diff --git a/packages/protocol/src/types.ts b/packages/protocol/src/types.ts
index 3cbd6c1..eb3641c 100644
--- a/packages/protocol/src/types.ts
+++ b/packages/protocol/src/types.ts
@@ -178,6 +178,29 @@ export type SessionStatus =
   | "waiting_approval"
   | "error";
 
+/**
+ * Placeholder body for a `thinking` message the backend produced no readable
+ * reasoning for.
+ *
+ * A thinking message must be committed with NON-EMPTY content — the TUI's
+ * "same msgId + content ⇒ committed" rule is what retires the live spinner, so
+ * an empty commit leaves `Thinking…` stuck. Hence a sentinel rather than "".
+ *
+ * Shared (not duplicated) because both sides key off it: the daemon writes it,
+ * and clients use it to tell "reasoning exists, show an expander" apart from
+ * "there is nothing behind this" — an expander that opens onto a placeholder is
+ * worse than no expander at all.
+ *
+ * Whether reasoning arrives at all is a BACKEND property, not a codeoid one.
+ * Claude returns readable text only when `thinking.display` is `"summarized"`
+ * (the API default is `"omitted"`, which streams thinking blocks with empty
+ * text); the raw chain of thought is never exposed on any model. Other
+ * backends — qwen-code, and OSS models behind an OpenAI-compatible gateway —
+ * stream plaintext reasoning directly. So both branches are live at once, and
+ * neither is an error state.
+ */
+export const REASONING_UNAVAILABLE = "(no reasoning returned by this model)";
+
 /** True when the session is mid-turn (either reasoning or running a tool). */
 export function isActiveStatus(s: SessionStatus): boolean {
   return s === "thinking" || s === "tool_running";
diff --git a/src/daemon/providers/claude/index.ts b/src/daemon/providers/claude/index.ts
index 143205d..abcf254 100644
--- a/src/daemon/providers/claude/index.ts
+++ b/src/daemon/providers/claude/index.ts
@@ -543,7 +543,16 @@ export class ClaudeProvider implements SessionProvider {
         permissionMode: "default",
         includePartialMessages: true,
         persistSession: true,
-        thinking: { type: "adaptive" as const },
+        // `display` defaults to "omitted" on Opus 5 / 4.8 / 4.7, Sonnet 5, and
+        // Fable 5 — which streams thinking blocks whose text is EMPTY. Codeoid
+        // then committed them as a placeholder, so every reasoning block in the
+        // UI expanded onto nothing (measured: 3,445 of 3,450 on one session).
+        // "summarized" returns readable reasoning instead. It is free: display
+        // controls visibility only, and thinking is billed identically either
+        // way — the tokens were already spent, we just weren't being shown
+        // anything for them. (The raw chain of thought is never exposed on any
+        // model; this is a summary of it.)
+        thinking: { type: "adaptive" as const, display: "summarized" as const },
         ...(opts.model ? { model: opts.model } : {}),
         ...(opts.fallbackModel ? { fallbackModel: opts.fallbackModel } : {}),
         stderr: (data: string) => {
diff --git a/src/daemon/session.ts b/src/daemon/session.ts
index de65a6a..8415603 100644
--- a/src/daemon/session.ts
+++ b/src/daemon/session.ts
@@ -61,7 +61,13 @@ import { promisify } from "node:util";
 const execFileP = promisify(execFile);
 /** Max wall-clock for a fork.setup command (deps install can be slow). */
 const FORK_SETUP_TIMEOUT_MS = 600_000;
-import { authToIdentity, CAPABILITIES, isActiveStatus, SYSTEM_IDENTITY } from "../protocol/types.js";
+import {
+  authToIdentity,
+  CAPABILITIES,
+  isActiveStatus,
+  REASONING_UNAVAILABLE,
+  SYSTEM_IDENTITY,
+} from "../protocol/types.js";
 import type { Store } from "./store.js";
 import type { AgentIdentityManager } from "./agent-identity.js";
 import { ScrollbackBuffer } from "./scrollback.js";
@@ -4290,7 +4296,11 @@ export class Session {
     this.#activeThinkingMsg = null;
     this.#activeThinkingIndex = null;
     if (!m.content || m.content.length === 0) {
-      m.content = "(reasoning elided)";
+      // Not an elision by codeoid — the backend returned no readable reasoning.
+      // Claude does this whenever `thinking.display` is `"omitted"`; backends
+      // that stream plaintext reasoning (qwen-code, OSS models over an
+      // OpenAI-compatible gateway) land in the branch above with real content.
+      m.content = REASONING_UNAVAILABLE;
     }
     this.#commitStreamed(m);
     this.#broadcastRaw(m);
diff --git a/web/src/components/transcript/MessageRow.test.tsx b/web/src/components/transcript/MessageRow.test.tsx
index f30fe95..420b003 100644
--- a/web/src/components/transcript/MessageRow.test.tsx
+++ b/web/src/components/transcript/MessageRow.test.tsx
@@ -4,6 +4,7 @@ import { render, cleanup } from "@solidjs/testing-library";
 import { createSignal } from "solid-js";
 
 import MessageRow from "./MessageRow";
+import { REASONING_UNAVAILABLE } from "../../protocol/types";
 import type { SessionMessage } from "../../protocol/types";
 
 function thinkingMsg(content: string): SessionMessage {
@@ -29,7 +30,34 @@ describe("ThinkingBlock", () => {
     expect(three.container.textContent).toContain("reasoning (3 lines)");
     cleanup();
     const one = render(() => <MessageRow msg={thinkingMsg("no newline here")} />);
-    expect(one.container.textContent).toContain("reasoning (1 lines)");
+    expect(one.container.textContent).toContain("reasoning (1 line)");
+  });
+
+  it("renders a flat marker — not an expander — when no reasoning was returned", () => {
+    // Backends differ: qwen-code and OSS models stream plaintext reasoning,
+    // while Claude returns text only under thinking.display "summarized".
+    // With nothing behind it, an expander advertises content it can't show.
+    const { container } = render(() => <MessageRow msg={thinkingMsg(REASONING_UNAVAILABLE)} />);
+    expect(container.querySelector("details")).toBeNull();
+    expect(container.textContent).toContain(REASONING_UNAVAILABLE);
+    // No line count either — "(1 line)" over a placeholder is what made the
+    // original report look like a counting bug rather than absent data.
+    expect(container.textContent).not.toContain("line)");
+  });
+
+  it("renders an expander when the backend DID return reasoning", () => {
+    const { container } = render(() =>
+      <MessageRow msg={thinkingMsg("Considering the tradeoffs\nand the constraints")} />,
+    );
+    const details = container.querySelector("details");
+    expect(details).not.toBeNull();
+    expect(container.textContent).toContain("reasoning (2 lines)");
+    expect(container.textContent).toContain("Considering the tradeoffs");
+  });
+
+  it("treats whitespace-only reasoning as absent", () => {
+    const { container } = render(() => <MessageRow msg={thinkingMsg("   \n  ")} />);
+    expect(container.querySelector("details")).toBeNull();
   });
 
   it("coalesces streaming deltas to one recount per animation frame", () => {
@@ -62,7 +90,7 @@ describe("ThinkingBlock", () => {
   it("updates synchronously when not streaming (throttle passthrough)", () => {
     const [msg, setMsg] = createSignal(thinkingMsg("x"));
     const { container } = render(() => <MessageRow msg={msg()} />);
-    expect(container.textContent).toContain("reasoning (1 lines)");
+    expect(container.textContent).toContain("reasoning (1 line)");
     setMsg(thinkingMsg("x\ny\nz"));
     expect(container.textContent).toContain("reasoning (3 lines)");
     expect(container.textContent).toContain("x\ny\nz");
diff --git a/web/src/components/transcript/MessageRow.tsx b/web/src/components/transcript/MessageRow.tsx
index e531508..a96ce73 100644
--- a/web/src/components/transcript/MessageRow.tsx
+++ b/web/src/components/transcript/MessageRow.tsx
@@ -19,6 +19,7 @@ import {
   createFrameThrottled,
   splitStreamingBlocks,
 } from "../../lib/streaming-markdown";
+import { REASONING_UNAVAILABLE } from "../../protocol/types";
 import type {
   MessageRole,
   SessionMessage,
@@ -208,17 +209,41 @@ const ThinkingBlock: Component<{ text: string; streaming?: boolean }> = (props)
     () => props.text,
     () => props.streaming === true,
   );
+  /**
+   * Whether there is real reasoning behind this block.
+   *
+   * Backends differ and both branches are normal: qwen-code and OSS models over
+   * an OpenAI-compatible gateway stream plaintext reasoning, while Claude
+   * returns readable text only under `thinking.display: "summarized"`. When
+   * there is nothing, an expander is actively misleading — it advertises
+   * content, counts "1 lines", and opens onto a placeholder. Render a flat
+   * marker instead, so the thinking→answer rhythm still reads without
+   * promising something that can't be shown.
+   */
+  const hasReasoning = createMemo(() => {
+    const t = throttled().trim();
+    return t.length > 0 && t !== REASONING_UNAVAILABLE;
+  });
   const lineCount = createMemo(() => countLines(throttled()));
   return (
-    <details class="text-[12px] italic text-role-thinking" open={props.streaming}>
-      <summary class="cursor-pointer select-none text-fg-faint hover:text-fg-muted">
-        reasoning ({lineCount()} lines)
-        <Show when={props.streaming}>
-          <span class="md-streaming-caret ml-1" aria-label="streaming" />
-        </Show>
-      </summary>
-      <div class="mt-1 whitespace-pre-wrap pl-3">{throttled()}</div>
-    </details>
+    <Show
+      when={hasReasoning()}
+      fallback={
+        <div class="text-[12px] italic text-fg-faint" aria-label="reasoning unavailable">
+          {REASONING_UNAVAILABLE}
+        </div>
+      }
+    >
+      <details class="text-[12px] italic text-role-thinking" open={props.streaming}>
+        <summary class="cursor-pointer select-none text-fg-faint hover:text-fg-muted">
+          reasoning ({lineCount()} {lineCount() === 1 ? "line" : "lines"})
+          <Show when={props.streaming}>
+            <span class="md-streaming-caret ml-1" aria-label="streaming" />
+          </Show>
+        </summary>
+        <div class="mt-1 whitespace-pre-wrap pl-3">{throttled()}</div>
+      </details>
+    </Show>
   );
 };