diff --git a/docs/observe.md b/docs/observe.md
index 6bf241a..cec2f8f 100644
--- a/docs/observe.md
+++ b/docs/observe.md
@@ -228,12 +228,73 @@ Key constraints:
 ## Sink Implementations
 
 APOPHIS does not ship with built-in sinks. The `ObserveSink` interface lets you
-plug in any backend. Common patterns:
+plug in any backend.
 
-- **OpenTelemetry**: emit counters and histograms via `@opentelemetry/api`.
-- **pino logger**: emit structured log records via `pino.info()` / `pino.warn()`.
-- **Internal metrics service**: POST events to an internal collector endpoint.
-- **In-memory ring buffer**: capture recent events for diagnostics endpoints.
+### OpenTelemetry
+
+Export contract evaluations as OTel custom metrics alongside your existing spans and traces:
+
+```typescript
+import type { ObserveSink, ObserveEvent } from '@apophis/fastify'
+import { metrics } from '@opentelemetry/api'
+
+const meter = metrics.getMeter('apophis')
+
+const contractCounter = meter.createCounter('apophis.contract.evaluations', {
+  description: 'Number of contract evaluations',
+})
+const violationCounter = meter.createCounter('apophis.contract.violations', {
+  description: 'Number of contract violations',
+})
+const durationHistogram = meter.createHistogram('apophis.contract.duration_ms', {
+  description: 'Contract evaluation duration',
+})
+
+export const otelSink: ObserveSink = {
+  emit(event: ObserveEvent) {
+    const labels = { route: event.route, formula: event.formula }
+    contractCounter.add(1, labels)
+    if (event.type === 'contract.violation') {
+      violationCounter.add(1, labels)
+    }
+    durationHistogram.record(event.durationMs, labels)
+  },
+}
+```
+
+Register it with your Fastify app:
+
+```typescript
+await app.register(apophisPlugin, {
+  observe: { enabled: true, sinks: [otelSink] },
+})
+```
+
+APOPHIS violations now appear in your OTel metrics backend (Prometheus, Datadog, New Relic, etc.) alongside latency and error data — no custom collector needed.
+
+### Console (development / debugging)
+
+```typescript
+export const consoleSink: ObserveSink = {
+  emit(event: ObserveEvent) {
+    if (event.type === 'contract.violation') {
+      console.warn('[apophis]', event.route, event.formula, event.observed)
+    }
+  },
+}
+```
+
+### pino logger
+
+```typescript
+export function createPinoSink(logger: pino.Logger): ObserveSink {
+  return {
+    emit(event: ObserveEvent) {
+      logger[event.type === 'contract.violation' ? 'warn' : 'info'](event)
+    },
+  }
+}
+```
 
 ## Monorepo Validation
 
diff --git a/docs/verify.md b/docs/verify.md
index 84a8f6c..b30d9ef 100644
--- a/docs/verify.md
+++ b/docs/verify.md
@@ -83,7 +83,7 @@ apophis verify --profile ci --changed
 
 If no routes changed, exits 2 with a message.
 
-`--changed` is a heuristic: it maps changed file paths to routes by checking route path segments against file names. This is useful as a developer convenience, but for strict CI gating, prefer explicit `--routes` filters or full verification.
+`--changed` tracks which source file registered each route by capturing stack traces during route discovery. When a file changes, only routes registered from that file are verified. Falls back to a path-segment heuristic for routes discovered without source file metadata (e.g., `printRoutes()` fallback).
 
 ## Failure Output Format
 
diff --git a/src/cli/commands/verify/runner.ts b/src/cli/commands/verify/runner.ts
index 9d67e6b..609d7f3 100644
--- a/src/cli/commands/verify/runner.ts
+++ b/src/cli/commands/verify/runner.ts
@@ -185,23 +185,29 @@ export async function getGitChangedFiles(cwd: string): Promise<string[]> {
 }
 
 /**
- * Filter routes to only those modified in git.
+ * Filter routes to only those whose source file was modified in git.
+ * Uses sourceFile captured from stack traces during route registration.
+ * Falls back to path-segment heuristic when sourceFile is unavailable.
  */
 export async function filterChangedRoutes(
   routes: RouteContract[],
   cwd: string,
 ): Promise<RouteContract[]> {
   const changedFiles = await getGitChangedFiles(cwd)
-  
-  // Map route paths to potential file paths (heuristic)
+
   return routes.filter(route => {
+    // Prefer precise source file match
+    if (route.sourceFile) {
+      return changedFiles.some(file =>
+        route.sourceFile!.endsWith(file) || file.endsWith(route.sourceFile!)
+      )
+    }
+    // Fallback: heuristic path-segment match
     const routePath = route.path
-    // Check if any changed file might contain this route
-    return changedFiles.some(file => {
-      // Simple heuristic: check if route path segments appear in file path
-      const segments = routePath.split('/').filter(Boolean)
-      return segments.some(segment => file.includes(segment))
-    })
+    const segments = routePath.split('/').filter(Boolean)
+    return changedFiles.some(file =>
+      segments.some(segment => file.includes(segment))
+    )
   })
 }
 
diff --git a/src/domain/discovery.ts b/src/domain/discovery.ts
index 55de4c8..0a15a0c 100644
--- a/src/domain/discovery.ts
+++ b/src/domain/discovery.ts
@@ -13,6 +13,7 @@ interface CapturedRoute {
   url: string
   schema?: Record<string, unknown>
   prefix?: string
+  sourceFile?: string
 }
 
 export interface DiscoveryResult {
@@ -24,6 +25,26 @@ export interface DiscoveryResult {
 
 // WeakMap to store captured routes per Fastify instance (no memory leaks)
 const capturedRoutes = new WeakMap<object, CapturedRoute[]>()
+
+/**
+ * Extract the source file that registered a route from a stack trace.
+ * Finds the first frame outside node_modules and APOPHIS internal directories.
+ */
+function extractSourceFile(stack: string): string | undefined {
+  const lines = stack.split('\n')
+  for (let i = 3; i < lines.length; i++) {
+    const line = lines[i]
+    if (!line) continue
+    const match = line.match(/\((.*?):\d+:\d+\)/) ?? line.match(/at\s+(.*?):\d+:\d+/)
+    if (!match || !match[1]) continue
+    const filePath = match[1]
+    if (!filePath.includes('node_modules') && !filePath.includes('/apophis/') && !filePath.includes('\\apophis\\')) {
+      return filePath
+    }
+  }
+  return undefined
+}
+
 /**
  * Capture a route for discovery.
  * Called from the plugin's `onRoute` hook.
@@ -32,6 +53,7 @@ export const captureRoute = (
   instance: object,
   route: CapturedRoute
 ): void => {
+  route.sourceFile = extractSourceFile(new Error().stack ?? '')
   const existing = capturedRoutes.get(instance) ?? []
   existing.push(route)
   capturedRoutes.set(instance, existing)
@@ -140,9 +162,11 @@ export const discoverRouteDetails = (instance: DiscoverRouteDetailsInput): Disco
   const captured = capturedRoutes.get(instance)
   if (captured && captured.length > 0) {
     return {
-      routes: captured.map((route) =>
-        extractContract(route.url, route.method, route.schema)
-      ),
+      routes: captured.map((route) => {
+        const contract = extractContract(route.url, route.method, route.schema)
+        contract.sourceFile = route.sourceFile
+        return contract
+      }),
       source: 'captured',
       hasSchemaMetadata: true,
       warnings: [],
diff --git a/src/types/core.ts b/src/types/core.ts
index 92854e5..b48a8b1 100644
--- a/src/types/core.ts
+++ b/src/types/core.ts
@@ -41,6 +41,8 @@ export interface RouteContract {
   schema?: Record<string, unknown>
   /** Per-route timeout in milliseconds, extracted from schema['x-timeout']. Overrides global/plugin timeout. */
   timeout?: number
+  /** Source file that registered this route (captured from stack trace during discovery). */
+  sourceFile?: string
   /** Outbound dependency contracts for this route. Extracted from schema['x-outbound'] and normalized. */
   outbound?: readonly OutboundBinding[]
   /** Route-level variants for negotiated content-type or feature testing. Extracted from schema['x-variants']. */