feat(streaming): add Executor.execute_stream() returning AsyncIterator[str] for token-by-token delivery #45

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hurui200320 merged 1 commit from feature/streaming-execute-stream into master 2026-06-12 12:29:49 +00:00

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hurui200320 commented 2026-06-11 14:04:20 +00:00

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Summary

Implements the complete streaming execution path for the CleverThis router, enabling token-by-token delivery to end-users on long-running LLM calls.

Motivation

The actor lifecycle requires both non-streaming and streaming execution (Step 6). Previously, LLMAgent.process_message() called ainvoke() only — buffering the full LLM response before returning. There was no token-by-token delivery path anywhere in PureLangGraph or LLMAgent.

What Was Implemented

New APIs

LLMAgent.stream_message(message, context) — agents/llm.py
Async generator calling self.chat_model.astream(messages) and yielding str(chunk.content) per chunk (with None-guard: metadata-only chunks with content=None yield "" instead of the literal string "None"). Captures token counts from the final chunk using the same three-tier _safe_int() fallback chain as process_message(). Applies _temperature_override from context (spec §4.4.5). Updates memory after streaming if memory_enabled is set (spec §4.4.4).

Token accumulation (O(n²) fix + m1 fix): stream_message() now uses a list accumulator (agent_response_parts: list[str]) and "".join(agent_response_parts) at the end instead of agent_response += token. The accumulation is only performed when memory_enabled is True — the append is inside the if _memory_enabled: block, so long responses with memory disabled do not grow a large list that is never consumed.

Node._stream_agent(state) — langgraph/nodes.py
Async generator mirroring _execute_agent() but using agent.stream_message() for LLMAgent instances. Exceptions are re-raised (not swallowed) so callers can map them to HTTP 5xx/4xx. Does not propagate context changes back to state.metadata (intentional asymmetry with _execute_agent(); documented in docstring; deferred to follow-up PR).

PureLangGraph.execute_stream() + _stream_from_node() — langgraph/pure_graph.py
Async generator mirroring execute(). Uses astream() only for terminal AGENT nodes (AC2).

Token delivery behaviour:

• For statically-terminal AGENT nodes whose edges are all unconditional, tokens are yielded immediately as they arrive AND accumulated into _collected_tokens — true token-by-token delivery with correct full_response (C1 fix).
• For statically-terminal AGENT nodes that have any conditional edge, tokens are buffered until the LLM call completes so that full_response is available for edge-condition evaluation.

GOTO_/ROUTE_ routing command parsing (Issue 3 fix): All three branches of _stream_from_node() now parse GOTO_*/ROUTE_* prefixes from node output and store the target in state.metadata["next_node"], mirroring _execute_from_node. This eliminates the behavioral asymmetry where graphs relying on routing commands routed correctly under execute() but incorrectly under execute_stream(). This covers:

• Terminal AGENT branch
• Intermediate AGENT branch
• Non-AGENT branch (function/tool nodes) — added in review round 7

M3 fix: Non-ExecutionError exceptions from _stream_agent() and intermediate AGENT ainvoke() are now re-raised as ExecutionError (wrapping the original cause) instead of being silently swallowed. Error messages are sanitised (no {e} interpolation) to avoid leaking sensitive provider details (API key fragments, internal URLs); from e preserves the cause chain.

_execute_llm_stream() / _execute_graph_stream() — runtime_dispatch.py
Async generator dispatch functions mirroring _execute_llm() / _execute_graph(). Set executor.last_result after the stream is exhausted using collected token usage.

Billing-integrity guarantee (Issues 1 & 2 fix): Both _execute_llm_stream() and _execute_graph_stream() now wrap their early config-validation blocks (temperature/max_tokens/timeout_ms for LLM; node/edge validation loop for graph) in a try/except that sets a <no_llm> placeholder ActorResult on executor.last_result before re-raising. This ensures the billing-integrity guarantee holds for all exception paths, including early config errors that fire before the main try/except block.

Execution limit enforcement (AC5):

• Graph path: timeout_ms wraps _collect_stream_tokens in asyncio.wait_for inside execute_stream(); max_cost_usd is enforced after each node's token usage is collected in _stream_from_node().
• LLM path (M1 fix from review round 3): timeout_ms wraps the entire agent.stream_message() call via asyncio.wait_for(_collect_llm_stream_tokens(...)), converting asyncio.TimeoutError to ExecutionError(kind="timeout"); max_cost_usd is enforced after the stream completes by computing cost from executor.pricing[provider][model] and raising ExecutionError(kind="cost", reason="budget_exhausted") if exceeded.

M2 fix (both paths): Both _execute_llm_stream() and _execute_graph_stream() now populate executor.last_result on the exception path before re-raising. The except (ConfigurationError, AgentCreationError, ExecutionError) blocks read captured token counts and build a partial ActorResult.

M-1 fix (review round 4 — billing integrity for cost check): The max_cost_usd enforcement block in _execute_llm_stream() is now placed inside the try/except block (before the success executor.last_result assignment). This ensures that when the cost check raises ExecutionError (e.g. budget_exhausted, missing_pricing_entry, invalid rate), the existing except (ConfigurationError, ExecutionError, AgentCreationError) handler populates executor.last_result before re-raising — satisfying the billing-integrity guarantee documented in runtime.py. Previously the cost check was outside the try/except, causing executor.last_result to remain None on cost-check failures.

m1 fix (LLM path, review round 3): _execute_llm_stream() now populates executor.last_result with a <no_llm> placeholder when factory.create_agent() raises ConfigurationError or AgentCreationError, mirroring the graph path's N5 fix.

M1 fix: The bare except Exception as exc: block in _execute_graph_stream now also sets executor.last_result before re-raising as ExecutionError, mirroring the LLM path.

Executor.execute_stream(message) + Executor.last_result — runtime.py
Public async generator dispatching to _execute_llm_stream() (llm actors) or _execute_graph_stream() (graph actors). last_result: ActorResult | None = None is set after iterator exhaustion. Docstring updated to reflect that last_result is also set on exception paths (billing-integrity guarantee).

Resource leak fix (Issue 4): Executor.execute_stream() now explicitly closes the inner generator in a try/finally block (await gen.aclose()), ensuring agent.cleanup() (which closes httpx.AsyncClient instances) is called promptly even when the caller abandons the iterator early. Without this, abandoned async generators are closed non-deterministically by the GC.

Variable Naming Cleanup (Issue 8)

Renamed review-round-marker prefixes in _execute_llm_stream and _execute_graph_stream:

• _m2_tok_var, _m2_tok_inst, _m2_usage → _exc_tok_var, _exc_tok_inst, _exc_usage
• _m2_nodes, _m1_nodes → _exc_nodes, _unexp_nodes

Dead Code Removal (M2 fix from review round 3)

The C3 guard (if content_next_nodes:) and parallel block in the terminal AGENT branch of _stream_from_node() were provably unreachable: _statically_terminal=True guarantees all static successors are END/end sentinels, so _get_next_nodes() can only return those same targets, making content_next_nodes always empty. These dead code blocks have been removed. The terminal branch now directly cleans up the execution path and yields buffered tokens (if not fast path), then returns.

The scenario previously titled "C3 guard fires in terminal AGENT branch" has been corrected: the graph in that test has agent1 with edges to both end (static) AND router (conditional: always), making _statically_terminal=False for agent1 (because router is a non-END static successor). The scenario actually exercises the intermediate AGENT branch. The title and comments have been updated accordingly.

Consistency Fix (m3)

The non-streaming path's end-node check now uses _END_MARKERS constant instead of the hardcoded if node_name == "end" or node_name == "END": pattern, consistent with the streaming path.

Other Fixes

m4 fix (dead initialization): full_response: str = str(message) changed to full_response: str = "" with a comment explaining it is a type-annotation placeholder. The str(message) initial value was a pre-C1 fallback that is no longer reachable.

m5 fix (docstring): _stream_agent() docstring now explicitly states that context changes made by the agent during streaming are not propagated back to state.metadata (intentional asymmetry with _execute_agent(); deferred to follow-up PR).

m6 fix (test assertion): The conditional-edge slow-path scenario now asserts executor.last_result.response == "Buffered", verifying the C1 fix's core guarantee that full_response is always the LLM's actual response.

M4 fix test corrected: The M4 fix test now uses max_depth=1 with a start → agent_start → {agent_a, agent_b} → end graph. agent_start (depth 1) is within the limit; agent_a and agent_b (depth 2) exceed it, actually exercising the _collect_stream_tokens(nn, full_response, depth + 1) call in the parallel block.

m5 fix test corrected: The _last_token_usage assertion now directly checks agent._last_token_usage == (0, 0) by capturing the agent reference in the When-step via context.es_agent.

m3 fix (review round 4 — success-path token validation): The success-path token-usage fallback in _execute_llm_stream() now validates that both elements of the _last_token_usage tuple are int (mirroring the exception-path's validation), preventing a TypeError from propagating outside the try/except block if a custom non-LLM agent has non-integer token counts.

n-3 fix (review round 4 — variable naming): Renamed agent_name_n → agent_name and nid → node_id in _execute_graph_stream() for consistency with _execute_graph().

m-4 fix (review round 4 — error message sanitisation): Both _stream_from_node() exception handlers that wrap non-ExecutionError exceptions now use sanitised messages ("Agent node streaming failed", "Intermediate agent node failed") without {e} interpolation, preventing sensitive provider details from leaking. The cause chain is preserved via from e.

Review Round 5 Fixes

Major Issues Fixed

Issue 1 (blocking) — _execute_graph_stream() outer exception handler leaks exception details:
The outer except Exception as exc: handler in _execute_graph_stream() raised ExecutionError(f"Graph execution failed: {exc}"), embedding the raw exception string in the user-visible error message. This could leak sensitive provider details (API key fragments, HTTP error bodies, internal URLs). Fixed to raise ExecutionError("Graph execution failed") from exc — preserves the cause chain while sanitising the message. Consistent with the PR's own m-4 fix policy applied to _stream_from_node().

Issue 6 — Agent-creation exception wrapping in _execute_graph_stream() leaks exception details:
The inner except Exception as exc: block during agent creation raised ConfigurationError(f"Failed to create agent '{agent_name}': {exc}"). Fixed to ConfigurationError(f"Failed to create agent '{agent_name}'") from exc — sanitised message, cause chain preserved. Added a comment explaining the rationale.

Minor Issues Fixed

Issue 2 — stream_message() missing except LangChainException handler (asymmetric logging):
Added a dedicated except LangChainException as e: arm to stream_message() between except ConfigurationError and except Exception, with the same billing-integrity logic and a distinct log message ("LLM agent %s LangChain streaming error: %s"). This makes log analytics symmetric with process_message() — alert rules filtering on "LangChain error" will now also catch the same condition in the streaming path.

Issue 3 — Executor.execute_stream() docstring missing abandoned-stream behavior:
Added a .. note:: block to the docstring: "If the caller abandons the iterator before exhaustion (e.g. by breaking out of the async for loop), last_result remains None. Callers must exhaust the iterator to obtain complete billing data."

Issue 4 — Buffering test cannot distinguish fast/slow path:
Added a comment block above the scenario acknowledging that it verifies end-state only (final token list and concatenated response), not the internal buffering behaviour. The comment explains why a regression removing the buffering code would not be caught by this test, and points to the C1 fix assertion (executor.last_result.response == "Buffered") as the correctness anchor.

Issue 5 — Docstring incorrectly claims last_result populated for unsupported actor type:
Updated the execute_stream() docstring to clarify that the billing-integrity guarantee applies only when the dispatch function is reached (i.e. for "llm" and "graph" actor types). For unsupported types ("tool", "multi_actor"), last_result remains None because no LLM call was attempted.

Issue 7 — Vacuous truth not commented in _statically_terminal / _all_edges_unconditional:
Added brief notes to both all(...) expressions explaining the design intent: "A node with no outgoing edges is intentionally treated as a fast-path terminal (no successors = effectively end-of-graph)."

Issue 8 — Actor-type detection logic duplicated between execute() and execute_stream():
Extracted a private _detect_actor_type(self) -> str helper method on Executor. Both execute() and execute_stream() now call self._detect_actor_type() instead of duplicating the 8-line detection block.

Issue 9 — Non-numeric max_depth in streaming path not tested:
Added a new BDD scenario: "execute_stream with non-numeric max_depth raises ExecutionError kind depth". Added the corresponding step definition step_es_graph_string_max_depth in execute_stream_steps.py that creates an executor with limits={"max_depth": "not_a_number"}. This exercises the except (TypeError, ValueError) path in _collect_stream_tokens() at pure_graph.py.

Review Round 6 Fixes

Major Issues Fixed

Issues 1 & 2 (billing-integrity for early config-validation errors):

• _execute_llm_stream: The temperature/max_tokens/timeout_ms validations now run inside a try/except (ConfigurationError, ExecutionError) wrapper that sets a <no_llm> placeholder ActorResult on executor.last_result before re-raising. This ensures the billing-integrity guarantee holds even for early config errors that fire before the agent is created.
• _execute_graph_stream: The node/edge validation loop now runs inside a try/except ConfigurationError wrapper with the same <no_llm> placeholder treatment.

Issue 3 (GOTO_/ROUTE_ routing command parsing in streaming path):
Both the terminal AGENT branch and the intermediate AGENT branch of _stream_from_node() now parse GOTO_*/ROUTE_* prefixes from agent output and store the target in state.metadata["next_node"], mirroring _execute_from_node. This eliminates the behavioral asymmetry where graphs relying on LLM-emitted routing commands routed correctly under execute() but incorrectly under execute_stream().

Issue 4 (resource leak — agent.cleanup() not guaranteed on abandoned streams):
Executor.execute_stream() now wraps the inner generator iteration in try/finally with await gen.aclose() for both the LLM and graph paths. This ensures agent.cleanup() (which closes httpx.AsyncClient instances) is called promptly even when the caller abandons the iterator early.

Minor Issues Fixed

Issue 5 (misleading comment in terminal AGENT branch):
The comment "Always update last_output for routing (mirrors non-streaming path)" has been corrected to "Update last_output for routing (mirrors non-streaming path)" with an explicit note that this is only reached on the success path (the except blocks re-raise).

Issue 6 (missing test for except Exception path in _execute_llm_stream):
Added a new BDD scenario: "_execute_llm_stream populates executor.last_result when unexpected RuntimeError is raised during streaming". This verifies that the except Exception block sets executor.last_result before re-raising as ExecutionError.

Issue 7 (partial tokens lost on timeout — undocumented):
Added a .. note:: block to the execute_stream() docstring documenting that when timeout_ms fires, any tokens already generated but not yet yielded are discarded and executor.last_result.response will be "".

Issue 8 (review-marker prefixes in variable names):
Renamed _m2_tok_var, _m2_tok_inst, _m2_usage, _m2_nodes, _m1_nodes to _exc_tok_var, _exc_tok_inst, _exc_usage, _exc_nodes, _unexp_nodes respectively.

Issue 9 (docstring inaccuracy in _stream_from_node):
Updated docstring: "after each terminal AGENT node's token usage is collected" → "after each AGENT node's (both terminal and intermediate) token usage is collected".

Issue 10 (misleading buffered variable name):
Renamed buffered to _collected_tokens in the terminal AGENT branch of _stream_from_node(). The new name accurately reflects that tokens are always accumulated for full_response assembly, regardless of whether they are also yielded immediately (fast path) or held back (slow path).

Issue 11 (str(chunk.content) coerces None to "None"):
Changed token = str(chunk.content) to token = str(chunk.content) if chunk.content is not None else "" in LLMAgent.stream_message(). Metadata-only chunks with content=None now yield "" instead of the literal string "None".

Also added BDD scenarios for Issues 1, 2, and 3 to verify the new behavior.

Review Round 7 Fixes

Major Issues Fixed

Issue 1 — GOTO_/ROUTE_ parsing missing in non-AGENT branch of _stream_from_node():
The non-AGENT branch (function/tool nodes) was missing the same GOTO_/ROUTE_ parsing that exists in _execute_from_node() for all node types. Added the same parsing block immediately after state.metadata["last_output"] = output_message in the non-AGENT branch. This eliminates the behavioral asymmetry where a function node emitting "GOTO_validation:..." would correctly set state.metadata["next_node"] under execute() but not under execute_stream(). Added a BDD scenario to verify this fix.

Issue 2 — str(None) yields literal "None" token in intermediate AGENT branch:
When last_msg["content"] is None (e.g. a metadata-only provider response), full_response can be None in the intermediate AGENT branch. The two yield str(full_response) sites (the "no routing command → return to user" guard and the "dynamically terminal" path) now use yield str(full_response) if full_response is not None else "", mirroring the chunk.content guard in LLMAgent.stream_message(). Added a BDD scenario to verify this fix.

Should-Fix Issues Addressed

Issue 3 — _START_MARKERS not used for start-node check (inconsistency):
Both _execute_from_node() and _stream_from_node() had if node_name == "start": hardcoded, inconsistent with the _END_MARKERS refactor. Changed both call sites to if node_name in _START_MARKERS: for consistency.

Issue 4 — except LangChainException arm in stream_message() has no test:
Added a BDD scenario that injects LangChainException into astream() and asserts ExecutionError is raised. This exercises the dedicated except LangChainException arm added in review round 5 and prevents silent regressions.

Issue 5 — Resource-leak test doesn't verify agent.cleanup() was called:
Added a new BDD scenario "execute_stream abandonment calls agent.cleanup() promptly" that replaces agent.cleanup with AsyncMock() and asserts cleanup.called after stream abandonment. This is the key assertion the existing abandonment test was missing.

Issue 6 — ExecutionError.reason not asserted in cost-error scenarios:
Added two new BDD scenarios that assert both error.kind and error.reason for budget_exhausted and missing_pricing_entry cost errors. Added a new Then-step an ExecutionError with kind "{kind}" and reason "{reason}" should be raised (stream kind+reason) to support this.

Tests

• 151 BDD scenarios in features/execute_stream.feature (143 from previous rounds + 8 new for review round 7 fixes)
• All existing unit tests continue to pass (non-streaming paths unaffected)
• Coverage: 96.9% (threshold: 96.5%)

Quality Gates

• ✅ nox -e lint — All checks passed
• ✅ nox -e typecheck — 0 errors (Pyright)
• ✅ nox -e unit_tests — 2556 scenarios passed
• ✅ nox -e integration_tests — All tests passed
• ✅ nox -e coverage_report — 96.9% (threshold: 96.5%)

Deferred Items

The following items are deferred to follow-up PRs:

• Issue 3 (review round 7) — _accumulated_cost race condition in parallel streaming: Pre-existing non-atomic read-modify-write; parallel execution is an edge case; documented as best-effort in the cost enforcement code.
• Issue 4 (review round 7) — executor.last_result is None on abandoned stream: Documented limitation in the execute_stream() docstring. Implementing partial billing recovery on abandoned streams requires significant additional infrastructure.
• Issue 7 (review round 7) — Slow-path buffering test cannot distinguish fast/slow path: Acknowledged in scenario comments; the C1 fix assertion (executor.last_result.response == "Buffered") serves as the correctness anchor.
• N1 (review round 7) — Cost enforcement block duplicated 4 times: Deferred as n-2 from previous rounds; extract _enforce_cost_limit() helper as follow-up.
• N2 (review round 7) — auto_finish_active extraction duplicated 4 times: Extract _is_auto_finish_active() helper as follow-up.
• N3 (review round 7) — _stream_from_node is ~800 lines: Decompose into private helpers as follow-up.
• m-5: Unbounded memory in _collect_stream_tokens helpers — larger scope change; documented in execute_stream() docstring as a known limitation
• n-1: _temperature_override not range-checked — pre-existing gap in process_message() as well; separate ticket needed
• n-6: _execute_graph_stream / _execute_llm_stream duplicate ~80% of non-streaming counterparts — extract shared setup helpers as follow-up
• Deferred from round 2: Loop detection duplicated between streaming and non-streaming paths

Closes #16

## Summary Implements the complete streaming execution path for the CleverThis router, enabling token-by-token delivery to end-users on long-running LLM calls. ## Motivation The actor lifecycle requires both non-streaming and streaming execution (Step 6). Previously, `LLMAgent.process_message()` called `ainvoke()` only — buffering the full LLM response before returning. There was no token-by-token delivery path anywhere in `PureLangGraph` or `LLMAgent`. ## What Was Implemented ### New APIs **`LLMAgent.stream_message(message, context)` — `agents/llm.py`** Async generator calling `self.chat_model.astream(messages)` and yielding `str(chunk.content)` per chunk (with `None`-guard: metadata-only chunks with `content=None` yield `""` instead of the literal string `"None"`). Captures token counts from the final chunk using the same three-tier `_safe_int()` fallback chain as `process_message()`. Applies `_temperature_override` from context (spec §4.4.5). Updates memory after streaming if `memory_enabled` is set (spec §4.4.4). **Token accumulation (O(n²) fix + m1 fix):** `stream_message()` now uses a list accumulator (`agent_response_parts: list[str]`) and `"".join(agent_response_parts)` at the end instead of `agent_response += token`. The accumulation is only performed when `memory_enabled` is `True` — the append is inside the `if _memory_enabled:` block, so long responses with memory disabled do not grow a large list that is never consumed. **`Node._stream_agent(state)` — `langgraph/nodes.py`** Async generator mirroring `_execute_agent()` but using `agent.stream_message()` for `LLMAgent` instances. Exceptions are re-raised (not swallowed) so callers can map them to HTTP 5xx/4xx. Does not propagate context changes back to `state.metadata` (intentional asymmetry with `_execute_agent()`; documented in docstring; deferred to follow-up PR). **`PureLangGraph.execute_stream()` + `_stream_from_node()` — `langgraph/pure_graph.py`** Async generator mirroring `execute()`. Uses `astream()` only for terminal AGENT nodes (AC2). **Token delivery behaviour:** - For statically-terminal AGENT nodes whose edges are all **unconditional**, tokens are yielded immediately as they arrive AND accumulated into `_collected_tokens` — true token-by-token delivery with correct `full_response` (C1 fix). - For statically-terminal AGENT nodes that have any **conditional** edge, tokens are buffered until the LLM call completes so that `full_response` is available for edge-condition evaluation. **GOTO_/ROUTE_ routing command parsing (Issue 3 fix):** All three branches of `_stream_from_node()` now parse `GOTO_*/ROUTE_*` prefixes from node output and store the target in `state.metadata["next_node"]`, mirroring `_execute_from_node`. This eliminates the behavioral asymmetry where graphs relying on routing commands routed correctly under `execute()` but incorrectly under `execute_stream()`. This covers: - Terminal AGENT branch - Intermediate AGENT branch - Non-AGENT branch (function/tool nodes) — **added in review round 7** **M3 fix:** Non-`ExecutionError` exceptions from `_stream_agent()` and intermediate AGENT `ainvoke()` are now re-raised as `ExecutionError` (wrapping the original cause) instead of being silently swallowed. Error messages are sanitised (no `{e}` interpolation) to avoid leaking sensitive provider details (API key fragments, internal URLs); `from e` preserves the cause chain. **`_execute_llm_stream()` / `_execute_graph_stream()` — `runtime_dispatch.py`** Async generator dispatch functions mirroring `_execute_llm()` / `_execute_graph()`. Set `executor.last_result` after the stream is exhausted using collected token usage. **Billing-integrity guarantee (Issues 1 & 2 fix):** Both `_execute_llm_stream()` and `_execute_graph_stream()` now wrap their early config-validation blocks (temperature/max_tokens/timeout_ms for LLM; node/edge validation loop for graph) in a `try/except` that sets a `<no_llm>` placeholder `ActorResult` on `executor.last_result` before re-raising. This ensures the billing-integrity guarantee holds for all exception paths, including early config errors that fire before the main `try/except` block. **Execution limit enforcement (AC5):** - **Graph path:** `timeout_ms` wraps `_collect_stream_tokens` in `asyncio.wait_for` inside `execute_stream()`; `max_cost_usd` is enforced after each node's token usage is collected in `_stream_from_node()`. - **LLM path (M1 fix from review round 3):** `timeout_ms` wraps the entire `agent.stream_message()` call via `asyncio.wait_for(_collect_llm_stream_tokens(...))`, converting `asyncio.TimeoutError` to `ExecutionError(kind="timeout")`; `max_cost_usd` is enforced after the stream completes by computing cost from `executor.pricing[provider][model]` and raising `ExecutionError(kind="cost", reason="budget_exhausted")` if exceeded. **M2 fix (both paths):** Both `_execute_llm_stream()` and `_execute_graph_stream()` now populate `executor.last_result` on the exception path before re-raising. The `except (ConfigurationError, AgentCreationError, ExecutionError)` blocks read captured token counts and build a partial `ActorResult`. **M-1 fix (review round 4 — billing integrity for cost check):** The `max_cost_usd` enforcement block in `_execute_llm_stream()` is now placed **inside** the `try/except` block (before the success `executor.last_result` assignment). This ensures that when the cost check raises `ExecutionError` (e.g. `budget_exhausted`, `missing_pricing_entry`, invalid rate), the existing `except (ConfigurationError, ExecutionError, AgentCreationError)` handler populates `executor.last_result` before re-raising — satisfying the billing-integrity guarantee documented in `runtime.py`. Previously the cost check was outside the `try/except`, causing `executor.last_result` to remain `None` on cost-check failures. **m1 fix (LLM path, review round 3):** `_execute_llm_stream()` now populates `executor.last_result` with a `<no_llm>` placeholder when `factory.create_agent()` raises `ConfigurationError` or `AgentCreationError`, mirroring the graph path's N5 fix. **M1 fix:** The bare `except Exception as exc:` block in `_execute_graph_stream` now also sets `executor.last_result` before re-raising as `ExecutionError`, mirroring the LLM path. **`Executor.execute_stream(message)` + `Executor.last_result` — `runtime.py`** Public async generator dispatching to `_execute_llm_stream()` (llm actors) or `_execute_graph_stream()` (graph actors). `last_result: ActorResult | None = None` is set after iterator exhaustion. Docstring updated to reflect that `last_result` is also set on exception paths (billing-integrity guarantee). **Resource leak fix (Issue 4):** `Executor.execute_stream()` now explicitly closes the inner generator in a `try/finally` block (`await gen.aclose()`), ensuring `agent.cleanup()` (which closes `httpx.AsyncClient` instances) is called promptly even when the caller abandons the iterator early. Without this, abandoned async generators are closed non-deterministically by the GC. ### Variable Naming Cleanup (Issue 8) Renamed review-round-marker prefixes in `_execute_llm_stream` and `_execute_graph_stream`: - `_m2_tok_var`, `_m2_tok_inst`, `_m2_usage` → `_exc_tok_var`, `_exc_tok_inst`, `_exc_usage` - `_m2_nodes`, `_m1_nodes` → `_exc_nodes`, `_unexp_nodes` ### Dead Code Removal (M2 fix from review round 3) The C3 guard (`if content_next_nodes:`) and parallel block in the **terminal AGENT branch** of `_stream_from_node()` were provably unreachable: `_statically_terminal=True` guarantees all static successors are END/end sentinels, so `_get_next_nodes()` can only return those same targets, making `content_next_nodes` always empty. These dead code blocks have been removed. The terminal branch now directly cleans up the execution path and yields buffered tokens (if not fast path), then returns. The scenario previously titled "C3 guard fires in terminal AGENT branch" has been corrected: the graph in that test has `agent1` with edges to both `end` (static) AND `router` (conditional: always), making `_statically_terminal=False` for `agent1` (because `router` is a non-END static successor). The scenario actually exercises the **intermediate** AGENT branch. The title and comments have been updated accordingly. ### Consistency Fix (m3) The non-streaming path's end-node check now uses `_END_MARKERS` constant instead of the hardcoded `if node_name == "end" or node_name == "END":` pattern, consistent with the streaming path. ### Other Fixes **m4 fix (dead initialization):** `full_response: str = str(message)` changed to `full_response: str = ""` with a comment explaining it is a type-annotation placeholder. The `str(message)` initial value was a pre-C1 fallback that is no longer reachable. **m5 fix (docstring):** `_stream_agent()` docstring now explicitly states that context changes made by the agent during streaming are not propagated back to `state.metadata` (intentional asymmetry with `_execute_agent()`; deferred to follow-up PR). **m6 fix (test assertion):** The conditional-edge slow-path scenario now asserts `executor.last_result.response == "Buffered"`, verifying the C1 fix's core guarantee that `full_response` is always the LLM's actual response. **M4 fix test corrected:** The M4 fix test now uses `max_depth=1` with a `start → agent_start → {agent_a, agent_b} → end` graph. `agent_start` (depth 1) is within the limit; `agent_a` and `agent_b` (depth 2) exceed it, actually exercising the `_collect_stream_tokens(nn, full_response, depth + 1)` call in the parallel block. **m5 fix test corrected:** The `_last_token_usage` assertion now directly checks `agent._last_token_usage == (0, 0)` by capturing the agent reference in the When-step via `context.es_agent`. **m3 fix (review round 4 — success-path token validation):** The success-path token-usage fallback in `_execute_llm_stream()` now validates that both elements of the `_last_token_usage` tuple are `int` (mirroring the exception-path's validation), preventing a `TypeError` from propagating outside the `try/except` block if a custom non-LLM agent has non-integer token counts. **n-3 fix (review round 4 — variable naming):** Renamed `agent_name_n` → `agent_name` and `nid` → `node_id` in `_execute_graph_stream()` for consistency with `_execute_graph()`. **m-4 fix (review round 4 — error message sanitisation):** Both `_stream_from_node()` exception handlers that wrap non-`ExecutionError` exceptions now use sanitised messages (`"Agent node streaming failed"`, `"Intermediate agent node failed"`) without `{e}` interpolation, preventing sensitive provider details from leaking. The cause chain is preserved via `from e`. ## Review Round 5 Fixes ### Major Issues Fixed **Issue 1 (blocking) — `_execute_graph_stream()` outer exception handler leaks exception details:** The outer `except Exception as exc:` handler in `_execute_graph_stream()` raised `ExecutionError(f"Graph execution failed: {exc}")`, embedding the raw exception string in the user-visible error message. This could leak sensitive provider details (API key fragments, HTTP error bodies, internal URLs). Fixed to `raise ExecutionError("Graph execution failed") from exc` — preserves the cause chain while sanitising the message. Consistent with the PR's own `m-4 fix` policy applied to `_stream_from_node()`. **Issue 6 — Agent-creation exception wrapping in `_execute_graph_stream()` leaks exception details:** The inner `except Exception as exc:` block during agent creation raised `ConfigurationError(f"Failed to create agent '{agent_name}': {exc}")`. Fixed to `ConfigurationError(f"Failed to create agent '{agent_name}'") from exc` — sanitised message, cause chain preserved. Added a comment explaining the rationale. ### Minor Issues Fixed **Issue 2 — `stream_message()` missing `except LangChainException` handler (asymmetric logging):** Added a dedicated `except LangChainException as e:` arm to `stream_message()` between `except ConfigurationError` and `except Exception`, with the same billing-integrity logic and a distinct log message (`"LLM agent %s LangChain streaming error: %s"`). This makes log analytics symmetric with `process_message()` — alert rules filtering on "LangChain error" will now also catch the same condition in the streaming path. **Issue 3 — `Executor.execute_stream()` docstring missing abandoned-stream behavior:** Added a `.. note::` block to the docstring: "If the caller abandons the iterator before exhaustion (e.g. by breaking out of the `async for` loop), `last_result` remains `None`. Callers must exhaust the iterator to obtain complete billing data." **Issue 4 — Buffering test cannot distinguish fast/slow path:** Added a comment block above the scenario acknowledging that it verifies end-state only (final token list and concatenated response), not the internal buffering behaviour. The comment explains why a regression removing the buffering code would not be caught by this test, and points to the C1 fix assertion (`executor.last_result.response == "Buffered"`) as the correctness anchor. **Issue 5 — Docstring incorrectly claims `last_result` populated for unsupported actor type:** Updated the `execute_stream()` docstring to clarify that the billing-integrity guarantee applies only when the dispatch function is reached (i.e. for `"llm"` and `"graph"` actor types). For unsupported types (`"tool"`, `"multi_actor"`), `last_result` remains `None` because no LLM call was attempted. **Issue 7 — Vacuous truth not commented in `_statically_terminal` / `_all_edges_unconditional`:** Added brief notes to both `all(...)` expressions explaining the design intent: "A node with no outgoing edges is intentionally treated as a fast-path terminal (no successors = effectively end-of-graph)." **Issue 8 — Actor-type detection logic duplicated between `execute()` and `execute_stream()`:** Extracted a private `_detect_actor_type(self) -> str` helper method on `Executor`. Both `execute()` and `execute_stream()` now call `self._detect_actor_type()` instead of duplicating the 8-line detection block. **Issue 9 — Non-numeric `max_depth` in streaming path not tested:** Added a new BDD scenario: "execute_stream with non-numeric max_depth raises ExecutionError kind depth". Added the corresponding step definition `step_es_graph_string_max_depth` in `execute_stream_steps.py` that creates an executor with `limits={"max_depth": "not_a_number"}`. This exercises the `except (TypeError, ValueError)` path in `_collect_stream_tokens()` at `pure_graph.py`. ## Review Round 6 Fixes ### Major Issues Fixed **Issues 1 & 2 (billing-integrity for early config-validation errors):** - `_execute_llm_stream`: The temperature/max_tokens/timeout_ms validations now run inside a `try/except (ConfigurationError, ExecutionError)` wrapper that sets a `<no_llm>` placeholder `ActorResult` on `executor.last_result` before re-raising. This ensures the billing-integrity guarantee holds even for early config errors that fire before the agent is created. - `_execute_graph_stream`: The node/edge validation loop now runs inside a `try/except ConfigurationError` wrapper with the same `<no_llm>` placeholder treatment. **Issue 3 (GOTO_/ROUTE_ routing command parsing in streaming path):** Both the terminal AGENT branch and the intermediate AGENT branch of `_stream_from_node()` now parse `GOTO_*/ROUTE_*` prefixes from agent output and store the target in `state.metadata["next_node"]`, mirroring `_execute_from_node`. This eliminates the behavioral asymmetry where graphs relying on LLM-emitted routing commands routed correctly under `execute()` but incorrectly under `execute_stream()`. **Issue 4 (resource leak — `agent.cleanup()` not guaranteed on abandoned streams):** `Executor.execute_stream()` now wraps the inner generator iteration in `try/finally` with `await gen.aclose()` for both the LLM and graph paths. This ensures `agent.cleanup()` (which closes `httpx.AsyncClient` instances) is called promptly even when the caller abandons the iterator early. ### Minor Issues Fixed **Issue 5 (misleading comment in terminal AGENT branch):** The comment "Always update last_output for routing (mirrors non-streaming path)" has been corrected to "Update last_output for routing (mirrors non-streaming path)" with an explicit note that this is only reached on the success path (the except blocks re-raise). **Issue 6 (missing test for `except Exception` path in `_execute_llm_stream`):** Added a new BDD scenario: "_execute_llm_stream populates executor.last_result when unexpected RuntimeError is raised during streaming". This verifies that the `except Exception` block sets `executor.last_result` before re-raising as `ExecutionError`. **Issue 7 (partial tokens lost on timeout — undocumented):** Added a `.. note::` block to the `execute_stream()` docstring documenting that when `timeout_ms` fires, any tokens already generated but not yet yielded are discarded and `executor.last_result.response` will be `""`. **Issue 8 (review-marker prefixes in variable names):** Renamed `_m2_tok_var`, `_m2_tok_inst`, `_m2_usage`, `_m2_nodes`, `_m1_nodes` to `_exc_tok_var`, `_exc_tok_inst`, `_exc_usage`, `_exc_nodes`, `_unexp_nodes` respectively. **Issue 9 (docstring inaccuracy in `_stream_from_node`):** Updated docstring: "after each **terminal** AGENT node's token usage is collected" → "after each AGENT node's (both terminal and intermediate) token usage is collected". **Issue 10 (misleading `buffered` variable name):** Renamed `buffered` to `_collected_tokens` in the terminal AGENT branch of `_stream_from_node()`. The new name accurately reflects that tokens are always accumulated for `full_response` assembly, regardless of whether they are also yielded immediately (fast path) or held back (slow path). **Issue 11 (`str(chunk.content)` coerces `None` to `"None"`):** Changed `token = str(chunk.content)` to `token = str(chunk.content) if chunk.content is not None else ""` in `LLMAgent.stream_message()`. Metadata-only chunks with `content=None` now yield `""` instead of the literal string `"None"`. Also added BDD scenarios for Issues 1, 2, and 3 to verify the new behavior. ## Review Round 7 Fixes ### Major Issues Fixed **Issue 1 — GOTO_/ROUTE_ parsing missing in non-AGENT branch of `_stream_from_node()`:** The non-AGENT branch (function/tool nodes) was missing the same GOTO_/ROUTE_ parsing that exists in `_execute_from_node()` for all node types. Added the same parsing block immediately after `state.metadata["last_output"] = output_message` in the non-AGENT branch. This eliminates the behavioral asymmetry where a function node emitting `"GOTO_validation:..."` would correctly set `state.metadata["next_node"]` under `execute()` but not under `execute_stream()`. Added a BDD scenario to verify this fix. **Issue 2 — `str(None)` yields literal `"None"` token in intermediate AGENT branch:** When `last_msg["content"]` is `None` (e.g. a metadata-only provider response), `full_response` can be `None` in the intermediate AGENT branch. The two `yield str(full_response)` sites (the "no routing command → return to user" guard and the "dynamically terminal" path) now use `yield str(full_response) if full_response is not None else ""`, mirroring the `chunk.content` guard in `LLMAgent.stream_message()`. Added a BDD scenario to verify this fix. ### Should-Fix Issues Addressed **Issue 3 — `_START_MARKERS` not used for start-node check (inconsistency):** Both `_execute_from_node()` and `_stream_from_node()` had `if node_name == "start":` hardcoded, inconsistent with the `_END_MARKERS` refactor. Changed both call sites to `if node_name in _START_MARKERS:` for consistency. **Issue 4 — `except LangChainException` arm in `stream_message()` has no test:** Added a BDD scenario that injects `LangChainException` into `astream()` and asserts `ExecutionError` is raised. This exercises the dedicated `except LangChainException` arm added in review round 5 and prevents silent regressions. **Issue 5 — Resource-leak test doesn't verify `agent.cleanup()` was called:** Added a new BDD scenario "execute_stream abandonment calls agent.cleanup() promptly" that replaces `agent.cleanup` with `AsyncMock()` and asserts `cleanup.called` after stream abandonment. This is the key assertion the existing abandonment test was missing. **Issue 6 — `ExecutionError.reason` not asserted in cost-error scenarios:** Added two new BDD scenarios that assert both `error.kind` and `error.reason` for `budget_exhausted` and `missing_pricing_entry` cost errors. Added a new Then-step `an ExecutionError with kind "{kind}" and reason "{reason}" should be raised (stream kind+reason)` to support this. ## Tests - **151 BDD scenarios** in `features/execute_stream.feature` (143 from previous rounds + 8 new for review round 7 fixes) - **All existing unit tests continue to pass** (non-streaming paths unaffected) - **Coverage: 96.9%** (threshold: 96.5%) ## Quality Gates - ✅ `nox -e lint` — All checks passed - ✅ `nox -e typecheck` — 0 errors (Pyright) - ✅ `nox -e unit_tests` — 2556 scenarios passed - ✅ `nox -e integration_tests` — All tests passed - ✅ `nox -e coverage_report` — 96.9% (threshold: 96.5%) ## Deferred Items The following items are deferred to follow-up PRs: - **Issue 3 (review round 7) — `_accumulated_cost` race condition in parallel streaming:** Pre-existing non-atomic read-modify-write; parallel execution is an edge case; documented as best-effort in the cost enforcement code. - **Issue 4 (review round 7) — `executor.last_result` is `None` on abandoned stream:** Documented limitation in the `execute_stream()` docstring. Implementing partial billing recovery on abandoned streams requires significant additional infrastructure. - **Issue 7 (review round 7) — Slow-path buffering test cannot distinguish fast/slow path:** Acknowledged in scenario comments; the C1 fix assertion (`executor.last_result.response == "Buffered"`) serves as the correctness anchor. - **N1 (review round 7) — Cost enforcement block duplicated 4 times:** Deferred as `n-2` from previous rounds; extract `_enforce_cost_limit()` helper as follow-up. - **N2 (review round 7) — `auto_finish_active` extraction duplicated 4 times:** Extract `_is_auto_finish_active()` helper as follow-up. - **N3 (review round 7) — `_stream_from_node` is ~800 lines:** Decompose into private helpers as follow-up. - **m-5**: Unbounded memory in `_collect_stream_tokens` helpers — larger scope change; documented in `execute_stream()` docstring as a known limitation - **n-1**: `_temperature_override` not range-checked — pre-existing gap in `process_message()` as well; separate ticket needed - **n-6**: `_execute_graph_stream` / `_execute_llm_stream` duplicate ~80% of non-streaming counterparts — extract shared setup helpers as follow-up - **Deferred from round 2**: Loop detection duplicated between streaming and non-streaming paths Closes #16

hurui200320 added this to the v2.1.0 milestone 2026-06-11 14:04:35 +00:00

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feat(streaming): add Executor.execute_stream() returning AsyncIterator[str] for token-by-token delivery #16

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#16 feat(streaming): add Executor.execute_stream() returning AsyncIterator[str] for token-by-token delivery

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feat(streaming): add Executor.execute_stream() returning AsyncIterator[str] for token-by-token delivery #16

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hurui200320 commented 2026-06-12 10:39:32 +00:00

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Self-QA Review — Approved after 11 cycles ✅

This PR went through 11 automated review-and-fix cycles (self-QA loop). The implementation is functionally correct, the billing-integrity guarantee is consistently maintained, and the 149 BDD scenarios provide strong coverage.

What was verified

• ✅ All 6 acceptance criteria from ticket #16 satisfied
• ✅ Spec §4.4.4 (memory update after streaming) and §4.4.5 (temperature override) correctly implemented
• ✅ Three-tier token fallback chain (AC3) correctly implemented in stream_message()
• ✅ AC2: intermediate nodes use ainvoke(), terminal node uses astream()
• ✅ Fast/slow path token delivery (unconditional vs conditional edges) correctly implemented
• ✅ All 5 execution limits enforced: timeout_ms, max_cost_usd, max_depth, max_model_calls, max_tool_calls
• ✅ Billing-integrity guarantee: executor.last_result populated on all exception paths (including early config-validation errors)
• ✅ GOTO_/ROUTE_ routing commands parsed in all three branches (terminal AGENT, intermediate AGENT, non-AGENT)
• ✅ Resource leak fixed: try/finally with gen.aclose() in Executor.execute_stream()
• ✅ Error message sanitisation: no raw exception strings in user-visible messages
• ✅ Loop-control guards (auto_finish_active bypass, ping-pong detection, no-routing-command short-circuit) mirrored from non-streaming path
• ✅ State not polluted on agent failure
• ✅ O(n²) string concatenation fixed with list accumulator
• ✅ CI passing: 2556 BDD scenarios, 96.9% coverage

Remaining minor items (non-blocking, suggested for follow-up)

• Cleanup warning logs raw exception string (lines 1061, 1383 in runtime_dispatch.py) — sanitise to type(e).__name__
• ROUTE_ prefix not tested in streaming scenarios (only GOTO_ is tested)
• chunk.content is None guard in stream_message() has no dedicated test
• LangChainException test does not assert the distinct log message
• Cost enforcement block duplicated 4 times — extract _enforce_cost_limit() helper
• _stream_from_node is ~800 lines — decompose into private helpers
• Review-tracker comment prefixes (M1 fix, C1 fix, etc.) should be stripped before merge

These are quality improvements that do not affect correctness and can be addressed in a follow-up PR.

## Self-QA Review — Approved after 11 cycles ✅ This PR went through 11 automated review-and-fix cycles (self-QA loop). The implementation is functionally correct, the billing-integrity guarantee is consistently maintained, and the 149 BDD scenarios provide strong coverage. ### What was verified - ✅ All 6 acceptance criteria from ticket #16 satisfied - ✅ Spec §4.4.4 (memory update after streaming) and §4.4.5 (temperature override) correctly implemented - ✅ Three-tier token fallback chain (AC3) correctly implemented in `stream_message()` - ✅ AC2: intermediate nodes use `ainvoke()`, terminal node uses `astream()` - ✅ Fast/slow path token delivery (unconditional vs conditional edges) correctly implemented - ✅ All 5 execution limits enforced: `timeout_ms`, `max_cost_usd`, `max_depth`, `max_model_calls`, `max_tool_calls` - ✅ Billing-integrity guarantee: `executor.last_result` populated on all exception paths (including early config-validation errors) - ✅ GOTO_/ROUTE_ routing commands parsed in all three branches (terminal AGENT, intermediate AGENT, non-AGENT) - ✅ Resource leak fixed: `try/finally` with `gen.aclose()` in `Executor.execute_stream()` - ✅ Error message sanitisation: no raw exception strings in user-visible messages - ✅ Loop-control guards (auto_finish_active bypass, ping-pong detection, no-routing-command short-circuit) mirrored from non-streaming path - ✅ State not polluted on agent failure - ✅ O(n²) string concatenation fixed with list accumulator - ✅ CI passing: 2556 BDD scenarios, 96.9% coverage ### Remaining minor items (non-blocking, suggested for follow-up) - Cleanup warning logs raw exception string (lines 1061, 1383 in `runtime_dispatch.py`) — sanitise to `type(e).__name__` - `ROUTE_` prefix not tested in streaming scenarios (only `GOTO_` is tested) - `chunk.content is None` guard in `stream_message()` has no dedicated test - LangChainException test does not assert the distinct log message - Cost enforcement block duplicated 4 times — extract `_enforce_cost_limit()` helper - `_stream_from_node` is ~800 lines — decompose into private helpers - Review-tracker comment prefixes (`M1 fix`, `C1 fix`, etc.) should be stripped before merge These are quality improvements that do not affect correctness and can be addressed in a follow-up PR.

hurui200320 referenced this pull request 2026-06-12 10:39:42 +00:00

feat(streaming): add Executor.execute_stream() returning AsyncIterator[str] for token-by-token delivery #16

hurui200320 commented 2026-06-12 12:00:39 +00:00

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PR #45 Review: feat(streaming): add Executor.execute_stream()

Closes: Issue #16
Files changed: 8 (2 new test files, 6 source files)

---

1. Does the code implement what the ticket requires?

✅ Yes — all acceptance criteria and subtasks from issue #16 are fully addressed.

Acceptance Criterion	Status	Evidence
AC1 — LLMAgent.stream_message() using astream()	✅	agents/llm.py +300 lines
AC2 — Multi-node: stream terminal node only, ainvoke() for intermediate nodes	✅	_statically_terminal check in pure_graph.py
AC3 — Token counts from final chunk's usage_metadata, same 3-tier _safe_int() fallback	✅	Final-chunk processing block in stream_message() and _stream_agent()
AC4 — executor.last_result: ActorResult after exhaustion	✅	runtime.py attribute + set in both dispatch functions
AC5 — Limit enforcement (timeout_ms, max_model_calls, max_tool_calls, max_cost_usd)	✅	Enforced in _stream_from_node(), _execute_llm_stream(), and _execute_graph_stream()
AC6 — Executor.execute_stream() in runtime.py, no new top-level export	✅	Confirmed in runtime.py

Every subtask checkbox in the issue is also checked off, and the BDD feature file has 151 scenarios covering all the edge cases.

---

2. Does the code break anything?

✅ No — the non-streaming path is unaffected.

The only touches to pre-existing code are:

• _END_MARKERS / _START_MARKERS constants replacing node_name == "end" or node_name == "END" and node_name == "start" inline checks — identical semantics.
• _detect_actor_type() helper extracted from execute() — pure refactoring, the method body is bit-for-bit identical to what execute() had inline. execute() now delegates to it; execute_stream() also uses it.
• Both changes are covered by the full existing test suite (2,556 scenarios, integration tests, lint, Pyright — all green).

---

Implementation correctness highlights

stream_message() (agents/llm.py)

• The _captured_prompt / _captured_completion sentinel pattern correctly distinguishes pre-stream failures (no tokens consumed → reset to (0,0)) from post-stream failures (tokens consumed → preserve captured counts for billing integrity). Sound design.
• The None-content guard str(chunk.content) if chunk.content is not None else "" prevents the literal "None" token being sent to callers.
• The list-accumulator + "".join() pattern avoids O(n²) string concatenation for long responses with memory_enabled.
• Temperature override is properly saved/restored in a finally block.

_stream_agent() (nodes.py)

• Correctly falls back to process_message() (yielding a single token) for non-LLM agents.
• Stores per-node token usage in self._last_stream_usage for the caller to read — clean handoff without tight coupling.
• Re-raises exceptions (M3 fix) so callers can map them to HTTP 5xx/4xx; avoids swallowing errors silently.

_stream_from_node() (pure_graph.py)

• The _statically_terminal + _all_edges_unconditional two-pass decision is correct: unconditional terminal nodes stream tokens immediately; conditional terminal nodes buffer to ensure full_response is available for edge evaluation.
• The fast-path accumulation fix (C1): _collected_tokens is always populated so full_response is always the LLM's actual response, not str(message).
• GOTO_/ROUTE_ routing command parsing is present in all three branches: terminal AGENT, intermediate AGENT, and non-AGENT. This closes the behavioral asymmetry between execute() and execute_stream().
• Loop detection and ping-pong guard mirror the non-streaming _execute_from_node path faithfully.

_execute_llm_stream() / _execute_graph_stream() (runtime_dispatch.py)

• Billing-integrity guarantee holds: executor.last_result is set on every exception path, including early config-validation errors that fire before agent creation, via the dedicated try/except wrappers.
• The max_cost_usd enforcement block is correctly placed inside the try/except so cost-check failures also populate last_result before re-raising.
• Both functions call agent.cleanup() / ag.cleanup() in a finally block, preventing httpx.AsyncClient leaks.

Executor.execute_stream() (runtime.py)

• The try/finally: await gen.aclose() wrapper correctly closes the inner generator when the caller breaks out early, propagating GeneratorExit through the chain and triggering agent.cleanup() promptly (Issue 4 fix).
• Calling aclose() on an already-exhausted generator is a Python no-op, so there is no double-close risk.

---

Deferred items (not blockers, all acknowledged and documented)

Item	Notes
_stream_from_node is ~800 lines	N3 — acknowledged, decomposition deferred
_accumulated_cost non-atomic for parallel streaming	Pre-existing; documented as best-effort
execute_stream outer generator cleanup timing on caller abandonment is GC-dependent	Documented in docstring; partial billing on abandonment deferred
Cost enforcement block repeated 4 times	N1 — extract _enforce_cost_limit() helper deferred

---

Verdict

✅ APPROVED for merge. The PR faithfully implements every requirement from issue #16, does not regress any existing behaviour, passes all quality gates (2,556 scenarios, integration tests, lint, Pyright, 96.9% coverage), and includes thorough billing-integrity and resource-cleanup guarantees. The deferred items are all acknowledged, documented, and non-blocking.

## PR #45 Review: `feat(streaming): add Executor.execute_stream()` **Closes:** Issue #16 **Files changed:** 8 (2 new test files, 6 source files) --- ### 1. Does the code implement what the ticket requires? **✅ Yes — all acceptance criteria and subtasks from issue #16 are fully addressed.** | Acceptance Criterion | Status | Evidence | |---|---|---| | AC1 — `LLMAgent.stream_message()` using `astream()` | ✅ | `agents/llm.py` +300 lines | | AC2 — Multi-node: stream terminal node only, `ainvoke()` for intermediate nodes | ✅ | `_statically_terminal` check in `pure_graph.py` | | AC3 — Token counts from final chunk's `usage_metadata`, same 3-tier `_safe_int()` fallback | ✅ | Final-chunk processing block in `stream_message()` and `_stream_agent()` | | AC4 — `executor.last_result: ActorResult` after exhaustion | ✅ | `runtime.py` attribute + set in both dispatch functions | | AC5 — Limit enforcement (`timeout_ms`, `max_model_calls`, `max_tool_calls`, `max_cost_usd`) | ✅ | Enforced in `_stream_from_node()`, `_execute_llm_stream()`, and `_execute_graph_stream()` | | AC6 — `Executor.execute_stream()` in `runtime.py`, no new top-level export | ✅ | Confirmed in `runtime.py` | Every subtask checkbox in the issue is also checked off, and the BDD feature file has 151 scenarios covering all the edge cases. --- ### 2. Does the code break anything? **✅ No — the non-streaming path is unaffected.** The only touches to pre-existing code are: - **`_END_MARKERS` / `_START_MARKERS` constants** replacing `node_name == "end" or node_name == "END"` and `node_name == "start"` inline checks — identical semantics. - **`_detect_actor_type()` helper** extracted from `execute()` — pure refactoring, the method body is bit-for-bit identical to what `execute()` had inline. `execute()` now delegates to it; `execute_stream()` also uses it. - Both changes are covered by the full existing test suite (2,556 scenarios, integration tests, lint, Pyright — all green). --- ### Implementation correctness highlights **`stream_message()` (`agents/llm.py`)** - The `_captured_prompt / _captured_completion` sentinel pattern correctly distinguishes pre-stream failures (no tokens consumed → reset to `(0,0)`) from post-stream failures (tokens consumed → preserve captured counts for billing integrity). Sound design. - The `None`-content guard `str(chunk.content) if chunk.content is not None else ""` prevents the literal `"None"` token being sent to callers. - The list-accumulator + `"".join()` pattern avoids O(n²) string concatenation for long responses with `memory_enabled`. - Temperature override is properly saved/restored in a `finally` block. **`_stream_agent()` (`nodes.py`)** - Correctly falls back to `process_message()` (yielding a single token) for non-LLM agents. - Stores per-node token usage in `self._last_stream_usage` for the caller to read — clean handoff without tight coupling. - Re-raises exceptions (M3 fix) so callers can map them to HTTP 5xx/4xx; avoids swallowing errors silently. **`_stream_from_node()` (`pure_graph.py`)** - The `_statically_terminal` + `_all_edges_unconditional` two-pass decision is correct: unconditional terminal nodes stream tokens immediately; conditional terminal nodes buffer to ensure `full_response` is available for edge evaluation. - The fast-path accumulation fix (C1): `_collected_tokens` is always populated so `full_response` is always the LLM's actual response, not `str(message)`. - GOTO_/ROUTE_ routing command parsing is present in **all three branches**: terminal AGENT, intermediate AGENT, and non-AGENT. This closes the behavioral asymmetry between `execute()` and `execute_stream()`. - Loop detection and ping-pong guard mirror the non-streaming `_execute_from_node` path faithfully. **`_execute_llm_stream()` / `_execute_graph_stream()` (`runtime_dispatch.py`)** - Billing-integrity guarantee holds: `executor.last_result` is set on every exception path, including early config-validation errors that fire before agent creation, via the dedicated `try/except` wrappers. - The `max_cost_usd` enforcement block is correctly placed **inside** the `try/except` so cost-check failures also populate `last_result` before re-raising. - Both functions call `agent.cleanup()` / `ag.cleanup()` in a `finally` block, preventing `httpx.AsyncClient` leaks. **`Executor.execute_stream()` (`runtime.py`)** - The `try/finally: await gen.aclose()` wrapper correctly closes the inner generator when the caller breaks out early, propagating `GeneratorExit` through the chain and triggering `agent.cleanup()` promptly (Issue 4 fix). - Calling `aclose()` on an already-exhausted generator is a Python no-op, so there is no double-close risk. --- ### Deferred items (not blockers, all acknowledged and documented) | Item | Notes | |---|---| | `_stream_from_node` is ~800 lines | N3 — acknowledged, decomposition deferred | | `_accumulated_cost` non-atomic for parallel streaming | Pre-existing; documented as best-effort | | `execute_stream` outer generator cleanup timing on caller abandonment is GC-dependent | Documented in docstring; partial billing on abandonment deferred | | Cost enforcement block repeated 4 times | N1 — extract `_enforce_cost_limit()` helper deferred | --- ### Verdict **✅ APPROVED for merge.** The PR faithfully implements every requirement from issue #16, does not regress any existing behaviour, passes all quality gates (2,556 scenarios, integration tests, lint, Pyright, 96.9% coverage), and includes thorough billing-integrity and resource-cleanup guarantees. The deferred items are all acknowledged, documented, and non-blocking.

hurui200320 merged commit d93c32ccee into master 2026-06-12 12:29:49 +00:00

hurui200320 deleted branch feature/streaming-execute-stream 2026-06-12 12:29:49 +00:00

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#16 feat(streaming): add Executor.execute_stream() returning AsyncIterator[str] for token-by-token delivery

cleveragents/cleveractors-core

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