[carloszanella]

Business logic

Feature

fynd-nexus can now run the Tycho client for its chain and keep fynd's market data and derived data (spot prices, pool depths, and token prices) up to date without worker pools. Nothing reads the market yet; it provides the foundation for serving derived data and for the component health monitor (#694).

Business decisions

• The market runs when --tycho-url is set. It then requires --rpc-url, which FyndBuilder uses to read gas prices. It is configured through --tycho-api-key, --tycho-use-tls (default: true), and --min-tvl (default: the chain's low TVL threshold).
• It tracks every on-chain protocol system that Tycho serves for the chain above the TVL floor, excluding those on the default blocklist.
• The protocol list is fetched from Tycho before the HTTP server binds, so an incorrect Tycho URL causes startup to fail.
• The market has 15 minutes to receive its first block and compute its derived data. After that, if the Tycho feed ends, the service stops with an error so the orchestrator restarts it.
• Passing --venues with no value runs no venue, allowing a deployment to run the market alone. The service refuses to start if it has neither a venue nor the market.

Design

• fynd-core: FyndBuilder::build_market starts the Tycho feed, market data, and derived data without worker pools and returns a MarketFeed. Market setup was separated from solver assembly so both paths share it.
• fynd-nexus: the new market module contains MarketArgs and launch_market. launch_market returns a LaunchedMarket that holds a shared Arc<MarketFeed> and the task that watches the feed. fynd-nexus now depends on fynd-rpc for the protocol list.

For the reviewer

• Most of the logic is in fynd-core/src/solver.rs (build_market and the shared market setup) and fynd-nexus/src/market/market_launch.rs.
• The MarketFeed tasks are never shut down; the process exits when the feed ends.
• No test starts a real market against Tycho.
  🤖 Generated with Claude Code

[github-actions]

Breaking API Changes Detected

This PR introduces breaking API changes, but the PR title does not declare them.
Either fix the breaking changes, or declare them:

• Append ! to the PR title type (e.g. feat!: ...) and make sure a !-marked commit
  lands on main — release-plz bumps the minor version for breaking changes on 0.x.x.

semver-checks output

Checking fynd-bench-harness v0.122.0 -> v0.122.0 (no change; assume minor)
     Checked [   0.043s] 196 checks: 196 pass, 58 skip
     Summary no semver update required
    Finished [   0.093s] fynd-bench-harness
    Checking fynd-core v0.122.0 -> v0.122.0 (no change; assume minor)
     Checked [   0.909s] 196 checks: 196 pass, 58 skip
     Summary no semver update required
    Finished [   1.551s] fynd-core
    Checking fynd-test-fixtures v0.122.0 -> v0.122.0 (no change; assume minor)
     Checked [   0.063s] 196 checks: 196 pass, 58 skip
     Summary no semver update required
    Finished [   0.089s] fynd-test-fixtures
    Checking fynd-rpc v0.122.0 -> v0.122.0 (no change; assume minor)
     Checked [   0.078s] 196 checks: 196 pass, 58 skip
     Summary no semver update required
    Finished [   0.125s] fynd-rpc
    Checking fynd-rpc-types v0.122.0 -> v0.122.0 (no change; assume minor)
     Checked [   0.104s] 196 checks: 196 pass, 58 skip
     Summary no semver update required
    Finished [   0.155s] fynd-rpc-types
    Checking fynd-nexus v0.122.0 -> v0.122.0 (no change; assume minor)
     Checked [   0.058s] 196 checks: 195 pass, 1 fail, 0 warn, 58 skip

--- failure constructible_struct_adds_field: struct exhaustively constructible through public API adds field ---

Description:
A pub struct that could be exhaustively constructed with a literal using only public API has a new pub field, breaking existing exhaustive literals.
        ref: https://doc.rust-lang.org/reference/expressions/struct-expr.html
       impl: https://github.com/obi1kenobi/cargo-semver-checks/tree/v0.50.0/src/lints/constructible_struct_adds_field.ron

Failed in:
  field Cli.market in fynd-nexus/src/cli.rs:42

     Summary semver requires new major version: 1 major and 0 minor checks failed
    Finished [   0.091s] fynd-nexus
    Checking fynd-client v0.122.0 -> v0.122.0 (no change; assume minor)
     Checked [   0.122s] 196 checks: 196 pass, 58 skip
     Summary no semver update required
    Finished [   0.198s] fynd-client
    Checking fynd-tools-common v0.122.0 -> v0.122.0 (no change; assume minor)
     Checked [   0.053s] 196 checks: 196 pass, 58 skip
     Summary no semver update required
    Finished [   0.078s] fynd-tools-common