diff --git a/packages/app/src/components/ui/combobox-options.test.ts b/packages/app/src/components/ui/combobox-options.test.ts
index 57396e163..34e076ced 100644
--- a/packages/app/src/components/ui/combobox-options.test.ts
+++ b/packages/app/src/components/ui/combobox-options.test.ts
@@ -88,6 +88,39 @@ describe("filterAndRankComboboxOptions", () => {
   it("returns empty when nothing matches", () => {
     expect(filterAndRankComboboxOptions(options, "zzz")).toEqual([]);
   });
+
+  it("ranks word-boundary matches above mid-word substring matches", () => {
+    const items = [
+      { id: "happy", label: "happy" },
+      { id: "a/py", label: "a/py" },
+    ];
+    const result = filterAndRankComboboxOptions(items, "py");
+    expect(result.map((o) => o.id)).toEqual(["a/py", "happy"]);
+  });
+
+  it("interleaves mixed branches and PRs by match quality", () => {
+    const items = [
+      { id: "branch:feat/api-login", label: "feat/api-login" },
+      { id: "branch:feat/pi-direct-sdk", label: "feat/pi-direct-sdk" },
+      { id: "github-pr:202", label: "#202 feat(server): replace Pi ACP with direct SDK provider" },
+      { id: "github-pr:355", label: "#355 feat: add LaTeX math formula rendering" },
+    ];
+    const result = filterAndRankComboboxOptions(items, "pi");
+    expect(result.map((o) => o.id)).toEqual([
+      "branch:feat/pi-direct-sdk",
+      "github-pr:202",
+      "branch:feat/api-login",
+    ]);
+  });
+
+  it("ranks PR-number matches via word-boundary on #", () => {
+    const items = [
+      { id: "github-pr:202", label: "#202 some title" },
+      { id: "github-pr:1202", label: "#1202 another title" },
+    ];
+    const result = filterAndRankComboboxOptions(items, "202");
+    expect(result.map((o) => o.id)).toEqual(["github-pr:202", "github-pr:1202"]);
+  });
 });
 
 describe("combobox above-search ordering", () => {
diff --git a/packages/app/src/components/ui/combobox-options.ts b/packages/app/src/components/ui/combobox-options.ts
index 8fc41832d..407c5bc99 100644
--- a/packages/app/src/components/ui/combobox-options.ts
+++ b/packages/app/src/components/ui/combobox-options.ts
@@ -1,3 +1,5 @@
+import { compareMatchScores, type MatchScore, scoreMatch } from "../../utils/score-match";
+
 export type ComboboxOptionKind = "directory" | "file";
 
 export interface ComboboxOptionModel {
@@ -7,6 +9,23 @@ export interface ComboboxOptionModel {
   kind?: ComboboxOptionKind;
 }
 
+const DESCRIPTION_FALLBACK_TIER = 99;
+
+function scoreOption(opt: ComboboxOptionModel, search: string): MatchScore | null {
+  const labelScore = scoreMatch(search, opt.label);
+  const idScore = scoreMatch(search, opt.id);
+  let best: MatchScore | null = null;
+  if (labelScore) best = labelScore;
+  if (idScore && (!best || compareMatchScores(idScore, best) < 0)) {
+    best = idScore;
+  }
+  if (best) return best;
+  if (opt.description && opt.description.toLowerCase().includes(search)) {
+    return { tier: DESCRIPTION_FALLBACK_TIER, offset: 0 };
+  }
+  return null;
+}
+
 export interface BuildVisibleComboboxOptionsInput {
   options: ComboboxOptionModel[];
   searchQuery: string;
@@ -40,21 +59,17 @@ export function filterAndRankComboboxOptions(
   search: string,
 ): ComboboxOptionModel[] {
   if (!search) return options;
-  return options
-    .filter(
-      (opt) =>
-        opt.label.toLowerCase().includes(search) ||
-        opt.id.toLowerCase().includes(search) ||
-        opt.description?.toLowerCase().includes(search),
-    )
-    .sort((a, b) => {
-      const aPrefix =
-        a.label.toLowerCase().startsWith(search) || a.id.toLowerCase().startsWith(search);
-      const bPrefix =
-        b.label.toLowerCase().startsWith(search) || b.id.toLowerCase().startsWith(search);
-      if (aPrefix !== bPrefix) return aPrefix ? -1 : 1;
-      return 0;
-    });
+  const scored: { opt: ComboboxOptionModel; score: MatchScore }[] = [];
+  for (const opt of options) {
+    const score = scoreOption(opt, search);
+    if (score) scored.push({ opt, score });
+  }
+  scored.sort((a, b) => {
+    const cmp = compareMatchScores(a.score, b.score);
+    if (cmp !== 0) return cmp;
+    return a.opt.label.localeCompare(b.opt.label);
+  });
+  return scored.map((entry) => entry.opt);
 }
 
 export function buildVisibleComboboxOptions(
diff --git a/packages/app/src/utils/score-match.test.ts b/packages/app/src/utils/score-match.test.ts
new file mode 100644
index 000000000..88177a2e7
--- /dev/null
+++ b/packages/app/src/utils/score-match.test.ts
@@ -0,0 +1,78 @@
+import { describe, expect, it } from "vitest";
+
+import { compareMatchScores, scoreMatch } from "./score-match";
+
+describe("scoreMatch", () => {
+  it("returns tier 0 for empty query", () => {
+    expect(scoreMatch("", "anything")).toEqual({ tier: 0, offset: 0 });
+  });
+
+  it("returns tier 0 for exact match ignoring case", () => {
+    expect(scoreMatch("pi", "pi")).toEqual({ tier: 0, offset: 0 });
+    expect(scoreMatch("PI", "pi")).toEqual({ tier: 0, offset: 0 });
+    expect(scoreMatch("Pi", "pI")).toEqual({ tier: 0, offset: 0 });
+  });
+
+  it("returns tier 1 for whole-word match at start", () => {
+    expect(scoreMatch("feat", "feat/pi-direct-sdk")).toEqual({ tier: 1, offset: 0 });
+  });
+
+  it("returns tier 1 for whole-word match in middle (word boundaries on both sides)", () => {
+    expect(scoreMatch("pi", "feat/pi-direct-sdk")).toEqual({ tier: 1, offset: 5 });
+    expect(scoreMatch("pi", "a b pi c d")).toEqual({ tier: 1, offset: 4 });
+  });
+
+  it("returns tier 2 for string prefix that does not complete a word", () => {
+    expect(scoreMatch("par", "party")).toEqual({ tier: 2, offset: 0 });
+  });
+
+  it("returns tier 3 for word-boundary start that does not complete a word", () => {
+    expect(scoreMatch("par", "a/party")).toEqual({ tier: 3, offset: 2 });
+  });
+
+  it("returns tier 4 for substring inside a word", () => {
+    expect(scoreMatch("art", "party")).toEqual({ tier: 4, offset: 1 });
+  });
+
+  it("returns null when query is not found", () => {
+    expect(scoreMatch("xyz", "feat/pi-direct-sdk")).toBeNull();
+  });
+
+  it("picks the best tier across multiple occurrences", () => {
+    expect(scoreMatch("ab", "xabxab-yy")).toEqual({ tier: 4, offset: 1 });
+    expect(scoreMatch("ab", "xxab x-ab-y")).toEqual({ tier: 1, offset: 7 });
+  });
+
+  it("prefers earlier offset when tiers are equal", () => {
+    expect(scoreMatch("pi", "pi-a pi-b")).toEqual({ tier: 1, offset: 0 });
+  });
+
+  it("treats common separators as word boundaries", () => {
+    expect(scoreMatch("pi", "x/pi")).toEqual({ tier: 1, offset: 2 });
+    expect(scoreMatch("pi", "x-pi")).toEqual({ tier: 1, offset: 2 });
+    expect(scoreMatch("pi", "x_pi")).toEqual({ tier: 1, offset: 2 });
+    expect(scoreMatch("pi", "x pi")).toEqual({ tier: 1, offset: 2 });
+    expect(scoreMatch("pi", "x.pi")).toEqual({ tier: 1, offset: 2 });
+    expect(scoreMatch("pi", "x:pi")).toEqual({ tier: 1, offset: 2 });
+    expect(scoreMatch("202", "#202 feat")).toEqual({ tier: 1, offset: 1 });
+  });
+
+  it("scores PR-title-shaped text realistically", () => {
+    const pr202 = "#202 feat(server): replace Pi ACP with direct SDK provider";
+    expect(scoreMatch("pi", pr202)?.tier).toBe(1);
+    expect(scoreMatch("202", pr202)).toEqual({ tier: 1, offset: 1 });
+    expect(scoreMatch("replace", pr202)?.tier).toBe(1);
+  });
+});
+
+describe("compareMatchScores", () => {
+  it("sorts by tier ascending", () => {
+    expect(compareMatchScores({ tier: 1, offset: 10 }, { tier: 2, offset: 0 })).toBeLessThan(0);
+    expect(compareMatchScores({ tier: 3, offset: 0 }, { tier: 1, offset: 99 })).toBeGreaterThan(0);
+  });
+
+  it("tie-breaks by offset ascending at the same tier", () => {
+    expect(compareMatchScores({ tier: 1, offset: 0 }, { tier: 1, offset: 5 })).toBeLessThan(0);
+    expect(compareMatchScores({ tier: 1, offset: 5 }, { tier: 1, offset: 5 })).toBe(0);
+  });
+});
diff --git a/packages/app/src/utils/score-match.ts b/packages/app/src/utils/score-match.ts
new file mode 100644
index 000000000..790f95cfe
--- /dev/null
+++ b/packages/app/src/utils/score-match.ts
@@ -0,0 +1,47 @@
+export interface MatchScore {
+  tier: number;
+  offset: number;
+}
+
+function isWordBoundaryChar(ch: string | undefined): boolean {
+  if (ch === undefined) return true;
+  return !/[a-z0-9]/.test(ch);
+}
+
+export function scoreMatch(query: string, text: string): MatchScore | null {
+  if (!query) return { tier: 0, offset: 0 };
+  const q = query.toLowerCase();
+  const t = text.toLowerCase();
+  if (t === q) return { tier: 0, offset: 0 };
+
+  let best: MatchScore | null = null;
+  let pos = 0;
+  while (pos <= t.length - q.length) {
+    const found = t.indexOf(q, pos);
+    if (found === -1) break;
+    const before = found > 0 ? t[found - 1] : undefined;
+    const after = t[found + q.length];
+    const startsAtBoundary = found === 0 || isWordBoundaryChar(before);
+    const endsAtBoundary = after === undefined || isWordBoundaryChar(after);
+    let tier: number;
+    if (startsAtBoundary && endsAtBoundary) {
+      tier = 1;
+    } else if (found === 0) {
+      tier = 2;
+    } else if (startsAtBoundary) {
+      tier = 3;
+    } else {
+      tier = 4;
+    }
+    if (!best || tier < best.tier || (tier === best.tier && found < best.offset)) {
+      best = { tier, offset: found };
+    }
+    pos = found + 1;
+  }
+  return best;
+}
+
+export function compareMatchScores(a: MatchScore, b: MatchScore): number {
+  if (a.tier !== b.tier) return a.tier - b.tier;
+  return a.offset - b.offset;
+}