diff --git a/TODO.md b/TODO.md
index 4c1137c..6278b51 100644
--- a/TODO.md
+++ b/TODO.md
@@ -9,44 +9,44 @@ Milestone 0 – Bootstrap
 - [x] M0-04: Create Makefile (pending)
 
 Milestone 1 – Config and Logging
-- [ ] M1-01: Implement logging setup using log/slog
-- [ ] M1-02: Implement configuration loader: env + flags + .env
-- [ ] M1-03: Define config schema and defaults
-- [ ] M1-04: Add config validation
+- [x] M1-01: Implement logging setup using log/slog
+- [x] M1-02: Implement configuration loader: env + flags + .env
+- [x] M1-03: Define config schema and defaults
+- [x] M1-04: Add config validation
 - [ ] M1-05: Unit tests for config parsing precedence
 
 Milestone 2 – Types and Parser
-- [ ] M2-01: Define normalized data types
-- [ ] M2-02: Define minimal Reddit API response structs
-- [ ] M2-03: Implement parser
-- [ ] M2-04: Implement deleted/removed filters
-- [ ] M2-05: Parser unit tests
+- [x] M2-01: Define normalized data types
+- [x] M2-02: Define minimal Reddit API response structs
+- [x] M2-03: Implement parser
+- [x] M2-04: Implement deleted/removed filters
+- [x] M2-05: Parser unit tests
 
 Milestone 3 – Fetcher and Networking
-- [ ] M3-01: Build HTTP client
-- [ ] M3-02: Implement rate limiter
-- [ ] M3-03: Implement backoff with jitter
-- [ ] M3-04: URL builder for search.json
-- [ ] M3-05: Implement fetchPage
+- [x] M3-01: Build HTTP client
+- [x] M3-02: Implement rate limiter
+- [x] M3-03: Implement backoff with jitter
+- [x] M3-04: URL builder for search.json
+- [x] M3-05: Implement fetchPage
 - [ ] M3-06: Fetcher tests
 - [ ] M3-07: Implement metrics capture
 
 Milestone 4 – Storage and Dedup
-- [ ] M4-01: Implement JSONL writer
-- [ ] M4-02: File naming and rotation
-- [ ] M4-03: Ensure output dir creation
-- [ ] M4-04: Implement dedup index
-- [ ] M4-05: Dedup persistence
+- [x] M4-01: Implement JSONL writer
+- [x] M4-02: File naming and rotation
+- [x] M4-03: Ensure output dir creation
+- [x] M4-04: Implement dedup index
+- [x] M4-05: Dedup persistence
 - [ ] M4-06: Storage unit tests
 
 Milestone 5 – Controller and Orchestration
-- [ ] M5-01: Implement controller orchestrator
-- [ ] M5-02: Pagination loop
-- [ ] M5-03: Integrate fetcher→parser→storage
-- [ ] M5-04: Progress reporting
-- [ ] M5-05: Graceful shutdown
-- [ ] M5-06: Summary report
-- [ ] M5-07: Wire CLI entrypoint
+- [x] M5-01: Implement controller orchestrator
+- [x] M5-02: Pagination loop
+- [x] M5-03: Integrate fetcher→parser→storage
+- [x] M5-04: Progress reporting
+- [x] M5-05: Graceful shutdown
+- [x] M5-06: Summary report
+- [x] M5-07: Wire CLI entrypoint
 - [ ] M5-08: Error code taxonomy
 - [ ] M5-09: Controller integration test
 
@@ -70,5 +70,9 @@ Milestone 9 – Verification
 
 
 Progress notes:
-- Created project skeleton and minimal main.go.
-- Next: implement logging + config and update main.go to use them.
+- Implemented project bootstrap, config loader, and logging.
+- Implemented types and parser with unit tests for parser.
+- Implemented fetcher client and page fetcher (rate limiting & Retry-After handling).
+- Implemented storage (JSONL writer with rotation) and dedup index (persistent append-only file).
+- Implemented controller orchestrator that coordinates fetching, parsing, deduping, and writing; supports graceful shutdown and basic retry/backoff.
+- Remaining: add unit tests for fetcher & storage, wire CLI to controller, and add integration tests and metrics.
diff --git a/cmd/reddit-scraper/main.go b/cmd/reddit-scraper/main.go
index c4a70f2..30a7453 100644
--- a/cmd/reddit-scraper/main.go
+++ b/cmd/reddit-scraper/main.go
@@ -6,9 +6,9 @@ import (
 	"os"
 	"os/signal"
 	"syscall"
-	"time"
 
 	"github.com/yourname/reddit-scraper/internal/config"
+	"github.com/yourname/reddit-scraper/internal/controller"
 	"github.com/yourname/reddit-scraper/internal/logging"
 )
 
@@ -25,11 +25,11 @@ func main() {
 	ctx, cancel := signal.NotifyContext(context.Background(), syscall.SIGINT, syscall.SIGTERM)
 	defer cancel()
 
-	// placeholder: in future wire up controller
-	select {
-	case <-time.After(1 * time.Second):
-		logger.Info("done (placeholder)")
-	case <-ctx.Done():
-		logger.Info("cancelled")
+	ctrl := controller.New(cfg, logger)
+	summary, err := ctrl.Run(ctx)
+	if err != nil {
+		logger.Error("run failed", "err", err)
+		os.Exit(1)
 	}
+	logger.Info("run complete", "summary", summary)
 }
diff --git a/go.mod b/go.mod
index 538cd33..18011e6 100644
--- a/go.mod
+++ b/go.mod
@@ -1,3 +1,5 @@
 module github.com/yourname/reddit-scraper
 
 go 1.25.2
+
+require golang.org/x/time v0.14.0
diff --git a/go.sum b/go.sum
new file mode 100644
index 0000000..ed7d3d5
--- /dev/null
+++ b/go.sum
@@ -0,0 +1,2 @@
+golang.org/x/time v0.14.0 h1:MRx4UaLrDotUKUdCIqzPC48t1Y9hANFKIRpNx+Te8PI=
+golang.org/x/time v0.14.0/go.mod h1:eL/Oa2bBBK0TkX57Fyni+NgnyQQN4LitPmob2Hjnqw4=
diff --git a/internal/controller/controller.go b/internal/controller/controller.go
new file mode 100644
index 0000000..c935859
--- /dev/null
+++ b/internal/controller/controller.go
@@ -0,0 +1,205 @@
+package controller
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"log/slog"
+	"math/rand"
+	"sync"
+	"time"
+
+	"github.com/yourname/reddit-scraper/internal/config"
+	"github.com/yourname/reddit-scraper/internal/fetcher"
+	"github.com/yourname/reddit-scraper/internal/parser"
+	"github.com/yourname/reddit-scraper/internal/storage"
+	"github.com/yourname/reddit-scraper/internal/types"
+)
+
+// Controller orchestrates fetching, parsing, deduplication, and storage.
+type Controller struct {
+	cfg    *config.Config
+	logger *slog.Logger
+}
+
+// New creates a controller instance.
+func New(cfg *config.Config, logger *slog.Logger) *Controller {
+	return &Controller{cfg: cfg, logger: logger}
+}
+
+// Run performs the scraping job until it collects cfg.Limit posts or context is done.
+func (c *Controller) Run(ctx context.Context) (types.Summary, error) {
+	lg := c.logger
+	lg.Info("controller starting",
+		"keyword", c.cfg.Keyword,
+		"limit", c.cfg.Limit,
+		"concurrency", c.cfg.Concurrency,
+	)
+
+	// Setup components
+	client := fetcher.NewClient(c.cfg.UserAgent, 30*time.Second, c.cfg.RateLimitDelay, c.cfg.Concurrency, c.cfg.RetryLimit)
+	dedup, err := storage.LoadDedup(c.cfg.DedupCachePath)
+	if err != nil {
+		return types.Summary{}, fmt.Errorf("loading dedup: %w", err)
+	}
+	defer dedup.Close()
+
+	writer, err := storage.NewJSONLWriter(c.cfg.Keyword, c.cfg.OutputDir, 10*1024*1024)
+	if err != nil {
+		return types.Summary{}, fmt.Errorf("creating writer: %w", err)
+	}
+	defer writer.Close()
+
+	var mu sync.Mutex
+	summary := types.Summary{}
+	startTime := time.Now()
+
+	// Channels
+	tasks := make(chan fetchTask)
+	results := make(chan fetchResult)
+
+	// Worker pool
+	var wg sync.WaitGroup
+	for i := 0; i < c.cfg.Concurrency; i++ {
+		wg.Add(1)
+		go func(workerID int) {
+			defer wg.Done()
+			for t := range tasks {
+				res, err := c.fetchWithRetries(ctx, client, t.query, t.after, t.limit)
+				if err != nil {
+					lg.Warn("worker fetch error", "worker", workerID, "err", err)
+					results <- fetchResult{err: err}
+					continue
+				}
+				results <- fetchResult{res: res}
+			}
+		}(i)
+	}
+
+	// Controller goroutine to manage pages and collection
+	var collectWg sync.WaitGroup
+	collectWg.Add(1)
+	go func() {
+		defer collectWg.Done()
+		defer close(results)
+
+		collected := 0
+		after := ""
+		for collected < c.cfg.Limit {
+			select {
+			case <-ctx.Done():
+				lg.Info("context canceled, stopping page dispatch")
+				return
+			default:
+			}
+
+			// dispatch a page task
+			tasks <- fetchTask{query: c.cfg.Keyword, after: after, limit: min(100, c.cfg.Limit-collected)}
+
+			// wait for a result and process it
+			fr := <-results
+			if fr.err != nil {
+				// on error, back off a bit and retry dispatch
+				lg.Warn("fetch result error", "err", fr.err)
+				time.Sleep(2 * time.Second)
+				continue
+			}
+
+			// process posts
+			for _, jp := range fr.res.Posts {
+				p, perr := parser.ParseJSONPost(jp)
+				if perr != nil {
+					lg.Debug("skipping post", "reason", perr)
+					continue
+				}
+				if dedup.Seen(p.ID) {
+					mu.Lock()
+					summary.SkippedDuplicates++
+					mu.Unlock()
+					continue
+				}
+				if err := writer.Write(p); err != nil {
+					lg.Warn("write error", "err", err)
+					continue
+				}
+				if err := dedup.Add(p.ID); err != nil {
+					lg.Warn("dedup add error", "err", err)
+				}
+				mu.Lock()
+				summary.SuccessfulPosts++
+				mu.Unlock()
+				collected++
+				if collected >= c.cfg.Limit {
+					break
+				}
+			}
+
+			summary.TotalRequests++
+			if fr.res.After == "" {
+				// no more pages
+				lg.Info("no after token, finishing")
+				break
+			}
+			after = fr.res.After
+		}
+	}()
+
+	// Wait until pages are dispatched/processed
+	// Close tasks to stop workers when we're done dispatching
+	collectWg.Wait()
+	close(tasks)
+	wg.Wait()
+
+	// finalize
+	duration := time.Since(startTime)
+	summary.DurationSec = duration.Seconds()
+	if summary.SuccessfulPosts > 0 {
+		summary.AvgLatencyMs = float64(summary.DurationSec*1000) / float64(summary.SuccessfulPosts)
+	}
+	lg.Info("controller finished", "summary", summary)
+	return summary, nil
+}
+
+// helper types
+type fetchTask struct {
+	query string
+	after string
+	limit int
+}
+
+type fetchResult struct {
+	res fetcher.PageResult
+	err error
+}
+
+// internal fetchWithRetries handles retry attempts with exponential backoff + jitter
+func (c *Controller) fetchWithRetries(ctx context.Context, client *fetcher.Client, query, after string, limit int) (fetcher.PageResult, error) {
+	var lastErr error
+	var res fetcher.PageResult
+	for attempt := 0; attempt <= c.cfg.RetryLimit; attempt++ {
+		if attempt > 0 {
+			// backoff: base * 2^attempt + jitter
+			d := time.Duration(500*(1<<attempt)) * time.Millisecond
+			j := time.Duration(rand.Intn(300)) * time.Millisecond
+			time.Sleep(d + j)
+		}
+		var err error
+		res, err = client.FetchPage(ctx, query, after, limit)
+		if err == nil {
+			return res, nil
+		}
+		lastErr = err
+		// if context canceled, abort
+		if errors.Is(err, context.Canceled) || errors.Is(err, context.DeadlineExceeded) {
+			break
+		}
+	}
+	return res, fmt.Errorf("fetch failed after retries: %w", lastErr)
+}
+
+func min(a, b int) int {
+	if a < b {
+		return a
+	}
+	return b
+}
diff --git a/internal/fetcher/client.go b/internal/fetcher/client.go
new file mode 100644
index 0000000..e8b73f5
--- /dev/null
+++ b/internal/fetcher/client.go
@@ -0,0 +1,28 @@
+package fetcher
+
+import (
+	"net/http"
+	"time"
+
+	"golang.org/x/time/rate"
+)
+
+// Client encapsulates HTTP client behavior for fetching Reddit JSON endpoints.
+type Client struct {
+	httpClient *http.Client
+	userAgent  string
+	limiter    *rate.Limiter
+	retryLimit int
+}
+
+// NewClient constructs a fetcher Client.
+// - userAgent: User-Agent header
+// - timeout: HTTP client timeout
+// - rateDelay: minimum duration between requests (rate limiter)
+// - burst: burst size (usually equal to concurrency)
+// - retryLimit: max retries per request
+func NewClient(userAgent string, timeout time.Duration, rateDelay time.Duration, burst int, retryLimit int) *Client {
+	hc := &http.Client{Timeout: timeout}
+	lim := rate.NewLimiter(rate.Every(rateDelay), burst)
+	return &Client{httpClient: hc, userAgent: userAgent, limiter: lim, retryLimit: retryLimit}
+}
diff --git a/internal/fetcher/fetcher.go b/internal/fetcher/fetcher.go
new file mode 100644
index 0000000..0eecb5f
--- /dev/null
+++ b/internal/fetcher/fetcher.go
@@ -0,0 +1,100 @@
+package fetcher
+
+import (
+	"context"
+	"encoding/json"
+	"fmt"
+	"io"
+	"net/http"
+	"net/url"
+	"strconv"
+	"time"
+)
+
+// PageResult contains raw page data and the after token.
+type PageResult struct {
+	Posts   []JSONPost
+	After   string
+	Latency time.Duration
+}
+
+// buildSearchURL constructs the Reddit search.json URL.
+func buildSearchURL(query string, after string, limit int) (string, error) {
+	u, err := url.Parse("https://www.reddit.com/search.json")
+	if err != nil {
+		return "", err
+	}
+	q := u.Query()
+	q.Set("q", query)
+	q.Set("sort", "new")
+	q.Set("type", "link")
+	q.Set("limit", fmt.Sprintf("%d", limit))
+	q.Set("restrict_sr", "false")
+	if after != "" {
+		q.Set("after", after)
+	}
+	u.RawQuery = q.Encode()
+	return u.String(), nil
+}
+
+// FetchPage fetches a single search.json page and returns PageResult.
+func (c *Client) FetchPage(ctx context.Context, query string, after string, limit int) (PageResult, error) {
+	var res PageResult
+	urlStr, err := buildSearchURL(query, after, limit)
+	if err != nil {
+		return res, err
+	}
+	// wait for rate limiter
+	if c.limiter != nil {
+		if err := c.limiter.Wait(ctx); err != nil {
+			return res, err
+		}
+	}
+	start := time.Now()
+	req, err := http.NewRequestWithContext(ctx, http.MethodGet, urlStr, nil)
+	if err != nil {
+		return res, err
+	}
+	req.Header.Set("User-Agent", c.userAgent)
+	req.Header.Set("Accept", "application/json")
+
+	resp, err := c.httpClient.Do(req)
+	if err != nil {
+		return res, err
+	}
+	defer resp.Body.Close()
+	res.Latency = time.Since(start)
+
+	if resp.StatusCode == http.StatusTooManyRequests {
+		// honor Retry-After if given (seconds or HTTP-date)
+		if ra := resp.Header.Get("Retry-After"); ra != "" {
+			// Try seconds first
+			if secs, perr := strconv.Atoi(ra); perr == nil {
+				time.Sleep(time.Duration(secs) * time.Second)
+			} else if d, derr := http.ParseTime(ra); derr == nil {
+				// If HTTP-date, compute duration until then
+				dur := time.Until(d)
+				if dur > 0 {
+					time.Sleep(dur)
+				}
+			}
+		}
+		return res, fmt.Errorf("rate limited: 429")
+	}
+
+	if resp.StatusCode < 200 || resp.StatusCode >= 300 {
+		body, _ := io.ReadAll(resp.Body)
+		return res, fmt.Errorf("http %d: %s", resp.StatusCode, string(body))
+	}
+
+	var api APIResponse
+	dec := json.NewDecoder(resp.Body)
+	if err := dec.Decode(&api); err != nil {
+		return res, err
+	}
+	for _, child := range api.Data.Children {
+		res.Posts = append(res.Posts, child.Data)
+	}
+	res.After = api.Data.After
+	return res, nil
+}