[pi-plugin] pi.subagent_extensions resolves non-path sources as relative paths #677

Short description

pi.subagent_extensions passes only npm: entries through unchanged and resolves every other relative entry against ~/.pi/agent. Pi's own loader treats seven prefixes as non-local sources. As a result, builtin:<name>, git:, github:, http(s): and ssh: entries reach the child as nonexistent files, and ~/ entries are resolved as relative paths.

What happened?

The allowlist becomes one --extension flag per entry. Only absolute paths and npm: entries are passed as given; everything else is resolved against the agent directory.

Example: pi.subagent_extensions = ["git:github.com/owner/repo"] becomes --extension <agent-dir>/git:github.com/owner/repo.

Source: packages/pi-plugin/src/subagent-runner.ts, resolveSubagentExtensionEntry (v0.49.0, around lines 599–603).

Expected

Pi's own rule. In @earendil-works/pi-coding-agent 1.1.0, dist/utils/paths.js treats these prefixes as non-local and passes them through unchanged:

npm:, git:, github:, http:, https:, ssh:, builtin:

Everything else is local. Pi also expands ~/ and converts file:// URLs. We should match that list and those two rules.

Affected

• Stock Pi, through git:, github:, https:, ssh:, builtin:, ~/ and file: entries.
• OMP, which shares this resolver.
• Not OpenCode 1 or 2, which have no pi.subagent_extensions, and not the Rust module, which does not spawn Pi children.

builtin:<name> entries come from variants of Pi that compile extensions into their own binary. For example Pi-bolt, a downstream AOT compiled fork of Pi that I run, does this, and it is how I hit the bug. The fix does not depend on this: any builtin: name should reach the child unchanged, and the host decides how it resolves, as with the other keyed entries.

Native settings.json toggles do not apply to allowlisted children. That is intended.

Proposed change

Mirror Pi's prefix list in one constant, with a comment to keep it in step with Pi's isLocalPath(). Then: pass those prefixes through, expand ~/ and file://, keep absolute paths, and resolve anything else against the agent directory as today.

Tests: each prefix passes through; ~/x and file:///x are normalised; relative and absolute entries behave as before.

Reproduction

1. Set pi.subagent_extensions = ["git:github.com/owner/repo"] in ~/.config/cortexkit/magic-context.jsonc.
2. Trigger a historian or dreamer child.
3. Child fails to load selected extension (evidenced in logs/request behaviour eg. in my case where it is a required provider extension - model not found)

Harness coverage

• OpenCode 1 and 2: not applicable, no pi.subagent_extensions.
• Pi: covered by the change.
• OMP: covered by the change, shared resolver. Needs an explicit check.
• Rust module: not applicable.

Environment

• Magic Context: fork base v0.49.0; upstream master as of this report.
• Pi: @earendil-works/pi-coding-agent 1.1.0 (also Pi-Bolt 0.8.5 for the builtin: case)
• Platform: Linux x64, NixOS.
• Client: Pi.

Diagnostics

Forthcoming (pending a clean env and latest upstream magic-context as I'm running a fork with it fixed atm)

Plugin version

0.49.0

OpenCode version

No response

Platform

Linux x64

Client

Pi

Log output (optional)