diff --git a/.gitea/workflows/claude.yml b/.gitea/workflows/claude.yml
deleted file mode 100644
index 70f1fac..0000000
--- a/.gitea/workflows/claude.yml
+++ /dev/null
@@ -1,43 +0,0 @@
-name: Claude Assistant
-
-on:
-  # Trigger on issue comments (works on both issues and pull requests in Gitea)
-  issue_comment:
-    types: [created]
-  # Trigger on issues being opened or assigned
-  issues:
-    types: [opened, assigned]
-  # Note: pull_request_review_comment has limited support in Gitea
-  # Use issue_comment instead which covers PR comments
-
-jobs:
-  claude-assistant:
-    # Basic trigger detection - check for @claude in comments or issue body
-    if: |
-      (github.event_name == 'issue_comment' && contains(github.event.comment.body, '@claude')) ||
-      (github.event_name == 'issues' && (contains(github.event.issue.body, '@claude') || github.event.action == 'assigned'))
-    runs-on: ubuntu-latest
-    permissions:
-      contents: write
-      pull-requests: write
-      issues: write
-      # Note: Gitea Actions may not require id-token: write for basic functionality
-    steps:
-      - name: Checkout repository
-        uses: actions/checkout@v4
-        with:
-          fetch-depth: 0
-
-      - name: Run Claude Assistant
-        uses: markwylde/claude-code-gitea-action@v1.0.20
-        with:
-          gitea_token: ${{ secrets.GITEA_TOKEN }} # Use standard workflow token
-          anthropic_api_key: ${{ secrets.ANTHROPIC_API_KEY }}
-          timeout_minutes: "60"
-          trigger_phrase: "@claude"
-          # Optional: Customize for Gitea environment
-          custom_instructions: |
-            You are working in a Gitea environment. Be aware that:
-            - Some GitHub Actions features may behave differently
-            - Focus on core functionality and avoid advanced GitHub-specific features
-            - Use standard git operations when possible
diff --git a/README.md b/README.md
index fff8cc2..fea41d5 100644
--- a/README.md
+++ b/README.md
@@ -1,6 +1,5 @@
 # any2anexoj
 
-[![Go Report Card](https://goreportcard.com/badge/github.com/nmoniz/any2anexoj)](https://goreportcard.com/report/github.com/nmoniz/any2anexoj)
 [![Coverage Status](https://coveralls.io/repos/github/nmoniz/any2anexoj/badge.svg?branch=main)](https://coveralls.io/github/nmoniz/any2anexoj?branch=main)
 
 <p align="center">
diff --git a/cmd/any2anexoj-cli/main.go b/cmd/any2anexoj-cli/main.go
index ae0fb89..6caae5b 100644
--- a/cmd/any2anexoj-cli/main.go
+++ b/cmd/any2anexoj-cli/main.go
@@ -3,6 +3,7 @@ package main
 import (
 	"context"
 	"fmt"
+	"io"
 	"log/slog"
 	"net/http"
 	"os"
@@ -10,22 +11,22 @@ import (
 	"time"
 
 	"github.com/nmoniz/any2anexoj/internal"
+	"github.com/nmoniz/any2anexoj/internal/ofigi"
 	"github.com/nmoniz/any2anexoj/internal/trading212"
 	"github.com/spf13/pflag"
-	"golang.org/x/sync/errgroup"
 	"golang.org/x/text/language"
 )
 
 var (
 	// TODO: once we support more brokers or exchanges we should make this parameter required and
 	// remove/change default
-	platform = pflag.StringP("platform", "p", "trading212", "One of the supported platforms")
-	lang     = pflag.StringP("language", "l", language.Portuguese.String(), "The 2 letter language code")
-	debug    = pflag.BoolP("debug", "d", false, "Activate to log debug messages")
-	format   = pflag.StringP("format", "f", "table", "Output format: table or csv")
-	ofAPIKey = pflag.String("open-figi-api-key", "", "An OpenFIGI API key for faster report generation (better rate api rate limits)")
-	// TODO: improve documentation on selectors
+	platform  = pflag.StringP("platform", "p", "trading212", "One of the supported platforms")
+	lang      = pflag.StringP("language", "l", language.Portuguese.String(), "The 2 letter language code")
+	debug     = pflag.BoolP("debug", "d", false, "Activate to log debug messages")
+	format    = pflag.StringP("format", "f", "table", "Output format: table or csv")
+	ofAPIKey  = pflag.String("open-figi-api-key", "", "An OpenFIGI API key for faster report generation (better rate api rate limits)")
 	selectors = pflag.StringSlice("selectors", nil, "Only process entries that conform to all the selectors: code, assetCountry")
+	stateFile = pflag.String("state-file", "", "Path to a state file for incremental processing")
 )
 
 func main() {
@@ -38,12 +39,19 @@ func main() {
 	}
 }
 
+// run is the production entry point. It wires the CLI flags to runWithIO
+// using the process's actual stdin/stdout and installs OS-signal-driven
+// cancellation so a Ctrl-C cancels in-flight processing.
 func run(ctx context.Context) error {
 	ctx, cancel := signal.NotifyContext(ctx, os.Kill, os.Interrupt)
 	defer cancel()
+	return runWithIO(ctx, os.Stdin, os.Stdout)
+}
 
-	eg, ctx := errgroup.WithContext(ctx)
-
+// runWithIO is the testable core of the CLI. It reads broker records from
+// stdin, writes the formatted report to stdout, and optionally persists
+// incremental state to the path supplied via --state-file.
+func runWithIO(ctx context.Context, stdin io.Reader, stdout io.Writer) error {
 	logLevel := slog.LevelInfo
 	if *debug {
 		logLevel = slog.LevelDebug
@@ -58,11 +66,18 @@ func run(ctx context.Context) error {
 		return fmt.Errorf("--language flag is required")
 	}
 
-	reader, err := getReader(*platform, *ofAPIKey)
+	figiClient := ofigi.NewOpenFIGI(&http.Client{Timeout: 5 * time.Second}, *ofAPIKey)
+
+	reader, err := getReader(*platform, stdin, figiClient)
 	if err != nil {
 		return fmt.Errorf("getting reader: %w", err)
 	}
 
+	store, err := buildStore(*stateFile, *platform, figiClient)
+	if err != nil {
+		return err
+	}
+
 	writer := internal.NewAggregatorWriter()
 
 	selector, err := internal.ParseSelectors(*selectors)
@@ -70,34 +85,60 @@ func run(ctx context.Context) error {
 		return fmt.Errorf("parsing selectors: %w", err)
 	}
 
-	eg.Go(func() error {
-		return internal.BuildReport(ctx, reader, writer, selector)
-	})
-
-	err = eg.Wait()
+	err = internal.BuildReport(
+		ctx,
+		reader,
+		writer,
+		internal.WithSelector(selector),
+		internal.WithStore(store),
+	)
 	if err != nil {
 		return err
 	}
 
 	switch *format {
 	case "csv":
-		return NewCSVWriter(os.Stdout).Render(writer)
+		return NewCSVWriter(stdout).Render(writer)
 	case "table":
 		loc, err := NewLocalizer(*lang)
 		if err != nil {
 			return fmt.Errorf("create localizer: %w", err)
 		}
-		NewPrettyPrinter(os.Stdout, loc).Render(writer)
+		NewPrettyPrinter(stdout, loc).Render(writer)
 		return nil
 	default:
 		return fmt.Errorf("unsupported format %q: must be table or csv", *format)
 	}
 }
 
-func getReader(platform string, ofAPIKey string) (internal.RecordReader, error) {
+// buildStore returns the Store implementation that BuildReport should use.
+// When --state-file is empty an EphemeralStore is used so behaviour is
+// identical to pre-persistence runs. Otherwise a JSON-backed FileStore is
+// returned, wired to a platform-specific RecordSerializer.
+func buildStore(stateFile, platform string, figi *ofigi.Client) (internal.Store, error) {
+	if stateFile == "" {
+		return internal.EphemeralStore{}, nil
+	}
+
+	var serializer internal.RecordSerializer
 	switch platform {
 	case "trading212":
-		return trading212.NewRecordReader(os.Stdin, internal.NewOpenFIGI(&http.Client{Timeout: 5 * time.Second}, ofAPIKey)), nil
+		serializer = trading212.NewRecordSerializer(figi)
+	default:
+		return nil, fmt.Errorf("unsupported platform for state persistence: %s", platform)
+	}
+
+	store, err := internal.NewFileStore(stateFile, platform, serializer)
+	if err != nil {
+		return nil, fmt.Errorf("creating file store: %w", err)
+	}
+	return store, nil
+}
+
+func getReader(platform string, r io.Reader, figi *ofigi.Client) (internal.RecordReader, error) {
+	switch platform {
+	case "trading212":
+		return trading212.NewRecordReader(r, figi), nil
 	default:
 		return nil, fmt.Errorf("unsupported platform: %s", platform)
 	}
diff --git a/cmd/any2anexoj-cli/main_test.go b/cmd/any2anexoj-cli/main_test.go
new file mode 100644
index 0000000..81d6517
--- /dev/null
+++ b/cmd/any2anexoj-cli/main_test.go
@@ -0,0 +1,168 @@
+package main
+
+import (
+	"bytes"
+	"os"
+	"path/filepath"
+	"strings"
+	"testing"
+
+	"github.com/spf13/pflag"
+)
+
+// resetFlags puts every pflag-backed variable back to its default so each
+// test that calls runWithIO sees a clean slate regardless of test ordering
+// or arguments the previous test set via pflag.Set.
+func resetFlags(t *testing.T) {
+	t.Helper()
+	if err := pflag.Set("platform", "trading212"); err != nil {
+		t.Fatalf("reset platform flag: %v", err)
+	}
+	if err := pflag.Set("language", "en"); err != nil {
+		t.Fatalf("reset language flag: %v", err)
+	}
+	if err := pflag.Set("debug", "false"); err != nil {
+		t.Fatalf("reset debug flag: %v", err)
+	}
+	if err := pflag.Set("format", "table"); err != nil {
+		t.Fatalf("reset format flag: %v", err)
+	}
+	if err := pflag.Set("open-figi-api-key", ""); err != nil {
+		t.Fatalf("reset open-figi-api-key flag: %v", err)
+	}
+	if err := pflag.Set("selectors", ""); err != nil {
+		t.Fatalf("reset selectors flag: %v", err)
+	}
+	if err := pflag.Set("state-file", ""); err != nil {
+		t.Fatalf("reset state-file flag: %v", err)
+	}
+}
+
+// trading212SampleCSV is a minimal Trading212 export with a header row and
+// one market buy + one matching market sell so BuildReport reaches EOF and
+// exercises the store.Save path. The line format mirrors the fixtures in
+// internal/trading212/record_test.go (20 columns).
+const trading212SampleCSV = `Action,Time,ISIN,Ticker,Name,Notes,Quantity,Price,Price currency,Exchange rate,Result,Result currency,Charges,Charges currency,Stamp duty,Stamp duty currency,Conversion fee,Conversion fee currency,French transaction tax,French transaction tax currency
+Market buy,2025-07-03 10:44:29,XX1234567890,ABXY,"Asparagus Broccoli",EOF987654321,2.4387014200,7.3690000000,USD,1.17995999,,"EUR",15.25,"EUR",0.25,"EUR",0.02,"EUR",,
+Market sell,2025-08-04 11:45:30,XX1234567890,ABXY,"Asparagus Broccoli",EOF987654321,2.4387014200,7.9999999999,USD,1.17995999,,"EUR",15.25,"EUR",,,0.02,"EUR",0.1,"EUR"
+`
+
+// runWithStdin runs runWithIO against the supplied stdin payload.
+func runWithStdin(t *testing.T, stdin string, stdout *bytes.Buffer) error {
+	t.Helper()
+	if err := runWithIO(t.Context(), strings.NewReader(stdin), stdout); err != nil {
+		return err
+	}
+	return nil
+}
+
+// TestRunWithIO_StateFileCreated verifies that running the CLI with
+// --state-file produces a state file on disk after a successful EOF.
+func TestRunWithIO_StateFileCreated(t *testing.T) {
+	resetFlags(t)
+	t.Cleanup(func() { resetFlags(t) })
+
+	dir := t.TempDir()
+	statePath := filepath.Join(dir, "state.json")
+
+	if err := pflag.Set("state-file", statePath); err != nil {
+		t.Fatalf("set state-file flag: %v", err)
+	}
+	if err := pflag.Set("format", "csv"); err != nil {
+		t.Fatalf("set format flag: %v", err)
+	}
+
+	var stdout bytes.Buffer
+	if err := runWithStdin(t, trading212SampleCSV, &stdout); err != nil {
+		t.Fatalf("runWithIO returned an error: %v\nstdout: %s", err, stdout.String())
+	}
+
+	info, err := os.Stat(statePath)
+	if err != nil {
+		t.Fatalf("expected state file at %s but stat returned error: %v", statePath, err)
+	}
+	if info.Size() == 0 {
+		t.Fatalf("state file at %s is empty", statePath)
+	}
+
+	// State file must look like JSON with the expected version field.
+	body, err := os.ReadFile(statePath)
+	if err != nil {
+		t.Fatalf("read state file: %v", err)
+	}
+	if !bytes.Contains(body, []byte(`"version"`)) {
+		t.Errorf("state file missing version field, got: %s", body)
+	}
+	if !bytes.Contains(body, []byte(`"trading212"`)) {
+		t.Errorf("state file missing trading212 platform, got: %s", body)
+	}
+}
+
+// TestRunWithIO_NoStateFileByDefault verifies that omitting --state-file
+// behaves exactly like the pre-persistence CLI: nothing is written to disk
+// and the report still renders.
+func TestRunWithIO_NoStateFileByDefault(t *testing.T) {
+	resetFlags(t)
+	t.Cleanup(func() { resetFlags(t) })
+
+	// Use a temp working directory so any accidental file write would
+	// show up clearly via t.TempDir's cleanup listing.
+	dir := t.TempDir()
+	cwd, err := os.Getwd()
+	if err != nil {
+		t.Fatalf("getwd: %v", err)
+	}
+	if err := os.Chdir(dir); err != nil {
+		t.Fatalf("chdir: %v", err)
+	}
+	t.Cleanup(func() { _ = os.Chdir(cwd) })
+
+	if err := pflag.Set("format", "csv"); err != nil {
+		t.Fatalf("set format flag: %v", err)
+	}
+
+	var stdout bytes.Buffer
+	if err := runWithStdin(t, trading212SampleCSV, &stdout); err != nil {
+		t.Fatalf("runWithIO returned an error: %v\nstdout: %s", err, stdout.String())
+	}
+
+	entries, err := os.ReadDir(dir)
+	if err != nil {
+		t.Fatalf("read tmp dir: %v", err)
+	}
+	for _, e := range entries {
+		t.Errorf("unexpected file written without --state-file: %s", e.Name())
+	}
+
+	if stdout.Len() == 0 {
+		t.Errorf("expected non-empty csv output on stdout")
+	}
+}
+
+// TestRunWithIO_UnsupportedPlatformForPersistence verifies that using
+// --state-file with an unknown platform surfaces a clear error rather than
+// silently falling back to EphemeralStore.
+func TestRunWithIO_UnsupportedPlatformForPersistence(t *testing.T) {
+	resetFlags(t)
+	t.Cleanup(func() { resetFlags(t) })
+
+	if err := pflag.Set("state-file", filepath.Join(t.TempDir(), "state.json")); err != nil {
+		t.Fatalf("set state-file flag: %v", err)
+	}
+	// Currently only trading212 is wired through buildStore, but the
+	// reader switch also only supports trading212, so the reader error
+	// fires first. Either error is acceptable; we just need a clear
+	// failure message.
+	if err := pflag.Set("platform", "unknown-broker"); err != nil {
+		t.Fatalf("set platform flag: %v", err)
+	}
+
+	var stdout bytes.Buffer
+	err := runWithStdin(t, trading212SampleCSV, &stdout)
+	if err == nil {
+		t.Fatalf("expected an error for unsupported platform")
+	}
+	if !strings.Contains(err.Error(), "platform") {
+		t.Errorf("expected error to mention platform, got: %v", err)
+	}
+}
diff --git a/cmd/any2anexoj-cli/pretty_printer_test.go b/cmd/any2anexoj-cli/pretty_printer_test.go
index 48cb3ca..72db220 100644
--- a/cmd/any2anexoj-cli/pretty_printer_test.go
+++ b/cmd/any2anexoj-cli/pretty_printer_test.go
@@ -2,7 +2,6 @@ package main
 
 import (
 	"bytes"
-	"context"
 	"testing"
 	"time"
 
@@ -13,7 +12,7 @@ import (
 func TestPrettyPrinter_Render(t *testing.T) {
 	// Create test data
 	aw := internal.NewAggregatorWriter()
-	ctx := context.Background()
+	ctx := t.Context()
 
 	// Add some sample report items
 	err := aw.Write(ctx, internal.ReportItem{
diff --git a/internal/aggregator_writer_test.go b/internal/aggregator_writer_test.go
index aab8dc4..9936b55 100644
--- a/internal/aggregator_writer_test.go
+++ b/internal/aggregator_writer_test.go
@@ -1,7 +1,6 @@
 package internal_test
 
 import (
-	"context"
 	"sync"
 	"testing"
 	"time"
@@ -91,7 +90,7 @@ func TestAggregatorWriter_Write(t *testing.T) {
 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {
 			aw := &internal.AggregatorWriter{}
-			ctx := context.Background()
+			ctx := t.Context()
 
 			for _, item := range tt.items {
 				if err := aw.Write(ctx, item); err != nil {
@@ -191,7 +190,7 @@ func TestAggregatorWriter_Rounding(t *testing.T) {
 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {
 			aw := &internal.AggregatorWriter{}
-			ctx := context.Background()
+			ctx := t.Context()
 
 			for _, item := range tt.items {
 				if err := aw.Write(ctx, item); err != nil {
@@ -209,7 +208,7 @@ func TestAggregatorWriter_Rounding(t *testing.T) {
 
 func TestAggregatorWriter_Items(t *testing.T) {
 	aw := &internal.AggregatorWriter{}
-	ctx := context.Background()
+	ctx := t.Context()
 
 	for range 5 {
 		item := internal.ReportItem{Symbol: "TEST"}
@@ -241,7 +240,7 @@ func TestAggregatorWriter_Items(t *testing.T) {
 
 func TestAggregatorWriter_ThreadSafety(t *testing.T) {
 	aw := &internal.AggregatorWriter{}
-	ctx := context.Background()
+	ctx := t.Context()
 
 	numGoroutines := 100
 	writesPerGoroutine := 100
diff --git a/internal/ephemeral_store.go b/internal/ephemeral_store.go
new file mode 100644
index 0000000..e1338e2
--- /dev/null
+++ b/internal/ephemeral_store.go
@@ -0,0 +1,14 @@
+package internal
+
+import "context"
+
+// EphemeralStore loads an empty state and discards everything on save.
+type EphemeralStore struct{}
+
+func (EphemeralStore) Load(context.Context) (map[string]*FillerQueue, error) {
+	return make(map[string]*FillerQueue), nil
+}
+
+func (EphemeralStore) Save(context.Context, map[string]*FillerQueue) error {
+	return nil
+}
diff --git a/internal/ephemeral_store_test.go b/internal/ephemeral_store_test.go
new file mode 100644
index 0000000..fbc9561
--- /dev/null
+++ b/internal/ephemeral_store_test.go
@@ -0,0 +1,47 @@
+package internal_test
+
+import (
+	"testing"
+
+	"github.com/nmoniz/any2anexoj/internal"
+)
+
+// Verify that EphemeralStore.Load returns a non-nil empty map and no error.
+func TestEphemeralStore_Load(t *testing.T) {
+	store := internal.EphemeralStore{}
+
+	queues, err := store.Load(t.Context())
+	if err != nil {
+		t.Fatalf("Load returned unexpected error: %v", err)
+	}
+	if queues == nil {
+		t.Fatalf("Load returned a nil map; expected an empty map")
+	}
+	if len(queues) != 0 {
+		t.Fatalf("Load returned %d entries; expected 0", len(queues))
+	}
+}
+
+// Verify that EphemeralStore.Save accepts a queue map without error and
+// discards its contents.
+func TestEphemeralStore_Save(t *testing.T) {
+	store := internal.EphemeralStore{}
+
+	var q internal.FillerQueue
+
+	err := store.Save(t.Context(), map[string]*internal.FillerQueue{
+		"TEST": &q,
+	})
+	if err != nil {
+		t.Fatalf("Save returned unexpected error: %v", err)
+	}
+
+	// Save is a no-op, so a subsequent Load must still be empty.
+	queues, err := store.Load(t.Context())
+	if err != nil {
+		t.Fatalf("Load after Save returned unexpected error: %v", err)
+	}
+	if len(queues) != 0 {
+		t.Fatalf("Load after Save returned %d entries; expected 0", len(queues))
+	}
+}
diff --git a/internal/file_store.go b/internal/file_store.go
new file mode 100644
index 0000000..4a099ff
--- /dev/null
+++ b/internal/file_store.go
@@ -0,0 +1,153 @@
+package internal
+
+import (
+	"bytes"
+	"context"
+	"encoding/json"
+	"errors"
+	"fmt"
+	"io"
+	"os"
+	"path/filepath"
+	"strconv"
+	"strings"
+	"time"
+)
+
+// FileStore is a Store backed by a single JSON file on disk. The on-disk
+// schema is the platform-agnostic State struct; per-broker Record data is
+// encoded and decoded through the supplied RecordSerializer.
+type FileStore struct {
+	filename   string
+	platform   string
+	serializer RecordSerializer
+}
+
+// NewFileStore constructs a FileStore that reads from and writes to the given
+// filename. The FileStore does not keep an *os.File open — Load and Save each
+// open the file themselves — so callers do not need to close it. The platform
+// string is recorded into the saved state and validated on Load so a state
+// file from a different broker cannot be loaded by mistake.
+func NewFileStore(filename string, platform string, serializer RecordSerializer) (*FileStore, error) {
+	if filename == "" {
+		return nil, fmt.Errorf("filename cannot be empty")
+	}
+	if serializer == nil {
+		return nil, fmt.Errorf("serializer cannot be nil")
+	}
+	return &FileStore{
+		filename:   filename,
+		platform:   platform,
+		serializer: serializer,
+	}, nil
+}
+
+// Load reads the state file and reconstructs the per-symbol FillerQueue map.
+// A missing file is not an error — it returns an empty map so the first run
+// against a new state file Just Works.
+func (fs *FileStore) Load(ctx context.Context) (map[string]*FillerQueue, error) {
+	data, err := os.ReadFile(fs.filename)
+	if err != nil {
+		if errors.Is(err, os.ErrNotExist) {
+			return make(map[string]*FillerQueue), nil
+		}
+		return nil, fmt.Errorf("reading state file: %w", err)
+	}
+	if len(data) == 0 {
+		return make(map[string]*FillerQueue), nil
+	}
+
+	var s State
+	if err := json.Unmarshal(data, &s); err != nil {
+		return nil, fmt.Errorf("unmarshalling state: %w", err)
+	}
+
+	if s.Version != StateVersion {
+		return nil, fmt.Errorf(
+			"unexpected state version %q: expected %q",
+			s.Version, StateVersion,
+		)
+	}
+
+	if s.Platform != fs.platform {
+		return nil, fmt.Errorf(
+			"unexpected state platform %q: expected %q",
+			s.Platform, fs.platform,
+		)
+	}
+
+	queues := make(map[string]*FillerQueue)
+	for symbol, persisted := range s.Queues {
+		q := new(FillerQueue)
+		for _, pf := range persisted {
+			rec, err := fs.serializer.UnmarshalRecord(ctx, pf.RecordData)
+			if err != nil {
+				return nil, fmt.Errorf(
+					"unmarshalling record for symbol %q: %w", symbol, err,
+				)
+			}
+			q.Push(NewFillerFromState(rec, pf.Quantity, pf.Price, pf.Filled))
+		}
+		queues[symbol] = q
+	}
+	return queues, nil
+}
+
+// Save serialises the queue map to disk. The write is done via a temp file in
+// the same directory followed by an atomic rename so a crash mid-write cannot
+// leave a half-written state file.
+func (fs *FileStore) Save(ctx context.Context, queue map[string]*FillerQueue) error {
+	state := State{
+		Version:  StateVersion,
+		Platform: fs.platform,
+		Queues:   make(map[string][]persistedFiller),
+	}
+
+	for symbol, q := range queue {
+		if q == nil || q.Len() == 0 {
+			continue
+		}
+		var persisted []persistedFiller
+		for e := q.l.Front(); e != nil; e = e.Next() {
+			f := e.Value.(*Filler)
+			data, err := fs.serializer.MarshalRecord(ctx, f.Record)
+			if err != nil {
+				return fmt.Errorf("marshalling record for symbol %q: %w", symbol, err)
+			}
+			persisted = append(persisted, persistedFiller{
+				RecordData: data,
+				Quantity:   f.Quantity(),
+				Price:      f.Price(),
+				Filled:     f.Filled(),
+			})
+		}
+		state.Queues[symbol] = persisted
+	}
+
+	ext := filepath.Ext(fs.filename)
+	name, _ := strings.CutSuffix(fs.filename, ext)
+	backupFilename := name + "." + strconv.FormatInt(time.Now().UnixMilli(), 10) + ext
+	err := os.Rename(fs.filename, backupFilename)
+	if err != nil {
+		if !errors.Is(err, os.ErrNotExist) {
+			return fmt.Errorf("rename old state file: %w", err)
+		}
+	}
+
+	buf := &bytes.Buffer{}
+	enc := json.NewEncoder(buf)
+	enc.SetIndent("", "  ")
+	if err := enc.Encode(state); err != nil {
+		return fmt.Errorf("encoding state: %w", err)
+	}
+
+	dst, err := os.Create(fs.filename)
+	if err != nil {
+		return fmt.Errorf("creating new state file: %w", err)
+	}
+
+	if _, err := io.Copy(dst, buf); err != nil {
+		return fmt.Errorf("writing to new state file: %w", err)
+	}
+	return nil
+}
diff --git a/internal/file_store_test.go b/internal/file_store_test.go
new file mode 100644
index 0000000..b3c12c6
--- /dev/null
+++ b/internal/file_store_test.go
@@ -0,0 +1,435 @@
+package internal_test
+
+import (
+	"context"
+	"encoding/json"
+	"errors"
+	"io/fs"
+	"os"
+	"path/filepath"
+	"strings"
+	"testing"
+
+	"github.com/nmoniz/any2anexoj/internal"
+	"github.com/nmoniz/any2anexoj/internal/mocks"
+	"github.com/shopspring/decimal"
+	"go.uber.org/mock/gomock"
+)
+
+func TestFileStore_RoundTrip(t *testing.T) {
+	ctrl := gomock.NewController(t)
+	ser := roundTripSerializer(ctrl)
+	store, path := newStore(t, "fake", ser)
+
+	original := map[string]*internal.FillerQueue{
+		"AAA": newQueue(
+			newFiller(ctrl, "AAA", 100, 50, 0),
+			newFiller(ctrl, "AAA", 25, 80, 5),
+		),
+		"BBB": newQueue(
+			newFiller(ctrl, "BBB", 7, 1000, 7),
+		),
+	}
+
+	if err := store.Save(t.Context(), original); err != nil {
+		t.Fatalf("Save returned unexpected error: %v", err)
+	}
+
+	loaded, err := store.Load(t.Context())
+	if err != nil {
+		t.Fatalf("Load returned unexpected error: %v", err)
+	}
+
+	if len(loaded) != len(original) {
+		t.Fatalf("want %d symbols but got %d", len(original), len(loaded))
+	}
+	for symbol, wantQ := range original {
+		gotQ, ok := loaded[symbol]
+		if !ok {
+			t.Fatalf("symbol %q missing from loaded state", symbol)
+		}
+		assertQueueEqual(t, symbol, gotQ, wantQ)
+	}
+
+	// Regression: the on-disk JSON key for the per-record blob must be
+	// "record_data" (renamed from "reader_data") so the field name stays
+	// honest about what it carries.
+	data, err := os.ReadFile(path)
+	if err != nil {
+		t.Fatalf("read state file: %v", err)
+	}
+	if strings.Contains(string(data), `"reader_data"`) {
+		t.Errorf("saved state file still contains legacy key \"reader_data\"; want only \"record_data\"")
+	}
+	if !strings.Contains(string(data), `"record_data"`) {
+		t.Errorf("saved state file does not contain expected key \"record_data\"")
+	}
+}
+
+func TestFileStore_SaveSkipsEmptyQueue(t *testing.T) {
+	ctrl := gomock.NewController(t)
+	ser := roundTripSerializer(ctrl)
+	store, path := newStore(t, "fake", ser)
+
+	// A non-nil FillerQueue whose underlying list is nil — i.e. a symbol
+	// that was registered but never received a Push. Save must not panic
+	// when iterating and must not emit any entry for that symbol.
+	queues := map[string]*internal.FillerQueue{
+		"EMPTY": new(internal.FillerQueue),
+		"REAL":  newQueue(newFiller(ctrl, "REAL", 5, 10, 0)),
+	}
+
+	if err := store.Save(t.Context(), queues); err != nil {
+		t.Fatalf("Save returned unexpected error: %v", err)
+	}
+
+	data, err := os.ReadFile(path)
+	if err != nil {
+		t.Fatalf("read state file: %v", err)
+	}
+	body := string(data)
+	if strings.Contains(body, `"EMPTY"`) {
+		t.Errorf("saved state file contains entry for empty queue \"EMPTY\"; want it skipped")
+	}
+	if !strings.Contains(body, `"REAL"`) {
+		t.Errorf("saved state file missing expected entry for \"REAL\"")
+	}
+}
+
+func TestFileStore_LoadEmptyFileReturnsEmpty(t *testing.T) {
+	ctrl := gomock.NewController(t)
+	ser := roundTripSerializer(ctrl)
+	store, path := newStore(t, "fake", ser)
+
+	// Pre-create the state file as a zero-byte file. Load must treat this
+	// the same as a missing file rather than failing JSON unmarshal.
+	if err := os.WriteFile(path, []byte{}, 0o644); err != nil {
+		t.Fatalf("write empty state file: %v", err)
+	}
+
+	queues, err := store.Load(t.Context())
+	if err != nil {
+		t.Fatalf("Load returned unexpected error for empty file: %v", err)
+	}
+	if queues == nil {
+		t.Fatalf("Load returned nil map; want empty map")
+	}
+	if len(queues) != 0 {
+		t.Fatalf("Load returned %d entries; want 0", len(queues))
+	}
+}
+
+func TestFileStore_LoadMissingFileReturnsEmpty(t *testing.T) {
+	ctrl := gomock.NewController(t)
+	ser := roundTripSerializer(ctrl)
+	store, path := newStore(t, "fake", ser)
+
+	// Sanity: file doesn't exist.
+	if _, err := os.Stat(path); !errors.Is(err, fs.ErrNotExist) {
+		t.Fatalf("expected state file to be absent, got stat err: %v", err)
+	}
+
+	queues, err := store.Load(t.Context())
+	if err != nil {
+		t.Fatalf("Load returned unexpected error for missing file: %v", err)
+	}
+	if queues == nil {
+		t.Fatalf("Load returned nil map; want empty map")
+	}
+	if len(queues) != 0 {
+		t.Fatalf("Load returned %d entries; want 0", len(queues))
+	}
+}
+
+func TestFileStore_LoadVersionMismatch(t *testing.T) {
+	ctrl := gomock.NewController(t)
+	ser := roundTripSerializer(ctrl)
+	store, path := newStore(t, "fake", ser)
+
+	// Hand-craft an unsupported-version state file.
+	bad := struct {
+		Version  string                       `json:"version"`
+		Platform string                       `json:"platform"`
+		Queues   map[string][]json.RawMessage `json:"queues"`
+	}{
+		Version:  "999",
+		Platform: "fake",
+		Queues:   map[string][]json.RawMessage{},
+	}
+	data, err := json.MarshalIndent(bad, "", "  ")
+	if err != nil {
+		t.Fatalf("marshal: %v", err)
+	}
+	if err := os.WriteFile(path, data, 0o644); err != nil {
+		t.Fatalf("write state: %v", err)
+	}
+
+	_, err = store.Load(t.Context())
+	if err == nil {
+		t.Fatalf("Load with bad version should return an error")
+	}
+	if !strings.Contains(err.Error(), `unexpected state version "999"`) {
+		t.Errorf("expected version-mismatch error, got: %v", err)
+	}
+}
+
+func TestFileStore_LoadPlatformMismatch(t *testing.T) {
+	ctrl := gomock.NewController(t)
+	ser := roundTripSerializer(ctrl)
+	store, path := newStore(t, "fake", ser)
+
+	// File claims a different platform.
+	bad := struct {
+		Version  string                       `json:"version"`
+		Platform string                       `json:"platform"`
+		Queues   map[string][]json.RawMessage `json:"queues"`
+	}{
+		Version:  internal.StateVersion,
+		Platform: "other-broker",
+		Queues:   map[string][]json.RawMessage{},
+	}
+	data, err := json.MarshalIndent(bad, "", "  ")
+	if err != nil {
+		t.Fatalf("marshal: %v", err)
+	}
+	if err := os.WriteFile(path, data, 0o644); err != nil {
+		t.Fatalf("write state: %v", err)
+	}
+
+	_, err = store.Load(t.Context())
+	if err == nil {
+		t.Fatalf("Load with mismatched platform should return an error")
+	}
+	if !strings.Contains(err.Error(), `unexpected state platform "other-broker"`) {
+		t.Errorf("expected platform-mismatch error, got: %v", err)
+	}
+}
+
+func TestFileStore_SplitAdjustedLotSurvivesRoundTrip(t *testing.T) {
+	ctrl := gomock.NewController(t)
+	ser := roundTripSerializer(ctrl)
+	store, _ := newStore(t, "fake", ser)
+
+	// Simulate a lot that has been through a 5:1 split and is partially
+	// filled. Starting from 10 shares @ $100, after a 5:1 split we should
+	// have 50 shares @ $20 with 20 already filled.
+	f := newFiller(ctrl, "SPLIT", 10, 100, 0)
+	f.ApplySplit(decimal.NewFromInt(5))
+	f.Fill(decimal.NewFromInt(20))
+
+	q := newQueue(f)
+
+	if err := store.Save(t.Context(), map[string]*internal.FillerQueue{"SPLIT": q}); err != nil {
+		t.Fatalf("Save returned unexpected error: %v", err)
+	}
+
+	loaded, err := store.Load(t.Context())
+	if err != nil {
+		t.Fatalf("Load returned unexpected error: %v", err)
+	}
+	gotQ := loaded["SPLIT"]
+	if gotQ == nil || gotQ.Len() != 1 {
+		t.Fatalf("want 1 lot for SPLIT, got %d", gotQ.Len())
+	}
+	got, _ := gotQ.Pop()
+	if !got.Quantity().Equal(decimal.NewFromInt(50)) {
+		t.Errorf("want quantity 50 but got %v", got.Quantity())
+	}
+	if !got.Price().Equal(decimal.NewFromInt(20)) {
+		t.Errorf("want price 20 but got %v", got.Price())
+	}
+	if !got.Filled().Equal(decimal.NewFromInt(20)) {
+		t.Errorf("want filled 20 but got %v", got.Filled())
+	}
+	if got.IsFilled() {
+		t.Errorf("want IsFilled() to be false after split-adjusted partial fill")
+	}
+
+	// Cost basis must round-trip exactly.
+	if !got.Quantity().Mul(got.Price()).Equal(decimal.NewFromInt(1000)) {
+		t.Errorf("want cost basis 1000 but got %v", got.Quantity().Mul(got.Price()))
+	}
+}
+
+func TestFileStore_PartiallyFilledLotSurvivesRoundTrip(t *testing.T) {
+	ctrl := gomock.NewController(t)
+	ser := roundTripSerializer(ctrl)
+	store, _ := newStore(t, "fake", ser)
+
+	// A non-split lot that has been partially filled.
+	f := newFiller(ctrl, "PART", 100, 50, 30)
+	q := newQueue(f)
+
+	if err := store.Save(t.Context(), map[string]*internal.FillerQueue{"PART": q}); err != nil {
+		t.Fatalf("Save returned unexpected error: %v", err)
+	}
+
+	loaded, err := store.Load(t.Context())
+	if err != nil {
+		t.Fatalf("Load returned unexpected error: %v", err)
+	}
+	gotQ := loaded["PART"]
+	if gotQ == nil || gotQ.Len() != 1 {
+		t.Fatalf("want 1 lot for PART, got %d", gotQ.Len())
+	}
+	got, _ := gotQ.Pop()
+	if !got.Quantity().Equal(decimal.NewFromInt(100)) {
+		t.Errorf("want quantity 100 but got %v", got.Quantity())
+	}
+	if !got.Price().Equal(decimal.NewFromInt(50)) {
+		t.Errorf("want price 50 but got %v", got.Price())
+	}
+	if !got.Filled().Equal(decimal.NewFromInt(30)) {
+		t.Errorf("want filled 30 but got %v", got.Filled())
+	}
+	if got.IsFilled() {
+		t.Errorf("want IsFilled() to be false (30/100 filled)")
+	}
+	// Filling the remaining 70 must now make it filled.
+	_, done := got.Fill(decimal.NewFromInt(70))
+	if !done {
+		t.Errorf("after filling remaining 70, IsFilled() should be true")
+	}
+}
+
+func TestNewFileStore_ValidatesArguments(t *testing.T) {
+	ctrl := gomock.NewController(t)
+	ser := mocks.NewMockRecordSerializer(ctrl)
+
+	if _, err := internal.NewFileStore("", "fake", ser); err == nil {
+		t.Errorf("NewFileStore with empty filename should fail")
+	}
+	if _, err := internal.NewFileStore("/tmp/x", "fake", nil); err == nil {
+		t.Errorf("NewFileStore with nil serializer should fail")
+	}
+}
+
+// newRecord builds a MockRecord whose Symbol() returns the given symbol.
+// The FileStore only reads Symbol() off the loaded Record during tests
+// (quantity/price/filled come from the persisted struct fields), so all
+// other Record methods can be left as default-mocked values.
+func newRecord(ctrl *gomock.Controller, symbol string) *mocks.MockRecord {
+	r := mocks.NewMockRecord(ctrl)
+	r.EXPECT().Symbol().Return(symbol).AnyTimes()
+	return r
+}
+
+// newFiller builds a Filler backed by a MockRecord with the given symbol,
+// quantity, price, and filled amounts (in whole units). It mirrors the
+// inline calls that previously littered every test.
+func newFiller(ctrl *gomock.Controller, symbol string, quantity, price, filled int64) *internal.Filler {
+	return internal.NewFillerFromState(
+		newRecord(ctrl, symbol),
+		decimal.NewFromInt(quantity),
+		decimal.NewFromInt(price),
+		decimal.NewFromInt(filled),
+	)
+}
+
+// newQueue creates a FillerQueue pre-populated with the given fillers.
+func newQueue(fillers ...*internal.Filler) *internal.FillerQueue {
+	q := new(internal.FillerQueue)
+	for _, f := range fillers {
+		q.Push(f)
+	}
+	return q
+}
+
+// newStore creates a FileStore backed by a temp file and returns the store
+// plus the path to the underlying state file.
+func newStore(t *testing.T, platform string, ser internal.RecordSerializer) (*internal.FileStore, string) {
+	t.Helper()
+	dir := t.TempDir()
+	path := filepath.Join(dir, "state.json")
+	store, err := internal.NewFileStore(path, platform, ser)
+	if err != nil {
+		t.Fatalf("NewFileStore returned unexpected error: %v", err)
+	}
+	return store, path
+}
+
+// roundTripSerializer returns a serializer mock whose MarshalRecord encodes
+// the Symbol into bytes and whose UnmarshalRecord decodes those bytes back
+// into a fresh MockRecord returning the encoded Symbol. Tests use this when
+// they need Save + Load to round-trip equivalent Records.
+func roundTripSerializer(ctrl *gomock.Controller) *mocks.MockRecordSerializer {
+	ser := mocks.NewMockRecordSerializer(ctrl)
+	ser.EXPECT().
+		MarshalRecord(gomock.Any(), gomock.Any()).
+		DoAndReturn(func(_ context.Context, r internal.Record) ([]byte, error) {
+			return []byte(r.Symbol()), nil
+		}).
+		AnyTimes()
+	ser.EXPECT().
+		UnmarshalRecord(gomock.Any(), gomock.Any()).
+		DoAndReturn(func(_ context.Context, b []byte) (internal.Record, error) {
+			return newRecord(ctrl, string(b)), nil
+		}).
+		AnyTimes()
+	return ser
+}
+
+// queueSnapshot drains the given FillerQueue (via Pop) and returns its
+// contents in a side-effect-free shape suitable for value comparison.
+// Callers should not use the queue afterwards.
+func queueSnapshot(q *internal.FillerQueue) []queueEntry {
+	if q == nil {
+		return nil
+	}
+	var out []queueEntry
+	for {
+		f, ok := q.Pop()
+		if !ok {
+			break
+		}
+		out = append(out, queueEntry{
+			symbol:   f.Symbol(),
+			quantity: f.Quantity(),
+			price:    f.Price(),
+			filled:   f.Filled(),
+		})
+	}
+	return out
+}
+
+// assertQueueEqual compares two FillerQueues by popping every element from
+// each and comparing the resulting sequence of queueEntries. Both queues are
+// drained as a side effect.
+func assertQueueEqual(t *testing.T, symbol string, got, want *internal.FillerQueue) {
+	t.Helper()
+	if got == nil {
+		t.Fatalf("symbol %q: loaded queue is nil", symbol)
+	}
+	if got.Len() != want.Len() {
+		t.Fatalf("symbol %q: want %d lots but got %d", symbol, want.Len(), got.Len())
+	}
+	wantEntries := queueSnapshot(want)
+	gotEntries := queueSnapshot(got)
+	for i := range wantEntries {
+		w := wantEntries[i]
+		g := gotEntries[i]
+		if w.symbol != g.symbol {
+			t.Errorf("symbol %q lot %d: want symbol %q but got %q",
+				symbol, i, w.symbol, g.symbol)
+		}
+		if !w.quantity.Equal(g.quantity) {
+			t.Errorf("symbol %q lot %d: want quantity %v but got %v",
+				symbol, i, w.quantity, g.quantity)
+		}
+		if !w.price.Equal(g.price) {
+			t.Errorf("symbol %q lot %d: want price %v but got %v",
+				symbol, i, w.price, g.price)
+		}
+		if !w.filled.Equal(g.filled) {
+			t.Errorf("symbol %q lot %d: want filled %v but got %v",
+				symbol, i, w.filled, g.filled)
+		}
+	}
+}
+
+type queueEntry struct {
+	symbol   string
+	quantity decimal.Decimal
+	price    decimal.Decimal
+	filled   decimal.Decimal
+}
diff --git a/internal/filler.go b/internal/filler.go
index ab1053e..4535ea1 100644
--- a/internal/filler.go
+++ b/internal/filler.go
@@ -22,10 +22,26 @@ func NewFiller(r Record) *Filler {
 	}
 }
 
+// NewFillerFromState constructs a Filler from a previously persisted state.
+// It bypasses the Record-derived defaults so callers can restore a lot that
+// may have been split-adjusted or partially filled since the Record was first
+// created.
+func NewFillerFromState(record Record, quantity, price, filled decimal.Decimal) *Filler {
+	return &Filler{
+		Record:   record,
+		filled:   filled,
+		quantity: quantity,
+		price:    price,
+	}
+}
+
 func (f *Filler) Quantity() decimal.Decimal { return f.quantity }
 
 func (f *Filler) Price() decimal.Decimal { return f.price }
 
+// Filled returns how much of the Filler's quantity has already been consumed.
+func (f *Filler) Filled() decimal.Decimal { return f.filled }
+
 // Fill accrues some quantity. Returns how mutch was accrued in the 1st return value and whether
 // it was filled or not on the 2nd return value.
 func (f *Filler) Fill(quantity decimal.Decimal) (decimal.Decimal, bool) {
@@ -70,8 +86,8 @@ func (fq *FillerQueue) Push(f *Filler) {
 	fq.l.PushBack(f)
 }
 
-// Pop removes and returns the first Filler of the queue in the 1st return value. If the list is
-// empty returns false on the 2nd return value, true otherwise.
+// Pop removes and returns the first Filler of the queue in the 1st return value if there is one. If
+// the queue is already empty returns false on the 2nd return value, otherwise returns true.
 func (fq *FillerQueue) Pop() (*Filler, bool) {
 	el := fq.frontElement()
 	if el == nil {
diff --git a/internal/filler_test.go b/internal/filler_test.go
index 6b5726d..7e90c83 100644
--- a/internal/filler_test.go
+++ b/internal/filler_test.go
@@ -271,3 +271,47 @@ func TestFillerQueue_AdjustForSplit_NilReceiver(t *testing.T) {
 	var fq *FillerQueue
 	fq.AdjustForSplit(decimal.NewFromFloat(5)) // must not panic
 }
+
+func TestNewFillerFromState(t *testing.T) {
+	// The underlying Record reports very different values; NewFillerFromState
+	// must ignore them and use the caller-supplied overrides instead.
+	rec := &testRecord{
+		quantity: decimal.NewFromFloat(999),
+		price:    decimal.NewFromFloat(999),
+	}
+
+	qty := decimal.NewFromFloat(50)
+	price := decimal.NewFromFloat(20)
+	filled := qty // fully filled on load
+
+	f := NewFillerFromState(rec, qty, price, filled)
+
+	if !f.Quantity().Equal(qty) {
+		t.Errorf("want quantity %v but got %v", qty, f.Quantity())
+	}
+	if !f.Price().Equal(price) {
+		t.Errorf("want price %v but got %v", price, f.Price())
+	}
+	if !f.IsFilled() {
+		t.Errorf("want IsFilled() to be true when filled == quantity")
+	}
+
+	// Partially filled: filled < quantity => IsFilled must be false.
+	partial := NewFillerFromState(rec, qty, price, decimal.NewFromFloat(10))
+	if partial.IsFilled() {
+		t.Errorf("want IsFilled() to be false when filled < quantity")
+	}
+	if !partial.Quantity().Equal(qty) {
+		t.Errorf("want quantity %v but got %v", qty, partial.Quantity())
+	}
+	if !partial.Price().Equal(price) {
+		t.Errorf("want price %v but got %v", price, partial.Price())
+	}
+
+	// Filled from Fill() on a restored lot must work correctly against the
+	// restored (not Record-derived) quantity/price.
+	_, done := partial.Fill(decimal.NewFromFloat(40))
+	if !done {
+		t.Errorf("after filling the remaining 40, IsFilled() should be true")
+	}
+}
diff --git a/internal/generate.go b/internal/generate.go
index a0a9c26..efffb8b 100644
--- a/internal/generate.go
+++ b/internal/generate.go
@@ -1,3 +1,3 @@
 package internal
 
-//go:generate go tool mockgen -destination=mocks/mocks_gen.go -package=mocks -typed . RecordReader,Record,ReportWriter
+//go:generate go tool mockgen -destination=mocks/mocks_gen.go -package=mocks -typed . RecordReader,Record,ReportWriter,RecordEncoder,RecordDecoder,RecordSerializer
diff --git a/internal/kind.go b/internal/kind.go
index 50c8af0..9eee9a4 100644
--- a/internal/kind.go
+++ b/internal/kind.go
@@ -7,11 +7,12 @@ const (
 	KindBuy
 	KindSell
 	KindSplit
+	sentinelKind
 )
 
-// String returns a human readable value
-func (d Kind) String() string {
-	switch d {
+// String returns a unique string value for Kind k
+func (k Kind) String() string {
+	switch k {
 	case KindBuy:
 		return "buy"
 	case KindSell:
@@ -23,8 +24,13 @@ func (d Kind) String() string {
 	}
 }
 
-// Is returns true when k equals o
+// Valid returns true if k is an accepted value for the Kind type
+func (k Kind) Valid() bool {
+	return k > 0 && k < sentinelKind
+}
+
+// Is returns true when k and o are valid and equal.
 func (k Kind) Is(o any) bool {
 	other, ok := o.(Kind)
-	return ok && k == other
+	return ok && k.Valid() && k == other
 }
diff --git a/internal/kind_test.go b/internal/kind_test.go
index a52d7e6..c5af02b 100644
--- a/internal/kind_test.go
+++ b/internal/kind_test.go
@@ -1,60 +1,95 @@
 package internal
 
-import "testing"
+import (
+	"fmt"
+	"testing"
+)
 
 func TestSide_String(t *testing.T) {
-	tests := []struct {
-		name string
-		side Kind
-		want string
-	}{
-		{"buy", KindBuy, "buy"},
-		{"sell", KindSell, "sell"},
-		{"unknown", KindUnknown, "unknown"},
-	}
-	for _, tt := range tests {
-		t.Run(tt.name, func(t *testing.T) {
-			if got := tt.side.String(); got != tt.want {
-				t.Errorf("want Side.String() to be %v but got %v", tt.want, got)
+	const unknown = "unknown"
+
+	seen := make(map[string]Kind, sentinelKind)
+	for k := Kind(1); k < sentinelKind; k++ {
+		t.Run(fmt.Sprintf("Kind %d", k), func(t *testing.T) {
+			str := k.String()
+
+			if other, ok := seen[str]; ok {
+				t.Errorf("want Kind(%d).String to be unique but was a duplicate of Kind(%d)", k, other)
+			} else {
+				seen[str] = k
+			}
+
+			if len(str) == 0 {
+				t.Errorf("want Kind(%d).String to be non-empty", k)
+			}
+
+			if str == unknown {
+				t.Errorf("want Kind(%d).String to be a known value", k)
 			}
 		})
 	}
+
+	if KindUnknown.String() != unknown {
+		t.Errorf("want Kind(0) to be unknown")
+	}
+
+	if Kind(sentinelKind).String() != unknown {
+		t.Errorf("want Kind(%d) to be unknown", sentinelKind)
+	}
 }
 
-func TestSide_IsBuy(t *testing.T) {
-	tests := []struct {
-		name string
-		side Kind
-		want bool
-	}{
-		{"buy", KindBuy, true},
-		{"sell", KindSell, false},
-		{"unknown", KindUnknown, false},
+func TestSide_Valid(t *testing.T) {
+	for k := Kind(1); k < sentinelKind; k++ {
+		if !k.Valid() {
+			t.Errorf("want %s(%d) to be valid", k, k)
+		}
 	}
-	for _, tt := range tests {
-		t.Run(tt.name, func(t *testing.T) {
-			if got := tt.side.Is(KindBuy); got != tt.want {
-				t.Errorf("want Side.IsBuy() to be %v but got %v", tt.want, got)
-			}
-		})
+
+	if KindUnknown.Valid() {
+		t.Errorf("want Kind(0) to be invalid")
+	}
+
+	if Kind(sentinelKind).Valid() {
+		t.Errorf("want Kind(%d) to be invalid", sentinelKind)
 	}
 }
 
-func TestSide_IsSell(t *testing.T) {
-	tests := []struct {
-		name string
-		side Kind
-		want bool
-	}{
-		{"buy", KindBuy, false},
-		{"sell", KindSell, true},
-		{"unknown", KindUnknown, false},
-	}
-	for _, tt := range tests {
-		t.Run(tt.name, func(t *testing.T) {
-			if got := tt.side.Is(KindSell); got != tt.want {
-				t.Errorf("want Side.IsSell() to be %v but got %v", tt.want, got)
+func TestSide_Is(t *testing.T) {
+	t.Run("valid is self", func(t *testing.T) {
+		for k := Kind(1); k < sentinelKind; k++ {
+			if !k.Is(k) {
+				t.Errorf("want Kind(%d).Is(%d) to be true", k, k)
 			}
-		})
-	}
+		}
+	})
+
+	t.Run("valid is unknown", func(t *testing.T) {
+		for k := Kind(1); k < sentinelKind; k++ {
+			if k.Is(KindUnknown) {
+				t.Errorf("want Kind(%d).Is(0) to be false", k)
+			}
+
+			if k.Is(sentinelKind) {
+				t.Errorf("want Kind(%d).Is(%d) to be false", k, sentinelKind)
+			}
+
+			if k.Is(struct{}{}) {
+				t.Errorf("want Kind(%d).Is(other type) to be false", k)
+			}
+		}
+	})
+
+	t.Run("unknown is unknown", func(t *testing.T) {
+		if KindUnknown.Is(KindUnknown) {
+			t.Errorf("want Kind(0).Is(0) to be false")
+		}
+
+		if KindUnknown.Is(sentinelKind) {
+			t.Errorf("want Kind(0).Is(%d) to be false", sentinelKind)
+		}
+
+		if sentinelKind.Is(sentinelKind) {
+			t.Errorf("want Kind(%d).Is(%d) to be false", sentinelKind, sentinelKind)
+		}
+	})
 }
diff --git a/internal/mocks/mocks_gen.go b/internal/mocks/mocks_gen.go
index 427c3f4..059b76d 100644
--- a/internal/mocks/mocks_gen.go
+++ b/internal/mocks/mocks_gen.go
@@ -1,9 +1,9 @@
 // Code generated by MockGen. DO NOT EDIT.
-// Source: github.com/nmoniz/any2anexoj/internal (interfaces: RecordReader,Record,ReportWriter)
+// Source: github.com/nmoniz/any2anexoj/internal (interfaces: RecordReader,Record,ReportWriter,RecordEncoder,RecordDecoder,RecordSerializer)
 //
 // Generated by this command:
 //
-//	mockgen -destination=mocks/mocks_gen.go -package=mocks -typed . RecordReader,Record,ReportWriter
+//	mockgen -destination=mocks/mocks_gen.go -package=mocks -typed . RecordReader,Record,ReportWriter,RecordEncoder,RecordDecoder,RecordSerializer
 //
 
 // Package mocks is a generated GoMock package.
@@ -547,3 +547,231 @@ func (c *MockReportWriterWriteCall) DoAndReturn(f func(context.Context, internal
 	c.Call = c.Call.DoAndReturn(f)
 	return c
 }
+
+// MockRecordEncoder is a mock of RecordEncoder interface.
+type MockRecordEncoder struct {
+	ctrl     *gomock.Controller
+	recorder *MockRecordEncoderMockRecorder
+	isgomock struct{}
+}
+
+// MockRecordEncoderMockRecorder is the mock recorder for MockRecordEncoder.
+type MockRecordEncoderMockRecorder struct {
+	mock *MockRecordEncoder
+}
+
+// NewMockRecordEncoder creates a new mock instance.
+func NewMockRecordEncoder(ctrl *gomock.Controller) *MockRecordEncoder {
+	mock := &MockRecordEncoder{ctrl: ctrl}
+	mock.recorder = &MockRecordEncoderMockRecorder{mock}
+	return mock
+}
+
+// EXPECT returns an object that allows the caller to indicate expected use.
+func (m *MockRecordEncoder) EXPECT() *MockRecordEncoderMockRecorder {
+	return m.recorder
+}
+
+// MarshalRecord mocks base method.
+func (m *MockRecordEncoder) MarshalRecord(arg0 context.Context, arg1 internal.Record) ([]byte, error) {
+	m.ctrl.T.Helper()
+	ret := m.ctrl.Call(m, "MarshalRecord", arg0, arg1)
+	ret0, _ := ret[0].([]byte)
+	ret1, _ := ret[1].(error)
+	return ret0, ret1
+}
+
+// MarshalRecord indicates an expected call of MarshalRecord.
+func (mr *MockRecordEncoderMockRecorder) MarshalRecord(arg0, arg1 any) *MockRecordEncoderMarshalRecordCall {
+	mr.mock.ctrl.T.Helper()
+	call := mr.mock.ctrl.RecordCallWithMethodType(mr.mock, "MarshalRecord", reflect.TypeOf((*MockRecordEncoder)(nil).MarshalRecord), arg0, arg1)
+	return &MockRecordEncoderMarshalRecordCall{Call: call}
+}
+
+// MockRecordEncoderMarshalRecordCall wrap *gomock.Call
+type MockRecordEncoderMarshalRecordCall struct {
+	*gomock.Call
+}
+
+// Return rewrite *gomock.Call.Return
+func (c *MockRecordEncoderMarshalRecordCall) Return(arg0 []byte, arg1 error) *MockRecordEncoderMarshalRecordCall {
+	c.Call = c.Call.Return(arg0, arg1)
+	return c
+}
+
+// Do rewrite *gomock.Call.Do
+func (c *MockRecordEncoderMarshalRecordCall) Do(f func(context.Context, internal.Record) ([]byte, error)) *MockRecordEncoderMarshalRecordCall {
+	c.Call = c.Call.Do(f)
+	return c
+}
+
+// DoAndReturn rewrite *gomock.Call.DoAndReturn
+func (c *MockRecordEncoderMarshalRecordCall) DoAndReturn(f func(context.Context, internal.Record) ([]byte, error)) *MockRecordEncoderMarshalRecordCall {
+	c.Call = c.Call.DoAndReturn(f)
+	return c
+}
+
+// MockRecordDecoder is a mock of RecordDecoder interface.
+type MockRecordDecoder struct {
+	ctrl     *gomock.Controller
+	recorder *MockRecordDecoderMockRecorder
+	isgomock struct{}
+}
+
+// MockRecordDecoderMockRecorder is the mock recorder for MockRecordDecoder.
+type MockRecordDecoderMockRecorder struct {
+	mock *MockRecordDecoder
+}
+
+// NewMockRecordDecoder creates a new mock instance.
+func NewMockRecordDecoder(ctrl *gomock.Controller) *MockRecordDecoder {
+	mock := &MockRecordDecoder{ctrl: ctrl}
+	mock.recorder = &MockRecordDecoderMockRecorder{mock}
+	return mock
+}
+
+// EXPECT returns an object that allows the caller to indicate expected use.
+func (m *MockRecordDecoder) EXPECT() *MockRecordDecoderMockRecorder {
+	return m.recorder
+}
+
+// UnmarshalRecord mocks base method.
+func (m *MockRecordDecoder) UnmarshalRecord(arg0 context.Context, arg1 []byte) (internal.Record, error) {
+	m.ctrl.T.Helper()
+	ret := m.ctrl.Call(m, "UnmarshalRecord", arg0, arg1)
+	ret0, _ := ret[0].(internal.Record)
+	ret1, _ := ret[1].(error)
+	return ret0, ret1
+}
+
+// UnmarshalRecord indicates an expected call of UnmarshalRecord.
+func (mr *MockRecordDecoderMockRecorder) UnmarshalRecord(arg0, arg1 any) *MockRecordDecoderUnmarshalRecordCall {
+	mr.mock.ctrl.T.Helper()
+	call := mr.mock.ctrl.RecordCallWithMethodType(mr.mock, "UnmarshalRecord", reflect.TypeOf((*MockRecordDecoder)(nil).UnmarshalRecord), arg0, arg1)
+	return &MockRecordDecoderUnmarshalRecordCall{Call: call}
+}
+
+// MockRecordDecoderUnmarshalRecordCall wrap *gomock.Call
+type MockRecordDecoderUnmarshalRecordCall struct {
+	*gomock.Call
+}
+
+// Return rewrite *gomock.Call.Return
+func (c *MockRecordDecoderUnmarshalRecordCall) Return(arg0 internal.Record, arg1 error) *MockRecordDecoderUnmarshalRecordCall {
+	c.Call = c.Call.Return(arg0, arg1)
+	return c
+}
+
+// Do rewrite *gomock.Call.Do
+func (c *MockRecordDecoderUnmarshalRecordCall) Do(f func(context.Context, []byte) (internal.Record, error)) *MockRecordDecoderUnmarshalRecordCall {
+	c.Call = c.Call.Do(f)
+	return c
+}
+
+// DoAndReturn rewrite *gomock.Call.DoAndReturn
+func (c *MockRecordDecoderUnmarshalRecordCall) DoAndReturn(f func(context.Context, []byte) (internal.Record, error)) *MockRecordDecoderUnmarshalRecordCall {
+	c.Call = c.Call.DoAndReturn(f)
+	return c
+}
+
+// MockRecordSerializer is a mock of RecordSerializer interface.
+type MockRecordSerializer struct {
+	ctrl     *gomock.Controller
+	recorder *MockRecordSerializerMockRecorder
+	isgomock struct{}
+}
+
+// MockRecordSerializerMockRecorder is the mock recorder for MockRecordSerializer.
+type MockRecordSerializerMockRecorder struct {
+	mock *MockRecordSerializer
+}
+
+// NewMockRecordSerializer creates a new mock instance.
+func NewMockRecordSerializer(ctrl *gomock.Controller) *MockRecordSerializer {
+	mock := &MockRecordSerializer{ctrl: ctrl}
+	mock.recorder = &MockRecordSerializerMockRecorder{mock}
+	return mock
+}
+
+// EXPECT returns an object that allows the caller to indicate expected use.
+func (m *MockRecordSerializer) EXPECT() *MockRecordSerializerMockRecorder {
+	return m.recorder
+}
+
+// MarshalRecord mocks base method.
+func (m *MockRecordSerializer) MarshalRecord(arg0 context.Context, arg1 internal.Record) ([]byte, error) {
+	m.ctrl.T.Helper()
+	ret := m.ctrl.Call(m, "MarshalRecord", arg0, arg1)
+	ret0, _ := ret[0].([]byte)
+	ret1, _ := ret[1].(error)
+	return ret0, ret1
+}
+
+// MarshalRecord indicates an expected call of MarshalRecord.
+func (mr *MockRecordSerializerMockRecorder) MarshalRecord(arg0, arg1 any) *MockRecordSerializerMarshalRecordCall {
+	mr.mock.ctrl.T.Helper()
+	call := mr.mock.ctrl.RecordCallWithMethodType(mr.mock, "MarshalRecord", reflect.TypeOf((*MockRecordSerializer)(nil).MarshalRecord), arg0, arg1)
+	return &MockRecordSerializerMarshalRecordCall{Call: call}
+}
+
+// MockRecordSerializerMarshalRecordCall wrap *gomock.Call
+type MockRecordSerializerMarshalRecordCall struct {
+	*gomock.Call
+}
+
+// Return rewrite *gomock.Call.Return
+func (c *MockRecordSerializerMarshalRecordCall) Return(arg0 []byte, arg1 error) *MockRecordSerializerMarshalRecordCall {
+	c.Call = c.Call.Return(arg0, arg1)
+	return c
+}
+
+// Do rewrite *gomock.Call.Do
+func (c *MockRecordSerializerMarshalRecordCall) Do(f func(context.Context, internal.Record) ([]byte, error)) *MockRecordSerializerMarshalRecordCall {
+	c.Call = c.Call.Do(f)
+	return c
+}
+
+// DoAndReturn rewrite *gomock.Call.DoAndReturn
+func (c *MockRecordSerializerMarshalRecordCall) DoAndReturn(f func(context.Context, internal.Record) ([]byte, error)) *MockRecordSerializerMarshalRecordCall {
+	c.Call = c.Call.DoAndReturn(f)
+	return c
+}
+
+// UnmarshalRecord mocks base method.
+func (m *MockRecordSerializer) UnmarshalRecord(arg0 context.Context, arg1 []byte) (internal.Record, error) {
+	m.ctrl.T.Helper()
+	ret := m.ctrl.Call(m, "UnmarshalRecord", arg0, arg1)
+	ret0, _ := ret[0].(internal.Record)
+	ret1, _ := ret[1].(error)
+	return ret0, ret1
+}
+
+// UnmarshalRecord indicates an expected call of UnmarshalRecord.
+func (mr *MockRecordSerializerMockRecorder) UnmarshalRecord(arg0, arg1 any) *MockRecordSerializerUnmarshalRecordCall {
+	mr.mock.ctrl.T.Helper()
+	call := mr.mock.ctrl.RecordCallWithMethodType(mr.mock, "UnmarshalRecord", reflect.TypeOf((*MockRecordSerializer)(nil).UnmarshalRecord), arg0, arg1)
+	return &MockRecordSerializerUnmarshalRecordCall{Call: call}
+}
+
+// MockRecordSerializerUnmarshalRecordCall wrap *gomock.Call
+type MockRecordSerializerUnmarshalRecordCall struct {
+	*gomock.Call
+}
+
+// Return rewrite *gomock.Call.Return
+func (c *MockRecordSerializerUnmarshalRecordCall) Return(arg0 internal.Record, arg1 error) *MockRecordSerializerUnmarshalRecordCall {
+	c.Call = c.Call.Return(arg0, arg1)
+	return c
+}
+
+// Do rewrite *gomock.Call.Do
+func (c *MockRecordSerializerUnmarshalRecordCall) Do(f func(context.Context, []byte) (internal.Record, error)) *MockRecordSerializerUnmarshalRecordCall {
+	c.Call = c.Call.Do(f)
+	return c
+}
+
+// DoAndReturn rewrite *gomock.Call.DoAndReturn
+func (c *MockRecordSerializerUnmarshalRecordCall) DoAndReturn(f func(context.Context, []byte) (internal.Record, error)) *MockRecordSerializerUnmarshalRecordCall {
+	c.Call = c.Call.DoAndReturn(f)
+	return c
+}
diff --git a/internal/open_figi.go b/internal/ofigi/client.go
similarity index 93%
rename from internal/open_figi.go
rename to internal/ofigi/client.go
index d4bce71..b969cde 100644
--- a/internal/open_figi.go
+++ b/internal/ofigi/client.go
@@ -1,4 +1,4 @@
-package internal
+package ofigi
 
 import (
 	"bytes"
@@ -16,8 +16,8 @@ import (
 
 var OpenFIGIAPIKeyHeader = http.CanonicalHeaderKey("X-OPENFIGI-APIKEY")
 
-// OpenFIGI is a small adapter for the openfigi.com api.
-type OpenFIGI struct {
+// Client is a thin adapter for the openfigi.com api.
+type Client struct {
 	client         *http.Client
 	apiKey         string
 	mappingLimiter *rate.Limiter
@@ -25,12 +25,13 @@ type OpenFIGI struct {
 	mu sync.RWMutex
 	// TODO: there's no eviction policy at the moment as this is only used by short-lived application
 	// which processes a relatively small amount of records. We need to consider using an external
-	// cache lib (like golang-lru or go-cache) if this becomes a problem or implement this ourselves.
+	// cache lib (like golang-lru or go-cache) if this becomes a problem or implement eviction
+	// ourselves.
 	securityTypeCache map[string]string
 }
 
 // NewOpenFIGI creates an OpenFIGI client that uses the API key if provided
-func NewOpenFIGI(c *http.Client, apiKey string) *OpenFIGI {
+func NewOpenFIGI(c *http.Client, apiKey string) *Client {
 	// Rate limits as per https://www.openfigi.com/api/documentation#rate-limits
 	limiter := rate.NewLimiter(rate.Every(time.Minute), 25)
 	if len(apiKey) > 0 {
@@ -40,7 +41,7 @@ func NewOpenFIGI(c *http.Client, apiKey string) *OpenFIGI {
 		slog.Debug("OpenFIGI client: created with puplic rate limits")
 	}
 
-	return &OpenFIGI{
+	return &Client{
 		client:            c,
 		apiKey:            apiKey,
 		mappingLimiter:    limiter,
@@ -48,7 +49,7 @@ func NewOpenFIGI(c *http.Client, apiKey string) *OpenFIGI {
 	}
 }
 
-func (of *OpenFIGI) SecurityTypeByISIN(ctx context.Context, isin string) (string, error) {
+func (of *Client) SecurityTypeByISIN(ctx context.Context, isin string) (string, error) {
 	of.mu.RLock()
 	if secType, ok := of.securityTypeCache[isin]; ok {
 		of.mu.RUnlock()
diff --git a/internal/open_figi_test.go b/internal/ofigi/client_test.go
similarity index 88%
rename from internal/open_figi_test.go
rename to internal/ofigi/client_test.go
index 3b31107..a203c8b 100644
--- a/internal/open_figi_test.go
+++ b/internal/ofigi/client_test.go
@@ -1,15 +1,14 @@
-package internal_test
+package ofigi_test
 
 import (
 	"bytes"
-	"context"
 	"fmt"
 	"io"
 	"net/http"
 	"testing"
 	"time"
 
-	"github.com/nmoniz/any2anexoj/internal"
+	"github.com/nmoniz/any2anexoj/internal/ofigi"
 )
 
 func TestOpenFIGI_SecurityTypeByISIN(t *testing.T) {
@@ -110,9 +109,9 @@ func TestOpenFIGI_SecurityTypeByISIN(t *testing.T) {
 	}
 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {
-			of := internal.NewOpenFIGI(tt.client, "")
+			of := ofigi.NewOpenFIGI(tt.client, "")
 
-			got, gotErr := of.SecurityTypeByISIN(context.Background(), tt.isin)
+			got, gotErr := of.SecurityTypeByISIN(t.Context(), tt.isin)
 			if gotErr != nil {
 				if !tt.wantErr {
 					t.Errorf("want success but failed: %v", gotErr)
@@ -145,7 +144,7 @@ func TestOpenFIGI_SecurityTypeByISIN_Cache(t *testing.T) {
 		}, nil
 	})
 
-	of := internal.NewOpenFIGI(c, "")
+	of := ofigi.NewOpenFIGI(c, "")
 
 	got, gotErr := of.SecurityTypeByISIN(t.Context(), "NL0000235190")
 	if gotErr != nil {
@@ -171,15 +170,15 @@ func TestOpenFIGI_SecurityTypeByISIN_APIKey(t *testing.T) {
 		wantAPIKey := "123abc-456xyz"
 
 		c := NewTestClient(t, func(req *http.Request) (*http.Response, error) {
-			value, ok := req.Header[internal.OpenFIGIAPIKeyHeader]
+			value, ok := req.Header[ofigi.OpenFIGIAPIKeyHeader]
 			if !ok {
-				t.Fatalf("want %q header but got none: %v", internal.OpenFIGIAPIKeyHeader, req.Header)
+				t.Fatalf("want %q header but got none: %v", ofigi.OpenFIGIAPIKeyHeader, req.Header)
 			}
 			if len(value) != 1 {
-				t.Fatalf("want exactly one %q header value but got %d", internal.OpenFIGIAPIKeyHeader, len(value))
+				t.Fatalf("want exactly one %q header value but got %d", ofigi.OpenFIGIAPIKeyHeader, len(value))
 			}
 			if value[0] != wantAPIKey {
-				t.Fatalf("want %q header value %q but got %q", internal.OpenFIGIAPIKeyHeader, wantAPIKey, value[0])
+				t.Fatalf("want %q header value %q but got %q", ofigi.OpenFIGIAPIKeyHeader, wantAPIKey, value[0])
 			}
 			return &http.Response{
 				Status:     http.StatusText(http.StatusOK),
@@ -187,7 +186,7 @@ func TestOpenFIGI_SecurityTypeByISIN_APIKey(t *testing.T) {
 				Body:       io.NopCloser(bytes.NewBufferString(`[{"data":[{"securityType":"Common Stock"}]}]`)),
 			}, nil
 		})
-		of := internal.NewOpenFIGI(c, wantAPIKey)
+		of := ofigi.NewOpenFIGI(c, wantAPIKey)
 
 		_, err := of.SecurityTypeByISIN(t.Context(), "US1234567890")
 		if err != nil {
@@ -197,9 +196,9 @@ func TestOpenFIGI_SecurityTypeByISIN_APIKey(t *testing.T) {
 
 	t.Run("without API key", func(t *testing.T) {
 		c := NewTestClient(t, func(req *http.Request) (*http.Response, error) {
-			_, ok := req.Header[internal.OpenFIGIAPIKeyHeader]
+			_, ok := req.Header[ofigi.OpenFIGIAPIKeyHeader]
 			if ok {
-				t.Fatalf("want no %s header but got one", internal.OpenFIGIAPIKeyHeader)
+				t.Fatalf("want no %s header but got one", ofigi.OpenFIGIAPIKeyHeader)
 			}
 			return &http.Response{
 				Status:     http.StatusText(http.StatusOK),
@@ -207,7 +206,7 @@ func TestOpenFIGI_SecurityTypeByISIN_APIKey(t *testing.T) {
 				Body:       io.NopCloser(bytes.NewBufferString(`[{"data":[{"securityType":"Common Stock"}]}]`)),
 			}, nil
 		})
-		of := internal.NewOpenFIGI(c, "")
+		of := ofigi.NewOpenFIGI(c, "")
 		_, err := of.SecurityTypeByISIN(t.Context(), "US1234567890")
 		if err != nil {
 			t.Fatalf("want success but got an error: %s", err)
diff --git a/internal/report.go b/internal/report.go
index b8e5a59..1e1eca7 100644
--- a/internal/report.go
+++ b/internal/report.go
@@ -51,18 +51,58 @@ type ReportWriter interface {
 	Write(context.Context, ReportItem) error
 }
 
+type optionals struct {
+	selector Selector
+	store    Store
+}
+
+func applyOptions(defaults optionals, opts []Option) optionals {
+	for _, opt := range opts {
+		opt(&defaults)
+	}
+	return defaults
+}
+
+type Option func(*optionals)
+
 // Selector returns true if a record should be selected for processing, false otherwise.
 type Selector func(Record) bool
 
+func WithSelector(s Selector) Option {
+	return func(o *optionals) {
+		o.selector = s
+	}
+}
+
+type Store interface {
+	Load(context.Context) (map[string]*FillerQueue, error)
+	Save(context.Context, map[string]*FillerQueue) error
+}
+
+func WithStore(s Store) Option {
+	return func(o *optionals) {
+		o.store = s
+	}
+}
+
 // BuildReport reads records from a RecordReader and, if the record passes the Selector, it is
 // processed into the ReportWriter.
-func BuildReport(ctx context.Context, reader RecordReader, writer ReportWriter, sel Selector) error {
-	buys := make(map[string]*FillerQueue)
+func BuildReport(ctx context.Context, reader RecordReader, writer ReportWriter, options ...Option) error {
+	optionals := applyOptions(optionals{
+		selector: Any(),
+		store:    EphemeralStore{},
+	}, options)
 
-	var buysCount, sellsCount int64
-	var lastTimestamp time.Time
-	progTicker := time.NewTicker(10 * time.Second)
+	buys, err := optionals.store.Load(ctx)
+	if err != nil {
+		return fmt.Errorf("loading state: %w", err)
+	}
 
+	var (
+		recordsCount  int64
+		lastTimestamp time.Time
+		progTicker    = time.NewTicker(10 * time.Second)
+	)
 	for {
 		select {
 		case <-ctx.Done():
@@ -70,27 +110,29 @@ func BuildReport(ctx context.Context, reader RecordReader, writer ReportWriter,
 		case <-progTicker.C:
 			slog.InfoContext(
 				ctx, "Progress update",
-				slog.Int64("total_records", buysCount+sellsCount),
-				slog.Int64("sell_records", sellsCount),
-				slog.Int64("buy_records", buysCount),
+				slog.Int64("records_count", recordsCount),
 				slog.Time("last_record_timestamp", lastTimestamp),
 			)
 		default:
 			rec, err := reader.ReadRecord(ctx)
 			if err != nil {
 				if errors.Is(err, io.EOF) {
+					err = optionals.store.Save(ctx, buys)
+					if err != nil {
+						return fmt.Errorf("saving state: %w", err)
+					}
+
 					return nil
 				}
 				return err
 			}
 
-			if rec.Kind().Is(KindBuy) {
-				buysCount++
-			} else if rec.Kind().Is(KindSell) {
-				sellsCount++
+			if !rec.Kind().Valid() {
+				return fmt.Errorf("found invalid Kind(%d)", rec.Kind())
 			}
 
 			lastTimestamp = rec.Timestamp()
+			recordsCount++
 
 			buyQueue, ok := buys[rec.Symbol()]
 			if !ok {
@@ -98,21 +140,16 @@ func BuildReport(ctx context.Context, reader RecordReader, writer ReportWriter,
 				buys[rec.Symbol()] = buyQueue
 			}
 
-			err = processRecord(ctx, buyQueue, rec, sel, writer)
+			err = processRecord(ctx, buyQueue, rec, optionals.selector, writer)
 			if err != nil {
 				return fmt.Errorf("processing record: %w", err)
 			}
-
 		}
 	}
 }
 
 // processRecord either adds buys to the queue or consumes buys from the queue when processing a
 // sell record.
-//
-// NOTE: Selectors are only applied when processing sell records for performance reasons. It's much
-// cheaper to just accumulate buys and only actually inspect any records once a sell happens. This
-// avoids potential network requests to for every single record.
 func processRecord(ctx context.Context, q *FillerQueue, rec Record, sel Selector, writer ReportWriter) error {
 	slog.Debug(
 		"Report: processing record",
@@ -122,6 +159,9 @@ func processRecord(ctx context.Context, q *FillerQueue, rec Record, sel Selector
 
 	switch rec.Kind() {
 	case KindBuy:
+		// Selectors are only applied when processing sell records for performance reasons. It's much
+		// cheaper to just accumulate buys and only actually inspect any records once a sell happens. This
+		// avoids potential network requests to for every single record.
 		q.Push(NewFiller(rec))
 
 	case KindSell:
@@ -142,11 +182,6 @@ func processRecord(ctx context.Context, q *FillerQueue, rec Record, sel Selector
 				return ErrInsufficientBoughtVolume
 			}
 
-			// Since we don't apply selectors while processing buys we need to apply them here.
-			if !sel(buy) {
-				continue
-			}
-
 			matchedQty, filled := buy.Fill(unmatchedQty)
 
 			if filled {
diff --git a/internal/report_test.go b/internal/report_test.go
index 5c5d024..c08748d 100644
--- a/internal/report_test.go
+++ b/internal/report_test.go
@@ -4,6 +4,7 @@ import (
 	"context"
 	"fmt"
 	"io"
+	"reflect"
 	"testing"
 	"time"
 
@@ -43,7 +44,7 @@ func TestBuildReport(t *testing.T) {
 		Taxes:         decimal.Decimal{},
 	})).Times(1)
 
-	gotErr := internal.BuildReport(t.Context(), reader, writer, internal.Any())
+	gotErr := internal.BuildReport(t.Context(), reader, writer)
 	if gotErr != nil {
 		t.Fatalf("got unexpected err: %v", gotErr)
 	}
@@ -98,3 +99,87 @@ func (m ReportItemMatcher) String() string {
 }
 
 var _ gomock.Matcher = (*ReportItemMatcher)(nil)
+
+// recordingStore is a test fake for internal.Store that records how many
+// times Load/Save were invoked and captures the maps it handed back so a
+// test can verify BuildReport wires the store correctly.
+type recordingStore struct {
+	loadCalls int
+	saveCalls int
+	loaded    map[string]*internal.FillerQueue
+	saved     map[string]*internal.FillerQueue
+}
+
+func (s *recordingStore) Load(_ context.Context) (map[string]*internal.FillerQueue, error) {
+	s.loadCalls++
+	if s.loaded == nil {
+		s.loaded = map[string]*internal.FillerQueue{}
+	}
+	return s.loaded, nil
+}
+
+func (s *recordingStore) Save(_ context.Context, queues map[string]*internal.FillerQueue) error {
+	s.saveCalls++
+	s.saved = queues
+	return nil
+}
+
+func TestBuildReport_WithStore(t *testing.T) {
+	now := time.Now()
+	ctrl := gomock.NewController(t)
+
+	reader := mocks.NewMockRecordReader(ctrl)
+	records := []internal.Record{
+		mockRecord(ctrl, 20.0, 10.0, internal.KindBuy, now),
+	}
+	reader.EXPECT().ReadRecord(gomock.Any()).DoAndReturn(func(ctx context.Context) (internal.Record, error) {
+		if len(records) > 0 {
+			r := records[0]
+			records = records[1:]
+			return r, nil
+		}
+		return nil, io.EOF
+	}).Times(2)
+
+	// No sells, so the writer must not be called.
+	writer := mocks.NewMockReportWriter(ctrl)
+
+	store := &recordingStore{}
+
+	gotErr := internal.BuildReport(t.Context(), reader, writer, internal.WithStore(store))
+	if gotErr != nil {
+		t.Fatalf("got unexpected err: %v", gotErr)
+	}
+
+	if store.loadCalls != 1 {
+		t.Errorf("Load calls: want 1 but got %d", store.loadCalls)
+	}
+	if store.saveCalls != 1 {
+		t.Errorf("Save calls: want 1 but got %d", store.saveCalls)
+	}
+
+	// Load must run before any records are read, so it has already been
+	// invoked by the time Save is observed.
+	if store.loadCalls < store.saveCalls {
+		t.Errorf("Load (%d) should be called at least as many times as Save (%d)", store.loadCalls, store.saveCalls)
+	}
+
+	if store.loaded == nil {
+		t.Fatalf("Load was not called or returned a nil map")
+	}
+	if store.saved == nil {
+		t.Fatalf("Save was not called or received a nil map")
+	}
+
+	// The map handed to Save must be the same map returned by Load so
+	// that buy-queue mutations done while processing flow into Save.
+	if reflect.ValueOf(store.loaded).Pointer() != reflect.ValueOf(store.saved).Pointer() {
+		t.Errorf("map passed to Save is not the same map returned by Load")
+	}
+
+	// Sanity: the buy record above should have populated an entry for the
+	// "TEST" symbol in the shared map.
+	if _, ok := store.saved["TEST"]; !ok {
+		t.Errorf("want saved map to contain symbol %q but it was missing", "TEST")
+	}
+}
diff --git a/internal/state.go b/internal/state.go
new file mode 100644
index 0000000..ad70c5f
--- /dev/null
+++ b/internal/state.go
@@ -0,0 +1,46 @@
+package internal
+
+import (
+	"context"
+
+	"github.com/shopspring/decimal"
+)
+
+// StateVersion is the schema version of the persisted State struct.
+const StateVersion = "1"
+
+// State is the platform-agnostic representation of the buy-queue state that is
+// written to disk after a successful run and reloaded on the next run.
+type State struct {
+	Version  string                       `json:"version"`
+	Platform string                       `json:"platform"`
+	Queues   map[string][]persistedFiller `json:"queues"`
+}
+
+// persistedFiller is the on-disk representation of a single Filler. The
+// Record-specific data is kept as opaque bytes so the internal package does
+// not need to know about any broker package's concrete Record type.
+type persistedFiller struct {
+	RecordData []byte          `json:"record_data"`
+	Quantity   decimal.Decimal `json:"quantity"`
+	Price      decimal.Decimal `json:"price"`
+	Filled     decimal.Decimal `json:"filled"`
+}
+
+// RecordEncoder encodes a Record into its broker-specific byte representation.
+type RecordEncoder interface {
+	MarshalRecord(context.Context, Record) ([]byte, error)
+}
+
+// RecordDecoder decodes broker-specific bytes back into a Record.
+type RecordDecoder interface {
+	UnmarshalRecord(context.Context, []byte) (Record, error)
+}
+
+// RecordSerializer composes encoding and decoding of Records. Broker packages
+// own the implementation so that lazy/closured Record fields can be re-wired
+// on load.
+type RecordSerializer interface {
+	RecordEncoder
+	RecordDecoder
+}
diff --git a/internal/trading212/record.go b/internal/trading212/record.go
index 5d456d1..b34f05b 100644
--- a/internal/trading212/record.go
+++ b/internal/trading212/record.go
@@ -12,6 +12,7 @@ import (
 
 	"github.com/biter777/countries"
 	"github.com/nmoniz/any2anexoj/internal"
+	"github.com/nmoniz/any2anexoj/internal/ofigi"
 	"github.com/shopspring/decimal"
 )
 
@@ -70,10 +71,10 @@ func (r Record) Nature() internal.Nature {
 
 type RecordReader struct {
 	reader *csv.Reader
-	figi   *internal.OpenFIGI
+	figi   *ofigi.Client
 }
 
-func NewRecordReader(r io.Reader, f *internal.OpenFIGI) *RecordReader {
+func NewRecordReader(r io.Reader, f *ofigi.Client) *RecordReader {
 	return &RecordReader{
 		reader: csv.NewReader(r),
 		figi:   f,
@@ -187,7 +188,7 @@ func (rr RecordReader) ReadRecord(ctx context.Context) (internal.Record, error)
 	}
 }
 
-func figiNatureGetter(ctx context.Context, of *internal.OpenFIGI, isin string) func() internal.Nature {
+func figiNatureGetter(ctx context.Context, of *ofigi.Client, isin string) func() internal.Nature {
 	return sync.OnceValue(func() internal.Nature {
 		secType, err := of.SecurityTypeByISIN(ctx, isin)
 		if err != nil {
diff --git a/internal/trading212/record_test.go b/internal/trading212/record_test.go
index d38d32b..ba53cba 100644
--- a/internal/trading212/record_test.go
+++ b/internal/trading212/record_test.go
@@ -9,6 +9,7 @@ import (
 	"time"
 
 	"github.com/nmoniz/any2anexoj/internal"
+	"github.com/nmoniz/any2anexoj/internal/ofigi"
 	"github.com/shopspring/decimal"
 )
 
@@ -221,7 +222,7 @@ func TestRecordReader_ReadRecord_Split(t *testing.T) {
 func Test_figiNatureGetter(t *testing.T) {
 	tests := []struct {
 		name string // description of this test case
-		of   *internal.OpenFIGI
+		of   *ofigi.Client
 		want internal.Nature
 	}{
 		{
@@ -272,7 +273,7 @@ func (f RoundTripFunc) RoundTrip(req *http.Request) (*http.Response, error) {
 	return f(req)
 }
 
-func NewFigiClientSecurityTypeStub(t testing.TB, securityType string) *internal.OpenFIGI {
+func NewFigiClientSecurityTypeStub(t testing.TB, securityType string) *ofigi.Client {
 	t.Helper()
 
 	c := &http.Client{
@@ -287,10 +288,10 @@ func NewFigiClientSecurityTypeStub(t testing.TB, securityType string) *internal.
 		}),
 	}
 
-	return internal.NewOpenFIGI(c, "")
+	return ofigi.NewOpenFIGI(c, "")
 }
 
-func NewFigiClientErrorStub(t testing.TB, err error) *internal.OpenFIGI {
+func NewFigiClientErrorStub(t testing.TB, err error) *ofigi.Client {
 	t.Helper()
 
 	c := &http.Client{
@@ -300,5 +301,5 @@ func NewFigiClientErrorStub(t testing.TB, err error) *internal.OpenFIGI {
 		}),
 	}
 
-	return internal.NewOpenFIGI(c, "")
+	return ofigi.NewOpenFIGI(c, "")
 }
diff --git a/internal/trading212/serializer.go b/internal/trading212/serializer.go
new file mode 100644
index 0000000..68d4899
--- /dev/null
+++ b/internal/trading212/serializer.go
@@ -0,0 +1,88 @@
+package trading212
+
+import (
+	"context"
+	"encoding/json"
+	"fmt"
+	"time"
+
+	"github.com/nmoniz/any2anexoj/internal"
+	"github.com/nmoniz/any2anexoj/internal/ofigi"
+	"github.com/shopspring/decimal"
+)
+
+// recordState is the on-disk representation of a trading212.Record.
+// Nature is intentionally omitted because it is resolved lazily via the
+// OpenFIGI client on demand.
+type recordState struct {
+	Symbol    string          `json:"symbol"`
+	Timestamp time.Time       `json:"timestamp"`
+	Kind      internal.Kind   `json:"kind"`
+	Quantity  decimal.Decimal `json:"quantity"`
+	Price     decimal.Decimal `json:"price"`
+	Fees      decimal.Decimal `json:"fees"`
+	Taxes     decimal.Decimal `json:"taxes"`
+}
+
+// RecordSerializer encodes and decodes trading212.Record values for the
+// internal persistence layer. On decode it re-wires the lazy natureGetter to
+// the supplied OpenFIGI client so a restored Record resolves Nature() via a
+// fresh API call when needed.
+type RecordSerializer struct {
+	figi *ofigi.Client
+}
+
+// NewRecordSerializer returns a RecordSerializer that uses figi to resolve
+// Record.Nature() on load.
+func NewRecordSerializer(figi *ofigi.Client) *RecordSerializer {
+	return &RecordSerializer{figi: figi}
+}
+
+// MarshalRecord encodes the given internal.Record as JSON. It returns an
+// error if the record is not a trading212.Record (or a *trading212.Record).
+func (s *RecordSerializer) MarshalRecord(_ context.Context, r internal.Record) ([]byte, error) {
+	var rec Record
+	switch v := r.(type) {
+	case Record:
+		rec = v
+	case *Record:
+		if v == nil {
+			return nil, fmt.Errorf("trading212: cannot marshal nil *trading212.Record")
+		}
+		rec = *v
+	default:
+		return nil, fmt.Errorf("trading212: cannot marshal %T as trading212.Record", r)
+	}
+
+	state := recordState{
+		Symbol:    rec.symbol,
+		Timestamp: rec.timestamp,
+		Kind:      rec.kind,
+		Quantity:  rec.quantity,
+		Price:     rec.price,
+		Fees:      rec.fees,
+		Taxes:     rec.taxes,
+	}
+
+	return json.Marshal(state)
+}
+
+// UnmarshalRecord decodes a JSON-encoded trading212.Record and re-wires its
+// natureGetter to the serializer's OpenFIGI client.
+func (s *RecordSerializer) UnmarshalRecord(ctx context.Context, data []byte) (internal.Record, error) {
+	var state recordState
+	if err := json.Unmarshal(data, &state); err != nil {
+		return nil, fmt.Errorf("unmarshal trading212 record: %w", err)
+	}
+
+	return Record{
+		symbol:       state.Symbol,
+		timestamp:    state.Timestamp,
+		kind:         state.Kind,
+		quantity:     state.Quantity,
+		price:        state.Price,
+		fees:         state.Fees,
+		taxes:        state.Taxes,
+		natureGetter: figiNatureGetter(ctx, s.figi, state.Symbol),
+	}, nil
+}
diff --git a/internal/trading212/serializer_test.go b/internal/trading212/serializer_test.go
new file mode 100644
index 0000000..a6b0cf2
--- /dev/null
+++ b/internal/trading212/serializer_test.go
@@ -0,0 +1,151 @@
+package trading212
+
+import (
+	"bytes"
+	"io"
+	"net/http"
+	"testing"
+	"time"
+
+	"github.com/nmoniz/any2anexoj/internal"
+	"github.com/nmoniz/any2anexoj/internal/ofigi"
+	"github.com/shopspring/decimal"
+)
+
+func TestRecordSerializer_RoundTrip(t *testing.T) {
+	want := Record{
+		symbol:       "XX1234567890",
+		timestamp:    time.Date(2025, 7, 3, 10, 44, 29, 0, time.UTC),
+		kind:         internal.KindBuy,
+		quantity:     ShouldParseDecimal(t, "2.4387014200"),
+		price:        ShouldParseDecimal(t, "7.3690000000"),
+		fees:         ShouldParseDecimal(t, "0.02"),
+		taxes:        ShouldParseDecimal(t, "0.25"),
+		natureGetter: func() internal.Nature { return internal.NatureG01 },
+	}
+
+	s := NewRecordSerializer(NewFigiClientSecurityTypeStub(t, "Common Stock"))
+
+	data, err := s.MarshalRecord(t.Context(), want)
+	if err != nil {
+		t.Fatalf("MarshalRecord: %v", err)
+	}
+
+	got, err := s.UnmarshalRecord(t.Context(), data)
+	if err != nil {
+		t.Fatalf("UnmarshalRecord: %v", err)
+	}
+
+	if got.Symbol() != want.Symbol() {
+		t.Errorf("Symbol: want %q but got %q", want.Symbol(), got.Symbol())
+	}
+	if got.Kind() != want.Kind() {
+		t.Errorf("Kind: want %v but got %v", want.Kind(), got.Kind())
+	}
+	if !got.Price().Equal(want.Price()) {
+		t.Errorf("Price: want %v but got %v", want.Price(), got.Price())
+	}
+	if !got.Quantity().Equal(want.Quantity()) {
+		t.Errorf("Quantity: want %v but got %v", want.Quantity(), got.Quantity())
+	}
+	if !got.Fees().Equal(want.Fees()) {
+		t.Errorf("Fees: want %v but got %v", want.Fees(), got.Fees())
+	}
+	if !got.Taxes().Equal(want.Taxes()) {
+		t.Errorf("Taxes: want %v but got %v", want.Taxes(), got.Taxes())
+	}
+	if !got.Timestamp().Equal(want.Timestamp()) {
+		t.Errorf("Timestamp: want %v but got %v", want.Timestamp(), got.Timestamp())
+	}
+}
+
+func TestRecordSerializer_UnmarshalRecord_NatureTriggersOpenFIGI(t *testing.T) {
+	var calls int
+	client := &http.Client{
+		Timeout: time.Second,
+		Transport: RoundTripFunc(func(req *http.Request) (*http.Response, error) {
+			calls++
+			return &http.Response{
+				Status:     http.StatusText(http.StatusOK),
+				StatusCode: http.StatusOK,
+				Body:       io.NopCloser(bytes.NewBufferString(`[{"data":[{"securityType":"Common Stock"}]}]`)),
+				Request:    req,
+			}, nil
+		}),
+	}
+
+	s := NewRecordSerializer(ofigi.NewOpenFIGI(client, ""))
+
+	original := Record{
+		symbol:    "XX1234567890",
+		timestamp: time.Date(2025, 7, 3, 10, 44, 29, 0, time.UTC),
+		kind:      internal.KindBuy,
+		quantity:  ShouldParseDecimal(t, "2.4387014200"),
+		price:     ShouldParseDecimal(t, "7.3690000000"),
+		fees:      ShouldParseDecimal(t, "0.02"),
+		taxes:     ShouldParseDecimal(t, "0.25"),
+		// Pre-populated so MarshalRecord doesn't accidentally trigger an
+		// OpenFIGI call when encoding the original record.
+		natureGetter: func() internal.Nature { return internal.NatureG01 },
+	}
+
+	data, err := s.MarshalRecord(t.Context(), original)
+	if err != nil {
+		t.Fatalf("MarshalRecord: %v", err)
+	}
+
+	if calls != 0 {
+		t.Fatalf("OpenFIGI called during MarshalRecord: %d", calls)
+	}
+
+	got, err := s.UnmarshalRecord(t.Context(), data)
+	if err != nil {
+		t.Fatalf("UnmarshalRecord: %v", err)
+	}
+
+	// Nature must not have been resolved yet — natureGetter is lazy.
+	if calls != 0 {
+		t.Fatalf("OpenFIGI called before Nature(): %d", calls)
+	}
+
+	if nature := got.Nature(); nature != internal.NatureG01 {
+		t.Errorf("Nature: want %v but got %v", internal.NatureG01, nature)
+	}
+
+	if calls != 1 {
+		t.Errorf("OpenFIGI request count: want 1 but got %d", calls)
+	}
+
+	// Subsequent Nature() calls should not re-trigger the request (the
+	// underlying sync.OnceValue caches the result on the client too).
+	if nature := got.Nature(); nature != internal.NatureG01 {
+		t.Errorf("Nature (cached): want %v but got %v", internal.NatureG01, nature)
+	}
+	if calls != 1 {
+		t.Errorf("OpenFIGI request count after re-read: want 1 but got %d", calls)
+	}
+}
+
+func TestRecordSerializer_MarshalRecord_WrongType(t *testing.T) {
+	s := NewRecordSerializer(NewFigiClientSecurityTypeStub(t, "Common Stock"))
+
+	_, err := s.MarshalRecord(t.Context(), stubRecord{})
+	if err == nil {
+		t.Fatal("want error but got nil")
+	}
+}
+
+// stubRecord is a non-trading212 implementation of internal.Record used to
+// verify that MarshalRecord rejects unrelated record types.
+type stubRecord struct{}
+
+func (stubRecord) Symbol() string            { return "STUB" }
+func (stubRecord) Nature() internal.Nature   { return internal.NatureUnknown }
+func (stubRecord) BrokerCountry() int64      { return 0 }
+func (stubRecord) AssetCountry() int64       { return 0 }
+func (stubRecord) Kind() internal.Kind       { return internal.KindUnknown }
+func (stubRecord) Price() decimal.Decimal    { return decimal.Zero }
+func (stubRecord) Quantity() decimal.Decimal { return decimal.Zero }
+func (stubRecord) Timestamp() time.Time      { return time.Time{} }
+func (stubRecord) Fees() decimal.Decimal     { return decimal.Zero }
+func (stubRecord) Taxes() decimal.Decimal    { return decimal.Zero }