SuperBased Observer

The exact tokens your AI provider billed you — cache splits, reasoning tokens, long-context surcharges — reconciled across 26 coding tools, entirely on your own machine. Nothing you build here ever leaves your machine unless you opt a node into it.

npm License: Apache 2.0 Platforms: Linux • macOS • Windows Go 1.22+


Table of contents


What it is in 30 seconds

A single local Go binary built on three things a hosted usage console can't give you, in order of how much they matter:

  1. Proxy-accurate, cross-vendor cost attribution. An optional API reverse proxy reads the token counts your provider actually billed — net input, 5m/1h cache read/write splits, reasoning tokens, long-context repricing — the same math your invoice uses, not a JSONL-derived estimate. It's accurate enough that it caught its own bug: a Codex reasoning-token double-billing regression Observer found and back-corrected months of history for (migration 058, shipped v1.18.0) — the kind of self-audit a vendor console has no incentive to run against itself.
  2. Local-first, by construction. The watcher, proxy, dashboard, MCP server, and CLI make zero outbound calls on your behalf — no telemetry, no analytics, no remote reporting. An optional team rollup server ships only hashed metadata by default; raw content ships only when the node opts in, never a remote admin toggle. Full details: PRIVACY.md.
  3. One capture layer, every tool you actually use. 26 adapters — Claude Code, Codex, Cursor, Cline + Cline CLI, GitHub Copilot + Copilot CLI, Gemini CLI, OpenCode, Google Antigravity, Cowork, Hermes Agent, Kilo Code, Aider, Goose, Devin, Qoder, Crush, Grok, Kiro CLI, Kimi Code, Qwen Code, OpenClaw, Pi, and more — parsed into one normalized schema, queryable from a local dashboard, an MCP server (so the tools themselves can query it), and a CLI. (Five of the 26 are *-web adapters for ChatGPT/Claude.ai/Gemini/ Copilot/Perplexity in the browser — those need the browser-capture extension, which today only installs unpacked; every tool listed above works out of the box.)

Raw token counting across tools is table stakes here — it's the substrate the accurate-cost layer above is built on, not the pitch.

Two planes, one binary. Plane B is coding-agent observability — desktop-first: capture, proxy-accurate cost, compression, cache tracking, and session handoff for every AI coding tool on your machine, with an optional team rollup server for org-wide spend. Plane A is general LLM-app observability — admin-server-first: OTLP trace/span capture, evals, and an LLM-as-judge input-admission guardrail for an application you host, whose end users route through Observer. Most solo developers only ever touch Plane B; teams add Plane A when they're also running an LLM-powered product. Full explainer: superbased.app/docs/getting-started/two-planes (or docs/deployment-models.md if you're reading this in the repo).

It answers questions like:

  • Where did this week's $147 Claude bill come from — which projects, models, sessions, tool calls? And is that number the same one my provider's invoice would show?
  • Did I spend more on Opus or Sonnet? Are my Sonnet sessions hitting the long-context tier and getting repriced at 2×?
  • How much did I waste re-reading files that hadn't changed since the last read in the same session?
  • Could that trivial Opus session have been done by Sonnet for 1/5 the cost?
  • Across Claude Code, Cursor, and Codex working in the same repo, what files are touched by all three? Where are they stepping on each other?
  • What will my next message roughly cost — and how much of my 5-hour and weekly subscription limit is left before I hit it?
  • Where did my own OpenTelemetry-instrumented agent spend its tokens — with the proxy's exact per-span cost where it routed through the proxy?

Install

Pick whichever package manager fits your environment — npm and PyPI ship the same prebuilt binary from the same v* tag, version numbers kept in lock-step.

Via VS Code (Marketplace or Open VSX)

code --install-extension superbased.superbased-observer

The VS Code extension bundles the observer binary, lifts the dashboard / sidebar / status bar / file decorations into the editor, and contributes a terminal profile that pre-exports the proxy env vars so AI CLIs launched from it route through observer automatically. Cursor, VSCodium, and Windsurf install the same VSIX via Open VSX.

After install, VS Code's Get Started page surfaces an in-editor walkthrough; the long-form user guide lives at docs/vscode-extension-user-guide.md and the command + settings reference is at docs/vscode-extension.md.

Via npm (recommended for Node users)

npm install -g @superbased/observer
observer --version

Via pip / uv / pipx (recommended for Python users)

pip install superbased-observer            # plain pip
uv tool install superbased-observer        # uv (isolated env, fastest)
pipx install superbased-observer           # pipx (isolated env)
observer --version

Wheels ship for manylinux2014_{x86_64,aarch64}, macosx_*_{x86_64,arm64}, and win_amd64. uv tool and pipx keep the install isolated from your project's Python env — generally what you want for a CLI tool.

Via go install (latest main, builds locally)

go install github.com/marmutapp/superbased-observer/cmd/observer@latest
observer --version

Via direct download (pre-built per-platform archive)

Each tagged release attaches per-platform archives to the Releases page, verifiable against the published SHA256SUMS:

Asset Platform Contents
observer-vX.Y.Z-linux-x64.tar.gz Linux x86_64 observer + antigravity-bridge.exe (for WSL2)
observer-vX.Y.Z-linux-arm64.tar.gz Linux arm64 observer + antigravity-bridge.exe (for WSL2)
observer-vX.Y.Z-darwin-x64.tar.gz macOS Intel observer
observer-vX.Y.Z-darwin-arm64.tar.gz macOS Apple Silicon observer
observer-vX.Y.Z-win32-x64.zip Windows x86_64 observer.exe
SHA256SUMS sha256 of all five archives
# Linux x64 example — substitute your platform + version.
VERSION=v1.6.21
PLAT=linux-x64
curl -L -O https://github.com/superbasedapp/observer/releases/download/$VERSION/observer-$VERSION-$PLAT.tar.gz
curl -L -O https://github.com/superbasedapp/observer/releases/download/$VERSION/SHA256SUMS
shasum -a 256 -c SHA256SUMS --ignore-missing
tar -xzf observer-$VERSION-$PLAT.tar.gz
./observer --version

The binary is pure Go — no CGO, no external runtime dependencies. SQLite storage is pure-Go via modernc.org/sqlite. Single static binary; scp it anywhere it runs. Same artifacts ship to npm and to the Releases page (build-once-ship-everywhere CI), so the npm and direct-download paths produce byte-identical binaries.


First-run walkthrough

# 1. Start everything: proxy + watcher + dashboard in one foreground
#    process (ctrl-c to stop). Hooks auto-register for every detected
#    AI tool, and the dashboard opens in your browser
#    (http://localhost:8081; suppress with --no-open).
observer start

# 2. (another shell) Backfill from existing session logs so the
#    dashboard has history immediately rather than starting empty.
observer scan

From here the dashboard drives. On an empty database the Overview tab leads with a three-step onboarding checklist — and a demo mode offer if you'd rather look around first: one click seeds a temporary synthetic dataset so every chart renders with realistic data (your real observer.db is never read or written; a persistent banner marks demo state and one click clears it). The two checklist steps that matter:

  1. Route your AI tool through the proxy — accurate token counts and conversation compression both need it. On the Compression tab's Proxy banner, click your tool's status pill, then Route through the observer proxy…: the button previews the exact file change (Claude Code: an env.ANTHROPIC_BASE_URL entry in ~/.claude/settings.json; Codex: an observer model provider in ~/.codex/config.toml) and writes only on confirm. Durable — every later session routes automatically. The same section of the Settings → Connected tools panel offers a per-tool setup wizard (hooks / MCP / routing, one consent click per write) and a Launch button. Prefer the terminal? The same routing ships as observer init, as session-scoped wrappers (observer claude / observer codex — no config writes), or as a plain export ANTHROPIC_BASE_URL=http://localhost:8820 / OPENAI_BASE_URL=http://localhost:8820/v1.
  2. Use your AI tool as normal. The checklist tracks the first captured session; cost, compression, and cache numbers populate within minutes of real activity.

Optional — MCP registration. observer init additionally writes MCP server entries (and hook entries) into each AI tool's own config files (~/.claude/settings.json, ~/.claude.json, ~/.cursor/mcp.json, ~/.codex/config.toml, …). Hooks default ON, MCP defaults ON; opt out per-side with --skip-hooks / --skip-mcp. Idempotent. observer start alone never registers the MCP server — MCP wiring is explicit-only, because it costs ~1,800 schema tokens per AI-client turn.

If you route Claude Code while MCP servers are registered, set ENABLE_TOOL_SEARCH=true in the same environment. Claude Code's SDK disables ToolSearch:optimistic deferred MCP loading whenever ANTHROPIC_BASE_URL is set, eagerly inlining all 17 observer MCP tool schemas (plus any Google MCPs) into every request prefix — ~+21K tokens/turn. The override re-enables lazy loading; observer's proxy forwards tool_reference blocks byte-identically, satisfying the SDK's documented safety condition. Empirical: with the override + v1.7.23 defaults, the proxy is −6.9% mean cost vs no-proxy on Claude Code's reference rig (n=8 lumen refactor task, V7-22 binary). Without it, ~+9% per-turn overhead. See superbased.app/docs/connect/claude-code for the full picture.

The proxy logs every turn with the exact token counts the provider returned, including cache-tier breakdowns (5m vs 1h ephemeral) and 1h surcharges that JSONL adapters can't always disambiguate.

Verifying the install

observer doctor          # health checks: DB integrity, hook
                         # registration, MCP entries, pid bridge
observer status          # row counts + recent activity
observer tail            # live-stream captured actions

Dashboard tour

observer start opens the dashboard automatically on interactive launches (suppress with --no-open; default URL http://localhost:8081). Twenty-one tabs in four nav groups (Monitor / Analyze / Optimize / Configure), each designed around one question — the tour below covers the core surfaces; Live (recent sessions with a real-time action feed), Search (full-text over captured tool outputs), Privacy (capture map + scrub tester), and the opt-in Terminals / Remote pages (covered under Remote & mobile access below) are self-explanatory once you're in, and the Suggestions tab's advisor nudges and the Patterns tab's derived habits are covered in their own docs. Evaluating without data? Start demo mode from the empty Overview — synthetic dataset in a temp DB, real observer.db untouched, one click to clear.

Overview — what's been happening?

Four headline KPI tiles (sessions, API turns, token rows, stale re-reads — each filterable by the global Window / Tool / Project chips), cost-over-time stacked area split by billable token bucket, actions-over-time stacked by tool, top models by token volume, top tools by action count.

Sessions — what did each run actually do?

One row per session with cost, token totals (input / cache R / cache W / output), elapsed time, action count, and a model badge. Quality / Errors / Redundancy scoring columns light up once observer score has run. Click a row to open the per-session slide-over (shown below in Session detail).

Actions — the firehose, filtered

Every recorded tool call, normalized across adapters. Filter by action type (28 categories), tool, effort, permission. Each row exposes its target + status + raw-tool source + truncated content preview; click to expand to the full event with error context.

Cost — per-model breakdown with the right math

Eight KPI tiles across the billable token buckets (Net Input, Cache Read, Cache Write 5m, Cache Write 1h, Output, Reasoning, plus total USD and turn count). Per-model table shows the full breakdown including reasoning tokens (billed at output rate) and long-context surcharges (Sonnet 1M, gpt-5 >272K, Gemini 2.5 Pro >200K). Hover any column header for its definition + formula.

Analysis — spending insights & efficiency signals

Twelve KPI tiles comparing this period to prior: spend Δ%, MTD vs budget with projection bar, $/M output rate, cache savings + cache efficacy %, high-context turn count, $/turn, burn rate ($/active hour), top model concentration %, Discovery waste $, sessions total. Daily-spend stacked bars with Model / Project / Tool dimension toggle, hour-of-day heatmap, period-over-period movers (top increases / decreases / new entrants), and model right-sizing hints (trivial Opus sessions that could have used Sonnet).

Tools — per-AI-client breakdown

Four KPIs (total actions, distinct tools, overall success rate, busiest tool), activity-over-time stacked area, and per-tool action-type-mix horizontal bars (100% normalized, colored by action category). Surfaces which AI client owned which kind of work.

Compression — what the proxy saved

Five KPIs: total $ saved (priced at your input rate), tokens saved, bytes trimmed, turns compressed. Savings-per-day stacked bar by mechanism (drop, trim, summary), savings-by-mechanism donut, recent events table with original→compressed→saved + dollar impact per event.

Cache — prompt-cache observation & forecasting

Headline cache-ratio hero (cache_read ÷ cache_write tokens) and three sibling KPIs: Cache read, Cache write, and Avoidable spend / Event count. Avoidable spend renders in warn tone — it's the dollar overhead of rewrites that wouldn't have happened on a perfectly cache-friendly session. By-model and By-project tables with R%/W% mix bars + absolute Read/Write/Events + cache Ratio + Avoidable $. Proportional Top causes histogram (suffix_growth + hit dominate a healthy session; real invalidations render in warn tone; tools_changed on MCP toggles renders neutral). Worst sessions table sorted by rewrite count; click-through opens the per-turn Cache panel.

How it's captured. Two paths feed the same engine, both writing to NODE-LOCAL cache_segments / cache_entries / cache_events tables (migrations 036+037, never pushed to a Teams org server):

  • Tier-1 (proxy) — point your AI client at 127.0.0.1:8820 and the cachetrack engine reads each turn's cache_read_input_tokens + cache_creation_input_tokens envelope live. Default capture path for Claude Code.
  • Tier-2 (transcript watcher) — feeds the same engine from on-disk claude-code JSONL transcripts for sessions that didn't route through the proxy. Run observer backfill --cache-rescan to retrofit history.

Enable / disable. Default-on per spec §11 (the loader merges [cachetrack].enabled = true if the section is absent). To turn off: [cachetrack].enabled = false in ~/.observer/config.toml, then restart observer start. Inspect engine health with observer cache-health --json. Operator reference: superbased.app/docs/guides/cache-tracking (or docs/cache-tracking.md in the repo).

Suggestions — the advisor's quantified nudges

Default-on, fully local suggestions engine (zero LLM cost, zero network): 19 detectors turn the window's captured activity into ranked, dollar- or minute-quantified recommendations — session balloons, idle re-cache, long-context tier crossings, trivial sessions on expensive models, cache hit-rate / cache-write waste / prefix thrash, read-heavy expensive-model sessions, effort overprovisioning, fast-tier premium, unrecovered failures, quality regressions, MCP schema overhead, compression off, capture without proxy routing, cross-session stale reads, web-search spend, spend spikes, plus a posture nudge (guard observing idle, pointing at the surface that owns the workflow). Every card carries its arithmetic ("show math"), a confidence score, snooze/dismiss with a 7-day cooldown, and — where a dashboard control can fix the finding — a one-click action that navigates to the right surface (writes stay behind that surface's own consent flow). CLI twin: observer advise. Config: Settings → Advisor ([advisor] — evidence window, confidence/savings floors, opt-in ≤400-token session-start digest).

Discovery — the waste detector

Waste $ hero (stale-read tokens × your blended input rate). Four KPIs: stale re-reads count, tokens wasted, affected files, repeated commands. Top files re-read table with cross-thread highlighting (when the same file was re-read from a subagent that didn't see the parent's read). Repeated-commands table with no-change-rerun detection.

Security — the guard, operable end to end

Posture tiles + a filterable verdict timeline (rule IDs resolve to their full definitions), then the routine workflows: a consent-gated mode control that shows the simulate evidence before you flip enforce, the enforce-readiness replay over your real history, the approvals register (scoped, expiring — live immediately), a lint-gated user-policy editor with .bak undo, budget guardrails suggested from your own observed spend with a daily burn-down meter, MCP pin approvals, and one-click compliance evidence downloads.

Settings — every config knob, editable

Schema-driven forms for every config section — Watcher, Freshness, Retention, Hooks, Proxy, Compression, Intelligence, Advisor, Cache tracking, Secrets scrubbing, MCP, Profiles, Org share, OTel — with honest reload semantics per section: pricing and profile changes apply hot, MCP applies to the next AI session, restart-gated sections raise a persistent restart-pending banner that names the exact command and clears only when the daemon actually restarts. Alongside the forms: a Connected tools panel (per-tool status matrix, consent-gated setup wizard, Launch button), a Health panel (the observer doctor checks + recent failures), the Backfill panel (every mode click-to-run with streamed output + full rescan), a Storage panel (per-table DB size breakdown with index/FTS bytes folded in, vacuum + online backup as click-to-run jobs, documented manual restore — CLI twin observer db stats|vacuum|backup), and a config-file card with one-click .bak restore. 182 baked-in default models; pricing "Override" prompts auto-fill from the default.

Live — what's running right now

Every session with activity in the last 15 minutes, refreshing on a 5-second tick: lifetime cost, tokens, turns, and a streaming action feed per session. The fastest way to confirm the proxy is capturing while you work.

Trajectories & Evals — observe an LLM app you host

General observability — Plane A. Distinct from the coding-agent usage above: this observes an LLM application you run at the admin level, whose end-users route through Observer.

Point any OpenTelemetry-instrumented app or agent at the local OTLP endpoint (or route it through the proxy) and its trace/span graph is captured into node-local obs_* tables — enriched with the proxy's exact cost and cache numbers wherever a span matches a proxied turn (the join no external observability tool can make). You view trajectories and eval-run health on the admin dashboard (web2, the Trajectories nav group) — the node/developer dashboard stays focused on your own coding-agent activity. Capture is local and node-opt-in, and the same plane adds per-end-user budgets + an input-admission guardrail judged by a local, custom-remote, or gateway LLM (see superbased.app/docs/getting-started/two-planes for the Plane A guardrail model).

Session detail — drill into one session

Click any session row → slide-over with an action-type breakdown donut, a token-bucket bar (net input / cache R / cache W / output), and the models used. It also carries the next-message cost predictor (a low / typical / high band over the session's likely turn fan-out) and, for proxied subscription sessions, the 5-hour / weekly limit gauge read from the provider's own rate-limit headers.

Scroll down for the full per-message timeline — every upstream API turn with its model, token buckets, per-turn cost, and the tool calls nested inside it, each row expandable. The same panel surfaces from Actions when you click a session pill.

Remote & mobile access

The dashboard reads fine from a phone (the layout adapts to small screens), and you can drive a node from another device over your tailnet — nothing is exposed to the public internet. Pair a second device from the Remote tab, then view sessions, cost, and the live feed from anywhere on your tailnet. Bind the dashboard to a tailnet interface with [dashboard].addr (or the OBSERVER_DASHBOARD_ADDR env override) instead of the default loopback.

Optionally, the Terminals tab + launch dock let you launch AI tools and run terminal commands from the dashboard — but remote execute is gated behind an explicit standing grant ([remote].allow_standing_terminal_control, default off), with per-session terminal leases and a full audit trail. Viewing is always read-only until you turn execute on. Full setup: docs/remote-access.md.


MCP server — 25 cross-tool intelligence calls

Opt-in. The MCP server is not active until you run observer init (or observer init --claude-code / --cursor / --codex). That command writes entries pointing at the observer binary into each AI tool's own MCP config file (~/.claude.json, ~/.cursor/mcp.json, ~/.codex/config.toml). The MCP server then runs as a stdio subprocess spawned by your AI tool — its lifecycle matches the AI tool's, and it never opens a network port. observer start alone does NOT register or launch the MCP server; it can be skipped entirely via observer init --skip-mcp if you want hooks-only capture.

Once registered, every connected AI tool can query the observer over MCP/stdio: 21 tools are always registered, and 4 more register conditionally (only when the capability they depend on — the proxy stash, or the codeintel index — is actually configured):

MCP tool What it answers
check_file_freshness Has this file changed since I last read it?
check_command_freshness Did this exact command already run? With what result?
get_file_history Every read/edit of this file across every tool + session (with codeintel enrichment when available).
get_session_summary What did session X actually do? AI-generated 2–4 sentence summaries.
get_session_recovery_context For resuming an interrupted session.
get_project_patterns Derived behaviours: hot files, co-changes, edit→test pairs.
get_last_test_result Without re-running.
get_failure_context Error correlation + retry detection.
get_action_details The raw row, scrubbed of secrets.
get_cost_summary Per-window spend rollup.
get_redundancy_report What would Discovery flag for this project?
search_symbols Fuzzy symbol search across the project's codeintel index (Tier-C).
list_actions_around Chronological ±N actions around an action_id.
search_past_outputs Full-text search of past tool-call outputs (FTS5 over excerpts).
get_output_composition Code vs. explanation split of a session's output, by bytes, with the code:explanation ratio and languages used.
get_suggestions Top dollar/time-quantified cost & quality suggestions from the local advisor.
cache_status Live prompt-cache health: which caches are warm, expiring, or cold, with value-at-risk.
get_model_recommendation Evidence-backed model suggestion per turn-kind, from the local Model Value Report.
get_routing_status Model-routing layer state: phase, available policy templates, tier-table size, decision-log counters.
continue_session A distilled, scrubbed handover of a session from another AI tool, so you can continue its work here.
get_session_message One full, un-excerpted message from a session's transcript — pulls the complete body a handover excerpt truncated.
get_file (conditional) The file's current bytes (or at a given commit), with path-safety gate + audit.
get_symbols (conditional) Resolve symbol name + range to file path + body (codeintel-backed).
get_relations (conditional) Codeintel BFS — who calls / is called by this symbol.
retrieve_stashed (conditional) Pulls original bytes of a tool_result the proxy stashed (only registered when CCR is enabled).

Operator note for Claude Code via observer's proxy. When you set ANTHROPIC_BASE_URL=http://localhost:8820, Claude Code's SDK disables ToolSearch:optimistic deferred MCP loading — observer's tool schemas (plus any Google MCPs you've registered) end up eagerly inlined into every request prefix, ~+21K tokens/turn. Set ENABLE_TOOL_SEARCH=true in the same shell to recover lazy loading; observer's proxy forwards tool_reference blocks byte-identically, satisfying the SDK's documented safety condition for the override. See superbased.app/docs/connect/claude-code for the full picture.

Knowledge captured from one tool benefits all the others working on the same project — data is organized by git root, not by tool. A read by Claude Code becomes a freshness signal for Codex; a Cursor compaction is visible from Cline.


API proxy — accurate tokens, compression, stash

The proxy is the home of three features that only exist when your AI client routes through it. None of them run on the watcher / observer start ingestion path — compression and stash live in the request path because that's the only place where bytes can be rewritten before they reach the upstream provider.

When you point your AI tool at http://localhost:8820, the proxy:

  1. Forwards your request to your chosen upstream (Anthropic or OpenAI). The destination is the same provider URL your AI client would have called directly; no data leaves your machine that wasn't already going to that provider. Your API key is yours — the proxy reads it from the inflight headers, never stores it.
  2. Records the exact token counts the provider returned (cache 5m vs 1h split, long-context tier triggers, reasoning tokens) into the api_turns table — more accurate than parsing the JSONL the AI tool wrote.
  3. Compresses the conversation before forwarding (importance-scored, prefix-stable for cache alignment) — the biggest lever for keeping long sessions inside rate-limit windows. Opt-in: flip [compression.conversation].enabled = true (or the Settings → Compression toggle); once enabled, tuned per-tool profiles apply automatically (see below), with the safe per-type set (compress_types = ["json","logs","code"]) on Anthropic traffic. Compressed events land in the compression_events table and surface on the Compression dashboard tab. Empirical on Claude Code lumen rig (n=8, V7-22): −6.9% mean cost vs no-proxy, CV 7.6%, zero tail outliers.
  4. Stashes large tool outputs the compressor hides, so the originals stay retrievable via the retrieve_stashed MCP tool (only registered when stash is configured). Off by default — stash markers break Anthropic's prefix cache (V7-25 n=1 measurement: +25% cost, cache_creation_input_tokens doubled). Operators who want stash on a workload should A/B before committing.

Three compression layers, each independently toggleable:

  • Shell output filters — RTK-style truncation of large bash / git / go test / docker / kubectl / cargo / pytest outputs inline before they hit the LLM context. Runs on hook / observer run paths; does not require the proxy.
  • Tool output indexing — every tool call's output indexed into FTS5; large outputs trimmed to a 2KB excerpt cap so the index stays compact and search_past_outputs stays fast. Runs on the watcher path; does not require the proxy.
  • Conversation compression — proxy rewrites large tool_result blocks before forwarding upstream. Proxy-only — there is no non-proxy path for this layer, and the stash that backs retrieve_stashed is wired here too.

Trade-off if you skip the proxy: you still get full hook + JSONL ingestion, the dashboard, MCP (if registered), and shell+indexing compression. You lose proxy-grade token accuracy, conversation compression, and the stash. For rate-limited plans (Claude Teams 5h/7d windows), conversation compression is usually the difference between "finishes the task" and "hits the limit."

Choosing a compression mode (Anthropic vs Codex)

mode is a profile parameter — each shipped profile (next section) already pins the right one, so most users never set it by hand; the matrix below is the why. It behaves differently per provider. Per-type tool_result compression runs in every mode; mode only changes how messages are dropped and whether an Anthropic cache_control marker is injected.

mode What it does Claude Code (Anthropic) Codex / OpenAI
token Per-type compress, then drop lowest-scored messages to hit target_ratio. ✅ Works. ✅ Clearest choice for Codex/OpenAI.
cache Restrict drops to the tail half + inject a cache_control marker at the prefix boundary. ✅ Anthropic-specific. ⚠️ No effect beyond token.
cache_aware (default) Skip drops, narrow compression to tool_result blocks, no marker injection; keep history byte-stable across turns so Anthropic's prefix cache keeps hitting (cache_creation falls on later turns). Recommended for Anthropic Pro/Max — and the shipped default. ⚠️ No effect beyond token, so the default is harmless for Codex.

The shipped default is cache_aware (token is just the internal fallback when mode is empty). The cache/cache_aware strategies exist for Anthropic's content-hash prefix cache (cache_control is an Anthropic Messages API concept). OpenAI/Codex prompt caching is automatic and server-side — there is nothing to mark or tune, so the proxy's OpenAI path is mode-agnostic (the default cache_aware simply behaves like token there).

Profiles — the right parameters per tool, automatically

Compression parameters ship as profiles: named parameter sets resolved per traffic class at the proxy boundary (formerly "recipes", which had to be hand-picked per daemon — and applied to all traffic, mis-tuning whichever tool the recipe wasn't written for). Enable compression once and the tuned parameters apply per tool simultaneously:

Profile Auto-assigned to Headline params Measured
claude-code Anthropic-path traffic (claude-sonnet-4-6, claude-opus-4-8, any claude-* via Claude Code) cache_aware, ratio 0.85, json+logs+code+tools, stash off (V7-25: stash breaks Anthropic's prefix cache) −6.9% mean cost vs OFF (n=8 lumen refactor, CV 7.6%, zero tail outliers; requires ENABLE_TOOL_SEARCH=true when MCP servers are registered). The A2 run (2026-06-11, n=8 Opus 4.8) added the tools-defs trim: −12.5% vs the pre-A2 set with zero tools_changed cache events.
codex-safe OpenAI-path traffic (plain GPT under the codex CLI: gpt-5.4, gpt-5.5, any non--codex) token mode, ratio 0.95, logs-only (JSON sentinel substitution corrupts codex tool data) −22% to −56% on gpt-5.4-mini (V7-21, n=10); inconclusive on an apply_patch-only workload (V7-26 — no logs-shaped output, so the proxy was a no-op; A/B your own traffic shape)
codex-variant manual — observer profile assign openai codex-variant ratio 0.99, preserve 50, no per-type compression (V7-2: -codex models re-derive when tool_results change) −10% ($0.270 vs $0.300, n=10, gpt-5.3-codex)
default escape hatch master-config [compression.conversation] params, unchanged

"variant" in codex-variant means the -codex model variant (gpt-5.3-codex, anything *-codex*), not a variant of the codex CLI — both codex profiles are for the codex CLI.

Working with profiles:

  • Inspect: observer profile list (assignments + sources), observer profile show codex-safe (the resolved TOML).
  • Reassign per traffic class or per tool: observer profile assign openai codex-variant, observer profile assign tool:cline codex-safe — or Settings → Profiles in the dashboard.
  • Custom profiles: observer profile create mine --from claude-code, then observer profile set mine compression.conversation.target_ratio 0.9 — or the Settings → Profiles editor.
  • Per-project overrides: a repo-level .observer/config.toml ([profiles] + [compression] keys only) picks different profiles or turns compression OFF for that repo's traffic — never on (untrusted-repo guard).
  • Hot for new sessions: profile edits and assignment changes apply without a daemon restart. The master enabled switch itself is restart-gated — the dashboard banner says so honestly.
  • observer start --recipe <name> survives as a deprecated alias that pins one profile for all traffic.

Measured effects vary by traffic shape and workload — from the double-digit savings above to a since-fixed configuration that once regressed cost on a different binary. Historic marketing claims of a flat savings percentage are retracted; compression ships opt-in and default-off precisely because the right call depends on your own traffic — A/B it before relying on any number here. Full knob reference (stash, rolling-summary's per-provider model split, compaction): docs/compression-modes.md. Then route your client through the proxy — the one-click button path in the First-run walkthrough — and restart it.


Architecture

┌──────────────┐     ┌──────────────┐     ┌──────────────┐
│ Claude Code  │     │    Cursor    │     │    Codex     │    ... 26 adapters total
└──────┬───────┘     └──────┬───────┘     └──────┬───────┘
       │ JSONL              │ hook events        │ rollout files
       ▼                    ▼                    ▼
┌────────────────────────────────────────────────────────┐
│              fsnotify Watcher + Adapters               │
│      (one parser per platform, normalized output)      │
└───────────────────────────┬────────────────────────────┘
                            │ ToolEvent / Action / Sessi