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docs(swaps): add EVM network integration skills (#66)
## Description Add two reusable skills for adding a new EVM network to MetaMask Swaps/Bridge: - a Core skill for registering the network in `@metamask/bridge-controller`; - a Mobile skill for consuming the released controller support and wiring the unified Swaps/Bridge flow. The workflows cover authoritative chain/token metadata, hex/decimal/CAIP representations, allowlists, default tokens, stablecoin slippage, dependency release coordination, Bridge API readiness, `bridgeConfigV2` rollout, testing, and manual verification. The Swaps domain description now includes both EVM and non-EVM network integration. Reference implementations: - [MetaMask/core#9007](MetaMask/core#9007) - [MetaMask/core#9459](MetaMask/core#9459) - [MetaMask/metamask-mobile#31413](MetaMask/metamask-mobile#31413) - [MetaMask/metamask-mobile#33110](MetaMask/metamask-mobile#33110) ## Type of Change - [x] New skill - [ ] Skill improvement/update - [ ] Bug fix - [x] Documentation update - [ ] Other (please describe): ## Skill Details (if adding a new skill) **Provider Name:** MetaMask **Skill Name:** `add-evm-network-bridge-controller`, `add-evm-network-mobile` **Brief Description:** Repeatable Core and Mobile workflows for adding an EVM network to the unified Swaps/Bridge experience. ## Checklist - [x] I have read the [CONTRIBUTING.md](../CONTRIBUTING.md) guidelines - [x] My skill follows the [SKILL_TEMPLATE.md](.github/SKILL_TEMPLATE.md) format - [x] I have tested this skill with an AI agent - [x] My skill does not contain any secrets, private keys, or sensitive data - [x] I have added appropriate documentation - [x] My changes do not break existing skills ## Testing - `node --test test/*.test.mjs` — 36 tests passed. - Installed the skills into isolated Core and Mobile targets with `tools/install --domain swaps`; each target received only its matching repo overlay. - Verified discovery with `node bin/metamask-skills.mjs list --repo ... --domain swaps --json`. - Forward-tested both skills with independent AI-agent tasks, including missing rollout/API metadata and additive Core changes without existing focused tests. - `git diff --check` passed. The standalone `quick_validate.py` helper could not run because its Python environment lacks PyYAML; repository-native discovery and installer validation passed. ## Additional Context Core support is the hard controller allowlist layer. Mobile launch readiness also requires Bridge API route support and approved `bridgeConfigV2` configuration; the Mobile skill distinguishes those launch gaps from code prerequisites.
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‎README.md‎

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| `performance` | MM product eng | React rendering, hooks, state perf |
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| `perps` | MM product eng | Perps feature dev + review |
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| `pr-workflow` | MM product eng | PR title, description, changelog |
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| `swaps` | MM product eng | Non-EVM swap integration |
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| `swaps` | MM product eng | EVM and non-EVM network integration |
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| `testing` | MM product eng | E2E, unit, visual, perf testing |
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| `ui` | MM product eng | Component development |
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‎domains/swaps/skills/add-evm-network-bridge-controller/repos/core.md‎

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---
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repo: core
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parent: add-evm-network-bridge-controller
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---
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# Add an EVM Network to Bridge Controller
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Add the chain as an additive public contract in `packages/bridge-controller`.
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Do not change quote, transaction, or controller behavior unless the task
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explicitly requires it.
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## Gather authoritative inputs
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Before editing, confirm these implementation inputs:
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- canonical network name and the uppercase TypeScript identifier;
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- decimal chain ID, lowercase `0x` chain ID, and `eip155:<decimal>` CAIP ID;
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- user-facing display name and desired picker rank;
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- native gas token symbol, name, decimals, and representation used by Bridge;
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- whether the zero address represents the native asset for this chain;
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- whether a nonstandard native symbol needs a `SYMBOL_TO_SLIP44_MAP` entry.
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Also identify the downstream Mobile and Extension rollout owners and intended
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package release when known. Missing handoff ownership or release timing does
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not block the additive Core implementation; record it as a remaining gap.
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Derive the hex and CAIP forms from the decimal chain ID and verify the round
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trip. Use authoritative network/token data; do not copy token decimals or an
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address from another network merely because its integration is structurally
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similar. Stop and report missing product or token metadata rather than inventing
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it. Picker rank and native-token representation are implementation inputs;
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downstream scheduling is not.
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## Review reference implementations
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Read the current files before editing because names and types evolve. Compare:
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- [MetaMask/core#9007 — ARC](https://github.com/MetaMask/core/pull/9007),
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including its non-ETH native/default token.
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- [MetaMask/core#9459 — Robinhood Chain](https://github.com/MetaMask/core/pull/9459),
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including an ETH-native chain.
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Use the newest adjacent EVM entry in each target file as the formatting and
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ordering reference.
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## Implement every registration point
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1. In `packages/bridge-controller/src/constants/chains.ts`:
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- add the lowercase hex value to `CHAIN_IDS`;
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- add a display-name constant;
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- add the chain to `NETWORK_TO_NAME_MAP`.
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2. In `packages/bridge-controller/src/constants/bridge.ts`:
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- add the hex chain ID to `ALLOWED_BRIDGE_CHAIN_IDS`;
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- add `{ chainId: 'eip155:<decimal>', name: '<display name>' }` to
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`DEFAULT_CHAIN_RANKING` at the intended picker position.
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3. In `packages/bridge-controller/src/constants/tokens.ts`:
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- register the native currency symbol if the current file maintains a
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currency-symbol map;
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- define a dedicated swaps token object and add it to
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`SWAPS_CHAINID_DEFAULT_TOKEN_MAP`;
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- reuse the existing ETH token metadata for an ETH-native chain;
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- for a non-ETH native asset, provide the exact symbol, name, address,
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decimals, and icon behavior expected by consumers;
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- update `SYMBOL_TO_SLIP44_MAP` only when the symbol is new and a valid
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asset identifier is known.
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4. In `packages/bridge-controller/src/types.ts`, add the decimal member to the
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public `ChainId` enum.
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5. Add an `Unreleased` entry to
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`packages/bridge-controller/CHANGELOG.md` and link the PR when its number is
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available.
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Preserve the three representations deliberately: `CHAIN_IDS` and allowlists
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use hex, `ChainId` uses decimal, and rankings use CAIP IDs. Search for the
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identifier, decimal ID, hex ID, and CAIP ID after editing to catch omissions or
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collisions.
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## Validate the package contract
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Use existing focused tests when the package already covers the changed maps.
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For each invariant below, either cite an existing or new assertion or record a
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static inspection backed by the package build and typecheck:
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- the chain is in `ALLOWED_BRIDGE_CHAIN_IDS`;
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- its default ranking uses the correct CAIP ID;
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- `NETWORK_TO_NAME_MAP` resolves its display name;
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- `SWAPS_CHAINID_DEFAULT_TOKEN_MAP` resolves correct token metadata;
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- the public enum value equals the decimal chain ID.
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Do not create a new low-value suite solely to restate additive constant entries.
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Add tests when an established seam exists or behavior, validation, or public
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serialization changes.
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Run the checks supported by the checkout:
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```bash
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yarn workspace @metamask/bridge-controller run test
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yarn workspace @metamask/bridge-controller run build
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yarn workspace @metamask/bridge-controller run changelog:validate
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yarn build
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yarn lint:misc:check
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```
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If invoking Jest directly, include `--collectCoverage=false`. Report unavailable
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or unrelated failing checks instead of masking them.
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## Hand off downstream rollout
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State that Core support is only the hard allowlist layer. Mobile and Extension
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must consume a released `@metamask/bridge-controller` version and their remote
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`bridgeConfigV2.chainRanking` must include the CAIP chain ID before the network
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can surface. Report the package release requirement, default token decision,
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tests run, and any downstream gaps.

‎domains/swaps/skills/add-evm-network-bridge-controller/skill.md‎

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---
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name: add-evm-network-bridge-controller
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description: >-
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Add a new EVM network to the @metamask/bridge-controller package in the
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MetaMask/core monorepo. Use when a task asks to register an EVM chain for
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Swaps or Bridge, extend ALLOWED_BRIDGE_CHAIN_IDS or DEFAULT_CHAIN_RANKING,
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add bridge chain constants and display names, define the chain's default
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swaps token, or expose a new bridge ChainId enum member.
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---

‎domains/swaps/skills/add-evm-network-mobile/repos/metamask-mobile.md‎

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---
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repo: metamask-mobile
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parent: add-evm-network-mobile
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---
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# Add an EVM Network to Mobile Swaps and Bridge
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Wire only the unified Swaps/Bridge flow. Do not modify legacy swaps or wrapping
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logic unless the task explicitly includes them.
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## Separate implementation and launch readiness
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Confirm these code inputs before implementation:
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- Mobile already exposes the chain through its current network constants,
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including the canonical `NETWORK_CHAIN_ID` entry and network metadata.
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- A released `@metamask/bridge-controller` version contains the chain in
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`CHAIN_IDS`, `ChainId`, and `ALLOWED_BRIDGE_CHAIN_IDS`.
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- The default destination token address, symbol, name, decimals, and icon URL
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are authoritative.
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- Stablecoin addresses are known if stable-to-stable swaps should receive the
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reduced default slippage.
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Stop and report a missing code input rather than inventing metadata or leaving
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a partial implementation.
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Track these separate launch requirements without blocking an otherwise valid
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Mobile code change:
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- the Bridge API supports at least one approved source/destination route and
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token pair for the chain;
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- the `bridgeConfigV2` owner has the decimal/CAIP chain ID, display name,
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ranking position, activation direction, rollout percentage, and minimum
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Mobile version.
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The network picker intersects two gates: the controller hard allowlist and the
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remote `bridgeConfigV2.chainRanking`. Missing API or remote configuration blocks
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claiming the network is launch-ready, not preparing the client PR. Continue with
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the code when its inputs are complete and report every launch gap explicitly.
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## Review reference implementations and live shapes
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Inspect current types and neighboring network entries before editing; the
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default-token map has changed shape over time. Use these PRs as behavioral
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references, not as patches to replay:
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- [MetaMask/metamask-mobile#31413 — ARC](https://github.com/MetaMask/metamask-mobile/pull/31413),
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covering the default destination token, stablecoin slippage, and network
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label.
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- [MetaMask/metamask-mobile#33110 — Robinhood Chain](https://github.com/MetaMask/metamask-mobile/pull/33110),
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covering the bridge-controller upgrade, default token, and label. Treat
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dependency-driven cleanup in that PR as incidental rather than required.
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## Implement the Mobile layer
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1. Verify the installed `@metamask/bridge-controller` exports the chain. If it
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does not, update `package.json` to the first compatible released version and
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regenerate `yarn.lock` with the repository's package-manager workflow.
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Avoid unrelated dependency upgrades where the lockfile permits it.
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2. In
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`app/components/UI/Bridge/constants/default-swap-dest-tokens.ts`, add the
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chain's default destination token. Follow the current value shape exactly
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(for example, a token entry may be nested under `'*'`). Include the canonical
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address, decimals, image URL, and chain ID. Checksum source addresses where
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current entries do so; use the lowercase address in the token-icon URL.
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3. In `app/constants/bridge.ts`, add the concise UI label to
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`NETWORK_TO_SHORT_NETWORK_NAME_MAP` using the existing Mobile chain
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constant.
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4. Find the current stablecoin registry used by default-slippage logic. If the
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chain supports reduced stablecoin slippage, add every approved stablecoin
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address using the registry's existing normalization and update its tests.
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Do not treat the default destination token as a stablecoin without product
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confirmation.
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5. Compile after a controller upgrade. Resolve only type errors or stale
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suppressions directly caused by the new dependency version. Keep unrelated
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fee, quote, and behavior cleanup out of the network integration.
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Search for the chain identifier, decimal ID, hex ID, and CAIP ID after editing.
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Confirm there is no second Mobile bridge label, token map, stablecoin registry,
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or test fixture that also requires the network.
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## Specify the remote rollout
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Record the required `bridgeConfigV2` change even when LaunchDarkly is outside
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the repository:
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- add `chains["<decimalChainId>"]` with the approved source/destination and
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unified-button activation fields;
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- add `{ "chainId": "eip155:<decimal>", "name": "<display name>" }` to
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`chainRanking` at the intended position;
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- add approved assets to `topAssets`, `batchSellDestStablecoins`, and the
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top-level `stablecoins` list only when the product configuration requires
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them;
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- define percentage rollout and `minimumVersion` gating.
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Do not claim the network is available in the picker until both controller and
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remote gates are satisfied.
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## Test and manually verify
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Use established test seams for behavior that the integration changes. Add or
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update focused tests for the default token, label, or stablecoin registry only
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when those areas already have meaningful coverage. Verify through tests or
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documented static inspection that:
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- the default token resolves for the new destination chain;
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- the short network label resolves;
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- approved stablecoin pairs receive the intended default slippage;
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- the existing bridge selector tests still enforce exclusion when either
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allowlist layer is absent and inclusion when both layers contain a chain.
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Do not add a per-network copy of generic allowlist-intersection tests unless the
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selector behavior itself changes. Run the existing bridge slice tests instead.
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Run the narrowest relevant Jest suites with `--collectCoverage=false`, then the
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repository's applicable typecheck and lint commands. Review lockfile changes
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when the controller dependency changes.
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Manually exercise both directions supported by the flag:
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1. select the new network as a destination and confirm the intended default
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token;
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2. request a real quote for an approved token pair;
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3. select it as a source if source activation is enabled;
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4. confirm the display label, token icon, decimals, balance, fee, and slippage;
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5. repeat on iOS and Android when preparing the PR for review.
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Finish with a prerequisites result, files changed, remote flag changes, tests
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run, manual-test evidence, dependency/release status, and remaining gaps.

‎domains/swaps/skills/add-evm-network-mobile/skill.md‎

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---
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name: add-evm-network-mobile
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description: >-
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Add a new EVM network to the unified Swaps and Bridge flow in
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MetaMask/metamask-mobile. Use when a task asks to consume a newly supported
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bridge-controller chain, add a Mobile bridge network label, configure its
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default destination token or stablecoin slippage, update bridgeConfigV2
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rollout requirements, or validate that a new EVM network appears in Mobile's
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source and destination network pickers.
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---

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