diff --git a/migrations/004_workflow_relations.sql b/migrations/004_workflow_relations.sql
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+-- Workflow Relations Schema
+-- Stores semantic relations between workflow canvas nodes with versioning support
+
+-- Table for storing workflow relations with relation wording
+CREATE TABLE IF NOT EXISTS workflow_relations (
+    id UUID PRIMARY KEY DEFAULT gen_random_uuid(),
+    workflow_id VARCHAR(255) NOT NULL,
+    version INTEGER NOT NULL,
+    source_node_id VARCHAR(255) NOT NULL,
+    target_node_id VARCHAR(255) NOT NULL,
+    relation_type VARCHAR(50) NOT NULL, -- data-flow, dependency, conditional, parallel
+    label TEXT NOT NULL,
+    relation_wording JSONB NOT NULL, -- {verb, source_output, target_input, connection_type, confidence, semantic_match}
+    metadata JSONB,
+    created_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP,
+    FOREIGN KEY (workflow_id) REFERENCES workflows(id) ON DELETE CASCADE,
+    UNIQUE(workflow_id, source_node_id, target_node_id, version)
+);
+
+-- Table for versioned history of relation changes
+CREATE TABLE IF NOT EXISTS workflow_relation_versions (
+    id UUID PRIMARY KEY DEFAULT gen_random_uuid(),
+    workflow_id VARCHAR(255) NOT NULL,
+    edge_id VARCHAR(255) NOT NULL,
+    version_num INTEGER NOT NULL,
+    operation VARCHAR(10) NOT NULL, -- CREATE, UPDATE, DELETE
+    snapshot JSONB NOT NULL,
+    changed_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP,
+    changed_by VARCHAR(255),
+    fields_changed JSONB, -- ["field1", "field2"]
+    FOREIGN KEY (workflow_id) REFERENCES workflows(id) ON DELETE CASCADE,
+    UNIQUE(workflow_id, edge_id, version_num)
+);
+
+-- Table for GraphRAG indexing metadata
+CREATE TABLE IF NOT EXISTS workflow_rag_index (
+    id UUID PRIMARY KEY DEFAULT gen_random_uuid(),
+    workflow_id VARCHAR(255) NOT NULL UNIQUE,
+    version INTEGER NOT NULL,
+    indexed_status VARCHAR(20) NOT NULL DEFAULT 'pending', -- pending, indexed, partial, failed
+    embedding_model VARCHAR(100),
+    last_indexed_at TIMESTAMP,
+    index_metadata JSONB,
+    created_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP,
+    updated_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP,
+    FOREIGN KEY (workflow_id) REFERENCES workflows(id) ON DELETE CASCADE
+);
+
+-- Indexes for performance
+CREATE INDEX idx_workflow_relations_workflow_version ON workflow_relations(workflow_id, version);
+CREATE INDEX idx_workflow_relations_type ON workflow_relations(relation_type);
+CREATE INDEX idx_workflow_relations_nodes ON workflow_relations(source_node_id, target_node_id);
+CREATE INDEX idx_workflow_relation_versions_workflow_edge ON workflow_relation_versions(workflow_id, edge_id);
+CREATE INDEX idx_workflow_relation_versions_operation ON workflow_relation_versions(operation);
+CREATE INDEX idx_workflow_rag_index_status ON workflow_rag_index(indexed_status);