diff --git a/src/caller/caller-resolution.controller.ts b/src/caller/caller-resolution.controller.ts
new file mode 100644
index 0000000..112f8cd
--- /dev/null
+++ b/src/caller/caller-resolution.controller.ts
@@ -0,0 +1,26 @@
+import { Controller, Post, Body, Headers, HttpException, HttpStatus, Logger } from '@nestjs/common';
+import { CallerResolutionService } from './caller-resolution.service';
+
+@Controller('api/caller')
+export class CallerResolutionController {
+    private readonly logger = new Logger(CallerResolutionController.name);
+
+    constructor(private readonly resolution: CallerResolutionService) {}
+
+    @Post('resolve')
+    async resolve(
+        @Body('phone') phone: string,
+        @Headers('authorization') auth: string,
+    ) {
+        if (!phone) {
+            throw new HttpException('phone is required', HttpStatus.BAD_REQUEST);
+        }
+        if (!auth) {
+            throw new HttpException('Authorization header required', HttpStatus.UNAUTHORIZED);
+        }
+
+        this.logger.log(`[RESOLVE] Resolving caller: ${phone}`);
+        const result = await this.resolution.resolve(phone, auth);
+        return result;
+    }
+}
diff --git a/src/caller/caller-resolution.module.ts b/src/caller/caller-resolution.module.ts
new file mode 100644
index 0000000..c167d64
--- /dev/null
+++ b/src/caller/caller-resolution.module.ts
@@ -0,0 +1,13 @@
+import { Module } from '@nestjs/common';
+import { PlatformModule } from '../platform/platform.module';
+import { AuthModule } from '../auth/auth.module';
+import { CallerResolutionController } from './caller-resolution.controller';
+import { CallerResolutionService } from './caller-resolution.service';
+
+@Module({
+    imports: [PlatformModule, AuthModule],
+    controllers: [CallerResolutionController],
+    providers: [CallerResolutionService],
+    exports: [CallerResolutionService],
+})
+export class CallerResolutionModule {}
diff --git a/src/caller/caller-resolution.service.ts b/src/caller/caller-resolution.service.ts
new file mode 100644
index 0000000..719786b
--- /dev/null
+++ b/src/caller/caller-resolution.service.ts
@@ -0,0 +1,216 @@
+import { Injectable, Logger } from '@nestjs/common';
+import { PlatformGraphqlService } from '../platform/platform-graphql.service';
+import { SessionService } from '../auth/session.service';
+
+const CACHE_TTL = 3600; // 1 hour
+const CACHE_PREFIX = 'caller:';
+
+export type ResolvedCaller = {
+    leadId: string;
+    patientId: string;
+    firstName: string;
+    lastName: string;
+    phone: string;
+    isNew: boolean; // true if we just created the lead+patient pair
+};
+
+@Injectable()
+export class CallerResolutionService {
+    private readonly logger = new Logger(CallerResolutionService.name);
+
+    constructor(
+        private readonly platform: PlatformGraphqlService,
+        private readonly cache: SessionService,
+    ) {}
+
+    // Resolve a caller by phone number. Always returns a paired lead + patient.
+    async resolve(phone: string, auth: string): Promise<ResolvedCaller> {
+        const normalized = phone.replace(/\D/g, '').slice(-10);
+        if (normalized.length < 10) {
+            throw new Error(`Invalid phone number: ${phone}`);
+        }
+
+        // 1. Check cache
+        const cached = await this.cache.getCache(`${CACHE_PREFIX}${normalized}`);
+        if (cached) {
+            this.logger.log(`[RESOLVE] Cache hit for ${normalized}`);
+            return JSON.parse(cached);
+        }
+
+        // 2. Look up lead by phone
+        const lead = await this.findLeadByPhone(normalized, auth);
+
+        // 3. Look up patient by phone
+        const patient = await this.findPatientByPhone(normalized, auth);
+
+        let result: ResolvedCaller;
+
+        if (lead && patient) {
+            // Both exist — link them if not already linked
+            if (!lead.patientId) {
+                await this.linkLeadToPatient(lead.id, patient.id, auth);
+                this.logger.log(`[RESOLVE] Linked existing lead ${lead.id} → patient ${patient.id}`);
+            }
+            result = {
+                leadId: lead.id,
+                patientId: patient.id,
+                firstName: lead.firstName || patient.firstName,
+                lastName: lead.lastName || patient.lastName,
+                phone: normalized,
+                isNew: false,
+            };
+        } else if (lead && !patient) {
+            // Lead exists, no patient — create patient
+            const newPatient = await this.createPatient(lead.firstName, lead.lastName, normalized, auth);
+            await this.linkLeadToPatient(lead.id, newPatient.id, auth);
+            this.logger.log(`[RESOLVE] Created patient ${newPatient.id} for existing lead ${lead.id}`);
+            result = {
+                leadId: lead.id,
+                patientId: newPatient.id,
+                firstName: lead.firstName,
+                lastName: lead.lastName,
+                phone: normalized,
+                isNew: false,
+            };
+        } else if (!lead && patient) {
+            // Patient exists, no lead — create lead
+            const newLead = await this.createLead(patient.firstName, patient.lastName, normalized, patient.id, auth);
+            this.logger.log(`[RESOLVE] Created lead ${newLead.id} for existing patient ${patient.id}`);
+            result = {
+                leadId: newLead.id,
+                patientId: patient.id,
+                firstName: patient.firstName,
+                lastName: patient.lastName,
+                phone: normalized,
+                isNew: false,
+            };
+        } else {
+            // Neither exists — create both
+            const newPatient = await this.createPatient('', '', normalized, auth);
+            const newLead = await this.createLead('', '', normalized, newPatient.id, auth);
+            this.logger.log(`[RESOLVE] Created new lead ${newLead.id} + patient ${newPatient.id} for ${normalized}`);
+            result = {
+                leadId: newLead.id,
+                patientId: newPatient.id,
+                firstName: '',
+                lastName: '',
+                phone: normalized,
+                isNew: true,
+            };
+        }
+
+        // 4. Cache the result
+        await this.cache.setCache(`${CACHE_PREFIX}${normalized}`, JSON.stringify(result), CACHE_TTL);
+
+        return result;
+    }
+
+    // Invalidate cache for a phone number (call after updates)
+    async invalidate(phone: string): Promise<void> {
+        const normalized = phone.replace(/\D/g, '').slice(-10);
+        await this.cache.setCache(`${CACHE_PREFIX}${normalized}`, '', 1); // expire immediately
+    }
+
+    private async findLeadByPhone(phone10: string, auth: string): Promise<{ id: string; firstName: string; lastName: string; patientId: string | null } | null> {
+        try {
+            const data = await this.platform.queryWithAuth<{ leads: { edges: { node: any }[] } }>(
+                `{ leads(first: 200) { edges { node {
+                    id
+                    contactName { firstName lastName }
+                    contactPhone { primaryPhoneNumber }
+                    patientId
+                } } } }`,
+                undefined,
+                auth,
+            );
+
+            const match = data.leads.edges.find(e => {
+                const num = (e.node.contactPhone?.primaryPhoneNumber ?? '').replace(/\D/g, '').slice(-10);
+                return num.length >= 10 && num === phone10;
+            });
+
+            if (!match) return null;
+
+            return {
+                id: match.node.id,
+                firstName: match.node.contactName?.firstName ?? '',
+                lastName: match.node.contactName?.lastName ?? '',
+                patientId: match.node.patientId || null,
+            };
+        } catch (err: any) {
+            this.logger.warn(`[RESOLVE] Lead lookup failed: ${err.message}`);
+            return null;
+        }
+    }
+
+    private async findPatientByPhone(phone10: string, auth: string): Promise<{ id: string; firstName: string; lastName: string } | null> {
+        try {
+            const data = await this.platform.queryWithAuth<{ patients: { edges: { node: any }[] } }>(
+                `{ patients(first: 200) { edges { node {
+                    id
+                    fullName { firstName lastName }
+                    phones { primaryPhoneNumber }
+                } } } }`,
+                undefined,
+                auth,
+            );
+
+            const match = data.patients.edges.find(e => {
+                const num = (e.node.phones?.primaryPhoneNumber ?? '').replace(/\D/g, '').slice(-10);
+                return num.length >= 10 && num === phone10;
+            });
+
+            if (!match) return null;
+
+            return {
+                id: match.node.id,
+                firstName: match.node.fullName?.firstName ?? '',
+                lastName: match.node.fullName?.lastName ?? '',
+            };
+        } catch (err: any) {
+            this.logger.warn(`[RESOLVE] Patient lookup failed: ${err.message}`);
+            return null;
+        }
+    }
+
+    private async createPatient(firstName: string, lastName: string, phone: string, auth: string): Promise<{ id: string }> {
+        const data = await this.platform.queryWithAuth<{ createPatient: { id: string } }>(
+            `mutation($data: PatientCreateInput!) { createPatient(data: $data) { id } }`,
+            {
+                data: {
+                    fullName: { firstName: firstName || 'Unknown', lastName: lastName || '' },
+                    phones: { primaryPhoneNumber: `+91${phone}` },
+                    patientType: 'NEW',
+                },
+            },
+            auth,
+        );
+        return data.createPatient;
+    }
+
+    private async createLead(firstName: string, lastName: string, phone: string, patientId: string, auth: string): Promise<{ id: string }> {
+        const data = await this.platform.queryWithAuth<{ createLead: { id: string } }>(
+            `mutation($data: LeadCreateInput!) { createLead(data: $data) { id } }`,
+            {
+                data: {
+                    name: `${firstName} ${lastName}`.trim() || 'Unknown Caller',
+                    contactName: { firstName: firstName || 'Unknown', lastName: lastName || '' },
+                    contactPhone: { primaryPhoneNumber: `+91${phone}` },
+                    source: 'PHONE',
+                    status: 'NEW',
+                    patientId,
+                },
+            },
+            auth,
+        );
+        return data.createLead;
+    }
+
+    private async linkLeadToPatient(leadId: string, patientId: string, auth: string): Promise<void> {
+        await this.platform.queryWithAuth<any>(
+            `mutation($id: UUID!, $data: LeadUpdateInput!) { updateLead(id: $id, data: $data) { id } }`,
+            { id: leadId, data: { patientId } },
+            auth,
+        );
+    }
+}