diff --git a/src/constants.ts b/src/constants.ts
index 38e9f35..5f84659 100644
--- a/src/constants.ts
+++ b/src/constants.ts
@@ -165,6 +165,18 @@ export const ENTRY_POINT_NAMES: Record<string, Set<string>> = {
   php: new Set(["main"]),
 };
 
+// ── Path normalization ──────────────────────────────────────────────────
+
+/**
+ * Normalize path separators to forward slashes.
+ * On POSIX this is a no-op; on Windows it replaces every `\` with `/`.
+ * Used for graph node keys, fileSet entries, and query inputs so that
+ * lookups succeed regardless of the host OS separator convention.
+ */
+export function toForwardSlash(p: string): string {
+  return p.replace(/\\/g, "/");
+}
+
 // ── File type configuration ─────────────────────────────────────────────
 
 export const SUPPORTED_EXTENSIONS = new Set([
diff --git a/src/services/code-graph.ts b/src/services/code-graph.ts
index f566b56..c0b0854 100644
--- a/src/services/code-graph.ts
+++ b/src/services/code-graph.ts
@@ -6,7 +6,7 @@ import { createRequire } from "node:module";
 import path from "node:path";
 import { Lang, registerDynamicLanguage } from "@ast-grep/napi";
 import { graphCollectionName, projectIdFromPath } from "../config.js";
-import { EXTRA_EXTENSIONS, getLanguageFromExtension, MAX_GRAPH_FILE_BYTES } from "../constants.js";
+import { EXTRA_EXTENSIONS, getLanguageFromExtension, MAX_GRAPH_FILE_BYTES, toForwardSlash } from "../constants.js";
 import type {
   CodeGraph, CodeGraphEdge, CodeGraphNode,
   SymbolEdge, SymbolGraphFilePayload, SymbolGraphMeta, SymbolNode, SymbolRef,
@@ -596,7 +596,7 @@ async function getGraphableFiles(
 
     for (const entry of entries) {
       const fullPath = path.join(dir, entry.name);
-      const relPath = path.relative(projectPath, fullPath);
+      const relPath = toForwardSlash(path.relative(projectPath, fullPath));
 
       if (shouldIgnore(ig, relPath)) continue;
 
diff --git a/src/services/graph-analysis.ts b/src/services/graph-analysis.ts
index 62df125..1650092 100644
--- a/src/services/graph-analysis.ts
+++ b/src/services/graph-analysis.ts
@@ -1,17 +1,20 @@
 // SPDX-License-Identifier: AGPL-3.0-only
 // Copyright (C) 2026 Giancarlo Erra - Altaire Limited
 import path from "node:path";
-import { getLanguageFromExtension } from "../constants.js";
+import { getLanguageFromExtension, toForwardSlash } from "../constants.js";
 import type { CodeGraph } from "../types.js";
 
 /**
  * Get dependencies for a specific file.
+ * The input path is normalized to forward slashes so lookups succeed
+ * regardless of whether the caller passes `/` or `\` separators.
  */
 export function getFileDependencies(graph: CodeGraph, relativePath: string): {
   imports: string[];
   importedBy: string[];
 } {
-  const node = graph.nodes.find((n) => n.relativePath === relativePath);
+  const normalized = toForwardSlash(relativePath);
+  const node = graph.nodes.find((n) => toForwardSlash(n.relativePath) === normalized);
   if (!node) {
     return { imports: [], importedBy: [] };
   }
diff --git a/src/services/graph-impact.ts b/src/services/graph-impact.ts
index 6d1cd8b..6bb7e5f 100644
--- a/src/services/graph-impact.ts
+++ b/src/services/graph-impact.ts
@@ -7,7 +7,7 @@
  * lazy-loaded per-file payloads.
  */
 
-import { MAX_FLOW_DEPTH, MAX_IMPACT_DEPTH } from "../constants.js";
+import { MAX_FLOW_DEPTH, MAX_IMPACT_DEPTH, toForwardSlash } from "../constants.js";
 import type { SymbolNode } from "../types.js";
 import {
   type SymbolGraphCache,
@@ -184,7 +184,10 @@ export async function getSymbolContext(
 ): Promise<SymbolContext[]> {
   const nameIndex = await cache.getNameIndex();
   let refs = nameIndex.get(name) ?? [];
-  if (fileHint) refs = refs.filter((r) => r.file === fileHint);
+  if (fileHint) {
+    const normalizedHint = toForwardSlash(fileHint);
+    refs = refs.filter((r) => r.file === normalizedHint);
+  }
   if (refs.length === 0) return [];
 
   const reverseIndex = await cache.getReverseFileIndex();
@@ -237,7 +240,7 @@ export async function listSymbols(
   const out: SymbolNode[] = [];
 
   if (opts.file) {
-    const payload = await cache.getFilePayload(opts.file);
+    const payload = await cache.getFilePayload(toForwardSlash(opts.file));
     if (!payload) return [];
     for (const s of payload.symbols) {
       if (s.name === "<module>") continue;
diff --git a/src/services/graph-resolution.ts b/src/services/graph-resolution.ts
index 58a4744..a6f1370 100644
--- a/src/services/graph-resolution.ts
+++ b/src/services/graph-resolution.ts
@@ -2,6 +2,7 @@
 // Copyright (C) 2026 Giancarlo Erra - Altaire Limited
 import { readFileSync } from "node:fs";
 import path from "node:path";
+import { toForwardSlash } from "../constants.js";
 import type { PathAliases } from "./graph-aliases.js";
 
 // ── Module resolution ────────────────────────────────────────────────────
@@ -12,7 +13,7 @@ import type { PathAliases } from "./graph-aliases.js";
  * For a Maven/Gradle multi-module layout such as:
  *   module-a/sub-module/src/main/java/com/example/Foo.java
  * the map entry is:
- *   key:   "com/example/Foo.java"  (platform-normalised with path.sep)
+ *   key:   "com/example/Foo.java"  (forward-slash-normalized)
  *   value: "module-a/sub-module/src/main/java/com/example/Foo.java"
  *
  * This enables O(1) resolution of fully-qualified class names that cannot be
@@ -41,7 +42,7 @@ export function buildJvmSuffixMap(fileSet: Set<string>): Map<string, string> {
 
     if (idx !== -1) {
       // classPath = everything after src/main/<lang>, e.g. com/example/Foo.java
-      const classPath = parts.slice(idx + 3).join(path.sep);
+      const classPath = parts.slice(idx + 3).join("/");
       // Only register the first match to avoid ambiguity for duplicate class names.
       if (!map.has(classPath)) {
         map.set(classPath, f);
@@ -184,13 +185,9 @@ export function buildGoModuleInfo(
 
   const packageMap = new Map<string, string>();
   for (const f of goFiles) {
-    // Normalize the directory key to forward slashes. Go import paths
-    // always use forward slashes regardless of host OS, so the key must
-    // be in the same form for the lookup in resolveImport to succeed on
-    // Windows (where path.dirname produces backslash separators for
-    // nested directories like `pkg\subpkg`). The map value keeps the
-    // file's native-separator form so it matches fileSet entries used
-    // elsewhere as graph node keys.
+    // Go import paths always use forward slashes. fileSet entries are
+    // also forward-slash-normalized (see toForwardSlash in constants.ts),
+    // so the key and value are both in the same form.
     const dir = path.dirname(f).replace(/\\/g, "/"); // "." for files at the project root
     if (!packageMap.has(dir)) {
       packageMap.set(dir, f);
@@ -351,7 +348,7 @@ export function resolveImport(
       //    The map is built once per graph build (O(n)) and looked up in O(1).
       if (jvmSuffixMap) {
         for (const ext of exts) {
-          const classPath = filePath.replace(/\//g, path.sep) + ext;
+          const classPath = filePath + ext;
           const found = jvmSuffixMap.get(classPath);
           if (found) return found;
         }
@@ -419,7 +416,7 @@ export function resolveImport(
           path.join(sourceDir, moduleSpecifier, "mod.rs"),
         ];
         for (const candidate of candidates) {
-          const rel = path.relative(projectPath, candidate);
+          const rel = toForwardSlash(path.relative(projectPath, candidate));
           if (fileSet.has(rel)) return rel;
         }
       }
@@ -564,7 +561,7 @@ function resolveRelativePath(
   extensions: string[],
 ): string | null {
   const fullPath = path.resolve(baseDir, modulePath);
-  const relPath = path.relative(projectPath, fullPath);
+  const relPath = toForwardSlash(path.relative(projectPath, fullPath));
 
   // Direct match
   if (fileSet.has(relPath)) return relPath;
@@ -590,7 +587,7 @@ function resolveRelativePath(
 
   // Try as directory with index file
   for (const ext of extensions) {
-    const indexFile = path.join(relPath, `index${ext}`);
+    const indexFile = toForwardSlash(path.join(relPath, `index${ext}`));
     if (fileSet.has(indexFile)) return indexFile;
   }
 
@@ -600,11 +597,11 @@ function resolveRelativePath(
     const base = path.basename(relPath);
     if (!base.startsWith("_")) {
       // Try _name (direct)
-      const partial = path.join(dir, `_${base}`);
+      const partial = toForwardSlash(path.join(dir, `_${base}`));
       if (fileSet.has(partial)) return partial;
       // Try _name with extensions
       for (const ext of extensions) {
-        const partialExt = path.join(dir, `_${base}${ext}`);
+        const partialExt = toForwardSlash(path.join(dir, `_${base}${ext}`));
         if (fileSet.has(partialExt)) return partialExt;
       }
     }
@@ -612,7 +609,7 @@ function resolveRelativePath(
 
   // Python: try __init__.py
   if (extensions.includes(".py")) {
-    const initFile = path.join(relPath, "__init__.py");
+    const initFile = toForwardSlash(path.join(relPath, "__init__.py"));
     if (fileSet.has(initFile)) return initFile;
   }
 
diff --git a/tests/unit/constants.test.ts b/tests/unit/constants.test.ts
index 740a210..8656eb7 100644
--- a/tests/unit/constants.test.ts
+++ b/tests/unit/constants.test.ts
@@ -27,6 +27,7 @@ import {
   SEARCH_MIN_SCORE,
   SPECIAL_FILES,
   SUPPORTED_EXTENSIONS,
+  toForwardSlash,
 } from "../../src/constants.js";
 
 describe("constants", () => {
@@ -373,6 +374,37 @@ describe("constants", () => {
   });
 });
 
+describe("toForwardSlash", () => {
+  it("returns the same string when no backslashes are present", () => {
+    expect(toForwardSlash("src/index.ts")).toBe("src/index.ts");
+  });
+
+  it("replaces single backslash with forward slash", () => {
+    expect(toForwardSlash("src\\index.ts")).toBe("src/index.ts");
+  });
+
+  it("replaces multiple backslashes in a path", () => {
+    expect(toForwardSlash("src\\services\\graph-analysis.ts")).toBe("src/services/graph-analysis.ts");
+  });
+
+  it("handles deeply nested Windows paths", () => {
+    expect(toForwardSlash("src\\a\\b\\c\\d\\file.ts")).toBe("src/a/b/c/d/file.ts");
+  });
+
+  it("handles empty string", () => {
+    expect(toForwardSlash("")).toBe("");
+  });
+
+  it("handles path with mixed separators", () => {
+    expect(toForwardSlash("src/services\\graph-analysis.ts")).toBe("src/services/graph-analysis.ts");
+  });
+
+  it("is a no-op on POSIX-style paths", () => {
+    const posixPath = "src/services/code-graph.ts";
+    expect(toForwardSlash(posixPath)).toBe(posixPath);
+  });
+});
+
 describe("resolveQdrantPort", () => {
   it("returns explicit port from URL", () => {
     expect(resolveQdrantPort("https://qdrant.example.com:6333")).toBe(6333);
diff --git a/tests/unit/graph-analysis.test.ts b/tests/unit/graph-analysis.test.ts
index ca88ef7..89f7034 100644
--- a/tests/unit/graph-analysis.test.ts
+++ b/tests/unit/graph-analysis.test.ts
@@ -113,6 +113,58 @@ describe("graph-analysis", () => {
       expect(deps.imports).toHaveLength(0);
       expect(deps.importedBy).toHaveLength(0);
     });
+
+    it("normalizes Windows backslash paths to match forward-slash graph keys", () => {
+      const graph = createSampleGraph();
+      // Graph keys use forward slashes; simulate a Windows-style query
+      const deps = getFileDependencies(graph, "src\\index.ts");
+
+      expect(deps.imports).toContain("src/utils.ts");
+      expect(deps.imports).toContain("src/types.ts");
+    });
+
+    it("normalizes deeply nested Windows paths", () => {
+      const nodes: CodeGraphNode[] = [
+        makeNode("src/services/graph/analysis.ts", ["src/types.ts"], []),
+        makeNode("src/types.ts", [], ["src/services/graph/analysis.ts"]),
+      ];
+      const edges: CodeGraphEdge[] = [
+        makeEdge("src/services/graph/analysis.ts", "src/types.ts"),
+      ];
+      const graph = makeGraph(nodes, edges);
+
+      const deps = getFileDependencies(graph, "src\\services\\graph\\analysis.ts");
+      expect(deps.imports).toContain("src/types.ts");
+    });
+
+    it("handles mixed separator paths", () => {
+      const graph = createSampleGraph();
+      const deps = getFileDependencies(graph, "src/utils.ts");
+      const depsMixed = getFileDependencies(graph, "src\\utils.ts");
+
+      expect(depsMixed.imports).toEqual(deps.imports);
+      expect(depsMixed.importedBy).toEqual(deps.importedBy);
+    });
+
+    it("finds nodes in a legacy cached graph with backslash keys", () => {
+      // Simulate a graph built on Windows before the fix: stored keys have backslashes
+      const nodes: CodeGraphNode[] = [
+        makeNode("src\\services\\api.ts", ["src\\types.ts"], []),
+        makeNode("src\\types.ts", [], ["src\\services\\api.ts"]),
+      ];
+      // Fix relativePath (makeNode sets it from the argument)
+      nodes[0].relativePath = "src\\services\\api.ts";
+      nodes[1].relativePath = "src\\types.ts";
+
+      const edges: CodeGraphEdge[] = [
+        makeEdge("src\\services\\api.ts", "src\\types.ts"),
+      ];
+      const graph = makeGraph(nodes, edges);
+
+      // Query with forward slashes should still find the node
+      const deps = getFileDependencies(graph, "src/services/api.ts");
+      expect(deps.imports).toContain("src\\types.ts");
+    });
   });
 
   describe("findCircularDependencies", () => {