Compiler and Foundry Layer

Foundry Compilation Model

Foundry compilation applies governance and hardware-like constraints before execution.

Core operations:

Validate circuit against foundry policy.
Optionally inject calibrated/static mode-loss gates.
Emit compiled circuit for backend execution.

Reference implementation:

core-swift/Sources/SchroSIM/src/compiler/foundry/foundry_spec.swift

Key Foundry Constraints

max_modes
max_squeezing_r
allow_non_gaussian
allow_measurements
mode_loss_eta
inject_mode_loss

Registry and Signature Flow

Registry-backed production profiles:

config/foundry_registry.json
foundry-admin add-draft
foundry-admin promote (approval/signing)

Runtime profile verification includes:

status checks (approved only),
validity window checks,
HMAC signature verification.

Public Governance Inputs

registry file path override: --foundry-registry
signing key: --foundry-key or env var

Profile Lifecycle (Public CLI Flow)

The runtime/registry lifecycle implemented by schrosim-cli is:

Draft creation (foundry-admin add-draft).
Approval and signing (foundry-admin promote --to approved).
Runtime consumption (run|trace --prod with foundry_profile).
Deprecation (foundry-admin promote --to deprecated) when superseded.

State transition rules are strict:

draft -> approved
approved -> deprecated

Any other transition is rejected as invalid.

Minimal example:

schrosim-cli foundry-admin add-draft \
  --profile-id public-default \
  --version 1 \
  --spec <foundry-spec.json> \
  --approver platform-admin

schrosim-cli foundry-admin promote \
  --profile-id public-default \
  --version 1 \
  --to approved \
  --approver platform-admin \
  --key "$SCHROSIM_FOUNDRY_HMAC_KEY"

Minimal <foundry-spec.json> shape:

{
  "name": "public-default-v1",
  "max_modes": 64,
  "max_squeezing_r": 1.2,
  "allow_non_gaussian": true,
  "allow_measurements": true,
  "inject_mode_loss": true,
  "mode_loss_eta": [0.995]
}

Validation and Failure Matrix

SchroSIM currently emits typed error classes rather than numeric failure codes. The table below maps the stable classes surfaced by the compiler and runtime.

Error class	Trigger	Typical message shape	Surface
`FoundryValidationError.invalidMaxModes`	`max_modes <= 0`	`Foundry maxModes must be > 0`	compile/validate
`FoundryValidationError.modeCountExceedsLimit`	`circuit.modes > max_modes`	`Circuit modes ... exceed foundry limit ...`	compile/validate
`FoundryValidationError.invalidSqueezingLimit`	non-finite or negative `max_squeezing_r`	`maxSqueezingR must be finite and >= 0`	compile/validate
`FoundryValidationError.squeezingLimitExceeded`	`abs(r) > max_squeezing_r`	`Squeezing on mode ... exceeds foundry maxSqueezingR ...`	compile/validate
`FoundryValidationError.modeLossLengthMismatch`	`mode_loss_eta.count != modes`	`modeLossEta must have ... values`	compile/validate
`FoundryValidationError.invalidModeLoss`	non-finite or out-of-range loss eta	`modeLossEta[i] must be finite in [0,1]`	compile/validate
`FoundryValidationError.nonGaussianDisallowed`	non-Gaussian injection while disabled	`Foundry disallows non-Gaussian injection`	compile/validate
`FoundryValidationError.measurementsDisallowed`	measurement/feed-forward while disabled	`Foundry disallows measurement gates`	compile/validate
`FoundryValidationError.unsupportedPlaceholderGate`	placeholder gate reaches compile	`Foundry rejects placeholder gate`	compile/validate
`CLIInputError.invalidField`	invalid `--prod`/foundry field combinations	`Inline 'foundry' block is not allowed in --prod mode`	CLI argument/input parse
`FoundryRegistryError.nonApprovedProfile`	profile exists but not approved	`... is not approved (status=...)`	registry resolution
`FoundryRegistryError.unsignedProfile`	approved profile without signature	`... is missing a signature`	registry resolution
`FoundryRegistryError.invalidSignature`	HMAC mismatch for approved profile	`signature verification failed`	registry resolution
`FoundryRegistryError.expiredProfile`	outside `valid_from/valid_to` window	`... is expired/not-yet-valid`	registry resolution

Practical rule: treat these class names as the stable automation interface, and treat the message body as human diagnostics.