Ruby SDK - Bitfab

The Bitfab Ruby SDK captures your AI function calls to automatically generate evaluations. Re-run your prompts with different models, parameters, and inputs to iterate faster.

Framework-native adapters (LangGraph, OpenAI Agents, BAML, Claude Agent SDK) are not yet available for Ruby. See Frameworks overview for current coverage. Instrument Ruby code manually via Bitfab::Traceable or Bitfab.span.

Installation

# Bundler
bundle add bitfab

# Gem
gem install bitfab

Quick Start

require "bitfab"

Bitfab.configure(api_key: ENV.fetch("BITFAB_API_KEY"))

Need an API key? Get one from the Bitfab dashboard or see the API Keys guide for detailed setup instructions.

Coding Agent Prompt (Cursor, Claude Code)

Copy this prompt into your coding agent (tested with Cursor and Claude Code using Sonnet 4.5):

Modify existing Ruby code to add Bitfab tracing.
Do NOT browse or web search. Use ONLY the API described below.

Bitfab Ruby SDK (authoritative excerpt):
- Install: `gem install bitfab` or `bundle add bitfab`
- Init:
  require "bitfab"
  Bitfab.configure(api_key: ENV.fetch("BITFAB_API_KEY"))
- Instrumentation (ONLY allowed form):
  class MyService
    include Bitfab::Traceable
    bitfab_function "<trace_function_key>"

    bitfab_span :method_name, type: "function"
    def method_name
      # ...
    end
  end
  (bitfab_span must be placed immediately ABOVE the `def` it instruments.)
- Span types: "llm", "agent", "function", "guardrail", "handoff", "custom"
- DO NOT use a block form of bitfab_span.
- DO NOT extract helper methods.

Task:
1) Ensure the bitfab gem is added and initialization exists (Gemfile + initializer).
2) Read the codebase and identify ALL AI workflows (LLM calls, agent runs, AI-driven decisions).
3) Present me with a numbered list of workflows you found. For each, describe:
   - What it does
   - Why it's worth instrumenting: what visibility tracing gives you into each step
4) After I choose which workflow(s) to instrument:
   - Add `bitfab_span` directly ABOVE each method's `def`
   - Instrument intermediate steps (not just the final output) so each trace has enough context to diagnose issues
   - Ensure each class includes `Bitfab::Traceable` and has `bitfab_function` set
5) Do not change method signature, behavior, or return value. Minimal diff.

Output:
- First: your numbered list of workflows with why each is worth instrumenting
- After my selection: minimal diffs for Gemfile, initializer, and the method changes

Basic Configuration

Bitfab.configure(api_key: "...")

# Omit api_key entirely: the SDK reads ENV["BITFAB_API_KEY"]
Bitfab.configure

# Disable tracing (methods still execute, but no spans are sent)
Bitfab.configure(api_key: "...", enabled: false)

Missing API key doesn’t crash. If the API key is missing, empty, or whitespace-only, the SDK automatically disables tracing and logs a one-time warning at first use. All instrumented methods still execute normally: no spans are sent, no errors are thrown. You don’t need any conditional logic around the API key.

API key resolution

The key is resolved lazily, the first time a span runs, not when configure is called. Resolution order is the configured value (a Proc is called while still unresolved), then a fallback read of ENV["BITFAB_API_KEY"].

# Pass a Proc to defer resolution explicitly (resolved at first use):
Bitfab.configure(api_key: -> { ENV["BITFAB_API_KEY"] })

For standalone scripts where a run that emits no traces should be treated as a failure rather than silently skipped, set strict:

# Raises on the first traced call if no key resolves, instead of disabling quietly
Bitfab.configure(api_key: ENV["BITFAB_API_KEY"], strict: true)

Tracing

Custom (Recommended)

Using `Bitfab::Traceable` to Link Spans

Include Bitfab::Traceable in a class, declare the trace function key once with bitfab_function, then use bitfab_span to wrap methods. Three declaration styles are supported:

class OrderService
  include Bitfab::Traceable
  bitfab_function "order-processing"

  # Style 1: Before-def (recommended): declare bitfab_span above the method
  bitfab_span :process_order, type: "function"
  def process_order(order_id)
    { order_id: order_id }
  end

  # Style 2: Inline: wrap the def directly
  bitfab_span def validate_order(order_id)
    { valid: true }
  end, type: "guardrail"

  # Style 3: After-def: declare bitfab_span after the method definition
  def enrich_order(order_id)
    { enriched: true }
  end
  bitfab_span :enrich_order, type: "function"
end

All three styles are equivalent. The before-def style is recommended for readability.

Multi-File Projects

For projects with instrumented methods spread across multiple files, create an initializer that configures Bitfab, then include Bitfab::Traceable in any class that needs tracing.

# config/initializers/bitfab.rb (single source of truth)
require "bitfab"
Bitfab.configure(api_key: ENV.fetch("BITFAB_API_KEY"))

# app/services/process_order_service.rb
class ProcessOrderService
  include Bitfab::Traceable
  bitfab_function "order-processing"

  bitfab_span :process_order, type: "function"
  def process_order(order_id)
    { order_id: order_id }
  end
end

# app/services/validate_order_service.rb
class ValidateOrderService
  include Bitfab::Traceable
  bitfab_function "order-processing"

  bitfab_span :validate_order, type: "guardrail"
  def validate_order(order_id)
    { valid: true }
  end
end

Classes sharing the same bitfab_function key are grouped together. Spans from different classes are automatically linked as parent-child when one instrumented method calls another.

Using `bitfab_span` with Explicit Key

For a single span with an explicit trace function key:

class StandaloneService
  include Bitfab::Traceable

  bitfab_span :standalone_task, trace_function_key: "one-off-operation"
  def standalone_task
    "done"
  end
end

Automatic Nesting

Spans nest automatically based on call stack:

class Pipeline
  include Bitfab::Traceable
  bitfab_function "pipeline"

  bitfab_span :outer, type: "agent"
  def outer
    inner  # Becomes a child of "outer"
  end

  bitfab_span :inner, type: "function"
  def inner
    # ...
  end
end

Span Options

Parameters:

method_name (required): Symbol of the method to wrap
trace_function_key (optional): Override class-level bitfab_function
name (optional): Display name. Defaults to method name
type (optional): Span type. Defaults to "custom"

Span Types:

SPAN_TYPES = %w[
  llm        # LLM calls
  agent      # Agent workflows
  function   # Function calls
  guardrail  # Safety checks
  handoff    # Human handoffs
  custom     # Default
]

Examples:

class SafetyService
  include Bitfab::Traceable
  bitfab_function "safety-service"

  # Method name is automatically captured as span name
  bitfab_span :check_safety, type: "guardrail"
  def check_safety(content)
    { safe: !content.include?("unsafe") }
  end

  # Override with name option
  bitfab_span :validate_input, name: "InputValidator", type: "guardrail"
  def validate_input(input)
    { valid: !input.empty? }
  end
end

Span Context

Use Bitfab.current_span to get a handle to the active span, then call .add_context() to attach contextual key-value pairs from inside a traced method, useful for runtime values like request IDs, computed scores, or dynamic context:

class OrderService
  include Bitfab::Traceable
  bitfab_function "order-processing"

  bitfab_span :process_order, type: "function"
  def process_order(order_id)
    user_id = current_user_id
    Bitfab.current_span.add_context("user_id" => user_id, "order_id" => order_id)
    { order_id: order_id, status: "completed" }
  end
end

Each add_context call pushes the entire hash as one entry. Multiple calls accumulate entries:

Bitfab.current_span.add_context("user_id" => "u-123")
Bitfab.current_span.add_context("request_id" => "req-789")
# Result: contexts: [{ "user_id" => "u-123" }, { "request_id" => "req-789" }]

You can also access the current trace ID via Bitfab.current_span.trace_id (returns an empty string outside a span):

trace_id = Bitfab.current_span.trace_id

Span Prompt

Use Bitfab.current_span to set the prompt string on the current span. This is stored in span_data.prompt and is useful for capturing the exact prompt text sent to an LLM:

class ClassificationService
  include Bitfab::Traceable
  bitfab_function "classification"

  bitfab_span :classify_text, type: "llm"
  def classify_text(text)
    prompt = "Classify the following text: #{text}"
    Bitfab.current_span.set_prompt(prompt)
    llm.complete(prompt)
  end
end

The last set_prompt call wins — it overwrites any previously set prompt on the span. Calling set_prompt outside a span context is a no-op (it never crashes).

Trace Context

Use Bitfab.current_trace to set context that applies to the entire trace (all spans within a single execution). This is useful for grouping traces by session or attaching trace-level metadata:

class OrderService
  include Bitfab::Traceable
  bitfab_function "order-processing"

  bitfab_span :process_order, type: "function"
  def process_order(order_id)
    trace = Bitfab.current_trace

    # Set session ID (stored as database column, filterable in dashboard)
    trace.set_session_id("session-123")

    # Set trace metadata (stored in raw trace data)
    trace.set_metadata("region" => "us-west-2", "environment" => "production")

    # Add context entries (stored as key-value pairs, accumulates across calls)
    trace.add_context("workflow" => "checkout-flow", "batch_id" => "batch-2024-01")

    { order_id: order_id, status: "completed" }
  end
end

set_session_id(id): Groups traces by user session. Stored as a database column for efficient filtering.
set_metadata(hash): Arbitrary key-value metadata on the trace. Merges with existing metadata.
add_context(hash): Key-value context entries. Accumulates across multiple calls.

Dropping a Trace

Call .drop on the current-trace handle to discard the in-flight trace. Once flagged, spans that complete afterward are not uploaded at all, and the flag rides out on the completion payload, so when the trace completes the server scrubs any payloads that already raced out (the trace, its external trace, and sibling spans), deletes the archived S3 objects, and marks it dropped instead of completed, keeping only a skeleton audit row. Use it to discard runs you never want stored (health checks, test traffic) or a run you know carries sensitive data.

class OrderService
  include Bitfab::Traceable
  bitfab_function "order-processing"

  bitfab_span :process_order, type: "function"
  def process_order(order_id)
    Bitfab.current_trace.drop if health_check?(order_id)

    { order_id: order_id, status: "completed" }
  end
end

Safe to call outside a trace (a no-op), and never raises into your application.

Error Handling

Errors are captured in the span and re-raised:

class RiskyService
  include Bitfab::Traceable
  bitfab_function "risky-service"

  bitfab_span :risky
  def risky
    raise "error"
  end
end

begin
  RiskyService.new.risky
rescue => e
  # Span records error and timing
end

Each error is classified by source. Errors raised by your code are recorded with error_source: "code". SDK-internal errors are recorded with source: "sdk". Both appear in the span’s errors array in the Bitfab dashboard.

Flushing Traces

Bitfab.flush_traces(timeout: 30)  # Default: 30s

Traces flush automatically on process exit via at_exit hook.

Wrapping Third-Party Methods

Use Bitfab::Traceable.wrap to trace methods on external classes:

require "openai"

Bitfab::Traceable.wrap(
  OpenAI::Client, :chat,
  trace_function_key: "openai",
  name: "Chat",
  type: "llm"
)

# Now all calls to client.chat are traced
client = OpenAI::Client.new(access_token: ENV["OPENAI_API_KEY"])
client.chat(parameters: { model: "gpt-4", messages: [...] })

Replay

A trace is replayable when its root span has serializable inputs (the recorded inputs must round-trip through to_json). Framework handlers are not yet available for Ruby, so serializable root inputs are the only path to a replayable trace; instrument the outer workflow method so its inputs serialize. Replay historical traces through a method to create test runs. This re-runs past inputs through your updated code and compares the results.

client = Bitfab.client

# Pass an instance for instance methods
service = OrderService.new(api_key: "...", db: db)
result = client.replay(
  service, :process_order,
  trace_function_key: "order-processing",
  limit: 5
)

# Or pass a Class for class methods
result = client.replay(
  OrderService, :process_order,
  trace_function_key: "order-processing",
  limit: 5
)

puts "Test Run URL: #{result[:test_run_url]}"
puts "Test Run ID:  #{result[:test_run_id]}"

result[:items].each do |item|
  puts "Input: #{item[:input]}, Result: #{item[:result]}, Error: #{item[:error]}"
  puts "Duration (ms): #{item[:duration_ms]}"
  puts "Tokens: #{item[:tokens]}"    # { input:, output:, cached:, total: } or nil
  puts "Model: #{item[:model]}"
  puts "Trace ID: #{item[:trace_id]}" # Server trace ID for the replayed execution
end

Replay waits for each item’s trace (spans + completion) to be persisted server-side before completing the test run, so :trace_id is a real server trace ID for completed items. If NO completed item’s trace persisted (uploads wholesale failed, or the replayed method isn’t traced), replay raises a RuntimeError instead of silently returning nil trace IDs. If only SOME items’ traces are missing (a transient per-item upload failure), those items get nil trace IDs with a loud warning and the rest of the run is returned intact. :trace_id is also nil for errored (unreplayable) items, and for all items when the server predates the trace-ID mapping (a warning explains which). Per-item :duration_ms and :model come from the historical trace that fed the item. :tokens is the replayed run’s token usage (the same numbers Studio’s experiments view shows), so comparing each item’s :tokens[:total] against the original trace’s recorded usage tells you how your change moved cost. Each field is nil when it wasn’t captured. Parameters:

receiver (required): An instance for instance methods, or a Class for class methods
method_name (required): Symbol of the method to replay
trace_function_key (required): The trace function key
limit (optional): Max traces to replay (default: 5). Ignored when trace_ids is passed (with a warning): an explicit ID list already determines how many traces replay.
trace_ids (optional): Array of specific trace IDs to replay (max 100). The ID count determines how many traces replay; limit is ignored when both are passed.
name (optional): Display name for the resulting experiment/test run.
max_concurrency (optional): Max threads for parallel replay (default: 10)
code_change_description (optional): Rationale for the code change being tested in this replay (stored on the experiment)
code_change_files (optional): Array of edited files, each as { path:, before:, after: } (use "" for newly created or deleted files)
mock (optional): Mock strategy for child spans during replay. One of "marked" (default, only spans tagged with mock_on_replay: true return historical output), "none" (every child runs real code), or "all" (every child returns its historical output)
experiment_group_id (optional): UUID string that groups multiple replay runs into a single experiment batch. Pass the same ID across successive replay() calls to link them together in the dashboard.
adapt_inputs (optional): A callable ->(args, kwargs, ctx) that reshapes recorded inputs onto the method’s current signature when its shape changed after the traces were captured. See Adapting inputs after a signature change below.
on_progress (optional): A callable ->(progress) fired once per item as it settles, with running totals plus the settled item payload (source trace id, local replay trace id, input, result, original output, error, duration, tokens/model metadata). Use it to render live progress or start evaluating completed items while replay runs. A raising callback never crashes the run. Bitfab plugin replay scripts can pass the SDK’s ready-made reporter straight in (on_progress: Bitfab.method(:report_replay_progress)); it writes the event to stderr, which the Bitfab plugin polls to report live progress and write per-item result files while replay runs (stdout remains available for direct-run ReplayResult JSON).
environment (optional): A Bitfab::ReplayEnvironment. When passed, the Bitfab server resolves a per-trace database branch from each source trace’s captured snapshot reference, and the SDK exposes that branch’s URL via environment.database_url inside the replayed method (releasing the branch after each item). Read environment.active? to fall back to your live database when no branch was resolved (e.g. the trace predates snapshot capture, or DB branching isn’t configured). Construct one with Bitfab::ReplayEnvironment.new and read it only inside the replayed method.

Notes:

receiver + method_name must resolve to the method that carries the traceable decoration. Passing a plain wrapper around it will not resolve the trace function key.
trace_function_key must match the method’s declared key. It is read from the bitfab_span / Bitfab::Traceable.wrap declaration on the method you point at. If the key you pass contradicts that declared key, replay raises an ArgumentError: it would otherwise fetch one function’s historical traces but record the replay under the method’s own key, producing an incoherent test run. (Ruby has no plain-callable replay form, so there is no reason to pass a non-matching key.)
trace_function_key is passed explicitly, so instance methods and class methods are disambiguated by the receiver.
Use a single Bitfab::Client across instrumentation and replay. If your instrumented module constructs a client at load and your replay script constructs another, they do not share registered trace functions; import the client from the instrumented module (or a shared singleton) rather than constructing a new one in the replay script.

Replay specific traces:

service = OrderService.new(api_key: "...")
result = client.replay(
  service, :process_order,
  trace_function_key: "order-processing",
  trace_ids: ["trace-id-1", "trace-id-2"]
)

Attaching a code change: Each replay creates an experiment (test run). When you’re iterating on a method and replaying after every edit, attach the change so the dashboard can show exactly what was edited alongside the results. Read each file before editing, edit, then read it again: the two strings go straight into code_change_files. There’s no diff format to construct.

before = File.read("lib/order_service.rb")
# ...edit lib/order_service.rb...
after = File.read("lib/order_service.rb")

result = client.replay(
  service, :process_order,
  trace_function_key: "order-processing",
  code_change_description: "fix off-by-one in retry logic",
  code_change_files: [
    {path: "lib/order_service.rb", before:, after:}
  ]
)

Both options are optional and independent: pass just code_change_description for a quick rationale-only annotation, or just code_change_files to record the literal edits.

Mock child spans during replay

For the workflow-level guide, see Replay Mocking. By default replay uses "marked": child spans tagged with mock_on_replay: true return their historical outputs, while every other child runs real code. Three mock strategies control this behavior:

# "marked" (default): only spans declared with mock_on_replay: true return historical output
client.replay(service, :process_order, trace_function_key: "order-processing")

# "none": every child span runs real code
client.replay(service, :process_order, trace_function_key: "order-processing", mock: "none")

# "all": every child span returns its historical output, real code never runs
client.replay(service, :process_order, trace_function_key: "order-processing", mock: "all")

Tag the child spans you want mocked at definition time:

class OrderService
  include Bitfab::Traceable
  bitfab_function "order-processing"

  # Paid LLM call: skip during replay by default
  bitfab_span :classify_intent, type: "llm", mock_on_replay: true
  def classify_intent(prompt); end

  # Cheap, deterministic: keep running real
  bitfab_span :persist, type: "function"
  def persist(order); end

  bitfab_span :process_order, type: "agent"
  def process_order(order)
    classify_intent(order.description)
    persist(order)
  end
end

Use the default mock: "marked" behavior when you want to iterate on process_order’s logic without paying for the LLM call on each replay. Use mock: "all" when the goal is the cheapest possible replay (every child span returns its recorded output; only the root function executes real code). Repeated calls to the same trace_function_key are distinguished by call order, so step:0, step:1, step:2 correspond to the first, second, and third invocations. Unmarked spans still advance the counter, so a marked sibling that runs after an unmarked one lines up with the right historical entry.

Fluent API: `client.get_function`

Bind a trace_function_key once and wrap multiple classes or methods against it. Mirrors client.get_function in the Python SDK and client.getFunction in TypeScript.

fn = Bitfab.client.get_function("openai")

fn.wrap(OpenAI::Client, :chat, name: "Chat", type: "llm")
fn.wrap(OpenAI::Client, :embeddings, name: "Embed", type: "llm")

#wrap accepts the same options as Bitfab::Traceable.wrap (name, type, mock_on_replay), but the trace_function_key is fixed to the one bound on the returned Bitfab::BitfabFunction.

Adapting inputs after a signature change

Replay deserializes each trace’s inputs exactly as they were captured against the method’s signature at trace time, then calls the current method with them. If the signature drifted since capture (an argument renamed, reordered, folded into a hash, or a new required argument added), the call no longer lines up and raises. The adapt_inputs hook reshapes the recorded inputs onto the current signature so replay can still run:

# Recorded as positional (user_id, limit); current signature takes a hash.
adapt = ->(args, _kwargs, _ctx) { [[{user_id: args[0], limit: args[1]}], {}] }

result = client.replay(
  service, :process_order,
  trace_function_key: "order-processing",
  adapt_inputs: adapt
)

The hook receives the deserialized (args, kwargs) plus a per-trace ctx ({ trace_id:, source_span_id: }) and returns [new_args, new_kwargs]. The returned args is what item[:input] reports. It runs once per item, inside the same rescue as the method: if it raises, that item’s :error is set and the run continues, so one unmappable trace never crashes the batch. ctx[:trace_id] (the original Bitfab trace ID) lets a table-driven adapter look up a per-trace transform. That’s the escape hatch for reshapes that need judgement rather than mechanical rearrangement: compute the adapted inputs per trace up front, then have the hook look them up by trace_id, keeping replay deterministic instead of calling a model mid-replay. When the new signature has a genuinely new required argument with no analog in the recorded trace, don’t fabricate one. There’s nothing faithful to map it to, so leave those traces unmapped (let them raise) rather than inventing test inputs. For anything beyond a one-liner, keep the adapter in its own file next to the replay script and require it:

# scripts/replay_adapters/extraction.rb
EXTRACTION_ADAPTER = ->(args, _kwargs, _ctx) do
  user_id, limit = args
  [[{user_id:, limit:}], {}]
end

# scripts/replay.rb
require_relative "replay_adapters/extraction"

client.replay(service, :extract_memories, trace_function_key: "my-function", adapt_inputs: EXTRACTION_ADAPTER)

That keeps the transform versioned and reviewable alongside the method it adapts, and you add the require only when a drift actually needs it.

Replay Output Contract

Replay results are typically consumed by automation (CI logs, code reviewers, and coding agents). When BITFAB_REPLAY_RESULT_PATH is set, Bitfab.replay automatically writes the full replay result JSON to that file. For direct/manual runs, emit the full replay result hash as a single stdout JSON block so a consumer can JSON.parse it and reason about every field, including the new per-item :duration_ms, :tokens, and :model. Never print only lengths, counts, hashes, or truncated previews, and never replace the JSON block with ad-hoc per-field log lines. Recommended script tail:

result = Bitfab.client.replay(service, :process_order, trace_function_key: "order-processing", limit:)

# Human-readable summary goes to stderr, so stdout stays pure JSON.
warn "Test run: #{result[:test_run_url]}"
warn "Items:    #{result[:items].length}"

# Full structured dump to stdout, ready for JSON.parse.
puts JSON.pretty_generate(result)

The dumped object includes every item’s :input, :result, :original_output, :error, :duration_ms, :tokens, :model, and :trace_id, plus :test_run_id and :test_run_url. When the Bitfab plugin runs this script, it sets BITFAB_REPLAY_RESULT_PATH; the SDK writes the final result there, and the plugin reads that file into the replay run’s .bitfab/replays/<run-id>/events.jsonl while writing large per-item payloads under .bitfab/replays/<run-id>/items/. Per-item errors are part of the contract. If the wrapped method raises on a given trace, Bitfab.replay rescues it, sets item[:error], leaves item[:result] as nil, and continues. Treat items with item[:error] set as unreplayable, not as failing outputs; compute pass/fail only over items where it’s nil. This matters most for DB reads/writes: a stale FK, missing record, or rejected write is infra failure, not a regression. Don’t swallow per-item errors in the script. A custom begin/rescue that returns a placeholder turns infra failures into fake successes. Let the SDK record them. The only allowed top-level rescue is a fatal handler around main that exits non-zero, so callers can tell a whole-replay crash from a clean run with some unreplayable items. Environment. Replay executes in the app’s own process: the instrumented method is loaded as a library, and its DB clients, env vars, config loaders, and model IDs resolve from whatever environment the replay script is run under. The script must bootstrap the same environment the app uses (e.g. require "dotenv/load" at the top, or run via bundle exec dotenv ruby scripts/replay.rb). Do not mock these; they’re the same dependencies the app resolves in production. For replay to see the same DB rows the trace was captured against, point the script at the trace’s source environment (the :environment field on the trace: production / staging / development). Input serialization caveat. Replay deserializes historical span inputs and passes them back to your method. This works for strings, numbers, and plain hashes. If your span wraps a method that takes hydrated domain objects (ActiveRecord models, class instances, DB records), they won’t round-trip through serialization; move the span to where inputs are IDs or plain data and let the method fetch objects internally, or reshape arguments in the wrapper.

Replay Script

Create a standalone script to regression-test your trace functions against production data with one command. The script maps pipeline names to their replay functions, accepts CLI flags, and prints a side-by-side comparison with delta summaries.

#!/usr/bin/env ruby
# Replay production traces through instrumented functions.
#
# Uses Bitfab.client.replay to fetch real traces and re-run them
# through the current code, creating a test run for side-by-side comparison.
#
# Usage:
#   ruby scripts/replay.rb <pipeline>
#   ruby scripts/replay.rb <pipeline> --limit 20
#   ruby scripts/replay.rb <pipeline> --trace-ids id1,id2

require "dotenv/load"
require "json"
require_relative "../config/initializers/bitfab"
require_relative "../services/extraction_pipeline"
require_relative "../services/search_pipeline"

FUNCTIONS = {
  "extraction" => "my-extraction-pipeline",
  "search" => "my-search-pipeline",
}.freeze

pipeline = ARGV[0]

unless pipeline && FUNCTIONS.key?(pipeline)
  warn "Usage: ruby scripts/replay.rb <#{FUNCTIONS.keys.join('|')}> [--limit N] [--trace-ids id1,id2]"
  exit 1
end

limit = 10
trace_ids = nil

ARGV[1..].each_with_index do |arg, i|
  case arg
  when "--limit"
    limit = ARGV[i + 2].to_i
  when "--trace-ids"
    trace_ids = ARGV[i + 2].split(",").map(&:strip)
  end
end

# Each pipeline gets its own replay method. If a signature drifts after traces
# were captured, add an input adapter (see the "Adapting inputs" section):
# write scripts/replay_adapters/<name>.rb defining an adapter lambda, require it,
# and pass it here, e.g.
#   require_relative "replay_adapters/extraction"  # defines EXTRACTION_ADAPTER
#   adapt_inputs: EXTRACTION_ADAPTER

# limit is ignored when trace_ids is passed -- an explicit ID list already
# determines how many traces replay.

def replay_extraction(limit:, trace_ids:)
  service = ExtractionPipeline.new
  opts = trace_ids ? {trace_ids:} : {limit:}
  Bitfab.client.replay(
    service, :extract_memories,
    trace_function_key: FUNCTIONS["extraction"],
    # Live progress the Bitfab plugin polls while replay runs in the background.
    on_progress: Bitfab.method(:report_replay_progress),
    **opts
  )
end

def replay_search(limit:, trace_ids:)
  service = SearchPipeline.new
  opts = trace_ids ? {trace_ids:} : {limit:}
  Bitfab.client.replay(
    service, :search_documents,
    trace_function_key: FUNCTIONS["search"],
    on_progress: Bitfab.method(:report_replay_progress),
    **opts
  )
end

REPLAY_FNS = {
  "extraction" => method(:replay_extraction),
  "search" => method(:replay_search),
}.freeze

function_key = FUNCTIONS[pipeline]
# Human-readable output goes to stderr; stdout carries only the ReplayResult JSON.
$stderr.puts "[replay] Replaying #{trace_ids&.length || limit} traces from \"#{function_key}\"...\n"

result = REPLAY_FNS[pipeline].call(limit:, trace_ids:)
$stderr.puts "Test run: #{result[:test_run_url]}\n"

changed = same = errors = 0
result[:items].each do |item|
  raw_input = item[:input] || []
  label = (raw_input.first || "unknown").to_s[0, 80]

  if item[:error]
    $stderr.puts "  ✗ \"#{label}\""
    $stderr.puts "    Error: #{item[:error]}"
    errors += 1
  else
    orig = item[:original_output]
    new_val = item[:result]
    orig_str = orig.is_a?(String) ? orig : orig.to_json
    new_str = new_val.is_a?(String) ? new_val : new_val.to_json
    is_same = orig_str == new_str
    marker = is_same ? "=" : "Δ"

    $stderr.puts "  #{marker} \"#{label}\""
    $stderr.puts "    Original: #{orig_str}"
    $stderr.puts "    New:      #{new_str}"

    is_same ? same += 1 : changed += 1
  end
end

$stderr.puts "\n─── Summary ───"
$stderr.puts "  Pipeline: #{pipeline}"
$stderr.puts "  Replayed: #{result[:items].length}"
$stderr.puts "  Same:     #{same}"
$stderr.puts "  Changed:  #{changed}"
$stderr.puts "  Errors:   #{errors}" if errors > 0
$stderr.puts "\n  #{result[:test_run_url]}"

# Full ReplayResult as JSON to stdout (the Replay Output Contract).
puts JSON.pretty_generate(result)

Adapt the imports, pipeline names, and per-pipeline replay methods to match your project’s instrumented workflows.

​Installation

​Quick Start

​Basic Configuration

​API key resolution

​Tracing

​Custom (Recommended)

​Using Bitfab::Traceable to Link Spans

​Multi-File Projects

​Using bitfab_span with Explicit Key

​Automatic Nesting

​Span Options

​Span Context

​Span Prompt

​Trace Context

​Dropping a Trace

​Error Handling

​Flushing Traces

​Wrapping Third-Party Methods

​Replay

​Mock child spans during replay

​Fluent API: client.get_function

​Adapting inputs after a signature change

​Replay Output Contract

​Replay Script

Installation

Quick Start

Basic Configuration

API key resolution

Tracing

Custom (Recommended)

Using `Bitfab::Traceable` to Link Spans

Multi-File Projects

Using `bitfab_span` with Explicit Key

Automatic Nesting

Span Options

Span Context

Span Prompt

Trace Context

Dropping a Trace

Error Handling

Flushing Traces

Wrapping Third-Party Methods

Replay

Mock child spans during replay

Fluent API: `client.get_function`

Adapting inputs after a signature change

Replay Output Contract

Replay Script