diff --git a/.changeset/harness-selector-support.md b/.changeset/harness-selector-support.md
new file mode 100644
index 0000000..8ceba61
--- /dev/null
+++ b/.changeset/harness-selector-support.md
@@ -0,0 +1,10 @@
+---
+"@tangle-network/agent-interface": minor
+---
+
+Add harness selector-support capability: `harnessHonorsModel`, `harnessHonorsEffort`, and
+`harnessHonorsSelectors`. These report whether a harness's runner actually honors the per-turn model
+and reasoning-effort pickers (grounded in the cli-bridge adapter audit: `amp` drops both;
+`openclaw`/`nanoclaw` drop the model; `factory-droids`/`hermes`/`nanoclaw` drop the effort). Chat
+pickers use these to trim or mark harnesses up front, so a user's model/effort choice is never
+silently ignored. Distinct from `reasoningEffortsFor` (which levels a harness can express).
diff --git a/packages/agent-interface/src/harness-capabilities.test.ts b/packages/agent-interface/src/harness-capabilities.test.ts
index d69f9e4..37d760a 100644
--- a/packages/agent-interface/src/harness-capabilities.test.ts
+++ b/packages/agent-interface/src/harness-capabilities.test.ts
@@ -1,5 +1,8 @@
 import { describe, expect, it } from "vitest";
 import {
+  harnessHonorsEffort,
+  harnessHonorsModel,
+  harnessHonorsSelectors,
   harnessProviders,
   harnessReasoningEfforts,
   harnessSupportsModel,
@@ -135,3 +138,38 @@ describe("reasoning effort support", () => {
     );
   });
 });
+
+describe("per-turn selector support", () => {
+  it("honors both selectors for the mainstream agent harnesses", () => {
+    for (const h of ["opencode", "claude-code", "codex", "kimi-code"] as const) {
+      expect(harnessHonorsModel(h)).toBe(true);
+      expect(harnessHonorsEffort(h)).toBe(true);
+      expect(harnessHonorsSelectors(h)).toBe(true);
+    }
+  });
+
+  it("flags harnesses that drop the per-turn model", () => {
+    for (const h of ["amp", "openclaw", "nanoclaw"] as const) {
+      expect(harnessHonorsModel(h)).toBe(false);
+    }
+    expect(harnessHonorsModel("factory-droids")).toBe(true); // honors model, not effort
+  });
+
+  it("flags harnesses that drop the reasoning effort", () => {
+    for (const h of ["amp", "factory-droids", "hermes", "nanoclaw"] as const) {
+      expect(harnessHonorsEffort(h)).toBe(false);
+    }
+    expect(harnessHonorsEffort("openclaw")).toBe(true); // honors effort, not model
+  });
+
+  it("harnessHonorsSelectors is the AND of both", () => {
+    expect(harnessHonorsSelectors("amp")).toBe(false);
+    expect(harnessHonorsSelectors("factory-droids")).toBe(false); // model yes, effort no
+    expect(harnessHonorsSelectors("openclaw")).toBe(false); // effort yes, model no
+  });
+
+  it("resolves aliases before keying", () => {
+    // `claude` canonicalizes to `claude-code`, which honors both.
+    expect(harnessHonorsSelectors("claude")).toBe(true);
+  });
+});
diff --git a/packages/agent-interface/src/harness-capabilities.ts b/packages/agent-interface/src/harness-capabilities.ts
index 75e6f8b..28dc746 100644
--- a/packages/agent-interface/src/harness-capabilities.ts
+++ b/packages/agent-interface/src/harness-capabilities.ts
@@ -196,3 +196,45 @@ export function reasoningEffortsFor(
   }
   return efforts;
 }
+
+// ── Per-turn selector support (does the harness honor the chat pickers?) ──────
+
+/**
+ * Harnesses whose runner DROPS a per-turn selector — grounded in the cli-bridge adapter audit, NOT a
+ * guess. Most harnesses honor both selectors, so only the exceptions are listed; a harness absent from
+ * a set honors that selector. Keyed by the BASE runner (aliases canonicalized).
+ *
+ *   - model dropped:  `amp` (own agent picks the model), `openclaw` (dispatcher routes by its own
+ *     config), `nanoclaw` (socket-bridge runner is config/env-driven).
+ *   - effort dropped: `amp` and `factory-droids`/`hermes`/`nanoclaw` (no thinking flag is plumbed to
+ *     the underlying CLI).
+ *
+ * This is distinct from {@link reasoningEffortsFor} (which levels a harness can EXPRESS): a picker uses
+ * these to trim or mark harnesses up front, so a user's model/effort choice is never silently ignored.
+ */
+const harnessIgnoresModel: ReadonlySet<HarnessType> = new Set([
+  "amp",
+  "openclaw",
+  "nanoclaw",
+]);
+const harnessIgnoresEffort: ReadonlySet<HarnessType> = new Set([
+  "amp",
+  "factory-droids",
+  "hermes",
+  "nanoclaw",
+]);
+
+/** Whether the harness's runner honors a per-turn MODEL override (vs. picking the model itself). */
+export function harnessHonorsModel(harness: HarnessType): boolean {
+  return !harnessIgnoresModel.has(canonicalizeHarness(harness));
+}
+
+/** Whether the harness's runner honors a reasoning-EFFORT override (vs. dropping it). */
+export function harnessHonorsEffort(harness: HarnessType): boolean {
+  return !harnessIgnoresEffort.has(canonicalizeHarness(harness));
+}
+
+/** Whether the harness honors BOTH chat selectors — i.e. the model and effort pickers are live. */
+export function harnessHonorsSelectors(harness: HarnessType): boolean {
+  return harnessHonorsModel(harness) && harnessHonorsEffort(harness);
+}