$/, "") || "0" : "0";
+    return parts[0] + "." + dec + " ETH";
+}
+
 async function estimateGas(txInfo) {
     try {
         const provider = getProvider(state.rpcUrl);
         const feeData = await provider.getFeeData();
-        const gasPrice = feeData.gasPrice;
         let gasLimit;
 
         if (txInfo.token === "ETH") {
@@ -246,21 +316,55 @@ async function estimateGas(txInfo) {
             });
         }
 
-        const gasCostWei = gasLimit * gasPrice;
+        // What the node will require to be reserved, which is what the gate
-        const gasCostEth = formatEther(gasCostWei);
+        // must be: the send pins no fee fields, so it is broadcast as a
-        // Format to 6 significant decimal places
+        // type-2 transaction priced at maxFeePerGas.
-        const parts = gasCostEth.split(".");
+        const gasCostWei = feeReserveWei(gasLimit, feeData);
-        const dec =
+        if (gasCostWei === null) {
-            parts.length > 1
+            throw new Error("no usable gas price from the provider");
-                ? parts[1].slice(0, 6).replace(/0+$/, "") || "0"
+        }
-                : "0";
+        // What the transaction is expected to cost, which is a different and
-        const feeStr = parts[0] + "." + dec + " ETH";
+        // usually much smaller number. Both are shown: quoting only the
+        // reserve overstates the typical cost by roughly double on mainnet,
+        // and quoting only the estimate contradicts the balance check.
+        const estimateWei = feeEstimateWei(gasLimit, feeData);
+        // The user may have left this transaction while the estimate was in
+        // flight; a stale fee must not reach the screen or the balance check.
+        if (pendingTx !== txInfo) return;
+
         const ethPrice = getPrice("ETH");
-        const feeUsd = ethPrice ? parseFloat(gasCostEth) * ethPrice : null;
+        const usd = (wei) =>
-        $("confirm-fee-amount").textContent = valueWithUsd(feeStr, feeUsd);
+            ethPrice ? parseFloat(formatEther(wei)) * ethPrice : null;
+
+        if (estimateWei !== null && estimateWei < gasCostWei) {
+            $("confirm-fee-amount").textContent = valueWithUsd(
+                "~" + formatFeeEth(estimateWei),
+                usd(estimateWei),
+            );
+            $("confirm-fee-reserve").textContent =
+                "up to " + formatFeeEth(gasCostWei) + " reserved";
+            setVisible("confirm-fee-reserve", true);
+        } else {
+            // No spread to report: either there is no estimate, or the node
+            // quotes a gas price at or above maxFeePerGas, so the expected
+            // cost is not below the reserve. Show the reserve alone.
+            $("confirm-fee-amount").textContent = valueWithUsd(
+                formatFeeEth(gasCostWei),
+                usd(gasCostWei),
+            );
+            setVisible("confirm-fee-reserve", false);
+        }
+        feeStatus = FEE_KNOWN;
+        feeWei = gasCostWei;
+        renderValidation(txInfo);
     } catch (e) {
         log.errorf("gas estimation failed:", e.message);
+        if (pendingTx !== txInfo) return;
         $("confirm-fee-amount").textContent = "Unable to estimate";
+        setVisible("confirm-fee-reserve", false);
+        feeStatus = FEE_UNAVAILABLE;
+        feeWei = null;
+        renderValidation(txInfo);
     }
 }
 

src/popup/views/deleteAddress.js

@@ -14,7 +14,11 @@ const {
     goBack,
     renderAddressHtml,
     attachCopyHandlers,
+    addressHoldsFunds,
+    balanceLinesForAddress,
 } = require("./helpers");
+const { formatUsd, getAddressValueUsd } = require("../../shared/prices");
+const { walletHasRecoveryPhrase } = require("../../shared/wallet");
 const { state, saveState } = require("../../shared/state");
 const {
     canRemoveAddress,
@@ -33,6 +37,71 @@ function setFlash(msg) {
     el.style.visibility = msg ? "visible" : "hidden";
 }
 
+// What it actually takes to get the address back, which is not what the
+// screen used to claim.
+//
+// Neither obvious route works: "+" derives the next unused index, because
+// wallet.nextIndex is a high-water mark and is deliberately not rewound; and
+// re-importing this wallet's key material is refused as a duplicate by
+// findWalletByXpub() for as long as the wallet is here. What remains is to
+// delete the whole wallet in Settings — which asks for the password and
+// destroys the stored secret — and import again, after which
+// scanForAddresses() rediscovers the address only if it has on-chain
+// activity. An address that was never used is not found by that scan, and
+// the copy must not imply otherwise.
+//
+// The noun follows the wallet: an xprv wallet holds no recovery phrase, and
+// this screen is offered on xprv wallets too.
+function recoveryPathText(wallet) {
+    const secret = walletHasRecoveryPhrase(wallet)
+        ? "recovery phrase"
+        : "extended private key";
+    return (
+        "Getting the address back into this list is not easy, so be sure. " +
+        "Adding an address derives the next unused one, not this one, and " +
+        "importing this " +
+        secret +
+        " again is refused while this wallet is still here. The way back is " +
+        "to delete the whole wallet in Settings, which asks for your " +
+        "password and destroys the stored " +
+        secret +
+        ", and then import that " +
+        secret +
+        " again. The scan that follows only finds addresses that have " +
+        "on-chain activity, so an address that has never been used is not " +
+        "found by it."
+    );
+}
+
+// The balance warning, or a blank line when the address holds nothing.
+//
+// A balance is a reason to be careful, not a reason to refuse: the funds are
+// at the address, not in this list, and stay there either way.
+//
+// "Holds" means ETH or any ERC-20 the wallet knows about — an address with no
+// ETH and a five-figure stablecoin position must not get the blank line on
+// the one screen whose job is to warn. The sentence names no figure of its
+// own: the rendered lines round to four decimals, so a sentence built from a
+// rounded number would report "0.0000 ETH" for an address holding real money.
+// The lines below it carry the amounts, in the same format as Home and
+// AddressDetail, followed by the USD total when prices are known (null on
+// testnet and before the first price fetch, where the line is left off rather
+// than printed as $0.00).
+function balanceWarningHtml(addr) {
+    if (!addressHoldsFunds(addr)) return " ";
+    const usd = getAddressValueUsd(addr);
+    const total =
+        usd === null
+            ? ""
+            : `<div class="text-xs text-muted mt-1">Total: ${formatUsd(usd)}</div>`;
+    return (
+        `<p class="mb-1">This address holds a balance. Removing it does not ` +
+        `move or spend anything; the balance stays at the address.</p>` +
+        balanceLinesForAddress(addr, state.trackedTokens, false) +
+        total
+    );
+}
+
 function show(walletIdx, addrIdx) {
     const wallet = state.wallets[walletIdx];
     const addr = wallet && wallet.addresses[addrIdx];
@@ -49,16 +118,8 @@ function show(walletIdx, addrIdx) {
     });
     attachCopyHandlers(value);
 
-    // A balance is a reason to be careful, not a reason to refuse: the funds
+    $("delete-address-recovery").textContent = recoveryPathText(wallet);
-    // are at the address, not in this list, and stay there either way.
+    $("delete-address-balance").innerHTML = balanceWarningHtml(addr);
-    const balance = parseFloat(addr.balance || "0");
-    $("delete-address-balance").innerHTML =
-        balance > 0
-            ? "This address holds " +
-              balance.toFixed(4) +
-              " ETH. Removing it does not move or spend anything; the balance " +
-              "stays at the address."
-            : "&nbsp;";
 
     setFlash("");
     showView("delete-address-confirm");
@@ -109,4 +170,7 @@ function init(_ctx) {
     });
 }
 
-module.exports = { init, show };
+// recoveryPathText and balanceWarningHtml are exported so the two pieces of
+// copy that carry the screen's substance can be tested without a DOM; show()
+// is a one-line assignment for each.
+module.exports = { init, show, recoveryPathText, balanceWarningHtml };

src/popup/views/helpers.js

@@ -218,6 +218,20 @@ function balanceLinesForAddress(addr, trackedTokens, showZero) {
     return html;
 }
 
+// Whether an address holds anything at all: ETH or any ERC-20 the wallet
+// knows about. Deliberately unrounded — the rendered lines round to four
+// decimals, so a dust balance displays as 0.0000 while still being real
+// money at a real address. Callers that warn about holdings must ask this,
+// not the rendered figure.
+function addressHoldsFunds(addr) {
+    if (!addr) return false;
+    if (parseFloat(addr.balance || "0") > 0) return true;
+    for (const t of addr.tokenBalances || []) {
+        if (parseFloat(t.balance || "0") > 0) return true;
+    }
+    return false;
+}
+
 // Truncate the middle of a string, replacing removed characters with "…".
 // Safety: refuses to truncate more than 10 characters, which is the maximum
 // that still prevents address spoofing attacks (see Display Consistency in
@@ -464,6 +478,7 @@ module.exports = {
     flashCopyFeedback,
     balanceLine,
     balanceLinesForAddress,
+    addressHoldsFunds,
     addressColor,
     addressDotHtml,
     escapeHtml,

src/popup/views/send.js

@@ -13,6 +13,7 @@ const { state, currentAddress } = require("../../shared/state");
 let ctx;
 const { getProvider } = require("../../shared/balances");
 const { KNOWN_SYMBOLS, resolveSymbol } = require("../../shared/tokenList");
+const { isLowHolderCount } = require("../../shared/holders");
 const { getAddress } = require("ethers");
 
 const ZERO_ADDRESS = "0x0000000000000000000000000000000000000000";
@@ -132,7 +133,10 @@ function renderSendTokenSelect(addr) {
     for (const t of addr.tokenBalances || []) {
         if (isSpoofedToken(t)) continue;
         if (fraudSet.has(t.address.toLowerCase())) continue;
-        if (state.hideLowHolderTokens && (t.holders || 0) < 1000) continue;
+        // An unknown holder count does not withhold a token the user holds:
+        // only a count the explorer actually reported as below the threshold
+        // does.  Otherwise a missing field makes a real asset unspendable.
+        if (state.hideLowHolderTokens && isLowHolderCount(t.holders)) continue;
         const opt = document.createElement("option");
         opt.value = t.address;
         opt.textContent = t.symbol;

src/shared/balances.js

@@ -12,6 +12,7 @@ const { ERC20_ABI } = require("./constants");
 const { log, debugFetch } = require("./log");
 const { deriveAddressFromXpub } = require("./wallet");
 const { KNOWN_SYMBOLS, TOKEN_BY_ADDRESS } = require("./tokenList");
+const { LOW_HOLDER_THRESHOLD, parseHoldersCount } = require("./holders");
 
 // Use a static network to skip auto-detection (which can fail and cause
 // "could not coalesce error" on some RPC endpoints like Cloudflare).
@@ -70,10 +71,20 @@ async function fetchTokenBalances(address, blockscoutUrl, trackedTokens) {
             if (bal === "0.0") continue;
 
             const tokenAddr = (item.token.address_hash || "").toLowerCase();
-            const holders = parseInt(item.token.holders_count || "0", 10);
+            // null means the explorer reported no count, which is not the
+            // same as a count of zero.  This gate is not the low-holder
+            // display filter: it has no user-facing off switch and governs
+            // the whole balance list, so it stays strict and admits a token
+            // only on a reported count — an unreported one is no evidence.
+            // A legitimate token still reaches the list through the known
+            // token list or by the user tracking it, and the null is carried
+            // through to the views, where the two low-holder filters treat
+            // an unknown count as "do not judge" rather than as zero.
+            const holders = parseHoldersCount(item.token.holders_count);
             const isKnown = TOKEN_BY_ADDRESS.has(tokenAddr);
             const isTracked = trackedSet.has(tokenAddr);
-            const hasEnoughHolders = holders >= 1000;
+            const hasEnoughHolders =
+                holders !== null && holders >= LOW_HOLDER_THRESHOLD;
 
             // Skip spam tokens the user never asked to see
             if (!isKnown && !isTracked && !hasEnoughHolders) continue;
@@ -278,6 +289,7 @@ async function scanForAddresses(xpub, rpcUrl, gapLimit = 5) {
 }
 
 module.exports = {
+    fetchTokenBalances,
     refreshBalances,
     lookupTokenInfo,
     getProvider,

src/shared/holders.js

@@ -0,0 +1,32 @@
+// Holder counts, and the one rule that decides whether a count is "low".
+//
+// The block explorer's holders_count is optional: it is absent on a token it
+// has only just indexed, and it goes missing on a degraded or changed API.
+// Absent means the count is unknown.  It does not mean the token has no
+// holders, and collapsing the two hides a token the user really holds as if
+// it were spam.  Every call site reads the count through here so the
+// distinction cannot be lost again in one place while holding in the others.
+
+const LOW_HOLDER_THRESHOLD = 1000;
+
+// Parse an explorer-supplied holders_count into a number, or null when the
+// explorer did not report one.  Anything unparseable is unknown too: a count
+// we cannot read is not a count of zero.
+function parseHoldersCount(raw) {
+    if (raw === null || raw === undefined || raw === "") return null;
+    const n = parseInt(raw, 10);
+    return Number.isFinite(n) ? n : null;
+}
+
+// True only for a token the explorer reported as having fewer holders than
+// the threshold.  An unknown count is never low: showing a spam token the
+// user can see is unusual costs less than hiding an asset they own.
+function isLowHolderCount(holders) {
+    return holders != null && holders < LOW_HOLDER_THRESHOLD;
+}
+
+module.exports = {
+    LOW_HOLDER_THRESHOLD,
+    parseHoldersCount,
+    isLowHolderCount,
+};

src/shared/transactions.js

@@ -9,6 +9,7 @@
 const { formatEther, formatUnits } = require("ethers");
 const { log, debugFetch } = require("./log");
 const { KNOWN_SYMBOLS, TOKEN_BY_ADDRESS } = require("./tokenList");
+const { parseHoldersCount, isLowHolderCount } = require("./holders");
 
 // Ethereum addresses are case-insensitive: EIP-55 mixed case is a checksum
 // over the address, not part of its identity.  Every address comparison in
@@ -116,7 +117,10 @@ function parseTokenTransfer(tt, addrLower) {
         contractAddress: normalizeAddress(
             tt.token?.address_hash || tt.token?.address || "",
         ),
-        holders: parseInt(tt.token?.holders_count || "0", 10),
+        // null when the explorer reported no count: unknown, not zero.  The
+        // low-holder filter declines to judge a null, so a legitimate token
+        // is not hidden because a field went missing upstream.
+        holders: parseHoldersCount(tt.token?.holders_count),
     };
 }
 
@@ -292,12 +296,13 @@ function filterTransactions(txs, filters = {}) {
             continue;
         }
 
-        // Filter low-holder tokens (<1000) if setting is on
+        // Filter low-holder tokens (<1000) if setting is on.  A token whose
+        // holder count the explorer did not report is kept: only a reported
+        // count below the threshold is "low".
         if (
             filters.hideLowHolderTokens &&
             tx.contractAddress &&
-            tx.holders !== null &&
+            isLowHolderCount(tx.holders)
-            tx.holders < 1000
         ) {
             continue;
         }

src/shared/txValidation.js

@@ -0,0 +1,171 @@
+// Balance arithmetic for the transaction confirmation screen.
+//
+// Pure: no DOM, no network, no state. Everything is exact integer math on
+// 18-decimal fixed point (wei for ETH), so it can be unit tested directly
+// instead of through the confirmation view. The caller maps the returned
+// codes to the reserved message elements on the screen.
+//
+// Human decimal strings ("1.25") are scaled to 18 decimals for comparison.
+// That scale is independent of a token's own decimals: both the amount and
+// the token balance arrive as human decimal strings, so comparing them at a
+// common scale is exact.
+
+const { parseUnits } = require("ethers");
+
+const SCALE_DECIMALS = 18;
+
+// Whether the asynchronous fee estimate has arrived yet.
+const FEE_PENDING = "pending";
+const FEE_KNOWN = "known";
+const FEE_UNAVAILABLE = "unavailable";
+
+const CODES = {
+    // The amount is not a non-negative number we can do exact arithmetic on.
+    AMOUNT_INVALID: "amount-invalid",
+    // ERC-20: the token amount exceeds the token balance.
+    INSUFFICIENT_TOKEN: "insufficient-token",
+    // ETH: the amount alone already exceeds the ETH balance.
+    INSUFFICIENT_ETH: "insufficient-eth",
+    // ETH: the amount fits, the amount plus the network fee does not.
+    INSUFFICIENT_ETH_WITH_FEE: "insufficient-eth-with-fee",
+    // ERC-20: the token balance covers the transfer, the ETH balance does
+    // not cover the network fee it costs.
+    INSUFFICIENT_ETH_FOR_FEE: "insufficient-eth-for-fee",
+    // The fee estimate has not arrived yet.
+    FEE_PENDING: "fee-pending",
+    // The fee estimate failed. Unknown is never treated as zero.
+    FEE_UNAVAILABLE: "fee-unavailable",
+};
+
+// The fee that must be reserved for a transaction, in wei: the amount the
+// node will require, not the amount the transaction is expected to cost.
+//
+// A send that pins no fee fields is populated by ethers as a type-2
+// (EIP-1559) transaction, and a node validates that against
+// `value + gasLimit * maxFeePerGas`. ethers derives maxFeePerGas as
+// `baseFeePerGas * 2 + maxPriorityFeePerGas`, so reserving `gasPrice`
+// (roughly `baseFee + tip`) under-reserves by about `gasLimit * baseFee` and
+// lets through a transaction the node then rejects with "insufficient funds
+// for gas * price + value". gasPrice is the fallback only for a network that
+// offers no type-2 pricing at all.
+//
+// Returns null when no usable price is available, which the caller must treat
+// as a failed estimate rather than as a free transaction.
+function feeReserveWei(gasLimit, feeData) {
+    if (typeof gasLimit !== "bigint" || gasLimit < 0n) return null;
+    const price = feeData?.maxFeePerGas ?? feeData?.gasPrice;
+    if (typeof price !== "bigint" || price < 0n) return null;
+    return gasLimit * price;
+}
+
+// What the transaction is expected to actually cost, in wei — not what must
+// be reserved for it. A type-2 transaction is charged `baseFee + tip` per gas
+// and refunded the rest of the cap, and `eth_gasPrice` reports roughly that,
+// so gasPrice is the estimate and maxFeePerGas is the reserve. On a network
+// with no type-2 pricing the two are the same number.
+//
+// Display only: nothing gates on this. Returns null on the same unusable
+// inputs as feeReserveWei().
+function feeEstimateWei(gasLimit, feeData) {
+    if (typeof gasLimit !== "bigint" || gasLimit < 0n) return null;
+    const price = feeData?.gasPrice ?? feeData?.maxFeePerGas;
+    if (typeof price !== "bigint" || price < 0n) return null;
+    return gasLimit * price;
+}
+
+// Scale a human decimal string to 18-decimal fixed point. Returns null when
+// the value is not a decimal number or carries more precision than the scale
+// can hold, which the caller must treat as unusable rather than as zero.
+function toFixedPoint(value) {
+    if (typeof value !== "string" && typeof value !== "number") return null;
+    const text = String(value).trim();
+    if (text === "") return null;
+    try {
+        return parseUnits(text, SCALE_DECIMALS);
+    } catch (e) {
+        return null;
+    }
+}
+
+// Validate a pending transfer against the balances that must cover it.
+//
+//   isErc20      — token transfer rather than a native ETH transfer
+//   amount       — human decimal string being sent, non-negative. Anything
+//                  else, a negative value included, is an unusable amount
+//                  rather than an amount that passes every comparison.
+//   ethBalance   — human decimal string, the sender's ETH balance
+//   tokenBalance — human decimal string, the sender's token balance
+//   feeStatus    — FEE_PENDING, FEE_KNOWN or FEE_UNAVAILABLE. Anything else
+//                  is treated as FEE_UNAVAILABLE.
+//   feeWei       — the fee reserve in wei from feeReserveWei(), as a
+//                  non-negative bigint, when FEE_KNOWN. Any other value makes
+//                  the fee unavailable rather than zero.
+//
+// Returns { canSend, codes }. Every code blocks sending: canSend is true
+// only when nothing was found.
+function validateTransfer({
+    isErc20 = false,
+    amount,
+    ethBalance,
+    tokenBalance,
+    feeStatus = FEE_PENDING,
+    feeWei = null,
+} = {}) {
+    const codes = [];
+
+    const amountFp = toFixedPoint(amount);
+    const ethFp = toFixedPoint(ethBalance) ?? 0n;
+
+    // A negative amount parses to a valid bigint, so every comparison below
+    // is trivially false and the send clears the screen — then dies at encode
+    // time in parseEther(). Unusable, on the same footing as a malformed fee.
+    if (amountFp === null || amountFp < 0n) {
+        codes.push(CODES.AMOUNT_INVALID);
+        return { canSend: false, codes };
+    }
+
+    // Fail closed. Anything that is not a usable fee under a recognised
+    // status — a malformed feeWei, or a status this module does not know —
+    // is an unavailable estimate, never a fee of zero. Every such input errs
+    // in the direction that lets money out, so none of them is trusted.
+    const known =
+        feeStatus === FEE_KNOWN && typeof feeWei === "bigint" && feeWei >= 0n;
+    let status = feeStatus;
+    if (feeStatus === FEE_KNOWN && !known) status = FEE_UNAVAILABLE;
+    if (status !== FEE_KNOWN && status !== FEE_PENDING) {
+        status = FEE_UNAVAILABLE;
+    }
+
+    const feeFp = known ? feeWei : null;
+
+    if (isErc20) {
+        const tokenFp = toFixedPoint(tokenBalance) ?? 0n;
+        if (amountFp > tokenFp) codes.push(CODES.INSUFFICIENT_TOKEN);
+        if (feeFp !== null && feeFp > ethFp) {
+            codes.push(CODES.INSUFFICIENT_ETH_FOR_FEE);
+        }
+    } else if (amountFp > ethFp) {
+        codes.push(CODES.INSUFFICIENT_ETH);
+    } else if (feeFp !== null && amountFp + feeFp > ethFp) {
+        codes.push(CODES.INSUFFICIENT_ETH_WITH_FEE);
+    }
+
+    // An unknown fee is never assumed to be zero: sending stays blocked
+    // until the estimate arrives, and stays blocked if it never does.
+    if (status === FEE_PENDING) codes.push(CODES.FEE_PENDING);
+    if (status === FEE_UNAVAILABLE) codes.push(CODES.FEE_UNAVAILABLE);
+
+    return { canSend: codes.length === 0, codes };
+}
+
+module.exports = {
+    CODES,
+    FEE_PENDING,
+    FEE_KNOWN,
+    FEE_UNAVAILABLE,
+    SCALE_DECIMALS,
+    feeReserveWei,
+    feeEstimateWei,
+    toFixedPoint,
+    validateTransfer,
+};

src/shared/vault.js

@@ -1,14 +1,80 @@
 // Vault: password-based encryption of secrets using libsodium.
 // Uses Argon2id for key derivation and XSalsa20-Poly1305 for encryption.
 // All crypto operations are delegated to libsodium — no raw primitives.
+//
+// Backend: WebAssembly, deliberately (#182).
+//
+// libsodium ships one file containing both a WebAssembly build and a
+// wasm2js ("asm.js") translation of it. It tries WASM first and, if
+// instantiation throws, silently swaps in the translation. An extension
+// CSP of plain script-src 'self' refuses WASM, so every popup load used
+// to take that fallback — announced by nothing but an uncaught
+// CompileError in the console.
+//
+// Measured here, same Argon2id parameters (OPSLIMIT_INTERACTIVE,
+// MEMLIMIT_INTERACTIVE = 2 passes over 64MiB), node 22 on this machine:
+// WASM 141-198ms per derivation, wasm2js 3204-3660ms. The work factor is
+// identical either way — it is set by the ops/mem parameters, not by wall
+// time — so the fallback bought no security, it only made every password
+// operation take three and a half seconds, and the wallet asks for the
+// password on every signature.
+//
+// So both manifests declare 'wasm-unsafe-eval' for extension pages. That
+// keyword permits compiling WebAssembly and nothing else: not eval() of
+// strings, not inline script, not remote script. Reaching it requires
+// already executing script in the extension page, which is total
+// compromise on its own. 'unsafe-eval' would be a different matter and is
+// not granted. tests/manifest.test.js pins both policies to exactly
+// "'self' 'wasm-unsafe-eval'" so neither the grant nor the surrounding
+// strictness can drift unnoticed.
+//
+// The fallback still exists, and a wallet that refuses to decrypt is
+// worse than a slow one, so it is not disabled — it is made loud:
+// cryptoBackend() reports which backend this realm can run, ensureReady()
+// logs an error if it is not WASM, tests/vaultBackend.test.js asserts the
+// unit tests exercise the WASM backend, and the end-to-end suite asserts
+// it in the real popup under the real manifest.
 
 const sodium = require("libsodium-wrappers-sumo");
+const { log } = require("./log");
+
+// An empty WebAssembly module: the 8-byte magic number and version header,
+// no sections. Compiling it asks the cheapest possible form of the only
+// question that matters here — may this realm compile WebAssembly at all —
+// which is exactly what a CSP without 'wasm-unsafe-eval' refuses, and
+// exactly what decides which backend libsodium ends up on.
+const EMPTY_WASM_MODULE = new Uint8Array([
+    0x00, 0x61, 0x73, 0x6d, 0x01, 0x00, 0x00, 0x00,
+]);
+
+// "wasm" or "asmjs": whether this realm may compile WebAssembly, which is
+// what decides libsodium's backend when the CSP is the reason it cannot —
+// the case this codebase guards. It probes the realm, not libsodium, so a
+// fallback taken for some other reason (allocation failure, corrupt module)
+// would not be caught here; tests/vaultBackend.test.js checks libsodium's
+// own marker directly.
+async function cryptoBackend() {
+    try {
+        await WebAssembly.compile(EMPTY_WASM_MODULE);
+        return "wasm";
+    } catch (_) {
+        return "asmjs";
+    }
+}
 
 let ready = false;
 
 async function ensureReady() {
     if (!ready) {
         await sodium.ready;
+        if ((await cryptoBackend()) !== "wasm") {
+            log.errorf(
+                "libsodium is running on the wasm2js fallback: this realm " +
+                    "refuses to compile WebAssembly, so every password " +
+                    "derivation costs roughly 20x what it should. See the " +
+                    "backend note in src/shared/vault.js.",
+            );
+        }
         ready = true;
     }
 }
@@ -59,4 +125,4 @@ async function decryptWithPassword(encrypted, password) {
     return sodium.to_string(plaintext);
 }
 
-module.exports = { encryptWithPassword, decryptWithPassword };
+module.exports = { cryptoBackend, decryptWithPassword, encryptWithPassword };

tests/deleteAddress.test.js

@@ -0,0 +1,158 @@
+// Tests for the copy on the address-removal confirmation (issue #162).
+//
+// The screen's whole job is to warn before a destructive-looking action, so
+// the copy is the substance and is tested as such. Two things it must not
+// get wrong: what it takes to get the address back — the app refuses both
+// obvious routes — and what counts as holding something, which is any
+// ERC-20 as well as ETH, at any size, including a balance that rounds to
+// zero at the four decimals the balance lines render. The DOM behaviour
+// around them is driven against the real popup by tests/e2e/run.js.
+
+// helpers.js pulls in state.js, which reads chrome.storage.local at load.
+globalThis.chrome = {
+    storage: { local: { get: async () => ({}), set: async () => {} } },
+};
+
+const { addressHoldsFunds } = require("../src/popup/views/helpers");
+const {
+    recoveryPathText,
+    balanceWarningHtml,
+} = require("../src/popup/views/deleteAddress");
+const { prices, clearPrices } = require("../src/shared/prices");
+
+const USDC = "0xa0b86991c6218b36c1d19d4a2e9eb0ce3606eb48";
+
+const EMPTY = { address: "0x1", balance: "0.0000", tokenBalances: [] };
+const ETH_ONLY = { address: "0x1", balance: "1.5", tokenBalances: [] };
+const DUST = { address: "0x1", balance: "0.00001", tokenBalances: [] };
+const TOKEN_ONLY = {
+    address: "0x1",
+    balance: "0.0000",
+    tokenBalances: [{ address: USDC, symbol: "USDC", balance: "2500.0" }],
+};
+const ZERO_TOKEN = {
+    address: "0x1",
+    balance: "0",
+    tokenBalances: [{ address: USDC, symbol: "USDC", balance: "0" }],
+};
+
+afterEach(() => {
+    clearPrices();
+});
+
+describe("what the screen says it takes to get the address back", () => {
+    // The screen used to promise the address "can be brought back at any
+    // time by importing this wallet's recovery phrase again". That import is
+    // refused as a duplicate for as long as the wallet is present, which it
+    // always is here — a wallet never gives up its last address.
+    test("it does not promise a re-import while the wallet is here", () => {
+        const text = recoveryPathText({ type: "hd" });
+        expect(text).not.toMatch(/at any time/);
+        expect(text).toContain("is refused while this wallet is still here");
+    });
+
+    test("it names deleting the whole wallet as the route back", () => {
+        expect(recoveryPathText({ type: "hd" })).toContain(
+            "delete the whole wallet in Settings",
+        );
+    });
+
+    // The scan after a re-import finds used addresses only, so an address
+    // that never saw a transaction does not come back at all. Saying so is
+    // the difference between a warning and a false reassurance.
+    test("it states the limit: only on-chain activity is found", () => {
+        const text = recoveryPathText({ type: "hd" });
+        expect(text).toContain("only finds addresses that have on-chain");
+        expect(text).toContain("never been used is not found by it");
+    });
+
+    // The screen is offered on xprv wallets too, and an xprv wallet holds no
+    // recovery phrase — telling its owner to import one would send them
+    // looking for words that do not exist.
+    test("an xprv wallet is told about its extended private key", () => {
+        const text = recoveryPathText({ type: "xprv" });
+        expect(text).toContain("extended private key");
+        expect(text).not.toContain("recovery phrase");
+    });
+
+    test("an HD wallet is told about its recovery phrase", () => {
+        const text = recoveryPathText({ type: "hd" });
+        expect(text).toContain("recovery phrase");
+        expect(text).not.toContain("extended private key");
+    });
+});
+
+describe("whether an address holds anything", () => {
+    test("ETH counts", () => {
+        expect(addressHoldsFunds(ETH_ONLY)).toBe(true);
+    });
+
+    // The case that decides the screen: no ETH at all, and $2500 of a
+    // stablecoin sitting at the address.
+    test("an ERC-20 balance counts even with no ETH", () => {
+        expect(addressHoldsFunds(TOKEN_ONLY)).toBe(true);
+    });
+
+    // 0.00001 ETH renders as "0.0000" at four decimals. It is still money.
+    test("an ETH balance below the displayed precision counts", () => {
+        expect(addressHoldsFunds(DUST)).toBe(true);
+    });
+
+    test("an address holding nothing does not", () => {
+        expect(addressHoldsFunds(EMPTY)).toBe(false);
+        expect(addressHoldsFunds(ZERO_TOKEN)).toBe(false);
+    });
+
+    test("a missing address or missing fields do not", () => {
+        expect(addressHoldsFunds(undefined)).toBe(false);
+        expect(addressHoldsFunds({ address: "0x1" })).toBe(false);
+    });
+});
+
+describe("the balance warning on the removal confirmation", () => {
+    test("an address holding nothing gets a blank line, not a warning", () => {
+        expect(balanceWarningHtml(EMPTY)).toBe(" ");
+        expect(balanceWarningHtml(ZERO_TOKEN)).toBe(" ");
+    });
+
+    test("an ERC-20-only address is warned about, and its token listed", () => {
+        const html = balanceWarningHtml(TOKEN_ONLY);
+        expect(html).toContain("This address holds a balance.");
+        expect(html).toContain("does not move or spend anything");
+        expect(html).toContain("USDC");
+        expect(html).toContain("2500.0000");
+    });
+
+    // The rendered line says 0.0000 for this address — that is the display
+    // format, shared with Home and AddressDetail — and the warning is shown
+    // all the same, because the balance is not zero.
+    test("an ETH balance that renders as 0.0000 is warned about", () => {
+        const html = balanceWarningHtml(DUST);
+        expect(html).toContain("This address holds a balance.");
+        expect(html).toContain("<span>0.0000</span>");
+    });
+
+    // The sentence must not assert an amount, because any amount it could
+    // assert has been rounded: "This address holds 0.0000 ETH." is what the
+    // rounded form produces for an address that holds real money.
+    test("the warning sentence asserts no rounded amount", () => {
+        for (const addr of [DUST, ETH_ONLY, TOKEN_ONLY]) {
+            expect(balanceWarningHtml(addr)).not.toMatch(
+                /holds [\d.]+ (ETH|USDC)/,
+            );
+        }
+    });
+
+    test("the USD total is shown when prices are known", () => {
+        prices.ETH = 2000;
+        prices.USDC = 1;
+        expect(balanceWarningHtml(TOKEN_ONLY)).toContain("Total: $2,500.00");
+        expect(balanceWarningHtml(ETH_ONLY)).toContain("Total: $3,000.00");
+    });
+
+    // getAddressValueUsd() returns null on testnet and before the first
+    // price fetch. A "Total: $0.00" there would be a lie about the holdings.
+    test("no USD total is shown when prices are not known", () => {
+        expect(balanceWarningHtml(TOKEN_ONLY)).not.toContain("Total:");
+    });
+});

tests/e2e/harness.js

@@ -22,18 +22,12 @@ const EXT_PATH = path.join(REPO_ROOT, "dist", "chrome");
 // entry must name the issue that will remove it. This list is the one
 // concession in an otherwise zero-tolerance policy: an uncaught error is
 // how this harness caught issue #150 in the first place.
-const ALLOWED_ERRORS = [
+//
-    {
+// Empty, and worth keeping that way. Its only entry was the WASM
-        // libsodium ships a WASM build and an asm.js fallback. The
+// CompileError libsodium provoked on every popup load, deleted with #182
-        // extension CSP (script-src 'self', with no wasm-unsafe-eval)
+// when both manifests started allowing WASM; the run that used to need it
-        // refuses the WASM module on every popup load; libsodium catches
+// is now the run that proves the fix.
-        // it and falls back to asm.js, so the wallet works. Deciding
+const ALLOWED_ERRORS = [];
-        // which backend actually ships is issue #182, and this entry gets
-        // deleted when that lands.
-        issue: "#182",
-        pattern: /Refused to compile or instantiate WebAssembly module/,
-    },
-];
 
 function isAllowed(text) {
     return ALLOWED_ERRORS.some((a) => a.pattern.test(text));
@@ -247,6 +241,26 @@ async function visible(page, selector, timeout = 15000) {
     await page.waitForSelector(selector, { state: "visible", timeout });
 }
 
+// An empty WebAssembly module: magic number and version header, no
+// sections. Compiling it in the popup asks the one question that decides
+// libsodium's backend — may this realm compile WebAssembly — of the real
+// page under the real shipped manifest, which is the only place the
+// answer can be observed. Kept independent of src/shared/vault.js on
+// purpose: a bundle asked to grade itself proves less than an outside
+// observation of the same realm.
+const EMPTY_WASM_MODULE = [0x00, 0x61, 0x73, 0x6d, 0x01, 0x00, 0x00, 0x00];
+
+async function pageCompilesWasm(page) {
+    return page.evaluate(async (bytes) => {
+        try {
+            await WebAssembly.compile(new Uint8Array(bytes));
+            return true;
+        } catch (_) {
+            return false;
+        }
+    }, EMPTY_WASM_MODULE);
+}
+
 async function openPopup(ctx, popupUrl) {
     const page = await ctx.newPage();
     await page.goto(popupUrl);
@@ -293,5 +307,6 @@ module.exports = {
     launch,
     openAddressDetail,
     openPopup,
+    pageCompilesWasm,
     visible,
 };

tests/e2e/run.js

@@ -15,6 +15,7 @@ const {
     launch,
     openAddressDetail,
     openPopup,
+    pageCompilesWasm,
     visible,
 } = require("./harness");
 const { STUB_TOKEN, STUB_TX_HASH } = require("./network");
@@ -60,6 +61,27 @@ test("popup loads and reaches the welcome view", async (env) => {
     assert(title === "AutistMask", "unexpected popup title: " + title);
 });
 
+// The empirical half of #182. The manifest change is only a claim about
+// what the CSP permits; this is the observation. Two things have to hold
+// together, and the run covers both: the popup realm compiles WASM (here),
+// and no WASM refusal or abort is recorded anywhere in the run — the
+// harness allowlist that used to excuse exactly that error is now empty,
+// so a recurrence fails whichever test it lands in rather than being
+// tolerated. Since libsodium's WASM module is embedded in the bundle and
+// needs no fetch, a realm that compiles WASM is a realm where libsodium
+// takes the WASM path, and the next test drives a real vault encryption
+// through it.
+test("the popup compiles WebAssembly under the shipped CSP (#182)", async (env) => {
+    const ok = await pageCompilesWasm(env.page);
+    assert(
+        ok,
+        "the popup refused to compile WebAssembly. The shipped manifest CSP " +
+            "has lost 'wasm-unsafe-eval', so libsodium is back on its wasm2js " +
+            "fallback and every password derivation costs roughly 20x what it " +
+            "should — see the backend note in src/shared/vault.js",
+    );
+});
+
 test("wallet creation through the UI reaches the main view", async (env) => {
     env.phrase = await createWallet(env.page);
     assert(
@@ -433,6 +455,20 @@ test("leaving the removal confirmation removes nothing (#162)", async (env) => {
         "the confirmation names the wrong address: " + JSON.stringify(label),
     );
 
+    // The route back is written by the view, not by index.html, so an empty
+    // paragraph here means the user is confirming with no idea what it
+    // takes to undo. This wallet is an HD one, so it is told about its
+    // recovery phrase.
+    const recovery = await env.page
+        .locator("#delete-address-recovery")
+        .innerText();
+    assert(
+        recovery.includes("delete the whole wallet in Settings") &&
+            recovery.includes("recovery phrase"),
+        "the confirmation does not state the route back: " +
+            JSON.stringify(recovery),
+    );
+
     // "Back" re-renders Home, so a count taken after it is a real
     // measurement of the wallet rather than a stale screen.
     await env.page.click("#btn-delete-address-back");

tests/holders.test.js

@@ -0,0 +1,166 @@
+// Tests for src/shared/holders.js and the balance-list spam gate that reads
+// it (issue #230).
+//
+// The rule these pin down: an explorer that reports no holders_count has told
+// us nothing, and "nothing" must not be recorded as "zero holders".  Zero is
+// the strongest spam signal the wallet has, so handing it out for free turns
+// a missing field into a hidden asset.
+
+jest.mock("../src/shared/log", () => ({
+    log: {
+        debugf: () => {},
+        infof: () => {},
+        warnf: () => {},
+        errorf: () => {},
+    },
+    debugFetch: jest.fn(),
+    setRuntimeDebug: () => {},
+    isDebug: () => false,
+}));
+
+global.fetch = jest.fn(() => {
+    throw new Error("tests must not perform network requests");
+});
+global.chrome = { storage: { local: {} } };
+
+const {
+    LOW_HOLDER_THRESHOLD,
+    parseHoldersCount,
+    isLowHolderCount,
+} = require("../src/shared/holders");
+const { fetchTokenBalances } = require("../src/shared/balances");
+const { debugFetch } = require("../src/shared/log");
+
+const BLOCKSCOUT = "https://eth.blockscout.com/api/v2";
+const HOLDER = "0x66133e8ea0f5d1d612d2502a968757d1048c214a";
+const USDC_CONTRACT = "0xa0b86991c6218b36c1d19d4a2e9eb0ce3606eb48";
+const NOVEL_TOKEN = "0x1111111111111111111111111111111111111111";
+
+describe("parseHoldersCount", () => {
+    test("a reported count parses to that number", () => {
+        expect(parseHoldersCount("3500000")).toBe(3500000);
+        expect(parseHoldersCount(3500000)).toBe(3500000);
+    });
+
+    test('a reported "0" parses to 0, which is not null', () => {
+        expect(parseHoldersCount("0")).toBe(0);
+        expect(parseHoldersCount(0)).toBe(0);
+    });
+
+    test("an omitted, null or empty count is unknown", () => {
+        expect(parseHoldersCount(undefined)).toBeNull();
+        expect(parseHoldersCount(null)).toBeNull();
+        expect(parseHoldersCount("")).toBeNull();
+    });
+
+    test("an unparseable count is unknown rather than zero", () => {
+        expect(parseHoldersCount("many")).toBeNull();
+        expect(parseHoldersCount(NaN)).toBeNull();
+    });
+});
+
+describe("isLowHolderCount", () => {
+    test("the threshold is the documented 1,000 holders", () => {
+        expect(LOW_HOLDER_THRESHOLD).toBe(1000);
+    });
+
+    test("a reported count below the threshold is low", () => {
+        expect(isLowHolderCount(0)).toBe(true);
+        expect(isLowHolderCount(999)).toBe(true);
+    });
+
+    test("a reported count at or above the threshold is not low", () => {
+        expect(isLowHolderCount(1000)).toBe(false);
+        expect(isLowHolderCount(1001)).toBe(false);
+    });
+
+    test("an unknown count is not low", () => {
+        expect(isLowHolderCount(null)).toBe(false);
+        expect(isLowHolderCount(undefined)).toBe(false);
+    });
+});
+
+// fetchTokenBalances applies its own spam gate, which is not the low-holder
+// display filter: it has no setting behind it and decides what the balance
+// list contains at all.  It stays strict on an unknown count — see the
+// comment at the gate — but must stop recording that unknown as zero.
+describe("the balance-list spam gate", () => {
+    function respondWith(items) {
+        debugFetch.mockImplementation(async () => ({
+            ok: true,
+            status: 200,
+            statusText: "OK",
+            json: async () => items,
+        }));
+    }
+
+    function item(overrides = {}) {
+        const { token, ...rest } = overrides;
+        return {
+            value: "12500000",
+            ...rest,
+            token: {
+                type: "ERC-20",
+                address_hash: NOVEL_TOKEN,
+                symbol: "SPAMTKN",
+                name: "Spam Token",
+                decimals: "6",
+                holders_count: "50000",
+                ...token,
+            },
+        };
+    }
+
+    beforeEach(() => {
+        debugFetch.mockReset();
+    });
+
+    test("a token with plenty of reported holders is listed", async () => {
+        respondWith([item()]);
+        const balances = await fetchTokenBalances(HOLDER, BLOCKSCOUT, []);
+        expect(balances).toHaveLength(1);
+        expect(balances[0].holders).toBe(50000);
+    });
+
+    test("a token reporting zero holders is still excluded", async () => {
+        respondWith([item({ token: { holders_count: "0" } })]);
+        expect(await fetchTokenBalances(HOLDER, BLOCKSCOUT, [])).toEqual([]);
+    });
+
+    test("an unknown holder count does not admit an unvouched token", async () => {
+        respondWith([item({ token: { holders_count: null } })]);
+        expect(await fetchTokenBalances(HOLDER, BLOCKSCOUT, [])).toEqual([]);
+    });
+
+    // The path that reaches the send selector and the history filter: a token
+    // the user vouched for by tracking it is listed whatever the explorer
+    // says, and it must carry the unknown count through as null, not as the
+    // zero that would then hide it downstream.
+    test("a tracked token with an unknown count is listed with holders null", async () => {
+        respondWith([item({ token: { holders_count: undefined } })]);
+        const balances = await fetchTokenBalances(HOLDER, BLOCKSCOUT, [
+            { address: NOVEL_TOKEN.toUpperCase() },
+        ]);
+        expect(balances).toHaveLength(1);
+        expect(balances[0].holders).toBeNull();
+    });
+
+    test("a known-list token with an unknown count is listed with holders null", async () => {
+        respondWith([
+            item({
+                token: {
+                    address_hash: USDC_CONTRACT,
+                    symbol: "USDC",
+                    holders_count: null,
+                },
+            }),
+        ]);
+        const balances = await fetchTokenBalances(HOLDER, BLOCKSCOUT, []);
+        expect(balances).toHaveLength(1);
+        expect(balances[0].holders).toBeNull();
+    });
+
+    test("no test in this file performed a network request", () => {
+        expect(global.fetch).not.toHaveBeenCalled();
+    });
+});

tests/manifest.test.js

@@ -0,0 +1,105 @@
+// The shipped Content Security Policy, pinned in both directions.
+//
+// This is the anti-regression check for #182. libsodium decides its
+// backend by trying to compile WebAssembly and catching the failure, so a
+// CSP that refuses WASM demotes the vault to the wasm2js translation —
+// roughly 20x slower per Argon2id derivation — and says so only in a
+// console message nobody reads. Dropping 'wasm-unsafe-eval' from either
+// manifest therefore has to fail a check, not a log line.
+//
+// It is equally a check against loosening. 'wasm-unsafe-eval' is granted
+// deliberately and narrowly (see the backend note in src/shared/vault.js);
+// 'unsafe-eval', 'unsafe-inline' and any remote script source are not, and
+// an exact match on the token set is what keeps the next edit from
+// smuggling one in alongside.
+//
+// build.js copies these files to dist/<target>/manifest.json verbatim, so
+// what is asserted here is what ships.
+
+const fs = require("fs");
+const path = require("path");
+
+const MANIFEST_DIR = path.join(__dirname, "..", "manifest");
+
+const EXPECTED_SCRIPT_SRC = ["'self'", "'wasm-unsafe-eval'"];
+const EXPECTED_OBJECT_SRC = ["'self'"];
+
+const FORBIDDEN_SOURCES = [
+    "'unsafe-eval'",
+    "'unsafe-inline'",
+    "http:",
+    "https:",
+    "data:",
+    "blob:",
+    "*",
+];
+
+function readManifest(name) {
+    return JSON.parse(
+        fs.readFileSync(path.join(MANIFEST_DIR, name + ".json"), "utf8"),
+    );
+}
+
+// "script-src 'self'; object-src 'self'" -> { "script-src": ["'self'"], ... }
+function parseCsp(policy) {
+    const directives = {};
+    for (const part of policy.split(";")) {
+        const tokens = part.trim().split(/\s+/).filter(Boolean);
+        if (tokens.length === 0) continue;
+        directives[tokens[0]] = tokens.slice(1);
+    }
+    return directives;
+}
+
+function assertPolicy(policy) {
+    const directives = parseCsp(policy);
+    expect(Object.keys(directives).sort()).toEqual([
+        "object-src",
+        "script-src",
+    ]);
+    expect(directives["script-src"].slice().sort()).toEqual(
+        EXPECTED_SCRIPT_SRC,
+    );
+    expect(directives["object-src"].slice().sort()).toEqual(
+        EXPECTED_OBJECT_SRC,
+    );
+    for (const source of FORBIDDEN_SOURCES) {
+        expect(directives["script-src"]).not.toContain(source);
+        expect(directives["object-src"]).not.toContain(source);
+    }
+}
+
+describe("shipped Content Security Policy", () => {
+    // MV3 takes an object and applies extension_pages to the popup and the
+    // background service worker, which is where libsodium runs.
+    test("chrome MV3 allows WASM and nothing else beyond 'self'", () => {
+        const csp = readManifest("chrome").content_security_policy;
+        expect(typeof csp).toBe("object");
+        expect(Object.keys(csp)).toEqual(["extension_pages"]);
+        assertPolicy(csp.extension_pages);
+    });
+
+    // MV2 takes the policy as a bare string. Firefox does not require
+    // 'wasm-unsafe-eval' for MV2 today — enforcement is report-only and
+    // Bugzilla 1770909 is still open — so that token is future-proofing
+    // for when it lands, not a mandate, and it stays inside Firefox's MV2
+    // base-CSP ceiling. object-src 'self' is the load-bearing half: a
+    // Firefox before 106 rejects an MV2 policy string that omits
+    // object-src and falls back to its own default, discarding everything
+    // declared here. Same policy as Chrome, different manifest shape.
+    test("firefox MV2 allows WASM and nothing else beyond 'self'", () => {
+        const csp = readManifest("firefox").content_security_policy;
+        expect(typeof csp).toBe("string");
+        assertPolicy(csp);
+    });
+
+    // The two targets share one codebase and one crypto path; a policy
+    // that drifts apart between them means one of the two builds is
+    // running a backend nothing tests.
+    test("both targets ship the same policy", () => {
+        const chrome =
+            readManifest("chrome").content_security_policy.extension_pages;
+        const firefox = readManifest("firefox").content_security_policy;
+        expect(firefox).toBe(chrome);
+    });
+});

tests/sendTokenSelect.test.js

@@ -0,0 +1,123 @@
+// Tests for the token filtering in the Send view's token selector
+// (src/popup/views/send.js).
+//
+// The selector decides which of the user's tokens can be spent at all, so
+// over-filtering here is worse than in the history list: the asset is not
+// merely hidden, it becomes unspendable through the UI.  Issue #230: an
+// explorer that omits holders_count was read as "zero holders" and the token
+// disappeared from this list.
+//
+// renderSendTokenSelect only ever touches getElementById, createElement,
+// innerHTML, value, textContent and appendChild, so a small stub document is
+// enough to drive it; the real DOM behaviour of the view is covered by
+// tests/e2e/run.js.
+
+globalThis.chrome = {
+    storage: { local: { get: async () => ({}), set: async () => {} } },
+};
+
+const { state } = require("../src/shared/state");
+const { renderSendTokenSelect } = require("../src/popup/views/send");
+
+const USDC_CONTRACT = "0xA0b86991c6218b36c1d19D4a2e9Eb0cE3606eB48";
+const NOVEL_TOKEN = "0x1111111111111111111111111111111111111111";
+
+let select;
+
+function installStubDocument() {
+    select = { innerHTML: "", children: [] };
+    select.appendChild = (child) => select.children.push(child);
+    globalThis.document = {
+        getElementById: (id) => (id === "send-token" ? select : null),
+        createElement: () => ({ value: "", textContent: "" }),
+    };
+}
+
+// The symbols offered for sending, excluding the hardcoded ETH option that
+// renderSendTokenSelect writes straight into innerHTML.
+function offeredTokens() {
+    return select.children.map((opt) => opt.value.toLowerCase());
+}
+
+function tokenBalance(overrides) {
+    return {
+        address: NOVEL_TOKEN,
+        symbol: "SPAMTKN",
+        decimals: 18,
+        balance: "12.5",
+        holders: 50000,
+        ...overrides,
+    };
+}
+
+function render(tokenBalances) {
+    installStubDocument();
+    renderSendTokenSelect({ address: "0x" + "a".repeat(40), tokenBalances });
+}
+
+beforeEach(() => {
+    state.fraudContracts = [];
+    state.hideLowHolderTokens = true;
+});
+
+describe("the low-holder rule in the send token selector", () => {
+    test("ETH is always offered", () => {
+        render([]);
+        expect(select.innerHTML).toBe('<option value="ETH">ETH</option>');
+        expect(offeredTokens()).toEqual([]);
+    });
+
+    test("a token with plenty of holders is offered", () => {
+        render([tokenBalance()]);
+        expect(offeredTokens()).toEqual([NOVEL_TOKEN]);
+    });
+
+    test("a token reporting zero holders is withheld", () => {
+        render([tokenBalance({ holders: 0 })]);
+        expect(offeredTokens()).toEqual([]);
+    });
+
+    test("boundary: 999 holders is withheld, 1000 is offered", () => {
+        render([tokenBalance({ holders: 999 })]);
+        expect(offeredTokens()).toEqual([]);
+        render([tokenBalance({ holders: 1000 })]);
+        expect(offeredTokens()).toEqual([NOVEL_TOKEN]);
+    });
+
+    // Issue #230: an unknown holder count must not read as zero.  A token the
+    // user demonstrably holds — it has a balance — cannot be made unspendable
+    // by a field the block explorer failed to report.
+    test("a token whose holder count is unknown is still offered", () => {
+        render([tokenBalance({ holders: null })]);
+        expect(offeredTokens()).toEqual([NOVEL_TOKEN]);
+    });
+
+    test("a token balance carrying no holders field at all is offered", () => {
+        const t = tokenBalance();
+        delete t.holders;
+        render([t]);
+        expect(offeredTokens()).toEqual([NOVEL_TOKEN]);
+    });
+
+    test("the rule is bypassed entirely when the setting is off", () => {
+        state.hideLowHolderTokens = false;
+        render([tokenBalance({ holders: 0 })]);
+        expect(offeredTokens()).toEqual([NOVEL_TOKEN]);
+    });
+});
+
+describe("the other send-selector rules are unaffected", () => {
+    test("a token spoofing a known symbol from a wrong address is withheld", () => {
+        render([
+            tokenBalance({ symbol: "USDC", holders: null }),
+            tokenBalance({ address: USDC_CONTRACT, symbol: "USDC" }),
+        ]);
+        expect(offeredTokens()).toEqual([USDC_CONTRACT.toLowerCase()]);
+    });
+
+    test("a blocklisted fraud contract is withheld even with an unknown count", () => {
+        state.fraudContracts = [NOVEL_TOKEN.toUpperCase()];
+        render([tokenBalance({ holders: null })]);
+        expect(offeredTokens()).toEqual([]);
+    });
+});

tests/transactions.test.js

@@ -1473,6 +1473,65 @@ describe("fetchRecentTransactions merge and dedup", () => {
         expect(result.newFraudContracts).toEqual([FAKE_ETH_CONTRACT]);
     });
 
+    // Regression guards (#230): the explorer's holders_count is optional.  A
+    // missing field means the count is unknown; it does not mean the token
+    // has no holders.  Recording the two as the same number both hides a
+    // legitimate token and makes the `holders !== null` guard in
+    // filterTransactions unreachable for token transfers.
+    describe("an unreported holders_count is unknown, not zero", () => {
+        function spamTransferWithToken(token) {
+            return [
+                {
+                    transaction_hash: "0x" + "9".repeat(64),
+                    block_number: 21000070,
+                    timestamp: TS,
+                    from: { hash: ORDINARY_PEER },
+                    to: { hash: VICTIM },
+                    total: { value: "1500500000", decimals: "6" },
+                    token: token,
+                },
+            ];
+        }
+
+        const OMITTED = {
+            symbol: NOVEL_SPAM_SYMBOL,
+            address_hash: NOVEL_SPAM_CONTRACT,
+        };
+        const NULLED = { ...OMITTED, holders_count: null };
+        const ZERO = { ...OMITTED, holders_count: "0" };
+
+        test("an omitted holders_count parses to null", async () => {
+            respondWith([], spamTransferWithToken(OMITTED));
+            const txs = await fetchRecentTransactions(VICTIM, BLOCKSCOUT);
+            expect(txs[0].holders).toBeNull();
+        });
+
+        test("a null holders_count parses to null", async () => {
+            respondWith([], spamTransferWithToken(NULLED));
+            const txs = await fetchRecentTransactions(VICTIM, BLOCKSCOUT);
+            expect(txs[0].holders).toBeNull();
+        });
+
+        test("the transfer survives the low-holder filter", async () => {
+            respondWith([], spamTransferWithToken(OMITTED));
+            const txs = await fetchRecentTransactions(VICTIM, BLOCKSCOUT);
+            expect(filterTransactions(txs, filters()).transactions).toEqual(
+                txs,
+            );
+        });
+
+        // The regression this fix could cause: a token that genuinely
+        // reports zero holders must keep being filtered.  Unlike the fake
+        // "ETH" fixture above, this symbol is not in the token list, so the
+        // holder count is the only rule that can catch it.
+        test('a reported holders_count of "0" still parses to 0 and is filtered', async () => {
+            respondWith([], spamTransferWithToken(ZERO));
+            const txs = await fetchRecentTransactions(VICTIM, BLOCKSCOUT);
+            expect(txs[0].holders).toBe(0);
+            expect(filterTransactions(txs, filters()).transactions).toEqual([]);
+        });
+    });
+
     test("failed responses yield an empty list rather than throwing", async () => {
         debugFetch.mockImplementation(async () => ({
             ok: false,

tests/txValidation.test.js

@@ -0,0 +1,357 @@
+const { parseEther } = require("ethers");
+const {
+    CODES,
+    FEE_PENDING,
+    FEE_KNOWN,
+    FEE_UNAVAILABLE,
+    feeReserveWei,
+    feeEstimateWei,
+    toFixedPoint,
+    validateTransfer,
+} = require("../src/shared/txValidation");
+
+// A plausible mainnet fee: 21000 gas at 20 gwei.
+const FEE = 21000n * 20000000000n; // 0.00042 ETH
+
+const GWEI = 1000000000n;
+const GAS_LIMIT = 21000n;
+
+describe("toFixedPoint", () => {
+    test("scales human decimals to 18 places", () => {
+        expect(toFixedPoint("1.5")).toBe(parseEther("1.5"));
+        expect(toFixedPoint("0")).toBe(0n);
+    });
+
+    test("rejects values it cannot represent exactly", () => {
+        expect(toFixedPoint("not a number")).toBe(null);
+        expect(toFixedPoint("")).toBe(null);
+        expect(toFixedPoint(null)).toBe(null);
+        // More precision than 18 decimals can hold.
+        expect(toFixedPoint("0.0000000000000000001")).toBe(null);
+    });
+});
+
+describe("validateTransfer, native ETH", () => {
+    const eth = (over) => ({
+        isErc20: false,
+        amount: "0.5",
+        ethBalance: "1.0",
+        feeStatus: FEE_KNOWN,
+        feeWei: FEE,
+        ...over,
+    });
+
+    test("allows a send comfortably within balance", () => {
+        const r = validateTransfer(eth());
+        expect(r).toEqual({ canSend: true, codes: [] });
+    });
+
+    test("blocks a send whose amount plus fee exceeds the balance", () => {
+        // The whole balance: passes an amount-only check, fails once the fee
+        // is counted. This is the bug this module exists to prevent.
+        const r = validateTransfer(eth({ amount: "1.0", ethBalance: "1.0" }));
+        expect(r.canSend).toBe(false);
+        expect(r.codes).toEqual([CODES.INSUFFICIENT_ETH_WITH_FEE]);
+    });
+
+    test("blocks a send left short by less than one fee", () => {
+        const balance = "1.0";
+        // One wei less headroom than the fee needs.
+        const amount = "0.99958000000000001"; // 1.0 - 0.00042 + 1e-17
+        const r = validateTransfer(eth({ amount, ethBalance: balance }));
+        expect(r.codes).toEqual([CODES.INSUFFICIENT_ETH_WITH_FEE]);
+    });
+
+    test("allows a send that leaves exactly the fee behind", () => {
+        const r = validateTransfer(
+            eth({ amount: "0.99958", ethBalance: "1.0" }),
+        );
+        expect(r).toEqual({ canSend: true, codes: [] });
+    });
+
+    test("reports plain insufficient balance when the amount alone is too big", () => {
+        const r = validateTransfer(eth({ amount: "2.0", ethBalance: "1.0" }));
+        expect(r.codes).toEqual([CODES.INSUFFICIENT_ETH]);
+    });
+
+    test("blocks while the fee estimate is still pending", () => {
+        const r = validateTransfer(
+            eth({ feeStatus: FEE_PENDING, feeWei: null }),
+        );
+        expect(r.canSend).toBe(false);
+        expect(r.codes).toEqual([CODES.FEE_PENDING]);
+    });
+
+    test("blocks when the fee estimate failed, without assuming zero", () => {
+        const r = validateTransfer(
+            eth({
+                amount: "1.0",
+                ethBalance: "1.0",
+                feeStatus: FEE_UNAVAILABLE,
+                feeWei: null,
+            }),
+        );
+        expect(r.canSend).toBe(false);
+        expect(r.codes).toEqual([CODES.FEE_UNAVAILABLE]);
+        // A zero fee would have let this exact transfer through.
+        expect(
+            validateTransfer(
+                eth({ amount: "1.0", ethBalance: "1.0", feeWei: 0n }),
+            ).canSend,
+        ).toBe(true);
+    });
+
+    test("still reports an over-balance amount before the estimate lands", () => {
+        const r = validateTransfer(
+            eth({
+                amount: "2.0",
+                ethBalance: "1.0",
+                feeStatus: FEE_PENDING,
+                feeWei: null,
+            }),
+        );
+        expect(r.codes).toEqual([CODES.INSUFFICIENT_ETH, CODES.FEE_PENDING]);
+    });
+
+    test("rejects an amount it cannot do exact arithmetic on", () => {
+        const r = validateTransfer(eth({ amount: "abc" }));
+        expect(r.canSend).toBe(false);
+        expect(r.codes).toEqual([CODES.AMOUNT_INVALID]);
+    });
+
+    test("rejects a negative amount", () => {
+        // A negative amount parses to a perfectly good bigint, so neither
+        // balance comparison can fire: both are trivially false against it.
+        // Left unblocked it clears the screen and then dies at encode time.
+        const r = validateTransfer(
+            eth({ amount: "-1", ethBalance: "1.0", feeWei: 861000000000000n }),
+        );
+        expect(r).toEqual({ canSend: false, codes: [CODES.AMOUNT_INVALID] });
+        expect(
+            validateTransfer(eth({ amount: "-0.000000000000000001" })),
+        ).toEqual({ canSend: false, codes: [CODES.AMOUNT_INVALID] });
+    });
+
+    test("treats a missing balance as zero, not as unlimited", () => {
+        const r = validateTransfer(eth({ ethBalance: undefined }));
+        expect(r.codes).toEqual([CODES.INSUFFICIENT_ETH]);
+    });
+});
+
+describe("validateTransfer, ERC-20", () => {
+    const erc20 = (over) => ({
+        isErc20: true,
+        amount: "100.0",
+        tokenBalance: "250.0",
+        ethBalance: "1.0",
+        feeStatus: FEE_KNOWN,
+        feeWei: FEE,
+        ...over,
+    });
+
+    test("allows a transfer with tokens to spend and ETH for the fee", () => {
+        expect(validateTransfer(erc20())).toEqual({ canSend: true, codes: [] });
+    });
+
+    test("checks the token amount against the token balance", () => {
+        const r = validateTransfer(erc20({ amount: "250.000001" }));
+        expect(r.codes).toEqual([CODES.INSUFFICIENT_TOKEN]);
+    });
+
+    test("does not charge the fee against the token balance", () => {
+        // The full token balance is sendable: the fee is paid in ETH.
+        expect(validateTransfer(erc20({ amount: "250.0" })).canSend).toBe(true);
+    });
+
+    test("blocks when the ETH balance does not cover the fee", () => {
+        const r = validateTransfer(erc20({ ethBalance: "0.0001" }));
+        expect(r.canSend).toBe(false);
+        expect(r.codes).toEqual([CODES.INSUFFICIENT_ETH_FOR_FEE]);
+    });
+
+    test("allows a fee exactly equal to the ETH balance", () => {
+        const r = validateTransfer(erc20({ ethBalance: "0.00042" }));
+        expect(r).toEqual({ canSend: true, codes: [] });
+    });
+
+    test("reports both shortfalls when tokens and ETH are both short", () => {
+        const r = validateTransfer(
+            erc20({ amount: "300.0", ethBalance: "0.0" }),
+        );
+        expect(r.codes).toEqual([
+            CODES.INSUFFICIENT_TOKEN,
+            CODES.INSUFFICIENT_ETH_FOR_FEE,
+        ]);
+    });
+
+    test("blocks while the fee estimate is pending or failed", () => {
+        expect(
+            validateTransfer(erc20({ feeStatus: FEE_PENDING, feeWei: null }))
+                .codes,
+        ).toEqual([CODES.FEE_PENDING]);
+        expect(
+            validateTransfer(
+                erc20({ feeStatus: FEE_UNAVAILABLE, feeWei: null }),
+            ).codes,
+        ).toEqual([CODES.FEE_UNAVAILABLE]);
+    });
+
+    test("rejects a negative token amount", () => {
+        const r = validateTransfer(
+            erc20({ amount: "-0.5", feeWei: 861000000000000n }),
+        );
+        expect(r).toEqual({ canSend: false, codes: [CODES.AMOUNT_INVALID] });
+    });
+
+    test("treats a missing token balance as zero", () => {
+        const r = validateTransfer(erc20({ tokenBalance: undefined }));
+        expect(r.codes).toEqual([CODES.INSUFFICIENT_TOKEN]);
+    });
+});
+
+// The reserve a node requires, not the fee the transaction is expected to
+// actually cost. An unpinned send goes out as type-2, and the node checks it
+// against maxFeePerGas; reserving gasPrice lets a transaction the node will
+// reject pass the gate.
+describe("feeReserveWei", () => {
+    // baseFee 20 gwei, tip 1 gwei: eth_gasPrice reports ~21 gwei, while
+    // ethers populates maxFeePerGas as baseFee * 2 + tip = 41 gwei.
+    const type2 = {
+        gasPrice: 21n * GWEI,
+        maxFeePerGas: 41n * GWEI,
+        maxPriorityFeePerGas: 1n * GWEI,
+    };
+
+    test("reserves gasLimit * maxFeePerGas, not gasLimit * gasPrice", () => {
+        expect(feeReserveWei(GAS_LIMIT, type2)).toBe(GAS_LIMIT * 41n * GWEI);
+        expect(feeReserveWei(GAS_LIMIT, type2)).toBe(861000000000000n);
+        // The number the node would not have accepted.
+        expect(feeReserveWei(GAS_LIMIT, type2)).not.toBe(441000000000000n);
+    });
+
+    test("gates out a send the type-2 reserve cannot fund", () => {
+        // Exactly fundable against a gasPrice reserve (0.999559 + 0.000441 is
+        // the whole balance to the wei), and short against the reserve the
+        // node will actually require.
+        const send = {
+            isErc20: false,
+            amount: "0.999559",
+            ethBalance: "1.0",
+            feeStatus: FEE_KNOWN,
+        };
+        expect(
+            validateTransfer({
+                ...send,
+                feeWei: GAS_LIMIT * type2.gasPrice,
+            }).canSend,
+        ).toBe(true);
+        const r = validateTransfer({
+            ...send,
+            feeWei: feeReserveWei(GAS_LIMIT, type2),
+        });
+        expect(r.canSend).toBe(false);
+        expect(r.codes).toEqual([CODES.INSUFFICIENT_ETH_WITH_FEE]);
+    });
+
+    test("falls back to gasPrice on a network with no type-2 pricing", () => {
+        const legacy = { gasPrice: 21n * GWEI, maxFeePerGas: null };
+        expect(feeReserveWei(GAS_LIMIT, legacy)).toBe(GAS_LIMIT * 21n * GWEI);
+    });
+
+    test("returns null when no usable price or gas limit is available", () => {
+        expect(feeReserveWei(GAS_LIMIT, { gasPrice: null })).toBe(null);
+        expect(feeReserveWei(GAS_LIMIT, {})).toBe(null);
+        expect(feeReserveWei(GAS_LIMIT, null)).toBe(null);
+        expect(feeReserveWei(21000, type2)).toBe(null);
+    });
+});
+
+// The display counterpart of the reserve: what the transaction is expected to
+// cost. Shown alongside the reserve so the screen neither contradicts the gate
+// nor quotes the user roughly double what they will pay.
+describe("feeEstimateWei", () => {
+    const type2 = {
+        gasPrice: 21n * GWEI,
+        maxFeePerGas: 41n * GWEI,
+        maxPriorityFeePerGas: 1n * GWEI,
+    };
+
+    test("estimates gasLimit * gasPrice, below the reserve", () => {
+        expect(feeEstimateWei(GAS_LIMIT, type2)).toBe(441000000000000n);
+        expect(feeReserveWei(GAS_LIMIT, type2)).toBe(861000000000000n);
+        expect(feeEstimateWei(GAS_LIMIT, type2)).toBeLessThan(
+            feeReserveWei(GAS_LIMIT, type2),
+        );
+    });
+
+    test("equals the reserve when the network has no type-2 pricing", () => {
+        const legacy = { gasPrice: 21n * GWEI, maxFeePerGas: null };
+        expect(feeEstimateWei(GAS_LIMIT, legacy)).toBe(
+            feeReserveWei(GAS_LIMIT, legacy),
+        );
+    });
+
+    test("falls back to maxFeePerGas when there is no gasPrice", () => {
+        const noLegacy = { gasPrice: null, maxFeePerGas: 41n * GWEI };
+        expect(feeEstimateWei(GAS_LIMIT, noLegacy)).toBe(
+            feeReserveWei(GAS_LIMIT, noLegacy),
+        );
+    });
+
+    test("returns null on the same unusable inputs as the reserve", () => {
+        expect(feeEstimateWei(GAS_LIMIT, {})).toBe(null);
+        expect(feeEstimateWei(GAS_LIMIT, null)).toBe(null);
+        expect(feeEstimateWei(GAS_LIMIT, { gasPrice: -1n })).toBe(null);
+        expect(feeEstimateWei(21000, type2)).toBe(null);
+    });
+});
+
+// Everything that is not a usable fee blocks exactly as FEE_UNAVAILABLE does.
+// Each of these previously returned { canSend: true, codes: [] } — counting no
+// fee at all, on a full-balance send, in the direction that lets money out.
+describe("validateTransfer, unusable fee input fails closed", () => {
+    const fullBalanceSend = (over) => ({
+        isErc20: false,
+        amount: "1.0",
+        ethBalance: "1.0",
+        ...over,
+    });
+
+    test("blocks a null fee claiming to be known", () => {
+        const r = validateTransfer(
+            fullBalanceSend({ feeStatus: FEE_KNOWN, feeWei: null }),
+        );
+        expect(r).toEqual({ canSend: false, codes: [CODES.FEE_UNAVAILABLE] });
+    });
+
+    test("blocks a known fee that is a number rather than a bigint", () => {
+        const r = validateTransfer(
+            fullBalanceSend({ feeStatus: FEE_KNOWN, feeWei: 420000000000000 }),
+        );
+        expect(r).toEqual({ canSend: false, codes: [CODES.FEE_UNAVAILABLE] });
+    });
+
+    test("blocks an unrecognised fee status", () => {
+        const r = validateTransfer(fullBalanceSend({ feeStatus: "bogus" }));
+        expect(r).toEqual({ canSend: false, codes: [CODES.FEE_UNAVAILABLE] });
+    });
+
+    test("blocks a negative fee", () => {
+        const r = validateTransfer(
+            fullBalanceSend({ feeStatus: FEE_KNOWN, feeWei: -1n }),
+        );
+        expect(r).toEqual({ canSend: false, codes: [CODES.FEE_UNAVAILABLE] });
+    });
+
+    test("blocks an ERC-20 transfer on an unusable fee too", () => {
+        const r = validateTransfer({
+            isErc20: true,
+            amount: "100.0",
+            tokenBalance: "250.0",
+            ethBalance: "1.0",
+            feeStatus: FEE_KNOWN,
+            feeWei: null,
+        });
+        expect(r).toEqual({ canSend: false, codes: [CODES.FEE_UNAVAILABLE] });
+    });
+});

tests/vaultBackend.test.js

@@ -0,0 +1,52 @@
+// The unit tests must exercise the libsodium backend that actually ships
+// (#182). Before this, they could not: node compiles WebAssembly happily,
+// the extension CSP refused it, and so the browser silently ran the
+// wasm2js translation while every test ran the WASM build.
+//
+// With 'wasm-unsafe-eval' in both manifests the two agree, and these tests
+// hold that agreement in place from the node side. tests/manifest.test.js
+// holds up the CSP end of it, and the end-to-end suite observes the real
+// popup.
+
+const { cryptoBackend } = require("../src/shared/vault");
+
+// The module libsodium-wrappers-sumo itself requires and drives. Not a new
+// dependency: it is inspected here, never used to perform crypto, because
+// it is the only thing that can say which backend is loaded.
+const SODIUM_CORE = "libsodium-sumo";
+
+describe("libsodium backend", () => {
+    test("this realm compiles WebAssembly, so the tests run the WASM build", async () => {
+        await expect(cryptoBackend()).resolves.toBe("wasm");
+    });
+
+    test("libsodium did not swap in the wasm2js fallback", async () => {
+        const core = require(SODIUM_CORE);
+        await require("libsodium-wrappers-sumo").ready;
+        // useBackupModule is the entry point to the fallback; taking it
+        // replaces the module's exports with the translation's, and the
+        // entry point goes with them. Still present after ready means the
+        // WASM module is the one in place. The test below is what keeps
+        // that inference honest.
+        expect(typeof core.useBackupModule).toBe("function");
+    });
+
+    // Deliberately last, and deliberately destructive: it takes the
+    // fallback, which replaces the loaded module for the rest of this
+    // file. Jest gives each test file its own module registry, so nothing
+    // outside sees it.
+    //
+    // Without this, the check above would be a claim about libsodium's
+    // internals with nothing holding it to account: if a future version
+    // kept useBackupModule on the fallback module too, the marker would
+    // quietly become true in both backends and the test would pass while
+    // measuring nothing. Forcing the fallback and watching the marker
+    // disappear is what makes its presence mean something.
+    test("the fallback marker distinguishes the two backends", async () => {
+        const core = require(SODIUM_CORE);
+        await require("libsodium-wrappers-sumo").ready;
+        expect(typeof core.useBackupModule).toBe("function");
+        await core.useBackupModule();
+        expect(typeof core.useBackupModule).toBe("undefined");
+    });
+});