diff --git a/apps/agent-worker/src/agent-events.ts b/apps/agent-worker/src/agent-events.ts
index 7dbec21..e5663fd 100644
--- a/apps/agent-worker/src/agent-events.ts
+++ b/apps/agent-worker/src/agent-events.ts
@@ -357,6 +357,114 @@ export const normalizeCodexJsonLine = (
   return events;
 };
 
+// Claude Code `--output-format stream-json` emits one JSON object per line:
+// `system:init` announces the session id, `assistant` messages carry text and
+// tool_use blocks, `user` messages carry tool_result blocks, and `result`
+// terminates the turn (success with final text, or an `error_*` subtype).
+export const normalizeClaudeJsonLine = (
+  line: string,
+): NormalizedAgentEvent[] => {
+  if (!line.trim()) return [];
+  let parsed: unknown;
+  try {
+    parsed = JSON.parse(line) as unknown;
+  } catch {
+    return [{ kind: 'status', status: line }];
+  }
+  const event = asRecord(parsed);
+  if (!event) return [{ kind: 'status', status: line }];
+  const type = stringify(event.type);
+  const subtype = stringify(event.subtype);
+  const events: NormalizedAgentEvent[] = [];
+
+  if (type === 'system') {
+    const sessionId = stringify(event.session_id);
+    if (subtype === 'init' && sessionId) {
+      events.push({ kind: 'session', sessionId });
+    }
+    if (events.length === 0) {
+      events.push({ kind: 'status', status: subtype || 'system' });
+    }
+    return events;
+  }
+
+  if (type === 'assistant') {
+    const message = asRecord(event.message);
+    const content = message?.content;
+    let text = '';
+    if (Array.isArray(content)) {
+      for (const block of content) {
+        const record = asRecord(block);
+        if (!record) continue;
+        const blockType = stringify(record.type);
+        if (blockType === 'text') {
+          text += textFromPart(record);
+        } else if (blockType === 'tool_use') {
+          events.push({
+            kind: 'tool_started',
+            name: stringify(record.name ?? 'tool'),
+            input: JSON.stringify(record.input ?? {}),
+          });
+        }
+      }
+    }
+    if (text) events.unshift({ kind: 'assistant_delta', content: text });
+    if (events.length === 0) {
+      events.push({ kind: 'status', status: 'assistant' });
+    }
+    return events;
+  }
+
+  if (type === 'content_block_delta') {
+    const delta = asRecord(event.delta);
+    const text = delta ? textFromPart(delta) : '';
+    if (text) events.push({ kind: 'assistant_delta', content: text });
+    if (events.length === 0) {
+      events.push({ kind: 'status', status: type });
+    }
+    return events;
+  }
+
+  if (type === 'user') {
+    const message = asRecord(event.message);
+    const content = message?.content;
+    if (Array.isArray(content)) {
+      for (const block of content) {
+        const record = asRecord(block);
+        if (!record || stringify(record.type) !== 'tool_result') continue;
+        events.push({
+          kind: 'tool_completed',
+          name: 'tool',
+          output: toolOutputFromRecord(record),
+        });
+      }
+    }
+    if (events.length === 0) {
+      events.push({ kind: 'status', status: 'user' });
+    }
+    return events;
+  }
+
+  if (type === 'result') {
+    const sessionId = stringify(event.session_id);
+    if (sessionId) events.push({ kind: 'session', sessionId });
+    if (subtype === 'success') {
+      events.push({
+        kind: 'assistant_completed',
+        content: stringify(event.result),
+      });
+    } else {
+      events.push({
+        kind: 'error',
+        message: stringify(event.result ?? event.error ?? subtype),
+      });
+    }
+    return events;
+  }
+
+  return [{ kind: 'status', status: type || line }];
+};
+
 export const normalizeOpenCodeEvent = (
   input: unknown,
 ): NormalizedAgentEvent[] => {
diff --git a/apps/agent-worker/src/runtime/auth.ts b/apps/agent-worker/src/runtime/auth.ts
new file mode 100644
index 0000000..cec04b5
--- /dev/null
+++ b/apps/agent-worker/src/runtime/auth.ts
@@ -0,0 +1,20 @@
+import { mkdir, writeFile } from 'node:fs/promises';
+import path from 'node:path';
+
+// Normalize + pretty-print an auth JSON blob before writing it with owner-only
+// permissions. Shared by the credential-writing adapters (Claude, and available
+// to Codex/OpenCode). `label` names the source in the parse-error message.
+export const writeJsonFile = async (
+  filePath: string,
+  content: string,
+  label = 'auth',
+) => {
+  let normalized = content.trim();
+  try {
+    normalized = `${JSON.stringify(JSON.parse(normalized), null, 2)}\n`;
+  } catch {
+    throw new Error(`${label} JSON is not valid JSON.`);
+  }
+  await mkdir(path.dirname(filePath), { recursive: true });
+  await writeFile(filePath, normalized, { mode: 0o600 });
+};
diff --git a/apps/agent-worker/src/runtime/claude-adapter.ts b/apps/agent-worker/src/runtime/claude-adapter.ts
new file mode 100644
index 0000000..50a5839
--- /dev/null
+++ b/apps/agent-worker/src/runtime/claude-adapter.ts
@@ -0,0 +1,127 @@
+import path from 'node:path';
+import { randomUUID } from 'node:crypto';
+
+import type { NormalizedAgentEvent } from '../agent-events';
+import { normalizeClaudeJsonLine } from '../agent-events';
+import { env } from '../env';
+import type { AdapterFactory, TurnResult } from './agent-runtime';
+import { writeJsonFile } from './auth';
+import {
+  buildMarkedCommand,
+  killBoxProcessesByMarker,
+  streamExecInContainer,
+} from './docker';
+import type { AdapterWorkspace } from './provider';
+import { claudeEnv, claudeModel, isClaudeOAuthProfile } from './provider';
+
+export const createClaudeAdapter: AdapterFactory = (deps) => {
+  const execStream = deps?.execStream ?? streamExecInContainer;
+
+  const prepareAuth = async (workspace: AdapterWorkspace) => {
+    // API-key profiles authenticate purely via ANTHROPIC_API_KEY in the
+    // environment; only OAuth-json profiles need `.credentials.json` on disk.
+    if (!isClaudeOAuthProfile(workspace.claim)) return;
+    const secret = workspace.claim.aiProviderProfile?.secret;
+    if (!secret) {
+      throw new Error('Claude auth profile is missing credentials.json contents.');
+    }
+    const credentialsPath = path.join(
+      workspace.homeDir,
+      '.claude',
+      '.credentials.json',
+    );
+    await writeJsonFile(credentialsPath, secret, 'Claude auth');
+  };
+
+  const runTurn = async (
+    workspace: AdapterWorkspace,
+    prompt: string,
+    onEvent: (event: NormalizedAgentEvent) => Promise<void>,
+  ): Promise<TurnResult> => {
+    workspace.runtime = 'claude';
+    workspace.turnMarker = `spoon-turn-${randomUUID()}`;
+    const marker = workspace.turnMarker;
+
+    // NOTE: exact flags are UNVERIFIED against the pinned CLI and are confirmed
+    // in Task 11's smoke. `--verbose` is required for `stream-json`;
+    // `--resume <sessionId>` carries continuity.
+    const argv = [
+      'claude',
+      '-p',
+      prompt,
+      '--output-format',
+      'stream-json',
+      '--verbose',
+      '--dangerously-skip-permissions',
+      '--model',
+      claudeModel(workspace.claim),
+      ...(workspace.claudeSessionId
+        ? ['--resume', workspace.claudeSessionId]
+        : []),
+    ];
+    const command = buildMarkedCommand(marker, argv);
+
+    const aiEnv = claudeEnv(workspace.claim, workspace.containerHome);
+    const secretEnv = Object.fromEntries(
+      workspace.claim.secrets.map((secret) => [secret.name, secret.value]),
+    );
+
+    let capturedSessionId: string | undefined;
+    let capturedError: string | undefined;
+    let finalMessage: string | undefined;
+
+    // execa's own `timeout` only kills the local docker-exec client, not the
+    // in-box process group. Schedule an explicit marker kill on timeout and clear
+    // it once the exec resolves.
+    const killTimer = setTimeout(() => {
+      void killBoxProcessesByMarker({
+        containerName: workspace.boxName,
+        marker,
+      });
+    }, env.jobTimeoutMs);
+
+    let result;
+    try {
+      result = await execStream({
+        containerName: workspace.boxName,
+        containerCwd: workspace.containerRepo,
+        command,
+        environment: { ...aiEnv, ...secretEnv },
+        redact: workspace.redact,
+        timeoutMs: env.jobTimeoutMs,
+        onStdoutLine: async (line) => {
+          for (const event of normalizeClaudeJsonLine(line)) {
+            if (event.kind === 'session') capturedSessionId = event.sessionId;
+            if (event.kind === 'error') capturedError = event.message;
+            if (event.kind === 'assistant_completed' && event.content) {
+              finalMessage = event.content;
+            }
+            await onEvent(event);
+          }
+        },
+        onStderrLine: async (line) => {
+          if (!line.trim()) return;
+          await onEvent({ kind: 'status', status: line });
+        },
+      });
+    } finally {
+      clearTimeout(killTimer);
+    }
+
+    if (result.exitCode !== 0) {
+      capturedError = result.output;
+    }
+
+    return { finalMessage, sessionId: capturedSessionId, error: capturedError };
+  };
+
+  const abort = async (workspace: AdapterWorkspace) => {
+    if (!workspace.turnMarker) return;
+    await killBoxProcessesByMarker({
+      containerName: workspace.boxName,
+      marker: workspace.turnMarker,
+    });
+  };
+
+  return { name: 'claude', prepareAuth, runTurn, abort };
+};
diff --git a/apps/agent-worker/src/runtime/provider.ts b/apps/agent-worker/src/runtime/provider.ts
index 37580df..4b4c705 100644
--- a/apps/agent-worker/src/runtime/provider.ts
+++ b/apps/agent-worker/src/runtime/provider.ts
@@ -169,3 +169,31 @@ export const codexModel = (claim: Claim) => {
 
 export const codexModelArgs = (claim: Claim) =>
   isCodexLoginProfile(claim) ? [] : ['--model', codexModel(claim)];
+
+// Claude Code OAuth profiles store their credentials as a JSON blob written to
+// `~/.claude/.credentials.json`; API-key profiles authenticate via
+// ANTHROPIC_API_KEY. Mirrors the OpenCode adapter's `opencode_auth_json` signal.
+export const isClaudeOAuthProfile = (claim: Claim) =>
+  claim.aiProviderProfile?.authType === 'opencode_auth_json';
+
+// The `claude --model` flag expects a bare model id (e.g. `claude-sonnet-4`),
+// so strip any `provider/` prefix like codexModel does.
+export const claudeModel = (claim: Claim) => {
+  const model = claim.aiProviderProfile?.model ?? claim.openai.model;
+  return model.includes('/') ? (model.split('/').at(-1) ?? model) : model;
+};
+
+// Environment for a `claude -p` turn. OAuth-json profiles authenticate from the
+// on-disk credentials file (only HOME is needed); API-key profiles export
+// ANTHROPIC_API_KEY.
+export const claudeEnv = (
+  claim: Claim,
+  containerHome: string,
+): Record<string, string> => {
+  if (isClaudeOAuthProfile(claim)) return { HOME: containerHome };
+  const secret = claim.aiProviderProfile?.secret ?? claim.openai.apiKey;
+  if (!secret) {
+    throw new Error('No Anthropic API key is configured for this Claude job.');
+  }
+  return { ANTHROPIC_API_KEY: secret, HOME: containerHome };
+};
diff --git a/apps/agent-worker/src/runtime/register.ts b/apps/agent-worker/src/runtime/register.ts
index bc8def2..7a71ac7 100644
--- a/apps/agent-worker/src/runtime/register.ts
+++ b/apps/agent-worker/src/runtime/register.ts
@@ -1,6 +1,8 @@
 import { registerAdapter } from './agent-runtime';
+import { createClaudeAdapter } from './claude-adapter';
 import { createCodexAdapter } from './codex-adapter';
 import { createOpenCodeAdapter } from './opencode-adapter';
 
 registerAdapter('codex', createCodexAdapter);
 registerAdapter('opencode', createOpenCodeAdapter);
+registerAdapter('claude', createClaudeAdapter);
diff --git a/apps/agent-worker/tests/unit/agent-events.test.ts b/apps/agent-worker/tests/unit/agent-events.test.ts
index a55066e..075e9e7 100644
--- a/apps/agent-worker/tests/unit/agent-events.test.ts
+++ b/apps/agent-worker/tests/unit/agent-events.test.ts
@@ -1,6 +1,7 @@
 import { describe, expect, test } from 'vitest';
 
 import {
+  normalizeClaudeJsonLine,
   normalizeCodexJsonLine,
   normalizeOpenCodeEvent,
   normalizeOpenCodeRunLine,
@@ -329,4 +330,73 @@ describe('agent event normalization', () => {
       status: 'not json at all',
     });
   });
+
+  test('normalizes Claude Code stream-json output lines', () => {
+    expect(
+      normalizeClaudeJsonLine(
+        JSON.stringify({
+          type: 'system',
+          subtype: 'init',
+          session_id: 'abc',
+        }),
+      ),
+    ).toContainEqual({ kind: 'session', sessionId: 'abc' });
+
+    expect(
+      normalizeClaudeJsonLine(
+        JSON.stringify({
+          type: 'assistant',
+          message: {
+            content: [
+              { type: 'text', text: 'hello ' },
+              { type: 'text', text: 'world' },
+            ],
+          },
+        }),
+      ),
+    ).toContainEqual({ kind: 'assistant_delta', content: 'hello world' });
+
+    expect(
+      normalizeClaudeJsonLine(
+        JSON.stringify({
+          type: 'assistant',
+          message: {
+            content: [
+              { type: 'tool_use', name: 'Bash', input: { command: 'ls' } },
+            ],
+          },
+        }),
+      ),
+    ).toContainEqual({
+      kind: 'tool_started',
+      name: 'Bash',
+      input: JSON.stringify({ command: 'ls' }),
+    });
+
+    expect(
+      normalizeClaudeJsonLine(
+        JSON.stringify({
+          type: 'result',
+          subtype: 'success',
+          result: 'final text',
+          session_id: 'abc',
+        }),
+      ),
+    ).toContainEqual({ kind: 'assistant_completed', content: 'final text' });
+
+    expect(
+      normalizeClaudeJsonLine(
+        JSON.stringify({
+          type: 'result',
+          subtype: 'error_max_turns',
+          result: 'hit the turn limit',
+        }),
+      ),
+    ).toContainEqual({ kind: 'error', message: 'hit the turn limit' });
+
+    expect(normalizeClaudeJsonLine('not json at all')).toContainEqual({
+      kind: 'status',
+      status: 'not json at all',
+    });
+  });
 });
diff --git a/apps/agent-worker/tests/unit/claude-adapter.test.ts b/apps/agent-worker/tests/unit/claude-adapter.test.ts
new file mode 100644
index 0000000..fd8f6d2
--- /dev/null
+++ b/apps/agent-worker/tests/unit/claude-adapter.test.ts
@@ -0,0 +1,110 @@
+import { describe, expect, test, vi } from 'vitest';
+
+import type { NormalizedAgentEvent } from '../../src/agent-events';
+import type { ExecStreamFn } from '../../src/runtime/agent-runtime';
+import type { AdapterWorkspace, Claim } from '../../src/runtime/provider';
+
+const loadAdapter = async () => {
+  process.env.SPOON_WORKER_TOKEN = 'test-worker-token';
+  process.env.GITHUB_APP_ID = '123';
+  process.env.GITHUB_APP_PRIVATE_KEY =
+    '-----BEGIN PRIVATE KEY-----\\ntest\\n-----END PRIVATE KEY-----';
+  return await import('../../src/runtime/claude-adapter');
+};
+
+const claim = {
+  job: {
+    _id: 'job-1',
+    prompt: 'hi',
+    baseBranch: 'main',
+    workBranch: 'spoon/x',
+    forkOwner: 'o',
+    forkRepo: 'r',
+    upstreamOwner: 'u',
+    upstreamRepo: 'r',
+  },
+  spoon: { name: 'Spoon' },
+  openai: { model: 'claude-sonnet-4', reasoningEffort: 'medium' },
+  aiProviderProfile: {
+    id: 'p',
+    name: 'Anthropic',
+    provider: 'anthropic',
+    authType: 'api_key',
+    secret: 'sk-ant-test',
+    model: 'claude-sonnet-4',
+    reasoningEffort: 'medium',
+  },
+  github: {},
+  secrets: [],
+} as unknown as Claim;
+
+const makeWorkspace = (): AdapterWorkspace => ({
+  claim,
+  workdir: '/tmp/spoon-claude-adapter-test-missing',
+  homeDir: '/tmp/spoon-claude-adapter-test-missing',
+  username: 'tester',
+  containerHome: '/home/tester',
+  containerRepo: '/home/tester/Code/spoon',
+  repoDir: '/tmp/spoon-claude-adapter-test-missing/Code/spoon',
+  boxName: 'spoon-box-tester',
+  redact: (value: string) => value,
+  runtime: 'claude',
+});
+
+describe('ClaudeCodeAdapter', () => {
+  test('streams normalized events and marks the turn via buildMarkedCommand', async () => {
+    const { createClaudeAdapter } = await loadAdapter();
+    const captured: unknown[] = [];
+    const execStream = vi.fn(async (args) => {
+      captured.push(args.command);
+      await args.onStdoutLine?.(
+        JSON.stringify({
+          type: 'system',
+          subtype: 'init',
+          session_id: 'abc',
+        }),
+      );
+      await args.onStdoutLine?.(
+        JSON.stringify({
+          type: 'assistant',
+          message: { content: [{ type: 'text', text: 'hi there' }] },
+        }),
+      );
+      await args.onStdoutLine?.(
+        JSON.stringify({
+          type: 'result',
+          subtype: 'success',
+          result: 'final text',
+          session_id: 'abc',
+        }),
+      );
+      return { exitCode: 0, output: '' };
+    }) as unknown as ExecStreamFn;
+
+    const adapter = createClaudeAdapter({ execStream });
+    const events: NormalizedAgentEvent[] = [];
+    const onEvent = (event: NormalizedAgentEvent): Promise<void> => {
+      events.push(event);
+      return Promise.resolve();
+    };
+
+    const result = await adapter.runTurn(makeWorkspace(), 'do it', onEvent);
+
+    expect(events).toContainEqual({ kind: 'session', sessionId: 'abc' });
+    expect(events).toContainEqual({
+      kind: 'assistant_delta',
+      content: 'hi there',
+    });
+    expect(result.finalMessage).toBe('final text');
+    expect(result.sessionId).toBe('abc');
+    expect(result.error).toBeUndefined();
+
+    // The turn ran through buildMarkedCommand (setsid bash session) carrying the
+    // `claude -p` argv in the script.
+    const command = captured[0] as string[];
+    expect(command[0]).toBe('setsid');
+    expect(command[1]).toBe('bash');
+    expect(command[3]).toContain("'claude' '-p'");
+    expect(command[3]).toContain("'--output-format' 'stream-json'");
+  });
+});