Optimize XYZAC motion updates and persist power-off recovery

2026-08-29 04:52:44 +08:00
parent a97971ea19
commit f6e545018e
17 changed files with 479 additions and 74 deletions
--- a/coverage/xyzac-trt-recovery.report.json
+++ b/coverage/xyzac-trt-recovery.report.json
@@ -65,15 +65,15 @@
    },
    {
      "path": "web/worker/sim-session.mjs",
-      "sha256": "4f674200bfcca9af6bc2c83017329355b88307d0749ebb5c9d0fc8eaecaa2349"
+      "sha256": "a676086169205f16e25c142cb97e7cfac493ea58852cec93b799797f09637845"
    },
    {
      "path": "web/worker/wasm-program-runtime.mjs",
-      "sha256": "60da7b953ac4ee2659f2b05c6bb93b58c8d0c2c4b56363f6a93e44aab7aebb02"
+      "sha256": "6bc403380cfecdb4a05abf0918681b7d64acc97fb948ce7f4f73f554d51df6c4"
    }
  ],
  "release_status": "STOP_RELEASE",
-  "report_sha256": "51beb4f92ebaa633816bdbdd1bea3bc0bd918488bb7173c4082683f06f3ed88d",
+  "report_sha256": "3792c52132374430266cd4671a7001c0f5665cbd594ccd64cd2cc78ec39e50f5",
  "required_checkpoint_fields": [
    "context_id",
    "simulation_tick",
--- a/coverage/xyzac-trt-tool-preview.report.json
+++ b/coverage/xyzac-trt-tool-preview.report.json
@@ -74,7 +74,7 @@
    },
    {
      "path": "web/worker/sim-session.mjs",
-      "sha256": "4f674200bfcca9af6bc2c83017329355b88307d0749ebb5c9d0fc8eaecaa2349"
+      "sha256": "a676086169205f16e25c142cb97e7cfac493ea58852cec93b799797f09637845"
    },
    {
      "path": "web/worker/test_xyzac_exact_preview.mjs",
@@ -82,19 +82,19 @@
    },
    {
      "path": "web/worker/wasm-program-runtime.mjs",
-      "sha256": "60da7b953ac4ee2659f2b05c6bb93b58c8d0c2c4b56363f6a93e44aab7aebb02"
+      "sha256": "6bc403380cfecdb4a05abf0918681b7d64acc97fb948ce7f4f73f554d51df6c4"
    },
    {
      "path": "web/worker/wasm-motion-queue.mjs",
-      "sha256": "85b53bf7a31b9b1f1e7e76dad4bf29aabb36defcf6344d34bbb192c157a80764"
+      "sha256": "ddc215a111e3966357fde967a770a5ba0233b2ddf9d55e663a6c04cdd83b716a"
    },
    {
      "path": "web/worker/wasm-xyzac-io.mjs",
-      "sha256": "692dfb4c869130fd4a0ee78a500a54817e326991f2a5ac23a91059136d41eabd"
+      "sha256": "07c9bc5b365d5bdbb5e23e319e71b807986f1b603b1533508b0004e2c3929265"
    },
    {
      "path": "web/worker/wasm-xyzac-device-io.mjs",
-      "sha256": "1d813d59048afb6854b6fd7783dc86f65bf37ccc46f0d4f592b56cbe044211a5"
+      "sha256": "6963277d64bf6d7780bb8014c4491c90c4961db9345cb8066b3933957dbda17d"
    },
    {
      "path": "web/worker/test_xyzac_machine_sequence.mjs",
@@ -102,7 +102,7 @@
    },
    {
      "path": "web/react/src/App.tsx",
-      "sha256": "2c9aaa252c734a3885d41364cf87f969bf9b58780137e8240906f5be0745b22c"
+      "sha256": "25ccd89e22f43464e23c5920da96b780b0ca4fdb9632f5b1d84a48c37e894f44"
    },
    {
      "path": "web/react/src/styles.css",
@@ -383,7 +383,7 @@
    }
  },
  "release_status": "STOP_RELEASE",
-  "report_sha256": "d7447aab0398ac572599ecd7b50f24bf29a1751c0f1723f89eac9dadd1308302",
+  "report_sha256": "e5823f9c3ddba1217a808c401fb23a8b2cdb93a4242633245c8fc0407aa69911",
  "schema": "xyzac-trt-tool-preview-report.v1",
  "status": "verified",
  "task_id": "RTCP-10-TOOL-PREVIEW",
--- a/coverage/xyzac-trt-wasm-authority-audit.report.json
+++ b/coverage/xyzac-trt-wasm-authority-audit.report.json
@@ -128,10 +128,10 @@
      "source_slice": "AXIS-XYZAC-PROGRAM-MDI",
      "sources": [
        {
-          "lines": "122-846",
+          "lines": "122-1000",
          "path": "web/worker/sim-session.mjs",
          "role": "session-authority-routing",
-          "sha256": "4f674200bfcca9af6bc2c83017329355b88307d0749ebb5c9d0fc8eaecaa2349",
+          "sha256": "a676086169205f16e25c142cb97e7cfac493ea58852cec93b799797f09637845",
          "status": "resolved",
          "symbol": "new ProgramRunner"
        },
@@ -161,10 +161,10 @@
          "symbol": "export class MotionState"
        },
        {
-          "lines": "122-846",
+          "lines": "122-1000",
          "path": "web/worker/sim-session.mjs",
          "role": "session-authority-routing",
-          "sha256": "4f674200bfcca9af6bc2c83017329355b88307d0749ebb5c9d0fc8eaecaa2349",
+          "sha256": "a676086169205f16e25c142cb97e7cfac493ea58852cec93b799797f09637845",
          "status": "resolved",
          "symbol": "new ProgramRunner"
        }
@@ -186,10 +186,10 @@
          "symbol": "export class AuthoritativeRuntime"
        },
        {
-          "lines": "122-846",
+          "lines": "122-1000",
          "path": "web/worker/sim-session.mjs",
          "role": "session-authority-routing",
-          "sha256": "4f674200bfcca9af6bc2c83017329355b88307d0749ebb5c9d0fc8eaecaa2349",
+          "sha256": "a676086169205f16e25c142cb97e7cfac493ea58852cec93b799797f09637845",
          "status": "resolved",
          "symbol": "new ProgramRunner"
        }
@@ -205,7 +205,7 @@
    "recovery": "Chromium SIGKILL/profile-reopen, corruption detection and Firefox OPFS round-trip are verified"
  },
  "release_status": "STOP_RELEASE",
-  "report_sha256": "a294fdb56b21d9a8bddca753229d41b045e3b7887a1cf2f5e255c32e2da1fabd",
+  "report_sha256": "0995970fa99ce6ac0736710bebd35782e4cf4ab60600a72c5baa3966314e1f5d",
  "scans": {
    "js_gcode_matches": [
      {
@@ -274,17 +274,17 @@
        "text": "const result = call(this.core, \"sim_interpreter_execute\", \"number\", [\"number\", \"number\", \"number\"], [this.interpreter, this.blockBuffer, bytes.length]);"
      },
      {
-        "line": 1553,
+        "line": 1733,
        "path": "web/worker/sim-session.mjs",
        "text": "const result = this.xyzacProgram.executeBlock(block);"
      },
      {
-        "line": 1572,
+        "line": 1752,
        "path": "web/worker/sim-session.mjs",
        "text": "const result = this.program.executeBlock(block);"
      },
      {
-        "line": 188,
+        "line": 197,
        "path": "web/worker/wasm-program-runtime.mjs",
        "text": "executeBlock(block) {"
      }
@@ -292,7 +292,7 @@
    "opfs_writer_matches": [
      {
        "line": 1,
-        "path": "web/react/dist/assets/sim-worker-entry-DqcdiXWu.js",
+        "path": "web/react/dist/assets/sim-worker-entry-CyL7D-EC.js",
        "text": "(function(){var e=(()=>{var e=self.location.href;return(function(t){t||={};var t=t===void 0?{}:t,n,r;t.ready=new Promise(function(e,t){n=e,r=t});var i=Object.assign({},t),a=[],o=typeof window==`object`,s=typeof importScripts==`function`;typ"
      },
      {
@@ -1492,11 +1492,11 @@
      }
    ],
    "react": {
-      "file_count": 19,
+      "file_count": 20,
      "files": [
        {
          "path": "web/react/src/App.tsx",
-          "sha256": "2c9aaa252c734a3885d41364cf87f969bf9b58780137e8240906f5be0745b22c"
+          "sha256": "25ccd89e22f43464e23c5920da96b780b0ca4fdb9632f5b1d84a48c37e894f44"
        },
        {
          "path": "web/react/src/ThreeMachineView.tsx",
@@ -1530,9 +1530,13 @@
          "path": "web/react/src/main.tsx",
          "sha256": "421d99e6173741894a6ec5bdbf1d7da519f25c346a842892ddd00110401721d8"
        },
+        {
+          "path": "web/react/src/power-off-checkpoint-storage.ts",
+          "sha256": "2aea7f0d2818170989d87c5532e4fb89ad62c51d8c643dd023183c03141deca5"
+        },
        {
          "path": "web/react/src/protocol.ts",
-          "sha256": "a4f3b12ec4615c00973e1617849b40e9e3441369f18e28a86434495b154f9112"
+          "sha256": "2c3f37b078fdbf39a07fd6f66c92a669b2b98f591b211820faa8828f70df3519"
        },
        {
          "path": "web/react/src/sim-worker-entry.ts",
@@ -1544,7 +1548,7 @@
        },
        {
          "path": "web/react/src/store.ts",
-          "sha256": "929aba2af3291aefb4e79f500ec6567f7b7e3f1dc91b68bf67aa8224ba9a41ee"
+          "sha256": "899f8c4e7ce512b91375ed47289d4a9f2b5146504acde4e23d0587018d7ec766"
        },
        {
          "path": "web/react/src/test_xyzac_threejs.mjs",
@@ -1560,7 +1564,7 @@
        },
        {
          "path": "web/react/src/worker-client.ts",
-          "sha256": "47fcfc52acd5ce6e5dbbd91cf9da45aa5a089a3172da6414a347de5039e36737"
+          "sha256": "4aee1bca0e6580760e08549dc0dfa7771e57513bb18e19c9471ff263f8af15ee"
        },
        {
          "path": "web/react/src/xyzac-panel-contract.ts",
@@ -1576,7 +1580,7 @@
    "react_opfs_matches": [],
    "react_wasm_matches": [],
    "worker": {
-      "file_count": 125,
+      "file_count": 126,
      "files": [
        {
          "path": "web/worker/authoritative-runtime.mjs",
@@ -1652,7 +1656,7 @@
        },
        {
          "path": "web/worker/sim-session.mjs",
-          "sha256": "4f674200bfcca9af6bc2c83017329355b88307d0749ebb5c9d0fc8eaecaa2349"
+          "sha256": "a676086169205f16e25c142cb97e7cfac493ea58852cec93b799797f09637845"
        },
        {
          "path": "web/worker/sim-task.mjs",
@@ -2006,6 +2010,10 @@
          "path": "web/worker/test_xyzac_rtcp.mjs",
          "sha256": "bb62b28ea9ecae7328c16ed65ba013a68cabd421bea58929d30fe9271c4e6d77"
        },
+        {
+          "path": "web/worker/test_xyzac_runtime_followups.mjs",
+          "sha256": "0d56d8331906d20a67a3c9686bf754be1c231d5392e4426b5b2d881c9120d36b"
+        },
        {
          "path": "web/worker/test_xyzac_session.mjs",
          "sha256": "76cd74a09a0318a33d70529f7c5b9cad25fd0daebd6dd8bb05f87b42626858ef"
@@ -2048,19 +2056,19 @@
        },
        {
          "path": "web/worker/wasm-motion-queue.mjs",
-          "sha256": "85b53bf7a31b9b1f1e7e76dad4bf29aabb36defcf6344d34bbb192c157a80764"
+          "sha256": "ddc215a111e3966357fde967a770a5ba0233b2ddf9d55e663a6c04cdd83b716a"
        },
        {
          "path": "web/worker/wasm-program-runtime.mjs",
-          "sha256": "60da7b953ac4ee2659f2b05c6bb93b58c8d0c2c4b56363f6a93e44aab7aebb02"
+          "sha256": "6bc403380cfecdb4a05abf0918681b7d64acc97fb948ce7f4f73f554d51df6c4"
        },
        {
          "path": "web/worker/wasm-xyzac-device-io.mjs",
-          "sha256": "1d813d59048afb6854b6fd7783dc86f65bf37ccc46f0d4f592b56cbe044211a5"
+          "sha256": "6963277d64bf6d7780bb8014c4491c90c4961db9345cb8066b3933957dbda17d"
        },
        {
          "path": "web/worker/wasm-xyzac-io.mjs",
-          "sha256": "692dfb4c869130fd4a0ee78a500a54817e326991f2a5ac23a91059136d41eabd"
+          "sha256": "07c9bc5b365d5bdbb5e23e319e71b807986f1b603b1533508b0004e2c3929265"
        },
        {
          "path": "web/worker/wasm-xyzac-kinematics.mjs",
@@ -2086,10 +2094,10 @@
  "scope": "selected_xyzac_simulation_only",
  "sources": [
    {
-      "lines": "122-846",
+      "lines": "122-1000",
      "path": "web/worker/sim-session.mjs",
      "role": "session-authority-routing",
-      "sha256": "4f674200bfcca9af6bc2c83017329355b88307d0749ebb5c9d0fc8eaecaa2349",
+      "sha256": "a676086169205f16e25c142cb97e7cfac493ea58852cec93b799797f09637845",
      "status": "resolved",
      "symbol": "new ProgramRunner"
    },
@@ -2134,10 +2142,10 @@
      "symbol": "export class SimTask"
    },
    {
-      "lines": "58-58",
+      "lines": "62-62",
      "path": "web/worker/wasm-motion-queue.mjs",
      "role": "wasm-motion-authority",
-      "sha256": "85b53bf7a31b9b1f1e7e76dad4bf29aabb36defcf6344d34bbb192c157a80764",
+      "sha256": "ddc215a111e3966357fde967a770a5ba0233b2ddf9d55e663a6c04cdd83b716a",
      "status": "resolved",
      "symbol": "export class WasmMotionQueue"
    },
@@ -2158,10 +2166,10 @@
      "symbol": "createModule"
    },
    {
-      "lines": "49-49",
+      "lines": "66-66",
      "path": "web/react/src/worker-client.ts",
      "role": "react-worker-boundary",
-      "sha256": "47fcfc52acd5ce6e5dbbd91cf9da45aa5a089a3172da6414a347de5039e36737",
+      "sha256": "4aee1bca0e6580760e08549dc0dfa7771e57513bb18e19c9471ff263f8af15ee",
      "status": "resolved",
      "symbol": "postMessage"
    },
@@ -2182,26 +2190,26 @@
      "symbol": "createSyncAccessHandle"
    },
    {
-      "lines": "47-47",
+      "lines": "56-56",
      "path": "web/worker/wasm-program-runtime.mjs",
      "role": "wasm-program-authority",
-      "sha256": "60da7b953ac4ee2659f2b05c6bb93b58c8d0c2c4b56363f6a93e44aab7aebb02",
+      "sha256": "6bc403380cfecdb4a05abf0918681b7d64acc97fb948ce7f4f73f554d51df6c4",
      "status": "resolved",
      "symbol": "export class WasmProgramRuntime"
    },
    {
-      "lines": "39-39",
+      "lines": "46-46",
      "path": "web/worker/wasm-xyzac-io.mjs",
      "role": "wasm-hal-io-tool-probe-authority",
-      "sha256": "692dfb4c869130fd4a0ee78a500a54817e326991f2a5ac23a91059136d41eabd",
+      "sha256": "07c9bc5b365d5bdbb5e23e319e71b807986f1b603b1533508b0004e2c3929265",
      "status": "resolved",
      "symbol": "export class WasmXyzacIo"
    },
    {
-      "lines": "39-39",
+      "lines": "44-44",
      "path": "web/worker/wasm-xyzac-device-io.mjs",
      "role": "wasm-device-io-authority",
-      "sha256": "1d813d59048afb6854b6fd7783dc86f65bf37ccc46f0d4f592b56cbe044211a5",
+      "sha256": "6963277d64bf6d7780bb8014c4491c90c4961db9345cb8066b3933957dbda17d",
      "status": "resolved",
      "symbol": "export class WasmXyzacDeviceIo"
    }
--- a/coverage/xyzac-trt-wasm-only-release-gate.report.json
+++ b/coverage/xyzac-trt-wasm-only-release-gate.report.json
@@ -96,7 +96,7 @@
  "failure_samples": [],
  "input": {
    "path": "coverage/xyzac-trt-web-wasm-parity.report.json",
-    "sha256": "1ef84b02927a83c4221c11ecd896ac9a3a8d4ec1febc5363c6088ef04202a84f"
+    "sha256": "df18bbb72ac8e97af9bdf310203c181e8d7a9cf2843121e39ecd3832f08569b0"
  },
  "known_blockers": [
    "STOP_RELEASE is intentional until an owner authorizes scope expansion"
@@ -104,7 +104,7 @@
  "outputs": [],
  "release_decision": "selected_case_verified_but_release_stopped_by_scope_exclusions",
  "release_status": "STOP_RELEASE",
-  "report_sha256": "98269d8e9f60e22cc65c1eceff0ad714a614d368bdec9b20b14048db7114ce7f",
+  "report_sha256": "c4ea0158e4527823915b678f4fbc0667bba20fe3eff25cd7427358d2b3571b3b",
  "schema": "xyzac-trt-wasm-only-release-gate.v1",
  "status": "verified",
  "task_id": "RELEASE-00"
--- a/coverage/xyzac-trt-web-wasm-parity.report.json
+++ b/coverage/xyzac-trt-web-wasm-parity.report.json
@@ -91,22 +91,22 @@
  },
  "release_status": "STOP_RELEASE",
  "report_hashes": {
-    "coverage/xyzac-trt-gate-matrix.report.json": "6b1d7fa299ceaf6d9a355fc3d201dd872b586e8cbd3042f886b6be9ffa990603",
+    "coverage/xyzac-trt-gate-matrix.report.json": "3a0dd402abd95e79243e0f61e62819d595110ac6d1c3ea2a3b2251424718ba86",
    "coverage/xyzac-trt-hal-tool-alarm.report.json": "666fb1273c2471cd5869aea83e847a657309ee8cb4915713e25f4a99c94b3943",
    "coverage/xyzac-trt-manual-control.report.json": "bd38d4f20322ae3e246438740b3e35827ab2ac6b7b16b8cee22920d2c24c1847",
    "coverage/xyzac-trt-program-preview.report.json": "c4db73f5ebe63e26921425d44c9e914ca453300a54f51b9da05d709a9e68cf15",
    "coverage/xyzac-trt-protocol-react.report.json": "af78f0fd639fca95c5406b8afdcf5305225d97aba448637745bd5a941aa19689",
-    "coverage/xyzac-trt-recovery.report.json": "4452efdf6de6975221f4944bda53688bbb5be5b256525cf0d4f108408d8191da",
+    "coverage/xyzac-trt-recovery.report.json": "96df470c39326eab1979bd86669fb894335185806015479d586711f67c19ee05",
    "coverage/xyzac-trt-rtcp.report.json": "b1562d6d2c9cd5144c7c8c9b334bd8bf67919ea7297f103ec67cb32773608d08",
    "coverage/xyzac-trt-source-slice-inventory.report.json": "bf5f3fd36e1943e0dc42bafb2ed195fad147bcb3e56a8d208d7f01a3641829de",
    "coverage/xyzac-trt-startup.report.json": "56e040b645bcefc3d6c57244cb2d3aba16f421ff5137089d9c3336970dfd968b",
    "coverage/xyzac-trt-threejs.report.json": "5172d7118c555fca5f92bcb443b9c259ea0225346482558d4c33ef8a4f8da5cb",
-    "coverage/xyzac-trt-tool-preview.report.json": "09b670a1c952d0629a19bce1cf584a37b92bacb1d6a5c1430fc939cd2668a3ea",
+    "coverage/xyzac-trt-tool-preview.report.json": "c1643894bf1f2f1e49f43052731bef461ceaaf307d170e4877ac251d16e37013",
    "coverage/xyzac-trt-trace-parity.report.json": "6c6b3500bc1189ff68513b74f0e5144879c3af7641349cb61737191303b76950",
-    "coverage/xyzac-trt-wasm-authority-audit.report.json": "4f5431e951c4384c90e4ef31988189dc4f1018ddfc9d0f5e76e8f89ac09557be",
+    "coverage/xyzac-trt-wasm-authority-audit.report.json": "f0d1de5dc69141fc85756b37d4c2a69ed3a8071b43962a5bd549f6465d94f3de",
    "coverage/xyzac-trt-workflow.report.json": "9d0ed087b17ec14c906f4268d2d616dbc3800da03f731376b2ef9ae44ca5c6e7"
  },
-  "report_sha256": "8c182cef79f750228660479587d5fa12675479dc898ba353f52e57e63b604dfb",
+  "report_sha256": "59b7792f766f45b0dfc2f59829d3932d8dfa75097c890ef58c41030583c11178",
  "schema": "xyzac-trt-web-wasm-parity-report.v1",
  "source_coverage": {
    "axis_keyboard": 10,
--- a/web/app/worker-client.mjs
+++ b/web/app/worker-client.mjs
@@ -1,11 +1,43 @@
 export const CONTEXT_ID = "linuxcnc-2.10.0-pre0-wasm-m1-py-c1";
 export const PROTOCOL_SCHEMA = 1;
+const POWER_OFF_CHECKPOINT_KEY = "linuxcnc-web-wasm:xyzac-power-off-checkpoint";
 let CLIENT_INSTANCE = 0;

 function isObject(value) {
  return value !== null && typeof value === "object" && !Array.isArray(value);
 }

+function persistPowerOffCheckpoint(message) {
+  const payload = isObject(message?.payload) ? message.payload : {};
+  if (message.kind !== "COMMAND_RESULT" || payload.status !== "verified" || payload.command !== "POWER" || payload.active !== false || !isObject(payload.recovery_checkpoint)) return;
+  try { globalThis.localStorage?.setItem(POWER_OFF_CHECKPOINT_KEY, JSON.stringify(payload.recovery_checkpoint)); } catch { /* checkpoint remains visible in the response */ }
+}
+
+function attachPowerOffCheckpoint(payload) {
+  if (!isObject(payload)) return payload;
+  try {
+    const raw = globalThis.localStorage?.getItem(POWER_OFF_CHECKPOINT_KEY);
+    return raw ? { ...payload, recovery_checkpoint: JSON.parse(raw) } : payload;
+  } catch { return payload; }
+}
+
+function clearPowerOffCheckpoint(message) {
+  const payload = isObject(message?.payload) ? message.payload : {};
+  if (message.kind !== "COMMAND_RESULT" || payload.status !== "verified" || payload.command !== "POWER" || payload.active !== true) return;
+  try { globalThis.localStorage?.removeItem(POWER_OFF_CHECKPOINT_KEY); } catch { /* cleanup is best effort */ }
+}
+
+function commandError(message) {
+  const payload = isObject(message?.payload) ? message.payload : {};
+  const reason = payload.reason ?? payload.gate_reason ?? payload.message_key ?? payload.code ?? "worker_error";
+  return Object.assign(new Error(String(reason)), {
+    code: payload.code ?? "worker_error",
+    reason: payload.reason ?? payload.gate_reason ?? null,
+    message_key: payload.message_key ?? null,
+    response: message,
+  });
+}
+
 export class WorkerClient {
  constructor({ worker = null, workerFactory = null, contextId = CONTEXT_ID, sessionId = null, timeoutMs = 10000, maxPending = 64 } = {}) {
    this.contextId = contextId;
@@ -32,6 +64,9 @@ export class WorkerClient {
  }

  #receive(message) {
+    const persistence = persistPowerOffCheckpoint(message);
+    if (persistence && isObject(message?.payload)) message.payload.recovery_persistence = persistence;
+    clearPowerOffCheckpoint(message);
    this.#emit(message);
    if (!isObject(message)) return;
    const operationId = message.operation_id ?? message.payload?.operation_id;
@@ -41,9 +76,7 @@ export class WorkerClient {
    this.pending.delete(operationId ?? `seq:${message.seq}`);
    if (operationId) this.completed.set(operationId, message);
    if (message.kind === "ERROR" || message.payload?.status === "error" || message.payload?.status === "blocked") {
-      const error = new Error(message.payload?.message_key ?? message.payload?.code ?? "worker_error");
-      error.response = message;
-      pending.reject(error);
+      pending.reject(commandError(message));
    } else pending.resolve(message);
  }

@@ -68,7 +101,7 @@ export class WorkerClient {
      seq,
      kind,
      ...(operationId ? { operation_id: operationId } : {}),
-      payload,
+      payload: kind === "LOAD_WORKSPACE" ? attachPowerOffCheckpoint(payload) : payload,
    };
    let resolvePromise;
    let rejectPromise;
--- a/web/react/src/App.tsx
+++ b/web/react/src/App.tsx
@@ -153,8 +153,8 @@ export function App() {
  const trajectory = [...(planner?.queue ?? []), ...(planner?.active ? [planner.active] : [])];
  const stopRunTimer = () => { if (runTimer.current) { clearInterval(runTimer.current); runTimer.current = null; } };
  const stopJogTimer = () => { if (jogTimer.current) { clearInterval(jogTimer.current); jogTimer.current = null; } };
-  const startJogTimer = () => { if (jogTimer.current) return; jogTimer.current = setInterval(() => { if (jogStepPending.current) return; jogStepPending.current = true; operationController.execute("SIM_STEP", { cycles: 1 }, { state: axisState, gate: false }).catch(() => undefined).finally(() => { jogStepPending.current = false; }); }, 50); };
-  const startRunTimer = () => { if (runTimer.current) return; runTimer.current = setInterval(() => { if (runStepPending.current) return; runStepPending.current = true; operationController.execute("SIM_STEP", { cycles: 5 }, { state: axisState, gate: false }).catch(() => undefined).finally(() => { runStepPending.current = false; }); }, 50); };
+  const startJogTimer = () => { if (jogTimer.current) return; jogTimer.current = setInterval(() => { if (jogStepPending.current) return; jogStepPending.current = true; operationController.execute("SIM_STEP", { cycles: 1, response: "motion_delta" }, { state: axisState, gate: false }).catch(() => undefined).finally(() => { jogStepPending.current = false; }); }, 50); };
+  const startRunTimer = () => { if (runTimer.current) return; runTimer.current = setInterval(() => { if (runStepPending.current) return; runStepPending.current = true; operationController.execute("SIM_STEP", { cycles: 5, response: "motion_delta" }, { state: axisState, gate: false }).catch(() => undefined).finally(() => { runStepPending.current = false; }); }, 50); };
  const dispatch = (kind: string, payload: Record<string, unknown> = {}, gate = true, action: string | null = null): Promise<void> => {
    setCommandStatus(`${kind} pending`);
    const pending = operationController.execute(kind, payload, { state: axisState, gate, ...(action ? { action } : {}) });
--- a/web/react/src/power-off-checkpoint-storage.ts
+++ b/web/react/src/power-off-checkpoint-storage.ts
@@ -0,0 +1,40 @@
+import type { MessageEnvelope } from "./protocol";
+
+const STORAGE_KEY = "linuxcnc-web-wasm:xyzac-power-off-checkpoint";
+
+function payloadOf(message: MessageEnvelope): Record<string, unknown> {
+  return message.payload && typeof message.payload === "object" ? message.payload as Record<string, unknown> : {};
+}
+
+export function persistPowerOffCheckpoint(message: MessageEnvelope): { status: string; storage: string; reason?: string } | null {
+  const payload = payloadOf(message);
+  const checkpoint = payload.recovery_checkpoint;
+  if (message.kind !== "COMMAND_RESULT" || payload.status !== "verified" || payload.command !== "POWER" || payload.active !== false || !checkpoint || typeof checkpoint !== "object") return null;
+  try {
+    if (!globalThis.localStorage) return { status: "blocked", storage: "browser_local_storage", reason: "local_storage_unavailable" };
+    globalThis.localStorage.setItem(STORAGE_KEY, JSON.stringify(checkpoint));
+    return { status: "verified", storage: "browser_local_storage" };
+  } catch (error) {
+    return { status: "blocked", storage: "browser_local_storage", reason: error instanceof Error ? error.message : String(error) };
+  }
+}
+
+export function attachPersistedPowerOffCheckpoint(payload: unknown): unknown {
+  if (!payload || typeof payload !== "object" || Array.isArray(payload)) return payload;
+  try {
+    const raw = globalThis.localStorage?.getItem(STORAGE_KEY);
+    if (!raw) return payload;
+    const checkpoint = JSON.parse(raw);
+    return { ...(payload as Record<string, unknown>), recovery_checkpoint: checkpoint };
+  } catch {
+    return payload;
+  }
+}
+
+export function clearPersistedPowerOffCheckpoint(message: MessageEnvelope): void {
+  const payload = payloadOf(message);
+  if (message.kind !== "COMMAND_RESULT" || payload.status !== "verified" || payload.command !== "POWER" || payload.active !== true) return;
+  try { globalThis.localStorage?.removeItem(STORAGE_KEY); } catch { /* storage cleanup is best effort */ }
+}
+
+export { STORAGE_KEY };
--- a/web/react/src/protocol.ts
+++ b/web/react/src/protocol.ts
@@ -42,6 +42,7 @@ export type SimSnapshotV1 = {
  simulation_tick: number;
  state_hash: string;
  task?: { state: string; mode: string; interp_state?: string; current_line?: number | null };
+  program?: Record<string, unknown> | null;
  motion?: MotionSnapshot;
  wasm_motion?: Record<string, unknown>;
  authoritative?: { state_hash?: string; planner?: TrajectorySnapshot; kinematics?: Record<string, unknown> };
@@ -56,6 +57,8 @@ export type SimSnapshotV1 = {
  panel_snapshot?: PanelSnapshotV1;
  configuration?: Record<string, unknown> | null;
  visual?: PanelSnapshotV1["visual"];
+  motion_sample?: { tick?: number; pose?: Record<string, number>; joints?: number[]; active_segment_id?: number; active_progress?: number };
+  snapshot_mode?: "full" | "motion_delta";
  kinematics?: XyzacKinematicsSnapshot;
  xyzac?: XyzacCapabilitySnapshot;
  gates?: Record<string, { action: string; enabled: boolean; reason: string }>;
--- a/web/react/src/store.ts
+++ b/web/react/src/store.ts
@@ -56,6 +56,41 @@ function payload<T>(message: MessageEnvelope): T {

 function projection(result: Record<string, unknown>, message: MessageEnvelope, previous: FrontendState) {
  const panel = result.panel_snapshot as PanelSnapshotV1 | undefined;
+  const delta = result.motion_sample as { tick?: number; pose?: Record<string, number>; joints?: number[]; active_segment_id?: number; active_progress?: number } | undefined;
+  if (!panel && delta && previous.snapshot) {
+    const pose = delta.pose ?? {};
+    const joints = Array.isArray(delta.joints) ? [...delta.joints] : previous.snapshot.motion?.joints ?? [];
+    const visual = previous.snapshot.visual ? {
+      ...previous.snapshot.visual,
+      pose: { ...previous.snapshot.visual.pose, ...pose },
+      joints,
+      ...(delta.active_segment_id !== undefined ? { active_segment_id: delta.active_segment_id } : {}),
+      ...(delta.active_progress !== undefined ? { active_progress: delta.active_progress } : {}),
+      ...(Array.isArray(result.motion_trace) ? { motion_trace: result.motion_trace } : {}),
+    } : previous.snapshot.visual;
+    const nextSnapshot = {
+      ...previous.snapshot,
+      simulation_tick: message.simulation_tick ?? delta.tick ?? previous.snapshot.simulation_tick,
+      state_hash: String(result.state_hash ?? previous.snapshot.state_hash),
+      task: (result.task as SimSnapshotV1["task"]) ?? previous.snapshot.task,
+      program: (result.program as Record<string, unknown>) ?? previous.snapshot.program,
+      motion: {
+        ...previous.snapshot.motion,
+        axes: [Number(pose.x ?? previous.snapshot.motion?.axes?.[0] ?? 0), Number(pose.y ?? previous.snapshot.motion?.axes?.[1] ?? 0), Number(pose.z ?? previous.snapshot.motion?.axes?.[2] ?? 0)],
+        joints,
+      },
+      wasm_motion: (result.wasm_motion as Record<string, unknown>) ?? previous.snapshot.wasm_motion,
+      ...(visual ? { visual } : {}),
+    } satisfies SimSnapshotV1;
+    return {
+      snapshot: nextSnapshot,
+      toolpath: previous.toolpath,
+      task: (result.task as Record<string, unknown>) ?? previous.task,
+      program: (result.program as Record<string, unknown>) ?? previous.program,
+      axisState: (result.axis_state as AxisStateView) ?? previous.axisState,
+      gates: (result.gates as FrontendState["gates"]) ?? previous.gates,
+    };
+  }
  if (panel?.schema === "axis-panel-snapshot.v1") {
    const visualSegments = (Array.isArray(panel.visual.toolpath) ? panel.visual.toolpath : previous.toolpath)
      .filter((segment) => segment && typeof segment === "object" && Number.isSafeInteger((segment as { id?: unknown }).id ?? 0))
@@ -178,7 +213,8 @@ export function reduceFrontendState(state: FrontendState, message: MessageEnvelo
      const projected = projection(value, message, state);
      const taskState = String((value.task as Record<string, unknown> | undefined)?.state ?? "").toUpperCase();
      const status = ["ESTOP", "FAULT"].includes(taskState) ? "blocked" : "error";
-      return { ...base, status, error: { code: String(value.code ?? "worker_error"), message: JSON.stringify(value) }, ...projected };
+      const readable = value.reason ?? value.gate_reason ?? value.message_key ?? value.code ?? "worker_error";
+      return { ...base, status, error: { code: String(value.code ?? "worker_error"), message: String(readable) }, ...projected };
    }
    default: return base;
  }
--- a/web/react/src/worker-client.ts
+++ b/web/react/src/worker-client.ts
@@ -1,7 +1,20 @@
 import { CONTEXT_ID, PROTOCOL_SCHEMA, isEnvelope, type MessageEnvelope } from "./protocol";
+import { attachPersistedPowerOffCheckpoint, clearPersistedPowerOffCheckpoint, persistPowerOffCheckpoint } from "./power-off-checkpoint-storage";

 type Listener = (message: MessageEnvelope) => void;

+function commandError(message: MessageEnvelope): Error {
+  const payload = message.payload && typeof message.payload === "object" ? message.payload as Record<string, unknown> : {};
+  const error = new Error(String(payload.reason ?? payload.gate_reason ?? payload.message_key ?? payload.code ?? "worker_error"));
+  Object.assign(error, {
+    code: String(payload.code ?? "worker_error"),
+    reason: payload.reason ?? payload.gate_reason ?? null,
+    message_key: payload.message_key ?? null,
+    response: message,
+  });
+  return error;
+}
+
 export class ReactWorkerClient {
  private readonly worker: Worker;
  private readonly contextId: string;
@@ -19,11 +32,14 @@ export class ReactWorkerClient {
    this.sessionId = sessionId;
    this.worker.onmessage = (event: MessageEvent<unknown>) => {
      if (!isEnvelope(event.data)) return;
+      const persistence = persistPowerOffCheckpoint(event.data);
+      if (persistence && event.data.payload && typeof event.data.payload === "object") Object.assign(event.data.payload, { recovery_persistence: persistence });
+      clearPersistedPowerOffCheckpoint(event.data);
      for (const listener of this.listeners) listener(event.data);
      const pending = this.pending.get(event.data.seq);
      if (pending) {
        this.pending.delete(event.data.seq);
-        if (event.data.kind === "ERROR" || event.data.payload && typeof event.data.payload === "object" && (event.data.payload as { status?: string }).status === "blocked") pending.reject(new Error(String((event.data.payload as { code?: string }).code ?? "worker_error")));
+        if (event.data.kind === "ERROR" || event.data.payload && typeof event.data.payload === "object" && (event.data.payload as { status?: string }).status === "blocked") pending.reject(commandError(event.data));
        else pending.resolve(event.data);
      }
    };
@@ -45,7 +61,8 @@ export class ReactWorkerClient {
  subscribe(listener: Listener): () => void { this.listeners.add(listener); return () => this.listeners.delete(listener); }

  send(kind: string, payload: unknown = {}, operationId?: string): Promise<MessageEnvelope> {
-    const message: MessageEnvelope = { schema_version: PROTOCOL_SCHEMA, kind, context_id: this.contextId, session_id: this.sessionId, seq: ++this.sequence, ...(operationId ? { operation_id: operationId } : {}), payload };
+    const nextPayload = kind === "LOAD_WORKSPACE" ? attachPersistedPowerOffCheckpoint(payload) : payload;
+    const message: MessageEnvelope = { schema_version: PROTOCOL_SCHEMA, kind, context_id: this.contextId, session_id: this.sessionId, seq: ++this.sequence, ...(operationId ? { operation_id: operationId } : {}), payload: nextPayload };
    return new Promise((resolve, reject) => { this.pending.set(message.seq, { resolve, reject }); this.worker.postMessage(message); });
  }

--- a/web/worker/sim-session.mjs
+++ b/web/worker/sim-session.mjs
@@ -149,7 +149,44 @@ export class SimSession {
    // WASM pose samples into every 10 ms step response; the frontend retains
    // the canonical path from PROGRAM_LOAD/PROGRAM_RESTART.
    const lightweightXyzacStep = input.kind === "SIM_STEP" && Boolean(this.xyzacProgram);
-    const panelSnapshot = this.panelSnapshot({ task, program, input, tick, motionTrace: statePayload.motion_trace, includeToolpath: !lightweightXyzacStep, includeConfiguration: !lightweightXyzacStep, includeStableRuntime: !lightweightXyzacStep });
+    const currentMotion = this.wasmMotion.read();
+    const completedMotion = program.status === 4 && currentMotion.state?.queue_depth === 0;
+    const motionDelta = lightweightXyzacStep && input.payload?.response === "motion_delta" && !completedMotion;
+    const panelSnapshot = motionDelta ? null : this.panelSnapshot({ task, program, input, tick, motionTrace: statePayload.motion_trace, includeToolpath: !lightweightXyzacStep, includeConfiguration: !lightweightXyzacStep, includeStableRuntime: !lightweightXyzacStep });
+    const compactProgram = motionDelta ? {
+      schema: program.schema,
+      source: program.source,
+      status: program.status,
+      program_status: program.program_status,
+      loaded: program.loaded,
+      current_line: program.current_line,
+      line: program.line,
+      path: program.path,
+      source_hash: program.source_hash,
+      state_hash: program.state_hash,
+    } : null;
+    const trace = Array.isArray(statePayload.motion_trace) ? statePayload.motion_trace : [];
+    const motionSample = motionDelta ? (trace.at(-1) ?? {
+      tick,
+      pose: currentMotion.state?.position ?? null,
+      joints: [],
+      active_segment_id: currentMotion.state?.active_id ?? 0,
+      active_progress: currentMotion.state?.progress ?? 0,
+    }) : null;
+    const responsePayload = motionDelta ? {
+      status: statePayload.status,
+      cycles: statePayload.cycles,
+      motion_trace: trace,
+      motion_sample: motionSample,
+      snapshot_mode: "motion_delta",
+      motion_authority: statePayload.motion_authority ?? this.motionAuthority,
+      task,
+      task_authority: statePayload.task_authority ?? this.task.authority(),
+      wasm_motion: statePayload.wasm_motion ?? currentMotion,
+      motion: statePayload.motion ?? this.motionProjection(),
+      program: compactProgram,
+      state_hash: statePayload.state_hash ?? null,
+    } : statePayload;
    return {
      schema_version: PROTOCOL_SCHEMA,
      kind,
@@ -159,12 +196,12 @@ export class SimSession {
      ...(text(input.operation_id) ? { operation_id: input.operation_id } : {}),
      simulation_tick: tick,
      payload: {
-        ...statePayload,
-        panel_snapshot: panelSnapshot,
-        motion_authority: statePayload.motion_authority ?? this.motionAuthority,
-        task_authority: statePayload.task_authority ?? this.task.authority(),
+        ...responsePayload,
+        ...(panelSnapshot ? { panel_snapshot: panelSnapshot } : {}),
+        motion_authority: responsePayload.motion_authority ?? this.motionAuthority,
+        task_authority: responsePayload.task_authority ?? this.task.authority(),
        ...(!lightweightXyzacStep ? { wasm_home_limit: statePayload.wasm_home_limit ?? this.wasmHomeLimit.read() } : {}),
-        axis_state: axisState({ task, program, motion: this.motionProjection(), devices: this.wasmDeviceProjection(), io: this.xyzacIo ? this.xyzacIo.export() : {}, device_io: this.xyzacIo ? this.xyzacIo.export() : this.deviceIo.export(), action: input.kind, payload: input.payload ?? {} }),
+        axis_state: axisState({ task, program, motion: this.motionProjection(), devices: {}, io: this.xyzacIo?.canonical?.() ?? {}, device_io: this.xyzacDeviceIo?.canonical?.() ?? this.deviceIo.export(), action: input.kind, payload: input.payload ?? {} }),
      },
    };
  }
@@ -516,6 +553,123 @@ export class SimSession {
    });
  }

+  createPowerOffCheckpoint() {
+    const checkpoint = this.createCheckpoint();
+    const state = structuredClone(checkpoint.state);
+    // Operation history and replay snapshots are useful for an explicit
+    // recovery command, but are redundant for a power-off restart. Omitting
+    // them keeps the browser durable record bounded during long JOG runs.
+    delete state.ledger;
+    const compact = {
+      schema: "xyzac-power-off-checkpoint.v1",
+      context_id: this.contextId,
+      simulation_tick: checkpoint.simulation_tick,
+      state,
+      state_hash: fnv1a64(state),
+    };
+    return { ...compact, checkpoint_hash: fnv1a64(compact) };
+  }
+
+  restoreCompactPowerOff(record, transportSeq) {
+    if (!record || record.schema !== "xyzac-power-off-checkpoint.v1" || record.context_id !== this.contextId || !record.state) return { status: "blocked", code: "runtime_checkpoint_schema", reason: "power_off_checkpoint_schema_invalid" };
+    if (fnv1a64(record.state) !== record.state_hash || fnv1a64(Object.fromEntries(Object.entries(record).filter(([key]) => key !== "checkpoint_hash"))) !== record.checkpoint_hash) return { status: "blocked", code: "runtime_checkpoint_hash", reason: "power_off_checkpoint_hash_mismatch" };
+    if (!Number.isSafeInteger(transportSeq) || transportSeq < 1 || !Number.isSafeInteger(record.simulation_tick) || record.simulation_tick < 0) return { status: "blocked", code: "runtime_checkpoint_range", reason: "power_off_checkpoint_range_invalid" };
+    const state = record.state;
+    const liveTimeline = this.timeline.export();
+    const liveLedger = this.ledger;
+    const liveOperations = [...this.operations.values()];
+    try {
+      if (!this.xyzacProgram || !state.program?.source_text) throw new Error("power_off_program_missing");
+      const loaded = this.xyzacProgram.load(state.program.source_text, state.program.path ?? null);
+      if (loaded.status !== "verified") throw new Error(loaded.code);
+      const subroutines = this.loadXyzacSubroutines(state.program.path ?? null);
+      if (subroutines.status !== "verified") throw new Error(subroutines.code);
+      if (this.xyzacProgram.restoreState(state.program).status === "error") throw new Error("power_off_program_restore_failed");
+      if (state.wasm_motion) this.wasmMotion.restoreState(state.wasm_motion);
+      if (state.wasm_home_limit) this.wasmHomeLimit.restoreState(state.wasm_home_limit);
+      if (state.device_io && this.xyzacDeviceIo) this.xyzacDeviceIo.restoreState(state.device_io);
+      if (state.devices && this.xyzacIo) this.xyzacIo.restoreState(state.devices);
+      if (state.kinematics && this.xyzacKinematics) this.xyzacKinematics.restoreState(state.kinematics);
+      if (state.task) {
+        const task = { ...state.task, session_id: this.sessionId, seq: transportSeq, simulation_tick: record.simulation_tick };
+        delete task.state_hash;
+        task.state_hash = fnv1a64(task);
+        this.task.restore(task);
+      }
+      if (state.scheduler) this.scheduler.restore(state.scheduler);
+      this.plc = new PlcRuntime(); if (state.plc) this.plc.restore(state.plc);
+      this.hal = new HalRuntime(); if (state.hal_runtime?.schema === "sim_hal_runtime.v1") this.hal.restore(state.hal_runtime);
+      this.configurationBatch = new ConfigurationBatchRuntime({ context_id: this.contextId }); if (state.configuration_batch) this.configurationBatch.restore(state.configuration_batch);
+      this.ioAck = new IoAckTracker(); if (state.io_ack) this.ioAck.restore(state.io_ack);
+      this.callbacks = new PythonCallbacks(); if (state.callbacks) this.callbacks.restore(state.callbacks);
+      this.configurationState = state.configuration ?? this.configurationState;
+      this.halState = state.hal ?? this.halState;
+      this.previewState = state.preview ?? this.previewState;
+      this.python = new PythonBridge(); if (state.python) this.python.restoreState(state.python);
+      const liveEvents = liveTimeline.events.events;
+      const rebasedEvents = liveEvents.map((event, index) => index === liveEvents.length - 1 ? { ...event, tick: record.simulation_tick } : event);
+      this.timeline = new ReplayTimeline({ schema: liveTimeline.schema, events: { ...liveTimeline.events, tick: record.simulation_tick, events: rebasedEvents }, snapshots: { schema: "snapshot.v1", snapshots: [] } });
+      this.tick = record.simulation_tick;
+      const protocolTick = call(this.core, "sim_protocol_set_tick", record.simulation_tick);
+      if (protocolTick !== 0) throw new Error(`protocol_tick_${protocolTick}`);
+      this.timeline.checkpoint(transportSeq, record.simulation_tick, this.stateForCheckpoint(), null);
+      this.operations = new Map(liveOperations.map((operation) => [operation.operation_id, operation]));
+      this.ledger = liveLedger;
+      return { status: "verified", storage: "browser_client_storage", checkpoint_hash: record.checkpoint_hash, simulation_tick: record.simulation_tick, rebased_seq: transportSeq };
+    } catch (error) {
+      this.ledger = liveLedger;
+      this.operations = new Map(liveOperations.map((operation) => [operation.operation_id, operation]));
+      return { status: "blocked", code: "runtime_checkpoint_restore_failed", reason: String(error?.message ?? error) };
+    }
+  }
+
+  restorePersistedPowerOff(checkpoint, transportSeq) {
+    if (!checkpoint || !Number.isSafeInteger(transportSeq) || transportSeq < 1) return { status: "blocked", code: "runtime_checkpoint_input_invalid", reason: "checkpoint_or_sequence_invalid" };
+    if (checkpoint.schema === "xyzac-power-off-checkpoint.v1") return this.restoreCompactPowerOff(checkpoint, transportSeq);
+    const liveTimeline = this.timeline.export();
+    const liveLedger = this.ledger;
+    const liveOperations = [...this.operations.values()];
+    // A browser restart creates a new transport session id. Adapt only the
+    // task identity and recompute checkpoint digests before restoring so the
+    // WASM task canonical (which was initialized with the new id) remains
+    // self-consistent.
+    let checkpointForRestore = checkpoint;
+    if (checkpoint.state?.task?.session_id && checkpoint.state.task.session_id !== this.sessionId) {
+      checkpointForRestore = structuredClone(checkpoint);
+      checkpointForRestore.state.task.session_id = this.sessionId;
+      checkpointForRestore.state.task.state_hash = fnv1a64(Object.fromEntries(Object.entries(checkpointForRestore.state.task).filter(([key]) => key !== "state_hash")));
+      checkpointForRestore.state_hash = fnv1a64(checkpointForRestore.state);
+      const unsigned = Object.fromEntries(Object.entries(checkpointForRestore).filter(([key]) => key !== "checkpoint_hash"));
+      checkpointForRestore.checkpoint_hash = fnv1a64(unsigned);
+    }
+    const restored = this.restoreCheckpoint(checkpointForRestore);
+    if (restored.status !== "recovered") return restored;
+    const restoredTick = this.tick;
+    const restoredTask = this.task.export();
+    const rebasedTask = { ...restoredTask, session_id: this.sessionId, seq: transportSeq, simulation_tick: restoredTick };
+    delete rebasedTask.state_hash;
+    rebasedTask.state_hash = fnv1a64(rebasedTask);
+    try {
+      this.task.restore(rebasedTask);
+      const liveEvents = liveTimeline.events.events;
+      const rebasedEvents = liveEvents.map((event, index) => index === liveEvents.length - 1 ? { ...event, tick: restoredTick } : event);
+      this.timeline = new ReplayTimeline({
+        schema: liveTimeline.schema,
+        events: { ...liveTimeline.events, tick: restoredTick, events: rebasedEvents },
+        snapshots: { schema: "snapshot.v1", snapshots: [] },
+      });
+      this.tick = restoredTick;
+      const protocolTick = call(this.core, "sim_protocol_set_tick", restoredTick);
+      if (protocolTick !== 0) throw new Error(`protocol_tick_${protocolTick}`);
+      this.timeline.checkpoint(transportSeq, restoredTick, this.stateForCheckpoint(), null);
+      this.operations = new Map(liveOperations.map((operation) => [operation.operation_id, operation]));
+      this.ledger = liveLedger;
+      return { status: "verified", storage: "browser_client_storage", checkpoint_hash: checkpoint.checkpoint_hash, simulation_tick: restoredTick, rebased_seq: transportSeq };
+    } catch (error) {
+      return { status: "blocked", code: "runtime_checkpoint_rebase_failed", reason: String(error?.message ?? error) };
+    }
+  }
+
  exportTrace() {
    const latest = this.timeline.snapshots.latest();
    if (!latest || latest.seq !== this.timeline.events.cursor || latest.tick !== this.timeline.events.tick) {
@@ -946,6 +1100,9 @@ export class SimSession {
        code: "axis_gate",
        message_key: gate.reason,
        gate_reason: gate.reason,
+        reason: gate.reason,
+        error_code: "axis_gate",
+        source: "linuxcnc-wasm-worker",
        retryable: false,
        operation_id: input.operation_id ?? null,
      });
@@ -1067,6 +1224,8 @@ export class SimSession {
      case "POWER": {
        if (this.xyzacProgram) {
          const result = this.xyzacIo.command("POWER", input.payload ?? {});
+          let recoveryCheckpoint = null;
+          let recoveryPersistence = { status: "skipped", reason: "power_on" };
          if (result.status === "verified") {
            if (input.payload?.active === false) {
              /* LinuxCNC emcTaskSetState(OFF) aborts motion, clears the
@@ -1084,9 +1243,17 @@ export class SimSession {
                if (["READY", "RUNNING", "PAUSED"].includes(this.task.state.state)) this.task.transition("STOPPED");
              }
            } catch { /* the WASM IO state remains authoritative */ }
+            if (input.payload?.active === false) {
+              try {
+                recoveryCheckpoint = this.createPowerOffCheckpoint();
+                recoveryPersistence = { status: "checkpoint_ready", persistence: "browser_client_storage" };
+              } catch (error) {
+                recoveryPersistence = { status: "blocked", code: "runtime_checkpoint_create_failed", reason: String(error?.message ?? error) };
+              }
+            }
            if (this.xyzacDeviceIo) this.xyzacDeviceIo.command("INTERLOCK_RESET", input.payload ?? {}, input.operation_id);
          }
-          return finish(this.envelope(result.status === "verified" ? "COMMAND_RESULT" : "ERROR", input, { ...result, command: input.kind, active: input.payload?.active === true, task: this.task.export(), device_io: this.xyzacIo.export(), operation_id: input.operation_id ?? null }), result.status === "verified" ? "verified" : "failed");
+          return finish(this.envelope(result.status === "verified" ? "COMMAND_RESULT" : "ERROR", input, { ...result, command: input.kind, active: input.payload?.active === true, task: this.task.export(), device_io: this.xyzacIo.export(), ...(recoveryCheckpoint ? { recovery_checkpoint: recoveryCheckpoint } : {}), recovery_persistence: recoveryPersistence, operation_id: input.operation_id ?? null }), result.status === "verified" ? "verified" : "failed");
        }
        if (input.payload?.active !== true) return finish(this.error(input, "power_state", "power_active_required"), "failed");
        const result = this.xyzacIo ? this.xyzacIo.command("POWER", input.payload ?? {}) : this.devices.command("IO_RECOVER", input.payload ?? {});
@@ -1210,12 +1377,25 @@ export class SimSession {
          if (kinematics.status === "blocked") return finish(this.envelope("ERROR", input, { status: "blocked", code: kinematics.code, kinematics: this.authoritative.export() }), "failed");
        }
        const loadResult = startupLoaded ? 0 : call(this.core, "sim_load_workspace", rootPath);
+        let powerOffRecovery = null;
+        if (loadResult === 0 && input.payload?.recovery_checkpoint && this.xyzacProgram) {
+          const restored = this.restorePersistedPowerOff(input.payload.recovery_checkpoint, input.seq);
+          if (restored.status !== "verified") return finish(this.envelope("ERROR", input, {
+            status: "blocked",
+            code: restored.code ?? "runtime_checkpoint_restore_failed",
+            message_key: restored.reason ?? restored.code ?? "runtime_checkpoint_restore_failed",
+            reason: restored.reason ?? restored.code ?? "runtime_checkpoint_restore_failed",
+            recovery: restored,
+          }), "failed");
+          powerOffRecovery = restored;
+        }
        return loadResult === 0 ? finish(this.envelope("COMMAND_RESULT", input, {
          status: "verified",
          command: input.kind,
          motion_authority: this.motionAuthority,
          state_hash: this.task.hash(),
          task: this.task.export(),
+          ...(powerOffRecovery ? { power_off_recovery: powerOffRecovery } : {}),
          ...(this.configurationState?.schema === "configuration-startup-runtime.v1" ? { configuration: this.configurationState } : {}),
        })) : finish(this.coreError(input, loadResult, "sim_load_workspace"), "failed");
      }
--- a/web/worker/test_xyzac_runtime_followups.mjs
+++ b/web/worker/test_xyzac_runtime_followups.mjs
@@ -0,0 +1,62 @@
+import assert from "node:assert/strict";
+import { readFile } from "node:fs/promises";
+import createModule from "../../build-wasm/linuxcnc-sim-core.js";
+import { loadSimulationCase, toWorkerConfiguration } from "../workspace/sim-case-loader.mjs";
+import { SimSession, CONTEXT_ID } from "./sim-session.mjs";
+
+const CASE = "linuxcnc/configs/sim/axis/vismach/5axis/table-rotary-tilting/xyzac-trt.ini";
+const PROGRAM = "G21 G90\nG0 X0 Y0 Z10 A0 C0\nG1 X20 Y5 Z5 A30 C45 F100\nM2\n";
+const fetchImpl = async (url) => {
+  try { const body = await readFile(new URL(`../../${String(url).replace(/^\//, "")}`, import.meta.url)); return { ok: true, text: async () => body.toString("utf8") }; }
+  catch { return { ok: false, text: async () => "" }; }
+};
+const bundle = await loadSimulationCase({ path: CASE, fetchImpl });
+const wasmBinary = await readFile(new URL("../../build-wasm/linuxcnc-sim-core.wasm", import.meta.url));
+
+async function open(sessionId) {
+  const core = await createModule({ wasmBinary });
+  const session = new SimSession(core, { sessionId });
+  const base = { schema_version: 1, context_id: CONTEXT_ID, session_id: sessionId };
+  let seq = 0;
+  const send = (kind, payload = {}) => session.accept({ ...base, kind, seq: ++seq, operation_id: `${sessionId}-${seq}`, payload });
+  send("HELLO"); send("SESSION_ATTACH");
+  assert.equal(send("LOAD_WORKSPACE", { root_path: "/workspace", configuration: toWorkerConfiguration(bundle) }).payload.status, "verified");
+  return { session, send };
+}
+
+const first = await open("xyzac-followups-a");
+const blocked = first.send("MDI_EXECUTE", { block: "G0 X1" });
+assert.equal(blocked.kind, "ERROR");
+assert.equal(blocked.payload.code, "axis_gate");
+assert.equal(blocked.payload.reason, "xyzac_machine_off");
+assert.equal(blocked.payload.message_key, "xyzac_machine_off");
+first.send("POWER", { active: true });
+first.send("HOME", { all: true });
+first.send("PROGRAM_LOAD", { source: PROGRAM, path: "followups.ngc" });
+first.send("PROGRAM_RUN");
+const compact = first.send("SIM_STEP", { cycles: 1, response: "motion_delta" });
+assert.equal(compact.payload.snapshot_mode, "motion_delta");
+assert.equal(compact.payload.panel_snapshot, undefined);
+assert.ok(compact.payload.motion_sample?.pose);
+const full = first.send("SIM_STEP", { cycles: 1 });
+const compactBytes = Buffer.byteLength(JSON.stringify(compact));
+const fullBytes = Buffer.byteLength(JSON.stringify(full));
+assert.ok(compactBytes < fullBytes / 2, `${compactBytes} >= ${fullBytes / 2}`);
+const off = first.send("POWER", { active: false });
+assert.equal(off.payload.recovery_checkpoint.schema, "xyzac-power-off-checkpoint.v1");
+assert.equal(off.payload.recovery_checkpoint.state.task.state, "STOPPED");
+assert.ok(Buffer.byteLength(JSON.stringify(off.payload.recovery_checkpoint)) < 512 * 1024);
+
+const second = await open("xyzac-followups-b");
+const restored = second.send("LOAD_WORKSPACE", { root_path: "/workspace", configuration: toWorkerConfiguration(bundle), recovery_checkpoint: off.payload.recovery_checkpoint });
+assert.equal(restored.payload.power_off_recovery.status, "verified");
+assert.equal(restored.payload.task.state, "STOPPED");
+assert.equal(restored.payload.panel_snapshot.program.program_status, "loaded");
+
+console.log(JSON.stringify({
+  schema: "xyzac-runtime-followups.v1",
+  status: "verified",
+  motion_delta: { compact_bytes: compactBytes, full_bytes: fullBytes, reduction_ratio: Number((1 - compactBytes / fullBytes).toFixed(3)) },
+  errors: { code: blocked.payload.code, reason: blocked.payload.reason, message_key: blocked.payload.message_key },
+  power_off_persistence: { schema: off.payload.recovery_checkpoint.schema, bytes: Buffer.byteLength(JSON.stringify(off.payload.recovery_checkpoint)), restored: restored.payload.power_off_recovery.status },
+}));
--- a/web/worker/wasm-motion-queue.mjs
+++ b/web/worker/wasm-motion-queue.mjs
@@ -7,6 +7,10 @@ const QUEUE_HEADER_BYTES = 32;
 const STATE_POSITION_BYTES = 72;
 const MOTION_QUEUE_SCHEMA = "sim_motion_queue_state.v1";
 const DEFAULT_CONTROLS = Object.freeze({ profile: 0, lookahead: 1, acceleration_limit: 1e9, jerk_limit: 1e12, paused: false });
+const MOTION_ERROR_REASONS = Object.freeze({
+  [-600]: "wasm_motion_invalid_argument", [-601]: "wasm_motion_nonfinite_value", [-602]: "wasm_motion_limit_range",
+  [-603]: "wasm_motion_invalid_state", [-604]: "wasm_motion_queue_full", [-605]: "wasm_motion_paused",
+});

 function call(core, name, returnType, argTypes, args) {
  const fn = core[`_${name}`] ?? core[name];
@@ -101,7 +105,7 @@ export class WasmMotionQueue {
    // Keep the WASM switchkins mode in the tag field; the C queue assigns id.
    ints[this.command / 4 + SEGMENT_INT_OFFSET + 3] = Number(segment.kinematics_mode ?? segment.tag ?? 0);
    const result = call(this.core, "sim_motion_enqueue", "number", ["number", "number", "number"], [this.queue, this.command, 0]);
-    return result === 0 ? { status: "verified", source_line: segment.source_line ?? null } : { status: "error", code: `wasm_motion_enqueue_${result}` };
+    return result === 0 ? { status: "verified", source_line: segment.source_line ?? null } : { status: "error", code: `wasm_motion_enqueue_${result}`, reason: MOTION_ERROR_REASONS[result] ?? `wasm_motion_enqueue_${result}`, message_key: MOTION_ERROR_REASONS[result] ?? `wasm_motion_enqueue_${result}`, source: "linuxcnc-wasm-motion" };
  }

  reset() {
@@ -183,7 +187,7 @@ export class WasmMotionQueue {
    if (!this.available) return { status: "error", code: "wasm_motion_step_-605" };
    if (this.controls.paused) return { status: "error", code: "wasm_motion_step_-605" };
    const result = call(this.core, "sim_motion_step", "number", ["number"], [this.queue]);
-    if (result !== 0) return { status: "error", code: `wasm_motion_step_${result}` };
+    if (result !== 0) return { status: "error", code: `wasm_motion_step_${result}`, reason: MOTION_ERROR_REASONS[result] ?? `wasm_motion_step_${result}`, message_key: MOTION_ERROR_REASONS[result] ?? `wasm_motion_step_${result}`, source: "linuxcnc-wasm-motion" };
    return this.read();
  }

--- a/web/worker/wasm-program-runtime.mjs
+++ b/web/worker/wasm-program-runtime.mjs
@@ -5,6 +5,15 @@ const SEGMENT_BYTES = 216;
 const POSE_BYTES = 72;
 const AXES = ["x", "y", "z", "a", "b", "c", "u", "v", "w"];
 const DEFAULT_RAPID_VELOCITY = 1000;
+const PROGRAM_ERROR_REASONS = Object.freeze({
+  [-1100]: "wasm_program_invalid_argument", [-1101]: "wasm_program_range_error", [-1102]: "wasm_program_invalid_state",
+  [-1103]: "wasm_program_control_error", [-1104]: "wasm_program_interpreter_error", [-1105]: "wasm_program_motion_error",
+});
+
+function programError(errorPrefix, result) {
+  const reason = PROGRAM_ERROR_REASONS[result] ?? `wasm_${errorPrefix}_${result}`;
+  return { status: "error", code: `wasm_${errorPrefix}_${result}`, result, reason, message_key: reason, source: "linuxcnc-wasm-sim_program" };
+}

 function call(core, name, returnType, argTypes, args) {
  const fn = core?.[`_${name}`] ?? core?.[name];
@@ -69,7 +78,7 @@ export class WasmProgramRuntime {
  invoke(name, args = [], errorPrefix = name) {
    if (!this.available) return { status: "blocked", code: "wasm_program_unavailable" };
    const result = call(this.core, name, "number", ["number", ...args.map(() => "number")], [this.pointer, ...args]);
-    return result === 0 ? { status: "verified", command: name } : { status: "error", code: `wasm_${errorPrefix}_${result}`, result };
+    return result === 0 ? { status: "verified", command: name } : { status: "error", code: `wasm_${errorPrefix}_${result}`, result, reason: PROGRAM_ERROR_REASONS[result] ?? `wasm_${errorPrefix}_${result}`, message_key: PROGRAM_ERROR_REASONS[result] ?? `wasm_${errorPrefix}_${result}`, source: "linuxcnc-wasm-sim_program" };
  }

  load(source, path = null) {
@@ -79,7 +88,7 @@ export class WasmProgramRuntime {
    this.core.HEAPU8.set(bytes, pointer);
    try {
      const result = call(this.core, "sim_program_load", "number", ["number", "number", "number"], [this.pointer, pointer, bytes.byteLength]);
-      if (result !== 0) return { status: "error", code: `wasm_program_load_${result}` };
+      if (result !== 0) return programError("program_load", result);
      const velocityResult = call(this.core, "sim_program_set_rapid_velocity", "number", ["number", "number"], [this.pointer, this.rapidVelocity]);
      if (velocityResult !== 0) return { status: "error", code: `wasm_program_rapid_velocity_${velocityResult}` };
      this.source = source;
@@ -191,7 +200,7 @@ export class WasmProgramRuntime {
    this.core.HEAPU8.set(bytes, pointer);
    try {
      const result = call(this.core, "sim_program_execute_block", "number", ["number", "number", "number"], [this.pointer, pointer, bytes.byteLength]);
-      if (result !== 0) return { status: "error", code: `wasm_program_execute_${result}` };
+      if (result !== 0) return programError("program_execute", result);
      return { status: "verified", program: this.snapshot(), motion: this.readMotion() };
    } finally { this.core._free(pointer); }
  }
--- a/web/worker/wasm-xyzac-device-io.mjs
+++ b/web/worker/wasm-xyzac-device-io.mjs
@@ -1,6 +1,11 @@
 import { fnv1a64 } from "./replay.mjs";

 const DEVICE_SCHEMA = "wasm_xyzac_device_io.v1";
+const DEVICE_ERROR_REASONS = Object.freeze({
+  [-1000]: "wasm_device_invalid_argument", [-1001]: "wasm_device_invalid_state", [-1002]: "wasm_device_range_error",
+  [-1003]: "wasm_device_estop_active", [-1004]: "wasm_device_interlock_open", [-1005]: "wasm_device_fault_active",
+  [-1006]: "wasm_device_ack_missing", [-1007]: "wasm_device_ack_timeout", [-1008]: "wasm_device_ack_invalid",
+});

 function call(core, name, returnType, argTypes, args) {
  const fn = core?.[`_${name}`] ?? core?.[name];
@@ -52,7 +57,8 @@ export class WasmXyzacDeviceIo {
  invoke(name, args = []) {
    if (!this.available) return { status: "blocked", code: "wasm_xyzac_device_io_unavailable" };
    const result = call(this.core, name, "number", ["number", ...args.map(() => "number")], [this.pointer, ...args]);
-    return result === 0 ? { status: "verified", command: name } : { status: "error", code: `wasm_${name}_${result}`, result };
+    const reason = DEVICE_ERROR_REASONS[result] ?? `wasm_${name}_${result}`;
+    return result === 0 ? { status: "verified", command: name } : { status: "error", code: `wasm_${name}_${result}`, result, reason, message_key: reason, source: "linuxcnc-wasm-device-io" };
  }

  canonical() {
--- a/web/worker/wasm-xyzac-io.mjs
+++ b/web/worker/wasm-xyzac-io.mjs
@@ -4,6 +4,13 @@ const IO_SCHEMA = "wasm_xyzac_io.v1";
 const HAL_SCHEMA = "wasm_xyzac_hal.v1";
 const POSE_BYTES = 72;
 const HAL_WRITE_ALLOWLIST = new Set(["motion.probe-input", "iocontrol.0.tool-prepared", "iocontrol.0.tool-changed", "spindle.0.speed-in", "spindle.0.at-speed"]);
+const IO_ERROR_REASONS = Object.freeze({
+  [-900]: "wasm_io_invalid_argument", [-901]: "wasm_io_range_error", [-902]: "wasm_io_invalid_state",
+  [-903]: "wasm_io_power_required", [-904]: "wasm_io_estop_active", [-905]: "wasm_io_fault_active",
+  [-906]: "wasm_io_limit_active", [-907]: "wasm_io_nonfinite_value", [-908]: "wasm_io_hal_pin_error",
+  [-909]: "wasm_io_capacity_exceeded", [-910]: "wasm_io_busy", [-911]: "wasm_io_probe_error",
+  [-912]: "wasm_io_timeout", [-913]: "wasm_io_recovery_required",
+});

 function call(core, name, returnType, argTypes, args) {
  const fn = core?.[`_${name}`] ?? core?.[name];
@@ -59,7 +66,7 @@ export class WasmXyzacIo {
    if (!this.available) return { status: "blocked", code: "wasm_xyzac_io_unavailable" };
    const result = call(this.core, name, "number", ["number", ...args.map(() => "number")], [this.pointer, ...args]);
    this.lastError = result;
-    return result === 0 ? { status: "verified", command: name } : { status: "error", code: `wasm_${name}_${result}`, result };
+    return result === 0 ? { status: "verified", command: name } : { status: "error", code: `wasm_${name}_${result}`, result, reason: IO_ERROR_REASONS[result] ?? `wasm_${name}_${result}`, message_key: IO_ERROR_REASONS[result] ?? `wasm_${name}_${result}`, source: "linuxcnc-wasm-io" };
  }

  canonical() {