MCP cdp_heap_sampling_start

Description

Start a lightweight heap allocation sampling capture on the debugged Roku app via CDP HeapProfiler.startSampling.

Requires rk server mode: this tool talks to the server's owned CDP connection, not a private socket. Unlike cdp_heap_snapshot, this does not capture full retained heap content -- it samples allocation call sites over time, which is far cheaper to run continuously. The response is a handle only; call cdp_heap_sampling_stop to end the capture and write the .heapprofile to disk.

Confirmed on-device: this only shows allocations still live when you call cdp_heap_sampling_stop. An allocation site whose objects were all garbage-collected before stop shows zero samples, as if it never allocated -- this is a retained-memory-by-call-site view, not an allocation-churn view. A small or empty profile after real allocation activity means the GC ran, not that capture failed.

Optional parameters:

• sessionId (string): Session id returned by cdp_session_create. Uses the active session when omitted.
• samplingIntervalBytes (number): Average number of bytes allocated between samples. Defaults to
  32768 (32KB) -- Chrome DevTools Protocol's own default. A smaller interval samples more often
  (finer detail, more overhead); a larger interval samples less often.
• output (string): Output .heapprofile file path (must stay within project root). Auto-generated
  under the project root when omitted.

Response:

• captureId (string): Handle used by cdp_heap_sampling_stop.
• samplingIntervalBytes (number): The interval actually requested.

Notes:

• Only one active heap sampling capture per session is allowed. Duplicate start returns
  409 SAMPLING_ALREADY_ACTIVE.

See also

• HTTP cdpStartHeapSampling (POST /api/cdp/heap/sampling/start)
• rk cdp heap sampling-start

Parameters

additionalProperties: false

sessionId

Session id returned by cdp_session_create. Uses the active session when omitted.

samplingIntervalBytes

Average bytes allocated between samples (default 32768)

output

Output .heapprofile file path (must stay within project root when provided)