diff --git a/.planning/STATE.md b/.planning/STATE.md
index 6033ccb6..77a13e68 100644
--- a/.planning/STATE.md
+++ b/.planning/STATE.md
@@ -9,19 +9,19 @@ See: .planning/PROJECT.md (updated 2026-01-09)
 
 ## Current Position
 
-Phase: 34 of 35 (Context-Aware Agentic Workflow Editing)
-Plan: 3 of 3 in current phase
-Status: Complete
-Last activity: 2026-01-30 - Completed plan 03 (Store Integration and ChatPanel Wiring)
+Phase: 35 of 35 (Large Workflow Handling)
+Plan: 1 of 3 in current phase
+Status: In Progress
+Last activity: 2026-01-31 - Completed plan 02 (Selection-Aware Subgraph Extraction)
 
 Progress: ░░░░░░░░░░ 6%
 
 ## Performance Metrics
 
 **Velocity:**
-- Total plans completed: 33
+- Total plans completed: 34
 - Average duration: 7 min
-- Total execution time: 3.7 hours
+- Total execution time: 3.9 hours
 
 **By Phase:**
 
@@ -56,10 +56,11 @@ Progress: ░░░░░░░░░░ 6%
 | 32. Chat UI Foundation | 2/2 | 9 min | 4.5 min |
 | 33. Workflow Edit Safety | 2/2 | 5 min | 5 min |
 | 34. Agentic Workflow Editing | 3/3 | 13 min | 4.3 min |
+| 35. Large Workflow Handling | 1/3 | 10 min | 10 min |
 
 **Recent Trend:**
-- Last 5 plans: 5 min, 5 min, 5 min, 8 min, <1 min
-- Trend: Phase 34 complete - agentic workflow editing shipped in 3 compact plans
+- Last 5 plans: 5 min, 5 min, 8 min, <1 min, 10 min
+- Trend: Phase 35 started - selection-aware context scoping for large workflows
 
 ## Accumulated Context
 
@@ -206,7 +207,7 @@ Recent decisions affecting current work:
 
 ## Session Continuity
 
-Last session: 2026-01-30
-Stopped at: Completed Phase 34 Plan 03 (Store Integration and ChatPanel Wiring)
+Last session: 2026-01-31
+Stopped at: Completed Phase 35 Plan 02 (Selection-Aware Subgraph Extraction)
 Resume file: None
-Next action: Phase 34 complete - proceed to next phase or milestone planning
+Next action: Proceed to plan 35-03 (Chat Context Builder Integration) or continue with parallel plan 35-01
diff --git a/src/lib/chat/contextBuilder.ts b/src/lib/chat/contextBuilder.ts
index fabe3d90..1e5eaebd 100644
--- a/src/lib/chat/contextBuilder.ts
+++ b/src/lib/chat/contextBuilder.ts
@@ -1,30 +1,175 @@
 import { WorkflowNode } from "@/types";
 import { WorkflowEdge } from "@/types/workflow";
 import type {
+  ImageInputNodeData,
+  AnnotationNodeData,
+  PromptNodeData,
   NanoBananaNodeData,
   GenerateVideoNodeData,
+  LLMGenerateNodeData,
+  SplitGridNodeData,
+  OutputNodeData,
 } from "@/types";
 
+/**
+ * Binary fields by node type - fields containing base64 data URLs
+ */
+const BINARY_FIELDS_BY_TYPE: Record<string, string[]> = {
+  imageInput: ["image"],
+  annotation: ["sourceImage", "outputImage"],
+  nanoBanana: ["inputImages", "outputImage"],
+  generateVideo: ["inputImages", "outputVideo"],
+  llmGenerate: ["inputImages"],
+  splitGrid: ["sourceImage"],
+  output: ["image", "video"],
+  prompt: [],
+};
+
+/**
+ * History fields to strip completely (irrelevant for editing context)
+ */
+const HISTORY_FIELDS = [
+  "imageHistory",
+  "videoHistory",
+  "selectedHistoryIndex",
+  "selectedVideoHistoryIndex",
+];
+
+/**
+ * Ref fields to strip completely (internal storage tracking)
+ */
+const REF_FIELDS = [
+  "imageRef",
+  "outputImageRef",
+  "sourceImageRef",
+  "inputImageRefs",
+  "outputVideoRef",
+];
+
+/**
+ * Stripped node with binary data replaced by metadata placeholders
+ */
+export interface StrippedNode {
+  id: string;
+  type: string;
+  position: { x: number; y: number };
+  data: Record<string, unknown>;
+}
+
 /**
  * Lightweight workflow context for LLM consumption.
  * Strips all base64 image data, history arrays, and internal state.
  */
 export interface WorkflowContext {
   nodeCount: number;
-  nodes: Array<{
-    id: string;
-    type: string;
-    title: string;
-    model?: string;
-  }>;
+  nodes: StrippedNode[];
   connections: Array<{
     from: string;
     to: string;
-    type: string;
+    sourceHandle: string | null;
+    targetHandle: string | null;
   }>;
   isEmpty: boolean;
 }
 
+/**
+ * Estimates the size of a base64 data URL in kilobytes.
+ */
+function estimateBase64Size(dataUrl: string): number {
+  // Base64 encoding overhead: every 3 bytes becomes 4 characters
+  // So to get original size: (length * 3) / 4
+  return Math.round((dataUrl.length * 3) / 4 / 1024);
+}
+
+/**
+ * Formats a binary field placeholder with metadata.
+ */
+function formatBinaryPlaceholder(
+  value: string | string[],
+  fieldName: string,
+  context?: string
+): string {
+  // Handle array fields (inputImages)
+  if (Array.isArray(value)) {
+    if (value.length === 0) {
+      return "[no images]";
+    }
+    const count = value.length;
+    return `[${count} image(s)]`;
+  }
+
+  // Handle single string fields
+  const sizeKB = estimateBase64Size(value);
+  const isVideo = fieldName.toLowerCase().includes("video");
+  const type = isVideo ? "video" : "image";
+
+  // Format: [type: context, sizeKB] or [type: sizeKB] if no context
+  if (context) {
+    return `[${type}: ${context}, ${sizeKB}KB]`;
+  }
+  return `[${type}: ${sizeKB}KB]`;
+}
+
+/**
+ * Strips binary data from workflow nodes, preserving all parameters and adding metadata placeholders.
+ *
+ * @param nodes - Workflow nodes to strip
+ * @returns Stripped nodes with binary data replaced by metadata
+ */
+export function stripBinaryData(nodes: WorkflowNode[]): StrippedNode[] {
+  return nodes.map((node) => {
+    const strippedData: Record<string, unknown> = {};
+    const binaryFields = BINARY_FIELDS_BY_TYPE[node.type] || [];
+
+    // Copy all data fields except binary, history, and ref fields
+    for (const [key, value] of Object.entries(node.data)) {
+      // Skip history fields
+      if (HISTORY_FIELDS.includes(key)) {
+        continue;
+      }
+      // Skip ref fields
+      if (REF_FIELDS.includes(key)) {
+        continue;
+      }
+
+      // Handle binary fields
+      if (binaryFields.includes(key)) {
+        if (value === null || value === undefined) {
+          strippedData[key] = value;
+        } else {
+          // Add context based on node type
+          let context: string | undefined;
+          if (node.type === "nanoBanana" || node.type === "generateVideo") {
+            const nodeData = node.data as NanoBananaNodeData | GenerateVideoNodeData;
+            context = nodeData.selectedModel?.displayName;
+          } else if (node.type === "imageInput") {
+            const nodeData = node.data as ImageInputNodeData;
+            if (nodeData.dimensions) {
+              context = `${nodeData.dimensions.width}x${nodeData.dimensions.height}`;
+            }
+          }
+
+          strippedData[key] = formatBinaryPlaceholder(
+            value as string | string[],
+            key,
+            context
+          );
+        }
+      } else {
+        // Copy non-binary field as-is
+        strippedData[key] = value;
+      }
+    }
+
+    return {
+      id: node.id,
+      type: node.type,
+      position: node.position,
+      data: strippedData,
+    };
+  });
+}
+
 /**
  * Builds a lightweight workflow context from nodes and edges.
  * Omits all base64 image data, history arrays, and internal state.
@@ -39,38 +184,20 @@ export function buildWorkflowContext(
 ): WorkflowContext {
   const isEmpty = nodes.length === 0;
 
-  // Map nodes to lightweight summaries
-  const nodeSummaries = nodes.map((node) => {
-    // Extract title: use customTitle if available, otherwise generate from type
-    const title =
-      (node.data as { customTitle?: string }).customTitle ||
-      generateNodeTitle(node.type);
-
-    // For nanoBanana and generateVideo nodes, include model name
-    let model: string | undefined;
-    if (node.type === "nanoBanana" || node.type === "generateVideo") {
-      const nodeData = node.data as NanoBananaNodeData | GenerateVideoNodeData;
-      model = nodeData.selectedModel?.displayName;
-    }
-
-    return {
-      id: node.id,
-      type: node.type,
-      title,
-      ...(model && { model }),
-    };
-  });
+  // Strip binary data from all nodes
+  const strippedNodes = stripBinaryData(nodes);
 
   // Map edges to connection summaries
   const connections = edges.map((edge) => ({
     from: edge.source,
     to: edge.target,
-    type: edge.sourceHandle || "unknown",
+    sourceHandle: edge.sourceHandle || null,
+    targetHandle: edge.targetHandle || null,
   }));
 
   return {
     nodeCount: nodes.length,
-    nodes: nodeSummaries,
+    nodes: strippedNodes,
     connections,
     isEmpty,
   };
@@ -92,8 +219,8 @@ export function formatContextForPrompt(context: WorkflowContext): string {
   // List nodes
   lines.push(`Current workflow has ${context.nodeCount} node(s):`);
   for (const node of context.nodes) {
-    const modelInfo = node.model ? ` (${node.model})` : "";
-    lines.push(`  - ${node.id}: ${node.title}${modelInfo}`);
+    const title = (node.data.customTitle as string) || generateNodeTitle(node.type);
+    lines.push(`  - ${node.id}: ${title}`);
   }
 
   // List connections
@@ -101,7 +228,8 @@ export function formatContextForPrompt(context: WorkflowContext): string {
     lines.push("");
     lines.push("Connections:");
     for (const conn of context.connections) {
-      lines.push(`  - ${conn.from} → ${conn.to} (${conn.type})`);
+      const handleInfo = conn.sourceHandle ? ` (${conn.sourceHandle})` : "";
+      lines.push(`  - ${conn.from} → ${conn.to}${handleInfo}`);
     }
   }