@davehardy20/pi-compact-plus

Advanced context compaction for Pi with mode-aware triggers, structured summaries, current-focus extraction, content classification, and lightweight checkpoints.

What it adds

Commands

| Command | Description | | --- | --- | | /compact-plus | Manual standard compaction | | /compact-plus hard | Manual hard compaction (aggressive pruning) | | /compact-plus status | Show usage, mode, cooldown state, and last compaction telemetry | | /compact-plus tool-prune status | Show detailed tool-output pruning status | | /compact-plus tool-prune flush | Manually flush pending tool-output batches | | /compact-plus-status | Show package identity, version, and source path | | /checkpoint [note] | Save a lightweight checkpoint without compacting |

Auto-compaction triggers

Compact+ replaces Pi's single-threshold early-compaction trigger with a tiered policy:

| Band | Usage | Behavior | | --- | --- | --- | | Normal | < 65% | No auto-compaction | | Checkpoint candidate | 65–69% | Eligible for checkpoint (no auto-compact) | | Standard | 70–89% | Auto standard compaction | | Hard | ≥ 90% | Auto hard compaction (aggressive pruning) |

Auto-compaction is triggered at message_end and turn_end with cooldown and regrowth guards to avoid thrashing.

Structured summaries

Compact+ produces structured compaction summaries with these sections:

• Current Objective
• Current Task State
• Active File Set
• Repository State
• Decisions Made
• Completed Work
• Open Problems
• Current Errors
• Known Constraints
• Failed Attempts
• Next Best Step
• Continuity Instruction
• Dependency Chain

Focus echo

After compaction, a compact "focus echo" is injected at the recency position (before the last user message) to mitigate "lost in the middle" degradation. The echo contains the objective, active files, blockers, decisions, dependency chain, and next step.

Compact+ currently injects the echo as a synthetic user-context message because Pi extension custom messages serialize to provider user messages, and the context hook does not yet expose a provider-preserved lower-authority memory role. The echo is therefore explicitly framed as generated, non-authoritative memory and sanitized so it cannot masquerade as a fresh user request. Revisit this fallback if Pi exposes a context/memory role that remains below user, developer, and system authority across supported providers.

Experimental tool-output pruning

Compact+ includes an experimental, default-off tool-output pruning subsystem. It is inspired by the MIT-licensed pi-context-prune project and reuses or adapts selected pi-context-prune ideas and implementation patterns where they fit Compact+'s architecture.

When enabled, Compact+:

1. Captures eligible tool results after each assistant turn.
2. Summarizes them with an LLM call after the final assistant message.
3. Replaces the original text content with compact recovery stubs in future model context.
4. Persists bounded metadata-only summary entries for branch-safe recovery reconstruction after reloads.
5. Preserves recovery through a built-in query tool (compact_plus_query_tool_output).

Safety defaults:

• Off by default; requires explicit enablement.
• Only the safe agent-message mode is implemented. Summarization happens after the agent's final text response.
• Only text-only tool results are eligible; images, binaries, and mixed content are skipped.
• Protected exclusions are non-overridable: read, read_hashed, hashline_edit, compact_plus_query_tool_output, and Compact+ internal tools are never eligible, even if user include/exclude settings change.
• User excluded/included tool settings only apply after protected exclusions.
• Original toolResult messages are preserved in the session branch. Pruning only affects future context snapshots by stubbing content, not deleting messages.
• Durable pruning metadata never stores original tool output. It stores bounded record ids, entry ids, tool call ids, tool names, summaries, argument previews, and counters needed to reconstruct the runtime index safely.
• Capture, pending/finalized state, metadata reconstruction, summarizer inputs, query scanning, and query output are bounded with hard internal limits so long sessions degrade by trimming/skipping instead of growing without bound.
• Summarization is atomic: a flushed batch is indexed/pruned only when every pending record has a non-empty summary tied to its short ref.
• Metadata reconstruction is atomic: malformed active-version metadata, over-limit payloads, duplicates, excluded tools, stale branch entries, or mismatched entryId/toolCallId/tool-name pairs reconstruct no records.

Attribution and reuse: Batch capture, LLM semantic summarization, short refs, branch-aware indexing, and recovery-query behavior were adapted from pi-context-prune (MIT). Compact+ does not copy the standalone extension wiring; it integrates the reused/adapted pieces into Compact+ settings, state, telemetry/status, lifecycle hooks, and context composition. Source files that closely follow or adapt pi-context-prune mechanics include attribution comments.

Features

• Content classification: Messages are classified as critical, contextual, or ephemeral for hard-mode pruning.
• Tool pair restoration: Tool call/result pairs are kept atomic after pruning.
• Summary normalization: Compaction summaries are normalized and validated before injection.
• Session persistence: Telemetry state is persisted across sessions.
• Model change reset: State resets when the model changes.
• Tool-output pruning (experimental): LLM-summarized tool output stubs with recovery query tool.

Install

From npm:

pi install npm:@davehardy20/pi-compact-plus

From git:

pi install git:github.com/davehardy20/pi-compact-plus

From a local checkout during development:

pi install /Users/dave/tools/pi-compact-plus

For one run only:

pi -e /Users/dave/tools/pi-compact-plus

Settings

Compact+ supports threshold tuning through either environment variables or your Pi agent settings.json file at ~/.pi/agent/settings.json. Environment variables take precedence over settings.json values.

Default profile: checkpoint candidate at 65%, standard compaction at 70%, hard compaction at 90%.

| Variable | Default | Description | | --- | --- | --- | | COMPACT_PLUS_CHECKPOINT_THRESHOLD | 65 | Checkpoint-candidate threshold | | COMPACT_PLUS_STANDARD_THRESHOLD | 70 | Standard compaction threshold | | COMPACT_PLUS_HARD_THRESHOLD | 90 | Hard compaction threshold | | COMPACT_PLUS_COOLDOWN_MS | 120000 | Auto-compaction cooldown in ms | | COMPACT_PLUS_SETTINGS_PATH | ~/.pi/agent/settings.json | Optional JSON config path | | COMPACT_PLUS_EXPERIMENTAL_TOOL_OUTPUT_PRUNING | false | Enable experimental tool-output pruning | | COMPACT_PLUS_TOOL_OUTPUT_PRUNING_MODE | off | Pruning mode (off or agent-message) | | COMPACT_PLUS_TOOL_OUTPUT_SUMMARY_STRATEGY | llm | Summary strategy (llm only for v1) | | COMPACT_PLUS_TOOL_OUTPUT_PRUNE_STRATEGY | stub | Prune strategy (stub or delete; v1 uses stub) | | COMPACT_PLUS_TOOL_OUTPUT_PRUNE_MIN_CHARS | (default) | Minimum tool output chars to be eligible | | COMPACT_PLUS_TOOL_OUTPUT_SUMMARY_MAX_CHARS | (default) | Max chars per LLM summary | | COMPACT_PLUS_TOOL_OUTPUT_QUERY_MAX_CHARS | (default) | Max chars returned by recovery query | | COMPACT_PLUS_TOOL_OUTPUT_SUMMARIZER_MODEL | default | Summarizer model (default or provider/model-id) | | COMPACT_PLUS_TOOL_OUTPUT_SUMMARIZER_THINKING | low | Thinking level; see notes below | | COMPACT_PLUS_TOOL_OUTPUT_PRUNE_EXCLUDED_TOOLS | (comma list) | Additional user exclusions | | COMPACT_PLUS_TOOL_OUTPUT_PRUNE_INCLUDED_TOOLS | (comma list) | User include allow-list |

Tool-output pruning notes:

• Summarizer thinking values: default, off, minimal, low, medium, high, or xhigh.
• User exclusions add tools to skip; protected exclusions still apply.
• User includes are evaluated after protected exclusions; empty means all eligible tools.

Example settings.json:

{
  "thresholds": {
    "checkpoint": 65,
    "standard": 70,
    "hard": 90
  },
  "cooldownMs": 120000,
  "experimentalToolOutputPruning": true,
  "toolOutputPruningMode": "agent-message",
  "toolOutputSummaryStrategy": "llm",
  "toolOutputPruneStrategy": "stub"
}

Top-level keys are also supported: checkpointThresholdPercent, standardThresholdPercent, hardThresholdPercent, and cooldownMs. Invalid, missing, or overlapping thresholds fall back safely to the default 65 / 70 / 90 threshold profile.

Threshold and cooldown constants are resolved when the extension module loads, so changes to those values require /reload or a Pi restart. Tool-output pruning settings are resolved when pruning commands and lifecycle events run, but /reload is still the safest way to apply settings edits consistently.

Notes

• Compact+ hooks into Pi's session_before_compact event to provide custom summarization.
• On Pi runtimes that support stream-aware compaction but do not expose the live session streamFn to extensions, Compact+ uses the public @earendil-works/pi-ai streamSimple adapter so custom summaries can still run.
• If custom summarization still fails after that, Compact+ falls back to Pi's default compaction.
• The extension persists telemetry to ~/.pi/agent/state/compact-plus-telemetry.json.
• State resets when the model changes to avoid stale compaction context from a different model.

Tool-output pruning recovery

V1 appends compact-plus-tool-prune-summary entries for summary visibility, observability, and metadata-only reconstruction. Legacy top-level fields (timestamp, refs, summaryChars, recordCount) remain for status/history compatibility. Newer entries also include a nested schema-versioned metadata payload that is used only after it is validated against the current active branch.

On reload or branch-tree updates, Compact+ reconstructs finalized pruning records only when pruning is effectively enabled and metadata matches current branch tool-result entries by entryId, toolCallId, tool name, tool-result role, and text-only content. Older summary entries without metadata are skipped safely. Active-version metadata that is malformed, oversized, duplicated, excluded by protected/user policy, or stale fails closed and reconstructs no records.

Compact+ always registers a recovery query tool so recovery stubs can point to an available tool, but execution remains inactive and throws unless pruning is effectively enabled:

• Name: compact_plus_query_tool_output
• Parameters: query, recordId, ref, toolCallId, toolName, limit, includeContent

Use this tool to recover original output by short ref or search terms. Query results are bounded by record count, scanned record count, per-record original text scan chars, total original text scan chars, and max returned chars. Full content recovery requires includeContent=true and is limited by toolOutputQueryMaxChars plus hard internal scan/result-size caps. Even after metadata reconstruction, original content is read only from the current branch's existing tool-result messages; it is not read from persisted metadata.

Caveats:

• LLM summarization adds latency and token cost per batch.
• Summaries may omit details; always verify against original output before relying on exact text, line numbers, diagnostics, or hashes.
• Stubbed content is labeled as historical data, not instructions, to reduce prompt-injection risk from captured tool output.
• Branch navigation (e.g., switching to a different session branch) removes stale index records automatically. Metadata from stale branches is rejected during reconstruction.
• Sub-agents currently run with --no-extensions and do not inherit pruning behavior.

Troubleshooting

Run /compact-plus-status to confirm:

• package name and version
• loaded source path
• package root
• current compaction state
• a one-line tool-output pruning status when the experimental feature is enabled

Run /compact-plus status for detailed runtime state:

• current usage percent, tokens, and context window
• usage source (native or estimated)
• current band and thresholds
• when Pi has not produced a post-compaction assistant usage yet, status will show usage as unknown instead of estimating from the pre-compaction branch
• cooldown state
• last compaction telemetry including mode, trigger source, path, thinking level, compatibility notes, fallback reason, and focus files
• the latest persisted focus echo derived from the most recent custom compaction summary
• a one-line tool-output pruning status when the experimental feature is enabled

Run /compact-plus tool-prune status for detailed pruning state:

• enabled/mode/strategy
• indexed record count in the current branch
• pending batch/record counts
• whether a flush is in progress
• last summary status and time
• last metadata reconstruction status, scanned counts, skipped legacy entries, and a bounded non-sensitive error note when reconstruction fails
• protected exclusions plus user excluded/included tools
• summarizer model and thinking level

If commands appear twice, Pi may be loading both the package and the old local extension. Disable or remove the old local auto-discovered extension before reload verification.

Update flow

1. Update the package repo
2. Push to GitHub
3. Run pi update --extensions or reinstall the package
4. Run /reload

/reload alone does not fetch newer package commits.

Architecture and development notes

Runtime source is split into small ownership seams:

• src/index.ts is the Pi extension composition root.
• src/commands.ts, src/events.ts, and src/usage.ts own command wiring, lifecycle/context hooks, and usage lookup.
• src/compaction-coordinator.ts owns manual/auto compaction orchestration and telemetry side effects.
• src/focus-echo/* owns summary detection, parsing, sanitization, rendering, context injection compatibility, and positioning.
• src/tool-output-pruning/* owns experimental pruning capture, summarization, metadata reconstruction, current-branch stubbing, recovery query, commands, and state.

Dev/release playbook:

1. Keep local validation green before opening a PR:

   npm run typecheck
   npm test
   npm run build

2. Run /compact-plus-status after installing from a local checkout or package update to confirm the loaded package name, version, source path, package root, update flow, and pruning one-line status.

3. To pick up a newer published package commit, run pi update --extensions or reinstall the package, then /reload. /reload alone does not fetch package updates.

4. Before release, run npm run package:check for a fast package-content sanity check, then npm run release:check. Release checks run verification, package-content sanity checks, npm whoami, and npm pack --dry-run.

5. Use scripts/release.sh <patch|minor|major> only for an intentional release. --allow-dirty stages tracked changes with git add -u; untracked files must be cleaned or ignored first because npm can pack them from shipped directories.

Build and test

npm run typecheck
npm run build
npm test