[Bug] Dify Cloud: all Workflow apps broken — LLM nodes fail with "Variable key <node>.#sys.query# not found in user inputs."

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Dify version

Dify Cloud (cloud.dify.ai) — status page reports production v1.17.1

Cloud or Self Hosted

Cloud

Steps to reproduce

1. Create a brand-new Workflow app: Start → LLM → End (nothing else).
2. On the LLM node, click "Run this step" (single-step test) and fill any input.
3. The run fails immediately.

✔️ Expected Behavior

The LLM node runs and returns its output.

❌ Actual Behavior

Every LLM node fails with: Variable key llm_test.#sys.query# not found in user inputs. This happens on ALL Workflow apps, including newly created minimal ones, in both single-step tests and full runs. First observed around 2026-10-01 14:30 CST (UTC+8); still broken 20+ hours later.

Why this looks platform-side

• The app DSL contains zero occurrences of #sys.query# (verified repeatedly, including a DSL exported from an affected instance) — no app configuration references it.
• A freshly created 3-node app with no shared configuration reproduces the identical error, ruling out app-level causes.
• #sys.query# is a chatflow-only system variable; it should never be required in Workflow mode. The error is thrown from the backend variable-pool mapping (mapping_user_inputs_to_variable_pool), suggesting a Cloud-side regression injecting a phantom sys.query reference into LLM nodes at runtime.
• status.dify.ai shows all green with no incident posted — the failure is silent there.