fix(pi): guard against null/undefined event in before_agent_start (closes #439)#462
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…oses DietrichGebert#439) The before_agent_start handler accessed event.systemPrompt with no null guard on the event argument. If the pi runtime calls the handler with a falsy event (null or undefined), it throws: TypeError: Cannot read properties of null (reading 'systemPrompt') This crashes the agent before every turn when the event is missing. The input handler on line 159 already uses optional chaining (event?.source, event?.text) — before_agent_start was the only handler that didn't follow this defensive pattern. Fix: - pi-extension/index.js: use event?.systemPrompt ?? "" so a null or missing event never throws; consistent with the input handler style Tests: - pi-extension/test/extension.test.js: three new regression cases: - null event does not throw and still injects instructions - undefined event does not throw and still injects instructions - truthy event without systemPrompt key produces no 'undefined' prefix
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🎯 What: Adds
event?.systemPrompt ?? ""optional chaining in thebefore_agent_starthandler inpi-extension/index.js, replacing the bareevent.systemPromptproperty access.💡 Why: If the pi runtime calls
before_agent_startwith a falsy event (null or undefined), the handler immediately throwsTypeError: Cannot read properties of null (reading 'systemPrompt'), crashing the agent before every session turn. The adjacentinputhandler already usesevent?.sourceandevent?.textdefensively —before_agent_startwas the only handler missing this guard (issue #439).✅ Verification: Added three targeted regression tests to
pi-extension/test/extension.test.jscovering: null event, undefined event, and a truthy event object without asystemPromptkey. All three were failing before the fix and pass after. Full pi-extension suite: 18/18 pass. Full repo suite: 68/69 pass — the single remaining failure is the pre-existingcsv: correct pandas one-liner passestest, which requires apandasinstall and was already failing onmainbefore this change.✨ Result: The
before_agent_starthandler is now robust to any event shape the pi runtime may pass, matching the defensive optional-chaining style used throughout the rest of the extension.