diff --git a/frontend/src/lib/api/types/core.ts b/frontend/src/lib/api/types/core.ts
index 98c41913..918baffd 100644
--- a/frontend/src/lib/api/types/core.ts
+++ b/frontend/src/lib/api/types/core.ts
@@ -25,6 +25,7 @@ export interface Session {
   file_mtime?: number;
   total_output_tokens: number;
   peak_context_tokens: number;
+  main_model?: string;
   created_at: string;
 }
 
diff --git a/frontend/src/lib/components/command-palette/CommandPalette.test.ts b/frontend/src/lib/components/command-palette/CommandPalette.test.ts
index 257643d4..df23de4c 100644
--- a/frontend/src/lib/components/command-palette/CommandPalette.test.ts
+++ b/frontend/src/lib/components/command-palette/CommandPalette.test.ts
@@ -73,6 +73,7 @@ function makeSession(id: string, agent: string) {
     user_message_count: 1,
     total_output_tokens: 0,
     peak_context_tokens: 0,
+    main_model: "",
     created_at: "2026-02-20T12:30:00Z",
   };
 }
diff --git a/frontend/src/lib/components/content/MessageContent.svelte b/frontend/src/lib/components/content/MessageContent.svelte
index 0ed3c80e..e57e0acd 100644
--- a/frontend/src/lib/components/content/MessageContent.svelte
+++ b/frontend/src/lib/components/content/MessageContent.svelte
@@ -4,7 +4,7 @@
     parseContent,
     enrichSegments,
   } from "../../utils/content-parser.js";
-  import { formatTimestamp } from "../../utils/format.js";
+  import { formatTimestamp, shortModelName } from "../../utils/format.js";
   import { copyToClipboard } from "../../utils/clipboard.js";
   import ThinkingBlock from "./ThinkingBlock.svelte";
   import ToolBlock from "./ToolBlock.svelte";
@@ -22,9 +22,10 @@
     isSubagentContext?: boolean;
     highlightQuery?: string;
     isCurrentHighlight?: boolean;
+    owningSession?: Session | null;
   }
 
-  let { message, isSubagentContext = false, highlightQuery = "", isCurrentHighlight = false }: Props = $props();
+  let { message, isSubagentContext = false, highlightQuery = "", isCurrentHighlight = false, owningSession: owningSessionProp = null }: Props = $props();
 
   let copied = $state(false);
 
@@ -37,12 +38,28 @@
 
   let isUser = $derived(message.role === "user");
 
-  /** Resolve the session that owns this message, falling back to activeSession. */
+  /**
+   * Resolve the session that owns this message. If an explicit owningSession
+   * prop is provided (e.g. from SubagentInline which already has the child
+   * session), use it. Otherwise look up by session_id in sessions.sessions,
+   * falling back to activeSession.
+   */
   let owningSession = $derived(
-    sessions.sessions.find((s) => s.id === message.session_id) ??
+    owningSessionProp ??
+      sessions.sessions.find((s) => s.id === message.session_id) ??
       sessions.activeSession,
   );
 
+  /**
+   * Show the message's model name when it differs from the session's main
+   * model. Only applies to assistant messages — user messages carry no model.
+   */
+  let offMainModel = $derived.by((): string => {
+    if (isUser || !message.model) return "";
+    const mainModel = owningSession?.main_model ?? "";
+    return message.model !== mainModel ? message.model : "";
+  });
+
   /** Walk the parent chain to check if any ancestor has the teammate tag. */
   function isTeammateAncestry(s: Session, all: Session[]): boolean {
     if ((s.first_message ?? "").includes("<teammate-message")) return true;
@@ -202,6 +219,9 @@
     <span class="timestamp">
       {formatTimestamp(message.timestamp)}
     </span>
+    {#if offMainModel}
+      <span class="message-model" title={offMainModel}>{shortModelName(offMainModel)}</span>
+    {/if}
   </div>
 
   <div class="message-body">
@@ -295,6 +315,17 @@
     margin-left: auto;
   }
 
+  .message-model {
+    font-size: 10px;
+    color: var(--text-muted);
+    padding: 1px 4px;
+    border-radius: 3px;
+    background: var(--bg-tertiary);
+    white-space: nowrap;
+    flex-shrink: 0;
+    opacity: 0.8;
+  }
+
   .copy-btn {
     display: flex;
     align-items: center;
diff --git a/frontend/src/lib/components/content/MessageContent.test.ts b/frontend/src/lib/components/content/MessageContent.test.ts
new file mode 100644
index 00000000..879f8a5a
--- /dev/null
+++ b/frontend/src/lib/components/content/MessageContent.test.ts
@@ -0,0 +1,194 @@
+// @vitest-environment jsdom
+// ABOUTME: Unit tests for MessageContent's off-main-model badge behavior.
+// ABOUTME: Covers correct session resolution for top-level and subagent messages.
+import { describe, it, expect, vi } from "vitest";
+import { mount, unmount, tick } from "svelte";
+import type { Message, Session } from "../../api/types.js";
+
+// Mock all stores and child components that MessageContent depends on.
+vi.mock("../../stores/sessions.svelte.js", () => ({
+  sessions: {
+    sessions: [
+      {
+        id: "parent-session",
+        project: "proj",
+        machine: "mac",
+        agent: "copilot",
+        first_message: "hello",
+        started_at: "2026-01-01T00:00:00Z",
+        ended_at: "2026-01-01T00:01:00Z",
+        message_count: 2,
+        user_message_count: 1,
+        total_output_tokens: 0,
+        peak_context_tokens: 0,
+        main_model: "claude-sonnet-4.6",
+        created_at: "2026-01-01T00:00:00Z",
+      },
+    ],
+    activeSession: null,
+    childSessions: new Map(),
+  },
+}));
+
+vi.mock("../../stores/ui.svelte.js", () => ({
+  ui: {
+    isBlockVisible: () => true,
+    findInSession: { query: "" },
+  },
+}));
+
+vi.mock("../../stores/pins.svelte.js", () => ({
+  pins: { isPinned: () => false, togglePin: async () => {} },
+}));
+
+vi.mock("./ThinkingBlock.svelte", () => ({ default: {} }));
+vi.mock("./ToolBlock.svelte", () => ({ default: {} }));
+vi.mock("./CodeBlock.svelte", () => ({ default: {} }));
+vi.mock("./SkillBlock.svelte", () => ({ default: {} }));
+
+// @ts-ignore
+import MessageContent from "./MessageContent.svelte";
+
+function makeMessage(overrides: Partial<Message> = {}): Message {
+  return {
+    id: 1,
+    session_id: "parent-session",
+    ordinal: 0,
+    role: "assistant",
+    content: "Hello from assistant",
+    has_thinking: false,
+    has_tool_use: false,
+    content_length: 20,
+    timestamp: "2026-01-01T00:00:30Z",
+    model: "",
+    ...overrides,
+  };
+}
+
+function makeSession(id: string, mainModel: string): Session {
+  return {
+    id,
+    project: "proj",
+    machine: "mac",
+    agent: "copilot",
+    first_message: "hello",
+    started_at: "2026-01-01T00:00:00Z",
+    ended_at: "2026-01-01T00:01:00Z",
+    message_count: 2,
+    user_message_count: 1,
+    total_output_tokens: 0,
+    peak_context_tokens: 0,
+    main_model: mainModel,
+    created_at: "2026-01-01T00:00:00Z",
+  };
+}
+
+describe("MessageContent off-main-model badge", () => {
+  it("shows no model badge when message.model matches the session main_model", async () => {
+    const message = makeMessage({ model: "claude-sonnet-4.6" });
+    const component = mount(MessageContent, {
+      target: document.body,
+      props: { message },
+    });
+    await tick();
+
+    expect(document.querySelector(".message-model")).toBeNull();
+    unmount(component);
+  });
+
+  it("shows model badge when message.model differs from session main_model", async () => {
+    const message = makeMessage({ model: "claude-haiku-4.5" });
+    const component = mount(MessageContent, {
+      target: document.body,
+      props: { message },
+    });
+    await tick();
+
+    const badge = document.querySelector(".message-model");
+    expect(badge).toBeTruthy();
+    expect(badge?.textContent).toContain("haiku-4.5");
+    unmount(component);
+  });
+
+  it("shows no model badge when message has no model set", async () => {
+    const message = makeMessage({ model: "" });
+    const component = mount(MessageContent, {
+      target: document.body,
+      props: { message },
+    });
+    await tick();
+
+    expect(document.querySelector(".message-model")).toBeNull();
+    unmount(component);
+  });
+
+  it("shows no model badge for user messages even when model is set", async () => {
+    const message = makeMessage({ role: "user", model: "claude-haiku-4.5" });
+    const component = mount(MessageContent, {
+      target: document.body,
+      props: { message },
+    });
+    await tick();
+
+    expect(document.querySelector(".message-model")).toBeNull();
+    unmount(component);
+  });
+
+  it("uses explicit owningSession prop over sessions.sessions lookup", async () => {
+    // The message belongs to a child session (haiku as main model) but its
+    // session_id is "parent-session" in the store (sonnet as main model).
+    // Passing the child session explicitly should compare against haiku.
+    const childSession = makeSession("child-session", "claude-haiku-4.5");
+    const message = makeMessage({
+      session_id: "child-session",
+      model: "claude-haiku-4.5", // same as child main_model → no badge
+    });
+    const component = mount(MessageContent, {
+      target: document.body,
+      props: { message, owningSession: childSession },
+    });
+    await tick();
+
+    // model matches child session's main_model → no badge
+    expect(document.querySelector(".message-model")).toBeNull();
+    unmount(component);
+  });
+
+  it("shows badge for subagent message using a different model than its child session", async () => {
+    // Child session's main model is haiku, but this message used sonnet.
+    const childSession = makeSession("child-session", "claude-haiku-4.5");
+    const message = makeMessage({
+      session_id: "child-session",
+      model: "claude-sonnet-4.6",
+    });
+    const component = mount(MessageContent, {
+      target: document.body,
+      props: { message, owningSession: childSession },
+    });
+    await tick();
+
+    const badge = document.querySelector(".message-model");
+    expect(badge).toBeTruthy();
+    expect(badge?.textContent).toContain("sonnet-4.6");
+    unmount(component);
+  });
+
+  it("without owningSession prop, falls back to sessions.sessions lookup by session_id", async () => {
+    // parent-session has main_model=claude-sonnet-4.6 in the mock store.
+    // Message uses haiku → badge should appear.
+    const message = makeMessage({
+      session_id: "parent-session",
+      model: "claude-haiku-4.5",
+    });
+    const component = mount(MessageContent, {
+      target: document.body,
+      props: { message },
+    });
+    await tick();
+
+    const badge = document.querySelector(".message-model");
+    expect(badge).toBeTruthy();
+    expect(badge?.textContent).toContain("haiku-4.5");
+    unmount(component);
+  });
+});
diff --git a/frontend/src/lib/components/content/SubagentInline.svelte b/frontend/src/lib/components/content/SubagentInline.svelte
index 7d3e14e2..bd9e8541 100644
--- a/frontend/src/lib/components/content/SubagentInline.svelte
+++ b/frontend/src/lib/components/content/SubagentInline.svelte
@@ -3,7 +3,7 @@
 <script lang="ts">
   import type { Message, Session } from "../../api/types.js";
   import { getMessages, getSession } from "../../api/client.js";
-  import { formatTokenCount } from "../../utils/format.js";
+  import { formatTokenCount, shortModelName } from "../../utils/format.js";
   import { sessions } from "../../stores/sessions.svelte.js";
   import { router } from "../../stores/router.svelte.js";
   import MessageContent from "./MessageContent.svelte";
@@ -75,6 +75,9 @@
         {#if ctxTokens + subagentSession.total_output_tokens > 0}
           <span class="toggle-tokens">({formatTokenCount(ctxTokens)} ctx / {formatTokenCount(subagentSession.total_output_tokens)} out)</span>
         {/if}
+        {#if subagentSession.main_model}
+          <span class="toggle-model" title={subagentSession.main_model}>{shortModelName(subagentSession.main_model)}</span>
+        {/if}
       {/if}
     </button>
     <a
@@ -95,7 +98,7 @@
         <div class="subagent-status subagent-error">{error}</div>
       {:else if messages && messages.length > 0}
         {#each messages as message}
-          <MessageContent {message} isSubagentContext={true} />
+          <MessageContent {message} isSubagentContext={true} owningSession={subagentSession} />
         {/each}
       {:else if messages}
         <div class="subagent-status">No messages</div>
@@ -192,6 +195,13 @@
     flex-shrink: 0;
   }
 
+  .toggle-model {
+    font-size: 10px;
+    color: var(--text-muted);
+    white-space: nowrap;
+    flex-shrink: 0;
+  }
+
 
   .subagent-messages {
     border-left: 3px solid var(--accent-green);
diff --git a/frontend/src/lib/components/layout/SessionBreadcrumb.svelte b/frontend/src/lib/components/layout/SessionBreadcrumb.svelte
index 5447d3b3..99279315 100644
--- a/frontend/src/lib/components/layout/SessionBreadcrumb.svelte
+++ b/frontend/src/lib/components/layout/SessionBreadcrumb.svelte
@@ -10,7 +10,7 @@
   } from "../../api/client.js";
   import { copyToClipboard } from "../../utils/clipboard.js";
   import { agentColor } from "../../utils/agents.js";
-  import { formatTokenCount } from "../../utils/format.js";
+  import { formatTokenCount, shortModelName } from "../../utils/format.js";
   import { sessions } from "../../stores/sessions.svelte.js";
   import {
     supportsResume,
@@ -447,6 +447,9 @@
           {formatTokenCount(sessionContextTokens)} ctx / {formatTokenCount(session?.total_output_tokens ?? 0)} out
         </span>
       {/if}
+      {#if session?.main_model}
+        <span class="model-badge" title={session.main_model}>{shortModelName(session.main_model)}</span>
+      {/if}
       <div class="actions-wrapper">
         <button
           class="find-btn"
@@ -703,6 +706,16 @@
     flex-shrink: 0;
   }
 
+  .model-badge {
+    font-size: 10px;
+    color: var(--text-muted);
+    padding: 1px 5px;
+    border-radius: 4px;
+    background: var(--bg-tertiary);
+    white-space: nowrap;
+    flex-shrink: 0;
+  }
+
 
   .actions-wrapper {
     position: relative;
diff --git a/frontend/src/lib/components/layout/SessionBreadcrumb.test.ts b/frontend/src/lib/components/layout/SessionBreadcrumb.test.ts
index c233dd73..7bb53e63 100644
--- a/frontend/src/lib/components/layout/SessionBreadcrumb.test.ts
+++ b/frontend/src/lib/components/layout/SessionBreadcrumb.test.ts
@@ -18,6 +18,7 @@ function makeSession(agent: string): Session {
     user_message_count: 1,
     total_output_tokens: 0,
     peak_context_tokens: 0,
+    main_model: "",
     created_at: "2026-02-20T12:30:00Z",
   };
 }
@@ -59,4 +60,35 @@ describe("SessionBreadcrumb", () => {
 
     unmount(component);
   });
+
+  it("shows shortened model badge when main_model is set", async () => {
+    const session: Session = {
+      ...makeSession("copilot"),
+      main_model: "claude-sonnet-4.6",
+    };
+    const component = mount(SessionBreadcrumb, {
+      target: document.body,
+      props: { session, onBack: () => {} },
+    });
+
+    await tick();
+    const badge = document.querySelector(".model-badge");
+    expect(badge).toBeTruthy();
+    expect(badge?.textContent).toBe("sonnet-4.6");
+    expect(badge?.getAttribute("title")).toBe("claude-sonnet-4.6");
+
+    unmount(component);
+  });
+
+  it("hides model badge when main_model is empty", async () => {
+    const component = mount(SessionBreadcrumb, {
+      target: document.body,
+      props: { session: makeSession("copilot"), onBack: () => {} },
+    });
+
+    await tick();
+    expect(document.querySelector(".model-badge")).toBeNull();
+
+    unmount(component);
+  });
 });
diff --git a/frontend/src/lib/components/sidebar/session-list-utils.test.ts b/frontend/src/lib/components/sidebar/session-list-utils.test.ts
index e777f495..215d9149 100644
--- a/frontend/src/lib/components/sidebar/session-list-utils.test.ts
+++ b/frontend/src/lib/components/sidebar/session-list-utils.test.ts
@@ -32,6 +32,7 @@ function makeSession(overrides: Partial<Session> = {}): Session {
     user_message_count: 5,
     total_output_tokens: 0,
     peak_context_tokens: 0,
+    main_model: "",
     created_at: "2025-01-01T00:00:00Z",
     ...overrides,
   };
diff --git a/frontend/src/lib/stores/messages.test.ts b/frontend/src/lib/stores/messages.test.ts
index e670dabf..3fc3c3cf 100644
--- a/frontend/src/lib/stores/messages.test.ts
+++ b/frontend/src/lib/stores/messages.test.ts
@@ -41,6 +41,7 @@ function makeSession(
     user_message_count: messageCount,
     total_output_tokens: 0,
     peak_context_tokens: 0,
+    main_model: "",
     created_at: new Date(0).toISOString(),
   };
 }
diff --git a/frontend/src/lib/stores/sessions.test.ts b/frontend/src/lib/stores/sessions.test.ts
index 346658ef..241acf5b 100644
--- a/frontend/src/lib/stores/sessions.test.ts
+++ b/frontend/src/lib/stores/sessions.test.ts
@@ -225,6 +225,7 @@ describe("SessionsStore", () => {
               user_message_count: 1,
               total_output_tokens: 0,
               peak_context_tokens: 0,
+    main_model: "",
               created_at: "2024-01-01T00:00:00Z",
             },
           ],
@@ -245,6 +246,7 @@ describe("SessionsStore", () => {
               user_message_count: 1,
               total_output_tokens: 0,
               peak_context_tokens: 0,
+    main_model: "",
               created_at: "2024-01-01T00:00:01Z",
             },
           ],
@@ -840,6 +842,7 @@ function makeSession(
     user_message_count: 1,
     total_output_tokens: 0,
     peak_context_tokens: 0,
+    main_model: "",
     created_at: "2024-01-01T00:00:00Z",
     ...overrides,
   };
diff --git a/frontend/src/lib/utils/format.test.ts b/frontend/src/lib/utils/format.test.ts
index bec88840..728fdbbc 100644
--- a/frontend/src/lib/utils/format.test.ts
+++ b/frontend/src/lib/utils/format.test.ts
@@ -121,3 +121,32 @@ describe("formatTokenCount", () => {
     expect(formatTokenCount(3000000)).toBe("3M");
   });
 });
+
+import { shortModelName } from "./format.js";
+
+describe("shortModelName", () => {
+  it("strips claude- prefix", () => {
+    expect(shortModelName("claude-sonnet-4.6")).toBe("sonnet-4.6");
+    expect(shortModelName("claude-haiku-4.5")).toBe("haiku-4.5");
+    expect(shortModelName("claude-opus-4.6")).toBe("opus-4.6");
+  });
+
+  it("strips gpt- prefix", () => {
+    expect(shortModelName("gpt-4.1")).toBe("4.1");
+    expect(shortModelName("gpt-5-mini")).toBe("5-mini");
+  });
+
+  it("strips gemini- prefix", () => {
+    expect(shortModelName("gemini-3-pro-preview")).toBe("3-pro-preview");
+  });
+
+  it("returns unknown models unchanged", () => {
+    expect(shortModelName("llama-3.3-70b")).toBe("llama-3.3-70b");
+  });
+
+  it("returns empty string for null/undefined/empty", () => {
+    expect(shortModelName(null)).toBe("");
+    expect(shortModelName(undefined)).toBe("");
+    expect(shortModelName("")).toBe("");
+  });
+});
diff --git a/frontend/src/lib/utils/format.ts b/frontend/src/lib/utils/format.ts
index 2bd47541..846ff737 100644
--- a/frontend/src/lib/utils/format.ts
+++ b/frontend/src/lib/utils/format.ts
@@ -68,6 +68,22 @@ export function formatTokenCount(n: number): string {
   return m % 1 === 0 ? `${Math.floor(m)}M` : `${m}M`;
 }
 
+/**
+ * Strips well-known vendor prefixes from a model name for compact display.
+ * e.g. "claude-sonnet-4.6" → "sonnet-4.6", "gpt-4.1" → "4.1"
+ * Unknown models are returned as-is.
+ */
+export function shortModelName(model: string | null | undefined): string {
+  if (!model) return "";
+  // Strip leading "claude-" prefix
+  if (model.startsWith("claude-")) return model.slice("claude-".length);
+  // Strip leading "gpt-" prefix
+  if (model.startsWith("gpt-")) return model.slice("gpt-".length);
+  // Strip leading "gemini-" prefix
+  if (model.startsWith("gemini-")) return model.slice("gemini-".length);
+  return model;
+}
+
 let nonceCounter = 0;
 
 /** Reset the nonce counter. Exported for testing only. */
diff --git a/frontend/src/lib/utils/keyboard.test.ts b/frontend/src/lib/utils/keyboard.test.ts
index 4c28ae33..33358c4b 100644
--- a/frontend/src/lib/utils/keyboard.test.ts
+++ b/frontend/src/lib/utils/keyboard.test.ts
@@ -211,6 +211,7 @@ describe("registerShortcuts", () => {
         user_message_count: 1,
         total_output_tokens: 0,
         peak_context_tokens: 0,
+    main_model: "",
         created_at: "2024-01-01T00:00:00Z",
       };
     }
diff --git a/internal/db/db.go b/internal/db/db.go
index b37dec4b..6ddadaa1 100644
--- a/internal/db/db.go
+++ b/internal/db/db.go
@@ -23,7 +23,7 @@ import (
 // formatting changes). Old databases with a lower user_version
 // trigger a non-destructive re-sync (mtime reset + skip cache
 // clear) so existing session data is preserved.
-const dataVersion = 4
+const dataVersion = 5
 
 //go:embed schema.sql
 var schemaSQL string
@@ -307,6 +307,10 @@ func (db *DB) migrateColumns() error {
 			"sessions", "local_modified_at",
 			"ALTER TABLE sessions ADD COLUMN local_modified_at TEXT",
 		},
+		{
+			"sessions", "main_model",
+			"ALTER TABLE sessions ADD COLUMN main_model TEXT NOT NULL DEFAULT ''",
+		},
 	}
 
 	for _, m := range migrations {
diff --git a/internal/db/schema.sql b/internal/db/schema.sql
index 0b434593..b8ec8820 100644
--- a/internal/db/schema.sql
+++ b/internal/db/schema.sql
@@ -19,6 +19,7 @@ CREATE TABLE IF NOT EXISTS sessions (
     relationship_type TEXT NOT NULL DEFAULT '',
     total_output_tokens INTEGER NOT NULL DEFAULT 0,
     peak_context_tokens INTEGER NOT NULL DEFAULT 0,
+    main_model  TEXT NOT NULL DEFAULT '',
     deleted_at  TEXT,
     created_at  TEXT NOT NULL DEFAULT (strftime('%Y-%m-%dT%H:%M:%fZ','now'))
 );
diff --git a/internal/db/sessions.go b/internal/db/sessions.go
index d70b14be..10d3babb 100644
--- a/internal/db/sessions.go
+++ b/internal/db/sessions.go
@@ -27,7 +27,7 @@ const sessionBaseCols = `id, project, machine, agent,
 	first_message, display_name, started_at, ended_at,
 	message_count, user_message_count,
 	parent_session_id, relationship_type,
-	total_output_tokens, peak_context_tokens,
+	total_output_tokens, peak_context_tokens, main_model,
 	deleted_at, created_at`
 
 // sessionPruneCols extends sessionBaseCols with file metadata
@@ -36,7 +36,7 @@ const sessionPruneCols = `id, project, machine, agent,
 	first_message, display_name, started_at, ended_at,
 	message_count, user_message_count,
 	parent_session_id, relationship_type,
-	total_output_tokens, peak_context_tokens,
+	total_output_tokens, peak_context_tokens, main_model,
 	deleted_at, file_path, file_size, created_at`
 
 // sessionFullCols includes all columns for a complete session record.
@@ -44,7 +44,7 @@ const sessionFullCols = `id, project, machine, agent,
 	first_message, display_name, started_at, ended_at,
 	message_count, user_message_count,
 	parent_session_id, relationship_type,
-	total_output_tokens, peak_context_tokens,
+	total_output_tokens, peak_context_tokens, main_model,
 	deleted_at, file_path, file_size, file_mtime,
 	file_hash, local_modified_at, created_at`
 
@@ -69,7 +69,7 @@ func scanSessionRow(rs rowScanner) (Session, error) {
 		&s.FirstMessage, &s.DisplayName, &s.StartedAt, &s.EndedAt,
 		&s.MessageCount, &s.UserMessageCount,
 		&s.ParentSessionID, &s.RelationshipType,
-		&s.TotalOutputTokens, &s.PeakContextTokens,
+		&s.TotalOutputTokens, &s.PeakContextTokens, &s.MainModel,
 		&s.DeletedAt, &s.CreatedAt,
 	)
 	return s, err
@@ -91,6 +91,7 @@ type Session struct {
 	RelationshipType  string  `json:"relationship_type,omitempty"`
 	TotalOutputTokens int     `json:"total_output_tokens"`
 	PeakContextTokens int     `json:"peak_context_tokens"`
+	MainModel         string  `json:"main_model,omitempty"`
 	DeletedAt         *string `json:"deleted_at,omitempty"`
 	FilePath          *string `json:"file_path,omitempty"`
 	FileSize          *int64  `json:"file_size,omitempty"`
@@ -459,7 +460,7 @@ func (db *DB) GetSessionFull(
 		&s.FirstMessage, &s.DisplayName, &s.StartedAt, &s.EndedAt,
 		&s.MessageCount, &s.UserMessageCount,
 		&s.ParentSessionID, &s.RelationshipType,
-		&s.TotalOutputTokens, &s.PeakContextTokens,
+		&s.TotalOutputTokens, &s.PeakContextTokens, &s.MainModel,
 		&s.DeletedAt, &s.FilePath, &s.FileSize,
 		&s.FileMtime, &s.FileHash, &s.LocalModifiedAt, &s.CreatedAt,
 	)
@@ -518,9 +519,9 @@ func (db *DB) UpsertSession(s Session) error {
 			started_at, ended_at, message_count,
 			user_message_count, parent_session_id,
 			relationship_type,
-			total_output_tokens, peak_context_tokens,
+			total_output_tokens, peak_context_tokens, main_model,
 			file_path, file_size, file_mtime, file_hash
-		) VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?)
+		) VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?)
 		ON CONFLICT(id) DO UPDATE SET
 			project = excluded.project,
 			machine = excluded.machine,
@@ -534,6 +535,7 @@ func (db *DB) UpsertSession(s Session) error {
 			relationship_type = excluded.relationship_type,
 			total_output_tokens = excluded.total_output_tokens,
 			peak_context_tokens = excluded.peak_context_tokens,
+			main_model = excluded.main_model,
 			file_path = excluded.file_path,
 			file_size = excluded.file_size,
 			file_mtime = excluded.file_mtime,
@@ -542,7 +544,7 @@ func (db *DB) UpsertSession(s Session) error {
 		s.StartedAt, s.EndedAt, s.MessageCount,
 		s.UserMessageCount, s.ParentSessionID,
 		s.RelationshipType,
-		s.TotalOutputTokens, s.PeakContextTokens,
+		s.TotalOutputTokens, s.PeakContextTokens, s.MainModel,
 		s.FilePath, s.FileSize, s.FileMtime, s.FileHash)
 	if err != nil {
 		return fmt.Errorf("upserting session %s: %w", s.ID, err)
@@ -1054,7 +1056,7 @@ func (db *DB) FindPruneCandidates(
 			&s.FirstMessage, &s.DisplayName, &s.StartedAt, &s.EndedAt,
 			&s.MessageCount, &s.UserMessageCount,
 			&s.ParentSessionID, &s.RelationshipType,
-			&s.TotalOutputTokens, &s.PeakContextTokens,
+			&s.TotalOutputTokens, &s.PeakContextTokens, &s.MainModel,
 			&s.DeletedAt, &s.FilePath, &s.FileSize, &s.CreatedAt,
 		)
 		if err != nil {
diff --git a/internal/parser/copilot.go b/internal/parser/copilot.go
index d7595370..07a9f614 100644
--- a/internal/parser/copilot.go
+++ b/internal/parser/copilot.go
@@ -13,6 +13,8 @@ import (
 // Copilot JSONL event types.
 const (
 	copilotEventSessionStart    = "session.start"
+	copilotEventModelChange     = "session.model_change"
+	copilotEventSessionShutdown = "session.shutdown"
 	copilotEventUserMessage     = "user.message"
 	copilotEventAssistantMsg    = "assistant.message"
 	copilotEventToolComplete    = "tool.execution_complete"
@@ -22,13 +24,15 @@ const (
 // copilotSessionBuilder accumulates state while scanning a
 // Copilot JSONL session file line by line.
 type copilotSessionBuilder struct {
-	messages     []ParsedMessage
-	firstMessage string
-	startedAt    time.Time
-	endedAt      time.Time
-	sessionID    string
-	project      string
-	ordinal      int
+	messages            []ParsedMessage
+	firstMessage        string
+	startedAt           time.Time
+	endedAt             time.Time
+	sessionID           string
+	project             string
+	currentModel        string
+	shutdownModelCounts map[string]int64 // accumulated across all session.shutdown events
+	ordinal             int
 }
 
 func newCopilotSessionBuilder() *copilotSessionBuilder {
@@ -52,6 +56,10 @@ func (b *copilotSessionBuilder) processLine(line string) {
 	switch gjson.Get(line, "type").Str {
 	case copilotEventSessionStart:
 		b.handleSessionStart(data)
+	case copilotEventModelChange:
+		b.handleModelChange(data)
+	case copilotEventSessionShutdown:
+		b.handleSessionShutdown(data)
 	case copilotEventUserMessage:
 		b.handleUserMessage(data, ts)
 	case copilotEventAssistantMsg:
@@ -81,6 +89,39 @@ func (b *copilotSessionBuilder) handleSessionStart(
 	}
 }
 
+func (b *copilotSessionBuilder) handleModelChange(
+	data gjson.Result,
+) {
+	if m := data.Get("newModel").Str; m != "" {
+		b.currentModel = m
+	}
+}
+
+// handleSessionShutdown accumulates model request counts from
+// modelMetrics across all shutdown events in the file (Copilot
+// appends a new shutdown on each reconnect). The model with the
+// highest total requests across all shutdowns wins.
+func (b *copilotSessionBuilder) handleSessionShutdown(
+	data gjson.Result,
+) {
+	// currentModel in the shutdown payload is a secondary
+	// fallback: use it only if we haven't learned the model yet.
+	if m := data.Get("currentModel").Str; m != "" && b.currentModel == "" {
+		b.currentModel = m
+	}
+
+	// Accumulate per-model request counts across all shutdowns.
+	data.Get("modelMetrics").ForEach(func(key, val gjson.Result) bool {
+		if count := val.Get("requests.count").Int(); count > 0 {
+			if b.shutdownModelCounts == nil {
+				b.shutdownModelCounts = make(map[string]int64)
+			}
+			b.shutdownModelCounts[key.Str] += count
+		}
+		return true
+	})
+}
+
 func (b *copilotSessionBuilder) handleUserMessage(
 	data gjson.Result, ts time.Time,
 ) {
@@ -165,6 +206,7 @@ func (b *copilotSessionBuilder) handleAssistantMessage(
 		HasToolUse:    hasToolUse,
 		ContentLength: len(displayContent),
 		ToolCalls:     toolCalls,
+		Model:         b.currentModel,
 	})
 	b.ordinal++
 }
@@ -196,6 +238,21 @@ func (b *copilotSessionBuilder) handleToolComplete(
 		}},
 	})
 	b.ordinal++
+
+	// Use the model field to keep currentModel current and to
+	// backfill the model on the preceding assistant message
+	// (which was appended before the tool result arrived).
+	if m := data.Get("model").Str; m != "" {
+		b.currentModel = m
+		for i := len(b.messages) - 1; i >= 0; i-- {
+			if b.messages[i].Role == RoleAssistant {
+				if b.messages[i].Model == "" {
+					b.messages[i].Model = m
+				}
+				break
+			}
+		}
+	}
 }
 
 func (b *copilotSessionBuilder) handleAssistantReasoning() {
@@ -294,6 +351,23 @@ func ParseCopilotSession(
 		EndedAt:          b.endedAt,
 		MessageCount:     len(b.messages),
 		UserMessageCount: userCount,
+		MainModel: func() string {
+			if len(b.shutdownModelCounts) > 0 {
+				var best string
+				var bestCount int64
+				for model, count := range b.shutdownModelCounts {
+					if count > bestCount || (count == bestCount && model < best) {
+						best = model
+						bestCount = count
+					}
+				}
+				return best
+			}
+			if m := ComputeMainModel(b.messages); m != "" {
+				return m
+			}
+			return b.currentModel
+		}(),
 		File: FileInfo{
 			Path:  path,
 			Size:  info.Size(),
diff --git a/internal/parser/copilot_test.go b/internal/parser/copilot_test.go
index fe12073a..c8e88ab9 100644
--- a/internal/parser/copilot_test.go
+++ b/internal/parser/copilot_test.go
@@ -330,3 +330,188 @@ func TestSessionIDFromPath(t *testing.T) {
 		})
 	}
 }
+
+func TestParseCopilotSession_ModelChange(t *testing.T) {
+	path := writeCopilotJSONL(t,
+		`{"type":"session.start","data":{"sessionId":"model-test"},"timestamp":"2025-01-15T10:00:00Z"}`,
+		`{"type":"session.model_change","data":{"newModel":"claude-sonnet-4.6"},"timestamp":"2025-01-15T10:00:01Z"}`,
+		`{"type":"user.message","data":{"content":"Hello"},"timestamp":"2025-01-15T10:00:02Z"}`,
+		`{"type":"assistant.message","data":{"content":"Hi there"},"timestamp":"2025-01-15T10:00:03Z"}`,
+	)
+
+	sess, msgs := parseAndValidateHelper(t, path, "m", 2)
+
+	// Model should be tracked on assistant message.
+	assertEqual(t, "claude-sonnet-4.6", msgs[1].Model, "msgs[1].Model")
+	// User messages have no model.
+	assertEqual(t, "", msgs[0].Model, "msgs[0].Model")
+	// MainModel is the single model used.
+	assertEqual(t, "claude-sonnet-4.6", sess.MainModel, "sess.MainModel")
+}
+
+func TestParseCopilotSession_NoModel(t *testing.T) {
+	// Sessions without a session.model_change event should have
+	// empty model fields — model data is simply not available.
+	path := writeCopilotJSONL(t,
+		`{"type":"session.start","data":{"sessionId":"no-model"},"timestamp":"2025-01-15T10:00:00Z"}`,
+		`{"type":"user.message","data":{"content":"Hello"},"timestamp":"2025-01-15T10:00:01Z"}`,
+		`{"type":"assistant.message","data":{"content":"Hi"},"timestamp":"2025-01-15T10:00:02Z"}`,
+	)
+
+	sess, msgs := parseAndValidateHelper(t, path, "m", 2)
+
+	assertEqual(t, "", msgs[1].Model, "msgs[1].Model")
+	assertEqual(t, "", sess.MainModel, "sess.MainModel")
+}
+
+func TestParseCopilotSession_ModelMidSessionChange(t *testing.T) {
+	// Model switches mid-session: first two assistant messages use
+	// sonnet, then user switches to haiku for the last one.
+	// MainModel should be sonnet (majority).
+	path := writeCopilotJSONL(t,
+		`{"type":"session.start","data":{"sessionId":"switch-test"},"timestamp":"2025-01-15T10:00:00Z"}`,
+		`{"type":"session.model_change","data":{"newModel":"claude-sonnet-4.6"},"timestamp":"2025-01-15T10:00:01Z"}`,
+		`{"type":"user.message","data":{"content":"First"},"timestamp":"2025-01-15T10:00:02Z"}`,
+		`{"type":"assistant.message","data":{"content":"Reply one"},"timestamp":"2025-01-15T10:00:03Z"}`,
+		`{"type":"user.message","data":{"content":"Second"},"timestamp":"2025-01-15T10:00:04Z"}`,
+		`{"type":"assistant.message","data":{"content":"Reply two"},"timestamp":"2025-01-15T10:00:05Z"}`,
+		`{"type":"session.model_change","data":{"newModel":"claude-haiku-4.5"},"timestamp":"2025-01-15T10:00:06Z"}`,
+		`{"type":"user.message","data":{"content":"Third"},"timestamp":"2025-01-15T10:00:07Z"}`,
+		`{"type":"assistant.message","data":{"content":"Reply three"},"timestamp":"2025-01-15T10:00:08Z"}`,
+	)
+
+	sess, msgs := parseAndValidateHelper(t, path, "m", 6)
+
+	assertEqual(t, "claude-sonnet-4.6", msgs[1].Model, "msgs[1].Model")
+	assertEqual(t, "claude-sonnet-4.6", msgs[3].Model, "msgs[3].Model")
+	assertEqual(t, "claude-haiku-4.5", msgs[5].Model, "msgs[5].Model")
+	// Majority is sonnet (2 vs 1).
+	assertEqual(t, "claude-sonnet-4.6", sess.MainModel, "sess.MainModel")
+}
+
+func TestParseCopilotSession_ModelFromMultipleShutdowns(t *testing.T) {
+	// A long session with multiple session.shutdown events (Copilot
+	// appends one per reconnect). The last shutdown alone shows haiku
+	// winning, but accumulated counts show sonnet as dominant.
+	path := writeCopilotJSONL(t,
+		`{"type":"session.start","data":{"sessionId":"multi-shutdown"},"timestamp":"2025-01-15T10:00:00Z"}`,
+		`{"type":"user.message","data":{"content":"Hello"},"timestamp":"2025-01-15T10:00:01Z"}`,
+		`{"type":"assistant.message","data":{"content":"Hi"},"timestamp":"2025-01-15T10:00:02Z"}`,
+		// First shutdown: sonnet=29, haiku=9 → sonnet leads
+		`{"type":"session.shutdown","data":{"shutdownType":"routine","modelMetrics":{"claude-sonnet-4.6":{"requests":{"count":29}},"claude-haiku-4.5":{"requests":{"count":9}}}},"timestamp":"2025-01-15T10:01:00Z"}`,
+		// Second shutdown: sonnet=137 only
+		`{"type":"session.shutdown","data":{"shutdownType":"routine","modelMetrics":{"claude-sonnet-4.6":{"requests":{"count":137}}}},"timestamp":"2025-01-15T10:02:00Z"}`,
+		// Third shutdown: haiku=39, sonnet=20 → haiku wins in isolation
+		`{"type":"session.shutdown","data":{"shutdownType":"routine","modelMetrics":{"claude-haiku-4.5":{"requests":{"count":39}},"claude-sonnet-4.6":{"requests":{"count":20}}}},"timestamp":"2025-01-15T10:03:00Z"}`,
+	)
+
+	// Accumulated: sonnet=29+137+20=186, haiku=9+39=48 → sonnet wins
+	sess, _ := parseAndValidateHelper(t, path, "m", 2)
+	assertEqual(t, "claude-sonnet-4.6", sess.MainModel, "sess.MainModel")
+}
+
+func TestParseCopilotSession_ModelFromShutdown(t *testing.T) {
+	// No session.model_change — main model derived from modelMetrics
+	// in session.shutdown (sonnet has more requests than haiku).
+	path := writeCopilotJSONL(t,
+		`{"type":"session.start","data":{"sessionId":"shutdown-test"},"timestamp":"2025-01-15T10:00:00Z"}`,
+		`{"type":"user.message","data":{"content":"Hello"},"timestamp":"2025-01-15T10:00:01Z"}`,
+		`{"type":"assistant.message","data":{"content":"Hi"},"timestamp":"2025-01-15T10:00:02Z"}`,
+		`{"type":"session.shutdown","data":{"shutdownType":"routine","modelMetrics":{"claude-sonnet-4.6":{"requests":{"count":5,"cost":1},"usage":{"inputTokens":1000,"outputTokens":200}},"claude-haiku-4.5":{"requests":{"count":2,"cost":0},"usage":{"inputTokens":400,"outputTokens":80}}}},"timestamp":"2025-01-15T10:00:10Z"}`,
+	)
+
+	sess, _ := parseAndValidateHelper(t, path, "m", 2)
+	assertEqual(t, "claude-sonnet-4.6", sess.MainModel, "sess.MainModel")
+}
+
+func TestParseCopilotSession_ModelFromShutdownCurrentModel(t *testing.T) {
+	// session.shutdown has currentModel but empty modelMetrics.
+	// shutdownModelCounts is empty, ComputeMainModel returns ""
+	// (no message has model set), so b.currentModel is the final
+	// fallback and should be used as MainModel.
+	path := writeCopilotJSONL(t,
+		`{"type":"session.start","data":{"sessionId":"cur-model-test"},"timestamp":"2025-01-15T10:00:00Z"}`,
+		`{"type":"user.message","data":{"content":"Hello"},"timestamp":"2025-01-15T10:00:01Z"}`,
+		`{"type":"assistant.message","data":{"content":"Hi"},"timestamp":"2025-01-15T10:00:02Z"}`,
+		`{"type":"session.shutdown","data":{"shutdownType":"routine","currentModel":"claude-sonnet-4.6","modelMetrics":{}},"timestamp":"2025-01-15T10:00:10Z"}`,
+	)
+
+	sess, _ := parseAndValidateHelper(t, path, "m", 2)
+	assertEqual(t, "claude-sonnet-4.6", sess.MainModel, "sess.MainModel")
+}
+
+func TestParseCopilotSession_ModelFromToolComplete(t *testing.T) {
+	// tool.execution_complete carries a model field that should
+	// backfill the preceding assistant message and update currentModel.
+	path := writeCopilotJSONL(t,
+		`{"type":"session.start","data":{"sessionId":"tool-model"},"timestamp":"2025-01-15T10:00:00Z"}`,
+		`{"type":"user.message","data":{"content":"Do something"},"timestamp":"2025-01-15T10:00:01Z"}`,
+		`{"type":"assistant.message","data":{"content":"","toolRequests":[{"toolCallId":"tc1","name":"bash","arguments":{"command":"ls"}}]},"timestamp":"2025-01-15T10:00:02Z"}`,
+		`{"type":"tool.execution_complete","data":{"toolCallId":"tc1","result":"file.txt","model":"claude-sonnet-4.6"},"timestamp":"2025-01-15T10:00:03Z"}`,
+		`{"type":"assistant.message","data":{"content":"Done"},"timestamp":"2025-01-15T10:00:04Z"}`,
+	)
+
+	// 4 messages: user, assistant (tool-only), tool-result user, assistant (final)
+	sess, msgs := parseAndValidateHelper(t, path, "m", 4)
+
+	// The tool-only assistant message should be backfilled.
+	assertEqual(t, "claude-sonnet-4.6", msgs[1].Model, "msgs[1].Model (backfilled)")
+	// The final assistant message gets currentModel set from the tool complete.
+	assertEqual(t, "claude-sonnet-4.6", msgs[3].Model, "msgs[3].Model")
+	// ComputeMainModel over these 2 assistant messages → sonnet.
+	assertEqual(t, "claude-sonnet-4.6", sess.MainModel, "sess.MainModel")
+}
+
+func TestComputeMainModel(t *testing.T) {
+	tests := []struct {
+		name     string
+		messages []ParsedMessage
+		want     string
+	}{
+		{
+			name:     "empty",
+			messages: nil,
+			want:     "",
+		},
+		{
+			name: "no model data",
+			messages: []ParsedMessage{
+				{Role: RoleAssistant, Model: ""},
+				{Role: RoleUser, Model: ""},
+			},
+			want: "",
+		},
+		{
+			name: "single model",
+			messages: []ParsedMessage{
+				{Role: RoleAssistant, Model: "claude-sonnet-4.6"},
+				{Role: RoleUser, Model: ""},
+			},
+			want: "claude-sonnet-4.6",
+		},
+		{
+			name: "majority wins",
+			messages: []ParsedMessage{
+				{Role: RoleAssistant, Model: "claude-sonnet-4.6"},
+				{Role: RoleAssistant, Model: "claude-sonnet-4.6"},
+				{Role: RoleAssistant, Model: "claude-haiku-4.5"},
+			},
+			want: "claude-sonnet-4.6",
+		},
+		{
+			name: "user role model ignored",
+			messages: []ParsedMessage{
+				{Role: RoleUser, Model: "some-model"},
+				{Role: RoleAssistant, Model: "claude-sonnet-4.6"},
+			},
+			want: "claude-sonnet-4.6",
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			got := ComputeMainModel(tt.messages)
+			assertEqual(t, tt.want, got, "ComputeMainModel")
+		})
+	}
+}
diff --git a/internal/parser/types.go b/internal/parser/types.go
index dc8d6336..0596b8c4 100644
--- a/internal/parser/types.go
+++ b/internal/parser/types.go
@@ -272,6 +272,29 @@ type ParsedSession struct {
 
 	TotalOutputTokens int
 	PeakContextTokens int
+
+	// MainModel is the most frequently used model across assistant
+	// messages in this session, or empty if no model data is available.
+	MainModel string
+}
+
+// ComputeMainModel returns the most frequently occurring model
+// string across assistant messages. Empty-string models are
+// ignored. Returns "" when no model data is present.
+func ComputeMainModel(messages []ParsedMessage) string {
+	counts := make(map[string]int)
+	for _, m := range messages {
+		if m.Role == RoleAssistant && m.Model != "" {
+			counts[m.Model]++
+		}
+	}
+	best, bestN := "", 0
+	for model, n := range counts {
+		if n > bestN || (n == bestN && model < best) {
+			best, bestN = model, n
+		}
+	}
+	return best
 }
 
 // ParsedToolCall holds a single tool invocation extracted from
diff --git a/internal/sync/engine.go b/internal/sync/engine.go
index d09b1720..c81e6a78 100644
--- a/internal/sync/engine.go
+++ b/internal/sync/engine.go
@@ -2095,6 +2095,7 @@ func toDBSession(pw pendingWrite) db.Session {
 		RelationshipType:  string(pw.sess.RelationshipType),
 		TotalOutputTokens: pw.sess.TotalOutputTokens,
 		PeakContextTokens: pw.sess.PeakContextTokens,
+		MainModel:         pw.sess.MainModel,
 		FilePath:          strPtr(pw.sess.File.Path),
 		FileSize:          int64Ptr(pw.sess.File.Size),
 		FileMtime:         int64Ptr(pw.sess.File.Mtime),