---

name: c-api description: "Guides agents locating Qiskit C headers and library, using qiskit.capi ctypes bindings, and handling public C-API build/link issues." disable-model-invocation: true metadata: disco-role: operating license: Apache 2.0

Qiskit C API workflows

Use this sub-skill when the task involves Qiskit's public C API from Python: locating headers, locating the shared library, using ctypes bindings, planning downstream extension builds, or diagnosing source-build/link failures.

Read next

• references/build-and-link.md for qiskit.capi.get_include(), get_lib(), ctypes access, and source-build notes.
• references/troubleshooting.md for missing headers/library, Rust extension, stale editable install, and direct-link caveats.
• ../../references/installation.md for source-build prerequisites.
• ../../scripts/check_qiskit_environment.py --sections capi for a source-free C-API path check.

Include here

• qiskit.capi.get_include() and qiskit.capi.get_lib().
• Python-space ctypes bindings exposed under qiskit.capi.
• Downstream C-extension or standalone C-library build planning that uses Qiskit's public headers.
• Source-build environment variables and Rust-backed extension diagnostics.

Exclude or route elsewhere

• Python circuit construction belongs in ../circuit/SKILL.md.
• Python transpilation APIs belong in ../transpiler/SKILL.md.
• Backend/provider abstractions belong in ../providers/SKILL.md.
• Generic C or Rust build-system advice not involving Qiskit belongs to a broader build-system skill.

Default route

Start here when the user mentions qiskit.capi, get_include, get_lib, qiskit.h, libqiskit, ctypes wrappers, C extension modules, make c, Rust build failures, or missing _accelerate during a Qiskit source install.

What to remember

• The Python package contains the public C headers and the shared-object library that backs the C API.
• get_lib() is useful for local introspection, but direct linking is not the safest path for distributable Python extensions unless the user understands the ABI caveats.
• Source builds require the supported Rust toolchain and the package build backend; normal wheels should already contain the built extension.