Provides tools for loading and reasoning about Linux Kconfig trees, explaining why configuration symbols are unavailable, finding verified dependency fixes, setting symbols, comparing and saving .config files, and searching Kconfig symbols.
Click on "Deploy Server".
Wait a few minutes for the server to deploy. Once ready, it will show a "Started" state.
In the chat, type @ followed by the MCP server name and your instructions, e.g., "@kconfig-mcp why can't I enable CONFIG_X86_X2APIC, and what's the smallest fix?"
That's it! The server will respond to your query, and you can continue using it as needed.
Here is a step-by-step guide with screenshots.
"Why can't I enable CONFIG_X?", answered with file:line and a fix that's been checked.
kconfig-mcp is an MCP server that lets an AI agent reason about Kconfig, the configuration system used by the Linux kernel, Zephyr, U-Boot, Buildroot and others.
Everyone who has configured a kernel has hit this: the option you want isn't in
menuconfig, or it's there but greyed out, and the reason is five depends on hops
away in a different directory. kconfig-mcp walks that chain for you. Then it searches
for the smallest set of changes that would unlock the option, and applies them to
the real tree to verify they work before it shows them to you.
This is real output on the current Linux tree (18,913 symbols) for x86:
> kconfig_why_not X86_X2APIC
X86_X2APIC = n (default), needs y - bool at arch/x86/Kconfig:463
its prompt (arch/x86/Kconfig:463) is visible only if
X86_LOCAL_APIC && X86_64 && (IRQ_REMAP || HYPERVISOR_GUEST), which is n:
needs any one of (2 options, all currently too low):
IRQ_REMAP = n (default), needs y - bool at drivers/iommu/Kconfig:201
its prompt is visible only if X86_64 && X86_IO_APIC && PCI_MSI && ACPI && IOMMU_SUPPORT:
PCI_MSI = n (default), needs y - bool at drivers/pci/Kconfig:44
its prompt is visible only if PCI, which is n:
PCI = n (default) - set PCI=y directly.
HYPERVISOR_GUEST = n (default), needs y - bool at arch/x86/Kconfig:787
its prompt is visible - set HYPERVISOR_GUEST=y directly.
Verified fix (2 change(s)): HYPERVISOR_GUEST=y, X86_X2APIC=y
HYPERVISOR_GUEST: arch/x86/Kconfig:787
X86_X2APIC: arch/x86/Kconfig:463
Unverified alternatives: PCI=y, PCI_MSI=y, IRQ_REMAP=y, X86_X2APIC=y
> kconfig_set HYPERVISOR_GUEST y
CONFIG_HYPERVISOR_GUEST: 'n' -> 'y'.
1 other symbol(s) changed as a consequence: X86_X2APIC n->yThe same question on a 32-bit build (ARCH=i386) ends somewhere no symbol change can
reach, and the tool says so instead of inventing a fix:
64BIT = n (default), needs y - bool at arch/x86/Kconfig:3
requires "i386" = "x86", which compares two constants and is always false here.
One side was probably expanded from an environment variable (like $(ARCH)) when
the tree was loaded: no symbol change can fix this - reload with a different env.
No verified fix: every route ends in something no assignment can change.Related MCP server: codegraph-mcp
Fixes are verified, not guessed. Kconfig is full of edge cases: tristate m
needs MODULES, bools promote m to y, choices deselect their other members,
select overrides depends on, and default y turns things on silently. So every
candidate plan is applied to the loaded tree and checked. Only plans that really
reach the goal are shown as fixes, together with their side effects (what else
select/imply/defaults switch on or off).
It parses current Linux. It's built on Kconfiglib, which hasn't had a release
since 2020 and can't parse Linux's newer modules, transitional and
depends on X if Y syntax. kconfig-mcp rewrites those lines as files are read,
keeping every line number exact. depends on X if Y is lowered with a line-by-line
port of expr_trans_compare from scripts/kconfig/expr.c, so it behaves exactly
as kconfig does, including how kconfig treats !S when S is m.
Environment problems are named. Linux sources arch/$(SRCARCH)/Kconfig, and an
unset variable silently becomes "". kconfig-mcp tracks undefined variables and
names them in the error (undefined variable(s): SRCARCH (the arch/ directory to use, ...)) instead of leaving you with arch//Kconfig not found.
pip install kconfig-mcp
claude mcp add kconfig -- kconfig-mcpPython 3.10+. You don't need a kernel build environment. A source tree with its Kconfig files is enough, even a sparse checkout:
git clone --depth 1 --filter=blob:none --sparse https://github.com/torvalds/linux.git
cd linux && git sparse-checkout set --no-cone '/Kconfig' '**/Kconfig*' '/arch/*/configs/*'Tree |
|
Linux |
|
Linux, no compiler / Windows | the same plus |
Any other tree | the top-level |
shell controls the tree's $(shell,...) calls, which is how Linux probes the
compiler:
"run" (default) runs them with a POSIX sh, as make menuconfig would.
Compiler-dependent symbols then reflect your real toolchain.
"dry" runs nothing. Linux's probe idioms get fixed answers: feature probes
read as absent, and the toolchain reports as GCC 13.2. $(error-if) checks become
warnings. Results then carry a note that compiler-dependent symbols such as
CC_HAS_* read as absent.
Tool | What it does |
| Parse a tree (plus optional |
| The unmet conditions behind |
| Type, prompt, value and why it has that value, assignable values, dependencies, defaults, select/imply in both directions, help text. |
| Every symbol that selects or implies this one, with current values and which are active. |
| Regex search over names, prompts and help, with name matches first. |
| Assign a value as menuconfig would, and report every other symbol that changed. A refused assignment says so. |
| Compare with another |
| Write |
| Manage loaded trees. |
Symbol names work with or without CONFIG_. A misspelt name gets "Did you mean: ...".
transitional symbols are always n. Real kconfig reads them from an old
.config to migrate a value during a rename. Kconfiglib has no equivalent.
The fix search is bounded. Selects and defaults are only explored when a symbol can't be reached through its own prompt, and the search has an expansion budget. If no verified fix is found, the result says whether the budget ran out or every route is genuinely blocked.
why_not covers bool and tristate symbols. For int/hex/string symbols, use
kconfig_symbol and kconfig_set.
Dry mode answers compiler probes generically (see above), so trust
CC_HAS_*-style symbols only with shell="run" on a real toolchain.
It depends on Kconfiglib 14.1.0, pinned because compat.py hooks two of its
internal methods. CI parses the latest Linux tree every week, so the next new
keyword shows up as a failing build rather than a silent wrong answer.
pip install ".[test]" "ruff==0.16.0" "mypy==2.3.0"
ruff check src tests && mypy --strict src
pytest tests # unit + stdio tests, fixture trees
LINUX_SRC=/path/to/linux pytest tests/test_linux_integration.pyThe fixture tree in tests/fixtures/tree exercises every construct the explainer
handles: depends on, select, imply, choice, visible if, menuconfig/if blocks,
defaults, tristate and modules, and an arch directory chosen by $(SRCARCH). The
Linux tests assert real facts, such as x2APIC's dependencies, the i386 dead end, and
the x86_64 defconfig already enabling it. CI runs them against a sparse checkout of
the current tree.
MIT. Kconfiglib is ISC-licensed.
Compare the session's current values with another config file.
A full .config lists every symbol that has a value, so a bool/tristate missing from it is n - that's the default. For a defconfig or a config fragment (only the interesting lines), pass fragment=True to compare just the symbols the file mentions.
Inputs: name (required), other_config (required), limit, fragment. Returns: result
Parse a Kconfig tree (and optionally a .config) into a session named name.
kconfig_path is the top-level Kconfig file; its directory becomes srctree.
env supplies the variables the tree expands - Linux needs SRCARCH and ARCH
(e.g. {"SRCARCH": "x86", "ARCH": "x86_64"}); Zephyr needs ZEPHYR_BASE and
friends. Missing ones are named in the error.
shell: "run" executes the tree's $(shell,...) compiler probes with a POSIX sh,
as make menuconfig would. "dry" runs nothing (no compiler needed, works on
Windows); compiler-feature symbols then read as absent.
A Linux tree takes 10-40 s to parse; the session stays loaded.
Inputs: name (required), kconfig_path (required), env, shell, +1 more. Returns: result
Write the current configuration. minimal=True writes a defconfig-style file with only the values that differ from defaults.
Inputs: name (required), path (required), minimal. Returns: result
Find symbols whose name, prompt or help text matches query
(case-insensitive; a regex is accepted). Name matches rank first.
Inputs: name (required), query (required), limit. Returns: result
List loaded sessions.
Inputs: no named parameters. Returns: result
Assign a value (y/m/n for bool/tristate; a number or string otherwise) as if in menuconfig, then report everything else that changed as a result. If the value doesn't stick (hidden prompt, unmet dependency, choice rules) it says so - use kconfig_why_not to see why.
Inputs: name (required), value (required), symbol (required). Returns: result
Everything about one symbol: type, prompt, current value and why, help text, where it's defined, its dependencies, and what selects/implies it.
Inputs: name (required), symbol (required). Returns: result
Forget a loaded session.
Inputs: name (required). Returns: result
Who forces this symbol on (select), who suggests it (imply), and what it selects/implies itself - with current values and locations.
Inputs: name (required), symbol (required). Returns: result
Explain why a symbol isn't (or can't be) at value, and how to fix it.
Walks every unmet depends on, visible if, if block, choice and
select/default condition with file:line, recursing into the symbols they
name. Then searches for a minimal set of assignments and VERIFIES it by
applying it to the tree - a fix is only shown if Kconfig agrees it works,
along with its side effects. value: "y", "m", or "n" (why can't I turn it off?).
Inputs: name (required), symbol (required), value. Returns: result
Recent tool additions, removals, and schema changes observed during successful MCP inspections.
Loading tool schema changelog…
Scored across 10 tools
Each tool has a distinct role: load/unload/list sessions, search symbols, inspect one symbol, set a value, diagnose why a value cannot be set, inspect select/imply relationships, save, and diff. kconfig_set and kconfig_why_not are complementary rather than overlapping: set attempts an assignment and why_not explains failures and verified fixes.
All tools use a consistent kconfig_ prefix and snake_case, making the namespace predictable. Most names are action-oriented, though kconfig_sessions and kconfig_symbol are noun-based rather than verb-based, a minor deviation from the otherwise consistent convention.
Ten tools is well-scoped for a Kconfig exploration and configuration server. Each tool covers a meaningful part of the workflow without obvious redundancy or excessive granularity.
The surface covers the core lifecycle: loading a tree/session, searching and inspecting symbols, setting values, diagnosing failures, examining select/imply relationships, saving, and diffing configs. A minor gap is the lack of an explicit menu-structure or full-symbol-listing tool, though search and symbol inspection can work around this.
Ask a codebase what calls what: search, blast radius, paths between symbols, and diffs.
Persistent memory, hybrid search and a goal graph for AI agents, over stdio or remote HTTP.
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