diff --git a/src/agent/runner.ts b/src/agent/runner.ts
index 2b8fbce..25fd21c 100644
--- a/src/agent/runner.ts
+++ b/src/agent/runner.ts
@@ -490,6 +490,8 @@ export class AgentRunner {
     for await (const event of this.stream(messages, options)) {
       if (event.type === 'done') {
         Object.assign(accumulated, event.data)
+      } else if (event.type === 'error') {
+        throw event.data
       }
     }
 
diff --git a/tests/runner-error-propagation.test.ts b/tests/runner-error-propagation.test.ts
new file mode 100644
index 0000000..0613f9e
--- /dev/null
+++ b/tests/runner-error-propagation.test.ts
@@ -0,0 +1,85 @@
+import { describe, it, expect } from 'vitest'
+import { Agent } from '../src/agent/agent.js'
+import { AgentRunner } from '../src/agent/runner.js'
+import { ToolRegistry } from '../src/tool/framework.js'
+import { ToolExecutor } from '../src/tool/executor.js'
+import type { AgentConfig, LLMAdapter, LLMMessage } from '../src/types.js'
+
+// ---------------------------------------------------------------------------
+// Helpers
+// ---------------------------------------------------------------------------
+
+/** Adapter whose chat() always throws. */
+function errorAdapter(error: Error): LLMAdapter {
+  return {
+    name: 'error-mock',
+    async chat(_messages: LLMMessage[]) {
+      throw error
+    },
+    async *stream() {
+      /* unused */
+    },
+  }
+}
+
+function buildAgentWithAdapter(config: AgentConfig, adapter: LLMAdapter) {
+  const registry = new ToolRegistry()
+  const executor = new ToolExecutor(registry)
+  const agent = new Agent(config, registry, executor)
+
+  const runner = new AgentRunner(adapter, registry, executor, {
+    model: config.model,
+    systemPrompt: config.systemPrompt,
+    maxTurns: config.maxTurns,
+    agentName: config.name,
+  })
+  ;(agent as any).runner = runner
+
+  return agent
+}
+
+const baseConfig: AgentConfig = {
+  name: 'test-agent',
+  model: 'mock-model',
+  systemPrompt: 'You are a test agent.',
+}
+
+// ---------------------------------------------------------------------------
+// Tests — #98: AgentRunner.run() must propagate errors from stream()
+// ---------------------------------------------------------------------------
+
+describe('AgentRunner.run() error propagation (#98)', () => {
+  it('LLM adapter error surfaces as success:false in AgentRunResult', async () => {
+    const apiError = new Error('API 500: internal server error')
+    const agent = buildAgentWithAdapter(baseConfig, errorAdapter(apiError))
+
+    const result = await agent.run('hello')
+
+    expect(result.success).toBe(false)
+    expect(result.output).toContain('API 500')
+  })
+
+  it('AgentRunner.run() throws when adapter errors', async () => {
+    const apiError = new Error('network timeout')
+    const adapter = errorAdapter(apiError)
+    const registry = new ToolRegistry()
+    const executor = new ToolExecutor(registry)
+    const runner = new AgentRunner(adapter, registry, executor, {
+      model: 'mock-model',
+      systemPrompt: 'test',
+      agentName: 'test',
+    })
+
+    await expect(
+      runner.run([{ role: 'user', content: [{ type: 'text', text: 'hi' }] }]),
+    ).rejects.toThrow('network timeout')
+  })
+
+  it('agent transitions to error state on LLM failure', async () => {
+    const agent = buildAgentWithAdapter(baseConfig, errorAdapter(new Error('boom')))
+
+    await agent.run('hello')
+
+    expect(agent.getState().status).toBe('error')
+  })
+})