---
title: "Semantic Port"
description: "Continuously port upstream changes from one language to another using a ledger-driven loop"
---
A semantic port workflow tracks commits in an upstream repository, analyzes each one for relevance, and either ports the change to a different codebase or acknowledges it as not applicable — then loops back for the next commit. It's an autonomous maintenance loop, not a one-shot build task.
This pattern is useful when you maintain a downstream implementation (e.g., a Go SDK) that tracks an upstream reference (e.g., a Python SDK). Instead of manually reviewing every upstream commit, the workflow processes the backlog commit-by-commit, making intelligent port-or-skip decisions.
## The workflow
```dot title="semantic-port.fabro"
digraph SemanticPort {
graph [
goal="Port semantic changes from upstream Python repository to our Go implementation",
rankdir=LR,
default_max_retries=3,
model_stylesheet="
* { model: claude-sonnet-4-5;}
.hard { model: claude-opus-4-6; }
.analyze { model: gemini-3.1-pro-preview;}
"
]
start [shape=Mdiamond, label="Start"]
exit [shape=Msquare, label="Exit"]
// Phase 1: Find the next unprocessed commit
fetch [
label="Fetch & Identify",
prompt="Find the next unprocessed upstream commit.\n\n\
1. Run `python3 ledger/manage.py earliest` to get the oldest commit with status=new\n\
2. If found, write the commit details to .fabro/current_commit.md and respond with:\n\
{\"preferred_next_label\": \"process\"}\n\
3. If no new commits exist:\n\
a. Fetch latest from upstream: cd upstream/ && git fetch && git pull\n\
b. Find commits newer than the latest in ledger.tsv\n\
c. Add them with `python3 ledger/manage.py add `\n\
d. Try `earliest` again\n\
e. If still none, respond with: {\"preferred_next_label\": \"done\"}\n\n\
Respond with exactly one of: process or done."
]
// Phase 2: Analyze the commit and decide port vs. skip
analyze [
label="Analyze & Decide",
class="analyze",
prompt="Read .fabro/current_commit.md for the commit to process.\n\
Examine it with `git show ` in the upstream/ directory.\n\n\
Analyze the semantic changes — what functionality changed, not just syntax.\n\
Decide if this change is relevant to our Go implementation or if it is\n\
Python-specific, docs-only, or not applicable.\n\n\
Write .fabro/analysis.md with sections:\n\
- Commit summary\n\
- Semantic analysis\n\
- Decision: PORT or ACKNOWLEDGE (with reasoning)\n\
- Port plan (if porting): concrete tasks with file:line references\n\n\
If decision is ACKNOWLEDGE:\n\
1. Update ledger: `python3 ledger/manage.py update acknowledged`\n\
2. Commit: `git add ledger/ && git commit -m \"semport: acknowledge - \"`\n\
3. Respond with: {\"preferred_next_label\": \"skip\"}\n\n\
If decision is PORT:\n\
Respond with: {\"preferred_next_label\": \"port\"}"
]
// Phase 3: Refine the plan
plan [
label="Finalize Plan",
prompt="Read .fabro/analysis.md. Perform a final editorial pass.\n\
Write .fabro/plan.md ensuring each task has:\n\
- Concrete file:line references in our Go code\n\
- Clear acceptance criteria\n\
- Directly executable instructions\n\n\
Remove vague language. The plan must be actionable."
]
// Phase 4: Implement the port
implement [
label="Implement Port",
class="hard",
prompt="Follow the plan in .fabro/plan.md.\n\
Port the semantic changes to the Go codebase.\n\
Focus on semantic equivalence, not literal translation.\n\
Use Go idioms and respect existing architecture.\n\
Log all changes to .fabro/implementation_log.md."
]
// Phase 5: Validate
validate [
label="Validate",
shape=parallelogram,
script="cd go-sdk && go build ./... && go test ./... -v 2>&1 || true"
]
gate [shape=diamond, label="Tests pass?"]
// Phase 6: Fix failures
fix [
label="Analyze & Fix",
class="hard",
max_visits=3,
prompt="Tests or build failed. Read the test output from the prior stage.\n\
Read .fabro/plan.md and .fabro/implementation_log.md.\n\
Diagnose the root cause, fix the issue, and log the fix."
]
// Phase 7: Update ledger and commit
finalize [
label="Finalize",
prompt="All tests pass. Finalize this port:\n\
1. Update ledger: `python3 ledger/manage.py update implemented`\n\
2. Commit all changes:\n\
`git add -A && git commit -m \"semport: implement - \"`\n\
3. Write a brief summary to .fabro/implementation_summary.md"
]
// Wiring
start -> fetch
fetch -> analyze [label="Process", condition="preferred_label=process"]
fetch -> exit [label="Done"]
analyze -> plan [label="Port", condition="preferred_label=port"]
analyze -> fetch [label="Skip"]
plan -> implement -> validate -> gate
gate -> finalize [label="Pass", condition="outcome=succeeded"]
gate -> fix [label="Fail"]
fix -> validate
finalize -> fetch
}
```
## Key patterns
### The commit-processing loop
The core of this workflow is a loop: `fetch → analyze → (port or skip) → fetch`. Each iteration processes exactly one upstream commit, then loops back for the next. The loop terminates when `fetch` finds no more unprocessed commits and routes to `exit`.
```
fetch → analyze → [Skip] → fetch → analyze → [Port] → plan → implement →
validate → gate → [Pass] → finalize → fetch → ... → [Done] → exit
```
This is fundamentally different from a build workflow that runs once and exits. The semantic port workflow is designed to process an entire backlog autonomously, handling dozens of commits in a single run.
### Ledger-driven state
The workflow tracks disposition in an external ledger file (`ledger.tsv`) with three states:
| Status | Meaning |
|---|---|
| `new` | Unprocessed — the workflow hasn't looked at this commit yet |
| `acknowledged` | Reviewed and determined to be irrelevant (docs-only, Python-specific, etc.) |
| `implemented` | Semantic changes ported to the Go codebase |
The ledger is the source of truth for what's been processed. Because it's a plain file committed to Git, it survives across runs — you can stop and resume the workflow and it picks up where it left off.
### Semantic analysis, not literal translation
The `analyze` node is the decision point. It examines each upstream commit for *what changed functionally*, not just what code was modified. A commit that refactors Python type hints has no semantic impact on a Go port. A commit that changes retry behavior in the HTTP client does.
This distinction is critical — routing a different model (Gemini) to the analysis node via the `.analyze` class brings a fresh perspective to the port/skip decision:
```
.analyze { model: gemini-3.1-pro-preview;}
```
### The fix loop
When ported code fails tests, the workflow enters a bounded fix loop:
```dot
gate -> fix [label="Fail"]
fix -> validate
```
The `fix` node has `max_visits=3`, preventing infinite retry cycles. If the fix can't be resolved in 3 attempts, the run terminates rather than looping forever.
### Skip vs. port branching
The `analyze` node uses [routing directives](/workflows/transitions#agent-transitions) to choose between two paths:
```dot
analyze -> plan [label="Port", condition="preferred_label=port"]
analyze -> fetch [label="Skip", condition="preferred_label=skip"]
```
When the agent decides a commit is irrelevant, it updates the ledger, commits the acknowledgment, and loops back to `fetch` immediately — no planning or implementation needed. This keeps the workflow efficient: trivial commits (typo fixes, CI config changes, docs updates) are processed in seconds.
## Multi-model routing
The stylesheet assigns three tiers of models:
```
* { model: claude-sonnet-4-5; } // Default: plan, finalize
.hard { model: claude-opus-4-6; } // Implementation, fixing
.analyze { model: gemini-3.1-pro-preview; } // Analysis: fresh eyes
```
- **Sonnet** handles routine tasks: fetching commits, finalizing plans, updating the ledger
- **Opus** handles the hard work: implementing ports and diagnosing test failures
- **Gemini Pro** handles analysis: a different provider brings independent judgment to the port/skip decision, reducing the risk of a single model's blind spots
## Run configuration
Pair the workflow with a run config TOML for repeatable execution:
```toml title="run.toml"
version = 1
goal = "Port semantic changes from upstream openai-agents-python to our Go SDK"
graph = "semport.fabro"
[llm]
model = "claude-sonnet-4-5"
provider = "anthropic"
[llm.fallbacks]
anthropic = ["openai"]
gemini = ["anthropic"]
[setup]
commands = [
"git clone https://github.com/openai/openai-agents-python upstream || (cd upstream && git pull)",
"pip install -r ledger/requirements.txt"
]
[vars]
upstream_repo = "openai/openai-agents-python"
downstream_lang = "go"
```
Launch with:
```bash
fabro run semport.toml
```
## Adapting this pattern
The semantic port pattern generalizes beyond language porting:
- **Spec tracking** — monitor an upstream specification (OpenAPI, protobuf) and propagate changes to client libraries
- **Dependency updates** — process a queue of dependency version bumps, testing and committing each one
- **Issue triage** — pull issues from a tracker, classify them, and route to the appropriate workflow
- **Log analysis** — process a backlog of alerts or log entries, investigating each one
The core structure is always the same: fetch the next item, analyze it, decide on an action, execute, record the disposition, loop.
## Further reading
Edge conditions, routing directives, and how agents control flow.
CSS-like rules for assigning models to workflow nodes.
Retry policies, loop detection, and max_visits.
TOML configs for repeatable, parameterized runs.