qwen-code/docs/developers/daemon/02-serve-runtime.md

Serve Runtime

Overview

packages/cli/src/serve/ is the boot layer for qwen serve. It translates CLI flags into ServeOptions, validates startup configuration, builds the Express app, wires middleware, registers routes, exposes daemon-host preflight/status providers, maintains the permission audit ring, and owns the two-phase graceful shutdown sequence. HTTP-facing work lives in this layer; ACP-facing work lives one layer below in @qwen-code/acp-bridge (see 03-acp-bridge.md).

Responsibilities

• Parse and validate ServeOptions: listen address, auth, workspace, session / connection caps, MCP budget / pool, CORS, prompt / SSE / session idle timeouts, rate limit, and related toggles.
• Canonicalize the primary workspace exactly once, and canonicalize every repeated --workspace before registering session runtimes. The primary canonical form is shared by /capabilities.workspaceCwd, the POST /session fallback, and the primary bridge.
• Reject unsafe or invalid startup configurations: non-loopback bind without token, --require-auth without token, --allow-origin '*' without token, mcpBudgetMode='enforce' without a positive mcpClientBudget, a nonexistent or non-directory --workspace, and invalid timeout or rate-limit values.
• Construct the WorkspaceFileSystem factory, permission audit publisher, DaemonStatusProvider, and acp-bridge.
• Build the Express app, wire middleware (denyBrowserOriginCors / allowOriginCors -> hostAllowlist -> access log -> bearerAuth -> rate limit -> JSON parser -> telemetry -> per-route mutationGate), and mount session, workspace CRUD, file, device-flow auth, permission vote, and ACP HTTP routes.
• Bind the listening port and register signal handlers.
• Run two-phase shutdown on SIGINT/SIGTERM; force-exit on a second signal.

Architecture

Entry: runQwenServe(opts, deps) in packages/cli/src/serve/run-qwen-serve.ts. Returns a RunHandle ({ url, port, close, ... }).

App factory: createServeApp(opts, getPort, deps) in packages/cli/src/serve/server.ts. Builds the Express Application. Direct embedders and tests call it without the bootstrap wrapper.

Capability registry: SERVE_CAPABILITY_REGISTRY in packages/cli/src/serve/capabilities.ts. Each tag has a since version and optional modes. Conditional tags are omitted when their deployment or runtime predicate is false; the registry and predicate map are the source of truth. See 11-capabilities-versioning.md.

Middleware (packages/cli/src/serve/auth.ts and server.ts):

Middleware, in registration order	Purpose	Notes
denyBrowserOriginCors / allowOriginCors	Deny all Origin headers by default; switch to an allowlist when --allow-origin <pattern> is configured.	See 12-auth-security.md.
hostAllowlist(bind, getPort)	On loopback, validate Host belongs to localhost, 127.0.0.1, [::1], or host.docker.internal plus the actual port.	Defense against DNS rebinding. Comparison is case-insensitive and cached per port.
Access-log middleware	Records method, path, status, durationMs, sessionId, and clientId to DaemonLogger when a request finishes.	Registered before bearerAuth, so 401 denials are logged too. Skips /health and heartbeat.
bearerAuth(token)	SHA-256 plus timingSafeEqual constant-time bearer comparison.	Open passthrough when no token is configured (loopback dev default). Bearer scheme is case-insensitive.
Rate-limit middleware	Optional per-tier token bucket for prompt, mutation, and read routes.	Registered after bearerAuth and before JSON parsing; returns 429 before parsing when a bucket is exhausted.
express.json({ limit: '10mb' })	JSON body parsing.	Parse errors return 400.
daemonTelemetryMiddleware	Wraps classified daemon API requests that reach this point in an OpenTelemetry span through withDaemonRequestSpan.	Attributes include canonical route, resolved workspace hash, sessionId, clientId, and status code. Earlier auth, rate-limit, and body-parser rejections are outside this span boundary.
createMutationGate (per-route)	Route-level opt-in gate for mutation routes that require token even on loopback.	Returns 401 { code: 'token_required' }. Not global app.use; routes call mutate({ strict: true }) as needed.

Subsystems:

Path	Role
serve/fs/	WorkspaceFileSystem factory plus policy.ts (size/trust/binary checks), paths.ts (canonicalize, resolveWithin, symlink rejection), audit.ts, and typed FsError values.
serve/routes/workspace-file-read.ts, workspace-file-write.ts	HTTP handlers for GET /file, GET /file/bytes, POST /file/write, and POST /file/edit.
serve/workspace-memory.ts	GET/POST /workspace/memory (QWEN.md CRUD).
serve/workspace-agents.ts	GET/POST/DELETE /workspace/agents (subagent CRUD).
serve/daemon-status-provider.ts	Env snapshot plus daemon-host preflight cells: Node version, CLI entry, workspace stat, ripgrep, git, npm.
serve/permission-audit.ts	PermissionAuditRing (512-entry FIFO) and createPermissionAuditPublisher.
serve/auth/device-flow.ts, qwen-device-flow-provider.ts	Device-flow OAuth routes. See 12-auth-security.md.
serve/daemon-logger.ts	DaemonLogger structured file logs. See 19-observability.md.
serve/debug-mode.ts	Shared isServeDebugMode() predicate controlling verbose error context in HTTP responses.
serve/acp-http/	ACP Streamable HTTP transport (RFD #721), mounted at /acp. Seven files implement JSON-RPC POST, SSE GET, DELETE teardown, and shared bridge usage in parallel with the REST surface.
serve/web-shell-static.ts, serve/web-shell-resolver.ts	Locate and mount the built Web Shell assets (the daemon's browser UI) at /, /assets, and /session/:id, plus the SPA deep-link fallback registered after all API routes. Mounted before bearerAuth in every launch mode — a browser cannot attach Authorization to a navigation or subresource — while every API route it calls stays token-gated. Degrades to API-only when the assets are absent; --no-web opts out.

ACP bridge package imports:

• Event-bus primitives are imported from @qwen-code/acp-bridge/eventBus.
• Status primitives are imported from @qwen-code/acp-bridge/status.
• serve/acp-session-bridge.ts remains as the CLI-local compatibility facade for the broader bridge surface.

Flow

Boot sequence

1. Resolve and trim token from opts.token or QWEN_SERVER_TOKEN; this avoids a trailing newline from cat token.txt silently breaking bearer comparison.
2. Hostname typo guard: --hostname localhost:4170 errors and suggests --port.
3. Auth preflight: non-loopback without token refuses; --require-auth without token refuses.
4. Workspace validation: absolute path, exists, directory. EACCES / EPERM are wrapped to point at the flag.
5. Canonicalize workspace: canonicalizeWorkspace(rawWorkspace) runs realpathSync.native once and feeds /capabilities, the POST /session fallback, and the bridge.
6. MCP budget validation: positive integer; enforce requires a budget.
7. MCP pool toggle inference: parent env QWEN_SERVE_NO_MCP_POOL=1 makes mcpPoolActive=false, so capabilities honestly omit mcp_workspace_pool and mcp_pool_restart.
8. CORS / timeout / rate-limit validation: --allow-origin '*' requires token; prompt, writer, channel idle, session idle, reaper, and rate-limit window values fail fast when invalid.
9. Per-handle childEnvOverrides: pass QWEN_SERVE_MCP_CLIENT_BUDGET and QWEN_SERVE_MCP_BUDGET_MODE to the ACP child through BridgeOptions.childEnvOverrides instead of mutating process.env.
10. Load settings.json once: read context.fileName, policy.permissionStrategy, and policy.consensusQuorum. Corrupt files fall back to defaults. validatePolicyConfig() checks policy.* against SERVE_CAPABILITY_REGISTRY.permission_mediation.modes; unknown strategies or non-positive consensusQuorum throw InvalidPolicyConfigError. A quorum set under a non-consensus strategy logs a stderr warning.
11. Allocate PermissionAuditRing (512 entries).
12. Build fsFactory: runQwenServe defaults to trusted: true; direct createServeApp callers default to trusted: false and warn once.
13. createHttpAcpBridge, see 03-acp-bridge.md.
14. createServeApp assembles Express.
15. server.listen(port, hostname), then resolve the actual getPort() for host allowlist.
16. Register SIGINT / SIGTERM handlers for graceful shutdown.

Graceful shutdown

1. Phase 1 - bridge teardown on first signal:
   • Dispose the device-flow registry and cancel pending flows.
   • bridge.shutdown() marks each channel isDying = true, sends graceful close to each ACP child stdin, waits KILL_HARD_DEADLINE_MS (10s) per channel, then calls channel.kill() if needed.
2. Phase 2 - HTTP teardown:
   • server.close() stops accepting new connections and lets in-flight requests finish.
   • SHUTDOWN_FORCE_CLOSE_MS (5s) triggers server.closeAllConnections().
   • A second 2s deadline escalates again if needed.
3. Second signal while exiting:
   • bridge.killAllSync() + process.exit(1) to avoid orphaned children blocking daemon exit.

State and lifecycle

RunHandle exposes:

• url: resolved listen URL, after ephemeral port resolution.
• port: actual port, including 0 resolution.
• close({ timeoutMs? }): programmatic shutdown for embedders and tests.

Calling createServeApp directly returns only an Application; the embedder owns listen and shutdown.

Dependencies

Upstream used by serve/	Downstream using serve/
@qwen-code/acp-bridge: bridge, event bus, status types	The qwen CLI serve subcommand handler
packages/core: loadSettings, getCurrentGeminiMdFilename, Config, WorkspaceContext	Direct embedders, tests
ACP SDK (@agentclientprotocol/sdk): PROTOCOL_VERSION, ClientSideConnection through bridge
Express + body-parser, node:crypto, node:fs, node:path

Configuration

Source	Key	Effect
Env	QWEN_SERVER_TOKEN	Bearer token after trim.
Env	QWEN_SERVE_NO_MCP_POOL=1	Forces mcpPoolActive=false.
ACP child env	QWEN_SERVE_MCP_CLIENT_BUDGET / QWEN_SERVE_MCP_BUDGET_MODE	Generated from --mcp-client-budget / --mcp-budget-mode and forwarded through childEnvOverrides.
Env	QWEN_SERVE_PROMPT_DEADLINE_MS / QWEN_SERVE_WRITER_IDLE_TIMEOUT_MS	Default prompt / SSE idle timeouts.
Env	QWEN_SERVE_RATE_LIMIT*	Rate-limit switch, prompt / mutation / read caps, and window default.
Env	QWEN_SERVE_DEBUG=1	Verbose stderr logs. See 19-observability.md.
Flags	--hostname, --port	Listen binding.
Flags	--token, --require-auth, --enable-session-shell	Bearer token, loopback auth hardening, and explicit shell execution switch.
Flag	--workspace	Overrides process.cwd(); repeat to register additional isolated workspace runtimes.
Flags	--max-sessions, --max-pending-prompts-per-session, --max-connections, --event-ring-size	Bridge / Express caps.
Flags	--mcp-client-budget=N, --mcp-budget-mode={off,warn,enforce}	Forwarded to the ACP child.
Flags	--allow-origin, --allow-private-auth-base-url	Browser CORS allowlist and localhost/private auth provider installation switch.
Flag	--web / --no-web	Serve or skip the Web Shell UI at the daemon root (default serves). --no-web leaves the daemon API-only.
Flags	--prompt-deadline-ms, --writer-idle-timeout-ms, --channel-idle-timeout-ms, --initialize-timeout-ms	Prompt, SSE writer, ACP child idle lifecycle, and ACP child request timeout control.
Flags	--session-reap-interval-ms, --session-idle-timeout-ms	Disconnected-session reaping control.
Flags	--rate-limit*	Per-tier HTTP rate limit.
settings.json	policy.permissionStrategy, policy.consensusQuorum	MultiClientPermissionMediator policy and quorum.
settings.json	context.fileName	getCurrentGeminiMdFilename override for the bridge.

See 17-configuration.md for the merged reference.

Caveats and known limits

• Direct createServeApp without deps.fsFactory or deps.bridge defaults to trusted: false; agent-side ACP writeTextFile rejects as untrusted_workspace. The warning is printed once.
• denyBrowserOriginCors rejects all requests carrying Origin; the loopback Web Shell works because another middleware strips matching loopback same-origin values first — non-loopback binds require --allow-origin for the shell's XHRs.
• Body-parser ordering: routes using mutate({ strict: true }) return 401 only after express.json(). The worst case is --max-connections × express.json({limit: '10mb'}), up to about 2.5 GB of transient memory on a saturated loopback listener; this tradeoff is intentional.
• Multiple daemons in one process must use per-handle childEnvOverrides; mutating process.env races because defaultSpawnChannelFactory snapshots env at spawn time.

References

• packages/cli/src/serve/run-qwen-serve.ts (bootstrap, boot validation, graceful shutdown)
• packages/cli/src/serve/server.ts (createServeApp(), middleware and route assembly)
• packages/cli/src/serve/auth.ts (CORS, Host allowlist, bearer auth, mutation gate)
• packages/cli/src/serve/rate-limit.ts (per-tier HTTP rate limit)
• packages/cli/src/serve/capabilities.ts (capability registry and conditional advertisement)
• packages/cli/src/serve/types.ts (ServeOptions, CapabilitiesEnvelope)
• packages/cli/src/serve/daemon-status-provider.ts
• packages/cli/src/serve/permission-audit.ts
• Issues: #3803, #4175