pi: stop repeated macos keychain prompts for mcp oauth

08 Sep, 2026 • 312 words • 2 min • updated 29 Sep, 2026

Problem statement: why did Pi keep asking for my macOS login keychain password during MCP OAuth authentication?

/mcp-auth grafana opened the same prompt again after I entered the correct password and selected Allow:

pi wants to use your confidential information stored in “pi-mcp-adapter.oauth” in your keychain.

pi-mcp-adapter stores OAuth credentials in the operating system credential store. Its Grafana record name is a SHA-256 hash:

     shell
     
   
% node -e 'const {createHash}=require("crypto"); console.log("sha256-" + createHash("sha256").update("grafana").digest("hex"))'
sha256-cace491b69555e8d0f77747d47ae54e31ce4cc322fe51a7bdcf64402f3676ebf

The Keychain ACL still allowed old Homebrew Node executables:

     shell
     
   
% security dump-keychain -a | rg -A18 'sha256-cace491b69555e8d0f77747d47ae54e31ce4cc322fe51a7bdcf64402f3676ebf"'
    entry 1:
        authorizations (6): decrypt derive export_clear export_wrapped mac sign
        don't-require-password
        description: pi-mcp-adapter.oauth
        applications (2):
            0: /opt/homebrew/Cellar/node/26.6.0/bin/node (status -67068)
                requirement: cdhash H"ea8d578543c9d8c21b74e26f7976cc30b60e24a5"
            1: /opt/homebrew/Cellar/node/26.5.0_1/bin/node (status -67068)
                requirement: cdhash H"4947cbedfdb054cda3708de8c0b22946c4fd98f1"

Pi now used Homebrew Node 26.8.1 with a different ad-hoc signature:

     shell
     
   
% codesign -dv --verbose=4 /opt/homebrew/Cellar/node/26.8.1/bin/node 2>&1 | rg 'Identifier|CDHash|TeamIdentifier'
Identifier=node-55554944b8d19d4157093cf1805ecde9a77d4850
CandidateCDHash sha256=cead962814af248488bb6597ee22a32fc23d00a1
CandidateCDHashFull sha256=cead962814af248488bb6597ee22a32fc23d00a1aac036bb431b750dd5120163
CDHash=cead962814af248488bb6597ee22a32fc23d00a1
TeamIdentifier=not set

The password was valid. macOS did not trust this new executable to read the old item. Selecting Allow authorized one access, so the next read prompted again.

I removed the base record and its two credential chunks, then authenticated again:

     shell
     
   
% service=pi-mcp-adapter.oauth
% base=sha256-cace491b69555e8d0f77747d47ae54e31ce4cc322fe51a7bdcf64402f3676ebf
% security dump-keychain 2>/dev/null \
    | sed -n 's/^[[:space:]]*"acct"<blob>="\([^"]*\)"/\1/p' \
    | rg "^${base}(\.chunk\.[a-f0-9]{16}\.[0-9]+)?$" \
    | while read -r account; do
        security delete-generic-password -s "$service" -a "$account"
      done
password has been deleted.
password has been deleted.
password has been deleted.

A future Homebrew Node update would change its code hash again. The official Node binary installed by Mise has a stable Developer ID requirement instead:

     shell
     
   
% codesign -dr - ~/.local/share/mise/installs/node/latest/bin/node 2>&1
designated => identifier node and anchor apple generic and certificate 1[field.1.2.840.113635.100.6.2.6] /* exists */ and certificate leaf[field.1.2.840.113635.100.6.1.13] /* exists */ and certificate leaf[subject.OU] = HX7739G8FX

Installing Pi through that Node avoids tying Keychain access to one Homebrew binary hash:

shell

% npm install -g --ignore-scripts @earendil-works/pi-coding-agent

∎

🤖 This post was drafted with an AI agent through /bloggify, then reviewed and edited by me. More agent-assisted posts.

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