qCompute — Backend Metadata Profiles

File: qc_BackendProfiles.md
Layer: RTT‑Inside Compute Harness
Status: Canonical (2026)

This document defines the deep metadata profiles for all qCompute backends.

Backends are structural abstractions, not hardware interfaces.
They define legality, drift envelopes, tier support, and routing behavior.

qCompute computes structure, not amplitudes.

1. Metadata Schema#

Each backend profile follows this schema:

backend_id: "<string>"
display_name: "<string>"

tier_support:
  - r1 | r2 | r3

environment_legal:
  - sandbox | production

drift_envelope:
  predicted: "<low|medium|high>"
  measured: "<low|medium|high>"
  max_accumulated: <float>

frame_behavior:
  reuse: true|false
  always_new: true|false

transition_behavior:
  sandbox_to_production: "allowed" | "token-required" | "forbidden"
  production_to_archive: "allowed" | "token-required" | "forbidden"

routing_constraints:
  tier_binding: "<r1|r2|r3>"
  environment_required: "<sandbox|production>"
  token_required: true|false

notes: "<freeform>"

All fields are required.

2. Backend Profiles#

2.1 local-sim#

backend_id: "local-sim"
display_name: "Local Structural Simulator"

tier_support:
  - r1

environment_legal:
  - sandbox
  - production

drift_envelope:
  predicted: "low"
  measured: "low"
  max_accumulated: 1.0

frame_behavior:
  reuse: true
  always_new: false

transition_behavior:
  sandbox_to_production: "allowed"
  production_to_archive: "forbidden"

routing_constraints:
  tier_binding: "r1"
  environment_required: "sandbox-or-production"
  token_required: false

notes: "Used for primitive operators. Stable, low drift, frame reuse preferred."

2.2 hybrid-sim#

backend_id: "hybrid-sim"
display_name: "Hybrid Structural Simulator"

tier_support:
  - r1
  - r2

environment_legal:
  - sandbox
  - production

drift_envelope:
  predicted: "medium"
  measured: "medium"
  max_accumulated: 3.0

frame_behavior:
  reuse: true
  always_new: false

transition_behavior:
  sandbox_to_production: "allowed"
  production_to_archive: "forbidden"

routing_constraints:
  tier_binding: "r2"
  environment_required: "sandbox-or-production"
  token_required: false

notes: "Used for composite operators. Medium drift. May reuse or open new frame depending on tier escalation or drift overflow."

2.3 hardware-qpu-2#

backend_id: "hardware-qpu-2"
display_name: "Hardware Pulse Tier (Structural)"

tier_support:
  - r3

environment_legal:
  - production

drift_envelope:
  predicted: "high"
  measured: "high"
  max_accumulated: 0.5

frame_behavior:
  reuse: false
  always_new: true

transition_behavior:
  sandbox_to_production: "token-required"
  production_to_archive: "token-required"

routing_constraints:
  tier_binding: "r3"
  environment_required: "production"
  token_required: true

notes: "Used for pulse operators. High drift. Always opens new frame. Token-gated. Forbidden in sandbox and archive."

3. Cross‑Backend Comparison#

4. Routing Integration#

Router uses backend profiles to determine:

• backend legality
• tier binding
• environment legality
• token requirements
• frame reuse vs. new frame
• drift overflow thresholds

Routing reasons include:

• "tier-escalation"
• "tier-binding"
• "environment-requirement"
• "token-required"
• "drift-overflow"
• "measurement"
• "meta"

5. Capture Metadata#

Each operator includes backend metadata:

routing:
  backend: "<backend-id>"
  reason: "<routing-reason>"
  frame_action: "reuse" | "new"

Each frame includes backend summary:

frame_backend:
  id: "<backend-id>"
  drift_profile: "<low|medium|high>"
  tier_support: [...]

All fields are required.

6. Replay Verification#

Replay verifies:

• backend legality
• tier binding
• environment legality
• drift envelope
• frame boundaries
• transition correctness
• token requirements
• hash chain integrity

Replay is deterministic and read‑only.

7. Invariants#

1. r1 → local-sim
2. r2 → hybrid-sim
3. r3 → hardware-qpu-2
4. hardware-qpu-2 requires production
5. hardware-qpu-2 requires token
6. drift must not exceed envelope
7. frame behavior must match backend profile
8. archive forbids all backends

8. Summary#

Backend Profiles define:

• identity
• tier support
• drift envelopes
• environment legality
• frame behavior
• transition behavior
• routing constraints

They are the deep structural metadata layer of qCompute.