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Huge memory occupation by sequentialthinking MCP #2912

Closed
#5397
Closed
Huge memory occupation by sequentialthinking MCP#2912
#5397
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cliffhall
Labels
bugSomething isn't workingserver-sequentialthinkingReference implementation for the Sequential Thinking MCP server - src/sequentialthinkingv2
Milestone
v2.3.0

Description

@MekayelAnik
MekayelAnik
opened on Oct 26, 2025

Describe the bug

After using sequentialthinking for a few hours, the RAM gets hogged up by this MCP server as much as 10GB+ RAM or more (I had this much RAM available, so..). But I doubt it is the Planning, because 10+ GB of Text is a huge amount of text, I DON'T THINK it was the TEXT. I strongly think there is a memory leak.

To Reproduce

  1. Use this MCP for a few (6-8) hours for frequent and long planning

Expected behavior
The memory should be freed after a job is done, or the memory should be offloaded to a disk space after a certain period of time. This should also help with persistent planning (Maybe, add a new tool for this).

Additional context
I have deployed this MCP as a distributed, standalone Docker container.

I love this MCP, a really great project. MANY MANY THANKS to the modelcontextprotocol Team
Regards

Activity

  1. MekayelAnik
    added
    bugSomething isn't working
    on Oct 26, 2025
  2. olaservo
    added
    server-memoryReference implementation for the Memory MCP server - src/memory
    on Oct 29, 2025
  3. olaservo
    added
    server-sequentialthinkingReference implementation for the Sequential Thinking MCP server - src/sequentialthinking
    and removed
    server-memoryReference implementation for the Memory MCP server - src/memory
    on Dec 8, 2025
  4. Limitless2023
    added a commit that references this issue on Feb 11, 2026

    fix(sequentialthinking): prevent unbounded memory growth in thought h…

    ceb2381
  5. cliffhall
    added
    v2
    on Oct 19, 2026

  6. cliffhall commented on Oct 19, 2026

    @cliffhall
    cliffhall
    on Oct 19, 2026
    Member

    Triage: Priority Low (total 5)

    • Severity 2: The sequential-thinking server keeps every thought and branch for the life of a connection with no cap or reset, so memory grows without bound on a long-lived connection; the 10 GB reported likely also involves the third-party container wrapper, which could not be checked.
    • Urgency 2: wanted eventually
    • Bonuses: +1 bug label

    Still present on v2 (checked by reading the current code).

    Board: Servers V2 (#43), Status Incoming, awaiting maintainer review (no milestone yet). Part of the backlog triage in #4875.

  7. cliffhall commented on Oct 20, 2026

    @cliffhall
    cliffhall
    on Oct 20, 2026
    Member

    Prior work, from the PR backlog triage (#4877). These outside pull requests addressed this issue against the pre-refactor code:

    They are being closed as part of the backlog triage in #4875, since the repository now takes issues rather than outside PRs and their diffs predate the v2 refactor. They stay readable and serve as prototypes for the fix here. Thank you to their authors.

  8. cliffhall
    added this to the v2.3.0 milestone on Oct 25, 2026
  9. cliffhall
    added a parent issue on Oct 25, 2026
  10. cliffhall
    self-assigned this
    on Oct 28, 2026
  11. cliffhall
    linked a pull request that will close this issuefix(sequentialthinking): cap the thought history each connection keeps #5397on Oct 29, 2026

  12. cliffhall commented on Oct 29, 2026

    @cliffhall
    cliffhall
    on Oct 29, 2026
    Member

    Fixed by #5397, merged into v2/main. Ships in v2.3.0.

  13. cliffhall
    closed this as completedon Oct 29, 2026
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