[Bug] PRIME_AGENT_KERNEL_PYTHON makes every kernel start about 0.6 s slower

[Wizermil]

Affected area

Coding agent and CLI

What happened?

When PRIME_AGENT_KERNEL_PYTHON is set, ensureKernelPython in packages/coding-agent/src/core/kernel/bootstrap.ts starts a new Python process for each of the 12 default packages (python -c "import pandas", and so on). It does this one after another, and then once more for each Python skill. This runs before every kernel start. Without the override, the uv venv path checks its marker file and skips all of this.

With the same Python, the override path is about 6 times slower.

Steps to reproduce

With the 0.9.6 release and uv on PATH:

prime-agent --prime-agent-bootstrap   # first run creates ~/.prime/agent/kernel-venv
hyperfine 'prime-agent --prime-agent-bootstrap'
PRIME_AGENT_KERNEL_PYTHON=$HOME/.prime/agent/kernel-venv/bin/python \
  hyperfine 'prime-agent --prime-agent-bootstrap'

I get 125 ms without the override and 747 ms with it. It is the same interpreter with the same packages. A real session also probes the 9 bundled skills, so the gap there is bigger.

Expected behavior

Pointing prime-agent at a ready Python should not cost more than letting it manage its own venv.

I patched our build to check all modules in one Python process with importlib.util.find_spec. It returns the same missing-package labels and warnings. --prime-agent-bootstrap went from 1.1 s to about 150 ms with our Nix-built Python, which is slower to import than the uv one. Batching the real imports in one process also works, at about 450 ms. I'm happy to share the patch.

Prime Agent version

0.9.6

Installation method

From source

Operating system

macOS

Operating system version

macOS 27.0 (26A428)

CPU architecture

arm64 / aarch64

Shell and terminal

fish 4.9.3 (not terminal-specific)

[awhite0030]

Investigated this report and produced a candidate fix, validated on a fork of this repository.

Root cause, fix and validation from the working notes:

Root cause: The PRIME_AGENT_KERNEL_PYTHON bootstrap override executed a separate Python subprocess to verify the import of each required dependency via -c import <module>. This sequentially added significant overhead, increasing the bootstrap time from ~150ms to ~750ms.

Fix: Changed the validation functions (missingRlmExtraImportLabels and missingPythonSkillImportLabels) to aggregate required package imports and execute a single inline Python script using importlib.util.find_spec(). This avoids the process invocation overhead while returning all missing packages at once.

Validation: I added a regression test in packages/coding-agent/test/suite/regressions/issue-2875-kernel-bootstrap-perf.test.ts. I verified it by executing cd packages/coding-agent && npx tsx ../../node_modules/vitest/dist/cli.js --run test/suite/regressions/issue-2875-kernel-bootstrap-perf.test.ts which passed. I also verified the full workspace with npm run check which passed.

Upstream discussion: #2875

Diff: awhite0030/prime-agent@main...fix-issue-2875-kernel-bootstrap-perf-1594963900057117039
Full pull request: awhite0030#97

The change passes npm run check and the focused regression tests against current main. If a fix for this is still wanted, I can open a pull request.