diff --git a/.env.example b/.env.example
index e514954..e457372 100644
--- a/.env.example
+++ b/.env.example
@@ -60,6 +60,10 @@ BACKEND_STORAGE_DRIVER=local
 #S3_SECRET_ACCESS_KEY=
 #S3_PREFIX=
 #S3_PATH_STYLE=true
+# Client-facing S3 endpoint for presigned URLs — set when S3_ENDPOINT is an
+# internal address (e.g. http://minio:9000 inside compose) that browsers
+# can't reach. Presigned URLs are valid only at the host they were minted for.
+#S3_PUBLIC_ENDPOINT=https://objects.example.com
 
 # Mail defaults — each is overridable in-app (Settings → Instance). In-app
 # values win over these env vars; deleting the in-app value reverts here.
diff --git a/CHANGELOG.md b/CHANGELOG.md
index 5a0c679..9e2f9e0 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -25,6 +25,7 @@ All notable changes to Primora. Format follows [Keep a Changelog](https://keepac
 - **Email templates + send log** (`core.email_log`, migration 00014) — the mailer renders registered templates (currently `invitation`) and every send — successful or failed — is recorded with template, recipient, subject, status, and error text. `GET /projects/:id/emails` lists recent sends; the Members page shows an "Email log" card under pending invitations.
 - **S3-compatible object storage backend** — `BACKEND_STORAGE_DRIVER=s3` swaps the local disk store for any S3-compatible API (AWS, MinIO, Garage, R2) via a stdlib-only SigV4 implementation — no AWS SDK dependency. `S3_ENDPOINT`/`S3_REGION`/`S3_BUCKET`/credentials configure it; `S3_PATH_STYLE` (default on) covers MinIO/Garage, off for AWS virtual-hosted. The configured bucket is created on startup if missing; objects stream with computed SHA-256, `storage_path` records `s3://bucket/key`. Verified live end-to-end (bucket → put → get → copy → list → delete).
 - **Functions** (`core.functions` + `core.function_runs`, migration 00015) — project-scoped JS/TS executed by a runtime binary on the backend host (`bun` or `deno`, per function). The JSON payload arrives on stdin and as `PRIMORA_PAYLOAD`; stdout/stderr are captured per run (capped at 64 KiB) with status, exit code and duration — `FUNCTIONS_RUNTIME`/`FUNCTIONS_TIMEOUT_SECONDS`/`FUNCTIONS_MAX_OUTPUT_BYTES` configure the runner. API: CRUD under `/projects/:id/functions`, `POST …/invoke` (502 + recorded run on failure), `GET …/runs`. Dashboard gains a Functions page: code editor, JSON payload invoke, live result, run history. Code executes with backend privileges — the documented self-hosted trust model.
+- **Presigned object URLs** — `POST /buckets/:bucketID/object-presigns` mints SigV4 query-signed `GET`/`PUT` URLs (60 s–1 h TTL) so clients transfer large objects directly against S3 without proxying through the backend. Read role for downloads (object must exist — no key probing), write role for uploads. `S3_PUBLIC_ENDPOINT` rewrites the client-facing host for internal `S3_ENDPOINT`s; signatures bind the host so URLs are valid only where they were minted. The local driver returns a clear error — a presigned URL needs a real object API.
 - **Function triggers** (migration 00016) — three new ways to run a function, all through the same executor and run log. Scheduled jobs accept `function_id` instead of `url` (run status mirrors the exit code); inbound hooks gain `mode: "function"` — the received body becomes the function's stdin payload, acked immediately with the run recorded async; and `event_pattern` on a function (`document.*`, `*`, or an exact type) fires it detached whenever a matching domain event publishes — `{event, project_id, occurred_at, data}` as payload. Runs record trigger source: `manual`/`schedule`/`hook`/`event`. Dashboard: function event-trigger field, job target picker (URL or function), and inbound-hook function mode.
 
 ## [0.7.1] - 2026-09-23
diff --git a/DEPLOYMENT_GUIDE.md b/DEPLOYMENT_GUIDE.md
index 72fe1d5..854efda 100644
--- a/DEPLOYMENT_GUIDE.md
+++ b/DEPLOYMENT_GUIDE.md
@@ -46,6 +46,7 @@ docker compose -f docker-compose.yml -f docker-compose.dev.yml up -d
 | `S3_ENDPOINT` / `S3_REGION` / `S3_BUCKET` | S3 API endpoint (empty endpoint → AWS `s3.<region>.amazonaws.com`), region, bucket | with `s3` |
 | `S3_ACCESS_KEY_ID` / `S3_SECRET_ACCESS_KEY` | S3 credentials | with `s3` |
 | `S3_PREFIX` / `S3_PATH_STYLE` | optional key prefix; path-style URLs (default `true`, needed by MinIO/Garage — set `false` for AWS virtual-hosted) | no |
+| `S3_PUBLIC_ENDPOINT` | client-facing S3 endpoint used for presigned URLs when `S3_ENDPOINT` is internal-only (e.g. `http://minio:9000`); signatures bind the public host | no |
 | `FUNCTIONS_RUNTIME` / `FUNCTIONS_TIMEOUT_SECONDS` / `FUNCTIONS_MAX_OUTPUT_BYTES` | Functions: runtime binary (`auto` resolves `bun`/`deno` from the backend's PATH — the backend image must ship one, or set this to its path), per-run timeout (default 30 s), captured-output cap (default 64 KiB) | no |
 | `AUTH_ADMIN_EMAILS` | comma-separated emails promoted to auth admin on boot | no |
 | `USER_RATE_LIMIT_PER_MINUTE` / `API_KEY_RATE_LIMIT_PER_MINUTE` | per-identity API rate limits (defaults 240 / 600) | no |
diff --git a/QUICK_START.md b/QUICK_START.md
index 4095e23..7a593e4 100644
--- a/QUICK_START.md
+++ b/QUICK_START.md
@@ -67,6 +67,7 @@ The important ones:
 | `USER_RATE_LIMIT_PER_MINUTE` / `API_KEY_RATE_LIMIT_PER_MINUTE` | Throttling defaults — overridable in-app |
 | `BACKEND_STORAGE_DRIVER` | `local` (default, `BACKEND_STORAGE_ROOT`) or `s3` — S3-compatible object storage |
 | `S3_ENDPOINT` / `S3_BUCKET` / `S3_ACCESS_KEY_ID` / `S3_SECRET_ACCESS_KEY` | S3 backend config (with `S3_REGION`, `S3_PREFIX`, `S3_PATH_STYLE`) |
+| `S3_PUBLIC_ENDPOINT` | Client-facing S3 host for presigned URLs when `S3_ENDPOINT` is internal-only |
 | `FUNCTIONS_RUNTIME` / `FUNCTIONS_TIMEOUT_SECONDS` | JS runtime for Functions — `auto` (default, resolves `bun`/`deno` from PATH) or a binary path; 30 s default timeout |
 | `VITE_DEMO_MODE` | Enable the client-side demo workspace |
 
diff --git a/README.md b/README.md
index 52a36e2..60c21e1 100644
--- a/README.md
+++ b/README.md
@@ -48,7 +48,7 @@ Supabase, with no hosted tier - your data stays on your hardware.
 
 - **Organizations & projects** - workspaces with scoped org and project roles.
 - **Auth** - email/password plus optional GitHub, Google, Discord, and Microsoft OAuth. JWTs verified by the API against JWKS.
-- **Storage** - S3-style buckets on local disk or any S3-compatible backend (AWS, MinIO, Garage, R2), public or private.
+- **Storage** - S3-style buckets on local disk or any S3-compatible backend (AWS, MinIO, Garage, R2), public or private. With `s3` the API mints presigned upload/download URLs so large objects skip the backend.
 - **Collections** - schema-flexible JSON documents in Postgres JSONB, with filter/order queries.
 - **Functions** - project-scoped JS/TS executed by bun/deno on the host, with per-run logs. Trigger them four ways: manual invoke, cron schedules (`function_id` on a job), inbound hooks (`mode: "function"`), or domain events (`event_pattern` like `document.*`).
 - **Vault** - AES-256-GCM project secrets plus an Argon2id/XChaCha20 local vault in the CLI and desktop app.
diff --git a/ROADMAP.md b/ROADMAP.md
index 58f0dfd..80c8c5a 100644
--- a/ROADMAP.md
+++ b/ROADMAP.md
@@ -365,10 +365,12 @@ Ordered loosely by leverage. None committed; each gets scoped when picked.
   Runs record trigger source (`manual`/`schedule`/`hook`/`event`).
   Remaining candidate: isolated runtimes (sidecar/Firecracker) for
   untrusted code — functions still execute with backend host privileges.
-- **Phase 10 — Storage backends** — ✅ S3-compatible object storage shipped:
-  `BACKEND_STORAGE_DRIVER=s3` + `S3_*` env vars, stdlib SigV4, verified
-  against a real S3 server. Presigned-URL uploads for large files remain a
-  candidate.
+- **Phase 10 — Storage backends** — ✅ shipped: `BACKEND_STORAGE_DRIVER=s3`
+  + `S3_*` env vars, stdlib SigV4, verified against a real S3 server.
+  Presigned upload/download URLs shipped: `POST
+  /buckets/:id/object-presigns` mints SigV4 query-signed GET/PUT URLs
+  (`S3_PUBLIC_ENDPOINT` rewrites the client-facing host); local driver
+  returns a clear error — a presigned URL needs a real object API behind it.
 - **HA mode** — ✅ shipped: PostgreSQL advisory-lock leadership for the
   scheduler and alert evaluator; failover verified with two replicas.
 - **Email surface** — ✅ shipped: templated sends + `core.email_log` +
diff --git a/apps/backend/internal/app/app.go b/apps/backend/internal/app/app.go
index ebf17c5..2d6661b 100644
--- a/apps/backend/internal/app/app.go
+++ b/apps/backend/internal/app/app.go
@@ -89,6 +89,7 @@ func Bootstrap(ctx context.Context) (*App, error) {
 			Bucket:          cfg.S3Bucket,
 			AccessKeyID:     cfg.S3AccessKeyID,
 			SecretAccessKey: cfg.S3SecretAccessKey,
+			PublicEndpoint:  cfg.S3PublicEndpoint,
 			Prefix:          cfg.S3Prefix,
 			PathStyle:       cfg.S3PathStyle,
 		})
diff --git a/apps/backend/internal/config/config.go b/apps/backend/internal/config/config.go
index da8d98e..f707540 100644
--- a/apps/backend/internal/config/config.go
+++ b/apps/backend/internal/config/config.go
@@ -44,6 +44,7 @@ type Config struct {
 	S3Bucket         string
 	S3AccessKeyID    string
 	S3SecretAccessKey string
+	S3PublicEndpoint string // presigned-URL host when it differs from Endpoint
 	S3Prefix         string
 	S3PathStyle      bool
 
@@ -86,6 +87,7 @@ func Load() (Config, error) {
 		S3Bucket:              os.Getenv("S3_BUCKET"),
 		S3AccessKeyID:         os.Getenv("S3_ACCESS_KEY_ID"),
 		S3SecretAccessKey:     os.Getenv("S3_SECRET_ACCESS_KEY"),
+		S3PublicEndpoint:      os.Getenv("S3_PUBLIC_ENDPOINT"),
 		S3Prefix:              os.Getenv("S3_PREFIX"),
 		FunctionsRuntime:      getenv("FUNCTIONS_RUNTIME", "auto"),
 		FunctionsMaxBytes:     65536,
diff --git a/apps/backend/internal/handlers/http.go b/apps/backend/internal/handlers/http.go
index 4f0378e..cda314c 100644
--- a/apps/backend/internal/handlers/http.go
+++ b/apps/backend/internal/handlers/http.go
@@ -142,6 +142,7 @@ func (h *HTTPHandler) Register(router *gin.Engine) {
 	api.GET("/buckets/:bucketID/objects", h.listObjects)
 	api.POST("/buckets/:bucketID/objects", h.uploadObject)
 	api.POST("/buckets/:bucketID/object-copies", h.copyObject)
+	api.POST("/buckets/:bucketID/object-presigns", h.presignObject)
 	api.GET("/buckets/:bucketID/objects/*objectKey", h.downloadObject)
 	api.PATCH("/buckets/:bucketID/objects/*objectKey", h.updateObject)
 	api.DELETE("/buckets/:bucketID/objects/*objectKey", h.deleteObject)
@@ -891,6 +892,39 @@ func (h *HTTPHandler) updateObject(c *gin.Context) {
 	c.Status(http.StatusNoContent)
 }
 
+type presignObjectRequest struct {
+	Key        string `json:"key" validate:"required"`
+	Op         string `json:"op" validate:"omitempty,oneof=download upload"`
+	TTLSeconds int    `json:"ttl_seconds" validate:"omitempty,min=60,max=3600"`
+}
+
+// presignObject returns a short-lived URL clients call against storage
+// directly — keeps large transfers off the backend. S3 driver only.
+func (h *HTTPHandler) presignObject(c *gin.Context) {
+	actor, ok := middleware.RequireActor(c)
+	if !ok {
+		return
+	}
+	bucketID, ok := parseUUIDParam(c, "bucketID")
+	if !ok {
+		return
+	}
+	var body presignObjectRequest
+	if !h.bindAndValidate(c, &body) {
+		return
+	}
+	out, err := h.Platform.PresignObject(c.Request.Context(), actor, bucketID, strings.TrimSpace(body.Key), body.Op, body.TTLSeconds)
+	if err != nil {
+		if errors.Is(err, pgx.ErrNoRows) {
+			apperrors.Abort(c, http.StatusNotFound, "not_found", "bucket or object not found")
+			return
+		}
+		h.handleError(c, err)
+		return
+	}
+	c.JSON(http.StatusOK, out)
+}
+
 func (h *HTTPHandler) deleteObject(c *gin.Context) {
 	actor, ok := middleware.RequireActor(c)
 	if !ok {
diff --git a/apps/backend/internal/services/platform_service.go b/apps/backend/internal/services/platform_service.go
index 03a7101..e133622 100644
--- a/apps/backend/internal/services/platform_service.go
+++ b/apps/backend/internal/services/platform_service.go
@@ -10,6 +10,7 @@ import (
 	"fmt"
 	"io"
 	"log/slog"
+	"net/http"
 	"net/url"
 	"path/filepath"
 	"strings"
@@ -1418,6 +1419,48 @@ func (s *PlatformService) GetObject(ctx context.Context, actor *models.Actor, bu
 	return object, file, nil
 }
 
+// PresignObject mints a short-lived direct-to-storage URL for a single
+// object. Requires the s3 storage driver — the local store has no external
+// URL surface to sign against.
+func (s *PlatformService) PresignObject(ctx context.Context, actor *models.Actor, bucketID uuid.UUID, objectKey, op string, ttlSeconds int) (*storage.PresignedURL, error) {
+	bucket, err := s.repo.Queries().GetBucketByID(ctx, bucketID)
+	if err != nil {
+		return nil, err
+	}
+	method := ""
+	switch op {
+	case "download", "":
+		method = http.MethodGet
+		if err := s.requireBucketRead(ctx, actor, bucket); err != nil {
+			return nil, err
+		}
+		if !objectExists(ctx, s, bucketID, objectKey) {
+			return nil, pgx.ErrNoRows
+		}
+	case "upload":
+		method = http.MethodPut
+		if err := s.requireBucketWrite(ctx, actor, bucket); err != nil {
+			return nil, err
+		}
+	default:
+		return nil, fmt.Errorf("invalid op %q — download or upload", op)
+	}
+	p, ok := s.store.(storage.Presigner)
+	if !ok {
+		return nil, fmt.Errorf("presigned URLs require BACKEND_STORAGE_DRIVER=s3")
+	}
+	ttl := time.Duration(ttlSeconds) * time.Second
+	return p.Presign(ctx, bucketID.String(), objectKey, method, ttl)
+}
+
+func objectExists(ctx context.Context, s *PlatformService, bucketID uuid.UUID, key string) bool {
+	_, err := s.repo.Queries().GetBucketObjectByKey(ctx, db.GetBucketObjectByKeyParams{
+		BucketID:  bucketID,
+		ObjectKey: key,
+	})
+	return err == nil
+}
+
 func (s *PlatformService) UpdateObject(ctx context.Context, actor *models.Actor, bucketID uuid.UUID, objectKey string, input UpdateObjectInput, requestID string) (db.CoreBucketObject, error) {
 	sourceBucket, err := s.repo.Queries().GetBucketByID(ctx, bucketID)
 	if err != nil {
diff --git a/apps/backend/internal/storage/s3.go b/apps/backend/internal/storage/s3.go
index 7081b17..dd301fc 100644
--- a/apps/backend/internal/storage/s3.go
+++ b/apps/backend/internal/storage/s3.go
@@ -28,7 +28,11 @@ type S3Config struct {
 	SecretAccessKey string
 	Prefix          string // optional key prefix, e.g. "primora/"
 	PathStyle       bool   // bucket/key path style (MinIO, Garage) vs virtual-hosted
-	HTTPClient      *http.Client
+	// PublicEndpoint rewrites presigned-URL hosts for clients that can't
+	// reach Endpoint (e.g. minio:9000 inside compose). Signature binds the
+	// public host — the URL is only valid there.
+	PublicEndpoint string
+	HTTPClient     *http.Client
 }
 
 // S3Store implements Store against an S3-compatible API using stdlib-only
@@ -271,6 +275,88 @@ func (s *S3Store) DeleteBucket(bucketID string) error {
 	}
 }
 
+// Presign mints a SigV4 query-signed URL for a single GET/PUT on the
+// object — clients talk to S3 directly instead of proxying bytes through
+// the backend. TTL is capped at one hour.
+func (s *S3Store) Presign(ctx context.Context, bucketID, objectKey, method string, ttl time.Duration) (*PresignedURL, error) {
+	if method != http.MethodGet && method != http.MethodPut {
+		return nil, fmt.Errorf("s3 presign: unsupported method %q", method)
+	}
+	key, err := s.objectKey(bucketID, objectKey)
+	if err != nil {
+		return nil, err
+	}
+	if ttl <= 0 {
+		ttl = 15 * time.Minute
+	}
+	if ttl > time.Hour {
+		ttl = time.Hour
+	}
+
+	now := s.now().UTC()
+	amzDate := now.Format("20060102T150405Z")
+	dateStamp := now.Format("20060102")
+	scope := fmt.Sprintf("%s/%s/s3/aws4_request", dateStamp, s.cfg.Region)
+
+	// Build the unsigned URL — same path/vhost logic as signedRequest, but
+	// on the client-facing endpoint when one is configured.
+	var base *url.URL
+	endpoint := strings.TrimSuffix(s.cfg.PublicEndpoint, "/")
+	if endpoint == "" {
+		endpoint = strings.TrimSuffix(s.cfg.Endpoint, "/")
+	}
+	if s.cfg.PathStyle {
+		u, err := url.Parse(endpoint + "/" + s.cfg.Bucket + "/" + escapeKey(key))
+		if err != nil {
+			return nil, fmt.Errorf("s3 presign url: %w", err)
+		}
+		base = u
+	} else {
+		u, err := url.Parse(endpoint)
+		if err != nil {
+			return nil, fmt.Errorf("s3 presign url: %w", err)
+		}
+		u.Host = s.cfg.Bucket + "." + u.Host
+		u.Path = "/" + escapeKey(key)
+		base = u
+	}
+
+	q := base.Query()
+	q.Set("X-Amz-Algorithm", "AWS4-HMAC-SHA256")
+	q.Set("X-Amz-Credential", s.cfg.AccessKeyID+"/"+scope)
+	q.Set("X-Amz-Date", amzDate)
+	q.Set("X-Amz-Expires", fmt.Sprintf("%d", int64(ttl.Seconds())))
+	q.Set("X-Amz-SignedHeaders", "host")
+
+	canonicalURI := base.EscapedPath()
+	if canonicalURI == "" {
+		canonicalURI = "/"
+	}
+	canonicalRequest := strings.Join([]string{
+		method,
+		canonicalURI,
+		canonicalQuery(q),
+		"host:" + base.Host + "\n",
+		"host",
+		"UNSIGNED-PAYLOAD",
+	}, "\n")
+	stringToSign := strings.Join([]string{
+		"AWS4-HMAC-SHA256",
+		amzDate,
+		scope,
+		hexSHA256(canonicalRequest),
+	}, "\n")
+
+	kDate := hmacSHA256([]byte("AWS4"+s.cfg.SecretAccessKey), dateStamp)
+	kRegion := hmacSHA256(kDate, s.cfg.Region)
+	kService := hmacSHA256(kRegion, "s3")
+	kSigning := hmacSHA256(kService, "aws4_request")
+	q.Set("X-Amz-Signature", hex.EncodeToString(hmacSHA256(kSigning, stringToSign)))
+	base.RawQuery = q.Encode()
+
+	return &PresignedURL{URL: base.String(), Method: method, ExpiresAt: now.Add(ttl)}, nil
+}
+
 type listResult struct {
 	Contents              []struct{ Key string `xml:"Key"` } `xml:"Contents"`
 	NextContinuationToken string `xml:"NextContinuationToken"`
diff --git a/apps/backend/internal/storage/s3_test.go b/apps/backend/internal/storage/s3_test.go
index f47df02..2d760ad 100644
--- a/apps/backend/internal/storage/s3_test.go
+++ b/apps/backend/internal/storage/s3_test.go
@@ -6,6 +6,7 @@ import (
 	"io"
 	"net/http"
 	"net/http/httptest"
+	"net/url"
 	"strings"
 	"sync"
 	"testing"
@@ -214,3 +215,37 @@ func TestCanonicalQueryRFC3986(t *testing.T) {
 		t.Fatalf("canonicalQuery = %q, want %q", got, want)
 	}
 }
+
+func TestS3StorePresign(t *testing.T) {
+	store, _ := newTestS3(t)
+	ctx := context.Background()
+
+	dl, err := store.Presign(ctx, "bucket-a", "docs/x.txt", http.MethodGet, 10*time.Minute)
+	if err != nil {
+		t.Fatalf("Presign: %v", err)
+	}
+	if dl.Method != http.MethodGet || dl.ExpiresAt.IsZero() {
+		t.Fatalf("bad presign: %+v", dl)
+	}
+	u, err := url.Parse(dl.URL)
+	if err != nil {
+		t.Fatalf("url parse: %v", err)
+	}
+	q := u.Query()
+	for _, k := range []string{"X-Amz-Algorithm", "X-Amz-Credential", "X-Amz-Date", "X-Amz-Expires", "X-Amz-SignedHeaders", "X-Amz-Signature"} {
+		if q.Get(k) == "" {
+			t.Fatalf("missing %s in %s", k, dl.URL)
+		}
+	}
+	if q.Get("X-Amz-Expires") != "600" || q.Get("X-Amz-SignedHeaders") != "host" {
+		t.Fatalf("bad query: %s", dl.URL)
+	}
+	if _, err := store.Presign(ctx, "b", "k", http.MethodDelete, 0); err == nil {
+		t.Fatal("expected method rejection")
+	}
+	// TTL cap.
+	capped, _ := store.Presign(ctx, "b", "k.txt", http.MethodPut, 48*time.Hour)
+	if cu, _ := url.Parse(capped.URL); cu.Query().Get("X-Amz-Expires") != "3600" {
+		t.Fatalf("ttl not capped: %s", capped.URL)
+	}
+}
diff --git a/apps/backend/internal/storage/store.go b/apps/backend/internal/storage/store.go
index e70e504..e8f7e69 100644
--- a/apps/backend/internal/storage/store.go
+++ b/apps/backend/internal/storage/store.go
@@ -3,6 +3,7 @@ package storage
 import (
 	"context"
 	"io"
+	"time"
 )
 
 // Store is the object-storage contract the platform service depends on.
@@ -14,3 +15,17 @@ type Store interface {
 	MoveBetweenBuckets(sourceBucketID, destinationBucketID, fromKey, toKey string) (string, error)
 	DeleteBucket(bucketID string) error
 }
+
+// PresignedURL is a short-lived direct-to-storage URL for one operation.
+type PresignedURL struct {
+	URL       string    `json:"url"`
+	Method    string    `json:"method"`
+	ExpiresAt time.Time `json:"expires_at"`
+}
+
+// Presigner is an optional capability: stores backed by a real object API
+// (S3) can mint URLs clients call directly. The local driver can't — its
+// "URL" would have to be served by this backend anyway.
+type Presigner interface {
+	Presign(ctx context.Context, bucketID, objectKey, method string, ttl time.Duration) (*PresignedURL, error)
+}
diff --git a/apps/backend/openapi/openapi.yaml b/apps/backend/openapi/openapi.yaml
index a1c8d7d..740c1de 100644
--- a/apps/backend/openapi/openapi.yaml
+++ b/apps/backend/openapi/openapi.yaml
@@ -677,6 +677,37 @@ paths:
             application/json:
               schema:
                 $ref: "#/components/schemas/BucketObject"
+  /buckets/{bucketID}/object-presigns:
+    post:
+      tags: [Storage]
+      operationId: presignBucketObject
+      description: >-
+        Mint a short-lived URL the client calls against object storage
+        directly — keeps large transfers off the backend. Requires
+        BACKEND_STORAGE_DRIVER=s3; the URL's host comes from
+        S3_PUBLIC_ENDPOINT (or S3_ENDPOINT when unset). Signatures bind the
+        host — a presigned URL is valid only at the endpoint it was minted
+        for.
+      security:
+        - bearerAuth: []
+        - apiKeyAuth: []
+      parameters:
+        - $ref: "#/components/parameters/BucketID"
+      requestBody:
+        required: true
+        content:
+          application/json:
+            schema:
+              $ref: "#/components/schemas/PresignObjectRequest"
+      responses:
+        "200":
+          description: Presigned URL
+          content:
+            application/json:
+              schema:
+                $ref: "#/components/schemas/PresignedURL"
+        "404":
+          description: Bucket or object not found (download)
   /buckets/{bucketID}:
     patch:
       tags: [Storage]
@@ -3130,6 +3161,36 @@ components:
           format: uuid
           nullable: true
       required: [objectKey, newObjectKey]
+    PresignObjectRequest:
+      type: object
+      properties:
+        key:
+          type: string
+          description: Object key inside the bucket.
+        op:
+          type: string
+          enum: [download, upload]
+          default: download
+          description: download → GET URL (object must exist); upload → PUT URL (creates/overwrites).
+        ttl_seconds:
+          type: integer
+          minimum: 60
+          maximum: 3600
+          default: 900
+      required: [key]
+    PresignedURL:
+      type: object
+      properties:
+        url:
+          type: string
+          description: Fully-signed URL — call it with the returned method, no auth header needed.
+        method:
+          type: string
+          enum: [GET, PUT]
+        expires_at:
+          type: string
+          format: date-time
+      required: [url, method, expires_at]
     PaginationMetadata:
       type: object
       properties:
diff --git a/apps/cli/src/cli.ts b/apps/cli/src/cli.ts
index 0e3c37a..5075e01 100644
--- a/apps/cli/src/cli.ts
+++ b/apps/cli/src/cli.ts
@@ -12,6 +12,7 @@ import {
   cmdObjectsDownload,
   cmdObjectsList,
   cmdObjectsRemove,
+  cmdObjectsPresign,
   cmdObjectsUpload,
 } from "./commands/objects.js";
 import { cmdOrgsCreate, cmdOrgsList } from "./commands/orgs.js";
@@ -114,6 +115,12 @@ cli
   .command("objects:rm <bucket> <key>", "Delete an object")
   .option("--project <id>", "Project override")
   .action(cmdObjectsRemove);
+cli
+  .command("objects:presign <bucket> <key>", "Mint a presigned URL (s3 driver)")
+  .option("--project <id>", "Project override")
+  .option("--upload", "PUT URL for direct upload instead of GET download")
+  .option("--ttl <seconds>", "Lifetime 60-3600 (default 900)")
+  .action(cmdObjectsPresign);
 
 cli
   .command("keys:list", "List API keys for the current project")
diff --git a/apps/cli/src/commands/objects.ts b/apps/cli/src/commands/objects.ts
index 55b1110..b05593e 100644
--- a/apps/cli/src/commands/objects.ts
+++ b/apps/cli/src/commands/objects.ts
@@ -2,7 +2,7 @@ import { statSync } from "node:fs";
 import { readFile, writeFile } from "node:fs/promises";
 import { basename } from "node:path";
 
-import { StorageService } from "@primora/api-client";
+import { PresignObjectRequest, StorageService } from "@primora/api-client";
 
 import { loadConfig } from "../config.js";
 import {
@@ -133,3 +133,31 @@ export async function cmdObjectsRemove(
   await StorageService.deleteBucketObject({ bucketId, objectKey });
   success(`Deleted ${objectKey}`);
 }
+
+export async function cmdObjectsPresign(
+  bucketRef: string,
+  objectKey: string,
+  options: { project?: string; upload?: boolean; ttl?: string; json?: boolean },
+): Promise<void> {
+  const cfg = loadConfig();
+  requireAuth(cfg);
+  configureClient(cfg);
+
+  const bucketId = await bucketIdFor(cfg, bucketRef, options.project);
+  const presigned = await StorageService.presignBucketObject({
+    bucketId,
+    requestBody: {
+      key: objectKey,
+      op: options.upload
+        ? PresignObjectRequest.op.UPLOAD
+        : PresignObjectRequest.op.DOWNLOAD,
+      ttl_seconds: options.ttl ? Number(options.ttl) : undefined,
+    },
+  });
+  if (isJson(options)) {
+    printJson(presigned);
+    return;
+  }
+  console.log(presigned.url);
+  console.error(`# ${presigned.method} — expires ${presigned.expires_at}`);
+}
diff --git a/packages/api-client/src/generated/index.ts b/packages/api-client/src/generated/index.ts
index 0cb47b3..ec3d314 100644
--- a/packages/api-client/src/generated/index.ts
+++ b/packages/api-client/src/generated/index.ts
@@ -108,6 +108,8 @@ export type { OrganizationSummary } from './models/OrganizationSummary';
 export type { PaginationLimit } from './models/PaginationLimit';
 export type { PaginationMetadata } from './models/PaginationMetadata';
 export type { PaginationOffset } from './models/PaginationOffset';
+export { PresignedURL } from './models/PresignedURL';
+export { PresignObjectRequest } from './models/PresignObjectRequest';
 export type { Project } from './models/Project';
 export type { ProjectID } from './models/ProjectID';
 export { ProjectMember } from './models/ProjectMember';
@@ -258,6 +260,8 @@ export { $OrganizationSummary } from './schemas/$OrganizationSummary';
 export { $PaginationLimit } from './schemas/$PaginationLimit';
 export { $PaginationMetadata } from './schemas/$PaginationMetadata';
 export { $PaginationOffset } from './schemas/$PaginationOffset';
+export { $PresignedURL } from './schemas/$PresignedURL';
+export { $PresignObjectRequest } from './schemas/$PresignObjectRequest';
 export { $Project } from './schemas/$Project';
 export { $ProjectID } from './schemas/$ProjectID';
 export { $ProjectMember } from './schemas/$ProjectMember';
diff --git a/packages/api-client/src/generated/models/PresignObjectRequest.ts b/packages/api-client/src/generated/models/PresignObjectRequest.ts
new file mode 100644
index 0000000..387dbcf
--- /dev/null
+++ b/packages/api-client/src/generated/models/PresignObjectRequest.ts
@@ -0,0 +1,25 @@
+/* generated using openapi-typescript-codegen -- do not edit */
+/* istanbul ignore file */
+/* tslint:disable */
+/* eslint-disable */
+export type PresignObjectRequest = {
+    /**
+     * Object key inside the bucket.
+     */
+    key: string;
+    /**
+     * download → GET URL (object must exist); upload → PUT URL (creates/overwrites).
+     */
+    op?: PresignObjectRequest.op;
+    ttl_seconds?: number;
+};
+export namespace PresignObjectRequest {
+    /**
+     * download → GET URL (object must exist); upload → PUT URL (creates/overwrites).
+     */
+    export enum op {
+        DOWNLOAD = 'download',
+        UPLOAD = 'upload',
+    }
+}
+
diff --git a/packages/api-client/src/generated/models/PresignedURL.ts b/packages/api-client/src/generated/models/PresignedURL.ts
new file mode 100644
index 0000000..9b8cfb9
--- /dev/null
+++ b/packages/api-client/src/generated/models/PresignedURL.ts
@@ -0,0 +1,19 @@
+/* generated using openapi-typescript-codegen -- do not edit */
+/* istanbul ignore file */
+/* tslint:disable */
+/* eslint-disable */
+export type PresignedURL = {
+    /**
+     * Fully-signed URL — call it with the returned method, no auth header needed.
+     */
+    url: string;
+    method: PresignedURL.method;
+    expires_at: string;
+};
+export namespace PresignedURL {
+    export enum method {
+        GET = 'GET',
+        PUT = 'PUT',
+    }
+}
+
diff --git a/packages/api-client/src/generated/schemas/$PresignObjectRequest.ts b/packages/api-client/src/generated/schemas/$PresignObjectRequest.ts
new file mode 100644
index 0000000..52e3bfc
--- /dev/null
+++ b/packages/api-client/src/generated/schemas/$PresignObjectRequest.ts
@@ -0,0 +1,21 @@
+/* generated using openapi-typescript-codegen -- do not edit */
+/* istanbul ignore file */
+/* tslint:disable */
+/* eslint-disable */
+export const $PresignObjectRequest = {
+    properties: {
+        key: {
+            type: 'string',
+            description: `Object key inside the bucket.`,
+            isRequired: true,
+        },
+        op: {
+            type: 'Enum',
+        },
+        ttl_seconds: {
+            type: 'number',
+            maximum: 3600,
+            minimum: 60,
+        },
+    },
+} as const;
diff --git a/packages/api-client/src/generated/schemas/$PresignedURL.ts b/packages/api-client/src/generated/schemas/$PresignedURL.ts
new file mode 100644
index 0000000..1277d20
--- /dev/null
+++ b/packages/api-client/src/generated/schemas/$PresignedURL.ts
@@ -0,0 +1,22 @@
+/* generated using openapi-typescript-codegen -- do not edit */
+/* istanbul ignore file */
+/* tslint:disable */
+/* eslint-disable */
+export const $PresignedURL = {
+    properties: {
+        url: {
+            type: 'string',
+            description: `Fully-signed URL — call it with the returned method, no auth header needed.`,
+            isRequired: true,
+        },
+        method: {
+            type: 'Enum',
+            isRequired: true,
+        },
+        expires_at: {
+            type: 'string',
+            isRequired: true,
+            format: 'date-time',
+        },
+    },
+} as const;
diff --git a/packages/api-client/src/generated/services/StorageService.ts b/packages/api-client/src/generated/services/StorageService.ts
index d3086be..8156a66 100644
--- a/packages/api-client/src/generated/services/StorageService.ts
+++ b/packages/api-client/src/generated/services/StorageService.ts
@@ -7,6 +7,8 @@ import type { BucketObject } from '../models/BucketObject';
 import type { BucketObjectListResponse } from '../models/BucketObjectListResponse';
 import type { CopyBucketObjectRequest } from '../models/CopyBucketObjectRequest';
 import type { CreateBucketRequest } from '../models/CreateBucketRequest';
+import type { PresignedURL } from '../models/PresignedURL';
+import type { PresignObjectRequest } from '../models/PresignObjectRequest';
 import type { UpdateBucketObjectRequest } from '../models/UpdateBucketObjectRequest';
 import type { UpdateBucketRequest } from '../models/UpdateBucketRequest';
 import type { CancelablePromise } from '../core/CancelablePromise';
@@ -131,6 +133,31 @@ export class StorageService {
             mediaType: 'application/json',
         });
     }
+    /**
+     * Mint a short-lived URL the client calls against object storage directly — keeps large transfers off the backend. Requires BACKEND_STORAGE_DRIVER=s3; the URL's host comes from S3_PUBLIC_ENDPOINT (or S3_ENDPOINT when unset). Signatures bind the host — a presigned URL is valid only at the endpoint it was minted for.
+     * @returns PresignedURL Presigned URL
+     * @throws ApiError
+     */
+    public static presignBucketObject({
+        bucketId,
+        requestBody,
+    }: {
+        bucketId: string,
+        requestBody: PresignObjectRequest,
+    }): CancelablePromise<PresignedURL> {
+        return __request(OpenAPI, {
+            method: 'POST',
+            url: '/buckets/{bucketID}/object-presigns',
+            path: {
+                'bucketID': bucketId,
+            },
+            body: requestBody,
+            mediaType: 'application/json',
+            errors: {
+                404: `Bucket or object not found (download)`,
+            },
+        });
+    }
     /**
      * @returns void
      * @throws ApiError