diff --git a/packages/opencode/src/lsp/index.ts b/packages/opencode/src/lsp/index.ts
index 0fd3b69dfcd..0015c64bfa1 100644
--- a/packages/opencode/src/lsp/index.ts
+++ b/packages/opencode/src/lsp/index.ts
@@ -3,7 +3,7 @@ import { Bus } from "@/bus"
 import { Log } from "../util/log"
 import { LSPClient } from "./client"
 import path from "path"
-import { pathToFileURL } from "url"
+import { fileURLToPath, pathToFileURL } from "url"
 import { LSPServer } from "./server"
 import z from "zod"
 import { Config } from "../config/config"
@@ -11,6 +11,14 @@ import { spawn } from "child_process"
 import { Instance } from "../project/instance"
 import { Flag } from "@/flag/flag"
 
+function normalizePathForUri(filePath: string): string {
+  const resolved = path.resolve(filePath)
+  if (process.platform === "win32" && /^[a-z]:/.test(resolved)) {
+    return resolved[0].toUpperCase() + resolved.slice(1)
+  }
+  return resolved
+}
+
 export namespace LSP {
   const log = Log.create({ service: "lsp" })
 
@@ -301,11 +309,12 @@ export namespace LSP {
   }
 
   export async function hover(input: { file: string; line: number; character: number }) {
-    return run(input.file, (client) => {
+    const file = normalizePathForUri(input.file)
+    return run(file, (client) => {
       return client.connection
         .sendRequest("textDocument/hover", {
           textDocument: {
-            uri: pathToFileURL(input.file).href,
+            uri: pathToFileURL(file).href,
           },
           position: {
             line: input.line,
@@ -369,7 +378,7 @@ export namespace LSP {
   }
 
   export async function documentSymbol(uri: string) {
-    const file = new URL(uri).pathname
+    const file = fileURLToPath(uri)
     return run(file, (client) =>
       client.connection
         .sendRequest("textDocument/documentSymbol", {
@@ -384,10 +393,11 @@ export namespace LSP {
   }
 
   export async function definition(input: { file: string; line: number; character: number }) {
-    return run(input.file, (client) =>
+    const file = normalizePathForUri(input.file)
+    return run(file, (client) =>
       client.connection
         .sendRequest("textDocument/definition", {
-          textDocument: { uri: pathToFileURL(input.file).href },
+          textDocument: { uri: pathToFileURL(file).href },
           position: { line: input.line, character: input.character },
         })
         .catch(() => null),
@@ -395,10 +405,11 @@ export namespace LSP {
   }
 
   export async function references(input: { file: string; line: number; character: number }) {
-    return run(input.file, (client) =>
+    const file = normalizePathForUri(input.file)
+    return run(file, (client) =>
       client.connection
         .sendRequest("textDocument/references", {
-          textDocument: { uri: pathToFileURL(input.file).href },
+          textDocument: { uri: pathToFileURL(file).href },
           position: { line: input.line, character: input.character },
           context: { includeDeclaration: true },
         })
@@ -407,10 +418,11 @@ export namespace LSP {
   }
 
   export async function implementation(input: { file: string; line: number; character: number }) {
-    return run(input.file, (client) =>
+    const file = normalizePathForUri(input.file)
+    return run(file, (client) =>
       client.connection
         .sendRequest("textDocument/implementation", {
-          textDocument: { uri: pathToFileURL(input.file).href },
+          textDocument: { uri: pathToFileURL(file).href },
           position: { line: input.line, character: input.character },
         })
         .catch(() => null),
@@ -418,10 +430,11 @@ export namespace LSP {
   }
 
   export async function prepareCallHierarchy(input: { file: string; line: number; character: number }) {
-    return run(input.file, (client) =>
+    const file = normalizePathForUri(input.file)
+    return run(file, (client) =>
       client.connection
         .sendRequest("textDocument/prepareCallHierarchy", {
-          textDocument: { uri: pathToFileURL(input.file).href },
+          textDocument: { uri: pathToFileURL(file).href },
           position: { line: input.line, character: input.character },
         })
         .catch(() => []),
@@ -429,10 +442,11 @@ export namespace LSP {
   }
 
   export async function incomingCalls(input: { file: string; line: number; character: number }) {
-    return run(input.file, async (client) => {
+    const file = normalizePathForUri(input.file)
+    return run(file, async (client) => {
       const items = (await client.connection
         .sendRequest("textDocument/prepareCallHierarchy", {
-          textDocument: { uri: pathToFileURL(input.file).href },
+          textDocument: { uri: pathToFileURL(file).href },
           position: { line: input.line, character: input.character },
         })
         .catch(() => [])) as any[]
@@ -442,10 +456,11 @@ export namespace LSP {
   }
 
   export async function outgoingCalls(input: { file: string; line: number; character: number }) {
-    return run(input.file, async (client) => {
+    const file = normalizePathForUri(input.file)
+    return run(file, async (client) => {
       const items = (await client.connection
         .sendRequest("textDocument/prepareCallHierarchy", {
-          textDocument: { uri: pathToFileURL(input.file).href },
+          textDocument: { uri: pathToFileURL(file).href },
           position: { line: input.line, character: input.character },
         })
         .catch(() => [])) as any[]
diff --git a/packages/opencode/src/tool/lsp.ts b/packages/opencode/src/tool/lsp.ts
index ca352280b2a..a14af89ee14 100644
--- a/packages/opencode/src/tool/lsp.ts
+++ b/packages/opencode/src/tool/lsp.ts
@@ -7,6 +7,20 @@ import { Instance } from "../project/instance"
 import { pathToFileURL } from "url"
 import { assertExternalDirectory } from "./external-directory"
 
+/**
+ * Normalize Windows path to ensure consistent drive letter casing.
+ * Windows paths are case-insensitive, but pathToFileURL preserves the case,
+ * which can cause URI mismatches when comparing URIs from different sources.
+ */
+function normalizePathForUri(filePath: string): string {
+  const resolved = path.resolve(filePath)
+  // Uppercase drive letter on Windows for consistent URI generation
+  if (process.platform === "win32" && /^[a-z]:/.test(resolved)) {
+    return resolved[0].toUpperCase() + resolved.slice(1)
+  }
+  return resolved
+}
+
 const operations = [
   "goToDefinition",
   "findReferences",
@@ -28,7 +42,8 @@ export const LspTool = Tool.define("lsp", {
     character: z.number().int().min(1).describe("The character offset (1-based, as shown in editors)"),
   }),
   execute: async (args, ctx) => {
-    const file = path.isAbsolute(args.filePath) ? args.filePath : path.join(Instance.directory, args.filePath)
+    const rawFile = path.isAbsolute(args.filePath) ? args.filePath : path.join(Instance.directory, args.filePath)
+    const file = normalizePathForUri(rawFile)
     await assertExternalDirectory(ctx, file)
 
     await ctx.ask({