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Cargo Feature Flags

Generated from Cargo.toml files as of 2026-03-24. Run grep -r '^\[features\]' crates/*/Cargo.toml to verify.

Source of truth: Crate Cargo.toml manifests. This page is a curated snapshot. To verify against the actual source:

# List all feature flags across the workspace
cargo metadata --format-version=1 --no-deps \
  | jq -r '.packages[] | select(.manifest_path | contains("crates/")) | "\(.name): \(.features | keys | join(", "))"'

This document lists all Cargo feature flags across the Echo workspace. For runtime configuration, see configuration-reference.md.

warp-core

The simulation engine. Most flags live here.

Feature Default Description
det_float no CI lane marker: float32-backed scalar backend (F32Scalar). Does not change behavior; used to tag test runs.
det_fixed no CI lane marker: fixed-point Q32.32 backend (DFix64). Experimental, test-only.
delta_validate no Enables extra validation for delta operations during rewrite execution.
golden_prng no Regression check for PRNG sequences. Off by default to avoid freezing algorithm choices. Test-only.
trig_audit_print no Extra diagnostic printing in deterministic trig tests. Test-only.
footprint_enforce_release no Enforce footprint independence checks in release builds (normally debug-only). Use in CI/staging. Mutually exclusive with unsafe_graph.
unsafe_graph no DANGER: Disables footprint enforcement entirely, even in debug. Removes all determinism safety checks. Mutually exclusive with footprint_enforce_release.
serde no Serde support for serializable wrappers. Only use with deterministic CBOR. JSON is non-deterministic and banned in warp-core.

Scalar Backend Lanes

The det_float feature is a CI orchestration marker — it tags a test lane but does not change runtime behavior. The det_fixed feature, however, is a behavioral switch: it selects the fixed-point Q32.32 math backend (DFix64), which genuinely changes runtime arithmetic. Both allow the CI matrix to run separate test lanes for each scalar backend:

# Float lane (default behavior)
cargo test -p warp-core --features det_float

# Fixed-point lane (experimental)
cargo test -p warp-core --features det_fixed

Footprint Safety Levels

Footprint enforcement is a determinism safety mechanism that validates rewrite independence during scheduling. Three modes exist:

Mode When Flag
Enforced (debug) Default in debug builds (none needed)
Enforced (release) CI/staging release builds footprint_enforce_release
Disabled Proven hot-path exemptions only unsafe_graph

Enabling both footprint_enforce_release and unsafe_graph is a compile error.

echo-dind-tests

Feature Default Description
dind_ops no Enables test-only ops (e.g., put_kv) for DIND convergence tests.

echo-dry-tests

Feature Default Description
det_float no Passthrough to warp-core/det_float for CI lane selection.
det_fixed no Passthrough to warp-core/det_fixed for CI lane selection.

echo-wasm-abi

Feature Default Description
std yes Standard library support (enables serde/std, ciborium/std, and half/std).
alloc no Alloc-only mode for no_std environments.

echo-runtime-schema

Feature Default Description
std yes Standard library support.
serde yes Enables serde derives for shared runtime-schema ids, counters, and structural keys. Consumers opt in explicitly when default features are disabled.

echo-registry-api

Feature Default Description
std yes Standard library support.

echo-scene-port

Feature Default Description
std yes Standard library support.

echo-scene-codec

Feature Default Description
std yes Standard library support (enables echo-scene-port/std, minicbor/std).
test-utils no Test utilities for codec testing.

warp-wasm

Feature Default Description
console-panic no Routes panic messages to the browser console via console_error_panic_hook.

ttd-browser

Feature Default Description
console-panic no Routes panic messages to the browser console via console_error_panic_hook while debugging the Echo browser host bridge.

echo-wasm-bindings

Feature Default Description
wasm no Enables wasm-bindgen support for WebAssembly bindings.

See Also