adaptive-compaction

name: adaptive-compaction description: >- Adaptive add-on policy and recovery layer that decides WHEN to compact, prune, snapshot, or fork -- replacing fixed-percent auto-compaction across Claude Code, Codex, and MCP-capable hosts. Trigger on auto-compact timing or damage: "when should I compact", "is it safe to compact now or start a fresh session", "auto-compact fires too early/mid-task", "switching to an unrelated task but the window still has space", "context rot", "answers get worse the longer the session runs", "the agent forgot the plan or my decisions after it summarized", "add a layer on top that manages context without changing the agent", raising autoCompactWindow to give the policy room, or installing/tuning a cross-tool compaction policy or PreCompact hook -- even when "compaction" is never said but the problem is context-window pressure or post-summarization memory loss. Do NOT use to summarize a conversation, build RAG, write a summarization prompt (decides WHEN not HOW), or answer max-context-length trivia. allowed-tools: Read, Bash, Write, Edit

Adaptive Compaction

Use this skill to install, inspect, or operate the adaptive compaction policy and recovery layer for coding agents. Keep the layer add-on only: decide when to preserve, prune, compact, fork, or ask; never rewrite the host agent core.

Operating Rules

Follow these rules before taking action:

1. Preserve state before any risky compaction path.
2. Run zero-LLM pruning before any LLM summary recommendation.
3. Treat relevance as advisory. Never use low relevance alone for destructive action.
4. Prefer fork/reset on topic shift when headroom is healthy.
5. Enforce FORCED_COMPACT only on hook-rich hosts. Degrade Codex and MCP-only hosts to advise/persist.
6. Keep stable instructions before volatile state to avoid prompt-cache churn.
7. Log every decision with thresholds and host capability tier.
8. Use portable paths such as <skill-dir>/scripts/decide.py; do not hardcode install paths.
9. When the per-turn additionalContext reports a non-NOOP action, lead your next reply by surfacing it to the user in their language (forced compaction needed, fork recommended, decision needs confirmation). Then continue with the user's actual request. Do not silently swallow these signals — that is the only channel by which the skill can ask the user to act.

Load References Conditionally

Do not read every reference by default. Load only the rows needed for the current request.

Workflow

1. Classify Host Capability

Classify the host before choosing behavior:

Load <skill-dir>/references/capability-matrix.md when the host behavior is disputed or user-facing.

2. Score Signals

Prepare host telemetry matching <skill-dir>/references/contract.md, then run:

python3 <skill-dir>/scripts/score_signals.py < telemetry.json > signals.json

Use the scorer output as the only input to the decision table. Do not add model calls in v1.

3. Decide Action

Run:

python3 <skill-dir>/scripts/decide.py < signals.json > decision.json

Accept only these actions:

• NOOP
• ZERO_LLM_PRUNE
• SAVE_STATE
• PREPARE_FOR_COMPACT
• FORCED_COMPACT
• FORK_OR_RESET
• ASK_USER

If FORCED_COMPACT appears outside hook-rich, treat it as a bug. The decider should downgrade it to PREPARE_FOR_COMPACT.

4. Act on the Decision

Use this table:

For pruning:

python3 <skill-dir>/scripts/prune_zero_llm.py < telemetry.json > prune.json

For state:

python3 <skill-dir>/scripts/state_packet.py < state-input.json > state-result.json

5. Log the Decision

Always append a JSONL decision entry:

python3 <skill-dir>/scripts/decision_log.py < log-input.json > log-result.json

Include the selected action, headroom, relevance, burden, continuity flags, host tier, thresholds, and snapshot requirement.

Hook Assets

Claude Code

Use <skill-dir>/assets/hooks/claude-code/ for hook-rich enforcement:

• pre-compact.sh calls <skill-dir>/scripts/hook_bridge.py claude-pre-compact.
• session-start.sh calls <skill-dir>/scripts/hook_bridge.py claude-session-start.
• user-prompt-submit.sh calls <skill-dir>/scripts/hook_bridge.py claude-user-prompt-submit.
• settings.json shows the hook configuration snippet.

The PreCompact path is the only v1 host-scoped native FORCED_COMPACT path. It snapshots first, then allows or blocks compaction according to the decision table.

Set ADAPTIVE_COMPACTION_SKILL_DIR=<skill-dir> if the shell scripts are copied outside the skill folder. Set ADAPTIVE_COMPACTION_DIR to choose the runtime directory for TASK_STATE.md, transcript dumps, decision logs, and quarantine files.

Codex

Use <skill-dir>/assets/hooks/codex/ for advise/persist integration:

• hooks.json routes session, prompt, and stop events into <skill-dir>/scripts/hook_bridge.py.
• config.toml contains a compact prompt snippet that asks native compaction to preserve the state packet shape.

Never claim Codex server compaction content is controlled or auditable. Snapshot externally and log advice.

Hook Bridge

Use <skill-dir>/scripts/hook_bridge.py only as a host adapter. It normalizes hook JSON, imports the scorer/decider/pruner/state/log scripts, writes runtime artifacts, and emits hook-friendly JSON. Keep policy in the scripts and references, not in host assets.

How the Decision Is Made (so you can reason about it)

Runtime autonomy does NOT come from the agent deciding anything per turn. The host harness fires hooks deterministically; each hook runs zero-token Python (score_signals.py -> decide.py). There is no per-turn LLM call in v1. The skill description only matters when a human asks to install/tune/explain the policy -- it is NOT the runtime trigger. These are two separate planes; keep them separate when explaining to the user.

The four signals and how each is judged (all deterministic, see <skill-dir>/references/decision-policy.md for exact formulas):

• Headroom = free context fraction from token counts. Pure arithmetic.
• Relevance = lexical + structural overlap of the new prompt vs the current objective / hot files / touched symbols / plan. No model call; advisory only -- never the sole cause of a destructive action.
• Burden = estimated reclaimable tokens: duplicate reads, superseded writes, errored-tool inputs, oversized tool outputs.
• Continuity = open edit / failing test / unresolved tool error / uncheckpointed plan flags. High continuity blocks mid-task compaction.

decide.py runs the canonical table in references/decision-policy.md over these four plus the host capability tier, emitting one action.

Install It Yourself

If you can edit the host config, set this up directly instead of asking the user to do it by hand:

1. Wire the hooks. Add <skill-dir>/assets/hooks/claude-code/ PreCompact, SessionStart, and UserPromptSubmit entries to settings.json (snippet in that folder). Set ADAPTIVE_COMPACTION_SKILL_DIR to the installed skill path and ADAPTIVE_COMPACTION_DIR to a runtime dir. For Codex, install <skill-dir>/assets/hooks/codex/hooks.json + config.toml.
2. Give the adaptive policy room (raise the native trigger). Native auto-compaction can fire on its own threshold before this policy's preferred action runs. Because this layer is adaptive, push the native trigger LATER so the policy decides first:

Raising the native trigger is real insurance here (the host exposes it), but the PreCompact block/allow boundary remains the primary mechanism: snapshot first, then block if policy says "not yet / fork", or allow with state-packet-preserving instructions. This IS the v1 host-scoped FORCED_COMPACT seam. Never claim full prevention of native compaction on a host that exposes no interception seam (MCP-only).

Script Index

Fixture Check

Run fixture checks after editing scripts or hook bridge behavior:

for f in <skill-dir>/scripts/fixtures/case_[abcd]*.json \
         <skill-dir>/scripts/fixtures/case_review_explicit_marker.json; do
  python3 <skill-dir>/scripts/score_signals.py < "$f" \
    | python3 <skill-dir>/scripts/decide.py
done

for f in <skill-dir>/scripts/fixtures/*_signals.json; do
  python3 <skill-dir>/scripts/decide.py < "$f"
done

Run at least one hook bridge smoke test:

python3 <skill-dir>/scripts/hook_bridge.py claude-user-prompt-submit \
  < <skill-dir>/scripts/fixtures/case_c_relevant_space_ok.json

Output Discipline

When reporting results:

• State the host tier and chosen action.
• State whether a snapshot was required and where it was written.
• State whether behavior was enforce, advise/persist, or persist-only.
• Mention any downgrade, especially Codex opaque compaction or MCP-only hosts.
• Keep recovered-token claims secondary to continuity and task-success claims.