diff --git a/cmd/server/tests/media_note_length_test.go b/cmd/server/tests/media_note_length_test.go
new file mode 100644
index 0000000..3447af9
--- /dev/null
+++ b/cmd/server/tests/media_note_length_test.go
@@ -0,0 +1,54 @@
+package main
+
+import (
+	"bytes"
+	"encoding/json"
+	"io"
+	"net/http"
+	"strings"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+// TestMediaNoteLengthLimits verifies the note content validator cap
+// (internal/handlers/media.go): content up to 100,000 chars is accepted,
+// longer content is rejected with 400.
+func TestMediaNoteLengthLimits(t *testing.T) {
+	setup := setupTestServer(t)
+
+	token := setup.Token
+	mediaItemID := createTestMediaItemID(t, setup)
+
+	postNote := func(content string) int {
+		payload := map[string]interface{}{
+			"content":  content,
+			"position": "page:1",
+		}
+		body, _ := json.Marshal(payload)
+		req, _ := http.NewRequest("POST", setup.Server.URL+"/api/media-items/"+mediaItemID+"/notes", bytes.NewBuffer(body))
+		req.Header.Set("Content-Type", "application/json")
+		req.Header.Set("Authorization", "Bearer "+token)
+
+		client := &http.Client{}
+		resp, err := client.Do(req)
+		require.NoError(t, err)
+		defer func(Body io.ReadCloser) {
+			_ = Body.Close()
+		}(resp.Body)
+		return resp.StatusCode
+	}
+
+	t.Run("50k-char note accepted", func(t *testing.T) {
+		assert.Equal(t, http.StatusCreated, postNote(strings.Repeat("a", 50000)))
+	})
+
+	t.Run("100k-char note accepted at boundary", func(t *testing.T) {
+		assert.Equal(t, http.StatusCreated, postNote(strings.Repeat("b", 100000)))
+	})
+
+	t.Run("over-limit note rejected", func(t *testing.T) {
+		assert.Equal(t, http.StatusBadRequest, postNote(strings.Repeat("c", 100001)))
+	})
+}
diff --git a/internal/handlers/media.go b/internal/handlers/media.go
index e2aa501..60a3cc0 100644
--- a/internal/handlers/media.go
+++ b/internal/handlers/media.go
@@ -102,13 +102,13 @@ type UpdateMediaItemRequest struct {
 
 // CreateMediaNoteRequest represents the request for creating a media note
 type CreateMediaNoteRequest struct {
-	Content  string `json:"content" validate:"required,min=1,max=10000"`
+	Content  string `json:"content" validate:"required,min=1,max=100000"`
 	Position string `json:"position"`
 }
 
 // UpdateMediaNoteRequest represents the request for updating a media note
 type UpdateMediaNoteRequest struct {
-	Content  string `json:"content" validate:"required,min=1,max=10000"`
+	Content  string `json:"content" validate:"required,min=1,max=100000"`
 	Position string `json:"position"`
 }
 
@@ -120,7 +120,7 @@ type CreateMediaHighlightRequest struct {
 	EpubcfiStart     string  `json:"epubcfi_start" validate:"max=2000"`
 	EpubcfiEnd       string  `json:"epubcfi_end" validate:"max=2000"`
 	Color            string  `json:"color" validate:"omitempty,len=7"`
-	NoteText         string  `json:"note_text" validate:"max=10000"`
+	NoteText         string  `json:"note_text" validate:"max=100000"`
 	NoteID           string  `json:"note_id"`
 	PercentageStart  float64 `json:"percentage_start"`
 	PercentageEnd    float64 `json:"percentage_end"`
@@ -135,7 +135,7 @@ type UpdateMediaHighlightRequest struct {
 	EpubcfiStart     string  `json:"epubcfi_start" validate:"max=2000"`
 	EpubcfiEnd       string  `json:"epubcfi_end" validate:"max=2000"`
 	Color            string  `json:"color" validate:"omitempty,len=7"`
-	NoteText         string  `json:"note_text" validate:"max=10000"`
+	NoteText         string  `json:"note_text" validate:"max=100000"`
 	NoteID           string  `json:"note_id"`
 	PercentageStart  float64 `json:"percentage_start"`
 	PercentageEnd    float64 `json:"percentage_end"`
@@ -146,7 +146,7 @@ type UpdateMediaHighlightRequest struct {
 type CreateMediaBookmarkRequest struct {
 	Title            string  `json:"title" validate:"required,min=1,max=255"`
 	Position         string  `json:"position" validate:"max=100"`
-	Notes            string  `json:"notes" validate:"max=10000"`
+	Notes            string  `json:"notes" validate:"max=100000"`
 	CfiPosition      string  `json:"cfi_position" validate:"max=255"`
 	PageNumber       int32   `json:"page_number"`
 	ChapterNumber    int32   `json:"chapter_number"`
@@ -160,7 +160,7 @@ type CreateMediaBookmarkRequest struct {
 // UpdateMediaBookmarkRequest represents the request for updating a media bookmark
 type UpdateMediaBookmarkRequest struct {
 	Title    string `json:"title" validate:"required,min=1,max=255"`
-	Notes    string `json:"notes" validate:"max=10000"`
+	Notes    string `json:"notes" validate:"max=100000"`
 	Position string `json:"position" validate:"max=100"`
 }