pi-context-manager/docs/plans/2026-04-12-context-manager-implementation.md

Context manager stronger pruning and compaction Implementation Plan

For agentic workers: REQUIRED SUB-SKILL: Use superpowers:subagent-driven-development (recommended) or superpowers:executing-plans to implement this plan task-by-task. Steps use checkbox (- [ ]) syntax for tracking.

Goal: Keep live context flatter by pruning whole older turns, compacting earlier, and injecting only lean resume state.

Architecture: Extend pruning at the context boundary, keep summary artifacts in snapshot/ledger only, and add an extension-managed early-compaction gate driven by observed context usage. Preserve existing commands and ledger semantics while removing footer status noise.

Tech Stack: TypeScript, Node test runner (tsx --test), Pi extension hooks

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Task 1: Turn-aware pruning and lean resume rendering

Files:

• Modify: src/prune.ts

• Modify: src/prune.test.ts

• Modify: src/summaries.ts

• Modify: src/summaries.test.ts

• Modify: src/runtime.ts

• Modify: src/runtime.test.ts

• Step 1: Write the failing prune and resume tests

test("pruneContextMessages drops turns older than the kept suffix", () => {
  const messages = [
    { role: "user", content: "turn 1" },
    { role: "assistant", content: "after turn 1" },
    { role: "user", content: "turn 2" },
    { role: "assistant", content: "after turn 2" },
    { role: "user", content: "turn 3" },
  ];

  const pruned = pruneContextMessages(messages, buildPolicy(2));
  assert.deepEqual(pruned.map((m) => m.content), ["turn 2", "after turn 2", "turn 3"]);
});

test("buildResumePacket keeps blocker text after raw handoff sections are removed", () => {
  const runtime = createContextManagerRuntime({ mode: "balanced", contextWindow: 200_000 });
  runtime.recordCompactionSummary("## Open questions and blockers\n- Verify /tree replaceInstructions behavior.");
  assert.match(runtime.buildResumePacket(), /Verify \/tree replaceInstructions behavior/);
  assert.doesNotMatch(runtime.buildResumePacket(), /## Latest compaction handoff/);
});

• Step 2: Run tests to verify they fail

Run: cd /home/dev/pi-packages/pi-context-manager/.worktree/context-manager-prune-compact && npm test -- src/prune.test.ts src/runtime.test.ts src/summaries.test.ts Expected: FAIL because pruning still keeps old turns and runtime still prepends raw handoff sections.

• Step 3: Write the minimal implementation

// src/prune.ts
// Keep only the last N user-anchored turns.
// Distill bulky tool results only for kept older turns, never for the newest turn.

// src/summaries.ts
export function buildResumePacket(ledger: LedgerState): string {
  return [
    ...lines("Goal", getActiveItems(ledger, "goal").map((item) => item.text)),
    ...lines("Current task", getActiveItems(ledger, "activeTask").map((item) => item.text)),
    ...lines("Constraints", getActiveItems(ledger, "constraint").map((item) => item.text)),
    ...lines("Key decisions", getActiveItems(ledger, "decision").map((item) => item.text)),
    ...lines("Open questions / blockers", getActiveItems(ledger, "openQuestion").map((item) => item.text)),
  ].join("\n").trim();
}

// src/runtime.ts
function buildResumePacket() {
  return renderResumePacket(snapshot.ledger).trim();
}

• Step 4: Run tests to verify they pass

Run: cd /home/dev/pi-packages/pi-context-manager/.worktree/context-manager-prune-compact && npm test -- src/prune.test.ts src/runtime.test.ts src/summaries.test.ts Expected: PASS for the new pruning and lean-resume assertions.

• Step 5: Commit

cd /home/dev/pi-packages/pi-context-manager/.worktree/context-manager-prune-compact
git add src/prune.ts src/prune.test.ts src/summaries.ts src/summaries.test.ts src/runtime.ts src/runtime.test.ts
git commit -m "fix: prune turns and slim resume packets"

Task 2: Context filtering, early compaction, and footer removal

Files:

• Modify: index.ts

• Modify: src/extension.test.ts

• Step 1: Write the failing extension tests

test("context filters raw compaction and branch summary messages", async () => {
  const result = await harness.handlers.get("context")?.({
    type: "context",
    messages: [
      { role: "compactionSummary", summary: "## Key Decisions\n- noisy raw handoff", timestamp: 1 },
      { role: "branchSummary", summary: "# Handoff\n- noisy raw branch", timestamp: 2 },
      createUserMessage("continue", 3),
    ],
  }, harness.ctx);

  assert.ok(result.messages.every((message: any) => message.role !== "compactionSummary" && message.role !== "branchSummary"));
});

test("turn_end triggers early compaction at red zone without footer status writes", async () => {
  const harness = createHarness([], { usageTokens: 150_000 });
  await harness.handlers.get("session_start")?.({ type: "session_start" }, harness.ctx);
  await harness.handlers.get("turn_end")?.({ type: "turn_end", turnIndex: 1, message: createAssistantMessage("done", 5), toolResults: [] }, harness.ctx);
  assert.equal(harness.compactions.length, 1);
  assert.equal(harness.statuses.length, 0);
});

• Step 2: Run tests to verify they fail

Run: cd /home/dev/pi-packages/pi-context-manager/.worktree/context-manager-prune-compact && npm test -- src/extension.test.ts Expected: FAIL because summary messages are still passed through, early compaction is absent, and status writes still occur.

• Step 3: Write the minimal implementation

// index.ts
// - Filter raw compactionSummary / branchSummary messages before pruning.
// - Remove ctx.ui.setStatus(...) calls.
// - After observeTokens on turn_end, call ctx.compact() once when snapshot.lastZone is red/compact.
// - Reset the latch on session_compact or when usage drops below red.

• Step 4: Run tests to verify they pass

Run: cd /home/dev/pi-packages/pi-context-manager/.worktree/context-manager-prune-compact && npm test -- src/extension.test.ts Expected: PASS for summary filtering, early compaction, and no-footer assertions.

• Step 5: Commit

cd /home/dev/pi-packages/pi-context-manager/.worktree/context-manager-prune-compact
git add index.ts src/extension.test.ts
git commit -m "fix: compact earlier and drop status noise"

Task 3: Full verification and cleanup

Files:

• Modify: src/config.ts (only if zone tightening needs a small recent-turn adjustment)

• Modify: src/config.test.ts (only if policy values change)

• Step 1: Run the full test suite

cd /home/dev/pi-packages/pi-context-manager/.worktree/context-manager-prune-compact
npm test

• Step 2: If any failures remain, make the minimal fix and rerun

// Only patch the failing behavior surfaced by the full test run.
// Do not broaden scope beyond pruning, lean resume injection, summary filtering,
// early compaction, and footer removal.

• Step 3: Verify the final green run

Run: cd /home/dev/pi-packages/pi-context-manager/.worktree/context-manager-prune-compact && npm test Expected: # fail 0

• Step 4: Commit final cleanup if needed

cd /home/dev/pi-packages/pi-context-manager/.worktree/context-manager-prune-compact
git add index.ts src/*.ts docs/plans/2026-04-12-context-manager-implementation.md
git commit -m "test: cover context pressure behavior"