diff --git a/packages/kilo-vscode/src/agent-manager/GitOps.ts b/packages/kilo-vscode/src/agent-manager/GitOps.ts
index f835cf3832c..0f0ff9a2048 100644
--- a/packages/kilo-vscode/src/agent-manager/GitOps.ts
+++ b/packages/kilo-vscode/src/agent-manager/GitOps.ts
@@ -205,7 +205,7 @@ export class GitOps {
     const remote = await this.resolveRemote(cwd, branch)
     const cacheKey = `default-branch:${cwd}:${remote}`
     const cached = this.getCached(cacheKey)
-    if (cached !== undefined) return cached
+    if (cached !== undefined) return cached === "" ? undefined : cached
 
     const head = await this.raw(["symbolic-ref", "--short", `refs/remotes/${remote}/HEAD`], cwd).catch(() => "")
     const result = head || undefined
diff --git a/packages/kilo-vscode/src/agent-manager/local-diff.ts b/packages/kilo-vscode/src/agent-manager/local-diff.ts
index 977b01de13d..c58189dace2 100644
--- a/packages/kilo-vscode/src/agent-manager/local-diff.ts
+++ b/packages/kilo-vscode/src/agent-manager/local-diff.ts
@@ -90,10 +90,25 @@ export function generatedLike(file: string): boolean {
   return false
 }
 
+const BASE_CANDIDATES = ["main", "master", "dev", "develop"]
+
+export async function resolveBase(git: GitOps, dir: string, base: string): Promise<string> {
+  // If the caller gave an explicit base, honor it. Return it as-is so merge-base
+  // fails loudly on a stale/misspelled ref instead of silently diffing against
+  // an unrelated candidate branch.
+  if (base && base !== "HEAD") return base
+  for (const name of BASE_CANDIDATES) {
+    const ok = await git.execGit(["rev-parse", "--verify", "--quiet", `refs/heads/${name}`], dir)
+    if (ok.code === 0) return name
+  }
+  return "HEAD"
+}
+
 async function ancestor(git: GitOps, dir: string, base: string, log?: Log): Promise<string | undefined> {
-  const result = await git.execGit(["merge-base", "HEAD", base], dir)
+  const resolvedBase = await resolveBase(git, dir, base)
+  const result = await git.execGit(["merge-base", "HEAD", resolvedBase], dir)
   if (result.code !== 0) {
-    log?.("git merge-base failed", { code: result.code, stderr: result.stderr.trim(), dir, base })
+    log?.("git merge-base failed", { code: result.code, stderr: result.stderr.trim(), dir, base, resolvedBase })
     return undefined
   }
   return result.stdout.trim()
diff --git a/packages/kilo-vscode/src/review-utils.ts b/packages/kilo-vscode/src/review-utils.ts
index e5c56a3b287..1e2a7c7927a 100644
--- a/packages/kilo-vscode/src/review-utils.ts
+++ b/packages/kilo-vscode/src/review-utils.ts
@@ -3,6 +3,7 @@ import * as vscode from "vscode"
 import { inspect } from "util"
 import type { SnapshotFileDiff } from "@kilocode/sdk/v2/client"
 import { GitOps } from "./agent-manager/GitOps"
+import { resolveBase } from "./agent-manager/local-diff"
 
 export function appendOutput(channel: vscode.OutputChannel, prefix: string, ...args: unknown[]): void {
   const msg = args
@@ -35,7 +36,8 @@ export async function resolveLocalDiffTarget(
 
   const tracking = await gitOps.resolveTrackingBranch(root, branch)
   const fallback = tracking ? undefined : await gitOps.resolveDefaultBranch(root, branch)
-  const base = tracking ?? fallback ?? "HEAD"
+  const raw = tracking || fallback || "HEAD"
+  const base = await resolveBase(gitOps, root, raw)
 
   log(`Local diff: branch=${branch} tracking=${tracking ?? "none"} default=${fallback ?? "none"} base=${base}`)
 
diff --git a/packages/kilo-vscode/tests/unit/git-stats-poller.test.ts b/packages/kilo-vscode/tests/unit/git-stats-poller.test.ts
index 8b1844f7641..0afb8b9254d 100644
--- a/packages/kilo-vscode/tests/unit/git-stats-poller.test.ts
+++ b/packages/kilo-vscode/tests/unit/git-stats-poller.test.ts
@@ -53,6 +53,35 @@ function gitOps(handler: (args: string[], cwd: string) => Promise<string>): GitO
   return new GitOps({ log: () => undefined, runGit: handler })
 }
 
+describe("GitOps", () => {
+  it("resolveDefaultBranch returns undefined on cache hit when there is no remote HEAD", async () => {
+    let calls = 0
+    const git = new GitOps({
+      log: () => undefined,
+      runGit: async (args) => {
+        calls++
+        if (args[0] === "symbolic-ref") throw new Error("no remote HEAD")
+        if (args[0] === "branch" && args[1] === "--show-current") return "main"
+        if (args[0] === "config" && args[1] === "branch.main.remote") return "origin"
+        if (args[0] === "rev-parse" && args[3] === "@{upstream}") throw new Error("no upstream")
+        return ""
+      },
+    })
+
+    // First call sets cache
+    const first = await git.resolveDefaultBranch("/test")
+    expect(first).toBeUndefined()
+    expect(calls).toBeGreaterThan(0)
+
+    // Second call reads from cache
+    const beforeSecondCall = calls
+    const second = await git.resolveDefaultBranch("/test")
+    expect(second).toBeUndefined()
+    // Should not have made any new git calls for the exact same resolution
+    expect(calls).toBe(beforeSecondCall)
+  })
+})
+
 describe("GitStatsPoller", () => {
   it("does not overlap polling runs", async () => {
     let running = 0
diff --git a/packages/kilo-vscode/tests/unit/local-diff.test.ts b/packages/kilo-vscode/tests/unit/local-diff.test.ts
index 0c95da09150..fdcfefede1a 100644
--- a/packages/kilo-vscode/tests/unit/local-diff.test.ts
+++ b/packages/kilo-vscode/tests/unit/local-diff.test.ts
@@ -2,8 +2,9 @@ import { describe, it, expect } from "bun:test"
 import * as fs from "fs/promises"
 import * as os from "os"
 import * as path from "path"
-import { diffSummary, diffFile, generatedLike, MAX_DETAIL_BYTES } from "../../src/agent-manager/local-diff"
+import { diffSummary, diffFile, generatedLike, resolveBase, MAX_DETAIL_BYTES } from "../../src/agent-manager/local-diff"
 import { GitOps } from "../../src/agent-manager/GitOps"
+import { resolveLocalDiffTarget } from "../../src/review-utils"
 
 function git(): GitOps {
   return new GitOps({ log: () => undefined })
@@ -91,6 +92,32 @@ describe("generatedLike", () => {
 })
 
 describe("diffSummary", () => {
+  it("uses candidate local branch fallback when base is empty string and on a feature branch", async () => {
+    await withRepo(async (dir) => {
+      runSync(dir, ["checkout", "-b", "feature"])
+      await fs.writeFile(path.join(dir, "seed.txt"), "seed\nfeature\n")
+      runSync(dir, ["commit", "-am", "feature commit"])
+      const result = await diffSummary(git(), dir, "")
+      const entry = result.find((e) => e.file === "seed.txt")
+      expect(entry?.status).toBe("modified")
+      // Pin the export contract: resolveBase("HEAD") must resolve to a real
+      // candidate branch when one exists locally. If this regresses, the
+      // revert-file fix below also silently regresses.
+      expect(await resolveBase(git(), dir, "HEAD")).toBe("main")
+    })
+  })
+
+  it("uses HEAD as fallback when no candidate branches exist and base is empty", async () => {
+    await withRepo(async (dir) => {
+      // Rename main to something else so it doesn't match candidates
+      runSync(dir, ["branch", "-m", "main", "other"])
+      await fs.writeFile(path.join(dir, "seed.txt"), "seed\nuncommitted\n")
+      const result = await diffSummary(git(), dir, "")
+      const entry = result.find((e) => e.file === "seed.txt")
+      expect(entry?.status).toBe("modified")
+    })
+  })
+
   it("returns empty array when ancestor cannot be resolved", async () => {
     await withRepo(async (dir) => {
       const result = await diffSummary(git(), dir, "nonexistent-branch")
@@ -98,6 +125,18 @@ describe("diffSummary", () => {
     })
   })
 
+  it("does not silently fall back to a candidate when an explicit base is stale", async () => {
+    await withRepo(async (dir) => {
+      // main exists locally, but caller provided a misspelled explicit base.
+      // We must NOT diff against main — merge-base should fail loudly.
+      runSync(dir, ["checkout", "-b", "feature"])
+      await fs.writeFile(path.join(dir, "seed.txt"), "seed\nfeature\n")
+      runSync(dir, ["commit", "-am", "feature commit"])
+      const result = await diffSummary(git(), dir, "typo-main")
+      expect(result).toEqual([])
+    })
+  })
+
   it("reports modified, added, and deleted tracked files", async () => {
     await withRepo(async (dir, base) => {
       // seed.txt is tracked on base. Modify it; add new.txt; delete seed.txt on HEAD.
@@ -272,3 +311,25 @@ describe("diffFile", () => {
     })
   })
 })
+
+describe("resolveLocalDiffTarget + revertFile", () => {
+  it("resolves a real candidate branch so revertFile actually restores the file when there is no remote", async () => {
+    await withRepo(async (dir) => {
+      // No remote; `main` exists locally with the seed commit.
+      runSync(dir, ["checkout", "-b", "feature"])
+      await fs.writeFile(path.join(dir, "seed.txt"), "seed\nfeature\n")
+      runSync(dir, ["commit", "-am", "feature commit"])
+
+      const target = await resolveLocalDiffTarget(git(), () => undefined, dir)
+      expect(target).toBeDefined()
+      // Before the fix this was "HEAD", which made revertFile a no-op.
+      expect(target?.baseBranch).toBe("main")
+
+      const revert = await git().revertFile(dir, target!.baseBranch, "seed.txt", "modified")
+      expect(revert.ok).toBe(true)
+
+      const restored = await fs.readFile(path.join(dir, "seed.txt"), "utf-8")
+      expect(restored).toBe("seed\n")
+    })
+  })
+})