Troubleshooting

This page starts from what you see and points to the cause, the fix and the page that explains it. First run npx lousho doctor (what it checks), then, if you have an error code (LOUSHO_...), look it up in Errors.

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Setup

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”No model configured”

• Cause: createAgent() got no model or provider and found nothing in the environment (LOUSHO_CONFIG_MISSING_PROVIDER).
• Fix: pass model: 'openai/gpt-4o-mini' (any <provider>/<model>), or set LOUSHO_MODEL or a provider key such as OPENAI_API_KEY.
• More: Providers, the error.

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”The API key is not set”

• Cause: the provider’s key variable (OPENAI_API_KEY, ANTHROPIC_API_KEY, OPENROUTER_API_KEY) is not in the environment of the process that runs the agent (LOUSHO_PROVIDER_MISSING_API_KEY).
• Fix: set it, or pass a configured provider instance. npx lousho doctor prints set or not set for each key, never the value.
• More: the error.

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”Cannot find package @ai-sdk/openai” or “install the optional peer”

• Cause: each provider is backed by an optional package that is loaded on first use, in the major that pairs with your ai major (LOUSHO_PEER_MISSING). The same error covers the other optional peers, such as dockerode and @modelcontextprotocol/sdk.
• Fix: run the npm install command in the message (it is also on error.installCommand), or look up your ai major in the pairing table.
• More: Provider packages, Optional peers, the error.

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”ai 5 is installed”

• Cause: ai 5 is not supported. The SDK takes ai ^4.3.19, ^6.0.0 or ^7.0.0.
• Fix: install one of those majors together with the provider package row that pairs with it.
• More: Install the package.

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”Top-level await is only available in ES modules”

• Cause: the quick start uses top-level await, so the file must be an ES module.
• Fix: name the file .mts, or set "type": "module" in package.json.
• More: Quickstart in the README.

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The Node version is too old

• Cause: the SDK needs Node.js 22.19 or newer (engines.node).
• Fix: upgrade Node. npx lousho doctor compares your version with the requirement.
• More: Requirements.

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Ollama and zod versions disagree

• Cause: ollama-ai-provider-v2 (the Ollama package for ai 6 and 7) declares zod 4 as a peer. Zod 3 does not satisfy it.
• Fix: use zod 4 with ai 6 or 7, or use ai@^4.3.19 with ollama-ai-provider@^1.2.0.
• More: Provider packages.

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Runs that end without an answer

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send() returned but text is empty

• Cause: a run that stops early resolves; it does not throw. result.finishReason says why. These are the ones that leave text empty or partial:
  • 'awaiting-approval': a tool call needs a human. Resolve it (next entry). Approvals.
  • 'max-steps': the maxSteps budget (default 10) ran out while the model still wanted to continue. Raise maxSteps, or simplify the task. Finish reasons.
  • 'budget-exceeded': a limits budget such as maxTokens or maxCostUsd tripped; result.budget says which. Raise the limit. Budgets.
  • 'guardrail': an input, output or tool guardrail blocked the run; result.guardrail says which. Guardrails.
  • 'output-invalid': the reply did not match the output schema even after the repair step. Structured output.
• Fix: check result.finishReason before reading result.text.

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The run seems stuck on a tool

• Cause: an approval is pending. A paused send() resolves with finishReason: 'awaiting-approval' and an approvalId; nothing runs until someone decides.
• Fix: list the pending calls with agent.approvals.list(), then agent.approvals.resolve({ id, approved }).
• More: createAgent() agents.

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LOUSHO_SESSION_AWAITING_APPROVAL or LOUSHO_SESSION_BUSY

• Cause: a session paused on an approval cannot take new input (LOUSHO_SESSION_AWAITING_APPROVAL); session.compact() or session.clear() was called while a turn was running or queued (LOUSHO_SESSION_BUSY).
• Fix: resolve the approval, then send again; or await the turn’s send() (or abort it), then call again.
• More: awaiting approval, busy.

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Tools

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The model never calls my tool

• Cause: the model decides from the tool’s description and input schema, so a vague description or unclear fields leave it nothing to go on. The name must match ^[a-zA-Z0-9_-]{1,64}$ (1-64 characters of letters, digits, _ and -).
• Fix: say in the description what the tool does and when to use it, and .describe() each input field.
• More: defineTool() options.

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My tool throws and the run goes on

• Cause: this is by design. A tool that throws gives the model an error result ({ error, toolName, message, kind }) and the run continues, so the model can react.
• Fix: if an error must stop the run, throw an error that extends PropagatingToolError; that one rejects the run instead.
• More: Tool errors.

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LOUSHO_TOOL_ARGS_INVALID

• Cause: the model sent arguments that do not match the tool’s input schema. Inside a run it gets the issues back as a result and can retry, so a run seldom ends on it.
• Fix: if the model keeps getting a field wrong, make its .describe() text clearer. If you called the tool yourself, fix the arguments named in the message.
• More: the error.

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Providers and models

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Rate limits and flaky calls

• Cause: the provider throttled the call (LOUSHO_PROVIDER_RATE_LIMITED) or failed transiently.
• Fix: createAgent() already retries a failed call twice; raise it with retry: { maxRetries: 3 }, and set fallbackModels to move on to the next model when the call still fails.
• More: Retries and fallback models, the error.

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The model does not read my files

• Cause: the built-in providers do not send file parts, on any ai major. A file part is sent as a text note ([file report.pdf (application/pdf) not sent]) and the provider warns once. Images are sent.
• Fix: put the file’s text in the message, or use a provider subclass whose model takes files.
• More: Multimodal input.

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I do not see the model’s reasoning

• Cause: reasoning is reported separately from the answer, as reasoning.* events in agent.stream() and as result.reasoning; it is not in result.text. Options are only sent to model families known to accept them, and reasoning: 'none' sends nothing.
• Fix: read result.reasoning or the reasoning.delta events; for a model outside the known families, pass { effort, force: true }.
• More: Reasoning.

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Sandbox, MCP and deployment

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Docker sandbox: “egress is unsupported”

• Cause: a SubprocessSandbox with network: { allow } and a broker needs the broker to be the container’s only way out. Docker Desktop, rootless Docker, a daemon on another machine and an Engine older than 25.0.5 cannot do that, so no container starts (LOUSHO_SANDBOX_EGRESS_UNSUPPORTED). This is refused on purpose rather than granting open egress.
• Fix: run the agent on the Linux host of a Docker Engine 25.0.5 or later, or use network: 'none'.
• More: Sandboxed shell, the error.

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An MCP server’s tools do not appear

• Cause: the servers connect on await agent.ready() or on the first send() / stream(), and a server that cannot connect fails that call. Each tool is named <server>__<tool> (for example docs__search), so look for that name, not the server’s own.
• Fix: await agent.ready() to see the connection error. With connectMcp(), check status(), which maps each server to 'idle', 'connected' or 'failed'; onError: 'skip' leaves a failing server out and warns through logger. MCP needs the optional peer @modelcontextprotocol/sdk.
• More: Connect MCP servers.

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My Worker build rejects the provider or tool

• Cause: the cloudflare-worker target supports the mock, openai and anthropic providers, and the current-date and day-name tools. ollama, openrouter and the http tool are not supported there, and lousho build fails with an error naming the one it rejected.
• Fix: use another provider or tool, or build for the node-server or docker target.
• More: Deployment.

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Getting help

Open an issue at https://github.com/LinuxDevil/agent-sdk/issues. Include:

• the output of npx lousho doctor --json,
• the error code (LOUSHO_...) and the full message,
• the SDK version (npm ls @lousho/build-ai-agent) and your ai version.

Never paste an API key.