spectra MCP server

linc-spectra

Attach a debugger to a running Android app (JDWP via kotlin-debug-adapter, or zero-config jdb by fully-qualified name with no sources) or iOS-simulator app (lldb-dap) and read what UI and logcat cannot show — locals at a method hit, exception frames — through 14 MCP tools.

Install

Prerequisites: Python 3.13+ (stock macOS python3 is older; uv tool install linc-spectra fetches its own Python 3.13 automatically, whereas running pip or pip3 on an older interpreter fails with No matching distribution found for linc-cli-kit).

Install with uv, pipx, or pip (Python >= 3.13):

• uv tool install linc-spectra
• pipx install linc-spectra
• pip install linc-spectra

uv tool install places spectra (and linc-spectra) in ~/.local/bin; a shell without ~/.local/bin on PATH gets exit code 127 (command not found) — run uv tool update-shell and open a new shell (or add ~/.local/bin to PATH).

Then check your environment with uvx linc-spectra doctor (or spectra doctor once installed):

• What it checks: adb, kotlin-debug-adapter, jdb, lldb-dap (macOS only), xcrun (macOS only), and python (>= 3.13). On macOS, doctor probes the /usr/bin/jdb and /usr/bin/xcrun stubs and reports them as failed until a JDK or Xcode / Command Line Tools is installed.
• Exit codes: exits 0 when at least one debugger lane is usable (Android: adb plus kotlin-debug-adapter or jdb; iOS on macOS: xcrun plus lldb-dap), or exits 1 with a hint: line for every failed check. Pass --json (spectra doctor --json) for a single {ok, checks} JSON object on stdout.

Adapters

• Android — zero-config jdb lane: requires adb (Android SDK platform-tools), a debuggable build (android:debuggable="true"), and jdb (ships with any JDK on PATH). Breaks on methods and exceptions by fully-qualified JVM name without local source files.
• Android — full DAP lane: requires adb, a debuggable build, local source files, and kotlin-debug-adapter. Unpack a release zip from fwcd/kotlin-debug-adapter so adapter/bin/kotlin-debug-adapter is on PATH or installed under ~/tools/kotlin-debug-adapter/ (~/tools/kotlin-debug-adapter/adapter/bin/kotlin-debug-adapter).
• iOS — simulator lane (experimental): requires macOS with Xcode's lldb-dap (checked on PATH first, then resolved via xcrun -f lldb-dap) and xcrun; spectra doctor reports the macOS /usr/bin/jdb and /usr/bin/xcrun stubs as failed until a JDK or Xcode is installed. Simulator only.

Finding your device id

• Android (device / device_serial): run adb devices and use the value in the first (serial) column (for example, emulator-5554).
• iOS Simulator (device / device_serial): run xcrun simctl list devices booted to find the booted simulator UDID, or pass the literal booted.

Quickstart

Register the MCP server and run either the zero-config jdb flow (no local sources) or the full DAP flow:

claude mcp add linc-spectra -- spectra bellows
# Or run directly without a global install:
claude mcp add linc-spectra -- uvx linc-spectra bellows

# Zero-config flow (Android jdb — no local source checkout needed):
#   spectra_method_breakpoint(device="emulator-5554", package="com.example.app", method_fqn="com.example.app.AuthRepository.login")
#   -> trigger the UI in the app
#   -> spectra_method_locals(session_id="<session_id>")

# Full DAP flow (Android kotlin-debug-adapter or iOS lldb-dap):
#   spectra_attach(device="emulator-5554", package="com.example.app", platform="android")
#   -> spectra_breakpoint(session_id="<session_id>", source_path="/abs/path/AuthRepository.kt", lines="42")
#   -> spectra_continue(session_id="<session_id>")
#   -> spectra_stacktrace(session_id="<session_id>")
#   -> spectra_variables(session_id="<session_id>", frame_id=0)  # 0 = stopped thread's top frame, or an id from spectra_stacktrace
#   -> spectra_detach(session_id="<session_id>")

MCP Tools (14)

linc-spectra exposes 14 MCP tools grouped by workflow.

DAP Session

Tool	Description
spectra_attach	Attach a DAP debugger to a running debuggable app (Android JDWP or iOS Simulator LLDB)
spectra_detach	Detach the debugger, remove port forwards, and clean up the session
spectra_sessions	List all active debug sessions

Stepping

Tool	Description
spectra_breakpoint	Set file:line breakpoints on local source files
spectra_continue	Resume execution and wait for the next breakpoint or stop event
spectra_step	Step next (over), in (into), or out (out of the current frame)

Inspection

Tool	Description
spectra_stacktrace	Get the call stack for the stopped thread
spectra_variables	Inspect local and scope variables at a stack frame
spectra_evaluate	Evaluate an expression in the current frame context (REPL at a breakpoint)

Zero-Config jdb

Tool	Description
spectra_method_breakpoint	Arm a zero-config breakpoint on a method by fully-qualified name (<class>.<method>) with no local sources
spectra_method_locals	Harvest captured local variables from an armed spectra_method_breakpoint hit
spectra_exception_breakpoint	Arm a zero-config exception catchpoint by fully-qualified exception class name
spectra_exception_info	Harvest the throwing frame, thread, and locals from an armed spectra_exception_breakpoint

Analytics

Tool	Description
spectra_usage_stats	Aggregate per-tool call counts, latency percentiles, and error rates from $LINC_HOME/mcp-calls.jsonl

Limitations

• Upstream kotlin-debug-adapter exception breakpoints do not work: use spectra_exception_breakpoint (the jdb catchpoint) instead.
• file:line breakpoints report verified: true even without local sources: kotlin-debug-adapter marks non-existent paths as verified even though they can never bind; spectra_breakpoint attaches a warning field when source_path is missing locally (use spectra_method_breakpoint when you do not have the source checkout).
• One debugger per process: a target process exposes a single JDWP connection at a time — detach any active DAP session before arming a jdb session on the same app (and vice versa).
• iOS simulator only: iOS debugging via lldb-dap supports booted iOS simulators on macOS only (experimental; physical iOS devices are not supported).
• iOS spectra_evaluate takes expressions only: iOS expressions run in lldb-dap's expression-only (watch) context and LLDB commands (such as backtick-prefixed commands) are refused.
• jdb renders values as text: a debuggee string containing line breaks can add a fake name = value line to a jdb reply (spectra keeps the first value of a name within a reply).
• Bounded jdb waits and stepping: spectra_method_locals and spectra_exception_info wait at most 180 s (wait_s 0–180), and manual stepping takes max_steps 0–16.
• Python >= 3.13: requires Python 3.13 or newer.

Trust

• No telemetry, no phone-home. spectra runs locally over stdio MCP and opens no network listener; it talks only to your local adb, jdb, kotlin-debug-adapter, xcrun, and lldb-dap processes.
• Local usage log under your control. Every MCP tool call is recorded in $LINC_HOME/mcp-calls.jsonl (default ~/.linc/mcp-calls.jsonl, rotated at 10 MB). Control logging with SPECTRA_USAGE_LOG=off|redacted|full:
  • redacted (default) — sensitive fields (expression and source_path) are replaced by length-only placeholders (<redacted len=N>, no digest), expression text is scrubbed from recorded error strings, and the log file is opened owner-only (0600) with O_NOFOLLOW.
  • off — nothing is written to disk.
  • full — raw parameter values are logged (long strings truncated at 500 characters, byte buffers summarized by length). Opt in only on a machine you trust.
• spectra_evaluate runs code inside the debuggee. By design, spectra_evaluate and the jdb tools execute inside the attached debuggable application. Identifiers that reach adb shell, xcrun simctl, or jdb stdin are validated with strict re.fullmatch patterns before execution. See SECURITY.md for the threat model and vulnerability reporting instructions.

How this repo works

This repository is a release mirror of LINC's private repository — each release lands here as a single commit. Issues are welcome; pull requests are accepted by arrangement (open an issue first). See CONTRIBUTING.md.

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Built by LINC Innovations. Licensed under Apache-2.0.