diff --git a/chainlink-modsec/libmodsec/internal/verifier/doc.go b/chainlink-modsec/libmodsec/internal/verifier/doc.go
new file mode 100644
index 0000000000..9af914b740
--- /dev/null
+++ b/chainlink-modsec/libmodsec/internal/verifier/doc.go
@@ -0,0 +1,3 @@
+// Package verifier implements a service that monitors a channel for incoming
+// messages and sends attestations to a results channel.
+package verifier
diff --git a/chainlink-modsec/libmodsec/internal/verifier/interfaces.go b/chainlink-modsec/libmodsec/internal/verifier/interfaces.go
new file mode 100644
index 0000000000..9e20bd35b5
--- /dev/null
+++ b/chainlink-modsec/libmodsec/internal/verifier/interfaces.go
@@ -0,0 +1,51 @@
+package verifier
+
+import (
+	"context"
+)
+
+// Reader is an interface for reading the blockchain for new work.
+type Reader interface {
+	// Next returns a channel that will yield the next piece of work to be processed.
+	Next(ctx context.Context) <-chan Work
+
+	// Watch returns a channel that will yield all work to be processed.
+	Watch(ctx context.Context) <-chan Work
+}
+
+// Transformer is an interface that defines how to transform a Work item into
+// the generic modsec.Message format and encoded into a destination specific
+// payload. This interface encapsulates most of the chain agnostic services
+// required by the 1.6 implementation.
+type Transformer interface {
+	Transform(work Work) HandlerPayload
+}
+
+// Writer is an interface that defines how to write attestations and messages to a storage layer.
+// The writer is responsible for deciding how to store the messages and attestations, including
+// how to avoid duplicates, and how to structure the storage for efficient scanning.
+//
+// TODO: standard io.Writer interface could be used to simplify testing.
+// Modex extensions would look like "modsec.NewS3Writer(path)"
+type Writer interface {
+	// WriteMessage stores the message that is being attested.
+	// The writer implementation is responsible for deciding how to store the message.
+	// It should consider things like how it will be retrieved later, and how to avoid duplicates.
+	// For example, it may decide to store messages in a hierarchy based on the time, block number, sequence number, etc.
+	WriteMessage(ctx context.Context, msg HandlerPayload) error
+
+	// WriteAttestation stores the attestation for a message.
+	// The writer implementation is responsible for deciding how to store the attestation.
+	// It should consider things like how it will be retrieved later, and how to avoid duplicates.
+	WriteAttestation(ctx context.Context, msg Attestation) error
+}
+
+// Handler is a function that processes incoming work from the work channel and sends results to the result channel.
+// There may be no results for a particular piece of work, in which case the result channel should not be written to.
+// For example, the verifier may have a rule to skip processing until a certain block depth is reached. In that case,
+// the work may be received, but no result will be produced until later.
+//
+// The verifier should respect the context for cancellation. If the context is cancelled, the verifier should stop.
+//
+// TODO: should verifier be a full service with start/stop/cancel, a cache, maybe a db connection, etc?
+type Handler func(ctx context.Context, payload HandlerPayload, result chan<- Attestation)
diff --git a/chainlink-modsec/libmodsec/internal/verifier/main.go b/chainlink-modsec/libmodsec/internal/verifier/main.go
new file mode 100644
index 0000000000..0acc647277
--- /dev/null
+++ b/chainlink-modsec/libmodsec/internal/verifier/main.go
@@ -0,0 +1,143 @@
+package verifier
+
+import (
+	"context"
+	"fmt"
+	"sync"
+)
+
+// run is the verifier main loop.
+//
+// Implementation of a pipeline:
+//   - Read events from blockchain.
+//   - Transform events to the verifier payload.
+//   - * Write raw message to storage.
+//   - Dispatch payloads to verifiers.
+//   - Collect results from verifiers as they are available.
+//   - Write verifier attestations to storage.
+func (s *Verifier) run() {
+	if s.writer == nil {
+		fmt.Println("No writer configured, verifier will not process any work.")
+		// TODO: surface an error.
+		return
+	}
+	if s.transformer == nil {
+		fmt.Println("No transformer configured, verifier will not process any work.")
+		// TODO: surface an error.
+		return
+	}
+	if s.signer == nil {
+		fmt.Println("No signer configured, verifier will not process any work.")
+		// TODO: surface an error.
+		return
+	}
+
+	ctx, cancel := context.WithCancel(context.Background())
+	defer cancel()
+
+	var wg sync.WaitGroup
+
+	transformCh := make(chan Work)
+	handlerPayloadCh := make(chan HandlerPayload)
+	writePayloadCh := make(chan HandlerPayload)
+	writeAttestationCh := make(chan Attestation)
+
+	// Read blockchain data for new work.
+	go func() {
+		wg.Add(1)
+		defer wg.Done()
+
+		for true {
+			select {
+			case <-ctx.Done():
+				fmt.Println("Verifier shutting down poller...")
+				return
+			case data := <-s.reader.Next(ctx):
+				fmt.Println(data)
+				transformCh <- data // to transformer
+			}
+		}
+	}()
+
+	// Transform work into the handler payload.
+	go func() {
+		wg.Add(1)
+		defer wg.Done()
+
+		for true {
+			select {
+			case <-ctx.Done():
+				fmt.Println("Verifier shutting down transformer...")
+				return
+			case work := <-transformCh:
+				payload := s.transformer.Transform(work)
+				fmt.Println("Payload transformed:", payload)
+				handlerPayloadCh <- payload // to handler dispatch.
+				writePayloadCh <- payload   // to writer.
+			}
+		}
+	}()
+
+	// run handlers
+	go func() {
+		wg.Add(1)
+		defer wg.Done()
+
+		for true {
+			select {
+			case <-ctx.Done():
+				fmt.Println("Verifier shutting down handlers...")
+				return
+			case payload := <-handlerPayloadCh:
+				fmt.Printf("Running handlers for payload: %v\n", payload)
+				// Dispatch payload to each handler.
+				for _, handler := range s.handlers {
+					// TODO: signing needs to fit in before writing.
+					go handler(ctx, payload, writeAttestationCh)
+				}
+			}
+		}
+	}()
+
+	// write results
+	go func() {
+		wg.Add(1)
+		defer wg.Done()
+
+		for true {
+			select {
+			case <-ctx.Done():
+				fmt.Println("Verifier shutting down handlers...")
+				return
+			case payload := <-writePayloadCh:
+				for _, w := range s.writer {
+					if err := w.WriteMessage(ctx, payload); err != nil {
+						// TODO: surface an error.
+						fmt.Println("Error writing payload.")
+					}
+				}
+			case attestation := <-writeAttestationCh:
+				for _, w := range s.writer {
+					if err := w.WriteAttestation(ctx, attestation); err != nil {
+						// TODO: surface an error.
+						fmt.Println("Error writing payload.")
+					}
+				}
+			}
+		}
+	}()
+
+	// Wait for service to stop.
+	done := false
+	for !done {
+		select {
+		case <-s.stopCh:
+			cancel()
+			done = true
+		case <-ctx.Done():
+			done = true
+		}
+	}
+
+	wg.Wait()
+}
diff --git a/chainlink-modsec/libmodsec/internal/verifier/types.go b/chainlink-modsec/libmodsec/internal/verifier/types.go
new file mode 100644
index 0000000000..7530a19a0b
--- /dev/null
+++ b/chainlink-modsec/libmodsec/internal/verifier/types.go
@@ -0,0 +1,47 @@
+package verifier
+
+import (
+	"github.com/smartcontractkit/chainlink-modsec/libmodsec/pkg/modsectypes"
+)
+
+// BlockInfo contains basic block metadata.
+type BlockInfo struct {
+	SourceChain uint64
+	BlockNum    uint64 // why do they use big int... at 100k  bps it would take 500k years to overflow uint64.
+	BlockHash   []byte
+	Finalized   bool // if the chain supports a finalized tag.
+}
+
+// Work is generated from the blockchain reader. It contains all raw data
+// required to verify a message. Work for one verification may be split
+// across multiple work items. For example, a finalized message verifier
+// would receive the initial work item containing message data but wait
+// to emit an attestation until the block is finalized before emitting an
+// attestation.
+type Work struct {
+	Data []byte // maybe nil if there were no messages for a particular block num
+	BlockInfo
+}
+
+// HandlerPayload is generated by the Transformer. It contains the Work data
+// in a processed format. Processing includes:
+// * Decoding the data into an AnyToAny object.
+// * Encoding the data into a destination byte format (for verifier signing).
+type HandlerPayload struct {
+	ID        string
+	Message   modsectypes.Message
+	DestData  []byte
+	BlockInfo BlockInfo
+}
+
+// VerifierInfo metadata needed by the writer.
+type VerifierInfo struct {
+	ID string
+}
+
+// Attestation for a message.
+type Attestation struct {
+	VerifierInfo VerifierInfo
+	Message      modsectypes.Message
+	Sig          []byte
+}
diff --git a/chainlink-modsec/libmodsec/internal/verifier/verifier.go b/chainlink-modsec/libmodsec/internal/verifier/verifier.go
new file mode 100644
index 0000000000..7f51c57fb7
--- /dev/null
+++ b/chainlink-modsec/libmodsec/internal/verifier/verifier.go
@@ -0,0 +1,77 @@
+package verifier
+
+import (
+	"github.com/smartcontractkit/chainlink-modsec/libmodsec/pkg/modsectypes"
+)
+
+// Verifier is the main verifier service. It manages the lifecycle of data
+// fetching, handling, and writing a resulting attestation.
+type Verifier struct {
+	workCh chan Work
+	stopCh chan struct{}
+
+	// configurable components
+	handlers    []Handler
+	signer      modsectypes.Signer
+	reader      Reader
+	transformer Transformer
+	writer      []Writer
+	// Add more configurable fields as needed
+}
+
+// Option is the Verifier functional option type
+type Option func(*Verifier)
+
+// WithSigner sets a custom signer for the verifier
+func WithSigner(signer modsectypes.Signer) Option {
+	return func(v *Verifier) {
+		v.signer = signer
+	}
+}
+
+// WithReader sets a reader for the verifier
+func WithReader(reader Reader) Option {
+	return func(v *Verifier) {
+		v.reader = reader
+	}
+}
+
+// WithTransformer sets the transformer for the verifier
+func WithTransformer(transformer Transformer) Option {
+	return func(v *Verifier) {
+		v.transformer = transformer
+	}
+}
+
+// WithWriter adds a writer for the verifier
+func WithWriter(writer Writer) Option {
+	return func(v *Verifier) {
+		v.writer = append(v.writer, writer)
+	}
+}
+
+// WithHandler adds a handler function, there can be more than one.
+func WithHandler(handler Handler) Option {
+	return func(v *Verifier) {
+		v.handlers = append(v.handlers, handler)
+	}
+}
+
+func NewVerifier(opts ...Option) *Verifier {
+	v := &Verifier{
+		stopCh: make(chan struct{}),
+	}
+	// Apply all options
+	for _, opt := range opts {
+		opt(v)
+	}
+	return v
+}
+
+func (s *Verifier) Start() {
+	go s.run()
+}
+
+func (s *Verifier) Stop() {
+	close(s.stopCh)
+}