diff --git a/src/backend/pullrequests/index.test.ts b/src/backend/pullrequests/index.test.ts
index e30b5f4..2ff5007 100644
--- a/src/backend/pullrequests/index.test.ts
+++ b/src/backend/pullrequests/index.test.ts
@@ -15,6 +15,7 @@ import {
 	PullRequestError,
 	requestChangesOnPullRequest,
 	unapprovePullRequest,
+	updatePullRequest,
 	withdrawRequestChanges,
 } from "./index.ts";
 
@@ -921,6 +922,103 @@ describe("review action endpoints (approve / unapprove / request-changes / unreq
 	});
 });
 
+describe("updatePullRequest", () => {
+	test("PUTs title only and returns the updated detail", async () => {
+		let seenBody: Record<string, any> | null = null;
+		server.use(
+			http.put(PR_DETAIL_PATH(42), async ({ request }) => {
+				seenBody = (await request.json()) as Record<string, any>;
+				return HttpResponse.json(makePrDetail({ id: 42, title: "new title" }));
+			}),
+		);
+
+		const result = await updatePullRequest(creds, ref, 42, {
+			title: "new title",
+		});
+
+		expect(seenBody!).toEqual({ type: "pullrequest", title: "new title" });
+		expect(seenBody!).not.toHaveProperty("description");
+		expect(result.id).toBe(42);
+		expect(result.title).toBe("new title");
+	});
+
+	test("PUTs description only", async () => {
+		let seenBody: Record<string, any> | null = null;
+		server.use(
+			http.put(PR_DETAIL_PATH(42), async ({ request }) => {
+				seenBody = (await request.json()) as Record<string, any>;
+				return HttpResponse.json(
+					makePrDetail({ id: 42, summary: { raw: "new description" } }),
+				);
+			}),
+		);
+
+		await updatePullRequest(creds, ref, 42, {
+			description: "new description",
+		});
+
+		expect(seenBody!).toEqual({
+			type: "pullrequest",
+			description: "new description",
+		});
+		expect(seenBody!).not.toHaveProperty("title");
+	});
+
+	test("PUTs title and description together when both provided", async () => {
+		let seenBody: Record<string, any> | null = null;
+		server.use(
+			http.put(PR_DETAIL_PATH(42), async ({ request }) => {
+				seenBody = (await request.json()) as Record<string, any>;
+				return HttpResponse.json(makePrDetail({ id: 42 }));
+			}),
+		);
+
+		await updatePullRequest(creds, ref, 42, {
+			title: "t",
+			description: "d",
+		});
+
+		expect(seenBody!).toEqual({
+			type: "pullrequest",
+			title: "t",
+			description: "d",
+		});
+	});
+
+	test("surfaces 4xx cleanly (e.g. editing a closed PR)", async () => {
+		server.use(
+			http.put(PR_DETAIL_PATH(42), () =>
+				HttpResponse.json(
+					{ type: "error", error: { message: "PR is not open" } },
+					{ status: 400 },
+				),
+			),
+		);
+
+		const err = await updatePullRequest(creds, ref, 42, {
+			title: "x",
+		}).catch((e) => e);
+
+		expect(err).toBeInstanceOf(PullRequestError);
+		expect((err as PullRequestError).status).toBe(400);
+	});
+
+	test("surfaces 404 when the PR does not exist", async () => {
+		server.use(
+			http.put(PR_DETAIL_PATH(99), () =>
+				HttpResponse.json({ type: "error" }, { status: 404 }),
+			),
+		);
+
+		const err = await updatePullRequest(creds, ref, 99, {
+			title: "x",
+		}).catch((e) => e);
+
+		expect(err).toBeInstanceOf(PullRequestError);
+		expect((err as PullRequestError).status).toBe(404);
+	});
+});
+
 describe("getPullRequestDiff", () => {
 	const DIFF_PATH = (id: number) =>
 		`${BITBUCKET_BASE}/repositories/ws/repo/pullrequests/${id}/diff`;
diff --git a/src/backend/pullrequests/index.ts b/src/backend/pullrequests/index.ts
index 0d7236f..23e1a01 100644
--- a/src/backend/pullrequests/index.ts
+++ b/src/backend/pullrequests/index.ts
@@ -265,6 +265,58 @@ export async function createPullRequest(
 	return toPullRequestDetail(data as RawPullRequest);
 }
 
+export type UpdatePullRequestInput = {
+	title?: string;
+	description?: string;
+};
+
+/**
+ * PUTs a partial update to a pull request. Bitbucket's spec types the body
+ * as the full `pullrequest` schema and the doc comment only formally
+ * describes "branches or description" updates, but the API accepts partial
+ * bodies in practice for common mutable fields (title, description) — see
+ * docs/bb-notes.md → "Updating a PR".
+ *
+ * The caller is responsible for making sure the PR is in a mutable state
+ * (i.e. OPEN). Non-mutable states surface here as a `PullRequestError`.
+ */
+export async function updatePullRequest(
+	credentials: Credentials,
+	ref: { workspace: string; slug: string },
+	pullRequestId: number,
+	input: UpdatePullRequestInput,
+): Promise<PullRequestDetail> {
+	const client = createBitbucketClient(credentials);
+	const { data, response } = await client.PUT(
+		"/repositories/{workspace}/{repo_slug}/pullrequests/{pull_request_id}",
+		{
+			params: {
+				path: {
+					workspace: ref.workspace,
+					repo_slug: ref.slug,
+					pull_request_id: pullRequestId,
+				},
+			},
+			body: {
+				type: "pullrequest",
+				...(input.title !== undefined ? { title: input.title } : {}),
+				...(input.description !== undefined
+					? { description: input.description }
+					: {}),
+			},
+		},
+	);
+
+	if (!response.ok || !data) {
+		throw new PullRequestError(
+			`Failed to update pull request #${pullRequestId}: HTTP ${response.status}.`,
+			response.status,
+		);
+	}
+
+	return toPullRequestDetail(data as RawPullRequest);
+}
+
 /**
  * Fetches a single pull request by id. Single typed call — the overlay
  * (BBC2-38) gives us typed path params and response shape, so we stay on
diff --git a/src/commands/pullrequest/edit.test.ts b/src/commands/pullrequest/edit.test.ts
new file mode 100644
index 0000000..114a81c
--- /dev/null
+++ b/src/commands/pullrequest/edit.test.ts
@@ -0,0 +1,61 @@
+import { describe, expect, test } from "bun:test";
+import { parseMessage } from "./edit.ts";
+
+describe("parseMessage", () => {
+	test("first line becomes the title; rest after blank line becomes the description", () => {
+		expect(parseMessage("Hello world\n\nA description here.\n")).toEqual({
+			title: "Hello world",
+			description: "A description here.",
+		});
+	});
+
+	test("handles multi-paragraph descriptions verbatim", () => {
+		expect(parseMessage("Title\n\nPara one.\n\nPara two.\n\n* list\n")).toEqual(
+			{
+				title: "Title",
+				description: "Para one.\n\nPara two.\n\n* list",
+			},
+		);
+	});
+
+	test("no description yields an empty string", () => {
+		expect(parseMessage("Just a title\n")).toEqual({
+			title: "Just a title",
+			description: "",
+		});
+	});
+
+	test("leading empty lines are skipped", () => {
+		expect(parseMessage("\n\nTitle\n\nBody\n")).toEqual({
+			title: "Title",
+			description: "Body",
+		});
+	});
+
+	test("trailing blank lines on the title are tolerated (multiple separators)", () => {
+		expect(parseMessage("Title\n\n\n\nBody\n")).toEqual({
+			title: "Title",
+			description: "Body",
+		});
+	});
+
+	test("CRLF line endings are handled", () => {
+		expect(parseMessage("Title\r\n\r\nBody\r\n")).toEqual({
+			title: "Title",
+			description: "Body",
+		});
+	});
+
+	test("empty input returns null (caller treats as abort)", () => {
+		expect(parseMessage("")).toBeNull();
+		expect(parseMessage("\n\n\n")).toBeNull();
+		expect(parseMessage("   \n\t\n")).toBeNull();
+	});
+
+	test("title is trimmed", () => {
+		expect(parseMessage("  Spacey title  \n\nbody\n")).toEqual({
+			title: "Spacey title",
+			description: "body",
+		});
+	});
+});
diff --git a/src/commands/pullrequest/edit.ts b/src/commands/pullrequest/edit.ts
new file mode 100644
index 0000000..3123ad6
--- /dev/null
+++ b/src/commands/pullrequest/edit.ts
@@ -0,0 +1,164 @@
+import {
+	getPullRequest,
+	type PullRequestDetail,
+	PullRequestError,
+	type PullRequestState,
+	updatePullRequest,
+} from "../../backend/pullrequests/index.ts";
+import { loadConfigOrExit } from "../../shared/config/index.ts";
+import { EditorError, openEditor } from "../../shared/editor/index.ts";
+import type { Renderer } from "../../shared/renderer/index.ts";
+import {
+	RepositoryResolutionError,
+	resolveRepository,
+} from "../../shared/repository/index.ts";
+import { resolveCurrentPullRequestId } from "./current.ts";
+
+export type PullRequestEditOptions = {
+	repository?: string;
+	title?: string;
+	description?: string;
+};
+
+const IMMUTABLE_STATES: ReadonlySet<PullRequestState> = new Set([
+	"MERGED",
+	"DECLINED",
+	"SUPERSEDED",
+]);
+
+/**
+ * Updates a PR's title and/or description. Without flags, falls through to
+ * $EDITOR pre-filled with the PR's current title (first line), a blank
+ * separator, and the current description. Classic git-style message layout.
+ *
+ * No-op guard: if the resolved new values match the existing ones, skip
+ * the PUT entirely. Saves a round trip and avoids a pointless "updated"
+ * confirmation when the editor was closed without changes.
+ */
+export async function runPullRequestEdit(
+	renderer: Renderer,
+	idArg: string | undefined,
+	options: PullRequestEditOptions,
+): Promise<void> {
+	const config = await loadConfigOrExit(renderer);
+
+	try {
+		const ref = await resolveRepository({ override: options.repository });
+		const id = await resolveCurrentPullRequestId(idArg, {
+			renderer,
+			config,
+			ref,
+			commandName: "edit",
+		});
+
+		const current = await getPullRequest(config, ref, id);
+		if (IMMUTABLE_STATES.has(current.state)) {
+			renderer.error(
+				`Pull request #${id} is ${current.state.toLowerCase()}; cannot edit.`,
+			);
+			process.exit(1);
+		}
+
+		const resolved = await resolveFields(renderer, current, options);
+		if (resolved === null) {
+			renderer.message(`No changes to pull request #${id}.`);
+			return;
+		}
+
+		const updated = await updatePullRequest(config, ref, id, resolved);
+
+		if (renderer.json) {
+			renderer.detail(updated, []);
+		} else {
+			renderer.message(`Updated pull request #${id}: ${updated.url}`);
+		}
+	} catch (err) {
+		if (
+			err instanceof RepositoryResolutionError ||
+			err instanceof PullRequestError ||
+			err instanceof EditorError
+		) {
+			renderer.error(err.message);
+			process.exit(1);
+		}
+		throw err;
+	}
+}
+
+/**
+ * Resolves the fields to PUT.
+ *
+ * - One or both flags set → use them; only include fields that actually
+ *   differ from the current PR (so e.g. `--title "same as before"` is a
+ *   no-op and doesn't generate a PUT).
+ * - No flags → open editor pre-filled; parse back the same way. Aborts
+ *   with a clear error on empty output.
+ *
+ * Returns `null` when there's nothing to send (either both flags matched
+ * current state, or the editor came back unchanged).
+ */
+async function resolveFields(
+	renderer: Renderer,
+	current: PullRequestDetail,
+	options: PullRequestEditOptions,
+): Promise<{ title?: string; description?: string } | null> {
+	if (options.title !== undefined || options.description !== undefined) {
+		const patch: { title?: string; description?: string } = {};
+		if (options.title !== undefined && options.title !== current.title) {
+			patch.title = options.title;
+		}
+		if (
+			options.description !== undefined &&
+			options.description !== current.description
+		) {
+			patch.description = options.description;
+		}
+		return Object.keys(patch).length > 0 ? patch : null;
+	}
+
+	// Editor fallback.
+	const initial = `${current.title}\n\n${current.description}`;
+	const raw = await openEditor(initial);
+	const parsed = parseMessage(raw);
+	if (parsed === null) {
+		renderer.error("Edit aborted: title is empty.");
+		process.exit(1);
+	}
+
+	const patch: { title?: string; description?: string } = {};
+	if (parsed.title !== current.title) patch.title = parsed.title;
+	if (parsed.description !== current.description) {
+		patch.description = parsed.description;
+	}
+	return Object.keys(patch).length > 0 ? patch : null;
+}
+
+/**
+ * Parses a git-style message buffer: first non-empty line is the title,
+ * everything after the first blank line is the description. Returns null
+ * when the title ends up empty, which the caller treats as "abort".
+ *
+ * Preserves trailing content verbatim so multi-paragraph descriptions
+ * survive the round trip.
+ */
+export function parseMessage(
+	raw: string,
+): { title: string; description: string } | null {
+	// Find the first non-empty line → that's the title. Everything after
+	// the first blank line following the title is the description.
+	const lines = raw.split(/\r?\n/);
+	let i = 0;
+	while (i < lines.length && lines[i]!.trim() === "") i++;
+	if (i >= lines.length) return null;
+
+	const title = lines[i]!.trim();
+	if (!title) return null;
+
+	// Skip the title line and any immediately following blank separator
+	// lines so the description doesn't start with an empty line.
+	i++;
+	while (i < lines.length && lines[i]!.trim() === "") i++;
+
+	const description = lines.slice(i).join("\n").trimEnd();
+	return { title, description };
+}
diff --git a/src/commands/pullrequest/index.ts b/src/commands/pullrequest/index.ts
index eb4197f..9581a45 100644
--- a/src/commands/pullrequest/index.ts
+++ b/src/commands/pullrequest/index.ts
@@ -3,6 +3,7 @@ import { withRenderer } from "../../shared/renderer/commander.ts";
 import { runPullRequestComment } from "./comment.ts";
 import { runPullRequestCreate } from "./create.ts";
 import { runPullRequestDiff } from "./diff.ts";
+import { runPullRequestEdit } from "./edit.ts";
 import { runPullRequestList } from "./list.ts";
 import { runPullRequestReview } from "./review.ts";
 import { runPullRequestView } from "./view.ts";
@@ -86,6 +87,19 @@ export function registerPullRequestCommands(program: Command): void {
 		)
 		.action(withRenderer(runPullRequestDiff));
 
+	pr.command("edit")
+		.description(
+			"Update a pull request's title and/or description (defaults to the PR for the current branch)",
+		)
+		.argument("[id]", "Pull request number")
+		.option(
+			"-R, --repository <workspace/repo>",
+			"Override repository detection",
+		)
+		.option("-t, --title <title>", "New title")
+		.option("-d, --description <description>", "New description")
+		.action(withRenderer(runPullRequestEdit));
+
 	pr.command("review")
 		.description(
 			"Submit a review on a pull request (defaults to the PR for the current branch)",