diff --git a/plugins/web-ui/src/contexts.ts b/plugins/web-ui/src/contexts.ts
index b3da5d1dc..44da7b7ed 100644
--- a/plugins/web-ui/src/contexts.ts
+++ b/plugins/web-ui/src/contexts.ts
@@ -797,6 +797,11 @@ function memberPicker(context: CoreContext): TemplateResult {
           .value=${contextsState.memberQuery}
           ?disabled=${contextsState.memberBusy}
           @input=${(event: InputEvent) => {
+            if (event.isComposing) return;
+            contextsState.memberQuery = (event.currentTarget as HTMLInputElement).value;
+            scheduleMemberSearch(context);
+          }}
+          @compositionend=${(event: CompositionEvent) => {
             contextsState.memberQuery = (event.currentTarget as HTMLInputElement).value;
             scheduleMemberSearch(context);
           }}
diff --git a/src/directory/directory-store.ts b/src/directory/directory-store.ts
index 8fe4b9bf2..f232e8f2e 100644
--- a/src/directory/directory-store.ts
+++ b/src/directory/directory-store.ts
@@ -84,6 +84,7 @@ function pickMatch<T>(
   query: string,
   id: (t: T) => string,
   label: (t: T) => string,
+  matchIds: boolean,
 ): { kind: "one"; item: T } | { kind: "ambiguous"; items: T[] } | { kind: "none" } {
   const q = normDirectoryQuery(query);
   if (!q) return { kind: "none" };
@@ -92,8 +93,15 @@ function pickMatch<T>(
   const exact = items.filter((t) => normDirectoryQuery(label(t)) === q);
   if (exact.length === 1) return { kind: "one", item: exact[0]! };
   if (exact.length > 1) return { kind: "ambiguous", items: exact.slice(0, MAX_CANDIDATES) };
-  const prefix = items.filter((t) => normDirectoryQuery(label(t)).startsWith(q));
-  const pool = prefix.length ? prefix : items.filter((t) => normDirectoryQuery(label(t)).includes(q));
+  const labelLc = (t: T) => normDirectoryQuery(label(t));
+  const labelTiers = [
+    items.filter((t) => labelLc(t).startsWith(q)),
+    items.filter((t) => labelLc(t).includes(q)),
+  ];
+  const idTiers = matchIds
+    ? [items.filter((t) => id(t).toLowerCase().startsWith(q)), items.filter((t) => id(t).toLowerCase().includes(q))]
+    : [];
+  const pool = [...labelTiers, ...idTiers].find((tier) => tier.length > 0) ?? [];
   if (pool.length === 0) return { kind: "none" };
   if (pool.length === 1) return { kind: "one", item: pool[0]! };
   return { kind: "ambiguous", items: pool.slice(0, MAX_CANDIDATES) };
@@ -280,6 +288,7 @@ export function createDirectoryStore(): DirectoryStore {
         query,
         (x) => x.principalId,
         (x) => x.displayName,
+        true,
       );
       if (m.kind === "one") return { kind: "one", member: m.item };
       if (m.kind === "ambiguous") return { kind: "ambiguous", candidates: m.items };
@@ -291,6 +300,7 @@ export function createDirectoryStore(): DirectoryStore {
         query,
         (x) => x.channelId,
         (x) => x.name,
+        false,
       );
       if (m.kind === "one") return { kind: "one", channel: m.item };
       if (m.kind === "ambiguous") return { kind: "ambiguous", candidates: m.items };
diff --git a/src/directory/postgres-directory-store.ts b/src/directory/postgres-directory-store.ts
index 563ef59e0..e0bbca6cf 100644
--- a/src/directory/postgres-directory-store.ts
+++ b/src/directory/postgres-directory-store.ts
@@ -179,6 +179,7 @@ export function createPostgresDirectoryStore(connectionString: string): Director
     labelLcCol: string,
     cols: string,
     map: (r: Record<string, unknown>) => T,
+    matchIds: boolean,
   ): Promise<{ kind: "one"; item: T } | { kind: "ambiguous"; items: T[] } | { kind: "none" }> {
     const qn = normDirectoryQuery(query);
     if (!qn) return { kind: "none" };
@@ -195,15 +196,23 @@ export function createPostgresDirectoryStore(connectionString: string): Director
     if (exact.length > 1) return { kind: "ambiguous", items: exact.slice(0, MAX_CANDIDATES).map(map) };
 
     const esc = likeEscape(qn);
-    let pool2 = await q(
-      `SELECT ${cols} ${from} AND ${labelLcCol} LIKE $2 ESCAPE '\\' ORDER BY ${labelLcCol}, ${idCol} LIMIT ${MAX_CANDIDATES + 1}`,
-      [orgId, `${esc}%`],
-    );
-    if (!pool2.length) {
+    const tiers: Array<readonly [string, string]> = [
+      [labelLcCol, `${esc}%`],
+      [labelLcCol, `%${esc}%`],
+      ...(matchIds
+        ? [
+            [`lower(${idCol})`, `${esc}%`] as const,
+            [`lower(${idCol})`, `%${esc}%`] as const,
+          ]
+        : []),
+    ];
+    let pool2: Record<string, unknown>[] = [];
+    for (const [match, pattern] of tiers) {
       pool2 = await q(
-        `SELECT ${cols} ${from} AND ${labelLcCol} LIKE $2 ESCAPE '\\' ORDER BY ${labelLcCol}, ${idCol} LIMIT ${MAX_CANDIDATES + 1}`,
-        [orgId, `%${esc}%`],
+        `SELECT ${cols} ${from} AND ${match} LIKE $2 ESCAPE '\\' ORDER BY ${labelLcCol}, ${idCol} LIMIT ${MAX_CANDIDATES + 1}`,
+        [orgId, pattern],
       );
+      if (pool2.length) break;
     }
     if (!pool2.length) return { kind: "none" };
     if (pool2.length === 1) return { kind: "one", item: map(pool2[0]!) };
@@ -627,7 +636,7 @@ export function createPostgresDirectoryStore(connectionString: string): Director
         [orgId, query.trim()],
       );
       if (bySlackId.length) return { kind: "one", member: memberRow(bySlackId[0]!) };
-      const m = await pick(query, "directory_members", "principal_id", "display_name_lc", MEMBER_COLS, memberRow);
+      const m = await pick(query, "directory_members", "principal_id", "display_name_lc", MEMBER_COLS, memberRow, true);
       if (m.kind === "one") return { kind: "one", member: m.item };
       if (m.kind === "ambiguous") return { kind: "ambiguous", candidates: m.items };
       return { kind: "none" };
@@ -641,6 +650,7 @@ export function createPostgresDirectoryStore(connectionString: string): Director
         "name_lc",
         "channel_id, name, is_private, is_external",
         channelRow,
+        false,
       );
       if (m.kind === "one") return { kind: "one", channel: m.item };
       if (m.kind === "ambiguous") return { kind: "ambiguous", candidates: m.items };
diff --git a/test/directory-resolve.test.ts b/test/directory-resolve.test.ts
index 371d1683f..5d1bfdc76 100644
--- a/test/directory-resolve.test.ts
+++ b/test/directory-resolve.test.ts
@@ -88,6 +88,46 @@ describe("GET /v1/directory/resolve (agent looks up a teammate's mention id)", a
     assert.ok(matches.every((m) => m.principalId));
   });
 
+  it("resolves an id substring to every matching member", async () => {
+    const res = await get("/v1/directory/resolve?q=acme.com");
+    assert.equal(res.status, 200);
+    const { matches } = (await res.json()) as { matches: Array<{ principalId: string }> };
+    assert.equal(matches.length, 4, "an id substring matches all four fixture members");
+  });
+
+  it("resolves a unique email local-part prefix to a single match", async () => {
+    const res = await get("/v1/directory/resolve?q=carol@acm");
+    assert.equal(res.status, 200);
+    const { matches } = (await res.json()) as { matches: Array<{ principalId: string }> };
+    assert.equal(matches.length, 1);
+    assert.equal(matches[0]!.principalId, "carol@acme.com");
+  });
+
+  it("keeps label-contains matches ahead of a lone id-prefix hit", async () => {
+    await built.app.upsertDirectory([
+      { principalId: "carol@acme.com", displayName: "Carol Example", type: "internal", slackId: "U0CAROL" },
+      { principalId: "alice@acme.com", displayName: "Alice", type: "internal", slackId: "U0ALICE" },
+      { principalId: "jordan@acme.com", displayName: "Jordan", type: "internal", slackId: "U0JORDAN" },
+      { principalId: "joan@acme.com", displayName: "Joan", type: "internal", slackId: "U0JOAN" },
+      { principalId: "asmith@acme.com", displayName: "Alice Smith", type: "internal" },
+      { principalId: "bsmith@acme.com", displayName: "Bob Smith", type: "internal" },
+      { principalId: "smith.dave@acme.com", displayName: "Dave Jones", type: "internal" },
+    ]);
+    const res = await get("/v1/directory/resolve?q=smith");
+    await built.app.upsertDirectory([
+      { principalId: "carol@acme.com", displayName: "Carol Example", type: "internal", slackId: "U0CAROL" },
+      { principalId: "alice@acme.com", displayName: "Alice", type: "internal", slackId: "U0ALICE" },
+      { principalId: "jordan@acme.com", displayName: "Jordan", type: "internal", slackId: "U0JORDAN" },
+      { principalId: "joan@acme.com", displayName: "Joan", type: "internal", slackId: "U0JOAN" },
+    ]);
+    assert.equal(res.status, 200);
+    const { matches } = (await res.json()) as { matches: Array<{ principalId: string }> };
+    assert.ok(matches.length >= 2, "surname query stays ambiguous across the label-contains Smiths");
+    const ids = matches.map((m) => m.principalId);
+    assert.ok(ids.includes("asmith@acme.com") && ids.includes("bsmith@acme.com"));
+    assert.ok(!ids.includes("smith.dave@acme.com"), "an id-prefix-only hit does not preempt label-contains matches");
+  });
+
   it("returns an empty match set for an unknown name (agent falls back to plain text)", async () => {
     const res = await get("/v1/directory/resolve?q=nobody-here");
     assert.equal(res.status, 200);
diff --git a/test/directory-store.test.ts b/test/directory-store.test.ts
index c2a2c39b5..7ab4dcd51 100644
--- a/test/directory-store.test.ts
+++ b/test/directory-store.test.ts
@@ -103,6 +103,10 @@ describe("channel resolution (agent → channel addressing, §10)", () => {
   it("returns none for an unknown channel", async () => {
     assert.equal((await (await dir()).resolveChannel("nonexistent")).kind, "none");
   });
+
+  it("does not fall back to channel-id prefixes when no name matches", async () => {
+    assert.equal((await (await dir()).resolveChannel("c-e")).kind, "none");
+  });
 });
 
 describe("member slackId (the real <@…> mention id for an email principal)", () => {