diff --git a/protocol/evidence-chain.md b/protocol/evidence-chain.md
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--- /dev/null
+++ b/protocol/evidence-chain.md
@@ -0,0 +1,101 @@
+# Evidence Chain Contract
+
+The evidence chain contract fixes the MVP relationship between L1 audit records
+and L4 agent or worker evidence without changing either implementation surface.
+It is a fixture-level contract for now: services may persist the records in their
+existing tables, while the chain example binds the identities that must not
+split later.
+
+## Minimal ID Relationship
+
+Every MVP evidence chain has one `operationId`, one `traceId`, one or more
+`auditId` values, and one or more `evidenceId` values.
+
+- `operationId` is the workflow anchor. It must match the
+  `hardwareOperation.operationId`, every chain `auditEvents[].operationId`,
+  every `traceEvents[].operationId`, and every
+  `evidenceRecords[].operationId`.
+- `traceId` is the request and execution correlation ID. It must match every
+  `auditEvents[].traceId` and every `traceEvents[].traceId`. Because the L0
+  `evidence-record` schema does not carry `traceId` at the top level, MVP
+  evidence records must copy it to `evidenceRecords[].metadata.traceId`.
+- `auditId` is unique per audit event in a chain. Each evidence record must set
+  `metadata.producedByAuditId` to an audit event in the same fixture. The audit
+  event that records evidence must target that evidence record with
+  `targetType: "evidence_record"` and `targetId: <evidenceId>`.
+- `evidenceId` is the stable artifact record ID. It must be unique in a chain,
+  belong to the same `projectId`, `operationId`, and `environment`, and point to
+  a content-addressed artifact through `uri`, `sha256`, and optional
+  `sizeBytes`.
+
+The same relationship applies whether the producer is a hardware trusted loop
+or an agent automation loop. Agent and worker IDs are optional for hardware-only
+chains, but when present they must be carried consistently by the operation,
+trace events, and evidence records.
+
+## MVP Required Fields
+
+The fixture root is not a database table. It exists to verify cross-record
+relationships and must include:
+
+- `chainId`
+- `schemaVersion`
+- `scenario`
+- `projectId`
+- `operationId`
+- `traceId`
+- `environment`
+- `hardwareOperation`
+- `auditEvents`
+- `traceEvents`
+- `evidenceRecords`
+
+`hardwareOperation` must satisfy the L0 hardware operation required fields:
+`operationId`, `projectId`, `gatewaySessionId`, `resourceId`, `capabilityId`,
+`requestedBy`, `status`, `environment`, `requestedAt`, and `updatedAt`.
+
+Each MVP `auditEvents[]` entry must satisfy the L0 audit event required fields
+and additionally include `projectId`, `operationId`, and `outcome` so the audit
+stream can be joined back to the operation without service-specific inference.
+
+Each MVP `traceEvents[]` entry must satisfy the L0 trace event required fields
+and additionally include `operationId`.
+
+Each MVP `evidenceRecords[]` entry must satisfy the L0 evidence record required
+fields and additionally include:
+
+- `metadata.traceId`
+- `metadata.producedByAuditId`
+
+Agent automation chains must also include `agentSessionId` and
+`workerSessionId` at the fixture root, on the hardware operation, on trace
+events, and on evidence records.
+
+## Future Enhancements
+
+The first version intentionally avoids heavier guarantees. Later contracts may
+add:
+
+- canonical chain hashing, previous-record links, and signatures
+- attestation data from real hardware roots of trust
+- retention policy, storage tier, and artifact redaction metadata
+- richer OpenTelemetry or JSON-LD correlation fields
+- multiple operations under one trace with explicit parent-child edges
+- policy decision records for agent authorization and remediation
+
+Those additions must preserve the MVP identity bindings above.
+
+## Fixtures
+
+The MVP fixture set lives under `protocol/examples/evidence-chain`:
+
+- `fixtures/hardware-trusted-loop.json`
+- `fixtures/agent-automation-loop.json`
+- `artifacts/hardware-trusted-measurement.json`
+- `artifacts/agent-automation-report.json`
+
+Validate the examples with:
+
+```sh
+node scripts/validate-evidence-chain.mjs
+```
diff --git a/protocol/examples/evidence-chain/README.md b/protocol/examples/evidence-chain/README.md
new file mode 100644
index 00000000..9a4fde50
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+++ b/protocol/examples/evidence-chain/README.md
@@ -0,0 +1,12 @@
+# Evidence Chain Examples
+
+These fixtures model the minimum MVP chain between hardware operations, audit
+events, trace events, and evidence records.
+
+- `fixtures/hardware-trusted-loop.json` covers the hardware trusted closed loop.
+- `fixtures/agent-automation-loop.json` covers the agent automation closed loop.
+- `artifacts/` contains small content-addressed files referenced by the
+  evidence records.
+
+Run `node scripts/validate-evidence-chain.mjs` from the repository root to
+verify field completeness, cross-record references, and artifact checksums.
diff --git a/protocol/examples/evidence-chain/artifacts/agent-automation-report.json b/protocol/examples/evidence-chain/artifacts/agent-automation-report.json
new file mode 100644
index 00000000..6a3a05e2
--- /dev/null
+++ b/protocol/examples/evidence-chain/artifacts/agent-automation-report.json
@@ -0,0 +1,13 @@
+{
+  "format": "hwlab.agent-report.v1",
+  "agentSessionId": "ags_agent-auto-001",
+  "workerSessionId": "wks_agent-auto-001",
+  "operationId": "op_agent-auto-loop-001",
+  "result": "succeeded",
+  "steps": [
+    "selected capability",
+    "ran firmware smoke command",
+    "persisted evidence"
+  ],
+  "createdAt": "2026-05-21T00:20:06.000Z"
+}
diff --git a/protocol/examples/evidence-chain/artifacts/hardware-trusted-measurement.json b/protocol/examples/evidence-chain/artifacts/hardware-trusted-measurement.json
new file mode 100644
index 00000000..0bc68aac
--- /dev/null
+++ b/protocol/examples/evidence-chain/artifacts/hardware-trusted-measurement.json
@@ -0,0 +1,15 @@
+{
+  "format": "hwlab.measurement.v1",
+  "resourceId": "res_boxsim-alpha",
+  "capabilityId": "cap_gpio-measure",
+  "operationId": "op_hw-trusted-loop-001",
+  "samples": [
+    {
+      "name": "gpio0",
+      "unit": "logic",
+      "value": 1,
+      "trusted": true
+    }
+  ],
+  "capturedAt": "2026-05-21T00:10:03.000Z"
+}
diff --git a/protocol/examples/evidence-chain/fixtures/agent-automation-loop.json b/protocol/examples/evidence-chain/fixtures/agent-automation-loop.json
new file mode 100644
index 00000000..e94e6977
--- /dev/null
+++ b/protocol/examples/evidence-chain/fixtures/agent-automation-loop.json
@@ -0,0 +1,235 @@
+{
+  "chainId": "echain_agent-auto-loop",
+  "schemaVersion": 1,
+  "scenario": "agent-automation-closed-loop",
+  "title": "Agent automation closed loop MVP",
+  "environment": "dev",
+  "projectId": "prj_evidence-chain",
+  "operationId": "op_agent-auto-loop-001",
+  "traceId": "trc_agent-auto-loop-001",
+  "gatewaySessionId": "gws_evidence-gateway-001",
+  "agentSessionId": "ags_agent-auto-001",
+  "workerSessionId": "wks_agent-auto-001",
+  "resourceId": "res_boxsim-beta",
+  "capabilityId": "cap_firmware-smoke",
+  "hardwareOperation": {
+    "operationId": "op_agent-auto-loop-001",
+    "projectId": "prj_evidence-chain",
+    "gatewaySessionId": "gws_evidence-gateway-001",
+    "agentSessionId": "ags_agent-auto-001",
+    "workerSessionId": "wks_agent-auto-001",
+    "resourceId": "res_boxsim-beta",
+    "capabilityId": "cap_firmware-smoke",
+    "requestedBy": "wkr_agent-auto-001",
+    "input": {
+      "command": "firmware-smoke",
+      "timeoutSeconds": 60
+    },
+    "output": {
+      "exitCode": 0,
+      "result": "passed"
+    },
+    "status": "succeeded",
+    "environment": "dev",
+    "requestedAt": "2026-05-21T00:20:02.000Z",
+    "startedAt": "2026-05-21T00:20:03.000Z",
+    "completedAt": "2026-05-21T00:20:05.000Z",
+    "updatedAt": "2026-05-21T00:20:05.000Z"
+  },
+  "auditEvents": [
+    {
+      "auditId": "aud_agent-auto-session-started",
+      "traceId": "trc_agent-auto-loop-001",
+      "actorType": "user",
+      "actorId": "usr_alice",
+      "action": "agent.session.started",
+      "targetType": "agent_session",
+      "targetId": "ags_agent-auto-001",
+      "projectId": "prj_evidence-chain",
+      "operationId": "op_agent-auto-loop-001",
+      "serviceId": "hwlab-agent-mgr",
+      "environment": "dev",
+      "outcome": "accepted",
+      "metadata": {
+        "agentSessionId": "ags_agent-auto-001",
+        "goal": "run firmware smoke and persist evidence"
+      },
+      "occurredAt": "2026-05-21T00:20:00.000Z"
+    },
+    {
+      "auditId": "aud_agent-auto-worker-started",
+      "traceId": "trc_agent-auto-loop-001",
+      "actorType": "agent",
+      "actorId": "agt_agent-auto-001",
+      "action": "worker.session.started",
+      "targetType": "worker_session",
+      "targetId": "wks_agent-auto-001",
+      "projectId": "prj_evidence-chain",
+      "gatewaySessionId": "gws_evidence-gateway-001",
+      "workerSessionId": "wks_agent-auto-001",
+      "operationId": "op_agent-auto-loop-001",
+      "serviceId": "hwlab-agent-worker",
+      "environment": "dev",
+      "outcome": "accepted",
+      "metadata": {
+        "agentSessionId": "ags_agent-auto-001"
+      },
+      "occurredAt": "2026-05-21T00:20:01.000Z"
+    },
+    {
+      "auditId": "aud_agent-auto-operation-requested",
+      "traceId": "trc_agent-auto-loop-001",
+      "actorType": "worker",
+      "actorId": "wkr_agent-auto-001",
+      "action": "hardware.operation.requested",
+      "targetType": "hardware_operation",
+      "targetId": "op_agent-auto-loop-001",
+      "projectId": "prj_evidence-chain",
+      "gatewaySessionId": "gws_evidence-gateway-001",
+      "workerSessionId": "wks_agent-auto-001",
+      "operationId": "op_agent-auto-loop-001",
+      "serviceId": "hwlab-agent-worker",
+      "environment": "dev",
+      "outcome": "accepted",
+      "metadata": {
+        "agentSessionId": "ags_agent-auto-001",
+        "capabilityId": "cap_firmware-smoke"
+      },
+      "occurredAt": "2026-05-21T00:20:02.000Z"
+    },
+    {
+      "auditId": "aud_agent-auto-operation-succeeded",
+      "traceId": "trc_agent-auto-loop-001",
+      "actorType": "service",
+      "actorId": "svc_hwlab-box-simu",
+      "action": "hardware.operation.succeeded",
+      "targetType": "hardware_operation",
+      "targetId": "op_agent-auto-loop-001",
+      "projectId": "prj_evidence-chain",
+      "gatewaySessionId": "gws_evidence-gateway-001",
+      "workerSessionId": "wks_agent-auto-001",
+      "operationId": "op_agent-auto-loop-001",
+      "serviceId": "hwlab-box-simu",
+      "environment": "dev",
+      "outcome": "succeeded",
+      "metadata": {
+        "agentSessionId": "ags_agent-auto-001",
+        "exitCode": 0
+      },
+      "occurredAt": "2026-05-21T00:20:05.000Z"
+    },
+    {
+      "auditId": "aud_agent-auto-evidence-recorded",
+      "traceId": "trc_agent-auto-loop-001",
+      "actorType": "worker",
+      "actorId": "wkr_agent-auto-001",
+      "action": "evidence.recorded",
+      "targetType": "evidence_record",
+      "targetId": "evd_agent-auto-report",
+      "projectId": "prj_evidence-chain",
+      "gatewaySessionId": "gws_evidence-gateway-001",
+      "workerSessionId": "wks_agent-auto-001",
+      "operationId": "op_agent-auto-loop-001",
+      "serviceId": "hwlab-agent-worker",
+      "environment": "dev",
+      "outcome": "succeeded",
+      "metadata": {
+        "agentSessionId": "ags_agent-auto-001",
+        "evidenceId": "evd_agent-auto-report",
+        "evidenceKind": "report"
+      },
+      "occurredAt": "2026-05-21T00:20:06.000Z"
+    }
+  ],
+  "traceEvents": [
+    {
+      "traceEventId": "tev_agent-auto-goal",
+      "traceId": "trc_agent-auto-loop-001",
+      "projectId": "prj_evidence-chain",
+      "agentSessionId": "ags_agent-auto-001",
+      "workerSessionId": "wks_agent-auto-001",
+      "operationId": "op_agent-auto-loop-001",
+      "serviceId": "hwlab-agent-mgr",
+      "level": "info",
+      "message": "Agent session accepted automation goal",
+      "environment": "dev",
+      "metadata": {
+        "auditId": "aud_agent-auto-session-started"
+      },
+      "occurredAt": "2026-05-21T00:20:00.000Z"
+    },
+    {
+      "traceEventId": "tev_agent-auto-worker",
+      "traceId": "trc_agent-auto-loop-001",
+      "projectId": "prj_evidence-chain",
+      "agentSessionId": "ags_agent-auto-001",
+      "workerSessionId": "wks_agent-auto-001",
+      "operationId": "op_agent-auto-loop-001",
+      "serviceId": "hwlab-agent-worker",
+      "level": "info",
+      "message": "Worker requested firmware smoke operation",
+      "environment": "dev",
+      "metadata": {
+        "auditId": "aud_agent-auto-operation-requested"
+      },
+      "occurredAt": "2026-05-21T00:20:02.000Z"
+    },
+    {
+      "traceEventId": "tev_agent-auto-operation",
+      "traceId": "trc_agent-auto-loop-001",
+      "projectId": "prj_evidence-chain",
+      "agentSessionId": "ags_agent-auto-001",
+      "workerSessionId": "wks_agent-auto-001",
+      "operationId": "op_agent-auto-loop-001",
+      "serviceId": "hwlab-box-simu",
+      "level": "info",
+      "message": "Firmware smoke operation completed",
+      "environment": "dev",
+      "metadata": {
+        "auditId": "aud_agent-auto-operation-succeeded"
+      },
+      "occurredAt": "2026-05-21T00:20:05.000Z"
+    },
+    {
+      "traceEventId": "tev_agent-auto-evidence",
+      "traceId": "trc_agent-auto-loop-001",
+      "projectId": "prj_evidence-chain",
+      "agentSessionId": "ags_agent-auto-001",
+      "workerSessionId": "wks_agent-auto-001",
+      "operationId": "op_agent-auto-loop-001",
+      "serviceId": "hwlab-agent-worker",
+      "level": "info",
+      "message": "Agent report evidence persisted",
+      "environment": "dev",
+      "metadata": {
+        "auditId": "aud_agent-auto-evidence-recorded",
+        "evidenceId": "evd_agent-auto-report"
+      },
+      "occurredAt": "2026-05-21T00:20:06.000Z"
+    }
+  ],
+  "evidenceRecords": [
+    {
+      "evidenceId": "evd_agent-auto-report",
+      "projectId": "prj_evidence-chain",
+      "operationId": "op_agent-auto-loop-001",
+      "agentSessionId": "ags_agent-auto-001",
+      "workerSessionId": "wks_agent-auto-001",
+      "kind": "report",
+      "uri": "protocol/examples/evidence-chain/artifacts/agent-automation-report.json",
+      "mimeType": "application/json",
+      "sha256": "2fc63687cd3170c9cf34cd650aaedfb84d3fe75683ae969ae286230ce3b425a7",
+      "sizeBytes": 340,
+      "serviceId": "hwlab-agent-worker",
+      "environment": "dev",
+      "metadata": {
+        "traceId": "trc_agent-auto-loop-001",
+        "producedByAuditId": "aud_agent-auto-evidence-recorded",
+        "agentSessionId": "ags_agent-auto-001",
+        "workerSessionId": "wks_agent-auto-001",
+        "producerServiceId": "hwlab-agent-worker"
+      },
+      "createdAt": "2026-05-21T00:20:06.000Z"
+    }
+  ]
+}
diff --git a/protocol/examples/evidence-chain/fixtures/hardware-trusted-loop.json b/protocol/examples/evidence-chain/fixtures/hardware-trusted-loop.json
new file mode 100644
index 00000000..b90fa87d
--- /dev/null
+++ b/protocol/examples/evidence-chain/fixtures/hardware-trusted-loop.json
@@ -0,0 +1,182 @@
+{
+  "chainId": "echain_hw-trusted-loop",
+  "schemaVersion": 1,
+  "scenario": "hardware-trusted-closed-loop",
+  "title": "Hardware trusted closed loop MVP",
+  "environment": "dev",
+  "projectId": "prj_evidence-chain",
+  "operationId": "op_hw-trusted-loop-001",
+  "traceId": "trc_hw-trusted-loop-001",
+  "gatewaySessionId": "gws_evidence-gateway-001",
+  "resourceId": "res_boxsim-alpha",
+  "capabilityId": "cap_gpio-measure",
+  "hardwareOperation": {
+    "operationId": "op_hw-trusted-loop-001",
+    "projectId": "prj_evidence-chain",
+    "gatewaySessionId": "gws_evidence-gateway-001",
+    "resourceId": "res_boxsim-alpha",
+    "capabilityId": "cap_gpio-measure",
+    "requestedBy": "usr_alice",
+    "input": {
+      "command": "measure",
+      "port": "gpio0"
+    },
+    "output": {
+      "sampleCount": 1,
+      "result": "logic-high"
+    },
+    "status": "succeeded",
+    "environment": "dev",
+    "requestedAt": "2026-05-21T00:10:00.000Z",
+    "startedAt": "2026-05-21T00:10:01.000Z",
+    "completedAt": "2026-05-21T00:10:03.000Z",
+    "updatedAt": "2026-05-21T00:10:03.000Z"
+  },
+  "auditEvents": [
+    {
+      "auditId": "aud_hw-trusted-requested",
+      "traceId": "trc_hw-trusted-loop-001",
+      "actorType": "user",
+      "actorId": "usr_alice",
+      "action": "hardware.operation.requested",
+      "targetType": "hardware_operation",
+      "targetId": "op_hw-trusted-loop-001",
+      "projectId": "prj_evidence-chain",
+      "gatewaySessionId": "gws_evidence-gateway-001",
+      "operationId": "op_hw-trusted-loop-001",
+      "serviceId": "hwlab-cloud-api",
+      "environment": "dev",
+      "outcome": "accepted",
+      "metadata": {
+        "requestId": "req_hw-trusted-001"
+      },
+      "occurredAt": "2026-05-21T00:10:00.000Z"
+    },
+    {
+      "auditId": "aud_hw-trusted-dispatched",
+      "traceId": "trc_hw-trusted-loop-001",
+      "actorType": "service",
+      "actorId": "svc_hwlab-gateway-simu",
+      "action": "hardware.operation.dispatched",
+      "targetType": "hardware_operation",
+      "targetId": "op_hw-trusted-loop-001",
+      "projectId": "prj_evidence-chain",
+      "gatewaySessionId": "gws_evidence-gateway-001",
+      "operationId": "op_hw-trusted-loop-001",
+      "serviceId": "hwlab-gateway-simu",
+      "environment": "dev",
+      "outcome": "accepted",
+      "metadata": {
+        "resourceId": "res_boxsim-alpha",
+        "capabilityId": "cap_gpio-measure"
+      },
+      "occurredAt": "2026-05-21T00:10:01.000Z"
+    },
+    {
+      "auditId": "aud_hw-trusted-succeeded",
+      "traceId": "trc_hw-trusted-loop-001",
+      "actorType": "service",
+      "actorId": "svc_hwlab-box-simu",
+      "action": "hardware.operation.succeeded",
+      "targetType": "hardware_operation",
+      "targetId": "op_hw-trusted-loop-001",
+      "projectId": "prj_evidence-chain",
+      "gatewaySessionId": "gws_evidence-gateway-001",
+      "operationId": "op_hw-trusted-loop-001",
+      "serviceId": "hwlab-box-simu",
+      "environment": "dev",
+      "outcome": "succeeded",
+      "metadata": {
+        "sampleCount": 1
+      },
+      "occurredAt": "2026-05-21T00:10:03.000Z"
+    },
+    {
+      "auditId": "aud_hw-trusted-evidence-recorded",
+      "traceId": "trc_hw-trusted-loop-001",
+      "actorType": "service",
+      "actorId": "svc_hwlab-cloud-api",
+      "action": "evidence.recorded",
+      "targetType": "evidence_record",
+      "targetId": "evd_hw-trusted-measurement",
+      "projectId": "prj_evidence-chain",
+      "gatewaySessionId": "gws_evidence-gateway-001",
+      "operationId": "op_hw-trusted-loop-001",
+      "serviceId": "hwlab-cloud-api",
+      "environment": "dev",
+      "outcome": "succeeded",
+      "metadata": {
+        "evidenceId": "evd_hw-trusted-measurement",
+        "evidenceKind": "measurement"
+      },
+      "occurredAt": "2026-05-21T00:10:04.000Z"
+    }
+  ],
+  "traceEvents": [
+    {
+      "traceEventId": "tev_hw-trusted-accepted",
+      "traceId": "trc_hw-trusted-loop-001",
+      "projectId": "prj_evidence-chain",
+      "operationId": "op_hw-trusted-loop-001",
+      "serviceId": "hwlab-cloud-api",
+      "level": "info",
+      "message": "Hardware operation accepted",
+      "environment": "dev",
+      "metadata": {
+        "auditId": "aud_hw-trusted-requested"
+      },
+      "occurredAt": "2026-05-21T00:10:00.000Z"
+    },
+    {
+      "traceEventId": "tev_hw-trusted-dispatched",
+      "traceId": "trc_hw-trusted-loop-001",
+      "projectId": "prj_evidence-chain",
+      "operationId": "op_hw-trusted-loop-001",
+      "serviceId": "hwlab-gateway-simu",
+      "level": "info",
+      "message": "Gateway dispatched trusted measurement",
+      "environment": "dev",
+      "metadata": {
+        "auditId": "aud_hw-trusted-dispatched"
+      },
+      "occurredAt": "2026-05-21T00:10:01.000Z"
+    },
+    {
+      "traceEventId": "tev_hw-trusted-evidence",
+      "traceId": "trc_hw-trusted-loop-001",
+      "projectId": "prj_evidence-chain",
+      "operationId": "op_hw-trusted-loop-001",
+      "serviceId": "hwlab-cloud-api",
+      "level": "info",
+      "message": "Measurement evidence persisted",
+      "environment": "dev",
+      "metadata": {
+        "auditId": "aud_hw-trusted-evidence-recorded",
+        "evidenceId": "evd_hw-trusted-measurement"
+      },
+      "occurredAt": "2026-05-21T00:10:04.000Z"
+    }
+  ],
+  "evidenceRecords": [
+    {
+      "evidenceId": "evd_hw-trusted-measurement",
+      "projectId": "prj_evidence-chain",
+      "operationId": "op_hw-trusted-loop-001",
+      "kind": "measurement",
+      "uri": "protocol/examples/evidence-chain/artifacts/hardware-trusted-measurement.json",
+      "mimeType": "application/json",
+      "sha256": "da1bb981f0a966e6906bfdf6a0387180617c8f891c131d7bebf9e19b14989a99",
+      "sizeBytes": 318,
+      "serviceId": "hwlab-cloud-api",
+      "environment": "dev",
+      "metadata": {
+        "traceId": "trc_hw-trusted-loop-001",
+        "producedByAuditId": "aud_hw-trusted-evidence-recorded",
+        "producerServiceId": "hwlab-box-simu",
+        "resourceId": "res_boxsim-alpha",
+        "capabilityId": "cap_gpio-measure"
+      },
+      "createdAt": "2026-05-21T00:10:04.000Z"
+    }
+  ]
+}
diff --git a/scripts/validate-evidence-chain.mjs b/scripts/validate-evidence-chain.mjs
new file mode 100644
index 00000000..6060b944
--- /dev/null
+++ b/scripts/validate-evidence-chain.mjs
@@ -0,0 +1,376 @@
+#!/usr/bin/env node
+import assert from "node:assert/strict";
+import { createHash } from "node:crypto";
+import { readdir, readFile } from "node:fs/promises";
+import path from "node:path";
+import { fileURLToPath } from "node:url";
+import { ENVIRONMENT_DEV, SERVICE_IDS } from "../internal/protocol/index.mjs";
+
+const repoRoot = path.resolve(path.dirname(fileURLToPath(import.meta.url)), "..");
+const fixturesDir = "protocol/examples/evidence-chain/fixtures";
+
+const idPattern = /^[a-z][a-z0-9]*_[A-Za-z0-9._:-]+$/;
+const actionPattern = /^[a-z][a-z0-9_]*(\.[a-z][a-z0-9_]*)+$/;
+const sha256Pattern = /^[a-f0-9]{64}$/;
+
+const rootRequired = [
+  "chainId",
+  "schemaVersion",
+  "scenario",
+  "projectId",
+  "operationId",
+  "traceId",
+  "environment",
+  "hardwareOperation",
+  "auditEvents",
+  "traceEvents",
+  "evidenceRecords"
+];
+
+const hardwareOperationRequired = [
+  "operationId",
+  "projectId",
+  "gatewaySessionId",
+  "resourceId",
+  "capabilityId",
+  "requestedBy",
+  "status",
+  "environment",
+  "requestedAt",
+  "updatedAt"
+];
+
+const auditEventRequired = [
+  "auditId",
+  "traceId",
+  "actorType",
+  "actorId",
+  "action",
+  "targetType",
+  "targetId",
+  "serviceId",
+  "environment",
+  "occurredAt",
+  "projectId",
+  "operationId",
+  "outcome"
+];
+
+const traceEventRequired = [
+  "traceEventId",
+  "traceId",
+  "projectId",
+  "serviceId",
+  "level",
+  "message",
+  "environment",
+  "occurredAt",
+  "operationId"
+];
+
+const evidenceRecordRequired = [
+  "evidenceId",
+  "projectId",
+  "operationId",
+  "kind",
+  "uri",
+  "sha256",
+  "serviceId",
+  "environment",
+  "createdAt"
+];
+
+const operationStatuses = new Set([
+  "requested",
+  "accepted",
+  "queued",
+  "running",
+  "succeeded",
+  "failed",
+  "rejected",
+  "canceled",
+  "timed_out"
+]);
+
+const actorTypes = new Set(["user", "service", "agent", "worker", "system"]);
+const auditOutcomes = new Set(["accepted", "succeeded", "failed", "rejected", "canceled"]);
+const traceLevels = new Set(["debug", "info", "warn", "error"]);
+const evidenceKinds = new Set(["log", "screenshot", "measurement", "artifact", "report", "trace"]);
+const scenarios = new Set(["hardware-trusted-closed-loop", "agent-automation-closed-loop"]);
+
+function assertObject(value, label) {
+  assert.ok(value && typeof value === "object" && !Array.isArray(value), `${label} must be an object`);
+}
+
+function assertRequired(value, fields, label) {
+  for (const field of fields) {
+    assert.ok(Object.hasOwn(value, field), `${label} missing ${field}`);
+  }
+}
+
+function assertId(value, label) {
+  assert.equal(typeof value, "string", `${label} must be a string`);
+  assert.match(value, idPattern, `${label} must match HWLAB id format`);
+}
+
+function assertTimestamp(value, label) {
+  assert.equal(typeof value, "string", `${label} must be a string`);
+  assert.ok(!Number.isNaN(Date.parse(value)), `${label} must be a parseable timestamp`);
+}
+
+function assertServiceId(value, label) {
+  assert.ok(SERVICE_IDS.includes(value), `${label} must be a frozen service id`);
+}
+
+function assertUnique(values, label) {
+  assert.equal(new Set(values).size, values.length, `${label} must be unique`);
+}
+
+function assertSame(actual, expected, label) {
+  assert.equal(actual, expected, `${label} must match ${expected}`);
+}
+
+async function parseFixtures() {
+  const entries = await readdir(path.join(repoRoot, fixturesDir), { withFileTypes: true });
+  const files = entries
+    .filter((entry) => entry.isFile() && entry.name.endsWith(".json"))
+    .map((entry) => path.join(fixturesDir, entry.name))
+    .sort();
+
+  const fixtures = [];
+  for (const relativePath of files) {
+    const raw = await readFile(path.join(repoRoot, relativePath), "utf8");
+    fixtures.push({ relativePath, doc: JSON.parse(raw) });
+  }
+  return fixtures;
+}
+
+async function assertArtifact(record, label) {
+  assert.match(record.sha256, sha256Pattern, `${label}.sha256 must be lowercase sha256`);
+  assert.equal(typeof record.uri, "string", `${label}.uri must be a string`);
+
+  const artifactPath = path.resolve(repoRoot, record.uri);
+  assert.ok(
+    artifactPath.startsWith(`${repoRoot}${path.sep}`),
+    `${label}.uri must point inside the repository`
+  );
+
+  const content = await readFile(artifactPath);
+  const digest = createHash("sha256").update(content).digest("hex");
+  assert.equal(digest, record.sha256, `${label}.sha256 must match ${record.uri}`);
+
+  if (Object.hasOwn(record, "sizeBytes")) {
+    assert.equal(record.sizeBytes, content.byteLength, `${label}.sizeBytes must match ${record.uri}`);
+  }
+}
+
+function validateHardwareOperation(chain, operation) {
+  assertObject(operation, `${chain.chainId}.hardwareOperation`);
+  assertRequired(operation, hardwareOperationRequired, `${chain.chainId}.hardwareOperation`);
+
+  for (const field of [
+    "operationId",
+    "projectId",
+    "gatewaySessionId",
+    "resourceId",
+    "capabilityId",
+    "requestedBy"
+  ]) {
+    assertId(operation[field], `${chain.chainId}.hardwareOperation.${field}`);
+  }
+
+  assertSame(operation.operationId, chain.operationId, `${chain.chainId}.hardwareOperation.operationId`);
+  assertSame(operation.projectId, chain.projectId, `${chain.chainId}.hardwareOperation.projectId`);
+  assertSame(operation.environment, chain.environment, `${chain.chainId}.hardwareOperation.environment`);
+  assert.ok(operationStatuses.has(operation.status), `${chain.chainId}.hardwareOperation.status is invalid`);
+  assertTimestamp(operation.requestedAt, `${chain.chainId}.hardwareOperation.requestedAt`);
+  assertTimestamp(operation.updatedAt, `${chain.chainId}.hardwareOperation.updatedAt`);
+
+  for (const field of ["startedAt", "completedAt"]) {
+    if (Object.hasOwn(operation, field)) {
+      assertTimestamp(operation[field], `${chain.chainId}.hardwareOperation.${field}`);
+    }
+  }
+
+  if (chain.agentSessionId) {
+    assertSame(operation.agentSessionId, chain.agentSessionId, `${chain.chainId}.hardwareOperation.agentSessionId`);
+  }
+  if (chain.workerSessionId) {
+    assertSame(operation.workerSessionId, chain.workerSessionId, `${chain.chainId}.hardwareOperation.workerSessionId`);
+  }
+}
+
+function validateAuditEvents(chain, auditEvents) {
+  assert.ok(Array.isArray(auditEvents), `${chain.chainId}.auditEvents must be an array`);
+  assert.ok(auditEvents.length >= 2, `${chain.chainId}.auditEvents must include operation and evidence audit events`);
+  assertUnique(
+    auditEvents.map((event) => event.auditId),
+    `${chain.chainId}.auditId values`
+  );
+
+  for (const [index, event] of auditEvents.entries()) {
+    const label = `${chain.chainId}.auditEvents[${index}]`;
+    assertObject(event, label);
+    assertRequired(event, auditEventRequired, label);
+
+    for (const field of ["auditId", "traceId", "actorId", "targetId", "projectId", "operationId"]) {
+      assertId(event[field], `${label}.${field}`);
+    }
+
+    assertSame(event.traceId, chain.traceId, `${label}.traceId`);
+    assertSame(event.projectId, chain.projectId, `${label}.projectId`);
+    assertSame(event.operationId, chain.operationId, `${label}.operationId`);
+    assertSame(event.environment, chain.environment, `${label}.environment`);
+    assert.ok(actorTypes.has(event.actorType), `${label}.actorType is invalid`);
+    assert.match(event.action, actionPattern, `${label}.action must be dotted`);
+    assert.equal(typeof event.targetType, "string", `${label}.targetType must be a string`);
+    assertServiceId(event.serviceId, `${label}.serviceId`);
+    assert.ok(auditOutcomes.has(event.outcome), `${label}.outcome is invalid`);
+    assertTimestamp(event.occurredAt, `${label}.occurredAt`);
+
+    if (Object.hasOwn(event, "gatewaySessionId")) {
+      assertSame(event.gatewaySessionId, chain.gatewaySessionId, `${label}.gatewaySessionId`);
+    }
+    if (chain.workerSessionId && Object.hasOwn(event, "workerSessionId")) {
+      assertSame(event.workerSessionId, chain.workerSessionId, `${label}.workerSessionId`);
+    }
+  }
+
+  assert.ok(
+    auditEvents.some((event) => event.targetType === "hardware_operation" && event.targetId === chain.operationId),
+    `${chain.chainId} must audit the hardware operation`
+  );
+}
+
+function validateTraceEvents(chain, traceEvents, auditIds) {
+  assert.ok(Array.isArray(traceEvents), `${chain.chainId}.traceEvents must be an array`);
+  assert.ok(traceEvents.length >= 1, `${chain.chainId}.traceEvents must not be empty`);
+  assertUnique(
+    traceEvents.map((event) => event.traceEventId),
+    `${chain.chainId}.traceEventId values`
+  );
+
+  for (const [index, event] of traceEvents.entries()) {
+    const label = `${chain.chainId}.traceEvents[${index}]`;
+    assertObject(event, label);
+    assertRequired(event, traceEventRequired, label);
+
+    for (const field of ["traceEventId", "traceId", "projectId", "operationId"]) {
+      assertId(event[field], `${label}.${field}`);
+    }
+
+    assertSame(event.traceId, chain.traceId, `${label}.traceId`);
+    assertSame(event.projectId, chain.projectId, `${label}.projectId`);
+    assertSame(event.operationId, chain.operationId, `${label}.operationId`);
+    assertSame(event.environment, chain.environment, `${label}.environment`);
+    assertServiceId(event.serviceId, `${label}.serviceId`);
+    assert.ok(traceLevels.has(event.level), `${label}.level is invalid`);
+    assert.equal(typeof event.message, "string", `${label}.message must be a string`);
+    assert.ok(event.message.length > 0, `${label}.message must not be empty`);
+    assertTimestamp(event.occurredAt, `${label}.occurredAt`);
+
+    if (chain.agentSessionId) {
+      assertSame(event.agentSessionId, chain.agentSessionId, `${label}.agentSessionId`);
+    }
+    if (chain.workerSessionId) {
+      assertSame(event.workerSessionId, chain.workerSessionId, `${label}.workerSessionId`);
+    }
+    if (event.metadata?.auditId) {
+      assert.ok(auditIds.has(event.metadata.auditId), `${label}.metadata.auditId must reference same-chain audit`);
+    }
+  }
+}
+
+async function validateEvidenceRecords(chain, evidenceRecords, auditEvents) {
+  assert.ok(Array.isArray(evidenceRecords), `${chain.chainId}.evidenceRecords must be an array`);
+  assert.ok(evidenceRecords.length >= 1, `${chain.chainId}.evidenceRecords must not be empty`);
+  assertUnique(
+    evidenceRecords.map((record) => record.evidenceId),
+    `${chain.chainId}.evidenceId values`
+  );
+
+  const auditsById = new Map(auditEvents.map((event) => [event.auditId, event]));
+
+  for (const [index, record] of evidenceRecords.entries()) {
+    const label = `${chain.chainId}.evidenceRecords[${index}]`;
+    assertObject(record, label);
+    assertRequired(record, evidenceRecordRequired, label);
+
+    for (const field of ["evidenceId", "projectId", "operationId"]) {
+      assertId(record[field], `${label}.${field}`);
+    }
+
+    assertSame(record.projectId, chain.projectId, `${label}.projectId`);
+    assertSame(record.operationId, chain.operationId, `${label}.operationId`);
+    assertSame(record.environment, chain.environment, `${label}.environment`);
+    assert.ok(evidenceKinds.has(record.kind), `${label}.kind is invalid`);
+    assertServiceId(record.serviceId, `${label}.serviceId`);
+    assertTimestamp(record.createdAt, `${label}.createdAt`);
+    assertObject(record.metadata, `${label}.metadata`);
+    assertSame(record.metadata.traceId, chain.traceId, `${label}.metadata.traceId`);
+    assertId(record.metadata.producedByAuditId, `${label}.metadata.producedByAuditId`);
+
+    const producerAudit = auditsById.get(record.metadata.producedByAuditId);
+    assert.ok(producerAudit, `${label}.metadata.producedByAuditId must reference same-chain audit`);
+    assert.equal(producerAudit.targetType, "evidence_record", `${label} producer audit must target evidence_record`);
+    assert.equal(producerAudit.targetId, record.evidenceId, `${label} producer audit must target this evidenceId`);
+
+    if (chain.agentSessionId) {
+      assertSame(record.agentSessionId, chain.agentSessionId, `${label}.agentSessionId`);
+      assertSame(record.metadata.agentSessionId, chain.agentSessionId, `${label}.metadata.agentSessionId`);
+    }
+    if (chain.workerSessionId) {
+      assertSame(record.workerSessionId, chain.workerSessionId, `${label}.workerSessionId`);
+      assertSame(record.metadata.workerSessionId, chain.workerSessionId, `${label}.metadata.workerSessionId`);
+    }
+
+    await assertArtifact(record, label);
+  }
+}
+
+async function validateFixture({ relativePath, doc }) {
+  assertObject(doc, relativePath);
+  assertRequired(doc, rootRequired, relativePath);
+
+  for (const field of ["chainId", "projectId", "operationId", "traceId"]) {
+    assertId(doc[field], `${relativePath}.${field}`);
+  }
+
+  assert.equal(doc.schemaVersion, 1, `${relativePath}.schemaVersion must be 1`);
+  assert.ok(scenarios.has(doc.scenario), `${relativePath}.scenario is not recognized`);
+  assert.equal(doc.environment, ENVIRONMENT_DEV, `${relativePath}.environment must be dev`);
+
+  for (const field of ["gatewaySessionId", "resourceId", "capabilityId", "agentSessionId", "workerSessionId"]) {
+    if (Object.hasOwn(doc, field)) {
+      assertId(doc[field], `${relativePath}.${field}`);
+    }
+  }
+
+  if (doc.scenario === "agent-automation-closed-loop") {
+    assertId(doc.agentSessionId, `${relativePath}.agentSessionId`);
+    assertId(doc.workerSessionId, `${relativePath}.workerSessionId`);
+  }
+
+  validateHardwareOperation(doc, doc.hardwareOperation);
+  validateAuditEvents(doc, doc.auditEvents);
+
+  const auditIds = new Set(doc.auditEvents.map((event) => event.auditId));
+  validateTraceEvents(doc, doc.traceEvents, auditIds);
+  await validateEvidenceRecords(doc, doc.evidenceRecords, doc.auditEvents);
+}
+
+const fixtures = await parseFixtures();
+
+assert.ok(fixtures.length >= 2, "expected at least two MVP evidence chain fixtures");
+
+const scenarioSet = new Set(fixtures.map(({ doc }) => doc.scenario));
+for (const scenario of scenarios) {
+  assert.ok(scenarioSet.has(scenario), `missing ${scenario} fixture`);
+}
+
+for (const fixture of fixtures) {
+  await validateFixture(fixture);
+}
+
+const evidenceCount = fixtures.reduce((count, { doc }) => count + doc.evidenceRecords.length, 0);
+console.log(`validated ${fixtures.length} evidence chain fixtures and ${evidenceCount} evidence records`);