Scope SessionStart hook to Copilot Studio projects only

[hectorfitch-coder]

Problem

The SessionStart hook in hooks/hooks.json has no matcher/condition, so hooks/system-prompt.md (~11KB of "act as manager, delegate to the Advisor/Author/Manage/Test sub-agents" routing rules) is injected into every session — including ones with nothing to do with Copilot Studio. I hit this when the prompt showed up in an unrelated session in a non-CS repository.

Why it matters

Beyond the constant context overhead, the prompt instructs a strong "bias toward assuming the request is about Copilot Studio" and that "using skills directly is FORBIDDEN". In a non-CS session those directives apply unless the model explicitly disregards them.

Fix

Gate the injection on the plugin's own definition of a Copilot Studio project — an agent.mcs.yml in the working directory or a subdirectory (exactly what system-prompt.md already uses to detect "already inside a Copilot Studio project"). When no marker is found, print-prompt.js exits without output.

A SessionStart hook runs before any user message, so it cannot read user intent; the project marker is the only reliable signal available at that point.

Changes

• hooks/print-prompt.js — adds a bounded hasCopilotStudioProject(cwd, depth 4, ≤2000 dirs) check (skips node_modules/.git/build dirs) and process.exit(0)s when no marker is present. The existing Copilot-CLI-JSON vs Claude-Code-raw output branch is unchanged.
• hooks/hooks.json — repoints the inline command variant (previously read system-prompt.md directly) at the now-gated print-prompt.js, so the gate is the single source of truth across the command/bash/powershell variants. setup.js is untouched.

Verification

• No marker in cwd → print-prompt.js produces 0 bytes (nothing injected).
• agent.mcs.yml present (incl. nested subdirectory) → full prompt injected as before.
• hooks.json parses as valid JSON; print-prompt.js passes node --check.

Notes / trade-offs

• This changes behaviour for CS work started in a directory that does not yet contain an agent.mcs.yml (e.g. cloning a brand-new agent from scratch). system-prompt.md already documents the clone-first flow, and users can also mention "Copilot Studio" explicitly; happy to add an env-var/opt-in escape hatch (e.g. COPILOT_STUDIO_ALWAYS_ON=1) if you'd prefer one.
• Scan depth (4) and dir cap (2000) are conservative defaults — easy to tune.

🤖 Generated with Claude Code

[hectorfitch-coder]

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