Context Engineering & Observability

You want to actively manage the context window itself: see what’s in it, measure cost, decide what to keep or evict, plan a budget, and reach for the deeper “power” tools. This journey documents the advanced and meta tools that don’t belong to a single everyday flow — the ones that make LeanCTX a context runtime, not just a compressor.

Most tools here are in the power profile. Enable them with lean-ctx tools power, or load just one category at runtime with ctx_load_tools (see §6).

1. See what’s in the context — observability

Before managing context, you measure it.

Tool	CLI	What it answers
ctx_radar	—	Full budget breakdown: prompt, messages, tools, reads, shell
ctx_metrics	lean-ctx stats	Session token stats, cache hit-rates, per-tool savings
ctx_context	—	Session-context overview: cache, files seen, current state
ctx_cost	lean-ctx gain --cost	Local cost attribution per agent / per tool
ctx_heatmap	lean-ctx heatmap	File-access heatmap (hot vs. cold files)

ctx_radar format=display      # human-readable context budget
ctx_radar format=json         # machine-readable, for dashboards

ctx_radar is the single best “where are my tokens going?” view: it attributes the live context window across system prompt, message history, tool schemas, file reads, and shell output. Pair it with ctx_metrics for cumulative savings.

2. Context Field Theory — actively shape the window

LeanCTX models the context window as a field you can manipulate with overlays (exclude, pin, prioritize) rather than only react to.

ctx_control / lean-ctx control

Overlay-based manipulation. Overlays apply at a scope (call, session, or project) and are reversible.

lean-ctx control pin src/auth.rs --reason "active task"
lean-ctx control exclude vendor/ --scope session
lean-ctx control set_priority src/main.rs --value high
lean-ctx control list            # current overlays
lean-ctx control history         # what changed and why
lean-ctx control reset           # drop overlays

Actions: exclude, include, pin, unpin, set_view, set_priority, mark_outdated, reset, list, history.

ctx_ledger / lean-ctx ledger — pressure management

The ledger tracks per-file context “pressure” (token cost vs. recency vs. use) and lets you evict the expensive, stale entries.

lean-ctx ledger status           # pressure table
lean-ctx ledger evict big.json large.log
lean-ctx ledger prune            # drop low-value entries
lean-ctx ledger reset

ctx_plan / lean-ctx plan — budget a task up front

Phi-scored planning: given a task and a token budget, it allocates the budget across the files/symbols most worth loading.

lean-ctx plan "add OAuth login" --budget=4000

MCP profile: ultra_lean | balanced | forensic.

ctx_compile / lean-ctx compile — fill the budget optimally

Knapsack + Boltzmann view-selection: compiles the actual context to send under a budget, choosing per-file views (handles, compressed, or full).

lean-ctx compile --mode=compressed --budget=6000

Together these form a pipeline: radar (measure) → plan (allocate) → compile (materialize) → control/ledger (adjust).

3. Proactive context — load before you’re asked

Tool	What it does
ctx_overview	Task-relevant project map (Journey 3)
ctx_preload	Load task-relevant files now; compact L-curve summary (~50–100 tok)
ctx_prefetch	Predictive prefetch of blast-radius files for changed files
ctx_compose	One call: keywords + ranked files + matches + top symbol inline
ctx_fill	Fill remaining budget with the most coverage-effective files
ctx_dedup	Detect (and optionally remove) duplicated content across files

ctx_preload task="refactor the auth module"
ctx_compose task="where is rate limiting enforced?"
ctx_prefetch changed_files=["src/auth.rs"] budget_tokens=3000
ctx_dedup action=analyze        # then action=apply to reclaim

ctx_compose is the highest-leverage everyday power tool: it replaces the typical search → read → outline → read chain (3–5 calls) with one rich response.

Golden output — the compact search primitive. ctx_compose builds on ctx_search, whose results are deliberately terse — a header plus one line per hit (path:line code), so a match costs a handful of tokens instead of pages of grep context:

1 matches in 805 files:
hooks/mod.rs:153 pub fn refresh_installed_hooks() {

ctx_compose then ranks the surrounding files and inlines the top symbol, so the agent gets the answer — not just the location — in the same call.

4. Advanced reads & symbols

Beyond ctx_read (Journey 2):

Tool	What it does
ctx_smart_read	Auto-pick the optimal read mode for a file
ctx_symbol	Read just one named symbol block (fn/struct/class)
ctx_outline	List all symbols of a file with signatures
ctx_retrieve	Fetch the uncompressed original from cache (CCR)
ctx_compress_memory	Compress memory/config files (CLAUDE.md, .cursorrules)
ctx_expand	Zero-loss retrieval of an archived tool output by id

ctx_expand is the escape hatch: any large tool output that was archived can be fully recovered later (retrieve, list, search_all) — nothing is ever lost, only deferred.

5. Execution, workflows & intent

Tool	What it does
ctx_execute	Sandboxed code execution (11 languages); only stdout enters context
ctx_workflow	Workflow state machine with evidence tracking
ctx_intent	Structured intent input with a routing policy
ctx_response	Compress LLM response text (strip filler, TDD)

ctx_execute language=python code="print(sum(range(100)))"
ctx_workflow action=start name=release spec=...
ctx_workflow action=transition to=verify

ctx_workflow enforces an evidence-tracked state machine (e.g. plan → implement → verify → ship), so an agent can’t claim “done” without recorded evidence.

6. Dynamic tool loading — keep the surface small

You don’t need all 68 tools loaded to use one. Lazy clients (and minimal/ standard profiles) reach deeper tools on demand:

ctx_discover_tools query="impact analysis"   # find tools by keyword
ctx_call name=ctx_impact arguments={...}      # call any tool by name
ctx_load_tools action=load category=arch      # load a category at runtime
ctx_load_tools action=list                    # what's loaded

Categories: arch, debug, memory, metrics, session. This is how you keep per-call overhead low (small visible tool list) without losing access to the full runtime.

7. Verification & proofs (CI / audit)

Tool	CLI	What it does
ctx_verify	lean-ctx verify	Verification observability + ContextProofV2
ctx_proof	lean-ctx proof	Export machine-readable ContextProofV1
ctx_feedback	—	Record LLM output tokens + latency for harness feedback
ctx_benchmark	lean-ctx benchmark	Benchmark compression modes for a file/project
ctx_analyze	—	Entropy analysis → recommends the optimal compression mode

lean-ctx benchmark run            # compare read modes on this repo
lean-ctx benchmark compare        # vs. naive baseline, write a report
lean-ctx verify --format both
lean-ctx proof export             # ContextProof artifact for audit

These exist so the savings are provable, not just claimed — useful in CI to assert a context budget, or for an audit trail (lean-ctx audit).