[verified] fix: preserve tracker precision eligibility

.scratch/routing-compatibility-regression/PRD.md

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+# PRD: Legacy routing compatibility regression
+
+## Overview
+
+The tracker’s new request-precision gate rejects legacy node registrations that omit `quantization`. This conflicts with the explicit `capability_policy=compat` rollout: an older node without a capability report remains routable, but an older node without a quantization field is silently excluded from proxy, pinned-route, benchmark, billing, and latency paths.
+
+## Goal
+
+Restore backward-compatible routing for legacy registrations while preserving fail-closed behavior for explicitly declared invalid/unsupported quantization values.
+
+## Quality gates
+
+- Run targeted routing, billing, benchmark, pricing, validation, and latency tests.
+- Run `python -m pytest -q` before completion and record any unrelated failures exactly.
+- Preserve the admission-policy invariant: invalid capability reports remain non-routable; absent reports route only under `compat`.
+
+## User story
+
+### RCR-001: Legacy registration precision fallback
+
+As an operator upgrading a mixed fleet, I need nodes that predate the `quantization` registration field to serve default-precision requests under `compat`, so the tracker rollout does not make otherwise healthy legacy nodes dark.
+
+## Non-goals
+
+- Do not weaken `enforce` capability policy.
+- Do not treat explicitly malformed or unsupported quantization values as valid.
+- Do not change requested-precision semantics for nodes that declare a supported precision.

.scratch/routing-compatibility-regression/issues/01-legacy-registration-precision-fallback.md

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+# RCR-001 — Legacy registration precision fallback
+
+Status: ready-for-agent
+Priority: Critical
+
+## Problem
+
+The tracker now filters proxy and pinned-route candidates through `_quantization_satisfies(node.quantization, requested_quantization)`. A registration produced before the protocol added singular `quantization` is normalized to `quantizations=["bfloat16"]`, but leaves `node.quantization is None`; routing then fails every request, including the default `bfloat16` request.
+
+The defect is therefore at protocol normalization: registration correctly records an available plural capability but never chooses a compatible active precision for the legacy entry.
+
+This is inconsistent with the explicit capability admission rollout policy: an absent capability report is routable under `compat`. Logs show `capability=absent routable=True`, while `/v1/chat/completions` returns 503 or a pinned route returns 409 because the separate precision gate excludes the same legacy node.
+
+## Evidence
+
+Representative tight repros fail on current `master`:
+
+- `tests/test_billing_ledger.py::test_proxy_chat_bills_credited_client_and_credits_node` → HTTP 503
+- `tests/test_tracker_routing.py::test_tracker_proxy_accepts_hf_model_alias_from_quickstart` → HTTP 503
+- `tests/test_manual_route_benchmark.py::test_pinned_route_uses_named_node` → HTTP 409
+- `tests/test_model_speed_latency.py::test_tracker_records_increasing_hop_latency_for_model_and_hardware` → HTTP 409 for every parameter
+
+Each fixture registers a complete, healthy legacy node without `quantization`; tracker registration logs show it as routable under `compat`.
+
+## Acceptance criteria
+
+- [ ] Legacy nodes omitting the `quantization` field are treated as the historical default precision for compatibility purposes.
+- [ ] Explicit `null`, invalid, or unsupported declared precision never receives that fallback and remains excluded from routing, assignment, and coverage calculations, including after managed shard assignment/rebalancing.
+- [ ] Raft replication preserves singular `quantization` and plural `quantizations`; follower routing has identical precision eligibility to the leader.
+- [ ] `capability_policy=enforce` still excludes absent capability reports regardless of precision fallback.
+- [ ] Automatic proxy routing, pinned routes, benchmark routes, and route-stat sampling use the same compatibility rule.
+- [ ] Add behavior-level tracker HTTP tests for legacy omission and explicit invalid declaration.
+- [ ] Targeted billing, routing, benchmark, model-speed, pricing, forfeiture, and TOPLOC dispatch tests pass.
+- [ ] Run the full suite and document any failures not caused by this issue.
+
+## Implementation notes
+
+Keep the compatibility decision at the protocol-normalization boundary, not scattered into individual route paths. A normalized legacy default can preserve existing `_quantization_satisfies` semantics while differentiating an omitted field from an explicitly invalid value.

.scratch/routing-compatibility-regression/prd.json

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+{
+  "name": "Legacy routing compatibility regression",
+  "description": "Restore compat-policy routing for legacy node registrations that omit quantization without weakening validation for invalid declared values.",
+  "branchName": "ralph/routing-compatibility-regression",
+  "userStories": [
+    {
+      "id": "RCR-001",
+      "title": "Legacy registration precision fallback",
+      "description": "As an operator upgrading a mixed fleet, I need nodes that predate the quantization registration field to serve default-precision requests under compat, so otherwise healthy legacy nodes do not become dark.",
+      "acceptanceCriteria": [
+        "A legacy registration without quantization is eligible for a bfloat16 request when capability policy is compat.",
+        "The same registration is excluded under capability policy enforce because its capability report is absent.",
+        "A node that explicitly declares null, an invalid, or an unsupported quantization remains excluded from routing, assignment, and coverage calculations, including after managed shard assignment/rebalancing.",
+        "Raft-applied registrations preserve both singular quantization and plural quantizations so follower routing matches leader routing.",
+        "Automatic proxy routing, pinned routes, manual benchmarks, billing proxy paths, and route-latency sampling retain their existing behavior for legacy registrations.",
+        "Tests cover the legacy/no-field case and explicit-invalid-field case at the tracker HTTP seam.",
+        "Targeted routing, billing, benchmark, pricing, validation, and latency tests pass.",
+        "python -m pytest -q is run and unrelated failures are recorded exactly."
+      ],
+      "priority": 1,
+      "passes": true,
+      "dependsOn": [],
+      "completionNotes": "Completed by agent"
+    }
+  ],
+  "metadata": {
+    "updatedAt": "2026-07-13T07:25:08.460Z"
+  }
+}