diff --git a/mateclaw-ui/package.json b/mateclaw-ui/package.json
index 82fb5fff..d594fae9 100644
--- a/mateclaw-ui/package.json
+++ b/mateclaw-ui/package.json
@@ -6,9 +6,10 @@
   "description": "MateClaw - Personal AI Assistant Web Console",
   "scripts": {
     "dev": "vite",
-    "build": "node --max-old-space-size=6144 ./node_modules/vue-tsc/bin/vue-tsc.js --noEmit && node --max-old-space-size=6144 ./node_modules/vite/bin/vite.js build",
+    "build": "bash ../scripts/check-snowflake-precision.sh && node --max-old-space-size=6144 ./node_modules/vue-tsc/bin/vue-tsc.js --noEmit && node --max-old-space-size=6144 ./node_modules/vite/bin/vite.js build",
     "preview": "vite preview",
-    "lint": "eslint src --ext .ts,.vue --fix"
+    "lint": "eslint src --ext .ts,.vue --fix && bash ../scripts/check-snowflake-precision.sh",
+    "lint:precision": "bash ../scripts/check-snowflake-precision.sh"
   },
   "dependencies": {
     "@element-plus/icons-vue": "^2.3.1",
diff --git a/mateclaw-ui/src/api/index.ts b/mateclaw-ui/src/api/index.ts
index 22c098a3..1348575a 100644
--- a/mateclaw-ui/src/api/index.ts
+++ b/mateclaw-ui/src/api/index.ts
@@ -559,7 +559,10 @@ export const settingsApi = {
   // unrelated settings pages can't clobber them via partial payloads. This
   // endpoint is the only path that writes those fields unconditionally —
   // pass {defaultVisionModelId: null} here to explicitly clear a sidecar.
-  updateSidecar: (data: { defaultVisionModelId: number | null; defaultVideoModelId: number | null }) =>
+  // Model IDs are accepted as either JSON numbers or strings — Jackson
+  // coerces both into Long. The string form is preferred from the UI to
+  // sidestep JS Number precision loss on 19-digit Snowflake IDs.
+  updateSidecar: (data: { defaultVisionModelId: number | string | null; defaultVideoModelId: number | string | null }) =>
     http.put('/settings/sidecar', data),
 }
 
@@ -1042,7 +1045,10 @@ export interface TriggerSummary {
   patternType: string
   patternJson: string
   targetType: string
-  targetId: number
+  // Snowflake ID — backend serializes Long as string (ToStringSerializer).
+  // Keep the union so v-model can hold the string form without TS errors
+  // and JS Number() coercion stays out of the round-trip.
+  targetId: number | string
   payloadTemplate?: string
   rateLimitPerMin: number
   dedupWindowSecs: number
diff --git a/mateclaw-ui/src/components/workflow/StepPropertyPanel.vue b/mateclaw-ui/src/components/workflow/StepPropertyPanel.vue
index 73e58964..b7ea7b97 100644
--- a/mateclaw-ui/src/components/workflow/StepPropertyPanel.vue
+++ b/mateclaw-ui/src/components/workflow/StepPropertyPanel.vue
@@ -406,10 +406,11 @@ function onAgentSelect(e: Event) {
     patch({ agentId: undefined, agentName: undefined })
     return
   }
-  const id = Number(v)
+  // Keep the id as the raw string from the option value — Snowflake IDs
+  // exceed Number.MAX_SAFE_INTEGER, so Number(v) would silently truncate.
   const selected = props.availableAgents.find((a) => String(a.id) === v)
   patch({
-    agentId: Number.isFinite(id) ? id : undefined,
+    agentId: v,
     // Kept as a denormalized label for the canvas node; runtime resolves by agentId.
     agentName: selected?.name,
   })
diff --git a/mateclaw-ui/src/components/workflow/TriggerPatternForm.vue b/mateclaw-ui/src/components/workflow/TriggerPatternForm.vue
index d360f3f7..3d4164e8 100644
--- a/mateclaw-ui/src/components/workflow/TriggerPatternForm.vue
+++ b/mateclaw-ui/src/components/workflow/TriggerPatternForm.vue
@@ -86,10 +86,14 @@
     <template v-else-if="patternType === 'agent_lifecycle'">
       <div class="pf-field">
         <span class="pf-label">{{ t('triggers.pattern.agentId') }}</span>
+        <!-- type=text + inputmode=numeric so 19-digit Snowflake IDs aren't
+             coerced through JS Number (input[type=number] silently truncates
+             values past 2^53-1 even when v-model has no .number modifier). -->
         <input
-          v-model.number="form.agentId"
-          type="number"
-          min="0"
+          v-model.trim="form.agentId"
+          type="text"
+          inputmode="numeric"
+          pattern="\d*"
           class="pf-input"
           :placeholder="t('triggers.pattern.agentIdPlaceholder')"
           @input="emitFromForm"
@@ -113,7 +117,7 @@
     <template v-else-if="patternType === 'workflow_completion'">
       <div class="pf-field">
         <span class="pf-label">{{ t('triggers.pattern.sourceWorkflowId') }}</span>
-        <select v-model.number="form.sourceWorkflowId" class="pf-input" @change="emitFromForm">
+        <select v-model="form.sourceWorkflowId" class="pf-input" @change="emitFromForm">
           <option :value="undefined">{{ t('triggers.pattern.sourceWorkflowAny') }}</option>
           <option v-for="wf in availableWorkflows" :key="wf.id" :value="wf.id">
             #{{ wf.id }} — {{ wf.name || '(unnamed)' }}
@@ -190,9 +194,12 @@ interface FormState {
   senderEquals?: string
   contentContains?: string
   substring?: string
-  agentId?: number | null
+  // IDs are kept as strings to survive 19-digit Snowflake values through
+  // v-model without precision loss; matcher's longOrNull accepts both
+  // numeric and string forms in pattern_json.
+  agentId?: string | null
   phase?: string
-  sourceWorkflowId?: number
+  sourceWorkflowId?: string | number
   stateFilter?: string
 }
 
@@ -220,9 +227,15 @@ function loadFromJson(json: string) {
     if (typeof parsed.senderEquals === 'string') form.senderEquals = parsed.senderEquals
     if (typeof parsed.contentContains === 'string') form.contentContains = parsed.contentContains
     if (typeof parsed.substring === 'string') form.substring = parsed.substring
-    if (typeof parsed.agentId === 'number') form.agentId = parsed.agentId
+    // Accept both number and string — pattern_json may store IDs either way
+    // depending on who wrote it (matcher's longOrNull accepts both too).
+    if (typeof parsed.agentId === 'number' || typeof parsed.agentId === 'string') { // snowflake-precision-ok: explicit dual-form handling, then String()
+      form.agentId = String(parsed.agentId)
+    }
     if (typeof parsed.phase === 'string') form.phase = parsed.phase
-    if (typeof parsed.sourceWorkflowId === 'number') form.sourceWorkflowId = parsed.sourceWorkflowId
+    if (typeof parsed.sourceWorkflowId === 'number' || typeof parsed.sourceWorkflowId === 'string') { // snowflake-precision-ok: explicit dual-form handling, then String()
+      form.sourceWorkflowId = String(parsed.sourceWorkflowId)
+    }
     if (typeof parsed.stateFilter === 'string') form.stateFilter = parsed.stateFilter
   } catch (e) {
     rawError.value = (e as Error).message
@@ -247,14 +260,17 @@ function buildJsonFromForm(): string {
       if (form.substring) out.substring = form.substring
       break
     case 'agent_lifecycle':
-      if (typeof form.agentId === 'number' && !Number.isNaN(form.agentId)) {
-        out.agentId = form.agentId
+      // Emit IDs as JSON strings to preserve Snowflake precision. The
+      // matcher's longOrNull parses either form, so this stays compatible
+      // with any pattern_json written previously as a JSON number.
+      if (form.agentId != null && String(form.agentId).trim() !== '') {
+        out.agentId = String(form.agentId).trim()
       }
       if (form.phase) out.phase = form.phase
       break
     case 'workflow_completion':
-      if (typeof form.sourceWorkflowId === 'number') {
-        out.sourceWorkflowId = form.sourceWorkflowId
+      if (form.sourceWorkflowId != null && String(form.sourceWorkflowId) !== '') {
+        out.sourceWorkflowId = String(form.sourceWorkflowId)
       }
       if (form.stateFilter) out.stateFilter = form.stateFilter
       break
diff --git a/mateclaw-ui/src/composables/chat/useStream.ts b/mateclaw-ui/src/composables/chat/useStream.ts
index b4c8ec3c..7f60f3f0 100644
--- a/mateclaw-ui/src/composables/chat/useStream.ts
+++ b/mateclaw-ui/src/composables/chat/useStream.ts
@@ -227,11 +227,12 @@ export function useStream(options: UseStreamOptions): UseStreamReturn {
         return
       }
       seenEventIds.add(event.id)
-      // Track highest id for reconnect Last-Event-ID echo. String compare is
-      // fine because ids are zero-padded server-side... actually they're plain
-      // numbers, so coerce to BigInt-safe numeric compare.
-      const incoming = Number(event.id)
-      const current = lastEventId.value === null ? -1 : Number(lastEventId.value)
+      // Track highest id for reconnect Last-Event-ID echo. SSE event ids are
+      // per-conversation sequential counters issued by ChatStreamTracker — not
+      // Snowflake — so coercing through Number is safe within JS's 2^53 ceiling
+      // (a single conversation would need 9 quadrillion events to overflow).
+      const incoming = Number(event.id) // snowflake-precision-ok: SSE sequence counter
+      const current = lastEventId.value === null ? -1 : Number(lastEventId.value) // snowflake-precision-ok: SSE sequence counter
       if (!Number.isNaN(incoming) && incoming > current) {
         lastEventId.value = event.id
       }
@@ -305,7 +306,7 @@ export function useStream(options: UseStreamOptions): UseStreamReturn {
     // switch. We only inject when the dedup state is still relevant
     // (sameConv) AND we actually have an id to echo.
     if (sameConv && lastEventId.value !== null && body && body.reconnect) {
-      const numericId = Number(lastEventId.value)
+      const numericId = Number(lastEventId.value) // snowflake-precision-ok: SSE sequence counter
       if (!Number.isNaN(numericId)) {
         body = { ...body, lastEventId: numericId }
       }
diff --git a/mateclaw-ui/src/composables/useWorkflowGraph.ts b/mateclaw-ui/src/composables/useWorkflowGraph.ts
index c1ec0c7b..0f042b0f 100644
--- a/mateclaw-ui/src/composables/useWorkflowGraph.ts
+++ b/mateclaw-ui/src/composables/useWorkflowGraph.ts
@@ -28,7 +28,10 @@ import dagre from 'dagre'
 
 export interface RawStep {
   name?: string
-  agentId?: number
+  // Snowflake IDs lose precision when round-tripped through JS Number, so
+  // we treat agentId as opaque (string preferred, number tolerated for
+  // legacy JSON written before the string-id convention).
+  agentId?: string | number
   agentName?: string
   mode?: { type?: string; expression?: string; [k: string]: unknown }
   promptTemplate?: string
@@ -45,7 +48,7 @@ export interface StepNodeData {
   index: number
   name: string
   modeType: string
-  agentId?: number
+  agentId?: string | number
   agentName?: string
   promptTemplate?: string
   expression?: string
@@ -102,7 +105,9 @@ export function buildGraph(json: string): { nodes: Node<StepNodeData>[]; edges:
       index: idx,
       name: step?.name?.trim() || fallbackName(idx),
       modeType,
-      agentId: typeof step?.agentId === 'number' ? step.agentId : undefined,
+      // Accept both string (post-fix, Snowflake-safe) and number (legacy)
+      // forms; the canvas only uses this for display, so we don't normalize.
+      agentId: step?.agentId != null && step.agentId !== '' ? step.agentId : undefined,
       agentName: step?.agentName,
       promptTemplate: step?.promptTemplate,
       expression: typeof step?.mode?.expression === 'string' ? step.mode!.expression : undefined,
diff --git a/mateclaw-ui/src/views/Settings/Models/MultimodalSidecarSection.vue b/mateclaw-ui/src/views/Settings/Models/MultimodalSidecarSection.vue
index 842afc45..7a6ec1b3 100644
--- a/mateclaw-ui/src/views/Settings/Models/MultimodalSidecarSection.vue
+++ b/mateclaw-ui/src/views/Settings/Models/MultimodalSidecarSection.vue
@@ -143,7 +143,7 @@ async function loadAll() {
   }
 }
 
-async function persistSettings(payload: { defaultVisionModelId: number | null; defaultVideoModelId: number | null }) {
+async function persistSettings(payload: { defaultVisionModelId: number | string | null; defaultVideoModelId: number | string | null }) {
   // Use the dedicated sidecar endpoint so the bulk /settings PUT can keep
   // guarding vision/video keys with non-null checks (preventing unrelated
   // settings pages from clobbering this configuration via partial payloads).
@@ -159,9 +159,12 @@ async function onSaveVision() {
     // Send vision's pending value plus the *initial* (last-saved) video value
     // so saving vision never accidentally clears a video selection the user
     // may have edited but not yet committed in that card.
+    // Send IDs as the raw string from the model picker. Number() would
+    // truncate 19-digit Snowflake IDs past Number.MAX_SAFE_INTEGER; Jackson
+    // on the backend coerces the string back to Long with full precision.
     await persistSettings({
-      defaultVisionModelId: visionModelId.value ? Number(visionModelId.value) : null,
-      defaultVideoModelId: initialVideo.value ? Number(initialVideo.value) : null,
+      defaultVisionModelId: visionModelId.value ? String(visionModelId.value) : null,
+      defaultVideoModelId: initialVideo.value ? String(initialVideo.value) : null,
     })
     initialVision.value = visionModelId.value
     savedTip.value = 'vision'
@@ -178,8 +181,8 @@ async function onSaveVideo() {
   savedTip.value = null
   try {
     await persistSettings({
-      defaultVisionModelId: initialVision.value ? Number(initialVision.value) : null,
-      defaultVideoModelId: videoModelId.value ? Number(videoModelId.value) : null,
+      defaultVisionModelId: initialVision.value ? String(initialVision.value) : null,
+      defaultVideoModelId: videoModelId.value ? String(videoModelId.value) : null,
     })
     initialVideo.value = videoModelId.value
     savedTip.value = 'video'
diff --git a/mateclaw-ui/src/views/Triggers.vue b/mateclaw-ui/src/views/Triggers.vue
index c7f6d863..a0592e6b 100644
--- a/mateclaw-ui/src/views/Triggers.vue
+++ b/mateclaw-ui/src/views/Triggers.vue
@@ -118,7 +118,10 @@
                     </select>
                   </label>
                   <label>{{ t('triggers.fields.targetId') }}
-                    <select v-model.number="formState.targetId">
+                    <!-- Keep targetId as a string so 19-digit Snowflake IDs survive
+                         the v-model round trip; .number would truncate to JS's
+                         53-bit safe-integer ceiling. -->
+                    <select v-model="formState.targetId">
                       <option v-if="!availableWorkflows.length" :value="0">
                         {{ t('triggers.targetWorkflowEmpty') }}
                       </option>
@@ -208,7 +211,11 @@ interface FormState {
   patternType: string
   patternJson: string
   targetType: string
-  targetId: number
+  // Snowflake IDs arrive from the backend as strings (ToStringSerializer).
+  // Keep that string form here so v-model on the workflow select can't
+  // accidentally lose precision. The 0 sentinel covers the "no workflow
+  // available" empty state.
+  targetId: number | string
   rateLimitPerMin: number
   dedupWindowSecs: number
   botSelfFilter: boolean
diff --git a/mateclaw-ui/src/views/Wiki/components/WikiConfig.vue b/mateclaw-ui/src/views/Wiki/components/WikiConfig.vue
index e8e14f5d..329e1564 100644
--- a/mateclaw-ui/src/views/Wiki/components/WikiConfig.vue
+++ b/mateclaw-ui/src/views/Wiki/components/WikiConfig.vue
@@ -196,7 +196,10 @@ async function saveEmbeddingBinding() {
       embeddingModelId: embeddingModelId.value === '' ? null : embeddingModelId.value,
     })
     const kb: any = store.currentKB
-    kb.embeddingModelId = embeddingModelId.value === '' ? null : Number(embeddingModelId.value)
+    // Mirror the persisted value to the in-memory KB without going through
+    // Number() — Snowflake model IDs would otherwise lose their last digits
+    // (Number.MAX_SAFE_INTEGER = 2^53-1, IDs are 19 digits).
+    kb.embeddingModelId = embeddingModelId.value === '' ? null : embeddingModelId.value
   } catch (e) {
     console.error('[WikiConfig] Failed to save embedding binding', e)
   } finally {
@@ -262,9 +265,13 @@ async function saveStepModelsAndClose() {
   if (!store.currentKB) return
   savingStepModels.value = true
   try {
-    const stepMap: Record<string, number> = {}
+    // Keep model IDs as strings end-to-end. Snowflake IDs exceed
+    // Number.MAX_SAFE_INTEGER, so Number() / .map(Number) would silently
+    // corrupt the last few digits before serializing to configContent JSON.
+    // Backend parses configContent leniently — string-typed IDs are fine.
+    const stepMap: Record<string, string> = {}
     for (const key of stepKeys) {
-      if (stepModels[key]) stepMap[`heavy_ingest.${key}`] = Number(stepModels[key])
+      if (stepModels[key]) stepMap[`heavy_ingest.${key}`] = stepModels[key]
     }
     let existingConfig: any = {}
     try {
@@ -272,9 +279,9 @@ async function saveStepModelsAndClose() {
     } catch { /* not JSON */ }
     existingConfig.stepModels = Object.keys(stepMap).length > 0 ? stepMap : undefined
     existingConfig.fallbackModelIds = fallbackModelIds.value.length > 0
-      ? fallbackModelIds.value.map(Number) : undefined
+      ? [...fallbackModelIds.value] : undefined
     existingConfig.wikiDefaultModelId = wikiGlobalModelId.value
-      ? Number(wikiGlobalModelId.value) : undefined
+      ? wikiGlobalModelId.value : undefined
     await wikiApi.updateConfig(store.currentKB.id, JSON.stringify(existingConfig, null, 2))
     modelsOpen.value = false
   } catch (e) {