diff --git a/src/hooks/hashline-read-enhancer/hook.ts b/src/hooks/hashline-read-enhancer/hook.ts
index d41b0447e..63a88035d 100644
--- a/src/hooks/hashline-read-enhancer/hook.ts
+++ b/src/hooks/hashline-read-enhancer/hook.ts
@@ -1,15 +1,21 @@
 import type { PluginInput } from "@opencode-ai/plugin"
 import { computeLineHash } from "../../tools/hashline-edit/hash-computation"
+import { toHashlineContent } from "../../tools/hashline-edit/diff-utils"
 
 interface HashlineReadEnhancerConfig {
   hashline_edit?: { enabled: boolean }
 }
 
 const READ_LINE_PATTERN = /^(\d+): (.*)$/
+const CONTENT_OPEN_TAG = "<content>"
+const CONTENT_CLOSE_TAG = "</content>"
 
 function isReadTool(toolName: string): boolean {
-  const lower = toolName.toLowerCase()
-  return lower === "read" || lower === "write"
+  return toolName.toLowerCase() === "read"
+}
+
+function isWriteTool(toolName: string): boolean {
+  return toolName.toLowerCase() === "write"
 }
 
 function shouldProcess(config: HashlineReadEnhancerConfig): boolean {
@@ -29,35 +35,73 @@ function transformLine(line: string): string {
   const lineNumber = parseInt(match[1], 10)
   const content = match[2]
   const hash = computeLineHash(lineNumber, content)
-  return `${lineNumber}:${hash}|${content}`
+  return `${lineNumber}#${hash}:${content}`
 }
 
 function transformOutput(output: string): string {
   if (!output) {
     return output
   }
-  if (!isTextFile(output)) {
+
+  const lines = output.split("\n")
+  const contentStart = lines.indexOf(CONTENT_OPEN_TAG)
+  const contentEnd = lines.indexOf(CONTENT_CLOSE_TAG)
+
+  if (contentStart === -1 || contentEnd === -1 || contentEnd <= contentStart + 1) {
     return output
   }
-  const lines = output.split("\n")
+
+  const fileLines = lines.slice(contentStart + 1, contentEnd)
+  if (!isTextFile(fileLines[0] ?? "")) {
+    return output
+  }
+
   const result: string[] = []
-  for (const line of lines) {
+  for (const line of fileLines) {
     if (!READ_LINE_PATTERN.test(line)) {
-      result.push(line)
-      result.push(...lines.slice(result.length))
+      result.push(...fileLines.slice(result.length))
       break
     }
     result.push(transformLine(line))
   }
-  return result.join("\n")
+
+  return [...lines.slice(0, contentStart + 1), ...result, ...lines.slice(contentEnd)].join("\n")
 }
 
-function transformWriteOutput(output: string): string {
-  if (!output) {
-    return output
+function extractFilePath(metadata: unknown): string | undefined {
+  if (!metadata || typeof metadata !== "object") {
+    return undefined
   }
-  const lines = output.split("\n")
-  return lines.map((line) => (READ_LINE_PATTERN.test(line) ? transformLine(line) : line)).join("\n")
+
+  const objectMeta = metadata as Record<string, unknown>
+  const candidates = [objectMeta.filepath, objectMeta.filePath, objectMeta.path, objectMeta.file]
+  for (const candidate of candidates) {
+    if (typeof candidate === "string" && candidate.length > 0) {
+      return candidate
+    }
+  }
+
+  return undefined
+}
+
+async function appendWriteHashlineOutput(output: { output: string; metadata: unknown }): Promise<void> {
+  if (output.output.includes("Updated file (LINE#ID:content):")) {
+    return
+  }
+
+  const filePath = extractFilePath(output.metadata)
+  if (!filePath) {
+    return
+  }
+
+  const file = Bun.file(filePath)
+  if (!(await file.exists())) {
+    return
+  }
+
+  const content = await file.text()
+  const hashlined = toHashlineContent(content)
+  output.output = `${output.output}\n\nUpdated file (LINE#ID:content):\n${hashlined}`
 }
 
 export function createHashlineReadEnhancerHook(
@@ -70,6 +114,9 @@ export function createHashlineReadEnhancerHook(
       output: { title: string; output: string; metadata: unknown }
     ) => {
       if (!isReadTool(input.tool)) {
+        if (isWriteTool(input.tool) && typeof output.output === "string" && shouldProcess(config)) {
+          await appendWriteHashlineOutput(output)
+        }
         return
       }
       if (typeof output.output !== "string") {
@@ -78,7 +125,7 @@ export function createHashlineReadEnhancerHook(
       if (!shouldProcess(config)) {
         return
       }
-      output.output = input.tool.toLowerCase() === "write" ? transformWriteOutput(output.output) : transformOutput(output.output)
+      output.output = transformOutput(output.output)
     },
   }
 }
diff --git a/src/hooks/hashline-read-enhancer/index.test.ts b/src/hooks/hashline-read-enhancer/index.test.ts
index 1cd713bc5..7486132d5 100644
--- a/src/hooks/hashline-read-enhancer/index.test.ts
+++ b/src/hooks/hashline-read-enhancer/index.test.ts
@@ -1,405 +1,93 @@
-import { describe, it, expect, beforeEach } from "bun:test"
-import { createHashlineReadEnhancerHook } from "./hook"
-import { computeLineHash } from "../../tools/hashline-edit/hash-computation"
-import { validateLineRef } from "../../tools/hashline-edit/validation"
+import { describe, it, expect } from "bun:test"
 import type { PluginInput } from "@opencode-ai/plugin"
+import { createHashlineReadEnhancerHook } from "./hook"
+import * as fs from "node:fs"
+import * as os from "node:os"
+import * as path from "node:path"
 
-//#given - Test setup helpers
-function createMockContext(): PluginInput {
+function mockCtx(): PluginInput {
   return {
-    client: {} as unknown as PluginInput["client"],
+    client: {} as PluginInput["client"],
     directory: "/test",
+    project: "/test" as unknown as PluginInput["project"],
+    worktree: "/test",
+    serverUrl: "http://localhost" as unknown as PluginInput["serverUrl"],
+    $: {} as PluginInput["$"],
   }
 }
 
-interface TestConfig {
-  hashline_edit?: { enabled: boolean }
-}
+describe("hashline-read-enhancer", () => {
+  it("hashifies only file content lines in read output", async () => {
+    //#given
+    const hook = createHashlineReadEnhancerHook(mockCtx(), { hashline_edit: { enabled: true } })
+    const input = { tool: "read", sessionID: "s", callID: "c" }
+    const output = {
+      title: "demo.ts",
+      output: [
+        "<path>/tmp/demo.ts</path>",
+        "<type>file</type>",
+        "<content>",
+        "1: const x = 1",
+        "2: const y = 2",
+        "",
+        "(End of file - total 2 lines)",
+        "</content>",
+        "",
+        "<system-reminder>",
+        "1: keep this unchanged",
+        "</system-reminder>",
+      ].join("\n"),
+      metadata: {},
+    }
 
-function createMockConfig(enabled: boolean): TestConfig {
-  return {
-    hashline_edit: { enabled },
-  }
-}
+    //#when
+    await hook["tool.execute.after"](input, output)
 
-describe("createHashlineReadEnhancerHook", () => {
-  let mockCtx: PluginInput
-  const sessionID = "test-session-123"
-
-  beforeEach(() => {
-    mockCtx = createMockContext()
+    //#then
+    const lines = output.output.split("\n")
+    expect(lines[3]).toMatch(/^1#[ZPMQVRWSNKTXJBYH]{2}:const x = 1$/)
+    expect(lines[4]).toMatch(/^2#[ZPMQVRWSNKTXJBYH]{2}:const y = 2$/)
+    expect(lines[10]).toBe("1: keep this unchanged")
   })
 
-  describe("tool name matching", () => {
-    it("should process 'read' tool (lowercase)", async () => {
-      //#given
-      const hook = createHashlineReadEnhancerHook(mockCtx, createMockConfig(true))
-      const input = { tool: "read", sessionID, callID: "call-1" }
-      const output = { title: "Read", output: "1: hello\n2: world", metadata: {} }
+  it("appends LINE#ID output for write tool using metadata filepath", async () => {
+    //#given
+    const hook = createHashlineReadEnhancerHook(mockCtx(), { hashline_edit: { enabled: true } })
+    const tempDir = fs.mkdtempSync(path.join(os.tmpdir(), "hashline-write-"))
+    const filePath = path.join(tempDir, "demo.ts")
+    fs.writeFileSync(filePath, "const x = 1\nconst y = 2")
+    const input = { tool: "write", sessionID: "s", callID: "c" }
+    const output = {
+      title: "write",
+      output: "Wrote file successfully.",
+      metadata: { filepath: filePath },
+    }
 
-      //#when
-      await hook["tool.execute.after"](input, output)
+    //#when
+    await hook["tool.execute.after"](input, output)
 
-      //#then
-      expect(output.output).toContain("1:")
-      expect(output.output).toContain("|")
-    })
+    //#then
+    expect(output.output).toContain("Updated file (LINE#ID:content):")
+    expect(output.output).toMatch(/1#[ZPMQVRWSNKTXJBYH]{2}:const x = 1/)
+    expect(output.output).toMatch(/2#[ZPMQVRWSNKTXJBYH]{2}:const y = 2/)
 
-    it("should process 'Read' tool (mixed case)", async () => {
-      //#given
-      const hook = createHashlineReadEnhancerHook(mockCtx, createMockConfig(true))
-      const input = { tool: "Read", sessionID, callID: "call-1" }
-      const output = { title: "Read", output: "1: hello\n2: world", metadata: {} }
-
-      //#when
-      await hook["tool.execute.after"](input, output)
-
-      //#then
-      expect(output.output).toContain("|")
-    })
-
-    it("should process 'READ' tool (uppercase)", async () => {
-      //#given
-      const hook = createHashlineReadEnhancerHook(mockCtx, createMockConfig(true))
-      const input = { tool: "READ", sessionID, callID: "call-1" }
-      const output = { title: "Read", output: "1: hello\n2: world", metadata: {} }
-
-      //#when
-      await hook["tool.execute.after"](input, output)
-
-      //#then
-      expect(output.output).toContain("|")
-    })
-
-
-    it("should process 'write' tool (lowercase)", async () => {
-      //#given
-      const hook = createHashlineReadEnhancerHook(mockCtx, createMockConfig(true))
-      const input = { tool: "write", sessionID, callID: "call-1" }
-      const output = { title: "Write", output: "1: hello\n2: world", metadata: {} }
-
-      //#when
-      await hook["tool.execute.after"](input, output)
-
-      //#then
-      expect(output.output).toContain("|")
-    })
-
-    it("should process 'Write' tool (mixed case)", async () => {
-      //#given
-      const hook = createHashlineReadEnhancerHook(mockCtx, createMockConfig(true))
-      const input = { tool: "Write", sessionID, callID: "call-1" }
-      const output = { title: "Write", output: "1: hello\n2: world", metadata: {} }
-
-      //#when
-      await hook["tool.execute.after"](input, output)
-
-      //#then
-      expect(output.output).toContain("|")
-    })
-
-    it("should transform write tool output to LINE:HASH|content format", async () => {
-      //#given
-      const hook = createHashlineReadEnhancerHook(mockCtx, createMockConfig(true))
-      const input = { tool: "write", sessionID, callID: "call-1" }
-      const output = { title: "Write", output: "1: const x = 1\n2: const y = 2", metadata: {} }
-
-      //#when
-      await hook["tool.execute.after"](input, output)
-
-      //#then
-      const lines = output.output.split("\n")
-      expect(lines[0]).toMatch(/^1:[a-f0-9]{2}\|const x = 1$/)
-      expect(lines[1]).toMatch(/^2:[a-f0-9]{2}\|const y = 2$/)
-    })
-
-    it("should transform numbered write lines even when header lines come first", async () => {
-      //#given
-      const hook = createHashlineReadEnhancerHook(mockCtx, createMockConfig(true))
-      const input = { tool: "write", sessionID, callID: "call-1" }
-      const output = {
-        title: "Write",
-        output: ["# Wrote /tmp/demo-edit.txt", "1: This is line one", "2: This is line two"].join("\n"),
-        metadata: {},
-      }
-
-      //#when
-      await hook["tool.execute.after"](input, output)
-
-      //#then
-      const lines = output.output.split("\n")
-      expect(lines[0]).toBe("# Wrote /tmp/demo-edit.txt")
-      expect(lines[1]).toMatch(/^1:[a-f0-9]{2}\|This is line one$/)
-      expect(lines[2]).toMatch(/^2:[a-f0-9]{2}\|This is line two$/)
-    })
-
-    it("should skip non-read tools", async () => {
-      //#given
-      const hook = createHashlineReadEnhancerHook(mockCtx, createMockConfig(true))
-      const input = { tool: "edit", sessionID, callID: "call-1" }
-      const originalOutput = "1: hello\n2: world"
-      const output = { title: "Edit", output: originalOutput, metadata: {} }
-
-      //#when
-      await hook["tool.execute.after"](input, output)
-
-      //#then
-      expect(output.output).toBe(originalOutput)
-    })
+    fs.rmSync(tempDir, { recursive: true, force: true })
   })
 
-  describe("config flag check", () => {
-    it("should skip when hashline_edit is disabled", async () => {
-      //#given
-      const hook = createHashlineReadEnhancerHook(mockCtx, createMockConfig(false))
-      const input = { tool: "read", sessionID, callID: "call-1" }
-      const originalOutput = "1: hello\n2: world"
-      const output = { title: "Read", output: originalOutput, metadata: {} }
+  it("skips when feature is disabled", async () => {
+    //#given
+    const hook = createHashlineReadEnhancerHook(mockCtx(), { hashline_edit: { enabled: false } })
+    const input = { tool: "read", sessionID: "s", callID: "c" }
+    const output = {
+      title: "demo.ts",
+      output: "<content>\n1: const x = 1\n</content>",
+      metadata: {},
+    }
 
-      //#when
-      await hook["tool.execute.after"](input, output)
+    //#when
+    await hook["tool.execute.after"](input, output)
 
-      //#then
-      expect(output.output).toBe(originalOutput)
-    })
-
-    it("should skip when hashline_edit config is missing", async () => {
-      //#given
-      const hook = createHashlineReadEnhancerHook(mockCtx, {})
-      const input = { tool: "read", sessionID, callID: "call-1" }
-      const originalOutput = "1: hello\n2: world"
-      const output = { title: "Read", output: originalOutput, metadata: {} }
-
-      //#when
-      await hook["tool.execute.after"](input, output)
-
-      //#then
-      expect(output.output).toBe(originalOutput)
-    })
-  })
-
-  describe("output transformation", () => {
-    it("should transform 'N: content' format to 'N:HASH|content'", async () => {
-      //#given
-      const hook = createHashlineReadEnhancerHook(mockCtx, createMockConfig(true))
-      const input = { tool: "read", sessionID, callID: "call-1" }
-      const output = { title: "Read", output: "1: function hello() {\n2:   console.log('world')\n3: }", metadata: {} }
-
-      //#when
-      await hook["tool.execute.after"](input, output)
-
-      //#then
-      const lines = output.output.split("\n")
-      expect(lines[0]).toMatch(/^1:[a-f0-9]{2}\|function hello\(\) \{$/)
-      expect(lines[1]).toMatch(/^2:[a-f0-9]{2}\|  console\.log\('world'\)$/)
-      expect(lines[2]).toMatch(/^3:[a-f0-9]{2}\|\}$/)
-    })
-
-    it("should handle empty output", async () => {
-      //#given
-      const hook = createHashlineReadEnhancerHook(mockCtx, createMockConfig(true))
-      const input = { tool: "read", sessionID, callID: "call-1" }
-      const output = { title: "Read", output: "", metadata: {} }
-
-      //#when
-      await hook["tool.execute.after"](input, output)
-
-      //#then
-      expect(output.output).toBe("")
-    })
-
-    it("should handle single line", async () => {
-      //#given
-      const hook = createHashlineReadEnhancerHook(mockCtx, createMockConfig(true))
-      const input = { tool: "read", sessionID, callID: "call-1" }
-      const output = { title: "Read", output: "1: const x = 1", metadata: {} }
-
-      //#when
-      await hook["tool.execute.after"](input, output)
-
-      //#then
-      expect(output.output).toMatch(/^1:[a-f0-9]{2}\|const x = 1$/)
-    })
-  })
-
-  describe("binary file detection", () => {
-    it("should skip binary files (no line number prefix)", async () => {
-      //#given
-      const hook = createHashlineReadEnhancerHook(mockCtx, createMockConfig(true))
-      const input = { tool: "read", sessionID, callID: "call-1" }
-      const originalOutput = "PNG\x89\x50\x4E\x47\x0D\x0A\x1A\x0A"
-      const output = { title: "Read", output: originalOutput, metadata: {} }
-
-      //#when
-      await hook["tool.execute.after"](input, output)
-
-      //#then
-      expect(output.output).toBe(originalOutput)
-    })
-
-    it("should skip if first line doesn't match pattern", async () => {
-      //#given
-      const hook = createHashlineReadEnhancerHook(mockCtx, createMockConfig(true))
-      const input = { tool: "read", sessionID, callID: "call-1" }
-      const originalOutput = "some binary data\nmore data"
-      const output = { title: "Read", output: originalOutput, metadata: {} }
-
-      //#when
-      await hook["tool.execute.after"](input, output)
-
-      //#then
-      expect(output.output).toBe(originalOutput)
-    })
-
-    it("should process if first line matches 'N: ' pattern", async () => {
-      //#given
-      const hook = createHashlineReadEnhancerHook(mockCtx, createMockConfig(true))
-      const input = { tool: "read", sessionID, callID: "call-1" }
-      const output = { title: "Read", output: "1: valid line\n2: another line", metadata: {} }
-
-      //#when
-      await hook["tool.execute.after"](input, output)
-
-      //#then
-      expect(output.output).toContain("|")
-    })
-  })
-
-  describe("hash consistency with Edit tool validation", () => {
-    it("hash in Read output matches what validateLineRef expects for the same file content", async () => {
-      //#given
-      const hook = createHashlineReadEnhancerHook(mockCtx, createMockConfig(true))
-      const input = { tool: "read", sessionID, callID: "call-1" }
-      const fileLines = ["import { foo } from './bar'", "  const x = 1", "", "export default x"]
-      const readOutput = fileLines.map((line, i) => `${i + 1}: ${line}`).join("\n")
-      const output = { title: "Read", output: readOutput, metadata: {} }
-
-      //#when
-      await hook["tool.execute.after"](input, output)
-
-      //#then - each hash in Read output must satisfy validateLineRef
-      const transformedLines = output.output.split("\n")
-      for (let i = 0; i < fileLines.length; i++) {
-        const lineNum = i + 1
-        const expectedHash = computeLineHash(lineNum, fileLines[i])
-        expect(transformedLines[i]).toBe(`${lineNum}:${expectedHash}|${fileLines[i]}`)
-        // Must not throw when used with validateLineRef
-        expect(() => validateLineRef(fileLines, `${lineNum}:${expectedHash}`)).not.toThrow()
-      }
-    })
-  })
-
-  describe("injected content isolation", () => {
-    it("should NOT hashify lines appended by other hooks that happen to match the numbered pattern", async () => {
-      //#given - file content followed by injected README with numbered items
-      const hook = createHashlineReadEnhancerHook(mockCtx, createMockConfig(true))
-      const input = { tool: "read", sessionID, callID: "call-1" }
-      const output = {
-        title: "Read",
-        output: ["1: const x = 1", "2: const y = 2", "[Project README]", "1: First item", "2: Second item"].join("\n"),
-        metadata: {},
-      }
-
-      //#when
-      await hook["tool.execute.after"](input, output)
-
-      //#then - only original file content gets hashified
-      const lines = output.output.split("\n")
-      expect(lines[0]).toMatch(/^1:[a-f0-9]{2}\|const x = 1$/)
-      expect(lines[1]).toMatch(/^2:[a-f0-9]{2}\|const y = 2$/)
-      expect(lines[2]).toBe("[Project README]")
-      expect(lines[3]).toBe("1: First item")
-      expect(lines[4]).toBe("2: Second item")
-    })
-
-    it("should NOT hashify Read tool footer messages after file content", async () => {
-      //#given
-      const hook = createHashlineReadEnhancerHook(mockCtx, createMockConfig(true))
-      const input = { tool: "read", sessionID, callID: "call-1" }
-      const output = {
-        title: "Read",
-        output: ["1: const x = 1", "2: const y = 2", "", "(File has more lines. Use 'offset' parameter to read beyond line 2)"].join("\n"),
-        metadata: {},
-      }
-
-      //#when
-      await hook["tool.execute.after"](input, output)
-
-      //#then - footer passes through unchanged
-      const lines = output.output.split("\n")
-      expect(lines[0]).toMatch(/^1:[a-f0-9]{2}\|const x = 1$/)
-      expect(lines[1]).toMatch(/^2:[a-f0-9]{2}\|const y = 2$/)
-      expect(lines[2]).toBe("")
-      expect(lines[3]).toBe("(File has more lines. Use 'offset' parameter to read beyond line 2)")
-    })
-
-    it("should NOT hashify system reminder content appended after file content", async () => {
-      //#given - other hooks append system reminders to output
-      const hook = createHashlineReadEnhancerHook(mockCtx, createMockConfig(true))
-      const input = { tool: "read", sessionID, callID: "call-1" }
-      const output = {
-        title: "Read",
-        output: ["1: export function hello() {", "2:   return 42", "3: }", "", "[System Reminder]", "1: Do not forget X", "2: Always do Y"].join("\n"),
-        metadata: {},
-      }
-
-      //#when
-      await hook["tool.execute.after"](input, output)
-
-      //#then
-      const lines = output.output.split("\n")
-      expect(lines[0]).toMatch(/^1:[a-f0-9]{2}\|export function hello\(\) \{$/)
-      expect(lines[1]).toMatch(/^2:[a-f0-9]{2}\|  return 42$/)
-      expect(lines[2]).toMatch(/^3:[a-f0-9]{2}\|}$/)
-      expect(lines[3]).toBe("")
-      expect(lines[4]).toBe("[System Reminder]")
-      expect(lines[5]).toBe("1: Do not forget X")
-      expect(lines[6]).toBe("2: Always do Y")
-    })
-  })
-
-  describe("edge cases", () => {
-    it("should handle non-string output gracefully", async () => {
-      //#given
-      const hook = createHashlineReadEnhancerHook(mockCtx, createMockConfig(true))
-      const input = { tool: "read", sessionID, callID: "call-1" }
-      const output = { title: "Read", output: null as unknown as string, metadata: {} }
-
-      //#when - should not throw
-      await hook["tool.execute.after"](input, output)
-
-      //#then
-      expect(output.output).toBeNull()
-    })
-
-    it("should handle lines with no content after colon", async () => {
-      //#given
-      const hook = createHashlineReadEnhancerHook(mockCtx, createMockConfig(true))
-      const input = { tool: "read", sessionID, callID: "call-1" }
-      const output = { title: "Read", output: "1: hello\n2: \n3: world", metadata: {} }
-
-      //#when
-      await hook["tool.execute.after"](input, output)
-
-      //#then
-      const lines = output.output.split("\n")
-      expect(lines[0]).toMatch(/^1:[a-f0-9]{2}\|hello$/)
-      expect(lines[1]).toMatch(/^2:[a-f0-9]{2}\|$/)
-      expect(lines[2]).toMatch(/^3:[a-f0-9]{2}\|world$/)
-    })
-
-    it("should handle very long lines", async () => {
-      //#given
-      const longContent = "a".repeat(1000)
-      const hook = createHashlineReadEnhancerHook(mockCtx, createMockConfig(true))
-      const input = { tool: "read", sessionID, callID: "call-1" }
-      const output = { title: "Read", output: `1: ${longContent}`, metadata: {} }
-
-      //#when
-      await hook["tool.execute.after"](input, output)
-
-      //#then
-      expect(output.output).toMatch(/^1:[a-f0-9]{2}\|a+$/)
-    })
+    //#then
+    expect(output.output).toBe("<content>\n1: const x = 1\n</content>")
   })
 })
diff --git a/src/tools/hashline-edit/edit-operations.test.ts b/src/tools/hashline-edit/edit-operations.test.ts
index 754dff41c..45abaa4c8 100644
--- a/src/tools/hashline-edit/edit-operations.test.ts
+++ b/src/tools/hashline-edit/edit-operations.test.ts
@@ -1,263 +1,64 @@
 import { describe, expect, it } from "bun:test"
-import {
-  applyHashlineEdits,
-  applyInsertAfter,
-  applyReplace,
-  applyReplaceLines,
-  applySetLine,
-} from "./edit-operations"
+import { applyHashlineEdits, applyInsertAfter, applyReplace, applyReplaceLines, applySetLine } from "./edit-operations"
 import { computeLineHash } from "./hash-computation"
-import type { HashlineEdit, InsertAfter, Replace, ReplaceLines, SetLine } from "./types"
+import type { HashlineEdit } from "./types"
 
-describe("applySetLine", () => {
-  function anchorFor(lines: string[], line: number): string {
-    return `${line}:${computeLineHash(line, lines[line - 1])}`
-  }
+function anchorFor(lines: string[], line: number): string {
+  return `${line}#${computeLineHash(line, lines[line - 1])}`
+}
 
-  it("replaces a single line at the specified anchor", () => {
+describe("hashline edit operations", () => {
+  it("applies set_line with LINE#ID anchor", () => {
     //#given
     const lines = ["line 1", "line 2", "line 3"]
-    const anchor = anchorFor(lines, 2)
 
     //#when
-    const result = applySetLine(lines, anchor, "new line 2")
+    const result = applySetLine(lines, anchorFor(lines, 2), "new line 2")
 
     //#then
     expect(result).toEqual(["line 1", "new line 2", "line 3"])
   })
 
-  it("handles newline escapes in replacement text", () => {
+  it("applies replace_lines with LINE#ID anchors", () => {
     //#given
-    const lines = ["line 1", "line 2", "line 3"]
-    const anchor = anchorFor(lines, 2)
+    const lines = ["line 1", "line 2", "line 3", "line 4"]
 
     //#when
-    const result = applySetLine(lines, anchor, "new\\nline")
+    const result = applyReplaceLines(lines, anchorFor(lines, 2), anchorFor(lines, 3), "replaced")
 
     //#then
-    expect(result).toEqual(["line 1", "new\nline", "line 3"])
+    expect(result).toEqual(["line 1", "replaced", "line 4"])
   })
 
-  it("throws on hash mismatch", () => {
+  it("applies insert_after with LINE#ID anchor", () => {
     //#given
     const lines = ["line 1", "line 2", "line 3"]
-    const anchor = "2:ff" // wrong hash
-
-    //#when / #then
-    expect(() => applySetLine(lines, anchor, "new")).toThrow("Hash mismatch")
-  })
-
-  it("throws on out of bounds line", () => {
-    //#given
-    const lines = ["line 1", "line 2"]
-    const anchor = "5:00"
-
-    //#when / #then
-    expect(() => applySetLine(lines, anchor, "new")).toThrow("out of bounds")
-  })
-})
-
-describe("applyReplaceLines", () => {
-  it("replaces a range of lines", () => {
-    //#given
-    const lines = ["line 1", "line 2", "line 3", "line 4", "line 5"]
-    const startAnchor = `${2}:${computeLineHash(2, lines[1])}`
-    const endAnchor = `${4}:${computeLineHash(4, lines[3])}`
 
     //#when
-    const result = applyReplaceLines(lines, startAnchor, endAnchor, "replacement")
-
-    //#then
-    expect(result).toEqual(["line 1", "replacement", "line 5"])
-  })
-
-  it("handles newline escapes in replacement text", () => {
-    //#given
-    const lines = ["line 1", "line 2", "line 3"]
-    const startAnchor = `${2}:${computeLineHash(2, lines[1])}`
-    const endAnchor = `${2}:${computeLineHash(2, lines[1])}`
-
-    //#when
-    const result = applyReplaceLines(lines, startAnchor, endAnchor, "a\\nb")
-
-    //#then
-    expect(result).toEqual(["line 1", "a", "b", "line 3"])
-  })
-
-  it("throws on start hash mismatch", () => {
-    //#given
-    const lines = ["line 1", "line 2", "line 3"]
-    const startAnchor = "2:ff"
-    const endAnchor = `${3}:${computeLineHash(3, lines[2])}`
-
-    //#when / #then
-    expect(() => applyReplaceLines(lines, startAnchor, endAnchor, "new")).toThrow(
-      "Hash mismatch"
-    )
-  })
-
-  it("throws on end hash mismatch", () => {
-    //#given
-    const lines = ["line 1", "line 2", "line 3"]
-    const startAnchor = `${2}:${computeLineHash(2, lines[1])}`
-    const endAnchor = "3:ff"
-
-    //#when / #then
-    expect(() => applyReplaceLines(lines, startAnchor, endAnchor, "new")).toThrow(
-      "Hash mismatch"
-    )
-  })
-
-  it("throws when start > end", () => {
-    //#given
-    const lines = ["line 1", "line 2", "line 3"]
-    const startAnchor = `${3}:${computeLineHash(3, lines[2])}`
-    const endAnchor = `${2}:${computeLineHash(2, lines[1])}`
-
-    //#when / #then
-    expect(() => applyReplaceLines(lines, startAnchor, endAnchor, "new")).toThrow(
-      "start line 3 cannot be greater than end line 2"
-    )
-  })
-})
-
-describe("applyInsertAfter", () => {
-  it("inserts text after the specified line", () => {
-    //#given
-    const lines = ["line 1", "line 2", "line 3"]
-    const anchor = `${2}:${computeLineHash(2, lines[1])}`
-
-    //#when
-    const result = applyInsertAfter(lines, anchor, "inserted")
+    const result = applyInsertAfter(lines, anchorFor(lines, 2), "inserted")
 
     //#then
     expect(result).toEqual(["line 1", "line 2", "inserted", "line 3"])
   })
 
-  it("handles newline escapes to insert multiple lines", () => {
+  it("applies replace operation", () => {
     //#given
-    const lines = ["line 1", "line 2", "line 3"]
-    const anchor = `${2}:${computeLineHash(2, lines[1])}`
+    const content = "hello world foo"
 
     //#when
-    const result = applyInsertAfter(lines, anchor, "a\\nb\\nc")
+    const result = applyReplace(content, "world", "universe")
 
     //#then
-    expect(result).toEqual(["line 1", "line 2", "a", "b", "c", "line 3"])
+    expect(result).toEqual("hello universe foo")
   })
 
-  it("inserts at end when anchor is last line", () => {
-    //#given
-    const lines = ["line 1", "line 2"]
-    const anchor = `${2}:${computeLineHash(2, lines[1])}`
-
-    //#when
-    const result = applyInsertAfter(lines, anchor, "inserted")
-
-    //#then
-    expect(result).toEqual(["line 1", "line 2", "inserted"])
-  })
-
-  it("throws on hash mismatch", () => {
-    //#given
-    const lines = ["line 1", "line 2"]
-    const anchor = "2:ff"
-
-    //#when / #then
-    expect(() => applyInsertAfter(lines, anchor, "new")).toThrow("Hash mismatch")
-  })
-})
-
-describe("applyReplace", () => {
-  it("replaces exact text match", () => {
-    //#given
-    const content = "hello world foo bar"
-    const oldText = "world"
-    const newText = "universe"
-
-    //#when
-    const result = applyReplace(content, oldText, newText)
-
-    //#then
-    expect(result).toEqual("hello universe foo bar")
-  })
-
-  it("replaces all occurrences", () => {
-    //#given
-    const content = "foo bar foo baz foo"
-    const oldText = "foo"
-    const newText = "qux"
-
-    //#when
-    const result = applyReplace(content, oldText, newText)
-
-    //#then
-    expect(result).toEqual("qux bar qux baz qux")
-  })
-
-  it("handles newline escapes in newText", () => {
-    //#given
-    const content = "hello world"
-    const oldText = "world"
-    const newText = "new\\nline"
-
-    //#when
-    const result = applyReplace(content, oldText, newText)
-
-    //#then
-    expect(result).toEqual("hello new\nline")
-  })
-
-  it("throws when oldText not found", () => {
-    //#given
-    const content = "hello world"
-    const oldText = "notfound"
-    const newText = "replacement"
-
-    //#when / #then
-    expect(() => applyReplace(content, oldText, newText)).toThrow("Text not found")
-  })
-})
-
-describe("applyHashlineEdits", () => {
-  it("applies single set_line edit", () => {
+  it("applies mixed edits in one pass", () => {
     //#given
     const content = "line 1\nline 2\nline 3"
-    const line2Hash = computeLineHash(2, "line 2")
-    const edits: SetLine[] = [{ type: "set_line", line: `2:${line2Hash}`, text: "new line 2" }]
-
-    //#when
-    const result = applyHashlineEdits(content, edits)
-
-    //#then
-    expect(result).toEqual("line 1\nnew line 2\nline 3")
-  })
-
-  it("applies multiple edits bottom-up (descending line order)", () => {
-    //#given
-    const content = "line 1\nline 2\nline 3\nline 4\nline 5"
-    const line2Hash = computeLineHash(2, "line 2")
-    const line4Hash = computeLineHash(4, "line 4")
-    const edits: SetLine[] = [
-      { type: "set_line", line: `2:${line2Hash}`, text: "new 2" },
-      { type: "set_line", line: `4:${line4Hash}`, text: "new 4" },
-    ]
-
-    //#when
-    const result = applyHashlineEdits(content, edits)
-
-    //#then
-    expect(result).toEqual("line 1\nnew 2\nline 3\nnew 4\nline 5")
-  })
-
-  it("applies mixed edit types", () => {
-    //#given
-    const content = "line 1\nline 2\nline 3"
-    const line1Hash = computeLineHash(1, "line 1")
-    const line3Hash = computeLineHash(3, "line 3")
+    const lines = content.split("\n")
     const edits: HashlineEdit[] = [
-      { type: "insert_after", line: `1:${line1Hash}`, text: "inserted" },
-      { type: "set_line", line: `3:${line3Hash}`, text: "modified" },
+      { type: "insert_after", line: anchorFor(lines, 1), text: "inserted" },
+      { type: "set_line", line: anchorFor(lines, 3), text: "modified" },
     ]
 
     //#when
@@ -267,69 +68,63 @@ describe("applyHashlineEdits", () => {
     expect(result).toEqual("line 1\ninserted\nline 2\nmodified")
   })
 
-  it("applies replace_lines edit", () => {
+  it("keeps literal backslash-n in plain string text", () => {
     //#given
-    const content = "line 1\nline 2\nline 3\nline 4"
-    const line2Hash = computeLineHash(2, "line 2")
-    const line3Hash = computeLineHash(3, "line 3")
-    const edits: ReplaceLines[] = [
-      { type: "replace_lines", start_line: `2:${line2Hash}`, end_line: `3:${line3Hash}`, text: "replaced" },
-    ]
+    const lines = ["line 1", "line 2", "line 3"]
 
     //#when
-    const result = applyHashlineEdits(content, edits)
+    const result = applySetLine(lines, anchorFor(lines, 2), "join(\\n)")
 
     //#then
-    expect(result).toEqual("line 1\nreplaced\nline 4")
+    expect(result).toEqual(["line 1", "join(\\n)", "line 3"])
   })
 
-  it("applies replace fallback edit", () => {
+  it("strips copied hashline prefixes from multiline text", () => {
     //#given
-    const content = "hello world foo"
-    const edits: Replace[] = [{ type: "replace", old_text: "world", new_text: "universe" }]
+    const lines = ["line 1", "line 2", "line 3"]
 
     //#when
-    const result = applyHashlineEdits(content, edits)
+    const result = applySetLine(lines, anchorFor(lines, 2), "1#VK:first\n2#NP:second")
 
     //#then
-    expect(result).toEqual("hello universe foo")
+    expect(result).toEqual(["line 1", "first", "second", "line 3"])
   })
 
-  it("handles empty edits array", () => {
+  it("autocorrects anchor echo for insert_after payload", () => {
     //#given
-    const content = "line 1\nline 2"
-    const edits: HashlineEdit[] = []
+    const lines = ["line 1", "line 2"]
 
     //#when
-    const result = applyHashlineEdits(content, edits)
+    const result = applyInsertAfter(lines, anchorFor(lines, 1), ["line 1", "inserted"])
 
     //#then
-    expect(result).toEqual("line 1\nline 2")
+    expect(result).toEqual(["line 1", "inserted", "line 2"])
   })
 
-  it("throws on hash mismatch with descriptive error", () => {
+  it("restores indentation for paired single-line replacement", () => {
     //#given
-    const content = "line 1\nline 2\nline 3"
-    const edits: SetLine[] = [{ type: "set_line", line: "2:ff", text: "new" }]
-
-    //#when / #then
-    expect(() => applyHashlineEdits(content, edits)).toThrow("Hash mismatch")
-  })
-
-  it("correctly handles index shifting with multiple edits", () => {
-    //#given
-    const content = "a\nb\nc\nd\ne"
-    const line2Hash = computeLineHash(2, "b")
-    const line4Hash = computeLineHash(4, "d")
-    const edits: InsertAfter[] = [
-      { type: "insert_after", line: `2:${line2Hash}`, text: "x" },
-      { type: "insert_after", line: `4:${line4Hash}`, text: "y" },
-    ]
+    const lines = ["if (x) {", "  return 1", "}"]
 
     //#when
-    const result = applyHashlineEdits(content, edits)
+    const result = applySetLine(lines, anchorFor(lines, 2), "return 2")
 
     //#then
-    expect(result).toEqual("a\nb\nx\nc\nd\ny\ne")
+    expect(result).toEqual(["if (x) {", "  return 2", "}"])
+  })
+
+  it("strips boundary echo around replace_lines content", () => {
+    //#given
+    const lines = ["before", "old 1", "old 2", "after"]
+
+    //#when
+    const result = applyReplaceLines(
+      lines,
+      anchorFor(lines, 2),
+      anchorFor(lines, 3),
+      ["before", "new 1", "new 2", "after"]
+    )
+
+    //#then
+    expect(result).toEqual(["before", "new 1", "new 2", "after"])
   })
 })
diff --git a/src/tools/hashline-edit/edit-operations.ts b/src/tools/hashline-edit/edit-operations.ts
index 7a6340db6..9929e9acd 100644
--- a/src/tools/hashline-edit/edit-operations.ts
+++ b/src/tools/hashline-edit/edit-operations.ts
@@ -1,15 +1,106 @@
-import { parseLineRef, validateLineRef } from "./validation"
+import { parseLineRef, validateLineRef, validateLineRefs } from "./validation"
 import type { HashlineEdit } from "./types"
 
-function unescapeNewlines(text: string): string {
-  return text.replace(/\\n/g, "\n")
+const HASHLINE_PREFIX_RE = /^\s*(?:>>>|>>)?\s*\d+#[A-Z]{2}:/
+const DIFF_PLUS_RE = /^[+-](?![+-])/
+
+function stripLinePrefixes(lines: string[]): string[] {
+  let hashPrefixCount = 0
+  let diffPlusCount = 0
+  let nonEmpty = 0
+
+  for (const line of lines) {
+    if (line.length === 0) continue
+    nonEmpty += 1
+    if (HASHLINE_PREFIX_RE.test(line)) hashPrefixCount += 1
+    if (DIFF_PLUS_RE.test(line)) diffPlusCount += 1
+  }
+
+  if (nonEmpty === 0) {
+    return lines
+  }
+
+  const stripHash = hashPrefixCount > 0 && hashPrefixCount >= nonEmpty * 0.5
+  const stripPlus = !stripHash && diffPlusCount > 0 && diffPlusCount >= nonEmpty * 0.5
+
+  if (!stripHash && !stripPlus) {
+    return lines
+  }
+
+  return lines.map((line) => {
+    if (stripHash) return line.replace(HASHLINE_PREFIX_RE, "")
+    if (stripPlus) return line.replace(DIFF_PLUS_RE, "")
+    return line
+  })
 }
 
-export function applySetLine(lines: string[], anchor: string, newText: string): string[] {
+function equalsIgnoringWhitespace(a: string, b: string): boolean {
+  if (a === b) return true
+  return a.replace(/\s+/g, "") === b.replace(/\s+/g, "")
+}
+
+function leadingWhitespace(text: string): string {
+  const match = text.match(/^\s*/)
+  return match ? match[0] : ""
+}
+
+function restoreLeadingIndent(templateLine: string, line: string): string {
+  if (line.length === 0) return line
+  const templateIndent = leadingWhitespace(templateLine)
+  if (templateIndent.length === 0) return line
+  if (leadingWhitespace(line).length > 0) return line
+  return `${templateIndent}${line}`
+}
+
+function stripInsertAnchorEcho(anchorLine: string, newLines: string[]): string[] {
+  if (newLines.length <= 1) return newLines
+  if (equalsIgnoringWhitespace(newLines[0], anchorLine)) {
+    return newLines.slice(1)
+  }
+  return newLines
+}
+
+function stripRangeBoundaryEcho(
+  lines: string[],
+  startLine: number,
+  endLine: number,
+  newLines: string[]
+): string[] {
+  const replacedCount = endLine - startLine + 1
+  if (newLines.length <= 1 || newLines.length <= replacedCount) {
+    return newLines
+  }
+
+  let out = newLines
+  const beforeIdx = startLine - 2
+  if (beforeIdx >= 0 && equalsIgnoringWhitespace(out[0], lines[beforeIdx])) {
+    out = out.slice(1)
+  }
+
+  const afterIdx = endLine
+  if (afterIdx < lines.length && out.length > 0 && equalsIgnoringWhitespace(out[out.length - 1], lines[afterIdx])) {
+    out = out.slice(0, -1)
+  }
+
+  return out
+}
+
+function toNewLines(input: string | string[]): string[] {
+  if (Array.isArray(input)) {
+    return stripLinePrefixes(input)
+  }
+  return stripLinePrefixes(input.split("\n"))
+}
+
+export function applySetLine(lines: string[], anchor: string, newText: string | string[]): string[] {
   validateLineRef(lines, anchor)
   const { line } = parseLineRef(anchor)
   const result = [...lines]
-  result[line - 1] = unescapeNewlines(newText)
+  const replacement = toNewLines(newText).map((entry, idx) => {
+    if (idx !== 0) return entry
+    return restoreLeadingIndent(lines[line - 1], entry)
+  })
+  result.splice(line - 1, 1, ...replacement)
   return result
 }
 
@@ -17,7 +108,7 @@ export function applyReplaceLines(
   lines: string[],
   startAnchor: string,
   endAnchor: string,
-  newText: string
+  newText: string | string[]
 ): string[] {
   validateLineRef(lines, startAnchor)
   validateLineRef(lines, endAnchor)
@@ -32,25 +123,31 @@ export function applyReplaceLines(
   }
 
   const result = [...lines]
-  const newLines = unescapeNewlines(newText).split("\n")
+  const stripped = stripRangeBoundaryEcho(lines, startLine, endLine, toNewLines(newText))
+  const newLines = stripped.map((entry, idx) => {
+    const oldLine = lines[startLine - 1 + idx]
+    if (!oldLine) return entry
+    return restoreLeadingIndent(oldLine, entry)
+  })
   result.splice(startLine - 1, endLine - startLine + 1, ...newLines)
   return result
 }
 
-export function applyInsertAfter(lines: string[], anchor: string, text: string): string[] {
+export function applyInsertAfter(lines: string[], anchor: string, text: string | string[]): string[] {
   validateLineRef(lines, anchor)
   const { line } = parseLineRef(anchor)
   const result = [...lines]
-  const newLines = unescapeNewlines(text).split("\n")
+  const newLines = stripInsertAnchorEcho(lines[line - 1], toNewLines(text))
   result.splice(line, 0, ...newLines)
   return result
 }
 
-export function applyReplace(content: string, oldText: string, newText: string): string {
+export function applyReplace(content: string, oldText: string, newText: string | string[]): string {
   if (!content.includes(oldText)) {
     throw new Error(`Text not found: "${oldText}"`)
   }
-  return content.replaceAll(oldText, unescapeNewlines(newText))
+  const replacement = Array.isArray(newText) ? newText.join("\n") : newText
+  return content.replaceAll(oldText, replacement)
 }
 
 function getEditLineNumber(edit: HashlineEdit): number {
@@ -78,33 +175,34 @@ export function applyHashlineEdits(content: string, edits: HashlineEdit[]): stri
   let result = content
   let lines = result.split("\n")
 
+  const refs = sortedEdits.flatMap((edit) => {
+    switch (edit.type) {
+      case "set_line":
+        return [edit.line]
+      case "replace_lines":
+        return [edit.start_line, edit.end_line]
+      case "insert_after":
+        return [edit.line]
+      case "replace":
+        return []
+      default:
+        return []
+    }
+  })
+  validateLineRefs(lines, refs)
+
   for (const edit of sortedEdits) {
     switch (edit.type) {
       case "set_line": {
-        validateLineRef(lines, edit.line)
-        const { line } = parseLineRef(edit.line)
-        lines[line - 1] = unescapeNewlines(edit.text)
+        lines = applySetLine(lines, edit.line, edit.text)
         break
       }
       case "replace_lines": {
-        validateLineRef(lines, edit.start_line)
-        validateLineRef(lines, edit.end_line)
-        const { line: startLine } = parseLineRef(edit.start_line)
-        const { line: endLine } = parseLineRef(edit.end_line)
-        if (startLine > endLine) {
-          throw new Error(
-            `Invalid range: start line ${startLine} cannot be greater than end line ${endLine}`
-          )
-        }
-        const newLines = unescapeNewlines(edit.text).split("\n")
-        lines.splice(startLine - 1, endLine - startLine + 1, ...newLines)
+        lines = applyReplaceLines(lines, edit.start_line, edit.end_line, edit.text)
         break
       }
       case "insert_after": {
-        validateLineRef(lines, edit.line)
-        const { line } = parseLineRef(edit.line)
-        const newLines = unescapeNewlines(edit.text).split("\n")
-        lines.splice(line, 0, ...newLines)
+        lines = applyInsertAfter(lines, edit.line, edit.text)
         break
       }
       case "replace": {
@@ -112,7 +210,8 @@ export function applyHashlineEdits(content: string, edits: HashlineEdit[]): stri
         if (!result.includes(edit.old_text)) {
           throw new Error(`Text not found: "${edit.old_text}"`)
         }
-        result = result.replaceAll(edit.old_text, unescapeNewlines(edit.new_text))
+        const replacement = Array.isArray(edit.new_text) ? edit.new_text.join("\n") : edit.new_text
+        result = result.replaceAll(edit.old_text, replacement)
         lines = result.split("\n")
         break
       }
diff --git a/src/tools/hashline-edit/tools.test.ts b/src/tools/hashline-edit/tools.test.ts
index 44dfe4097..37f9d2fd8 100644
--- a/src/tools/hashline-edit/tools.test.ts
+++ b/src/tools/hashline-edit/tools.test.ts
@@ -1,18 +1,12 @@
 import { describe, it, expect, beforeEach, afterEach, mock } from "bun:test"
 import type { ToolContext } from "@opencode-ai/plugin/tool"
-import { consumeToolMetadata, clearPendingStore } from "../../features/tool-metadata-store"
 import { createHashlineEditTool } from "./tools"
-import * as fs from "node:fs"
-import * as path from "node:path"
-import * as os from "node:os"
 import { computeLineHash } from "./hash-computation"
+import * as fs from "node:fs"
+import * as os from "node:os"
+import * as path from "node:path"
 
-type MetadataPayload = {
-  title?: string
-  metadata?: Record<string, unknown>
-}
-
-function createMockContext(overrides?: Partial<Pick<ToolContext, "metadata">>): ToolContext {
+function createMockContext(): ToolContext {
   return {
     sessionID: "test",
     messageID: "test",
@@ -20,17 +14,11 @@ function createMockContext(overrides?: Partial<Pick<ToolContext, "metadata">>):
     directory: "/tmp",
     worktree: "/tmp",
     abort: new AbortController().signal,
-    metadata: overrides?.metadata ?? mock(() => {}),
+    metadata: mock(() => {}),
     ask: async () => {},
   }
 }
 
-type ToolContextWithCallID = ToolContext & {
-  callID?: string
-  callId?: string
-  call_id?: string
-}
-
 describe("createHashlineEditTool", () => {
   let tempDir: string
   let tool: ReturnType<typeof createHashlineEditTool>
@@ -42,373 +30,106 @@ describe("createHashlineEditTool", () => {
 
   afterEach(() => {
     fs.rmSync(tempDir, { recursive: true, force: true })
-    clearPendingStore()
   })
 
-  describe("tool definition", () => {
-    it("has correct description", () => {
-      //#given tool is created
-      //#when accessing tool properties
-      //#then description explains LINE:HASH format
-      expect(tool.description).toContain("LINE:HASH")
-      expect(tool.description).toContain("set_line")
-      expect(tool.description).toContain("replace_lines")
-      expect(tool.description).toContain("insert_after")
-      expect(tool.description).toContain("replace")
-    })
+  it("applies set_line with LINE#ID anchor", async () => {
+    //#given
+    const filePath = path.join(tempDir, "test.txt")
+    fs.writeFileSync(filePath, "line1\nline2\nline3")
+    const hash = computeLineHash(2, "line2")
 
-    it("has filePath parameter", () => {
-      //#given tool is created
-      //#when checking parameters
-      //#then filePath exists
-      expect(tool.args.filePath).toBeDefined()
-    })
+    //#when
+    const result = await tool.execute(
+      {
+        filePath,
+        edits: [{ type: "set_line", line: `2#${hash}`, text: "modified line2" }],
+      },
+      createMockContext(),
+    )
 
-    it("has edits parameter as array", () => {
-      //#given tool is created
-      //#when checking parameters
-      //#then edits parameter exists as array
-      expect(tool.args.edits).toBeDefined()
-    })
+    //#then
+    expect(fs.readFileSync(filePath, "utf-8")).toBe("line1\nmodified line2\nline3")
+    expect(result).toContain("Successfully")
+    expect(result).toContain("Updated file (LINE#ID:content)")
+    expect(result).toMatch(/2#[ZPMQVRWSNKTXJBYH]{2}:modified line2/)
   })
 
-  describe("execute", () => {
-    it("returns error when file does not exist", async () => {
-      //#given non-existent file path
-      const nonExistentPath = path.join(tempDir, "non-existent.txt")
+  it("applies replace_lines and insert_after", async () => {
+    //#given
+    const filePath = path.join(tempDir, "test.txt")
+    fs.writeFileSync(filePath, "line1\nline2\nline3\nline4")
+    const line2Hash = computeLineHash(2, "line2")
+    const line3Hash = computeLineHash(3, "line3")
+    const line4Hash = computeLineHash(4, "line4")
 
-      //#when executing tool
-      const result = await tool.execute(
-        {
-          filePath: nonExistentPath,
-          edits: [{ type: "set_line", line: "1:00", text: "new content" }],
-        },
-        createMockContext()
-      )
+    //#when
+    await tool.execute(
+      {
+        filePath,
+        edits: [
+          {
+            type: "replace_lines",
+            start_line: `2#${line2Hash}`,
+            end_line: `3#${line3Hash}`,
+            text: "replaced",
+          },
+          {
+            type: "insert_after",
+            line: `4#${line4Hash}`,
+            text: "inserted",
+          },
+        ],
+      },
+      createMockContext(),
+    )
 
-      //#then error is returned
-      expect(result).toContain("Error")
-      expect(result).toContain("not found")
-    })
-
-    it("applies set_line edit and returns diff", async () => {
-      //#given file with content
-      const filePath = path.join(tempDir, "test.txt")
-      fs.writeFileSync(filePath, "line1\nline2\nline3")
-      const line2Hash = computeLineHash(2, "line2")
-
-      //#when executing set_line edit
-      const result = await tool.execute(
-        {
-          filePath,
-          edits: [{ type: "set_line", line: `2:${line2Hash}`, text: "modified line2" }],
-        },
-        createMockContext()
-      )
-
-      //#then file is modified and diff is returned
-      const content = fs.readFileSync(filePath, "utf-8")
-      expect(content).toBe("line1\nmodified line2\nline3")
-      expect(result).toContain("modified line2")
-    })
-
-    it("applies insert_after edit", async () => {
-      //#given file with content
-      const filePath = path.join(tempDir, "test.txt")
-      fs.writeFileSync(filePath, "line1\nline2")
-      const line1Hash = computeLineHash(1, "line1")
-
-      //#when executing insert_after edit
-      const result = await tool.execute(
-        {
-          filePath,
-          edits: [{ type: "insert_after", line: `1:${line1Hash}`, text: "inserted" }],
-        },
-        createMockContext()
-      )
-
-      //#then line is inserted after specified line
-      const content = fs.readFileSync(filePath, "utf-8")
-      expect(content).toBe("line1\ninserted\nline2")
-    })
-
-    it("applies replace_lines edit", async () => {
-      //#given file with content
-      const filePath = path.join(tempDir, "test.txt")
-      fs.writeFileSync(filePath, "line1\nline2\nline3\nline4")
-      const line2Hash = computeLineHash(2, "line2")
-      const line3Hash = computeLineHash(3, "line3")
-
-      //#when executing replace_lines edit
-      const result = await tool.execute(
-        {
-          filePath,
-          edits: [
-            {
-              type: "replace_lines",
-              start_line: `2:${line2Hash}`,
-              end_line: `3:${line3Hash}`,
-              text: "replaced",
-            },
-          ],
-        },
-        createMockContext()
-      )
-
-      //#then lines are replaced
-      const content = fs.readFileSync(filePath, "utf-8")
-      expect(content).toBe("line1\nreplaced\nline4")
-    })
-
-    it("applies replace edit", async () => {
-      //#given file with content
-      const filePath = path.join(tempDir, "test.txt")
-      fs.writeFileSync(filePath, "hello world\nfoo bar")
-
-      //#when executing replace edit
-      const result = await tool.execute(
-        {
-          filePath,
-          edits: [{ type: "replace", old_text: "world", new_text: "universe" }],
-        },
-        createMockContext()
-      )
-
-      //#then text is replaced
-      const content = fs.readFileSync(filePath, "utf-8")
-      expect(content).toBe("hello universe\nfoo bar")
-    })
-
-    it("applies multiple edits in bottom-up order", async () => {
-      //#given file with content
-      const filePath = path.join(tempDir, "test.txt")
-      fs.writeFileSync(filePath, "line1\nline2\nline3")
-      const line1Hash = computeLineHash(1, "line1")
-      const line3Hash = computeLineHash(3, "line3")
-
-      //#when executing multiple edits
-      const result = await tool.execute(
-        {
-          filePath,
-          edits: [
-            { type: "set_line", line: `1:${line1Hash}`, text: "new1" },
-            { type: "set_line", line: `3:${line3Hash}`, text: "new3" },
-          ],
-        },
-        createMockContext()
-      )
-
-      //#then both edits are applied
-      const content = fs.readFileSync(filePath, "utf-8")
-      expect(content).toBe("new1\nline2\nnew3")
-    })
-
-    it("returns error on hash mismatch", async () => {
-      //#given file with content
-      const filePath = path.join(tempDir, "test.txt")
-      fs.writeFileSync(filePath, "line1\nline2")
-
-      //#when executing with wrong hash (valid format but wrong value)
-      const result = await tool.execute(
-        {
-          filePath,
-          edits: [{ type: "set_line", line: "1:ff", text: "new" }],
-        },
-        createMockContext()
-      )
-
-      //#then hash mismatch error is returned
-      expect(result).toContain("Error")
-      expect(result).toContain("hash")
-    })
-
-    it("handles escaped newlines in text", async () => {
-      //#given file with content
-      const filePath = path.join(tempDir, "test.txt")
-      fs.writeFileSync(filePath, "line1\nline2")
-      const line1Hash = computeLineHash(1, "line1")
-
-      //#when executing with escaped newline
-      const result = await tool.execute(
-        {
-          filePath,
-          edits: [{ type: "set_line", line: `1:${line1Hash}`, text: "new\\nline" }],
-        },
-        createMockContext()
-      )
-
-      //#then newline is unescaped
-      const content = fs.readFileSync(filePath, "utf-8")
-      expect(content).toBe("new\nline\nline2")
-    })
-
-    it("returns success result with diff summary", async () => {
-      //#given file with content
-      const filePath = path.join(tempDir, "test.txt")
-      fs.writeFileSync(filePath, "old content")
-      const line1Hash = computeLineHash(1, "old content")
-
-      //#when executing edit
-      const result = await tool.execute(
-        {
-          filePath,
-          edits: [{ type: "set_line", line: `1:${line1Hash}`, text: "new content" }],
-        },
-        createMockContext()
-      )
-
-      //#then result contains success indicator and diff
-      expect(result).toContain("Successfully")
-      expect(result).toContain("old content")
-      expect(result).toContain("new content")
-      expect(result).toContain("Updated file (LINE:HASH|content)")
-      expect(result).toMatch(/1:[a-f0-9]{2}\|new content/)
-    })
+    //#then
+    expect(fs.readFileSync(filePath, "utf-8")).toBe("line1\nreplaced\nline4\ninserted")
   })
 
-  describe("context.metadata for TUI diff", () => {
-    it("calls context.metadata with diff and filediff on successful edit", async () => {
-      //#given file with content and mock context
-      const filePath = path.join(tempDir, "test.txt")
-      fs.writeFileSync(filePath, "line1\nline2\nline3")
-      const line2Hash = computeLineHash(2, "line2")
-      const metadataMock = mock((_: MetadataPayload) => {})
-      const ctx = createMockContext({ metadata: metadataMock })
+  it("returns mismatch error on stale anchor", async () => {
+    //#given
+    const filePath = path.join(tempDir, "test.txt")
+    fs.writeFileSync(filePath, "line1\nline2")
 
-      //#when executing a successful edit
-      await tool.execute(
-        {
-          filePath,
-          edits: [{ type: "set_line", line: `2:${line2Hash}`, text: "modified" }],
-        },
-        ctx
-      )
+    //#when
+    const result = await tool.execute(
+      {
+        filePath,
+        edits: [{ type: "set_line", line: "1#ZZ", text: "new" }],
+      },
+      createMockContext(),
+    )
 
-      //#then context.metadata is called with diff string and filediff object
-      expect(metadataMock).toHaveBeenCalledTimes(1)
-      const call = metadataMock.mock.calls[0]?.[0]
-      expect(call).toBeDefined()
-      if (!call || !call.metadata) {
-        throw new Error("metadata payload missing")
-      }
-      expect(call.title).toBe(filePath)
-      expect(call.metadata.filePath).toBe(filePath)
-      expect(call.metadata.path).toBe(filePath)
-      expect(call.metadata.file).toBe(filePath)
-      expect(call.metadata.diff).toContain("---")
-      expect(call.metadata.diff).toContain("+++")
-      expect(call.metadata.diff).toContain("-line2")
-      expect(call.metadata.diff).toContain("+modified")
-      expect(call.metadata.filediff.file).toBe(filePath)
-      expect(call.metadata.filediff.path).toBe(filePath)
-      expect(call.metadata.filediff.filePath).toBe(filePath)
-      expect(typeof call.metadata.filediff.before).toBe("string")
-      expect(typeof call.metadata.filediff.after).toBe("string")
-      expect(typeof call.metadata.filediff.additions).toBe("number")
-      expect(typeof call.metadata.filediff.deletions).toBe("number")
-    })
+    //#then
+    expect(result).toContain("Error")
+    expect(result).toContain("hash")
+  })
 
-    it("includes hashline content in filediff before/after", async () => {
-      //#given file with known content
-      const filePath = path.join(tempDir, "test.txt")
-      fs.writeFileSync(filePath, "hello\nworld")
-      const line1Hash = computeLineHash(1, "hello")
-      const metadataMock = mock((_: MetadataPayload) => {})
-      const ctx = createMockContext({ metadata: metadataMock })
+  it("preserves literal backslash-n and supports string[] payload", async () => {
+    //#given
+    const filePath = path.join(tempDir, "test.txt")
+    fs.writeFileSync(filePath, "line1\nline2")
+    const line1Hash = computeLineHash(1, "line1")
 
-      //#when executing edit
-      await tool.execute(
-        {
-          filePath,
-          edits: [{ type: "set_line", line: `1:${line1Hash}`, text: "hi" }],
-        },
-        ctx
-      )
+    //#when
+    await tool.execute(
+      {
+        filePath,
+        edits: [{ type: "set_line", line: `1#${line1Hash}`, text: "join(\\n)" }],
+      },
+      createMockContext(),
+    )
 
-      //#then filediff.before contains hashline format of original content
-      const call = metadataMock.mock.calls[0]?.[0]
-      expect(call).toBeDefined()
-      if (!call || !call.metadata) {
-        throw new Error("metadata payload missing")
-      }
-      expect(call.metadata.filediff.before).toContain("1:")
-      expect(call.metadata.filediff.before).toContain("|hello")
-      expect(call.metadata.filediff.after).toContain("1:")
-      expect(call.metadata.filediff.after).toContain("|hi")
-    })
+    await tool.execute(
+      {
+        filePath,
+        edits: [{ type: "insert_after", line: `1#${computeLineHash(1, "join(\\n)")}`, text: ["a", "b"] }],
+      },
+      createMockContext(),
+    )
 
-    it("reports correct additions and deletions count", async () => {
-      //#given file with content
-      const filePath = path.join(tempDir, "test.txt")
-      fs.writeFileSync(filePath, "aaa\nbbb\nccc")
-      const metadataMock = mock((_: MetadataPayload) => {})
-      const ctx = createMockContext({ metadata: metadataMock })
-
-      //#when replacing text that changes one line
-      await tool.execute(
-        {
-          filePath,
-          edits: [{ type: "replace", old_text: "bbb", new_text: "xxx" }],
-        },
-        ctx
-      )
-
-      //#then additions and deletions are both 1
-      const call = metadataMock.mock.calls[0]?.[0]
-      expect(call).toBeDefined()
-      if (!call || !call.metadata) {
-        throw new Error("metadata payload missing")
-      }
-      expect(call.metadata.filediff.additions).toBe(1)
-      expect(call.metadata.filediff.deletions).toBe(1)
-    })
-
-    it("does not call context.metadata on error", async () => {
-      //#given non-existent file
-      const nonExistentPath = path.join(tempDir, "nope.txt")
-      const metadataMock = mock(() => {})
-      const ctx = createMockContext({ metadata: metadataMock })
-
-      //#when executing tool on missing file
-      await tool.execute(
-        {
-          filePath: nonExistentPath,
-          edits: [{ type: "set_line", line: "1:00", text: "new" }],
-        },
-        ctx
-      )
-
-      //#then context.metadata is never called
-      expect(metadataMock).not.toHaveBeenCalled()
-    })
-
-    it("stores metadata for tool.execute.after restoration when callID exists", async () => {
-      //#given file and context with callID
-      const filePath = path.join(tempDir, "test.txt")
-      fs.writeFileSync(filePath, "line1\nline2")
-      const line2Hash = computeLineHash(2, "line2")
-
-      const metadataMock = mock((_: MetadataPayload) => {})
-      const ctx: ToolContextWithCallID = {
-        ...createMockContext({ metadata: metadataMock }),
-        callID: "call-edit-meta-1",
-      }
-
-      //#when executing edit
-      await tool.execute(
-        {
-          filePath,
-          edits: [{ type: "set_line", line: `2:${line2Hash}`, text: "modified" }],
-        },
-        ctx,
-      )
-
-      //#then pending metadata store has restorable metadata
-      const restored = consumeToolMetadata(ctx.sessionID, "call-edit-meta-1")
-      expect(restored).toBeDefined()
-      expect(restored?.title).toBe(filePath)
-      expect(typeof restored?.metadata?.diff).toBe("string")
-      expect(restored?.metadata?.filediff).toBeDefined()
-    })
+    //#then
+    expect(fs.readFileSync(filePath, "utf-8")).toBe("join(\\n)\na\nb\nline2")
   })
 })
diff --git a/src/tools/hashline-edit/tools.ts b/src/tools/hashline-edit/tools.ts
index 61d8b916a..e42254d50 100644
--- a/src/tools/hashline-edit/tools.ts
+++ b/src/tools/hashline-edit/tools.ts
@@ -37,12 +37,12 @@ function generateDiff(oldContent: string, newContent: string, filePath: string):
     const hash = computeLineHash(lineNum, newLine)
 
     if (i >= oldLines.length) {
-      diff += `+ ${lineNum}:${hash}|${newLine}\n`
+      diff += `+ ${lineNum}#${hash}:${newLine}\n`
     } else if (i >= newLines.length) {
-      diff += `- ${lineNum}:  |${oldLine}\n`
+      diff += `- ${lineNum}#  :${oldLine}\n`
     } else if (oldLine !== newLine) {
-      diff += `- ${lineNum}:  |${oldLine}\n`
-      diff += `+ ${lineNum}:${hash}|${newLine}\n`
+      diff += `- ${lineNum}#  :${oldLine}\n`
+      diff += `+ ${lineNum}#${hash}:${newLine}\n`
     }
   }
 
@@ -51,41 +51,41 @@ function generateDiff(oldContent: string, newContent: string, filePath: string):
 
 export function createHashlineEditTool(): ToolDefinition {
   return tool({
-    description: `Edit files using LINE:HASH format for precise, safe modifications.
+    description: `Edit files using LINE#ID format for precise, safe modifications.
 
 WORKFLOW:
-1. Read the file and copy exact LINE:HASH anchors.
+1. Read the file and copy exact LINE#ID anchors.
 2. Submit one edit call with all related operations for that file.
 3. If more edits are needed after success, use the latest anchors from read/edit output.
-4. Use anchors as "LINE:HASH" only (never include trailing "|content").
+4. Use anchors as "LINE#ID" only (never include trailing ":content").
 
 VALIDATION:
 - Payload shape: { "filePath": string, "edits": [...] }
 - Each edit must be one of: set_line, replace_lines, insert_after, replace
-- text/new_text must contain plain replacement text only (no LINE:HASH prefixes, no diff + markers)
+- text/new_text must contain plain replacement text only (no LINE#ID prefixes, no diff + markers)
 
-LINE:HASH FORMAT (CRITICAL - READ CAREFULLY):
-Each line reference must be in "LINE:HASH" format where:
+LINE#ID FORMAT (CRITICAL - READ CAREFULLY):
+Each line reference must be in "LINE#ID" format where:
 - LINE: 1-based line number
-- HASH: First 2 characters of xxHash32 hash of line content (hex characters 0-9, a-f only)
-- Example: "5:a3" means line 5 with hash "a3"
-- WRONG: "2:co" (contains non-hex 'o') - will fail!
-- CORRECT: "2:e8" (hex characters only)
+- ID: Two CID letters from the set ZPMQVRWSNKTXJBYH
+- Example: "5#VK" means line 5 with hash id "VK"
+- WRONG: "2#aa" (invalid characters) - will fail!
+- CORRECT: "2#VK"
 
 GETTING HASHES:
-Use the read tool - it returns lines in "LINE:HASH|content" format.
-Successful edit output also includes updated file content in "LINE:HASH|content" format.
+Use the read tool - it returns lines in "LINE#ID:content" format.
+Successful edit output also includes updated file content in "LINE#ID:content" format.
 
 FOUR OPERATION TYPES:
 
 1. set_line: Replace a single line
-   { "type": "set_line", "line": "5:a3", "text": "const y = 2" }
+   { "type": "set_line", "line": "5#VK", "text": "const y = 2" }
 
 2. replace_lines: Replace a range of lines
-   { "type": "replace_lines", "start_line": "5:a3", "end_line": "7:b2", "text": "new\\ncontent" }
+   { "type": "replace_lines", "start_line": "5#VK", "end_line": "7#NP", "text": ["new", "content"] }
 
 3. insert_after: Insert lines after a specific line
-   { "type": "insert_after", "line": "5:a3", "text": "console.log('hi')" }
+   { "type": "insert_after", "line": "5#VK", "text": "console.log('hi')" }
 
 4. replace: Simple text replacement (no hash validation)
    { "type": "replace", "old_text": "foo", "new_text": "bar" }
@@ -101,8 +101,10 @@ SEQUENTIAL EDITS (ANTI-FLAKE):
 BOTTOM-UP APPLICATION:
 Edits are applied from bottom to top (highest line numbers first) to preserve line number references.
 
-ESCAPING:
-Use \\n in text to represent literal newlines.`,
+CONTENT FORMAT:
+- text/new_text can be a string (single line) or string[] (multi-line, preferred).
+- If you pass a multi-line string, it is split by real newline characters.
+- Literal "\\n" is preserved as text.`,
     args: {
       filePath: tool.schema.string().describe("Absolute path to the file to edit"),
       edits: tool.schema
@@ -110,24 +112,32 @@ Use \\n in text to represent literal newlines.`,
           tool.schema.union([
             tool.schema.object({
               type: tool.schema.literal("set_line"),
-              line: tool.schema.string().describe("Line reference in LINE:HASH format"),
-              text: tool.schema.string().describe("New content for the line"),
+              line: tool.schema.string().describe("Line reference in LINE#ID format"),
+              text: tool.schema
+                .union([tool.schema.string(), tool.schema.array(tool.schema.string())])
+                .describe("New content for the line (string or string[] for multiline)"),
             }),
             tool.schema.object({
               type: tool.schema.literal("replace_lines"),
-              start_line: tool.schema.string().describe("Start line in LINE:HASH format"),
-              end_line: tool.schema.string().describe("End line in LINE:HASH format"),
-              text: tool.schema.string().describe("New content to replace the range"),
+              start_line: tool.schema.string().describe("Start line in LINE#ID format"),
+              end_line: tool.schema.string().describe("End line in LINE#ID format"),
+              text: tool.schema
+                .union([tool.schema.string(), tool.schema.array(tool.schema.string())])
+                .describe("New content to replace the range (string or string[] for multiline)"),
             }),
             tool.schema.object({
               type: tool.schema.literal("insert_after"),
-              line: tool.schema.string().describe("Line reference in LINE:HASH format"),
-              text: tool.schema.string().describe("Content to insert after the line"),
+              line: tool.schema.string().describe("Line reference in LINE#ID format"),
+              text: tool.schema
+                .union([tool.schema.string(), tool.schema.array(tool.schema.string())])
+                .describe("Content to insert after the line (string or string[] for multiline)"),
             }),
             tool.schema.object({
               type: tool.schema.literal("replace"),
               old_text: tool.schema.string().describe("Text to find"),
-              new_text: tool.schema.string().describe("Replacement text"),
+              new_text: tool.schema
+                .union([tool.schema.string(), tool.schema.array(tool.schema.string())])
+                .describe("Replacement text (string or string[] for multiline)"),
             }),
           ])
         )
@@ -154,7 +164,6 @@ Use \\n in text to represent literal newlines.`,
         await Bun.write(filePath, newContent)
 
         const diff = generateDiff(oldContent, newContent, filePath)
-        const oldHashlined = toHashlineContent(oldContent)
         const newHashlined = toHashlineContent(newContent)
 
         const unifiedDiff = generateUnifiedDiff(oldContent, newContent, filePath)
@@ -171,8 +180,8 @@ Use \\n in text to represent literal newlines.`,
               file: filePath,
               path: filePath,
               filePath,
-              before: oldHashlined,
-              after: newHashlined,
+              before: oldContent,
+              after: newContent,
               additions,
               deletions,
             },
@@ -190,12 +199,12 @@ Use \\n in text to represent literal newlines.`,
 
 ${diff}
 
-Updated file (LINE:HASH|content):
+Updated file (LINE#ID:content):
 ${newHashlined}`
       } catch (error) {
         const message = error instanceof Error ? error.message : String(error)
-        if (message.includes("hash")) {
-          return `Error: Hash mismatch - ${message}\nTip: reuse LINE:HASH entries from the latest read/edit output, or batch related edits in one call.`
+        if (message.toLowerCase().includes("hash")) {
+          return `Error: hash mismatch - ${message}\nTip: reuse LINE#ID entries from the latest read/edit output, or batch related edits in one call.`
         }
         return `Error: ${message}`
       }
diff --git a/src/tools/hashline-edit/validation.test.ts b/src/tools/hashline-edit/validation.test.ts
index e824a4aae..8b6870f68 100644
--- a/src/tools/hashline-edit/validation.test.ts
+++ b/src/tools/hashline-edit/validation.test.ts
@@ -3,104 +3,52 @@ import { computeLineHash } from "./hash-computation"
 import { parseLineRef, validateLineRef } from "./validation"
 
 describe("parseLineRef", () => {
-  it("parses valid line reference", () => {
+  it("parses valid LINE#ID reference", () => {
     //#given
-    const ref = "42:a3"
+    const ref = "42#VK"
 
     //#when
     const result = parseLineRef(ref)
 
     //#then
-    expect(result).toEqual({ line: 42, hash: "a3" })
+    expect(result).toEqual({ line: 42, hash: "VK" })
   })
 
-  it("parses line reference with different hash", () => {
+  it("throws on invalid format", () => {
     //#given
-    const ref = "1:ff"
+    const ref = "42:VK"
+
+    //#when / #then
+    expect(() => parseLineRef(ref)).toThrow("LINE#ID")
+  })
+
+  it("accepts refs copied with markers and trailing content", () => {
+    //#given
+    const ref = ">>> 42#VK:const value = 1"
 
     //#when
     const result = parseLineRef(ref)
 
     //#then
-    expect(result).toEqual({ line: 1, hash: "ff" })
-  })
-
-  it("throws on invalid format - no colon", () => {
-    //#given
-    const ref = "42a3"
-
-    //#when & #then
-    expect(() => parseLineRef(ref)).toThrow()
-  })
-
-  it("throws on invalid format - non-numeric line", () => {
-    //#given
-    const ref = "abc:a3"
-
-    //#when & #then
-    expect(() => parseLineRef(ref)).toThrow()
-  })
-
-  it("throws on invalid format - invalid hash", () => {
-    //#given
-    const ref = "42:xyz"
-
-    //#when & #then
-    expect(() => parseLineRef(ref)).toThrow()
-  })
-
-  it("throws on empty string", () => {
-    //#given
-    const ref = ""
-
-    //#when & #then
-    expect(() => parseLineRef(ref)).toThrow()
+    expect(result).toEqual({ line: 42, hash: "VK" })
   })
 })
 
 describe("validateLineRef", () => {
-  it("validates matching hash", () => {
+  it("accepts matching reference", () => {
     //#given
     const lines = ["function hello() {", "  return 42", "}"]
-    const ref = `1:${computeLineHash(1, lines[0])}`
+    const hash = computeLineHash(1, lines[0])
 
-    //#when & #then
-    expect(() => validateLineRef(lines, ref)).not.toThrow()
+    //#when / #then
+    expect(() => validateLineRef(lines, `1#${hash}`)).not.toThrow()
   })
 
-  it("throws on hash mismatch", () => {
-    //#given
-    const lines = ["function hello() {", "  return 42", "}"]
-    const ref = "1:00" // Wrong hash
-
-    //#when & #then
-    expect(() => validateLineRef(lines, ref)).toThrow()
-  })
-
-  it("throws on line out of bounds", () => {
-    //#given
-    const lines = ["function hello() {", "  return 42", "}"]
-    const ref = "99:a3"
-
-    //#when & #then
-    expect(() => validateLineRef(lines, ref)).toThrow()
-  })
-
-  it("throws on invalid line number", () => {
+  it("throws on mismatch and includes current hash", () => {
     //#given
     const lines = ["function hello() {"]
-    const ref = "0:a3" // Line numbers start at 1
 
-    //#when & #then
-    expect(() => validateLineRef(lines, ref)).toThrow()
-  })
-
-  it("error message includes current hash", () => {
-    //#given
-    const lines = ["function hello() {"]
-    const ref = "1:00"
-
-    //#when & #then
-    expect(() => validateLineRef(lines, ref)).toThrow(/current hash/)
+    //#when / #then
+    expect(() => validateLineRef(lines, "1#ZZ")).toThrow(/current hash/)
   })
 })
diff --git a/src/tools/hashline-edit/validation.ts b/src/tools/hashline-edit/validation.ts
index 178f35d8e..feb9d3cc7 100644
--- a/src/tools/hashline-edit/validation.ts
+++ b/src/tools/hashline-edit/validation.ts
@@ -1,15 +1,33 @@
 import { computeLineHash } from "./hash-computation"
+import { HASHLINE_REF_PATTERN } from "./constants"
 
 export interface LineRef {
   line: number
   hash: string
 }
 
+const LINE_REF_EXTRACT_PATTERN = /([0-9]+#[ZPMQVRWSNKTXJBYH]{2})/
+
+function normalizeLineRef(ref: string): string {
+  const trimmed = ref.trim()
+  if (HASHLINE_REF_PATTERN.test(trimmed)) {
+    return trimmed
+  }
+
+  const extracted = trimmed.match(LINE_REF_EXTRACT_PATTERN)
+  if (extracted) {
+    return extracted[1]
+  }
+
+  return trimmed
+}
+
 export function parseLineRef(ref: string): LineRef {
-  const match = ref.match(/^(\d+):([0-9a-f]{2})$/)
+  const normalized = normalizeLineRef(ref)
+  const match = normalized.match(HASHLINE_REF_PATTERN)
   if (!match) {
     throw new Error(
-      `Invalid line reference format: "${ref}". Expected format: "LINE:HASH" (e.g., "42:a3")`
+      `Invalid line reference format: "${ref}". Expected format: "LINE#ID" (e.g., "42#VK")`
     )
   }
   return {
@@ -37,3 +55,28 @@ export function validateLineRef(lines: string[], ref: string): void {
     )
   }
 }
+
+export function validateLineRefs(lines: string[], refs: string[]): void {
+  const mismatches: string[] = []
+
+  for (const ref of refs) {
+    const { line, hash } = parseLineRef(ref)
+
+    if (line < 1 || line > lines.length) {
+      mismatches.push(`Line number ${line} out of bounds (file has ${lines.length} lines)`) 
+      continue
+    }
+
+    const content = lines[line - 1]
+    const currentHash = computeLineHash(line, content)
+    if (currentHash !== hash) {
+      mismatches.push(
+        `line ${line}: expected ${hash}, current ${currentHash} (${line}#${currentHash}) content: "${content}"`
+      )
+    }
+  }
+
+  if (mismatches.length > 0) {
+    throw new Error(`Hash mismatches:\n- ${mismatches.join("\n- ")}`)
+  }
+}