0.4.4

Aegon

Observability for Claude Code agentic runs.

Watches the JSONL session files Claude Code writes during a run, parses them into typed Rust structs, tracks live session state, and displays everything in a split terminal UI — a raw event feed on the left and an aggregated dashboard on the right.

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Demo

https://github.com/user-attachments/assets/a34fd65b-3872-40b2-a0a4-ef012dcf0c0a

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What it looks like

┌─ Aegon   1 session   247 events ──────────────────────────────────────────────────────────┐
│                                                                                             │
│  Events (newest first)          │  Session                                                 │
│  ─────────────────────          │  Live session  ● LIVE   247 events                      │
│  14:22:01 TOOL▶ Bash cargo…     │  ─────────────────────────────────────────────────────  │
│  14:22:00 THINK I should…       │  Tokens  ████████████░░░░░░░░░░  42k / 200k             │
│  14:21:59 ASST  Let me run…     │  in=38420  out=3801  cache_r=71204                      │
│  14:21:55 TOOL◀ Finished `d…    │  est. cost: $0.0321                                     │
│  14:21:54 TOOL▶ Read src/…      │  ─────────────────────────────────────────────────────  │
│  14:21:54 TOOL▶ Bash ls -la…    │  Steps                                                  │
│  14:21:53 ASST  I'll check…     │  ⠋ Bash          [1.2s]                                 │
│  14:21:52 USER  lets start…     │  ✓ Read          312ms                                  │
│                                 │  ✓ Write         89ms                                   │
│                                 │  ─────────────────────────────────────────────────────  │
│                                 │  Flow                                                    │
│                                 │  USER → THINK → [Bash ‖ Read] → ASST → Write → ASST    │
│ q quit                          │                                                          │
└─────────────────────────────────────────────────────────────────────────────────────────────┘

Left panel — raw event feed: every tool call, result, thinking block, and assistant message in arrival order, coloured by type, newest first.

Right panel — live dashboard:

• Session header: title, live/idle status, event count
• Token gauge: progress bar auto-filling as the context window fills; estimated cost
• Steps: spinner on active tool calls, ✓/✗ for completed/failed, with timing
• Flow: one-line causal chain showing order, parallel branches ([Bash ‖ Read]), and human turns

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Architecture

~/.claude/projects/**/*.jsonl
         │
         │  notify (OS file events: FSEvents / inotify)
         ▼
  aegon-cli / watcher.rs
  ┌─ background thread ──────────────────────────────────┐
  │  seek to last-read byte → read new lines              │
  │  ClaudeAdapter::parse_line() → Vec<LogEvent>          │
  │  tx.send(event)                                       │
  └──────────────────────────────────────────────────────┘
         │  mpsc channel
         ▼
  aegon-cli / main.rs  (main thread)
  App::push(event)
    ├─► events: Vec<LogEvent>        raw feed buffer (500 events)
    └─► SessionRegistry::ingest()
          └─► SessionState::ingest()
                ├─ pending: HashMap<id, Step>   running tool calls
                ├─ steps: Vec<Step>             completed with timing
                ├─ flow: Vec<FlowNode>          causal chain
                └─ token_totals: TokenTotals    cumulative usage

  aegon-ui / tui.rs  draws every 50ms:
    left  → raw event list
    right → dashboard::draw(SessionState)
              ├─ gauge::draw()   token progress bar + cost
              ├─ steps::draw()   spinners + completed steps
              └─ flow::draw()    USER → THINK → [T1 ‖ T2] → ASST

Crate map

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Install

Via pip (no Rust toolchain needed):

pip install aegon-rs

Via Cargo (Rust toolchain required):

cargo install aegon-cli

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Running

aegon run              # TUI in the current terminal
aegon run --detached   # open TUI in a new terminal window
aegon                  # same as aegon run

Press q or Esc to quit.

The watcher automatically picks up ~/.claude/projects/**/*.jsonl and ~/.claude/sessions/**/*.jsonl. Start a Claude Code session in another terminal — events appear in real time.

From source (contributors):

just run          # build + launch in one step
just demo         # opens in a new Terminal window
just setup        # first-time: installs system deps and Cargo tools

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Development

just --list          # all available recipes
just ci              # mirrors what CI runs (fmt + clippy + check + test + docs)
just build           # cargo build --workspace
just test            # cargo test --workspace
just audit-jsonl     # scan ~/.claude/projects for JSONL structure insights
just demo            # run the tool in a separate terminal for live demo

See CLAUDE.md for full design constraints, crate responsibilities, and the development workflow.

See CHANGELOG.md for release history and JOURNAL.md for design decisions and session notes.

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Contributing

Workflow

All changes go through a branch → PR → squash-merge cycle. The full loop is documented in CLAUDE.md and enforced by skills in .claude/skills/. In short:

just branch feat/<name>     # cut a branch from latest main
# ... make changes ...
just ci                     # must pass locally before pushing
just push                   # push and set upstream
just pr                     # open PR (gh will prompt for title + body)
just merge                  # squash-merge once CI is green
just cleanup feat/<name>    # delete local branch + prune remote refs

Rules

• Never commit to main directly. Every change goes through a PR.
• just ci must pass before pushing. It runs fmt, clippy -D warnings, check, test, and cargo doc -D warnings — exactly what CI runs.
• Every public item needs a doc comment. cargo doc -D warnings is an error, not a warning.
• CHANGELOG.md and JOURNAL.md must be updated on every PR that changes behaviour. [Unreleased] in CHANGELOG for unreleased changes; add a dated JOURNAL entry with achievements, caveats, and next steps.
• No unwrap() or expect() in library crates outside tests.
• Adapters must not use #[serde(deny_unknown_fields)] on top-level event types — the Claude JSONL format evolves without notice.

Adding a new tool adapter

1. Create crates/aegon-adapters/src/<tool>/mod.rs and raw.rs
2. Implement the Adapter trait from crates/aegon-adapters/src/lib.rs
3. Add fixture JSONL samples to aegon-tests/fixtures/<tool>/
4. Wire into aegon-cli via config or format detection

Codeowners

@chinmaypandya is the default owner for all files. All PRs require approval before merge.