From c119bf3c79a074b59d0f9855b223b2b9680264cf Mon Sep 17 00:00:00 2001 From: "brynary-fabro[bot]" <265161896+brynary-fabro[bot]@users.noreply.github.com> Date: Fri, 20 Mar 2026 21:38:16 -0400 Subject: [PATCH] Use short hex IDs for subagents instead of UUIDs (#128) MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit This PR updates subagent ID generation to use short 8-character hex strings instead of full UUID v4 strings. Previously, subagent IDs were 36-character UUIDs (e.g. `550e8400-e29b-41d4-a716-446655440000`), which were verbose in CLI output and unwieldy when the LLM needed to reference them in tools like `send_input`, `wait`, and `close_agent`. The new format generates IDs like `a3f1b20c` — compact, human-readable, and with ~4 billion possible values, effectively collision-free within a session. The change is made at the source in `subagent.rs`, where UUID generation is replaced with `format!("{:08x}", uuid::Uuid::new_v4().as_fields().0)`. Because IDs are now inherently 8 characters, the display-layer truncations in `cli.rs` (5 occurrences) and `run_progress.rs` (2 occurrences) are redundant and have been removed — `agent_id` is used directly in format strings instead of a `short_id` slice. ### Plan Summary - **Replace UUID generation** in `subagent.rs`: use the first field of a UUID v4 formatted as 8-char lowercase hex, yielding IDs like `a3f1b20c` instead of full 36-char UUIDs - **Remove `short_id` truncation** in `cli.rs` (5 places) and `run_progress.rs` (2 places): since IDs are now already 8 chars, the `let short_id = &agent_id[..8.min(agent_id.len())]` pattern is eliminated and `{agent_id}` is used directly in all format strings - No test changes required — existing tests use hardcoded IDs like `"sa-1"` and don't assert on ID length or format
Full plan ````md The plan has been written to `/home/daytona/workspace/plan.md`. It covers: - **4 files to modify**: `fabro-agent/Cargo.toml` (add `rand` dep), `subagent.rs` (replace UUID with 8-char hex), `cli.rs` (remove 5 `short_id` truncations), `run_progress.rs` (remove 2 `short_id` truncations) - **Step-by-step implementation** with exact line references and before/after code - **Verification commands** to confirm correctness - **Test case analysis** explaining why no test changes are needed ````
### Fabro Details
Ran 3 stages in 18m 46s for $0.57 | Stage | Duration | Cost | Retries | |---|---|---|---| | start | 0s | – | 0 | | plan | 1m 28s | $0.57 | 0 | | implement | 17m 6s | – | 0 | | **Total** | **18m 46s** | **$0.57** | **0** |
Ran GhImplement.fabro (4 nodes and 3 edges) ```dot digraph GhImplement { graph [ goal="Implement a GitHub issue", model_stylesheet=" * { model: claude-opus-4-6; } " ] rankdir=LR start [shape=Mdiamond, label="Start"] exit [shape=Msquare, label="Exit"] plan [label="Plan", prompt="Fetch the GitHub issue from the goal using: gh issue view $goal --json title,body,labels,comments\n\nRead the issue title, description, and any comments carefully. Analyze what code changes are needed to resolve the issue.\n\nWrite a detailed implementation plan to plan.md that includes:\n- Summary of the issue\n- Files to create or modify\n- Step-by-step implementation approach\n- Test cases to add or update\n\nThe plan should be specific enough for another agent to implement without seeing the original issue.\n\nRespond with the location of the plan file (plan.md)."] implement [label="Implement", shape=house, stack.child_workflow="fabro/workflows/implement/workflow.fabro", manager.max_cycles=100] start -> plan plan -> implement [fidelity="summary:high"] implement -> exit } ```
⚒️ Generated with [Fabro](https://fabro.sh) --------- Co-authored-by: Fabro --- lib/crates/fabro-agent/src/cli.rs | 15 ++-- lib/crates/fabro-agent/src/subagent.rs | 2 +- .../fabro-cli/src/commands/run_progress.rs | 6 +- plan.md | 71 +++++++++++++++++++ 4 files changed, 79 insertions(+), 15 deletions(-) create mode 100644 plan.md diff --git a/lib/crates/fabro-agent/src/cli.rs b/lib/crates/fabro-agent/src/cli.rs index c15c48ddb..2e97d76ca 100644 --- a/lib/crates/fabro-agent/src/cli.rs +++ b/lib/crates/fabro-agent/src/cli.rs @@ -539,7 +539,6 @@ pub async fn run_with_args_and_client( task, .. } => { - let short_id = &agent_id[..8.min(agent_id.len())]; let task_preview = if task.len() > 60 { &task[..crate::truncation::floor_char_boundary(task, 60)] } else { @@ -548,7 +547,7 @@ pub async fn run_with_args_and_client( eprintln!( " {}", s.dim.apply_to(format!( - "\u{25b6} subagent {short_id} spawned (depth={depth}) task={task_preview:?}" + "\u{25b6} subagent {agent_id} spawned (depth={depth}) task={task_preview:?}" )), ); } @@ -558,11 +557,10 @@ pub async fn run_with_args_and_client( success, turns_used, } => { - let short_id = &agent_id[..8.min(agent_id.len())]; eprintln!( " {}", s.dim.apply_to(format!( - "\u{25a0} subagent {short_id} completed (depth={depth}, success={success}, turns={turns_used})" + "\u{25a0} subagent {agent_id} completed (depth={depth}, success={success}, turns={turns_used})" )), ); } @@ -571,20 +569,18 @@ pub async fn run_with_args_and_client( depth, error, } => { - let short_id = &agent_id[..8.min(agent_id.len())]; eprintln!( " {}", s.red.apply_to(format!( - "\u{2717} subagent {short_id} failed (depth={depth}): {error}" + "\u{2717} subagent {agent_id} failed (depth={depth}): {error}" )), ); } AgentEvent::SubAgentClosed { agent_id, depth } => { - let short_id = &agent_id[..8.min(agent_id.len())]; eprintln!( " {}", s.dim.apply_to(format!( - "\u{25a0} subagent {short_id} closed (depth={depth})" + "\u{25a0} subagent {agent_id} closed (depth={depth})" )), ); } @@ -593,11 +589,10 @@ pub async fn run_with_args_and_client( event: child_event, .. } if verbose => { - let short_id = &agent_id[..8.min(agent_id.len())]; eprintln!( " {}", s.dim - .apply_to(format!("[subagent {short_id}] {child_event:?}")), + .apply_to(format!("[subagent {agent_id}] {child_event:?}")), ); } _ => {} diff --git a/lib/crates/fabro-agent/src/subagent.rs b/lib/crates/fabro-agent/src/subagent.rs index b29124be4..a1bfd21a8 100644 --- a/lib/crates/fabro-agent/src/subagent.rs +++ b/lib/crates/fabro-agent/src/subagent.rs @@ -64,7 +64,7 @@ impl SubAgentManager { ))); } - let agent_id = uuid::Uuid::new_v4().to_string(); + let agent_id = format!("{:08x}", uuid::Uuid::new_v4().as_fields().0); let followup_queue = session.followup_queue_handle(); let cancel_token = session.cancel_token(); diff --git a/lib/crates/fabro-cli/src/commands/run_progress.rs b/lib/crates/fabro-cli/src/commands/run_progress.rs index 8b7a5857a..56c5ef9ef 100644 --- a/lib/crates/fabro-cli/src/commands/run_progress.rs +++ b/lib/crates/fabro-cli/src/commands/run_progress.rs @@ -1419,11 +1419,10 @@ impl ProgressUI { } AgentEvent::SubAgentSpawned { agent_id, task, .. } if self.verbose => { let dim = Style::new().dim(); - let short_id = &agent_id[..agent_id.len().min(8)]; self.insert_subagent_line_for_stage( stage_node_id, &dim.apply_to(format!( - "\u{25b8} subagent[{short_id}] \"{}\"", + "\u{25b8} subagent[{agent_id}] \"{}\"", truncate(task, 50) )) .to_string(), @@ -1435,11 +1434,10 @@ impl ProgressUI { success, .. } if self.verbose => { - let short_id = &agent_id[..agent_id.len().min(8)]; let glyph = if *success { green_check() } else { red_cross() }; self.insert_subagent_line_for_stage( stage_node_id, - &format!("{glyph} subagent[{short_id}] ({turns_used} turns)"), + &format!("{glyph} subagent[{agent_id}] ({turns_used} turns)"), ); } _ => {} diff --git a/plan.md b/plan.md new file mode 100644 index 000000000..45c8811ee --- /dev/null +++ b/plan.md @@ -0,0 +1,71 @@ +# Plan: Use short hex IDs for subagents instead of UUIDs + +## Summary + +GitHub issue #126: Subagent IDs are currently full UUID v4 strings (36 chars, e.g. `550e8400-e29b-41d4-a716-446655440000`). These are verbose in CLI output and error-prone when referenced by the LLM in tools like `send_input`, `wait`, and `close_agent`. The codebase already truncates agent IDs to 8 chars for display in multiple places. This change replaces UUID generation with a random 8-char hex string (e.g. `a3f1b20c`) so the full ID matches what's already displayed. + +## Files to modify + +### 1. `lib/crates/fabro-agent/Cargo.toml` +- Add `rand.workspace = true` to `[dependencies]`. (`rand = "0.8"` is already defined in workspace root `Cargo.toml`; other crates like `fabro-cli`, `fabro-llm`, `fabro-workflows` already use it.) +- Do **not** remove `uuid.workspace = true` — it's still used in `session.rs:58` for session IDs. + +### 2. `lib/crates/fabro-agent/src/subagent.rs` +- **Line 67**: Replace `uuid::Uuid::new_v4().to_string()` with `format!("{:08x}", rand::random::())`. +- This generates 8-char lowercase hex strings with ~4 billion possible values — collision-free within a session. + +### 3. `lib/crates/fabro-agent/src/cli.rs` +Remove the `short_id` truncation pattern in 5 places. Since IDs are now 8 chars, `short_id == agent_id`, so use `agent_id` directly: + +- **Line 542** (`SubAgentSpawned` handler): Remove `let short_id = &agent_id[..8.min(agent_id.len())];` and replace `{short_id}` with `{agent_id}` in the format string. +- **Line 561** (`SubAgentCompleted` handler): Same removal and replacement. +- **Line 574** (`SubAgentFailed` handler): Same removal and replacement. +- **Line 583** (`SubAgentClosed` handler): Same removal and replacement. +- **Line 596** (`SubAgentEvent` handler, verbose mode): Same removal and replacement. + +### 4. `lib/crates/fabro-cli/src/commands/run_progress.rs` +Remove the `short_id` truncation pattern in 2 places: + +- **Line 1416** (`SubAgentSpawned` handler): Remove `let short_id = &agent_id[..agent_id.len().min(8)];` and replace `{short_id}` with `{agent_id}` in the format string. +- **Line 1432** (`SubAgentCompleted` handler): Same removal and replacement. + +## Step-by-step implementation + +1. **Add `rand` dependency to `fabro-agent`**: + In `lib/crates/fabro-agent/Cargo.toml`, add `rand.workspace = true` to the `[dependencies]` section (e.g. after the `uuid.workspace = true` line). + +2. **Replace UUID generation in `subagent.rs`**: + In `lib/crates/fabro-agent/src/subagent.rs` line 67, change: + ```rust + let agent_id = uuid::Uuid::new_v4().to_string(); + ``` + to: + ```rust + let agent_id = format!("{:08x}", rand::random::()); + ``` + +3. **Remove `short_id` truncation in `cli.rs`**: + In `lib/crates/fabro-agent/src/cli.rs`, for each of the 5 occurrences of `let short_id = &agent_id[..8.min(agent_id.len())];` (lines 542, 561, 574, 583, 596): + - Delete the `let short_id = ...` line. + - Replace `{short_id}` with `{agent_id}` in the corresponding format string on the same match arm. + +4. **Remove `short_id` truncation in `run_progress.rs`**: + In `lib/crates/fabro-cli/src/commands/run_progress.rs`, for each of the 2 occurrences of `let short_id = &agent_id[..agent_id.len().min(8)];` (lines 1416, 1432): + - Delete the `let short_id = ...` line. + - Replace `{short_id}` with `{agent_id}` in the corresponding format string. + +## Verification + +- `cargo build --workspace` — clean build with no errors. +- `cargo test -p fabro-agent` — all existing subagent tests pass. Tests use hardcoded IDs like `"sa-1"`, not UUIDs, so no test changes needed. +- `cargo clippy --workspace -- -D warnings` — no new warnings. +- `cargo fmt --check --all` — formatting is clean. + +## Test cases + +No new test cases are needed. The existing tests in `subagent.rs` (e.g. `spawn_creates_agent_and_returns_id`) already verify that: +- `agent_id` is non-empty +- The agent can be looked up by its ID +- Spawn/wait/close/send_input work with the generated IDs + +The generated IDs will now be 8 chars instead of 36, but the tests don't assert on length or format, so they pass unchanged.