diff --git a/src/cli.ts b/src/cli.ts
index ceb5298..b5f9ec5 100644
--- a/src/cli.ts
+++ b/src/cli.ts
@@ -125,9 +125,15 @@ program
 
 program
   .command("list")
-  .description("List results from the most recent ensemble run")
-  .action(async () => {
-    await list();
+  .description("List all past runs, or show details for a specific run")
+  .argument("[run-number]", "Run number to show details for")
+  .action(async (runNumberArg?: string) => {
+    const runNumber = runNumberArg ? parseInt(runNumberArg, 10) : undefined;
+    if (runNumberArg && (Number.isNaN(runNumber) || (runNumber as number) < 1)) {
+      console.error("Error: run number must be a positive integer");
+      process.exit(1);
+    }
+    await list(runNumber);
   });
 
 program
diff --git a/src/commands/list.test.ts b/src/commands/list.test.ts
new file mode 100644
index 0000000..f0b9dae
--- /dev/null
+++ b/src/commands/list.test.ts
@@ -0,0 +1,96 @@
+import assert from "node:assert/strict";
+import { describe, it } from "node:test";
+import type { EnsembleResult } from "../types.js";
+import { buildRunSummary, extractRunNumber } from "./list.js";
+
+describe("extractRunNumber", () => {
+  it("returns -1 (run numbers assigned by load order, not filename)", () => {
+    assert.equal(extractRunNumber("run-2026-03-28T05-58-48-564Z.json"), -1);
+    assert.equal(extractRunNumber("latest.json"), -1);
+  });
+});
+
+function makeResult(overrides: Partial<EnsembleResult> = {}): EnsembleResult {
+  return {
+    prompt: "test prompt",
+    model: "sonnet",
+    timestamp: "2026-03-28T10:00:00Z",
+    scoring: "copeland",
+    agents: [
+      {
+        id: 1,
+        worktree: "/tmp/w1",
+        status: "success",
+        exitCode: 0,
+        duration: 5000,
+        output: "",
+        diff: "diff",
+        filesChanged: ["a.ts"],
+        linesAdded: 10,
+        linesRemoved: 2,
+      },
+      {
+        id: 2,
+        worktree: "/tmp/w2",
+        status: "success",
+        exitCode: 0,
+        duration: 8000,
+        output: "",
+        diff: "diff",
+        filesChanged: ["a.ts", "b.ts"],
+        linesAdded: 20,
+        linesRemoved: 5,
+      },
+    ],
+    tests: [
+      { agentId: 1, passed: true, output: "", exitCode: 0 },
+      { agentId: 2, passed: false, output: "", exitCode: 1 },
+    ],
+    convergence: [
+      { agents: [1, 2], similarity: 0.8, filesChanged: ["a.ts"], description: "similar" },
+    ],
+    recommended: 1,
+    scores: [],
+    ...overrides,
+  };
+}
+
+describe("buildRunSummary", () => {
+  it("builds summary with test pass rate and convergence", () => {
+    const result = makeResult();
+    const summary = buildRunSummary(3, result);
+
+    assert.equal(summary.runNumber, 3);
+    assert.equal(summary.timestamp, "2026-03-28T10:00:00Z");
+    assert.equal(summary.agentCount, 2);
+    assert.equal(summary.recommended, 1);
+    assert.equal(summary.testPassRate, 0.5);
+    assert.equal(summary.avgConvergence, 0.8);
+  });
+
+  it("returns null test pass rate when no tests", () => {
+    const result = makeResult({ tests: [] });
+    const summary = buildRunSummary(1, result);
+
+    assert.equal(summary.testPassRate, null);
+  });
+
+  it("returns null convergence when no convergence groups", () => {
+    const result = makeResult({ convergence: [] });
+    const summary = buildRunSummary(1, result);
+
+    assert.equal(summary.avgConvergence, null);
+  });
+
+  it("averages multiple convergence groups", () => {
+    const result = makeResult({
+      convergence: [
+        { agents: [1, 2], similarity: 0.6, filesChanged: ["a.ts"], description: "a" },
+        { agents: [1, 2], similarity: 1.0, filesChanged: ["b.ts"], description: "b" },
+      ],
+    });
+    const summary = buildRunSummary(5, result);
+
+    assert.equal(summary.avgConvergence, 0.8);
+  });
+});
diff --git a/src/commands/list.ts b/src/commands/list.ts
index ee6ef6e..eb31dc8 100644
--- a/src/commands/list.ts
+++ b/src/commands/list.ts
@@ -1,13 +1,119 @@
-import { readFile } from "node:fs/promises";
+import { readdir, readFile } from "node:fs/promises";
 import { join } from "node:path";
+import pc from "picocolors";
 import type { EnsembleResult } from "../types.js";
-import { displayResults } from "../utils/display.js";
+import { displayResults, padRight } from "../utils/display.js";
 
-export async function list(): Promise<void> {
+export interface RunSummary {
+  runNumber: number;
+  timestamp: string;
+  agentCount: number;
+  recommended: number | null;
+  testPassRate: number | null;
+  avgConvergence: number | null;
+}
+
+/** Run numbers are assigned by sort order (chronological), not embedded in filename */
+export function extractRunNumber(_filename: string): number {
+  return -1; // Assigned by loadAllRuns based on sort position
+}
+
+export function buildRunSummary(runNumber: number, result: EnsembleResult): RunSummary {
+  const testPassRate =
+    result.tests.length > 0
+      ? result.tests.filter((t) => t.passed).length / result.tests.length
+      : null;
+
+  const similarities = result.convergence.map((g) => g.similarity);
+  const avgConvergence =
+    similarities.length > 0
+      ? similarities.reduce((sum, s) => sum + s, 0) / similarities.length
+      : null;
+
+  return {
+    runNumber,
+    timestamp: result.timestamp,
+    agentCount: result.agents.length,
+    recommended: result.recommended,
+    testPassRate,
+    avgConvergence,
+  };
+}
+
+export async function loadAllRuns(): Promise<{ filename: string; result: EnsembleResult }[]> {
+  const entries = await readdir(".thinktank");
+  const files = entries.filter((f) => f.startsWith("run-") && f.endsWith(".json")).sort(); // Lexicographic sort = chronological for ISO timestamps
+
+  const runs: { filename: string; result: EnsembleResult }[] = [];
+  for (const file of files) {
+    try {
+      const raw = await readFile(join(".thinktank", file), "utf-8");
+      runs.push({ filename: file, result: JSON.parse(raw) as EnsembleResult });
+    } catch {
+      // skip malformed files
+    }
+  }
+  return runs;
+}
+
+function displayRunTable(summaries: RunSummary[]): void {
+  console.log();
+  console.log(pc.bold("Run History"));
+  console.log(pc.dim("─".repeat(72)));
+  console.log(
+    "  " +
+      padRight("Run", 6) +
+      padRight("Timestamp", 22) +
+      padRight("Agents", 8) +
+      padRight("Best", 6) +
+      padRight("Tests", 10) +
+      padRight("Convergence", 12),
+  );
+  console.log(`  ${pc.dim("─".repeat(64))}`);
+
+  for (const s of summaries) {
+    const testStr =
+      s.testPassRate !== null ? `${Math.round(s.testPassRate * 100)}%` : pc.dim("n/a");
+    const convStr =
+      s.avgConvergence !== null ? `${Math.round(s.avgConvergence * 100)}%` : pc.dim("n/a");
+    const bestStr = s.recommended !== null ? `#${s.recommended}` : pc.dim("n/a");
+
+    console.log(
+      "  " +
+        padRight(`${s.runNumber}`, 6) +
+        padRight(s.timestamp, 22) +
+        padRight(String(s.agentCount), 8) +
+        padRight(bestStr, 6) +
+        padRight(testStr, 10) +
+        padRight(convStr, 12),
+    );
+  }
+
+  console.log();
+  console.log(pc.dim("  View details: thinktank list <run-number>"));
+  console.log();
+}
+
+export async function list(runNumber?: number): Promise<void> {
   try {
-    const raw = await readFile(join(".thinktank", "latest.json"), "utf-8");
-    const result: EnsembleResult = JSON.parse(raw);
-    displayResults(result);
+    const runs = await loadAllRuns();
+
+    if (runs.length === 0) {
+      console.log("  No results found. Run `thinktank run` first.");
+      return;
+    }
+
+    if (runNumber !== undefined) {
+      if (runNumber < 1 || runNumber > runs.length) {
+        console.log(`  Run #${runNumber} not found. Valid range: 1-${runs.length}`);
+        return;
+      }
+      displayResults(runs[runNumber - 1]!.result);
+      return;
+    }
+
+    const summaries = runs.map((r, i) => buildRunSummary(i + 1, r.result));
+    displayRunTable(summaries);
   } catch {
     console.log("  No results found. Run `thinktank run` first.");
   }