backnotprop
diff --git a/‎AGENTS.md‎
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diff --git a/‎apps/hook/server/index.ts‎
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diff --git a/‎apps/marketing/src/content/docs/commands/code-review.md‎
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diff --git a/‎apps/marketing/src/content/docs/guides/ai-code-review.md‎
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diff --git a/‎apps/pi-extension/plannotator-browser.ts‎
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diff --git a/‎apps/pi-extension/server/agent-jobs.ts‎
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diff --git a/‎apps/pi-extension/server/pr.ts‎
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@@ -250,6 +250,9 @@ During normal plan review, an Archive sidebar tab provides the same browsing via
 | `/api/agents/jobs` | POST | Launch an agent job (body: `{ provider, command, label }`) |
 | `/api/agents/jobs` | DELETE | Kill all running agent jobs |
 | `/api/agents/jobs/:id` | DELETE | Kill a specific agent job |
+| `/api/pr-diff-scope` | POST | Switch between layer and full-stack diff scope |
+| `/api/pr-list` | GET | List PRs for the current repo (cached 30s) |
+| `/api/pr-switch` | POST | Switch to a different PR in-place (body: `{ url }`) |
 | `/api/tour/:jobId` | GET | Fetch Code Tour result (greeting, stops, checklist) for a completed tour job |
 | `/api/tour/:jobId/checklist` | PUT | Persist checklist item state for a Code Tour |
 
 
@@ -69,6 +69,7 @@ import { stripAtPrefix, resolveAtReference } from "@plannotator/shared/at-refere
 import { htmlToMarkdown } from "@plannotator/shared/html-to-markdown";
 import { urlToMarkdown } from "@plannotator/shared/url-to-markdown";
 import { fetchRef, createWorktree, removeWorktree, ensureObjectAvailable } from "@plannotator/shared/worktree";
+import { createWorktreePool, type WorktreePool } from "@plannotator/shared/worktree-pool";
 import { parsePRUrl, checkPRAuth, fetchPR, getCliName, getCliInstallUrl, getMRLabel, getMRNumberLabel, getDisplayRepo } from "@plannotator/server/pr";
 import { writeRemoteShareLink } from "@plannotator/server/share-url";
 import { resolveMarkdownFile, resolveUserPath, hasMarkdownFiles } from "@plannotator/shared/resolve-file";
@@ -293,6 +294,7 @@ if (args[0] === "sessions") {
   let prMetadata: Awaited<ReturnType<typeof fetchPR>>["metadata"] | undefined;
   let initialDiffType: DiffType | undefined;
   let agentCwd: string | undefined;
+  let worktreePool: WorktreePool | undefined;
   let worktreeCleanup: (() => void | Promise<void>) | undefined;
 
   if (isPRMode) {
@@ -337,6 +339,7 @@ if (args[0] === "sessions") {
     if (useLocal && prMetadata) {
       // Hoisted so catch block can clean up partially-created directories
       let localPath: string | undefined;
+      let sessionDir: string | undefined;
       try {
         const repoDir = process.cwd();
         const identifier = prMetadata.platform === "github"
@@ -345,7 +348,9 @@ if (args[0] === "sessions") {
         const suffix = Math.random().toString(36).slice(2, 8);
         // Resolve tmpdir to its real path — on macOS, tmpdir() returns /var/folders/...
         // but processes report /private/var/folders/... which breaks path stripping.
-        localPath = path.join(realpathSync(tmpdir()), `plannotator-pr-${identifier}-${suffix}`);
+        sessionDir = path.join(realpathSync(tmpdir()), `plannotator-pr-${identifier}-${suffix}`);
+        const prNumber = prMetadata.platform === "github" ? prMetadata.number : prMetadata.iid;
+        localPath = path.join(sessionDir, "pool", `pr-${prNumber}`);
         const fetchRefStr = prMetadata.platform === "github"
           ? `refs/pull/${prMetadata.number}/head`
           : `refs/merge-requests/${prMetadata.iid}/head`;
@@ -393,9 +398,18 @@ if (args[0] === "sessions") {
             cwd: repoDir,
           });
 
-          worktreeCleanup = () => removeWorktree(gitRuntime, localPath, { force: true, cwd: repoDir });
+          worktreeCleanup = async () => {
+            if (worktreePool) await worktreePool.cleanup(gitRuntime);
+            try { rmSync(sessionDir, { recursive: true, force: true }); } catch {}
+          };
           process.once("exit", () => {
-            try { Bun.spawnSync(["git", "worktree", "remove", "--force", localPath]); } catch {}
+            // Best-effort sync cleanup: remove each pool worktree from git, then rm session dir
+            try {
+              for (const entry of worktreePool?.entries() ?? []) {
+                Bun.spawnSync(["git", "worktree", "remove", "--force", entry.path], { cwd: repoDir });
+              }
+            } catch {}
+            try { Bun.spawnSync(["rm", "-rf", sessionDir]); } catch {}
           });
         } else {
           // ── Cross-repo: shallow clone + fetch PR head ──
@@ -443,23 +457,29 @@ if (args[0] === "sessions") {
           Bun.spawnSync(["git", "branch", "--", prMetadata.baseBranch, prMetadata.baseSha], { cwd: localPath, stderr: "pipe" });
           Bun.spawnSync(["git", "update-ref", `refs/remotes/origin/${prMetadata.baseBranch}`, prMetadata.baseSha], { cwd: localPath, stderr: "pipe" });
 
-          worktreeCleanup = () => { try { rmSync(localPath, { recursive: true, force: true }); } catch {} };
+          worktreeCleanup = () => { try { rmSync(sessionDir, { recursive: true, force: true }); } catch {} };
           process.once("exit", () => {
-            try { Bun.spawnSync(["rm", "-rf", localPath]); } catch {}
+            try { Bun.spawnSync(["rm", "-rf", sessionDir]); } catch {}
           });
         }
 
         // --local only provides a sandbox path for agent processes.
         // Do NOT set gitContext — that would contaminate the diff pipeline.
         agentCwd = localPath;
 
+        // Create worktree pool with the initial PR as the first entry
+        worktreePool = createWorktreePool(
+          { sessionDir, repoDir, isSameRepo },
+          { path: localPath, prUrl: prMetadata.url, number: prNumber, ready: true },
+        );
+
         console.error(`Local checkout ready at ${localPath}`);
       } catch (err) {
         console.error(`Warning: --local failed, falling back to remote diff`);
         console.error(err instanceof Error ? err.message : String(err));
-        // Clean up partially-created directory (clone may have succeeded before fetch/checkout failed)
-        if (localPath) try { rmSync(localPath, { recursive: true, force: true }); } catch {}
+        if (sessionDir) try { rmSync(sessionDir, { recursive: true, force: true }); } catch {}
         agentCwd = undefined;
+        worktreePool = undefined;
         worktreeCleanup = undefined;
       }
     }
@@ -485,6 +505,7 @@ if (args[0] === "sessions") {
     gitContext,
     prMetadata,
     agentCwd,
+    worktreePool,
     sharingEnabled,
     shareBaseUrl,
     htmlContent: reviewHtmlContent,
 
@@ -24,6 +24,8 @@ The `/plannotator-review` command opens an interactive code review UI for your l
 
 PR review uses the `gh` CLI for authentication, so private repos work automatically if you're authenticated with `gh auth login`.
 
+GitLab merge request URLs are also supported when the `glab` CLI is installed and authenticated.
+
 ## How it works
 
 **Local review:**
@@ -60,6 +62,14 @@ Send Feedback → PR context included in feedback
 Approve → "LGTM" sent to agent
 ```
 
+## Stacked PRs and MRs
+
+When a PR or MR targets a non-default branch, Plannotator marks it as stacked in the review header. The default view remains **Layer**, which matches the platform diff and is the safe mode for posting inline review comments.
+
+If Plannotator has a local checkout for the PR or MR, the header also offers **Full stack**. Full stack shows everything from the repository default branch through the current checked-out head, which helps you understand the whole chain before reviewing the current layer.
+
+Platform posting is intentionally limited to **Layer** because GitHub and GitLab inline comments are anchored to the PR or MR's own diff. Use **Full stack** for comprehension and agent review, then switch back to **Layer** before posting to the platform.
+
 ## Switching diff types
 
 By default the review opens showing uncommitted changes, but you can switch what you're comparing using the diff type dropdown in the toolbar. The available options are:
 
@@ -24,6 +24,13 @@ Both integrations are derived from official tooling. Claude's review model is ba
 
 For PR reviews, a temporary local checkout is created by default so the agent has file access beyond the diff. Pass `--no-local` to skip this.
 
+For stacked PRs and MRs, the review header lets you choose what the agent sees:
+
+- **Layer** reviews only the current PR or MR relative to its parent branch.
+- **Full stack** reviews the cumulative diff from the repository default branch through the current head.
+
+Layer review is best for avoiding duplicate feedback on parent PRs. Full stack review is useful for integration issues that only appear when the whole chain is considered together. Posting inline comments back to GitHub or GitLab stays limited to Layer because platform comments must anchor to the platform diff.
+
 ## Findings
 
 Each finding includes a file path, line range, description, and severity or priority. Claude findings also include a reasoning trace that explains how the issue was verified.
 
@@ -2,6 +2,7 @@ import { existsSync, readFileSync, realpathSync, rmSync, statSync } from "node:f
 import { dirname, join, resolve } from "node:path";
 import { tmpdir } from "node:os";
 import { spawnSync } from "node:child_process";
+import { createWorktreePool, type WorktreePool } from "./generated/worktree-pool.js";
 import { fileURLToPath } from "node:url";
 import type { ExtensionContext } from "@mariozechner/pi-coding-agent";
 import {
@@ -183,6 +184,7 @@ export async function openCodeReview(
 	let agentCwd: string | undefined;
 	let initialBase: string | undefined;
 	let worktreeCleanup: (() => void | Promise<void>) | undefined;
+	let worktreePool: WorktreePool | undefined;
 	let exitHandler: (() => void) | undefined;
 
 	if (isPRMode && urlArg) {
@@ -218,13 +220,16 @@ export async function openCodeReview(
 
 		// Create local worktree for agent file access (--local is the default for PR reviews)
 		let localPath: string | undefined;
+		let sessionDir: string | undefined;
 		try {
 			const repoDir = options.cwd ?? ctx.cwd;
 			const identifier = prMetadata.platform === "github"
 				? `${prMetadata.owner}-${prMetadata.repo}-${prMetadata.number}`
 				: `${prMetadata.projectPath.replace(/\//g, "-")}-${prMetadata.iid}`;
 			const suffix = Math.random().toString(36).slice(2, 8);
-			localPath = join(realpathSync(tmpdir()), `plannotator-pr-${identifier}-${suffix}`);
+			const prNumber = prMetadata.platform === "github" ? prMetadata.number : prMetadata.iid;
+			sessionDir = join(realpathSync(tmpdir()), `plannotator-pr-${identifier}-${suffix}`);
+			localPath = join(sessionDir, "pool", `pr-${prNumber}`);
 			const fetchRefStr = prMetadata.platform === "github"
 				? `refs/pull/${prMetadata.number}/head`
 				: `refs/merge-requests/${prMetadata.iid}/head`;
@@ -266,14 +271,19 @@ export async function openCodeReview(
 					cwd: repoDir,
 				});
 
-				const worktreePath = localPath;
 				const wtRepoDir = repoDir;
 				exitHandler = () => {
-					try { spawnSync("git", ["worktree", "remove", "--force", worktreePath], { cwd: wtRepoDir }); } catch {}
+					try {
+						for (const entry of worktreePool?.entries() ?? []) {
+							spawnSync("git", ["worktree", "remove", "--force", entry.path], { cwd: wtRepoDir });
+						}
+					} catch {}
+					if (sessionDir) try { rmSync(sessionDir, { recursive: true, force: true }); } catch {}
 				};
-				worktreeCleanup = () => {
+				worktreeCleanup = async () => {
 					if (exitHandler) { process.removeListener("exit", exitHandler); exitHandler = undefined; }
-					return removeWorktree(reviewRuntime, worktreePath, { force: true, cwd: wtRepoDir });
+					if (worktreePool) await worktreePool.cleanup(reviewRuntime);
+					if (sessionDir) try { rmSync(sessionDir, { recursive: true, force: true }); } catch {}
 				};
 				process.once("exit", exitHandler);
 			} else {
@@ -312,25 +322,29 @@ export async function openCodeReview(
 				await reviewRuntime.runGit(["branch", "--", prMetadata.baseBranch, prMetadata.baseSha], { cwd: localPath });
 				await reviewRuntime.runGit(["update-ref", `refs/remotes/origin/${prMetadata.baseBranch}`, prMetadata.baseSha], { cwd: localPath });
 
-				const clonePath = localPath;
 				exitHandler = () => {
-					try { rmSync(clonePath, { recursive: true, force: true }); } catch {}
+					if (sessionDir) try { rmSync(sessionDir, { recursive: true, force: true }); } catch {}
 				};
 				worktreeCleanup = () => {
 					if (exitHandler) { process.removeListener("exit", exitHandler); exitHandler = undefined; }
-					try { rmSync(clonePath, { recursive: true, force: true }); } catch {}
+					if (sessionDir) try { rmSync(sessionDir, { recursive: true, force: true }); } catch {}
 				};
 				process.once("exit", exitHandler);
 			}
 
 			agentCwd = localPath;
+			worktreePool = createWorktreePool(
+				{ sessionDir: sessionDir!, repoDir, isSameRepo },
+				{ path: localPath, prUrl: prMetadata.url, number: prNumber, ready: true },
+			);
 			console.error(`Local checkout ready at ${localPath}`);
 		} catch (err) {
 			console.error("Warning: local worktree creation failed, falling back to remote diff");
 			console.error(err instanceof Error ? err.message : String(err));
 			if (exitHandler) { process.removeListener("exit", exitHandler); exitHandler = undefined; }
-			if (localPath) try { rmSync(localPath, { recursive: true, force: true }); } catch {}
+			if (sessionDir) try { rmSync(sessionDir, { recursive: true, force: true }); } catch {}
 			agentCwd = undefined;
+			worktreePool = undefined;
 			worktreeCleanup = undefined;
 		}
 	} else {
@@ -359,6 +373,7 @@ export async function openCodeReview(
 		initialBase,
 		prMetadata,
 		agentCwd,
+		worktreePool,
 		htmlContent: reviewHtmlContent,
 		sharingEnabled: process.env.PLANNOTATOR_SHARE !== "disabled",
 		shareBaseUrl: process.env.PLANNOTATOR_SHARE_URL || undefined,
 
@@ -73,6 +73,10 @@ export interface AgentJobHandlerOptions {
 		reasoningEffort?: string;
 		/** Whether Codex fast mode was enabled. */
 		fastMode?: boolean;
+		/** PR URL at launch time. */
+		prUrl?: string;
+		/** PR diff scope at launch time. */
+		diffScope?: string;
 		/** Diff context snapshot at launch (stored on AgentJobInfo for per-job "Copy All"). */
 		diffContext?: AgentJobInfo["diffContext"];
 	} | null>;
@@ -120,7 +124,7 @@ export function createAgentJobHandler(options: AgentJobHandlerOptions) {
 		command: string[],
 		label: string,
 		outputPath?: string,
-		spawnOptions?: { captureStdout?: boolean; stdinPrompt?: string; cwd?: string; prompt?: string; engine?: string; model?: string; effort?: string; reasoningEffort?: string; fastMode?: boolean; diffContext?: AgentJobInfo["diffContext"] },
+		spawnOptions?: { captureStdout?: boolean; stdinPrompt?: string; cwd?: string; prompt?: string; engine?: string; model?: string; effort?: string; reasoningEffort?: string; fastMode?: boolean; prUrl?: string; diffScope?: string; diffContext?: AgentJobInfo["diffContext"] },
 	): AgentJobInfo {
 		const id = crypto.randomUUID();
 		const source = jobSource(id);
@@ -139,6 +143,8 @@ export function createAgentJobHandler(options: AgentJobHandlerOptions) {
 			...(spawnOptions?.effort && { effort: spawnOptions.effort }),
 			...(spawnOptions?.reasoningEffort && { reasoningEffort: spawnOptions.reasoningEffort }),
 			...(spawnOptions?.fastMode && { fastMode: spawnOptions.fastMode }),
+			...(spawnOptions?.prUrl && { prUrl: spawnOptions.prUrl }),
+			...(spawnOptions?.diffScope && { diffScope: spawnOptions.diffScope }),
 			...(spawnOptions?.diffContext && { diffContext: spawnOptions.diffContext }),
 		};
 
@@ -422,6 +428,8 @@ export function createAgentJobHandler(options: AgentJobHandlerOptions) {
 					let jobEffort: string | undefined;
 					let jobReasoningEffort: string | undefined;
 					let jobFastMode: boolean | undefined;
+					let jobPrUrl: string | undefined;
+					let jobDiffScope: string | undefined;
 					let jobDiffContext: AgentJobInfo["diffContext"] | undefined;
 					if (options.buildCommand) {
 						// Thread config from POST body to buildCommand
@@ -445,6 +453,8 @@ export function createAgentJobHandler(options: AgentJobHandlerOptions) {
 							jobEffort = built.effort;
 							jobReasoningEffort = built.reasoningEffort;
 							jobFastMode = built.fastMode;
+							jobPrUrl = built.prUrl;
+							jobDiffScope = built.diffScope;
 							jobDiffContext = built.diffContext;
 						}
 					}
@@ -464,6 +474,8 @@ export function createAgentJobHandler(options: AgentJobHandlerOptions) {
 						effort: jobEffort,
 						reasoningEffort: jobReasoningEffort,
 						fastMode: jobFastMode,
+						prUrl: jobPrUrl,
+						diffScope: jobDiffScope,
 						diffContext: jobDiffContext,
 					});
 					json(res, { job }, 201);
 
@@ -11,11 +11,16 @@ import {
 	fetchPR as fetchPRCore,
 	fetchPRFileContent as fetchPRFileContentCore,
 	fetchPRViewedFiles as fetchPRViewedFilesCore,
+	fetchPRStack as fetchPRStackCore,
+	fetchPRList as fetchPRListCore,
 	getUser as getUserCore,
 	markPRFilesViewed as markPRFilesViewedCore,
+	type PRMetadata,
 	type PRRef,
 	type PRReviewFileComment,
 	type PRRuntime,
+	type PRStackTree,
+	type PRListItem,
 	parsePRUrl as parsePRUrlCore,
 	submitPRReview as submitPRReviewCore,
 } from "../generated/pr-provider.js";
@@ -104,3 +109,16 @@ export function markPRFilesViewed(
 ): Promise<void> {
 	return markPRFilesViewedCore(prRuntime, ref, prNodeId, filePaths, viewed);
 }
+
+export function fetchPRStack(
+	ref: PRRef,
+	metadata: PRMetadata,
+): Promise<PRStackTree | null> {
+	return fetchPRStackCore(prRuntime, ref, metadata);
+}
+
+export function fetchPRList(
+	ref: PRRef,
+): Promise<PRListItem[]> {
+	return fetchPRListCore(prRuntime, ref);
+}